dental liners bases and varnishes

DENTAL LINERS, BASES AND VARNISHESDepartment of Conservative dentistry, endodontics and esthetics

By dr. siddharth suthar part I endo PG

Why do we need them?

Pulp protection

THERMALCHEMICAL

MECHANICAL

BIOLOGICALELECTRICAL

Importance of remaining dentin thickness

0.5mm

1 mm

2 mm

Remaining dentin

thickness

25%

10%

Minimal or nil

Effect of toxic

substances

Some important points to consider

1. Knowledge about pulp dentin complex, its defensive mechanism as a function of the intensity and duration of irritants.

2. Clinical signs of pulpal irritation and its healing capacity

3. The irritating capabilities of the diseases affecting the tooth, operative procedures and the materials used.

Proper understanding of the nature of diffusability and the factors affecting it.

The functions of the intermediary bases.

Factors governing dentin permeability

1. Type of dentin

Calcific barrier dentin

Sclerosed dentin

Primary dentin

Secondary dentin

Tertiary dentin

Globular dentin

Granular dentin

Dead tract

dentin

• Compatibility and reactivity with dentinal constituents

• Their valencies• Degree of ionization• Molecular size• Molecular mobility• Wetting ability• Driving forces

The types and nature of penetrants depending upon

Plaque acids-penetrate quickly and extensively

Salivary ions-depends on molecular size and reaction potential

Corrosion products –readily penetrate dentin

1. The degree of mineralization of dentin2. Dentin exposed during tooth preparation3. Effective depth (dentinal bridge)4. Induced stresses5. Hydraulic pressure6. Deficient resistance and retention form7. Microleakage8. Cracks and microcracks in the dentin and

enamel9. Type of intermediary base or restorative

material10. Dessication of dentin

Why do we need liners and bases

Because the dentine is sensitive Hydrodynamic theory of pain

transmission When we cut or prepare a cavity we are

cutting fresh dentinal tubule we have to maintain a good seal

between the filling and the cavity

Ideal requirements for intermediary base materials

1. Should be capable of creating an impervious layer on cut vital dentin

2. Biocompatible3. Chemically compatible4. Should be thermal, chemical and electrical insulator.5. Should not discolour6. Should harden quickly7. Should withstand condensation forces8. Should stabilize or diminish dentin permeability.9. Should be easily manipulated10. Should impart sedative action11. Should promote repair and healing

Materials used for intermediary bases and basing

1. Zinc oxide eugenol2. Calcium hydroxide3. Zinc phosphate cement4. Polycarboxylate cement5. Varnishes and film forming resinous

materials6. Glass ionomer cements

Principles of intermediary basing

Apply all over the preparation

No therapeutic effect

R.M.- no chemical &/or

physical adhesion

Layer of the intermediary base< the

microleakage space

Are applied to change only

certain properties

are not concerned with retention and resistance form of

restoration.

But if it is not so, then…

Do not apply on margins or surrounding walls, confine to axial and pulpal walls only

Confine to deepest parts of the pulpal and/or axial walls so that restoration will be seated on two opposite areas in dentin.

Apply minimal thickness to fulfill the objectives Therapeutic bases-always weak-either carry

with reinforcing carrier or use as subbase Should be securely retained in the dentin to

avoid displacement.

Determination of effective depth

From the radiographEffective depth in the radiographEnamel thickness in the radiographActual effective depthActual enamel thickness

Using sonic probes By correlating the items recognizable in

the preoperative radiograph. E.g., sclerotic dentin, dead tract etc.

CAVITY LINER

Thin layer of cement such as calcium hydroxide suspension in an aqueous or resin carrier (after evaporation), used for protection of pulp: certain glass ionomer cements that are used as an intermediate layer between tooth structure and composite restorative material are also considered liners.

Liners are aqueous or volatile organic suspensions or solutions.

They leave a thin film and shining surface on the cavity, the thickness of this film very minimal not exceeding 0.5 mm.

Their solvents evaporate quickly, leaving behind a film residue.

Composition

Suspension of calcium hydroxide in an organic solvent such as methyl ethyl ketone or ethyl alcohol

Other liners include Type III GIC Type IV ZOE

Properties

Do not possess mechanical strength Very less thermal protection Calcium hydroxide-soluble-should not be

applied at the margins Flouride added to some liners to reduce

secondary caries

Types of liners

Solution liners Suspension liners

Indications for use Protects the pulp from chemical irritation

by its sealing ability. Stimulates the production of reparative or

secondary dentin. Compatible with all types of restorative

materials.

Calcium HydroxideCalcium Hydroxide

Application process Placed only on dentin. Placed directly over the deepest portion of

the preparation.

Calcium Hydroxide-cont’dCalcium Hydroxide-cont’d

Commercial Examples:

a. DYCAL (LD Caulk):

Catalyst Paste= 51% CH, 39.7% EthylToluene Sulfonamide, 9% ZnO, 0.3% Zn StearateBase Paste= 39% Glycol Salicylate, 45% TiO2,15% Ca Tungstate, 0.6% CHReaction= Moisture allows Ca+2 ions to dissolve and chelate

with salicylate

b. LIFE (Kerr):Catalyst Paste = CH, ...Base = 83% Methyl Salicylate Oligomers, 15% Methyl

Salicylate Polymer,...Reaction = Moisture dissolves CH and Ca+2 ions crosslink the

oligomers

c. Light Cured DYCAL

Fig. 44-1 Location for placement of calcium hydroxide.

CAVITY VARNISHA solution of natural gum, synthetic resins, or resins dissolved in a volatile solvent, such as acetone, ether or chloroform.

Indications for use* Seal the dentinal tubules. Reduce leakage around a restoration. Act as a barrier to protect the tooth from

highly acidic cements such as zinc phosphate.

* This material is contraindicated in its use under composite resins and glass ionomer restorations.

VarnishesVarnishes

Applications

Reduces microleakage around newly placed amalgam

Reduces passage of irritants into dentinal tubules

Prevents penetration of corrosion products. Can be used as surface coating over certain

restorations As a temporary protection from galvanic shock In cases where electