BONDING IN

ORTHODONTICS

Presented By, Dr. Girish G. Sarada 1ST year P.G. Department Of Orthodontics & Dentofacial Orthopedics K.L.E. society`s Institute of dental sciences, Bangalore

EVOLUTION OF BONDING

For the orthodontic treatment to carry out, force is to be applied to the teeth, to

apply force we need some form of attachment over the teeth, so this can be done in two

ways

1. Banding

2. Bonding

BANDS - Bandless dentistry had been dream of orthodontists for many years. These

bands were introduced by W.E. Magill in 1871 & have been in existence for more than

100 years.

DISADVANTAGES OF BANDING

Laborious, time-consuming

Skilled work is required

Difficulty in banding partially erupted teeth

Decalcification /discoloration with loose or un-contoured bands

Gingival irritation

Unaesthetic

Need of separators

Closure of band spaces after completion of treatment

For the patient to whom esthetics being prime consideration even during treatment

,metallic look of fixed orthodontic appliance , has always been the bone of contention.

A survey of the developments in the field of orthodontics over last 50 years would

indicate that successful bonding of brackets to teeth, replacing conventional system of

cementing stainless steel bands with welded attachments is most significant achievement.

Since breakthrough of bandless dentistry in 1955, when buonocore described acid

technique to achieve to achieve micromechanical retention of resin to enamel, bonding

had come to stay.

•• HHIISSTTOORRYY––

3 major developments that made bonding of attachments to teeth possible

1. BUONOCORE 1955 – improved retention of methyl methacrylate to enamel – 85%

phosphoric acid for 30 seconds

2. BOWEN 1962 – bis Glycidyl methacrylate – more stable and greater strength

3. NEWMAN 1965 – first to acid etch and bond orthodontic brackets with epoxy

resin

ACID ETCHING -Michael Buonocore in 1955

• The first bonding agent for restorative dentistry, Sevriton Cavity Seal introduced

in 1949 by Oskar Hagger, a Swiss chemist working in London, using

glycerophosphoric acid dimethacrylate, an unfilled acrylic resin.

• In 1955, Buonocore, borrowing the techniques of industrial bonding, enhanced

the adhesion with the phosphoric acid etch.

Micahel Buonocore was first to demonstrate that bonding of acrylic material was

substantially increased by conditioning enamel surface with 85% phosphoric acid for 30

seconds. Monomer of acrylic wet etched surface, flowed into each pits aided by capillary

action & generated retentive resin tags. Mainly used to seal pits & fissures.

This procedure has expanded the use of resin bonded restorative materials as it provides

a strong bond between resin & enamel, forming basis for many innovative dental

procedures like resin bonded metal retainers, porcelain laminates & bonded orthodontic

brackets.

Newmann in 1965-

Was first to apply these findings & bonded plastic brackets with an epoxy resin after

etching with 40% phosphoric acid for 60 seconds.

Mitchell in 1967 -

Described a successful although limited, clinical trial using black copper cement & gold

copper attachment.

Smith in 1968-

Introduced zinc polycarboxylate cement & bracket bonding with this cement.

Miura et al in 1971-

Described an acrylic resin ORTHOMITE using a modified trialkyl borane catalyst, that

proved to be particularly successful for bonding plastic brackets & for enhanced adhesion

in presence of moisture.

In 1975, Silverstone Three patterns of enamel etching.

1979 Maijer R. and Smith D.C.

introduced an alternative to acid etching.The crystal growth on the enamel

surface.

Bonding materials strong enough for clinical use did not become routinely available until

mid 1970‘s before that experimental bonding system based on epoxy & acrylic resin had

been proposed & evaluated clinically with success. The greatest difficulty with epoxy

resin was slow development of full strength, so it was not possible to place arch wires at

same visit the bonded attachments were placed. The early resin materials suffered from

their different thermal coefficient of expansion relative to enamel extended to weaken

bonds.

The adhesives used introduced in early 1970‘s were primarily those of powder-liquid

type of methyl methacrylate that did not incorporate a filler. During this period, all

adhesives introduced had to adhere to plastic brackets that were made up of

polycarbonate. As time passed however the weakness of plastic brackets became apparent

& metal brackets begin to be used.

From mid 1970‘s the paste type of adhesives emerged in which both base materials &

catalyst were dispensed as pastes to be to be mixed before being used for bonding. The

reason for change from powder & liquid type to paste was mainly due to change in type

of brackets used in bonding.

It was in 1977, first detailed post-treatment evaluation of direct bonding over a full

period orthodontic treatment was published.

In survey by Gorlick in 1979 in U.S. it was seen that 93% of orthodontist preferred

bonding for bracket placement

First commercially available orthodontic adhesives

1. OIS Adhesive system – OIS company in 1969.

=> Masuhara introduced -- called direct bonding system for enamel. It was one of the

first dental adhesive commercially introduced after Buonocore proposed the concept of

acid-etching enamel.

2. Bracket Bond – GAC in 1970

3. Fujio Miura and associates in 1971 –

• Introduced – ORTHOMITE

• MMA - Tri–N–Butyl Borane (catalyst)

• Increased adhesive strength

• Coupling agent – ‗silane‘ methacryloxypropyltrimethoxysilane

• Increased adhesive penetration

• Chemically bonded to adhesive

Affinity to enamel

Methyl Methacrylate – 1st used adhesive

Catalyst - BPO (Benzoyl peroxide)

Difficulty in adhesion

• Polymerization shrinkage

Pulpal irritation

Merits of MMA adhesives:

1. Plastic brackets

2. Good storage stability

3. Increased working time – brush-on / dip-in

4. Elimination of sealant - good penetration into enamel surface

5. Less damage during debonding

Demerits of MMA adhesives:

1. Fluctuating proportion of powder-liquid depending on operator

2. Poor mechanical interlocking to metal bracket bases

BOWEN 1962 :

Bisphenol Glycidyl Dimethacrylate (Bis-GMA)

• Greater strength

• Lower water absorption

• Less polymerization shrinkage

• 2-paste system

• Strongest adhesives for metal brackets

MERIT AND DEMERIT OF BIS-GMA

• Poor penetration due to increased viscosity – dilution reqd.

• Plastic brackets could not be used – primer for partially dissolving added

• Active life less than powder liquid system

In 1974 – ORTHOMITE II

20% more HNPM –

hydroxy napthoxy propyl methacrylate

• Eliminated silane

ORTHOMITE SUPER BOND

4 - META – methacryloxyethyl trimellitate anhydride

4 - META • Bonds to Plastic & metal

• PRE-PRIMED brackets

• Base was primed with adhesive

• Bracket base covered with PMMA powder

• Base dipped in monomer and pressed onto etched surface.

• Bond strength less than manual application

Nanotechnology

has led to the development of a new composite resin characterised by containing

nanoparticles measuring approximately 25 nm and nanoaggregates of

approximately 75 nm, which are made up of zirconium/silica or nanosilica

particles.

Advantages of bonding-

1. Esthetically superior.

2. Faster & simpler.

3. There is less discomfort for patient

4. Arch length not increased by band material

5. Allows more precise bracket placement

6. Improved gingival condition is possible & there is better access for cleaning.

7. Partially erupted or fractured teeth can be controlled.

8. Mesiodistal enamel reduction is possible during treatment.

9. Interproximal areas are accessible for composite buildup.

10. Caries under loose bands is eliminated. Interproximal caries can be detected &

treated.

11. No band spaces to close at end of treatment.

12. No large supply of bands needed.

13. Brackets may be recycled further reducing the cost.

14. Lingual brackets ‗Invisible Braces‘ may be used when esthetics important.

15. Improved appearance, deceased discomfort for patient & ease of application for

clinician.

Most important –

Improved appearance

Hygiene

Ease of application

Decreased discomfort for the patient

Disadvantages- 1. A bonded bracket has weaker attachment than a cemented band.

2. Few bracket adhesives are not strong.

3. Better access for cleaning does not necessarily guarantee better oral hygiene &

improved gingival condition, specially if excess adhesive extends beyond bracket base.

4. Protection against interproximal caries of well contoured cemented band is absent.

5. Bonding in not indicated on teeth where lingual auxillaries are required or where

headgear are attached.

6. Rebonding a loose bracket requires more preparation than rebanding a loose band.

7. Debonding is more consuming than debanding since removal of adhesive is more time

consuming.

••

TERMINOLOGY

Bonding -

Process of joining 2 materials by means of an adhesive agent that solidifies during

bonding process.

•• TTyyppeess-- 1. Physical bonding-

Involves Vander wall / electrostatic interactions that are

relatively weak. It is the type of bonding seen when

surfaces smooth & chemically dissimilar.

2. Chemical bonding -

Involves bonds between atoms are formed across

the interface from adhesive & adherand. Since materials are

dissimilar,the extent to which bonding is possible is

limited, overall contribution to bond strength low.

Mechanical bonding –

Result of an interface that involves undercuts & other irregularities that produce

interlocking of the material.

Almost every case of dental adhesion is based primarily on mechanical bonding.

ADHESION-

A molecular attraction between 2 contacting surfaces promoted by interfacial force of

attraction between molecules or atoms of two different species.

Can be chemical, mechanical or combination.

ADHESIVE- Substance that promotes adhesion of one substance or material to another

Requirements-

1. Resist ambient temperature

2. Fluid enough to penetrate tooth surface but viscous enough to enable good bracket

positioning.

3. Set hard and tough

4. Tolerate/dissolve impurities

5. Not cure slowly, unduly shrink or allow discontinuities

6. Must wet tooth surface & flow into surface pores & valleys.

7.Contact angle – It is angle formed between interface of adhesive & adherent. It should

be zero for proper wetting of surface.

8. No change on solidification

9. Water absorbing tendency - minimal

SUBSTRATE / INTERFACE

1. It should be Clean & Firm

2. Allow air to escape as air if present acts as-

- Polymerisation inhibitor

- Decreases cohesion

Nature of Enamel –

Unique characters are -

1. Hardest

2. Only clinically visible mineralized tissue

3. No regenerative capacity

•• Morphologically – It has enamel prisms which results in Keyhole/ Fishlike appearance.

Enamel rod has 2 parts- Head & tail

Each prism contains hydroxyapatite crystals which are parallel to long axis in head region

& perpendicular in tail region

Crystal dissolves faster – Head region

Factors affecting Enamel solubility-

Pre-eruptive-Hypoplasia/hypocaicification- infection of primary teeth

Excessive ingestion of fluoride

Post-eruptive- Topical fluorides

Plaque/pellicle

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Classification of Bonding Materials-

A) Based on basic bonding Materials-

1- Acrylic based- Self curing acrylic

2- Diacrylate based- Bis GMA/

Bowen‘s resin

3- Glass ionomer

Basic difference between is acrylics are linear polymers where as diacrylates are cross

linked 3-D polymers.

•• B) Based on curing system-

1. Self curing

2. Light curing

3. Dual curing

4. Thermocured

C) Based on Fluoride system-

1. Fluoride releasing

2. Non-fluoride releasing

Adhesives acting in the presence of water

1. MOISTURE-RESISTANT

- can bond in presence of water

- saliva, gingival fluid – contaminants

- ex. Transbond MIP

2. MOISTURE-ACTIVE

- need water for bonding

- enamel surface intentionally made wet

- Cyanoacrylate – no liquid, only paste

- ex. Smartbond

Unfilled Acrylic Resins-

Widely used as adhesives in beginning but its use is limited due to its few properties.

Available in powder & liquid form.

Composition-

Powder - polymethyl methacrylate

Initiator- Benzoyl Peroxide approximately 0.3 to 0.5%.

Monomer- Methyl methacrylate

Cross linking agent - Ethylene dimethacrylate

Inhibitor- Methyl hydroquinone 0.006%

Orthimite, Directon, Bondeze, Geine etc. are based on self curing acrylics

Properties-

Unfilled

Compressive strength- 70MPa

Tensile strength –24MPa

Elastic modulus-2.4GPa

Thermal coefficient of expansion- 92.8ppm/ºC

KHN- 15

Water sorption- 1.7

Curing shrinkage-2-3vol%

Disadvantages-

Low hardness & strength

Inferior resistance to abrasion

High coefficient of thermal expansion

- microleakage

Composites-

Composite is a solid formed from two or more distinct phases that have been combined to

produce properties superior to or intermediate to those of individual components.

Dental Composite - It is a highly cross linked polymeric material reinforced by dispersion

of amorphous silica, glass, crystalline or organic resin filler particles &/ short fibers

bonded to matrix by a coupling agent.

•• There are 3 structural components-

Matrix – Plastic resin that forms continuous phase & binds filler particles.

Filler

Coupling agent

MATRIX – It is made up any of the following

BisGMA

Urethane dimethacrylate

Triethylene Glycol Dimethacrylate (TEGMA)

High molecular weight that reduces polymerization shrinkage but increases viscosity.

Viscosity Controller-

Methyl methacrylate (MMP)

Ethylene glycol Dimethacrylate (EDMA)

Triethylene Dimethacrylate (TEGDMA)

Diethylene glycol Dimethacrylate (DEGMA)

•• Inhibitors-

Butylated Hydroxytolune (BHT) - 0.01wt%

Functions -

1. For adequate storage life

2. Ensures sufficient working time

Chemical Activation-

Initiators - Benzoyl peroxide

Accelerators - Tertiary aromatic amines

Eg- N,N-Dimethyl-p-toluidine

N,N dihydroxy ethyl-p-toludine

Two pastes are mixed- amine reacts with BP forming free radicles & polymerization

is initiated.

Photochemical Activators

Initiator - UV light of 365nm

Activator - benzion ethyl ether

Initiator - Visible light of 420-450nm.

Activator - Diaketone such as camphoroquinone - 0.2wt%

Advantages of Visible light over UV light-

- Greater depth of cure

- Controlled working time

Optical Modifiers-

Titanium oxide & aluminum oxide - 0.001-0.007wt%

Visual shading & translucency

DISPERSED PHASE/ REINFORCING PHASE

Quartz, fluorosilicates, glasses & glass ceramics.

The glass or glass ceramic may be lithium aluminum, barium aluminum or strontium

aluminum silicates.

Purpose-

1. Reinforcement of matrix resin - increased hardness, strength, decreased wear.

2. Reduction of polymerization shrinkage.

3. Reduction in thermal expansion & contraction.

4. Improved workability by increasing viscosity.

5. Reduction in water sorption, softening & staining.

6. Increased radiopacity & diagnostic sensitivity through incorporation of strontium &

barium glass & other heavy metals.

••

Concise, Solo-Tach, Nuva-Tach -3 to 20 µm impart abrasion resistance properties.

Endur, Dynabond - 0.2 to 0.3µm smoother surface that retains less plaque & is prone

to abrasion.

COUPLING AGENT

Filler particles bonded to resin matrix

Titanates & Zirconates

Organosilanes like γ-emethacryloxypropyl-trimethoxy-silane

Improves physical & mechanical properties

Inhibits leaching by preventing water from penetrating along resin-filler interface

•• BBoonnddiinngg aaggeennttss-- PPhhyyssiiccaall pprrooppeerrttiieess

Classification – based on particle size

1. Traditional/macrofilled

Filler size – 1-50µm

Average- 8-12µm

Filler loading 70-80wt%

Compressive strength- 250-300MPa

Tensile strength – 50-65MPa

Elastic modulus- 8-15GPa

Thermal coefficient of expansion- 25-35ppm/ºC

KHN- 55

•• 2. Hybrid (small particle) –

Filler size – 0.5-3µm

Filler loading – 80-90wt%

Compressive strength- 350-400MPa

Tensile strength – 75-90MPa

Elastic modulus-15-20GPa

Thermal coefficient of expansion- 19-26ppm/ºC

KHN- 50-60

Curing shrinkage-2-3vol%

•• 3. Hybrid (all purpose)

Filler size – 0.4-1µm

Filler loading – 75-80wt%

Compressive strength- 300-350MPa

Tensile strength – 40-50MPa

Elastic modulus-11-15GPa

Thermal coefficient of expansion- 30-40ppm/ºC

KHN- 50-60

Curing shrinkage-2-3vol%

•• 4. Microfilled-

Filler size – 0.04-4µm

Filler loading – 35-67wt%

Compressive strength- 250-350MPa

Tensile strength – 30-50MPa

Elastic modulus-3-6GPa

Thermal coefficient of expansion- 50-60ppm/ºC

KHN- 25-35

Curing shrinkage-2-3vol%

••

Flowable composites –

Modification of small particle filled & hybrid composites. They have reduced filler level

so as to provide a consistency that enables the material to flow readily, spread uniformly,

intimately adapt to tooth surface.

Properties-

Filler size – 0.6-1µm

Filler loading – 40-60wt%

Elastic modulus-4-8GPa

Curing shrinkage-3-5vol%

Packable composites-

Filler size –fibrous

Filler loading – 65-81wt%

Elastic modulus-3-13GPa

Curing shrinkage-2-3vol%

••

Chemistry

Basic

• Dental resins solidify when they polymerize.

• Polymerization occurs through a series of chemical reactions by which the

macromolecule, or the polymer, is formed from large number of molecules known

as monomers.

Monomers may be joined by either:

1. Addition polymerization

2. Step- growth or condensation polymerization

Addition polymerization

• Most dental resins are polymerized by this mechanism in which monomers add

sequentially to the end of a growing chain

• Compared with condensation polymerization, add polymerization can produce

giant molecules of almost unlimited size.

• Also there is no change in composition i.e. the structure of monomer is repeated

many times in polymer

• Requirement :-

An unsaturated group (having double bond)

e.g. Ethylene C2H4

A free radical I*

When the free radical & its unpaired electron approach a monomer with its high

electron density double bond, an electron is extracted, & it pairs with the electron

to form a bond between the radical & the monomer molecule , leaving the other

electron of the double bond unpaired

- Thus the original free radical bonds to one side of the monomer molecule & forms

a new free radical site at the other end.

- The reaction is now initiated.

STAGES IN ADDITION POLYMERIZATION

1. Induction

2. Propagation

3. Chain transfer

4. Termination

Induction Activation of monomer molecules

Free Radicals

In light activated system Camphoroquinone & Dimethyleaminoethylemethacrylate will

generate free radicals.

Visible light => 470 nm wavelength

Propogation - The resulting free radical- monomer complex then acts as a new free radical

center when it approaches another monomer to form a dimer, which also becomes

a free radical.

- This in turn, can add successively to a large no. of molecules so that the

polymerization process continues through the propagation of the reactive center.

TERMINATION

1. Direct coupling

Ii Mm*+ IiMn* => Ii Mm MnIi

It become deactivated by an exchange of energy.

2. Exchange of hydrogen atom

The hydrogen atom is transferred from one growing chain to another.

The double bond is created in this transfer

STEP GROWTH POLYMERIZATION

• The polymerization is accompanied by repeated elimination of small molecules

(byproducts)

• Functional groups are repeated in the polymer chain.

Slow process, reaction follows step wise pattern i.e. monomer – dimer – trimer- so for

Glass ionomer cement

Glass Ionomer is generic name of group of materials based on reaction of silicate glass

powder & polyacrylic acid. This acquires its name from its formulation of glass powder

& an ionomer that contains carboxylic acids

GIC were introduced in 1972 primarily as luting agent & direct restorative properties

with unique properties for bonding chemically to enamel dentin being able to release

fluoride ions for caries protection.

It is used routinely for cementing bands because they are stronger than zinc phosphate &

zinc polycarboxylate cement with less demineralization at the end of treatment.

••

Composition- Powder-

It is an acid soluble calcium fluroaluminosilicate

Silica, aluminum oxide , aluminum fluoride, calcium fluoride, sodium fluoride &

aluminum phosphate

Lanthanum, strontium, barium, or zinc oxide – provides radiopacity.

Raw materials are fused at 1100 -1500ºC to a uniform glass.

Liquid-

Polyacrylic acid- 40-50%

Itaconic / Maleic acid - Increase reactivity & reduce viscosity

Tartaric acid - improves handling characterstics & increases working time

Rexn- Acid base

Glass + Polyelectrolyte = Polysalt hydrogel

+ silica gel

Porperties-

ST – 7 min

Film thickness – 24

Compressive strength- 86

Tensile strength –6.2MPa

Elastic modulus -7.3GPa

Solubility in water- 1.25wt%

Advantages -

1. Ease of debonding

2. Controllable working time

3. No iatrogenic enamel damage

4. Fluoride release

5. Resistance to acid erosion

6. Adhesion to enamel & metallic bases

Limitations-

Short working time

Initial sensitivity to moisture & dehydration

Slow development of strength & elastic modulus

Low fracture toughness

Low abrasion resistance

Need for GIC for bonding

• The use of composites for bracket attachment has a number of disadvantages.

• Enamel may be lost during prophylaxis, acid etching and at the time of clean up

of residual resin at debond, as well as during rebonding procedures (Thompson

and Way, 1981; Silverston, 1974; Pus and Way, 1980).

• The concentration of fluoride is greatest at the enamel surface (Thompson and

Way, 1981) and the loss of this surface material is therefore of concern.

Larry White in 1986 described method of bonding orthodontic brackets with GIC. The

earlier chemically cured GIC typically took 24 hours to reach optimal bond strength

therefore arch wires had to be deterred or else very light force generating arch wires

could be only placed.

Silverman et al introduced in 1995 a light curing GIC for orthodontic bonding Fuji

ortho LC. They have recommended a no etch technique for bonding & claims it to bond

satisfactory in presence of moisture. They reported failure rate of approx 3% comparable

to that of bonding resins which indicate its clinical satisfactory.

Advantages

Faster setting

Show higher initial & sustained shear bond strength

Types

1. Modified composite - Compomer or polyacid modified composite resin

2. True resin modified / Hybrid ionomer

Compomer-

Essentially resin matrix composite. It consists of silicate glass particles, sodium fluoride

& polyacid modified monomer without any water. Because of absence of water cement

mixture is not self adhesive.

- Filler replaced by ion leachable aluminosilicate

- No acid base reaction during setting

- Light activated free radicals polymerization of methacrylate groups.

True Resin modified-

Replacing part of polyacrylic acid with hydrophilic monomer.

It incorporates acid base reaction.

Composition-

Powder-

Ion- leachable fluoroaluminosilicate glass particles

Initiators for light & / chemical curing.

Liquid-

Water

Polyacrylic acid or Polyacrylic acid modified with methacrylate & hydroxyethyl

methacrylate (HEMA) monomers.

Advantages

-Better early strength compared to conventional GIC.

-Reduce moisture sensitivity

-Improvement of translucency

-Higher bond strength compared to conventional GIC.

But polymerization shrinkage on setting can increase microleakage.

Compressive strength- 105

Tensile strength –20

KHN-40

Increased early strength

Less moisture sensitivity

Literature

Bond strength and durability of glass ionomer cements used as bonding agents - AJO

July 1989

-Klockowski, Davis, Joynt, Wieczkowski, and MacDo

• Compared GICs (Ketac-fil, Ketac-cem and Chelon) with Rely-A-Bond (no-mix

autopolymerising) which served as a standard in a clinical study.

Results:

• Bond strength of GICs was significantly less when compared to Rely-A-bond.

• Less reduction of bond strength of GICs on recycling – lesser than Rely-A-bond

on recycling

• Failures involved cohesion within cement or adhesion involving the enamel -

easily scraped off from the enamel surface without causing much damage.

• Cook -1990 compared the in vivo bond strength of a glass ionomer cement,

Ketac (ESPE Premier Denbol Products, Norristown, Pa.), with a composite resin

bonding agent – 12% failure rate

• Fajen et al- 1990 evaluated the bond strength of three glass ionomer cements

against a composite resin in vitro

• Fricker - 1994, worked with Fuji II LC glass ionomer cement (GC Corp., Kyoto,

Japan)

• Same rate of success bonding brackets to enamel surfaces as he did with

composite cements.

• Dentine conditioner was utilized for ten seconds

A new light-cured glass ionomer cement that bonds brackets to teeth without etching in

the presence of saliva - AJO-DO SEP 1995

- Silverman, Cohen

• Used a new Resin modified GIC

• Fuji Ortho LC

• Light-cured, resin-reinforced glass ionomer cement

3 mechanisms of setting

Advantages:

• Saves significant amount of chair time.

• Eliminates working in a dry field.

• Eliminates etching and priming enamel surfaces.

• Fluoride release protects teeth against decalcification.

• Repairs are quick and easy.

• Increased patient and operator comfort.

EJO 2004 April according to S.B. Oliveria et al

• There is no significant bond strength difference occurred when compared to

composite resin when used with light and medium arched wires. So RMGIC is a

viable alternative when used with light & medium arch wires.

Aug 2004 AJO-DO by Andrew Summers et al

• bond strength, highest is achieved by conventional chemically cured composite

followed by RMGIC & least by GIC

BONDING PROCEDURE

DIRECT BONDING-

1. CLEANING-

Thorough cleaning of teeth with pumice is essential to remove plaque & the organic

pellicle that normally covers all teeth. Cleaning is done using rotary instruments either a

rubber cup or polishing brush. A bristle brush cleans effectively after cleaning rinse.

Reisner et al found more consistent results when Buccal tooth surfaces were abraded

lightly with a tungsten carbide bur(#1172) at slow speed (25,000rpm) than pumiced for

10 secs before acid etching.

2. ENAMEL CONDITIONING-

a. Moisture Control-

After the rinse, salivary control & maintenance of a completely dry working field is

absolutely essential.

Some measures are-

1. Lip Expander- For simultaneous premolar to premolar bonding in both arches.

2. Dri-Angles to restrict flow of saliva from parotid duct.

3. Combined saliva ejector- tongue holder to remove moisture from mouth.

4. While bonding mandibular second molar use of double hygoformic saliva ejector & T

tube is indicated.

5. Antisialogogues are generally not recommended. Different preparations used are

Methantheline bromide (Banthine), Propanthaline bromide(Probanthine ), atropine

sulfate.

Excellent & rapid saliva flow restriction is obtained by Propanthaline bromide injections.

Whenever indicated Banthine tablets 50mg per 100 lb(45kg) in sugar free drink 15 min

indicated.

6. Cheek retractors

7. Gadgets that combine several of these.

8.Cotton or gauze rolls.

Various means for moisture control-

••

••

Dri angle Salivary duct obstructor

••

ANTISIALOGOGUES –

They help to decrease salivary release from glands & ducts unlike other devices that

control released saliva.

• Atropine sulphate - In JCO-1981 Sidney brant Showed this is a safe drug with

few complication & can be used as an sublingual injection

(Dose-0.4 mg)

• Banthine tablets –In JCO 1981 Richard .N. Carter reported that 50 mg per 100 lb

in a sugar free drink 15 min before bonding is adequate.

b.Enamel Pretreatment-

• Acid etching

• Other alternatives to acid etching

1. Crystal growth

2. Sand blasting/air abrasion

3. Laser etching

Acid Etching-

Process of roughning a solid surface by exposing it to an acid & thoroughly rinsing

the residue to promote micromechanical bonding of an adhesive to the surface.

The conditioning solution or gel usually 30% to 50% phosphoric acid typically

37% is preferred

Calcium monophosphate & ca. sulfate byproducts – removed by water rinse

Concentration greater than 50% - Deposition of adherent layer of monocalcium

phosphate monohydrate on etched surface which inhibits further dissolution

Concentration less than 27% creates dicalcium phosphate monohydrate precipitate that

cannot be easily removed & may interfere with adhesion

Apply over enamel surface - foam pellet, brush for approximately 15-30 seconds.

Saliva ejector, tongue

holder, bite block HHiigghh ssppeeeedd evacuator

To avoid damaging delicate enamel rods care should be taken not to rub liquid onto

tooth.

Etchant is washed with abundant water spray.

High evacuator - increased efficiency in collecting etchant water rinse & reduce

moisture contamination.

Thoroughly wash with moisture & oil free surface to obtain dull, frosty appearance.

Etched enamel - higher total surface energy which ensures that a resin will readily

wet surface & penetrate into resulting microporosity.

Once resin penetrates into porosity it can be polymerized to form resin tags that

produce mechanical bond to enamel.

If contamination occurs re-etch again.

Cervical enamel due to its different morphology usually looks different from central

& incisal portion of tooth.

Etching entire facial surface is harmless but logically etch an area only slightly larger

than pad

Acid in gel or solution

Gel provides better control.

Gels are prepared by adding colloidal silica or polymer beads to acid.

Fluoridated phosphoric acid solutions and gel provides same morphological etching

pattern. & have adequate strength.

Mostly used gel -Ultra Etch 37% phosphoric acid blue gel

Advantages-

1. Adequate contrast

2. Smooth consistency

3. Ideal viscosity

4. Provides even nicely demarcated white frosted appearance

Alternative acids for etching

traditionally :- 30 – 40 % Phosphoric acid

- 10 % Phosphoric acid

- 10 % Maleic acid

- 2.5 % Nitric acid

Type and concentration of Acid

A. Liquid

B. Gel

Bond Strength

37% phosphoric acid – highest bond strength – 28 MPa

10% maleic acid – 18 MPa

Wang and colleagues ( Angle 1994) evaluated several phosphoric acid concentrations

from 2% to 80% and found that best bond strength was achieved with 30%-40%

concentrations

Rationale of etching

Gwinnett, Matsui & Buonocore

Primary mechanism of attachment of resin

Resin tags to etched surface

MICROMECHANICAL BOND

Acid etch removes 10 microns of enamel

Creates porous surface

Increases wettability

Timing-

Young permanent teeth -15-30 secs.

Deciduous teeth- Sandblast with 50 µm Aluminum oxide for 30 secs to remove

outermost aprismatic enamel & etch for 30 secs with 35% phosphoric acid gel.

Adult- 60 secs

Premolars,canine, anteriors- 15 secs

First molar- 30 secs

10- 30 secs – No effect on bond strength

Less than 5 secs- Decreased bond strength

Scanning electron microscopy- 30 secs produces optimal etching than 15 secs

••

Normal thickness of enamel is 1000- 2000µm

Etching removes 3-10µm of surface enamel

Histological alteration of 25 µm

Deeper – 100 µm

Care taken while etching acquired & developmental demineralization.

- Short etching time

- Apply sealer / primer

- Use bonding agents with extra care not to have any adhesive deficiency

Study of Etched Enamel Under Scanning Electron Microscope-

Bonding should have sufficient strength to resists application of orthodontic force to

move teeth, at the same time should facilitate easy & a traumatic debonding attachments

& minimum clean up procedure of enamel subsequent to removal of appliances.

Various studies have been carried out to define optimal concentration of acid used for

etching with phosphoric acid. These investigations include study of etched enamel

surface pattern under scanning electron microscope highlighting the loss of enamel , test

of shear bond strength of a bonded attachment to a correlated etchant concentration &

duration of etching & trauma to enamel & amount of adhesive on surface of enamel

subsequent to debonding.

Diedrich typed action of etchant on enamel in 3 stages-

The above mentioned etched patterns of etched enamel surface given by Silverstone et al.

Patterns of etching Gwinnett & Silverstone

Type I- Core etching

A. Honeycomb pattern – ( Initially periphery of prism head is delineated

by micro- clefts (0.1-0.2Mm) continued action of acid leads to loss of

substance predominantly in area of prism cores with simultaneous

conservation of marginal areas

Least amount of enamel is lost in this etch pattern.

Type II – Periphery etching

Peripheral etching pattern is an advanced stage in which fragile prism

peripheries break off.. Max enamel loss takes place in this stage

Type III – Mixed pattern

As action of acid proceeds there is dissolution of crest like marginal

ridges, while marginal clefts continue to widen. This transitional zone of

central & peripheral etching pattern in which existing marginal ridges are

elevated to 3µm

Galil & Wright desribed Type IV & V

Type IV- Etch pattern commonly seen in cervical areas. It shows irregular pattern &

displays no rod or prism pattern.

Type V – Shows no prism outline. Enamel surface is extremely flat & smooth & they

lack micro-irregularities for resin penetration.

Iatrogenic effects of acid etching-

Fracture & cracking of enamel on bonding

Increased surface porosity- staining

Loss of acquired fluoride in outer 10 µm of enamel surface

Resin tags retained- discoloration

Rougher surface if overetched

Bond strength with various etching times

WEI NAN WANG ET AL AJO 1991

• Compared the tensile bond strength at various etching times 15, 30, 60, 90, 120

secs

• 37 % phosphoric acid

• TBS was not statistically different for 15,30,60,90

• TBS decreased – 120 secs

• Debonding – fewer enamel fragments with shorter etching times

ALASTAIR GARDNER , ROSS HOBSON AJO 2001

• Compared quality and quantity of enamel etch produced by 37 % phosphoric acid

and 2.5% nitric acid for 15 , 30 ,& 60 secs

Concluded

• 37 % phosphoric acid - better etch for all 3 applications

• 15 < 30 & 60

• 30 = 60

• Supported use of 37% - 30 secs to get optimum bond strength

The continuous brush acid technique

BAHARAV , LANGSAM J PROSTH DENT 1987

• Aim was to determine whether mechanical agitation of etchant would enhance

decalcification of enamel

• Non carious pre molars

1. Mesial half – 35% P04 acid[30 secs] left undisturbed

2. Distal half – 35% po4 acid [30 secs] continuously painted

• Results

• Continuous brushing of etchant - more efficient dissolution of enamel

• Reduction of size of remaining crystals

• Hence increasing the potential space between them for retention

Alternatives to acid etching

• CRYSTAL GROWTH

• SAND BLASTING/ AIR ABRASION

• LASER ETCHING

Crystal growth

SMITH

Polyacrylic acid – chemical bonding

Purified polyacrylic acid- slight etching

Polyacrylic acid + sulfate ion – crystalline deposit

CALCIUM SULPHATE DIHYDRATE

Depends on concentration of sulfate ions

MAIJER AND SMITH AJO 1982

Crystalline interface produced tensile bond strength equivalent to conventional

acid etched surface

Debonding => fracture at crystal - resin interface

Other soln – sulphuric acid anion[more reliable and uniform growth

Procedure

• One drop of viscous liquid placed on tooth surface

• Left undisturbed for 30 secs

• Brush / swab should not be agitated as in etching as it may affect crystal/enamel

interface

• Rinsed for 20 secs

• Forceful water spray to be avoided as it will break crystals

• Look out for a dull whitish deposit

• Bracket bonded in usual way

• These crystals grow in so called spherulitic habit

MECHANISM OF RETENTION

• Calcium sulfate crystals must enucleate from bound calcium

• To achieve this some etching is required

• Enamel solubility ~ crystal enucleation

• Mechanical attachment is created around the crystalline interface and

superficially etched enamel

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eennaammeell ssuurrffaaccee eennaammeell ssuurrffaaccee

ARTUN AND BERGLAND

• Sulphuric acid - crystals not as long and needle like as with polyacrylic acid but

were rounder and flatter

Hence debonding was easier

Advantages of crystal growth • Debonding easier and quicker

• Little damage to enamel

• Minimal effect on outer fluoride containing enamel

• No resin tags left behind

• Possibility of incorporating fluoride in crystal interface – anticariogenic action

Crystal growth

JOHN ARTUN , S. BERGLAND AJO 1984 • Sol

n A – dil. sulphuric acid + sodium

sulphate

• Soln B – 10% po4 acid +dil. sulphuric acid

• Failure rates recorded – 6 months

• A > B > ACID ETCH

Sand blasting / air abrasion

Also referred as Micro etching in which particles of aluminum oxide are propelled

against suefrace of enamel by high air pressure causing abrasion of surface.

Resultant bond strength is 50% of those to conventional acid etching.

Its a older technique of enamel pretreatment introduced as early as 1940 by Dr. Robert

Black.

It uses abrading with 50 µm or 90 µm particles of aluminium oxide for 3 sec at 10 mm

distance.

Used for cavity preparation

Preparation of enamel /dentin

• Factors affecting bond strength

1. Particle size

2. Air pressure

3. Exposure time

4. Microstructure of enamel surface

37% H3PO4 acid 90 um AlO2 air abrasion

WENDALA VAN WAVERAN, ALBERT FEILZER AJO 2000

Compared bond strength and enamel loss between sand blasting and conventional

acid etching at varying exposure times and air pressure

Bond strength

Sand blasting < acid etching

Enamel loss

Sand blasting < acid etching

AJO-DO 1997 Marc .E. Olsen et al

reported that air abrasion significantly decreases bond strength & on debonding

leaves no adhesive on enamel surface.

• So it is not recommended.

Laser etching LASER

• Light Amplification By Stimulated Emission Of Radiation

3 elements

• Lasing medium [ solid/liquid/gas]

• Energy source[xenon flash lamp/electrical discharge]

• Optical resonator

1. Coherence

2. Collimation

3. Monochromaticity

When laser strikes an object it may be

• Reflected

• Transmitted

• Scattered

• Absorbed

• Combination of above

This new concept was proposed in 1993, by J.A.Von Fraunhofer.

• At 3 watts for 12 sec laser etching = acceptable bond strength though

significantly less than conventional acid etching.

• He used Nd/ YAG as laser source.

• Serder Usumuz et al in AJO-DO 2002 used ErCr ; YSGG as the hydrokinetic

laser system for acid etching & came to the same conclusion.

Classification • Mode of excitation ( Continuous or Pulsed)

• Wavelength

1. UV range(Krypton Flouride, Argon Flouride)

2. Visible Light ( Helium , Neon )

3. Infra Red range ( carbon dioxide, Nd:Yag)

Application of laser causes localized melting & ablation.

Removal of enamel primarily occurs by micro-expulsion of entrapped water in the

enamel.

There may be melting of hydroxyapatite crystals

Laser etching with Nd : Yag M.A WILSON ET AL

• Studied the surface effects of dentin following

laser etching with Nd:Yag and evaluated the

shear bond strength of composite between

treated and untreated laser etched dentin

• Surface roughness

laser etched > unlased dentin

• Bond strength

Laser treated >unlased dentin

LYDON COOPER ET AL

• Shear bond strength of composite to laser pre treated dentin increased by 300 %

localized melting + recrystallization

Fungiform projections

• The composite adapted to undercuts & space between the dentin projections

SEM picture of enamel after 37% SEM picture of enamel

after phosphoric acid etching laser etching of 2 W output

Pulsed krypton fluoride excimer laser Dr Francis M

Compared surface morphology, bond strength, and ARI between acid etching and

3 different energy densities of pulsed krypton fluoride laser

440, 460, 480 MJ/cm2

Concluded :

TBS 460> 480 >A E >440

SBS 480 > A E > 460 > 440

SEM regular etch pattern similar to acid etch seen with 460 & 480 MJ/cm2

Törün Özer et al (AJODO Aug 2008)

• compared shear bond strengths, enamel surface characteristics, and adhesive

remnant index (ARI) scores of bonding with laser irradiation, phosphoric-acid

etching, and SEP systems.

Results

• Irradiation with the 0.75-W laser produced lower shear bond strengths than the

other methods

• No difference for enamel characteristics

• ARI scores no diff. except for 0.75 W laser group.

• 0.75 W group => not suitable

LASER ETCHING UNIT

3. SEALING

After teeth are completely dried & appear frosty white, a thin layer of sealant is

applied over entire etched enamel surface with a small foam pellet or brush with a single

gingivoincisal stroke.

Sealer is a hydrophilic , low viscosity resin that promotes bonding to substrate such as

dentin Coated in thin layer. It is thinned with gentle air burst for 1-2 secs.

Research is going on to determine the exact function of intermediate resin in acid etch

procedure.

- Some investigations conclude that intermediate resin is necessary to achieve proper

bond strength.

- Sealing permits a relaxation of moisture control.

- Sealants permits easier bracket removal.

- They protect against enamel tear outs at Debonding

Light polymerizing resins-

Permits relaxation of moisture control

Provides cover over adhesive voids - indirect bonding

Ceen & Gwinnet- Light polymerized sealants protects enamel adjacent to brackets

from dissolution & surface lesions.

Permit easier bracket removal

Chemical curing primers-

Poor polymerization

Drift

Low resistance to abrasion

Self Etching Primers (SEP‘s)

Main feature of single step Etch/primer bonding system is that no separate acid

etching of enamel & subsequent rinsing with water & air spray required. Liquid itself has

component that conditions enamel.

Active ingredient of self etching primer is a methacrylated phosphoric acid ester that

dissolves calcium from hydroxyapatite. Removed calcium forms complex & is

incorporated into network when primer polymerizes.

Etching & monomer penetration to exposed enamel rods are simultaneous.

3 mechanisms for self etching process-

1. Acid groups attach to monomer are neutralized by forming a complex with calcium

from hydroxyapatite.

2. Solvent is removed from primer during airburst step, viscosity rises showing transport

of acid groups to enamel interface.

3. Primer is cured & monomer are polymerized, transport of acid groups to interface is

stopped.

Clinical procedure-

1. Dry tooth surface.

2. Apply Transbond Plus

1st compartment- Methacrylated phosphoric acid ester

Photosensitizers

Stablizers

2nd

compartment- Water soluble fluoride

3rd

compartment- Applicator microbrush

Sqeeze & fold first compartment over second activates

system. The mixed component then ejected into 3rd

to wet applicator tip. Rub thoroughly

atleast 3 secs & always wet surface with new solution to ensure monomer penetration

3. Bond bracket with Transbond XT & cure with light

Scanning electron microscopy shows following etching pattern -

••

Study by Helen Grubisa et al – shear bond strength with SEP‘s is less than

conventional acid etching. AJO 2004

Moisture Insensitive Primers-

Reduce bond failure under moisture contamination hydrophilic primers that bond in wet

condition. They contain hydrophilic methacrylated monomer

Transbond MIP, 3M/Unitek

Acid etching SEP treated

Indications-

Second molar bonding

When there is risk of blood contamination on half erupted teeth or on impacted teeth

Hydrophilic resins polymerize in presence of slight amount of water but will not

routinely compensate for saliva contamination.

Literature 1. Effect of self etch primer on shear bond strength of orthodontic brackets

Samir Bishara & Leigh Von Wald

AJO 2001

• Their study concluded that use of self etch primer resulted in low but clinically

acceptable shear bond strength.

• Comparison of ARI scores – More residual adhesive remained with self etch

primer.

2. Bonding of stainless steel brackets to enamel with new self etch primer

Ryan Arnold et al AJO sep 2002

• Bond strength of stainless steel brackets using Transbond self etch primer

Four groups

A- Conventional etchant with separate primer

Group B

a- Self etch –15 sec Before

b- Self etch - 2 min bonding

c-Self etch - 10 min

Conclusion –

• No significant difference in bond strength between the two groups.

• 10 min delay in bonding after application of self etch primer might not be

deleterious for adhesion

3. Asgari et al (JCO 2002) did a clinical study of Transbond SEP in 20 patients

=> the bond failure rate using Transbond Plus Self Etching Primer was significantly less

than the bond failure rate in those quadrants where a 37% phosphoric acid etchant was

used.

•• 44.. BBOONNDDIINNGG STEPS

Four steps

1. Transfer

2. Positioning

3. Fitting

4. Removal of excess

Instruments-

••

Transfer-

Bracket is gripped with pair of cotton pliers or reverse action

tweezer & mixed adhesive is applied to back of bonding

base.

Earlier brackets were welded to band.

Disadvantages of this technique includes-

Extensive chair time

Frequent screening for caries

Periodontal – leaching of cements

••

Positioning- Placement scaler can be used to place bracket on tooth surface.

For Vertical positioning-Height gauges/boon‘s gauge is used

where as for horizontal positioning mouth mirror can be used.

Bracket pushed against the surface firmly. Tight fit is very

important as it results in

- Good bond strength

- Little material for debonding

- Optimal adhesive penetration at bracket base.

- Reduced slide

Undisturbed setting-optimal bond strength ••

•• RReemmoovvaall ooff eexxcceessss-- - Prevent or minimize gingival irritation & plaque build up

- Reduces periodontal damage

- Prevents Decalcification

- Improve aesthetic appearance

••

Removing excess adhesive why?

• To minimize gingival irritation by preventing plaque accumulation around the

periphery of bracket base.

• To reduce periodontal damage

• To prevent possibility of decalcifications.

• It avoids bridging when tooth are crowded

• Improves esthetics.

• Facilitate debonding.

Small & large TC burs are used to remove excess set adhesive

Curing - Once excess is removed it is cured.

Curing lights

• Tungsten quartz halogen light

• Argon laser

• Xenon plasma arc light

• light emitting diode curing units[LED]

• Pulsed xenon plasma arc light

Tungsten quartz halogen curing light

when electric energy is passed

Halogen bulb

Tungsten filament is heated HEAT

LIGHT

Selective filters – blue light [ 400-500 microns]

• 40 seconds per bracket

• 15 minutes – both arches

Disadvantages

• Time consuming

• Light output < 1% of consumed electricity

• Lifetime – 100hrs

• High heat - degrades components of bulb

Argon laser • Introduced in the late 80‘s & early 90‘s

• Promised to reduce the curing time dramatically

• 480 microns wavelength

• Curing time

• 3 secs – per bracket

• 1 min – both arches

• KELSEY ,POWELL

To equal bond strength of 40 sec exposure by conventional curing light argon laser must

cure for 10 seconds

Disadvantages

• Laser unit large

• expensive

Xenon plasma arch light • Introduced in the late 1990‘s

• Short exposure time at lower cost

• Curing time

3 – 5 secs per bracket

Comparison of efficiency of xenon plasma

light and conventional curing light Sheldon Newman et al AJO 2001

• Exposure time

40 secs - conventional curing light

3 , 6 , & 9 secs – xenon plasma light

• Bond strength

xenon light > with longer exposure time

• To equal bond strength of conventional curing light the exposure time with xenon

had to be 6 –9 seconds

Light emitting diode curing units Mills –1995

• Instead of hot filament – Halogen bulb.

• LED – junction of doped semi conductors.

Advantages;

• Lifetime 10, 000 hrs

• Requires no filters

• Resist shock and vibration

• Little power to operate

• Newer –GALLIUM NITRIDE ( LED )

400-500microns

• Optimum curing time ?

• Replace halogen bulbs ?

Mills et al ( BJO 1997 )

• Compared light source containing LED to Halogen units

• Concluded – LED curing units cured composites to significantly greater depths

when tested at 40 & 60 sec

Polymerization of resin cement with LED curing unit

William Dunn & Louis Taloumis

AJO sep 2002

• Compared the shear bond strength of orthodontic brackets bonded to teeth with

conventional halogen light and LED curing units .

• Concluded- LED curing units bonded brackets to enamel as well as Halogen

based curing lights

Pulsed Xenon Plasma Arc Light

Polymerization shrinkage – Over come

-Curing composite in layers

-Pulsed curing light

Pulsed curing light- unit light is a series of pulse to polymerize the adhesive

Facts • In the study by Eliades et al the DC value for a light cured adhesive bonded to a

metal bracket and irradiated from incisal & cervical edges was comparable to DC

values for a chemically cured adhesive & its light cured counterpart bonded to

ceramic brackets

• J Dent Res 1992 (sp Issue) 71:169

Bikram S Thind & David R Stirrups ( EJO 2006) compared tungsten quartz halogen,

plasma arc and LED light sources for polymerization of an orthodontic adhesive and

concluded that polymerization as effective as conventional bulb light sources was

obtained with short exposure times recommended for plasma arc or LED

Similar results have been got for Argon laser (Bryan S, Angle Orthod 2006) where it is

concluded that exposure time beyond 5 sec and power setting beyond 150mW has no

cumulative effect on the shear bond strength of stainless steel orthodontic brackets.

• The concept of ―total energy,‖— the reciprocity between power density and

exposure

• The concept of ―total energy‖ does not hold for orthodontic light-cure bracket

bonding. An exposure time of less than 4 seconds, irrespective of the power

density, cannot guarantee sufficient bracket bond strength. There seems to be an

advantage of power density over exposure duration in the context of metallic

bracket bonding.

Am J Orthod Dentofacial Orthop Oct 2008;134:543-7

These results show that, for an efficient light-cure bracket bonding, there is an absolute

lower limit of exposure duration (4 seconds) and an upper limit of useful power density

(3000 mW/cm2).

• The polymerization only begins at the edges of the bracket base and then

continues as a chain reaction.

• The light-initiated bonding resins under metal brackets may take as long as 3

days to reach maximum polymerization or strength.

• Reynolds and von Fraunhofer (1976) investigated the minimum bond strength

values required in direct orthodontic bonding systems with bracket placement and

confirmed that bond strengths of

5.9 – 7.8 MPa are clinically acceptable.

Various Factors Can Affect Bond Failure

1. operator technique and manual dexterity,

2. patient behaviour,

3. variation in the enamel surface,

4. the type of etchant used

5. its duration of application,

6. the adhesive Influence of different tooth types on the bond strength

• Mattick and Hobson (2000) showed that the etched enamel surface varied

between different tooth types => influence bond strength.

• Linklater and Gordon (2001) and Hobson et al. (2001) => significant differences

in the bond strength of different tooth types

• no significant differences between upper and lower teeth of the same type (

Linklater and Gordon, 2001 ).

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A post-treatment evaluation, after 9-20 months of routine orthodontic therapy

Bjorn U. Zachrisson (EJO 2007)

• overall failure rate = 11 per cent

• The brackets most prone to come loose, maxillary first molars =27%

• mandibular first molars = 24%

• Mandi. second molars = 18% molars.

• all other teeth = lower than 10 %

• canines = lowest debonding rates (4-6%)

BBoonnddiinngg ttoo MMoollaarr-- In young patients second molars bonding is advantageous.

Resin modified GIC (chemical & light cured)- bond to saliva contaminated enamel

surface without phosphoric acid etching

Liquid- Polyacrylic acid, maleic acid

It removes contaminants & change surface mechanically

It do not produce micromechanical retention.

Disadvantages-

1. Do not create micromechanical retention as good as 37% phosphoric acid.

2. Bond strength is lower.

Bonding to Premolar-

-Most difficult technical problem

-Visibility - mouth mirror is recommended.

-Newly erupted mandibular premolar gingivally offset brackets

are recommended.

••

Ligation of Bonded Brackets-

Bonded brackets will not withstand heavy pull on arch wires.

Steel ties are safer than elastomers & definitely are more hygienic.

Rule of Thumb - ligature wire should be twisted with the strand that crosses arch wire

closest to bracket wing. This tightens ligature when end is tucked under arch wire.

- Push arch wire into bottom of slot using fingers for flexible wires & plier or

ligature director for stiffer wire & make passive ligation.

- If full engagement is not possible, ligature can be retied at next visit.

•• Ligature less, self ligating, low friction brackets are available now- SPEED system

Advantages-

a. Saves time.

b. Reduces friction.

c. Increases patient comfort

•• FFiirrsstt DDiirreecctt bboonnddiinngg It was done in Eastman Dental Center in 1966

Round metal brackets with single groove 0.019×0.025 inch slot were used

Adhesive was Plastic resin base with liquid monomer of methyl-2-cyanoacrylate &

silicate filler

Working time- 1 min

ST- 2-4 min

•• Acid Etching- 50% phosphoric acid & 7% zinc oxide- 45 secs

- Only 4 upper anterior teeth bonded

- In few cases canines were bonded

- Arch wires placed in next visit

BRACKETS-

11.. Plastic Brackets-

They are made up of polycarbonate & are used mainly for esthetic purpose.

Pure plastic brackets lack strength to resist distortion & breakages, wire slot wear, uptake

of water, discoloration, & need for compatible bonding resin.

Such brackets may be useful in minimal force situation & for treatment of short duration.

New types of reinforced plastic brackets with or without steel slot inserts have presently

being introduced.

2. Ceramic Brackets-

Theoretically porcelain brackets made of aluminum oxide could combine esthetics of

plastic & reliability of metal brackets.

Two forms currently available are-

1. Polycrystalline- Made of sintered or fused aluminum oxide particles.

Eg- GAC Allure, Unitek 3M Transcend 2000.

2. Single crystal form-‗A‘ company starfire.

Both of them resists staining & discoloration.

Ceramic brackets bond to enamel by 2 mechanisms-

a. Mechanical retention via indentation &b undercuts in the base.

b. Chemical bonding by means of silane coupling agent.

With mechanical retention the stress of debonding is generally at adhesive bracket

interface, whereas chemical bonding may produce excessive bond strength with stress at

debonding shifted towards enamel-adhesive interface.

Drawbacks-

1. Frictional resistance between orthodontic wire & ceramic bracket is greater & less

predictable than with steel brackets therefore optimal force levels & anchorage control

are difficult to determine.

2. Not as durable as steel brackets & brittle by nature( break easily)

3. Harder than steel & induce enamel wear of any opposing teeth.

4. Debonding is difficult- wing fractures easily.

5. Surface is more rougher & more porous attracts plaque & stains surrounding enamel.

6. Added bulk required to provide adequate strength makes oral hygiene difficult.

3. Metal Brackets-

Although not as esthetically pleasing as ceramic & plastic brackets , small metal

attachments are improvement over bands metal brackets rely on mechanical retention for

bonding & mesh gauge is conventional method of providing retention. Photoetched

recessions or machined undercuts are also available.

The base of the bracket must be small ( not smaller than bracket wings therefore of

danger of demineralization around periphery) as it avoids gingival irritation & should be

designed to follow tissue contour along gingival margin.

Corrosion of metal is a problem & black & green stains appeared with bonded stainless

steel attachments. Hence increased interest fore corrosion resistant & biocompatible

brackets like titanium.

4.Gold coated Brackets-

- Used particularly for maxillary premolar, mandibular anterior & posterior teeth.

- More hygienic & neater.

- Corrosion is not found clinically

Adhesive Precoated Brackets

Advantages

1. Better control over

flash removal

2. Better slot orientation

3. Moisture tolerant

4. Better resin hygiene

5. Convenience

Clinical comparison of APC bracket v/s uncoated ceramic bracket

system

- Verstrynge et. al, OCFR 04 Materials & methods

RCT with APC Clarity®

v/s Clarity®

+ Transbond XT®

20 pts. Requiring fixed mechanotherapy.

ARI at debonding was recorded.

Results

No significant diff. in ARI scores b/w the 2 groups.

The 2 groups performed identically.

INDIRECT BONDING--

Several techniques for indirect bonding are available. Most are based on procedures

based on procedures described by Silverman & Cohen. Most current indirect bonding

techniques are based on based on modification introduced by Thomas. In these

techniques brackets are attached to teeth on patients models, transferred to mouth with

some sort of tray into brackets become incorporated & then bonded simultaneously.

Advantages-

1. Brackets can be placed more accurately.

2. Clinical chair time is decreased.

Disadvantages-

1. Removal of excessive is more difficult & more time consuming.

2. Risk for adhesive deficiency under brackets is greater.

3. Failure rates are high.

4. Technique sensitive

5. Chairside procedure very crucial.

6. Risk of adhesive leakage to interproximal gingival areas.

Reasons for difference in bond strength between direct & indirect techniques-

1. Bracket bases may be fitted closer to tooth surface with one point fitting by placement

scaler than when a transfer tray is placed over teeth.

2. A totally undisturbed setting is obtained more easily with direct bonding.

Several indirect bonding techniques have proved reliable in clinical practice. They differ

in way brackets are attached temporarily to model ( caramel candy, laboratory adhesive,

bonding resin), the type of transfer tray (silicone, acrylic with transfer arms) .

SILVERMAN AND COHEN – 1972 • MMA and UV light activated unfilled BISGMA

• MMA was applied to the plastic bracket base on the patient‘s model

• BISGMA –intermediary adhesive between the patients etched enamel & pre set

adhesive on the bracket base

• Updated technique – 1974 by same authors

• Used perforated metal bracket bases and only one adhesive- BISGMA[ UV light

activated]

• Increased operator working time as polymerization did not occur

THOMAS TECHNIQUE 1979 • Filled BISGMA resin placed into the bracket bases

• Attached to the stone model

• Before setting all excess material is removed from the cast around the brackets

• Transfer tray made of flexible material

• Tray + brackets removed from the cast as single unit

• Teeth of one arch isolated +etched

• Liquid unfilled resin formed the interface between etched enamel and filled resin

• Liquid catalyst – tooth

• Base resin – brackets

• Unfilled resin not pre mixed – working time increased

• tray seated held till polymerization is complete

Silicone Tray technique-

1. Make an impression & pour a stone model

2. Select brackets for each tooth

3. Apply a small portion of water soluble adhesive on each base or tootrh.

4. Position brackets on model. Check all measurements & alignments. Reposition if

needed.

5. For silicone tray fabrication , mix material . Press the putty onto cemented brackets.

Form a tray allowing sufficient thickness for strength.

6. After silicone has set, immerse model & tray in hot water to release the brackets from

stone. Remove any adhesive under running water.

7. Trim tray & mark midline

8. Prepare patients teeth as for direct bonding

9. Mix adhesive, load it in syringe. Apply a sufficient portion to bonding bases.

10. Seat tray on the prepared arch & hold with firm & steady pressure for about 3 mins.

11. Remove the tray after 10 mins. The tray may be cut transversly or longitudinally to

reduce the risk of bracket debonding when peeled.

12.Complete bonding by careful removal of excess flash. Use a scaler & oval or tapered

TC bur to clean tray properly around bracket

Above steps are shown in following figure-

Indirect bonding

Moin & Dogon technique AJO 1977 • Pour impression in stone

• A drop of sticky wax is placed on teeth surfaces of cast

Brackets are warmed over flame and set on the cast

• Impression made with polyether material

• Tray separated from cast but brackets remain in situ

• Bracket is removed from the cast &warmed to remove

residual wax

• They are placed into the impression

• Teeth are pumiced,etched & isolated

• Enamel surface is sealed with mixture of universal &

catalyst sealant

• bracket base is covered with the adhesive

• tray is seated

• Use of sticky wax-corrections can easily

&readily be made until optimal bracket

alignment is obtained

• Previously used

• Adhesive tape - bracket displacement

• Bonding resin – cleaning of bracket base prior to

bonding difficult and time consuming

A new approach to indirect bonding technique using light-cure

composites - AJO-DO 1997

- Paul Kasrovi et al Conventional indirect bonding –

Non-transparent trays

Poor visualization

Self-cure resin – difficult to clean-up on setting

Time lost in removing set flash

Improperly seated tray revealed only after removal – misplaced brackets, failed

procedures

• Modifies the fabrication of transfer tray

• Provides direct visualization & access to the brackets - during both lab and

clinical procedures

STEPS

• Lab adhesive for IDB

Technique is highly predictable & reproducible

Visibility and accessibility from start to finish

Ability to remove composite flash before curing

Double sealant technique- Steps-

1. Bonding adhesive paste – attach brackets to model

2. Excessive adhesive removed

3. After 10 min, placement tray is vaccum formed

4. Trays with model placed in water

5. Tray separated and trimmed with gingival edge within 2mm of brackets

6. Midline marked

7. Bonding base lightly abraded with stone point

8. Oral prophylaxis, isolation & etching

9. Tooth- Universal sealant resin

Bracket base- catalyst sealant resin

10. Tray seated - held for 3 mins

11. Peel it from lingual towards buccal

12. Remove excess

Advantages-

1. Clean up is simple

2. Little flash

•• CCoommppoossiittee CCuussttoomm bbrraacckkeett bbaassee-- 1.Make an impression & pour up a stone model.

2.Select brackets for each tooth.

3.Isolate stone model with a separating medium.

4.Attach brackets to teeth on model

5.Check all measurements & alignments. Reposition if needed.

6.Make transfer tray for brackets. Material can be putty silicone, thermoplastics or

similar.

7.Remove transfer tray & gently sandblast adhesive base with microetching unit.

8. Apply acetone to base to dissolve remaining separating medium.

9. Prepare patient teeth for a direct application.

10. Apply Sondhi Rapid Set resin A to teeth surface & resin B to bracket base. If Custom

IQ is used, apply resin B to teeth & resin A to bases

11. Seat tray on prepared arch & apply equal pressure to occlusal, labial & buccal

surface for 30 secs & allow 2 mins or more of curing.

12. Remove excess flash of resin with scaler or contrangle handpiece & tungsten carbide

bur.

Above steps are shown in following figure-

•• RReessiinn uusseedd ffoorr IInnddiirreecctt BBoonnddiinngg ccoonnttaaiinnss ffiinnee ppaarrttiiccllee ffuummeedd ssiilliiccaa ffiilllleerr

wwhhiicchh aavvooiidd vvooiiddss It has quick set time- 30secs which allows rapid removal of tray in 2mins

Indirect bonding technique- ANUP SONDHI •• LLaabb pprroocceedduurree--

1. Working models from accurate alginate impression

remove air voids

2. Apply thin layer of diluted separating medium

Dry for 1 hr

3. If APC brackets- place directly

If non-coated- Place Transbond XT adhesive on base

4. Place all brackets

5. Check for final bracket placement

6. Place models in TRIAD 2000 curing unit

7. Cure for 10 minutes

If clear esthetic brackets- cure for 1 min

8. Use light separating spray to fascilitate easy removal of tray from

brackets

Silicon/ light cooking spray like PAM.

Spray for less than 1 secs

9. Tray is made

Biostar unit- Vaccum formed tray with 1.5 mm thick layer of bio-

plast , overlayed with 0.75mm thick layer of Biocryl

Outer layer- rigidity

Inner layer- easier removal

10. Soak tray for 1 hour- separating medium dissolves

11. Tray sectioned with bur

12. Once trimmed place in TRID unit to ensure curing of uncured resin

13. Clean tray with ultrasonic cleaner with dishwashing detergent for 10 mins then with

water-for 5 mins

Microetching is done to remove any adhesive remnant

•• CClliinniiccaall sstteeppss-- 1. Antisialagogue- atropine/ propantheline is given to decrease salivation

2. Polish teeth with pumice

3. Tray can either Single tray / segmented depending on the type of malocclusion

Segmented tray is used in case of crowding

4. Isolation

5. Dry teeth

6. Etching- 15secs

Suction gel off. Water sprayed 30secs

7. Apply primer, air dry for 2secs

8. Resin poured in wells. Apply resin A on tooth surface & resin B on

bracket base

••

9. Position tray & seat it in hinge motion. Apply equal pressure for

30 secs. It is cured for 2 mins

10. Remove outer layer using scaler

11. Remove inner layer using scaler & fingers

12. Scale excess resin & floss interproximal areas

FFlloowwaabbllee LLiigghhtt--CCuurreedd AAddhheessiivvee

•• PPEETTEERR GG.. MMIILLEESS JJCCOO22000022

AAppcc bbrraacckkeettss uusseedd

A Thermal-Cured, Fluoride-Releasing Indirect Bonding

System • R .S. Nanda, P.K. Sinha JCO 1995 • Heat the cast with the brackets in place in a countertop toaster-oven, set at 325°F,

for 20 minutes. This process will cure the composite resin. Calibrate the oven

thermostat monthly with an oven thermometer. Remove the model from the oven,

and let it cool. .

Make a transfer tray from silicone impression material or a vacuum-formed plastic sheet.

We prefer the silicone material, which is manipulated to encapsulate the brackets and

make an impression of the model. This allows all the brackets to be bonded

simultaneously in their predetermined positions.

Mix Maxicure* sealants \ and B Th

sealant, which contains hydrogen fluoride m >S

monomer, reaches its initial set in 60 second* and therefore no time should be wasted

once n has been mixed.

Indirect Bonding with

a Thermal Cured Composite

Elliott M. Moskowitz • modification of the Thomas technique

1. Thermally cured composite material.

2. Reprosil—a vinyl polysiloxane impression material (PVS) as a highly accurate but

flexible inner tray that can be easily removed.

3. Vacuum-form Essix 0.020 inch (0.5 mm) clear material tray that covers the PVS inner

tray

Place the ThermaCure composite resin on

the pad of each bracket, taking care to cover

all of the pad surfaces. The

ThermaCure provides virtually unlimited

working time

Casts placed in toaster oven for curing at

325°F for 15 minutes

2. Apply the Reprosil impression material with

a syringe over the thermally cured brackets

3. Vacuum-form Essix (trademark of Raintree

Essix, Inc., New Orleans, LA) 0.020 inch

(0.5 mm) or 0.030 inch (0.75 mm) clear

thermoplastic material over the cast, brackets,

and undertray complex

To remove the air-inhibited layer of adhesive,

lightly abrade the composite back of

each bracket base with a Micro Etcher

Mix 2 drops each of Enhance (Reliance

Orthodontic Products, Itasca, IL) A and B

primer. Apply the mixture to the composite

bases and the tooth surfaces.

The flexible undertray is teased away with

an explorer or scaler without dislodging the

brackets.

•• BBoonndd SSttrreennggtthh--

Ratio of debonding force by interfacial area of adhesive or bracket base.

Bonding area- 16mm2

Debonding force- 120N

Bond Strength- 7.5 N/mm2 or 7.5 MPa

Able to withstand stress of 6-8 MPa

Various Factors Can Affect Bond Failure

1. operator technique and manual dexterity,

2. patient behaviour,

3. variation in the enamel surface,

4. the type of etchant used

5. its duration of application,

6. the adhesive Influence of different tooth types on the bond strength

• Mattick and Hobson (2000) showed that the etched enamel surface varied

between different tooth types => influence bond strength.

• Linklater and Gordon (2001) and Hobson et al. (2001) => significant differences

in the bond strength of different tooth types

• no significant differences between upper and lower teeth of the same type (

Linklater and Gordon, 2001 ).

European Journal of Orthodontics 30 (2008) 407–412

A post-treatment evaluation, after 9-20 months of routine orthodontic therapy

Bjorn U. Zachrisson (EJO 2007)

• overall failure rate = 11 per cent

• The brackets most prone to come loose, maxillary first molars =27%

• mandibular first molars = 24%

• Mandi. second molars = 18% molars.

• all other teeth = lower than 10 %

• canines = lowest debonding rates (4-6%)

•• LLiinngguuaall OOrrtthhooddoonnttiiccss

LINGUAL BRACKET POSITIONING ( INVISIBLE RETAINERS)

Lingual orthodontics has added a new dimension to bonding spectrum, however

questions have arisen with regard to lingual bonding procedures & how, if at all they

should differ from labial bonding procedures.

The technique rapidly gained popularity in early 1980‘s, but most clinicians

experienced considerable difficulties particularly in finishing stages & abandoned the

technique for routine use.

The development was pioneered in Japan by Fujita who worked on

mushroom arch, & by several American orthodontists: Kurz, Kelley &

more recently by Creekmore. Although it appears possible to treat

malocclusion successfully from lingual side, a combined lingual & buccal

segmental approach may offer a number of options with no great esthetic

compromises n most patients.

- More precision is necessary for adjustment of lingual arch wires with

reduced bracket distance.

- If lingual treatment is to become more important in future, additional

improvements in bracket design & technical aids are needed.

- Pronunciations difficulty occur immediately after insertion.

- Difficult & time consuming.

- Working position awkward.

Customized brackets are formed after scanning malocclusion model

using a high resolution optical 3-D scanner. Brackets then designed in

computer using computer aided manufacturing technology. High end

rapid prototyping machines are used to convert virtual bracket series

into wax analog that is then casted into alloy with high gold content.

•• BBOONNDDIINNGG TTOO OOTTHHEERR MMEETTAALLSS--

Many adult patients have crown & bridge restorations fabricated from porcelain & non-

precious metals or gold. Recent advances in materials & techniques indicate however that

effective bonding of orthodontic attachments to surface other than enamel may now be

possible

.

Intraoral Sandblasting-

Microetcher - Uses 50µm white or 90µm tan aluminum oxide at 7kg/cm2 pressure

Uses-

-Rebonding loose bracket

-Increases retentive area inside molar band

-Create retention for bonded retainers

- Bonding to decidous teeth.

BONDING TO PORCELAIN-

In 1986 Wood et al showed that roughening the porcelain surface, adding a porcelain

primer & using a highly filled adhesive resin when bonding to glazed porcelain added

progressively to bond strength.

In vitro studies have shown that bond strength to porcelain equals or surpassed that

obtained after bonding to acid etched enamel which suggested possible damage to

porcelain tooth surface during debonding.

Two different techniques-

1. Hydrofluoric acid gel – Excellent result

2. Sandblasting & silane (Scotchprime)

3. Others-

Roughninig with diamonds or stones

1. Conventional acid etching is ineffective in preparation of porcelain surfaces for

mechanical retention of brackets. However , several porcelain etchants have been

developed. The most commonly used etchant is 9.6% Hydrofluoric acid. In gel form for 2

to 4 mins.

Hydrofluoric acid is strong & requires careful isolation of working area, cautious

removal of gel with cotton roll, rinsing with high volume suction & immediate drying &

bonding.

Etchant produces microporosities on porcelain surface that achieves mechanical

retention. Etchant porcelain will have frosted appearance similar to etched enamel.

Other studies indicate that 1.23% or 4% Acidulated Phosphate Fluoride(APF) for

10 mins solution or gel containing sodium fluoride, phosphoric acid & hydrofluoric acid

may provide equivalent bond strength.

Procedure-

1. Isolate working field adequately.

2. Use barrier gel such as Kool-Dam to prevent flow of gel in gingiva or soft tissues.

3. Deglaze area slightly larger than bracket by sandblasting with

50Mm aluminum oxide for 3 secs.

4.Etch porcelain with 9.6% hydrofluoric acid gel for 2 mins.

5. Remove gel with cotton roll & rinse using high volume suction.

6. Immediately dry with air & bond bracket.

2. Porcelain surface is sandblasted with aluminum oxide to create

rough surface

If allergic to Al.oxide- Silicon carbide

Silane coupling - γ-methacryloxy-propyltrimethoxysilane which provides reactive sites

for inorganic & organic components.

Methacrylate groups- covalent bond with polymer matrix

Hydrofluoric acid cannot be used for high alumina porcelain & glass ceramics where

silica coating can be used.

•• Debonding-

Gentle 45 degree outward pull applied to gingival tie wings

Residual adhesive- remove with tungstun carbide bur

Smoothing- slow speed polishing rubber wheel

Polishing- Diamond polishing paste in rubber cup

• Surface preparation for orthodontic bonding to porcelain

ZACHRISSON et al AJO 1996

HF acid gel = sand blasting + silane

• Some authors feel

Sand blasting + silane = high failure rates

AJO-DO 1998 Zachrisson showed HF produce extensive in depth penetrating pattern

.But diamond roughening & microetching produce only surface peeling.

AJO –DO 2004 Mutlu Ozean et al superior bond strength is obtained when ceramic

surface is pretreated with silica coating & silanization giving about 13.6 MPa particularly

with polycarbonate brackets. Bond failure site is at bracket / adhesive interface.

••

BONDING TO AMALGAM-

Techniques for bonding to amalgam includes-

1) The method of choice for bonding to hardened amalgam with any orthodontic adhesive

is to increase surface by sand blasting.

2) Intermediate resin that improves bond strength- All Bond 2

3) Adhesive resin that bond chemically to metals- 4-methacryloxtethyl trimellitate

anhydride (4-META) & 10-MDP /Bis-GMA resins.

Strongest bond to amalgam were obtained with 4-META adhesive9Superbond C & B)

Procedure-

For small amalgam fillings-

1. Sandblast amalgam with 50Mm aluminum oxide for 3 secs.

2. Condition surrounding enamel with 37% phosphoric acid for

15 secs.

3. Apply sealant & bond with composite.

For Large amalgam fillings-

1. Sandblast amalgam with 50Mm aluminum oxide for 3 secs.

2. Apply a uniform coat of Reliance metal primer & wait for 30 secs.

3. Apply sealant & bond with composite.

••

•• BBOONNDDIINNGG TTOO GGOOLLDD--

Until recently bonding to gold & other metals was considered difficult. In 1980‘s some

adhesives ( Enamelite 500, Goldlink) & primers (Fusion) were designed to allow such

bonding however published reports & clinical experience do not support their

effectiveness.

Roughening gold surface with green stone was found by Wood et al to significantly

increase bond strength to a highly filled resin system. However the breakthrough came

with intraoral sandblasting. A hand piece abraded surface may look rough eye, but SEM

studies indicate that micromechanical retention of metals can be increased by atleast

300% using intraoral sandblasting.

The micro etcher which uses 50 micron while aluminum oxide or

silicon carbide particles approximately 7kg/cm2 pressure has been most

advantageous for bonding to gold & other metals. During a quick 3

second blast with fingertip control & high speed evacuation the

abrasives creates a retentive surface to which bonding & composite resin

(Concise) is greatly enhanced.

Tin Plating-

New voltage tin plates also facilitate intraoral bonding to noble metals. The deposition of

layer of tin on gold surface permits a chemical & mechanical bond between resin &

metal.

Most commonly the tin is electrolytically deposited with a unit such as Micro Tin or

Kura Ace Mini.

Tin plating is not approved by Food & Drug administration for intraoral use.

Alternative method is to rub on a solution of gallium Or tin alloy with a pure tin bar.

Alternative that bond chemically to Metal-

1. Two different types of adhesives 4-META resins ( Methacryloethyl trimellitate

anhydro) & 10-MDP bisGMA have been recently developed to improve adhesion to

metals.

2. Super bond C & B is activated by combining 4-META & tributyl borane monomers &

then adding polymer powder to activated liquid.

3. Bond strength of any adhesive can be greatly increased by with intermediate resins

like All-Bond 2+ and Scotchbond MP (multipurpose).

Gloria Nollie et al in ANGLE 1997 reported that Type –1V gold treated with adlloy

has increased bond strength & gives twice as strong as those found in microetched gold.

BONDING TO COMPOSITES- 1.Outer layer removed with diamond /carbide bur

2. Etch- 37% phosphoric acid

3. Apply silane coupling agent

4. Bonding

••

BONDING TO ACRYLICS-

- Wet surface with MMA for 3 mins

- Bond using unfilled resin & composite

Deciduous teeth • The outer prismless enamel layer

• lacks the characteristic prism markings of enamel

• no well-developed etch pattern with well-defined prisms

• The enamel crystallite diameter of deciduous teeth is relatively larger than

permanent teeth

• The chemical compositions of calcium and phosphorus => similar

• A recommended procedure for conditioning deciduous teeth ==

• sandblast with 50-μm aluminum oxide for 3 seconds to remove some outermost

aprismatic enamel

• etch for 30 seconds with the Ultraetch 35% phosphoric acid gel.

• The failure rate = less than 5%.

• Comparison of shear bond strengths of orthodontic brackets bonded to deciduous

and permanent teeth

Toshiya Endo AJO 2008 Aug

4 groups:

a. Permanent teeth – acid etch tech.

b. Permanent teeth – SEP

c. Deciduous teeth – acid etch

d. Deciduous teeth – SEP

Results =

The shear bond strengths of the brackets bonded to the deciduous teeth with either

adhesive system were lower than those to the permanent teeth

SBS for all groups exceeded the clinically sufficient SBS i.e. 6 to 8 MPa

Enamel Fluorosis

• Fluorosed enamel =

• an outer hypermineralized and acid-resistant layer

• difficult to attach bonds because a reliable etched enamel surface cannot be

produced.

• Fluorosis manifests itself as defects in the subsurface enamel

As

• colour from white to brown

• as pits and irregular white opaque lines

• striations

cloudy areas

• Effects of adhesion promoters on the shear bond strengths of orthodontic

brackets to fluorosed enamel

Necdet Adanir et al EJO Dec 2008

evaluate the effect of enamel fluorosis on the SBS of orthodontic

brackets and to

determine whether adhesion promoter, Enhance LC, increases the bond strength of

brackets to fluorosed enamel.

• Results =

• fluorosis significantly reduced the bond strengths

• Enhance LC significantly increased bond strength on fluorosed enamel

In Vivo Bonding of Orthodontic Brackets to Fluorosed Enamel

using an Adhesion Promotor

James Noble et al AO 2008 • the success of bracket retention using an adhesion promoter with and without the

additional microabrasion of enamel.

• group 1 – microabrasion + acid etching + Scotchbond Multipurpose Plus Bonding

Adhesive

• Group 2 – acid etching + Scotchbond Multipurpose Plus Bonding Adhesive

• Conclusion

• Bonding orthodontic attachments to fluorosed enamel using an adhesion promoter

is a viable clinical procedure that does not require the additional micro-

mechanical abrasion step.

Miller JCO 1995 reported that microabrasion of fluorosed enamel concomitantly

with acid etching improves bond strength

•• RReebboonnddiinngg -Consumes more chair time

- It can be avoided by following rules for bonding

Procedure-

- Remove from archwire

- Remove adhesive from tooth surface with tungstun carbide bur

- Sandblast bracket

- Re-etch tooth surface for 15 secs.

Loose ceramic bracket- better to replace with new for optimal bond strength.

Optimization of a procedure for rebonding dislodged orthodontic brackets

B. Mui et al AO 1999

Compared shear bond strength (SBS) of bonded and rebonded orthodontic

brackets

Brackets debonded were rebonded after the removal of residual resin from

enamel surfaces using five different treatments

(1) Remove residual resin using a tungsten carbide bur, re-etch enamel surface, then

bond a new bracket

(2) ) Remove resin from the base mesh with micro-etching then rebond the same

bracket

(3) (3) Remove residual resin from the enamel surface using resin-removing pliers,

recondition the enamel with an air-powder polisher, then bond a new bracket

(4) (4) Remove residual resin using a rubber cup and pumice, then bond a new

bracket

(5) (5) Remove residual resin using pliers alone, then bond a new bracket.

(6) results =>

the light-cured system produced higher shear bond strength in the initial

bond than the self-cured system.

Reconditioning the enamel surfaces using a tungsten carbide bur and

acid-etching gave the highest SBS (difference 5.8 MPa; p<0.01) and clinically

favorable fracture characteristics.

• The optimal procedure for rebonding dislodged orthodontic brackets is to

resurface the enamel using a tungsten carbide bur, acid-etch the enamel, and use

a new or re-use an old bracket after microetching.

•• RReeccyycclliinngg-- Goal- remove adhesive from bracket without damaging bracket backing /distorting

dimensions of slot.

Only 4% of orthodontists in US use recycled brackets

Methods-

1. Heat (above 450) to burn resin followed by electropoloshing to remove oxide build

up

2. Solvent striping with high frequency vibrations & flash electropolishing

Electropolishing- Remove tarnish or oxide

Buchman- Changes in torque angle & slot size after 1/2 recycling were below

significance.

•• FFrriiccttiioonnaall EEffffeeccttss bbeettwweeeenn bbrraacckkeett && aarrcchh wwiirree-- Friction at interface between wire & bracket produces resistance to movement. It is

directly proportional to force at which contacting surfaces are pressed together.

Affected by nature of surface-

Rough/smooth

Reactive/passive

Though surface appears to be smooth microscopic irregularites present

Real contact occurs only at limited no of spots at peak of irregularity ASPERITES which

-Carry all loads

- Light load- cause appreciable plastic deformation

When force is applied- junctions shears as sliding takes place

When soft material slides against harder, small fragments of soft

material adheres to hard one

•• FFrriiccttiioonn ddeeppeennddss oonn --

1. Surface qualities of wires-

NiTi- greater surface roughness

Beta-Ti – greater frictional resistance

Cold weld to steel bracket – sliding impossible.

2. Brackets-

Steel –smooth

Titanium – sliding difficult

Ceramic –

Rough & hard

Can penetrate steel wires during sliding

Produces nicks & cuts in wire

To reduce friction metal slot can be used

•• 3.Force of contact-

- If tooth pulled along arch wire-initial tipping

- Friction based on contact angle at which corner of the

bracket meets arch wire. More the angle, more is the

friction.

•• Self ligating - reduced friction- effective sliding-better

anchorage control

APPLICATIONS OF BONDING-

1. BONDED RETAINERS-

Advantages-

1. Differential retention

2. Completely invisible from front

3. Reduced caries risk

4. Reduced need for long term patient co-operation.

5. Prolonged semi permanent as well as even permanent retention when conventional

retainers do not provide same degree of stability

•• Differential Retention-

Introduced by James L. Jensen, implies special attention is directed towards the strongest

or most important predilection site for relapse in each & every case.

Based on evaluation of-

Pre-treatment records

Habits

Patient cooperation

Growth pattern

Age

•• TTyyppeess--

Mandibular canine to Canine retainers

Mandibular premolar to premolar retainer

Direct contact splinting

Flexible spiral wire retainers

Hold retainers for individual tooth

•• Made of -

Thick wire- 0.030/0.032 inch

Thin wire- 0.0215 inch

DIRECT CONTACT SPLINTING-

- Prevent post orthodontic space opening & stability against traumatic jigging

-- Absolute moisture control is very important- rubber dam

- Toothpicks to avoid interdental flow of adhesive

- Bond breakage high- Need for independent physiological tooth

movement during function

•• BONDED SPACE MAITAINERS –

Several studies regarding bonded space maintainers have been described with varying

degree of short term success. Long term results on a group of

patients are not available for any design.

They are made of 0.032 inch s. steel wire/ 0.030 gold coated wire.

Utility wire design was used to reduce the influence of occlusal

forces

BONDED SINGLE TOOTH REPLACEMENT –

For most children having missing anterior teeth, replacement is made mainly by

removable appliance. Such appliances are sometimes damaging to periodontal tissues &

an inconvenience to patient.

Use of acid etched retainers cast appliances has been expanded to include other

appliances including posterior tooth replacement & tooth contouring.

Another method which is cheaper, simpler & more durable than cast variant for anterior

tooth replacement is by using acrylic prosthetic tooth & inserting into it 2 flexible braided

rectangular (0.016×0.022) & one round spiral wire (0.0195) for support.

Short clinical crowns can be utilized since rectangular braided wire is placed along

gingival margin. With round wire on either side & thus

frequently out of occlusion.

This type of replacement can be used during

orthodontic treatment. It can be attached to canine or

second premolar for better esthetics to avoid empty –

looking spaces in adults when premolar extractions are needed & invisible lingual

appliances are used.

••

SPLINTING OF TRAUMATIC INJURIES-

The goal of splinting traumatized teeth is to stabilize & to allow healing & prevent

further damage to pulp & periodontal structures.

Several types of traumatic splinting devices are conventionally used including band –

acrylic splint, contact splinting with composite & orthodontic bonded bracket plus arch

wire.

It has been demonstrated that clinical success has been achieved by using bonded plastic

wire and thick 0.032 inch stainless steel spiral wire.

COMPOSITE BUILDUPS-

The addition of composite resin to non- carious teeth during or after orthodontic

treatment may be indicated as an alternative to capping on single or multiple teeth to

solve tooth shape & / size problems.

In certain situations this buildup technique may be provide esthetic improvement of the

orthodontic results. Eg.- small or peg shaped lateral, congenitally missing lateral.

As shown in below figure restoration of peg lateral to normal size & shape.

•• DDEEBBOONNDDIINNGG--

DDeeffiinniittiioonn::

TToo rreemmoovvee tthhee aattttaacchhmmeenntt aanndd aallll tthhee aaddhheessiivvee rreessiinn ffrroomm tthhee ttooootthh aanndd rreessttoorree tthhee

ssuurrffaaccee aass cclloosseellyy aass ppoossssiibbllee ttoo iittss pprree--ttrreeaattmmeenntt ccoonnddiittiioonn wwiitthhoouutt iinndduucciinngg iiaattrrooggeenniicc

ddaammaaggee..

Objectives-

Remove attachment & all adhesive resin from tooth surface

Restore surface as closely as possible to its pre treatment condition

DDEEBBOONNDDIINNGG OOFF BBRRAACCKKEETTSS::

PPrriinncciipplleess::

11.. MMiinniimmuumm ddaammaaggee ttoo eennaammeell –– ffrraaccttuurree

•• WWiitthhiinn bboonnddiinngg mmaatteerriiaall iittsseellff

•• BBeettwweeeenn bbrraacckkeett –– rreessiinn –– mmoosstt ddeessiirraabbllee

•• BBeettwweeeenn rreessiinn –– eennaammeell -- uunnddeessiirraabbllee

22.. FFaaiilluurree hhaass ttoo bbee iinndduucceedd bbeettwweeeenn bbrraacckkeett aanndd rreessiinn

33.. DDiissttoorrttiinngg mmeettaall bbrraacckkeett bbaassee –– nnoonn--rreeuussaabbllee

44.. RReemmaaiinniinngg aaddhheessiivvee cclleeaanneedd--uupp 55.. DDeebboonnddiinngg cceerraammiicc bbrraacckkeettss pprroobblleemmaattiicc

66.. BBrraacckkeett bbaasseess ccaannnnoott bbee ddiissttoorrtteedd

•• GGrriinndd bbrraacckkeettss –– rroottaarryy iinnssttrruummeennttss

•• MMeecchhaanniiccaall iinnsstteeaadd ooff cchheemmiiccaall bboonndd bbeettwweeeenn bbaassee aanndd

rreessiinn

•• HHeeaatt ttoo ssoofftteenn rreessiinn,, ffoorr eeaassyy rreemmoovvaall –– eelleeccttrrootthheerrmmaall //

llaasseerrss

DDeebboonnddiinngg FFoorrccee

•• IInn uunniittss NNeewwttoonn''ss ((NN)),, kkiillooggrraammss ((kkgg)),, oorr ppoouunnddss ((llbb))..

•• BBoonndd ssttrreennggtthh== tthhee ffoorrccee ooff ddeebboonnddiinngg

tthhee aarreeaa ooff tthhee bboonnddeedd iinntteerrffaaccee,, UUnniitt -- mmeeggaappaassccaallss ggrraammss ppeerr ssqquuaarree

cceennttiimmeetteerr..

AAnn aaddhheessiivvee--bbrraacckkeett ssyysstteemm sshhoouulldd bbee aabbllee ttoo wwiitthhssttaanndd aa ssttrreessss ooff aatt lleeaasstt 66--88MMPPaa

PROCEDURE Steel brackets-

1. Cutting -

-Tips of twin beaked plier against mesial & distal edges of bracket

& cut bracket off with peel force

•• 2. Sqeezing-

- Sqeeze bracket wing mesiodistally & lift it with peeling force

Adv- Useful on brittle, mobile or endodontically treated teeth

Disadvantages-

Brackets easily deformed

Break at adhesive-bracket interface- adhesive remnant on

enamel

•• 3. Peeling-

-Brackets gripped with removing plier & lifted outwards

at 45 angle

-It creates Peripheral stress concentration

-Advantage includes bracket remains intact & fit for

recycling

• Lift-off Debonding Instrument:

• A tensile force is placed on the adhesive bond through a wire loop hooked over

the bracket tie wings

• pulling the wings of the bracket directly away from the tooth surface.

• This method distorts the brackets the least and is preferred if recycling is a

consideration.

• Oliver and Pal (AJODO July 1989)

compared three methods of debonding:

• Method A— The mesial and distal wings of an edgewise twin bracket are

squeezed together with pliers.

• Method B— A shear force is applied with the blades of the debonding pliers or

ligature cutters positioned at the enamel/composite or composite/bracket

interface.

• Method C—

Use of LODI.

This may be used in two ways:

the arch wire – in situ

the slot keeper (a length of 0.018 ´ 0.022-inch wire embedded in a plastic handle)

In either case, the presence of a wire in the bracket should help to maintain the

slot dimensions.

• Results :

• Method B => most distortion (majority on the base).

• Method A => All parts equally affected

• Method C => wing distortion only.

• Most of the debonded brackets had increased slot dimensions compared with

control brackets, the greatest being an increase of 0.032 mm.

• The clinical significance (increase in slot dimension) => loss of effective torque

from an arch wire.

• Conclusion –

Recycling of brackets is considered, then use of the lift off debracketing

instrument for bracket removal is most advantageous.

• Coley-Smith and Rock (BJO 1999) compared two methods of debonding (bracket

removing pliers or a lift off debonding instrument) in 507 metallic brackets, with

and without the archwire in place during debonding.

• After debond brackets were tested for slot closure by the fit of rectangular test

wires from 0·016X 0·022 to 0·021X 0·025 inch in size.

• Results :

• LODI produced few slot closures

• Bracket removing pliers used after removal of the archwire produced significantly

greater numbers of slot closures and distorted brackets.

• 10% of the brackets debonded using bracket removing pliers had distorted bases

• No base damage – LODI

When bracket removing pliers are used, the archwire should be left in place at the time of

debond since this reduces the number of distortions

•• CCeerraammiicc bbrraacckkeettss-- Ceramic – low fracture toughness

Metal deform- 20% under stress before fracture

Ceramic - < 1% before fracture

Common site of fracture - enamel-adhesive interface but metal bracket –adhesive

interface

Ripley- If retention is

Chemical & mechanical- fracture occurs at Enamel –Adhesive interface

Chemical- Bracket - fracture occurs at Adhesive interface

•• Reasons for failure during debonding is-

Stress incorporated during-

Ligation & arch wire activation

Force of mastication & occlusion

Stress applied during debonding

It creates cracks resulting in failure

•• MMeetthhooddss ooff DDeebboonnddiinngg-- 1. Mechanical

Pliers-

ETM 346 direct bond bracket removing plier

Transcend debonding wrench

-Sharp torsional force applied in downward direction

-Very painful

-Risk of bracket failure hence Bracket remains on tooth surface where removal in high

speed handpiece

-Time consuming

-Ceramic dust – itching, eye irritation hence safety glass should be worn.

• Bishara et al (AJODO 1999) compared the debonding characteristics of the two

brackets, using their appropriate pliers.

The most efficient method of debonding the Clarity bracket is to use the Weingart pliers

and apply pressure to the tiewings

The most efficient method to debond the MXi ceramic bracket is to place the blades of

the ETM 346 plier between the bracket base and the enamel surface.

• The mean shear bond strength

Clarity bracket (10.4MPa) >

MXi ceramic bracket (7.6 MPa).

• Clinically acceptable

• The Clarity brackets – greater rate of partial bracket failure with the Weingart

pliers compared the to the MXi brackets in which no failures were seen.

•• 2. Ultrasonic-

- Straight chisel tip with bevel of chisel towards bracket

- Flash- remove it before bracket removal

- Tip moved in MD direction until purchase pt / groove of 0.5 mm

made between bracket base & enamel surface

- Rocking motion applied to break bond

Advantages-

No bracket breakage

Can be used for metal brackets

Less time

•• 3. Electrothermal debonding (ETD)

- Heat used 3-0 joules total energy

- Given by Sheridan et al in 1986

- Rechargable direct current power unit connected to cylindrical

handpiece which ngets activated at 450ºF

- Debondig tip maintains constant temperature

- Width of tip is equal to width of vertical slot / saddle between M &

D tie wings of bracket

- When heat applied- it deforms Adhesive- Bracket interface &

bracket can be gently separated

Time- 3.2 secs

Composite softens – 300-392ºF

Bracket failure-

Complete- tie wing

break at bracket base

within body of bracket

Partial- fracture of bracket component in which part of bracket remains on tooth

surface

••

Paul Takle et al –Studied pulpal response, debonding time & pt response to ETD

AJO 1995

Conclusions were-

Pulpal hyperemia occurs 24 after debonding

Upto 30 days- inflammation to pulpal fibrosis persists

No discomfort except for burning smell

5 secs application – irreversible pulpal disease.

•• Advantages-

Better bracket removal without damage to enamel/ distortion of bracket

Failure site- E- A interface

Recyling of bracket

Comfortable

Disadvantages-

Pulpal damage

Adhesive remains on tooth surface

Burning smell

Straight handpiece- intraoral use difficult

• Jost-Brinkmann et al (EJO 1997) did an in vivo study in which 12 human

premolars scheduled for extraction were bonded with ceramic brackets which

were subsequently debonded using ETD.

• After 4 weeks, the teeth were extracted and histologically examined.

• No signs of pulpal inflammation were seen.

•• 4. Chemical debonding

Various chemicals used are-Acetone, Ethanol, Peppermint oil

Peppermint oil – viscous gel in 2ml syringe

Apply around bracket base & left for 2 min

Promotes failure at Enamel –Adhesive interface

No damage tooth

Reduces mean & maximal debond force from 103.7, 200N to 77 & 114N

respectively.

•• 5. Laser debonding

Ruby laser – first introduced in 1960‘s

Widely used in dentistry

Tocchio et al- degrades adhesive by 3 ways

1. Thermal softening- bracket slides off

Slow

•• 2. Thermal ablation- heating is very fast to raise the temperature of resin into vapours

It is rapid as bracket blown off

3. Photoablation- High energy laser interact with adhesive & energy level bonds between

resin rises rapidly above their dissociation energy level resulting in decomposition of

adhesive.

Bracket-blown off from tooth surface.

•• CO2 laser timing-

Super pulse- 2W for , <4 secs

Normal pulse- little more time

Pulp- heat propagation can result in pulp damage

It is found that 5.5ºC raise can result in necrosis but results shows that there is increase of

0.91ºC- after 1 sec of lasing

1.74ºC- 2 secs

2.67ºC- 3 secs

•• Ma et al – Debonding at 1.48 MPa of tensile load with CO2 laser at 18 W for 2 secs

Intrapulpal temp raise of 1.1ºC

Shear force to debond is less if MMA is used than BisGMA

•• Study by Samir Bishara - AJO 1992

Studied the 2 types of lasers-CO2 & Nd:YAG Laser

- Polycrystalline & monocrystalline brackets

Results-

- Polycrystalline- force decreased by factor by 25- CO2 laser at 14 watts for 2 secs

& there was complete bracket removal

- Monocrystalline- force decreased by factor of 5.2 at 7 watts

& Bracket cracked along slot in 2 of 10 cases

•• Advantages-

Heat is localized & controlled

Debracketing tool is cold

Can be used for various types of brackets- all designs

Atraumatic & safer

•• 6. Debonding With rubber dam-

- R.A.C.chate et al- safeguard during debonding as it

- Prevents inhalation/ingestion of fragments

- Isolation

Disadvantages-

- Gingival trauma due to inappropriate clamp application

- Respiratory distress – cannot be used in atopic individuals

••

•• 7. Arthur Wool-

He suggested hot water rinse before debonding

- Used Small wood burning pen which has cool cork handle, plugs into a 110 volt outlet

- Flat , beveled, angled working tip

- 21 watts, generates 600ºC of heat

- Tip placed flat against facial aspect of bracket for 6-8 secs

- Patient indicates first feel of warmth- bracket removed with flat beaked

plier

•• Advantages-

Safe

Can be used for both metal & ceramic brackets

No pulpal reactions

RESIDUAL ADHESIVE REMOVAL-

Difficult- color similarity between adhesive & tooth.

Abrasive wear minimal

Remnants gets discolored over period of time

•• MMeetthhooddss ooff rreemmoovvaall-- 1. Scrape with supersharp band/band removing plier/

scaler

- Fast & more useful on curved teeth

- Less use on flat anteriors

- Creates scratches

•• 2. Suitable bur with contrangle

- Dome shaped tungstun carbide

- 30,000 rpm – rapid removal

- Light painting movements

- Water cooling is not recommended as it lessen contrast

•• CChhaarraacctteerrssttiiccss ooff NNoorrmmaall eennaammeell –– 1. Perikymata – transverse, wavelike grooves, parallel to each other which considered as

external manifestation of incremental lines of retzius.

2. Open enamel prism ends appear as small holes

Ridges get worn off- scratched pattern

•• As per Mannerberg-

At 8 yrs- 1/3 – 2/3 surface

At 13 yrs- reduced to 70-80%

At 18 yrs- 25-50% ridges remains

Normal wear- 0-2µm/year

•• EEnnaammeell cchhaarraacctteerrssttiiccss aafftteerr ddeebboonnddiinngg-- Zachrisson & Artun in 1979 – Enamel surface index which is based on

Scanning electron microscopy

Different instruments for debonding

•• Score 4 - diamond instruments

Not acceptable

Coarse scratches

Marred appearance

•• Score 3 - medium sand paper disks & green rubber wheel

Similar coarse appearance

•• Score 2 – fine sand paper disks

Marked deeper scratches

Surface resembles adult tooth

•• Score 1 – plain cut & spiral fluted TC bur

At 25,000 rpm satisfactory appearane

Score 0 –

None of instruments kept perikymata intact

•• Clinical implication-

No instrument left surface intact

TC spiral fluted bur- finest scratch pattern & has ability to reach difficult areas- pits,

fissures

Lingual surfaces - Oval TC bur

•• Ultrasonic scaler- alternative to burs

- Patient comfort

- Water coolant results in poor contrast

- Slow

•• AAmmoouunntt ooff eennaammeell lloosstt iinn ddeebboonnddiinngg-- Based on -

Instrument used for prophylaxis

Method of debonding

Type of adhesive

•• Instrument used for prophylaxis –

Bristle brush for 10-15 secs- abrades 10µm

Rubber cup- abrades 5µm

Brawn & Way- 26µm loss as a result of prophylaxis

•• Type of adhesive-

Filled resin – clean up with rotary instruments

enamel loss- 10-25µm

Unfilled resin – clean up hand instruments

enamel loss- 5-8µm

•• Pus & Way- high speed bur & green rubber wheel removes 20µm & low speed tungstun

carbide bur- 10µm

Van Waes et al- average enamel loss of 7.4µm with tungstun carbide bur

•• EEnnaammeell TTeeaarroouuttss--

Brobakken & Zachrisson- suggested that enamel tearouts are localized

& are seen specially with filled resins

-Comparison between macro(10-30µm) & micro(0.20-0.30)

- Size of hole after etching of prism core is 3-5µm so small filler

particles penetrates etched enamel

- During debonding – small fillers reinforce adhesive tags

Macrofillers forms natural breakpoint at enamel-adhesive

interface

Unfilled resins- no breakpoint

Ceramic brackets- chemical retention – more damage

•• Clinical implications -

To use brackets that have mechanical retention

Avoid scraping of adhesive remnants with hand instruments

•• EEnnaammeell ccrraacckkss-- - They are Split lines which are often overlooked

- Fiber optic transillumination is used to view them

- Sharp sound on debonding – creation of crack

•• Zachrisson et al –Studied 3000 teeth in 135 adolescents

using fiberoptic light occurrence of cracks in debonded,

debanded & untreated teeth

Findings are-

Vertical cracks common- >50%

Few oblique & horizontal cracks

No significant difference in 3 groups in relation to prevalence & relation of cracks

Most notable cracks – maxillary centrals & canine

•• Clinical implications -

Several distinct cracks after debonding on maxillary centrals & canines

Cracks in horizontal direction- debonding techniques needs improvement

Pretreatment examination of cracks if pronounced cracks are present.

•• AAddhheessiivvee rreemmnnaanntt wweeaarr--

Remain undetected due to colour

Abrasion depends on – size, type & amount of reinforced filler

Small size- abrade easily

•• Study by Brabakken & Zachrisson-

Degree of abrasion was minimal

Diacrylate with macrofiller & other resin with submicrometer sized particles

Debonding – adhesive was left purposely & abrasion over 12 months was studied

Very thin film of residual adhesive showed reduction.

•• Study by Gwinnet & Ceen-

Unfilled sealant begin to wear & did not showed plaque accumalation

Filled- did not wear

•• AAddhheessiivvee RReemmnnaanntt IInnddeexx-- Given by Artun & Bergland

1. All composite remains on tooth surface along with impression of bracket

2. > 90% on tooth surface

3. <10% but >90% on tooth surface

4. <10% on tooth surface

5. no composite on tooth surface

•• WWhhiittee ssppoott//RReevveerrssaall ooff ddeeccaallcciiffiiccaattiioonn --

Areas of demineralization of varying extent

Gorelick et al – in multibanded technique 50%

developed increase in white spots

Highest incidence- maxillary laterals

•• PPrreevveennttiioonn --

Daily rinsing with dil.0.05% NaF & regular use of F

dentifrice

Apply f varnish/ titanium tetrafluoride agent in caries susceptible areas

Hollender & Koch – reversal of white spot on labial surface after daily tooth brushing

with 0.22% NaF paste

Fehr et al – reversal of white spot along gingival margins after rinsing with 0.2% NaF for

2-4 mins

•• Recommendations –

Daily/ twice daily application of weak (0.05%) F solution for several months

Good oral hygiene

If strong solution is used then it causes precipitation of ca phosphate which blocks

pores & limits remineralization.

•• MMiiccrrooaabbrraassiioonn --

Removes superficial opacities

Eliminate enamel stains with minimal enamel loss

Procedure-

Abrasive gel – 18% Hcl, fine powdered pumice & glycerin

Isolate gingiva with rubber dam/block out resin

Apply gel with electric toothbrush for 3-5mins ( smaller tip)

Rinse for 1 min

Can be repeated monthly 2-3 times

Removes- white spots, streaks, brown-yellow discoloration

ELECTROTHERMAL BONDING-

- Given by Voster in 1979

- Acceleration of the setting by selective application of heat to brackets

•• HHeeaatt -- rreessiissttaannccee ooff oorrtthhooddoonnttiicc bbrraacckkeett ttoo aa llooww vvoollttaaggee

ddiirreecctt ccuurrrreenntt

•• ooff eelleeccttrriicciittyy ppaasssseedd tthhrroouugghh iitt bbyy mmeeaannss ooff aa ssppeecciiaallllyy ddeessiiggnneedd

ttwweeeezzeerr..

Based on Arrehenius equation-

For every 18-28ºF rise in temp, speed of chemical reaction doubles & vice versa

Temp at bracket –tooth interface is 45.9-50.2ºC at 5 amps or 84.3-98.5ºC at 7.5 amps.

Pulp- 2-3 & 5-6ºC

Advantages –

1. Several attachments can be done with one mix composite.

2. Setting can be accurately controlled.

3. Bracket may be accurately positioned.

4. Bond achieved is strong due to less disturbance during polymerization.

5. No pulpal reaction

6. Clinician can control current level, duration of current flow & no of pulses

7. Can be used with both light & chemically cured

8. Setting occurs in 3-6secs

Influence on enamel by different debonding techniques

Enamel Surface Index - Zachrisson and Artun (1979-AJO

0 – Perfect surface - none

1 – Satisfactory – TC burs – 25,000rpm

2 – Acceptable – fine sandpaper

3 – Imperfect – medium sandpaper

4 - Unacceptable - diamond

Amount of enamel lost in debonding The amt is related to several factors-

An initial prophylaxis with bristle brush for 10-15 sec abrade as much as 10µ.

Whereas, with rubber cups only 5µ.

Cleanup of unfilled resin with hand only results in a loss of 5-8µ.

• Removal of filled resin requires rotary inst, loss may then be 10-25µ.

• High speed bur and green rubber wheel removes appro. 20µ.

• But with careful use of TC bur,enamel loss was only 7.5µ.

Adhesive remnant index (ARI)

-Artun • Used to evaluate the amount of adhesive left on the tooth after debonding.

Score 0 : No adhesive left on the tooth

Score 1 : Less than half of the adhesive left

Score 2 : More than half of the adhesive left

Score 3 : All adhesive left on the tooth, with

distinct impression of the bracket mesh

CRYSTAL BONDING SYSTEM OR CRYSTAL GROWTH INTERLOKING

SYSTEM-

According Kartz & Smith, a new method of bonding that involves crystal growth on

enamel surface described. This system consists of a polyacrylic acid treatment liquid

containing a sulfate component that reacts with needle shaped crystals. These crystals

grow in spherulite manner. The crystals building on enamel surface serves as an

additional retentive mechanism for resin that bonds the orthodontic attachment to teeth.

In this extensive procedure the bond does not rely on extensive penetration into enamel &

micromechanical interlocking is created at enamel surface.

Using this method-

1. There is minimal effect on outer fluoride rich enamel layer.

2. Enamel surface is not significantly damaged.

3. Few, if any resin tags are left behind.

4. Adequate bond strength for clinical practice is achieved.

5. Debonding & clean up are much easier with minimal iatrogenic damage.

6. Crystal interface offers possibility of incorporation of fluoride or other antiplaque

agents in future to anticariogenic Action.

M.L.Jones & K.A.Pizarro BJO 1994

Conducted a study using 4 crystal growing solutions

50% polyacrylic acid + conc.sulphuric acid

••

Solution applied- calcium sulphate dihydrate

Pot. Sulphate crystals were longest

Lithium sulphate – highest shear bond strength- 80%

•• Advantages-

1. There is minimal effect on outer fluoride rich enamel layer.

2. Enamel surface is not significantly damaged.

3. Few, if any resin tags are left behind.

4. Adequate bond strength for clinical practice is achieved.

5. Debonding & clean up are much easier with minimal iatrogenic damage.

6.Crystal interface offers possibility of incorporation of fluoride or other antiplaque

agents in future to anticariogenic action.

Polyacrylic

acid

Sulphates

of Lithium

Sulphates of

potassium

Sulphates of

Magnesium

•• AADDHHEESSIIOONN PPRROOMMOOTTEERRSS-- George Newmann et al AJO 1995

Various adhesion promoters are-

1. Sandblasting -90µm aluminum oxide

2. Sandblasting + silane (Bondpor)

3. Rocatec- sandblast with 110µm of corundum, glass layer deposited on bracket base,

silane coupler

4. Silicoat- sandblast with 250µm of corundum, 0.1µm

coating of flexible ceramic.Treat with silane coupler,

opaque layer cured

••

5. Megabond Bowens promoter- 3 parts

M1- NTG-GMA - Magnesium salt of N- Tolyglycine- glycidyl methacrylate in

acetone.

M2- PMGDM – pyromellitic glycerol dimethacrylate in acetone.

M3 – Mono & difunctional monomers & oligomers & activators in acetone

•• Procedure-

- Etch tooth surface & air dry

- 2 drops of M1 & M2 are mixed for 5secs & 3 coats are applied on tooth surface – glossy

- 2/3 drops of M2 & M3 are mixed & 2 coats are applied on metal mesh

- Bond bracket & allow to dry for 5secs

Indications-

Hypocalcified teeth

Fluorotic teeth

Bond strength- 9-13.3 MPa

•• SSMMAARRTTBBOONNDD-- - In 1991- ethyl cyanoacrylate introduced

- Higher tensile strength than composites

- Used as superglue- automobiles, light aircrafts

- In medicine- fracture fixation, GTR, cardiac surgery, skin sutures

- Smartbond – ethyl cyanoacrylate + silica gel

Polymerization starts in moisture & pressure

If used on polycarbonate brackets- pretreated with water

When it polymerize in presence of water white acrylic like

Powder is formed & process is called as ‘Blooming’

Surface should be bonded closely, If not results in formation of voids

Brackets with deep mesh/undercuts- decreased bond strength

No residual monomer reacts later- no water absorption- no discoloration

•• Advantages-

Bonds to wet surface

Moisture control

Use with metal, plastic & ceramic brackets

Bonds to composite & porcelain materials

••

•• FFIIBBEERR--RREEIINNFFOORRCCEEDD CCOOMMPPOOSSIITTEESS ((FFRRCC))

Fiber-reinforced composites are sometimes referred to as ‗polymers‘.

Composed of long chain-like molecules consisting of many simple repeating units.

Manmade polymers are generally called ‗synthetic resins‘ or simply ‗resins‘.

•• Classification - according to the effect of heat on their properties.

1.Thermoplastics - soften with heating and eventually melt, hardening again with

cooling.

Eg-nylon, polypropylene

Can be reinforced with short, chopped fibers such as glass

•• 2. Thermosetting materials, or ‗thermosets‘, are formed from a chemical reaction

Undergo a non-reversible chemical reaction to form a hard, infusible product.

Eg - phenolic resins,polyester and epoxy

Once cured, thermosets will not become liquid again if heated

•• Most polyester resins are viscous, pale coloured liquids consisting of a solution of

polyester in a monomer, which is usually styrene.

Styrene -50% -reduces viscosity

Cross-linking the molecular chains of the polyester,without the evolution of any by-

products.

These resins can therefore be moulded without the use of pressure and are called

‗contact‘ or ‗low pressure‘ resins.

Polyester resins have a limited storage life as they will set or ‗gel‘ on their own over

a long period of time.

•• Advantages -

Non-corrosiveness

Translucency

Good bonding properties

Ease of repair

Potential for chair side and laboratory fabrication

••

Long FRC – bars which joins teeth to form anchorage/ active splints

New partially polymerized continous long chain FRC - PRE-PEGS

Superior properties with good coupling, easily formed, flexible

Uses –

Retention

Anchorage

Active tooth movement

•• RRIIBBBBOONNDD --

Reinforced polyethylene fiber – Ribbond

Ultrahigh molecular weight

Treated with cold gas plasma to enhance adhesion to synthetic restorative materials

Special fiber network- efficient transfer of stresses

Translucent –excellent aesthetic

Ease of adaptation to dental contours

Ease of bonding

Easy & fast technique – one appointment

Acceptable strength

Good clinical longetivity

Thin – volume of appliance reduced

Easy repair

•• Uses-

Periodontal splints

Endodontic Posts & cores

Treat cracked tooth syndrome

FPD

Trauma stablization

•• 1. Fixed retention-

Etching with 36% phosphoric acid for 30 secs

Ribbond of required size is cut & saturated with bonding agent

Flowable composite applied on tooth surface & Ribbond

placed

••

2. fixed space maintainer

Dentin primer applied on tooth surface

Ribbond segment saturated & bonded with flowable composite

••

3. Temporary esthetic appliance-

••

4. Post traumatic stabilization splint

••

FRC in Lingual Orthodontics-

Anchorage reinforcement-

2 FRC bars – labial surface from I PM to I M

Procedure -

Buccal surface microetched then acid etched

Bonding agent applied over tooth surface & cured

••

Thin layer of flowable composite applied on enamel surface & FRC positioned &

pressed against composite.

Light cure for 5 secs

Each fiber layer covered with layer of flowable composite & Light cure for 40 secs

•• SSPPLLIINNTT --

Kelvin fibers- weak in compression

S-glass fibers – SPLINT

Matrix- light curable thermoset BisGMA

Modulus of elasticity – 70% greater

Yield strength- 6 times greater

Resilience- 24 times greater

•• 1. Any attachments like brackets, hooks can be directly

bonded to FRC

FRC bar can be easily removed by peeling action

••

•• 2. Intermaxillary elastics are applied without bands/wires eliminating bracket-wire play

••

••

••

••

••

•• 3. Vertical elastics to close open bite when incisor extrusion indicated

••

4. Posterior & anterior anchor units with bonded attachments

for space closure

••

5. - T- loop used for space closure with bonded ceramic bracket on anterior FRC

- Chain elastics for space closure

••

6. Uprighting second molar with full arch FRC-

With straight archwire segment

With T-loop

••

Repair of FRC bars – bond replacement connector

•• BBoonnddiinngg ttoo FFlluuoorroosseedd EEnnaammeell-- - Frequent bracket failure at compromised enamel interface in fluorosed teeth due to

outer hypermineralized & acid resistant layer which prevents proper etching of enamel.

- Fluorosed enamel manifests as defects in subsurface enamel ranges from white to

brown, pits & irregular opaque lines, striations & cloudy areas

- It is seen tnat 37% phosphoric acid- decreased irregularty

Ways to increases retention are-

1. Microabrasion along with sandblasting – improves retention- aluminum oxide/silicon

carbide

2. Adhesion promoter- James Noble et al Angle Orthod 2008

Primer- aq soln of HEMA & polyalkenoic acid- resin layer to flow on etched surface

••

Adhesive- BisGMA & HEMA resin combined with amines

Scotchbond multipurpose plus primer- apply & gently air dry for 5 secs

Light cure

Only 1 bond failure in 9 months

3. Etching time – study by Peter Ng‘ang‘a et al

40% phosphoric acid for 60 secs- better etching pattern

Bond strength- 7.8N/mm2 for fluorotic teeth

8.6N/mm2 for nonfluorotic

teeth

Scotchbond MP (Multi-Purpose) - can bond to amalgam or porcelain that has been

microetched with 40-micron aluminum oxide before acid etching.

Filled composite Concise to visible-light-cured composites for bonding, because

fluorosed enamel seems to diffract visible light and prevent complete curing

••

1. Microetch each fluorosed tooth

2. Etch for 20 seconds with 37% phosphoric acid gel

3. Apply Scotchbond MP, and light-cure it for 10 seconds per tooth

4. Apply Concise to each bracket, then position the bracket on the tooth

••

Light cured composite veneers for fluorosed teeth. JCO 2006

Gp A – surface cleaned with plain non-fluoridated pumice & water

Gp B- Above+ remove 1-2mm of enamel with carbide drill

Gp C- Above + porcelain veneers

Bond failure- A- 74%

B- 25.9%

C- 1.7%

VARIOUS STUDIES -

Direct bonding to porcelain AJO 1995

Study done by Vanessa Barbosa, Marco Almedia, Orlando Chevitarese

Hydrofluoric acid – better retention to porcelain

Mucosal contact- erythema, burning with loss of tissue, intense pain for several days

APF- other alternate

•• Bond strength between composites & RMGI as a adhesive AJO 2004

Study done by Andrew Summer et al.

RMGI- Fuji ortho LL & composite- concise

Results-

Decreased shear bond strength with RMGI

Predominant failure at enamel adhesive interface

Weak bond- easy clean up

SEM – less rough & porous surface after 10% polyacrylic acid etching

Effect of blood contamination on shear bond strength of conventional &

hydrophillic primer AJO 2004

Study done by Marier F. Sfondrini et al

Conventional primer- Transbond XT

Hydrophillic primer - Transbond MIP

Results-

Non-contaminated surface- highest bond strength

Contaminated surface- greater but not clinically significant strength

••

Bond strength with self etching Primer AJO 2004

Study done by Helen Grubisa.

SEP‘s – ph of 1

Shear bond strength is less than achieved with 37% phosphoric acid

••

Bond strength of light cured GI & chemically cured GI AJO 1992

Study done by Anne M. Compton et al.

Light cured - 80% of strength in 20 secs

Chemically cured- 80% of strength in15 mins

Light cured – Zionomer- 2 paste

Chemically cured- Ketac bond ( rapid setting)

Light curing – Ortholux for 20 secs

Results-

Mean bond strength of light cured GI > chemically cured at 1 hr & 24 hrs

Bond strength for both increased from 1 to 24 hrs.

•• Shear bond strength of 4 primer systems AJO 1992

Study done by Mark Neil Corril et al

Segasealant

Max cure

Scotchbond 2

Concise enamel bond

•• RReessuullttss--

Shear bond strength tested with Instron testing machine

Max cure – highest mean bond strength of 25.33N/mm2

Scotchbond 2 – lowest

•• Bond strength of 3 GI cements AJO 1990

Study by Valerier Bowser Fajen et al

Ketac cem , Fuji I, Precise

Results-

Mean force for bond failure in-

Precise- 2.43pounds

Fuji I – 6.87

Ketac cem – 11.3

Keatc cem- highest bond strength of 3.91MPA

It is a water hardened soln with polyacrylic acid

Freeze dried

Provides more consistent mix

Minimal material between bracket & tooth- better adhesion

•• Clinical evaluation of Glass polyalkenoate cement for direct bonding AJO

1992

Study done by John Fricker

Fuji I & system 1+

Bracket failure recorded at 3 month intervals

Results-

After 12 months- 12 failure with GIC & 3 with composite

Majority failure in 6 months

Bond strength for GI – 32kg/mm2

Bond strength for composite– 103kg/mm2

F release in GIC – prevents demineralizaion

Povie et al- pretreat with polyacrylic acid to increase bond strength

Cook & Youngston- no difference

•• Shear bond strength of s.steel & ceramic brackets with chemically & light cured

composites AJO 1990

Study done by V.P. Joseph, Rossouw.

Chemical- Concise ( macrofilled)

Light – Heliosit (microfilled)

Results-

Most fractures with chemically cured & ceramic brackets

Creamic- high bond strength than s.steel

Ceramic bracket fracture- 6.66%

•• Effect of phosphoric acid concentration & etch duration on enemel depth of etch

AJO 1990

Study done by L.R. Legler, D.H. Retiet, E.L. Bradley.

9 subgroups-

37%- for 60,30,15 secs

15% - for 60,30,15 secs

5% - for 60,30,15 secs

•• RReessuullttss-- Max depth etch- 27.1µm- 37% for 60 secs

Min depth etch- 3.5µm- 5% for 15 secs

Amount of enamel dissolved increases with increase in acid conc upto 27%.

Above 27% it decreases – formation of MCPM

•• Effect of phosphoric acid concentration on shear bond strength AJO 1995

Study done by Wasundhara Bhad, Pushpa Hazarey

5 & 37% phosphoric acid

5% - minimal enamel loss than 37%

No difference in shear bond strength

Even 5% can be used

•• Effect of phosphoric acid concentration on shear bond strength AJO 1995

Study done by Wolfgang Carstensen

Phosphoric acid concentration in 37,5,2%

Results-

Less conc- less shear bond strength & less adhesive for removal after debonding.

•• Shear bond strength of SEP to fluorosed teeth Journal of Dentistry 2005

Thick resin tags of 3.5µm with conventional etching

SEP - 1µm

Better etching with conventional acid etching.

•• Debonding techniques on enamel surface AJO 1995

Study done by K. Zarrinnia, M.J.Kehoe.

Results-

Better bracket removal with bracket removal plier

Bulk resin removal with- 12 fluted tungstun carbide bur at 20,000 rpm

Finish- graded, medium/fine superfine sof-lex disks at 10,000rpm with air cooling

Final finish- rubber cup with zircate powder

•• Role of sandblasting on retention of metallic brackets with GIC BJO 1993

Ketac cem & Right

Results-

Sandblasting of bracket base for 3secs at 10mm distance

Produced good micro-roughned surface

Increased mean bond strength by 22%

Mean survival time increased

•• Remnant amount & clean for 3 adhesives after debracketing AJO 2002

Study done by Valerie David et al.

Transbond, Fuji Ortho LC, Advance

Results-

Remnants from GI were heavier than composite

Remnants of Advance- larger

Bonded to acid etched teeth took 1-11/2 longer to clean up

•• Enamel surface after orthodontic Debonding Angle Orthod 1995

Study done by Phillip Cambell

Tungstun carbide bur & abrasive disks

30 fluted tungstun carbide bur most efficient with least amount of scarring

Steps-

Bulk removal with 30 fluted tungstun carbide bur

Enhance cups & points to remove gross scarring

Water slurry of fine pumice to obtain smooth surface

Final finish with brown & green cups

•• Shear bond strength of resin reinforced GIC- AJO 1999

Study done by Chun Chung, Patrick T.C., Francis K.M.

Concise & Fuji Ortho LC (RMGI)

Results-

Concise strongest shear bond strength

Fuji Ortho LC- strong bond under dry condition. Site of failure between adhesive &

enamel

••

Light & chemically cured- degree of cure/ monomer leaching & cytotoxicity

AJO 2005

Study done by Christiana Gioka et al

Chemical- Rely-a bond

VLC- Reliance

Results-

Degree of cure of both do not differ

Amount of monomer leached is same

No cytotoxic effects on PDL

•• Antimicrobial properties of an adhesive with Cetylpyridinium Chloride AJO

2006

Study done by Tahani Musallam et al.

S.Mutans- risk of caries

CPC – antiplaque

Added to filled photoactivated adhesive- Transbond XT

Conc – 0%, 2.5%, 5%, 10%

Results-

Bacterial inhibition with CPC

2.5% best antimicrobial without affecting DTS

Initial more release upto 15 days, reaches plateau upto 60 days

•• Effect of Adhesion promoters on shear bond strength AJO 2006

Study done by Ascension Vincente et al.

Orthosolo, All-Bond 2, Enhance LC

Contains N- Tolyglycine- glycidyl methacrylate & hydrophilic resins

Adhesives – Transbond XT, Light bond

Results-

High bond strength – light bond+Enhance LC

Tranbond XT – best bond strength with Orthosolo

Lightbond left less adhesive

None of adhesion promoters increased adhesive remaining on tooth surface

•• Shear bond strength of 3 Self etching adhesives AJO 2006

Study done by Neslihan et al.

Adaper prompt L-Pop

Clearfil protect bond ( F & antimicrobial)

Transbond Plus SEP ( F)

Results-

Clearfil protect bond- max shear bond strength

Adaper- adequate

None produced enamel fracture during debonding

•• In vivo- Effect of fluoridated antiplaque dentifrice on enamel demineralization

AJO 2006

F paste - Tandy

F antiplaque paste – Triclosan/zinc/Pyrophosphate

Antiplaque –superior, less demineralization

•• Assessment of long term failure of 2 SEP’s AJO 2005

Study done by Nikolaos Pandis et al.

Transbond plus, One step

Failure rates recorded after 14 months

Results-

Transbond plus – 0.94%

One step – 8.10%

More in mandibular arch

•• Plasma curing light & Conventional halogen curing light AJO 2005

Study done by A.P. Pettermerides, M.Sheriff, A.J.Ireland.

Transbond XT,Fuji Ortho LC

Plasma arc light- 3 secs

Halogen light- 20 secs

Results-

Transbond XT- failure rate 3.41% with both lights

Fuji Ortho LC - 11.4% with halogen & 10.2% with plasma

No difference in bond failure but time can be saved with plasma light.

•• Porcelain surface treatment by laser for bracket porcelain bonding AJO 2005

Study done by Tolga Akova et al.

20 secs superpulse CO2 laser irradiation provides adequate bond strength between

metal brackets & porcelain surface

Silane application after laser improves bond strength

•• Nd- YAG laser for debonding ceramic brackets AJO 2005

Study done by Kotaro Hayakawa, Chiba.

Laser – wavelength of 1060nm

Results-

High peak power at 2J more effective for debonding

Max temp on pulpal walls- 5.1ºc

Polycrystalline brackets – significant decrease in bond strength than with

monocrystalline

••

Effect of Argon laser curing on shear bond strength when bonded with light cured

GIC AJO 2005

Study done by Glaucco Serra et al.

Argon laser for 5 secs, halogen light for 40 secs.

Results-

Bond strength – equivalent in both groups but reduces cure time by 87.5%

Argon leaves more adhesive on tooth surface

•• Light curing time reduction with new high power halogen lamp AJO 2005

Study done by Christine B.S. et al

Conventional halogen- long curing time

Low priced, high power halogen light –NEW (Swiss master light)

Cost effective solution to reduce curing time

Recommended time- 6 secs & with caution 3 secs.

•• Effect of bleaching on shear bond strength AJO 2005

Study done by Samir Bishara et al.

At home bleaching- opalescence bleaching agent (10% carbamide peroxide)

In office bleaching- Zoom (25% hydrogen peroxide

Bonded with composite adhesive

Bleaching do not affect shear bond strength

•• Bonding impacted teeth without moisture contamination JCO 2005

Study done by Sandhya Jain

Etch tooth surface

Clean & dry surface by wiping enamel with alcohol swab

Water irrigation not needed

•• New Self Etching, Light cured Bonding system JCO 2005

Study done by Alberto Armenio

Brajen unibond - average bond strength of 22MPa

Fluoride release

Viscosity prevents bracket flotation

Good resistance to discoloration

•• Modified amalgam plugger for Etchant application JCO 2005

Study done by John Baccelli

Std amalgam plugger modified with crosshatch file

Etchant can adhere to surface

Carefully scraping against enamel surface removes all debris & pellicle

••

CONCLUSION-

Simplicity of bonding can be misleading . Success in bonding requires understanding of

and adherence to accepted orthodontic and preventive dentistry principles.

It has taken half a century for orthodontic bonding procedures to evolve from acrylic to

chemically cured (2-phase, then 1) to light-cured to dual-cured (chemical light) to

moisture-active

Even the device that threatens to replace conventional brackets altogether—the

aligner—relies on bonded buttons, so it appears that some form of bonding will be with

us for a while.

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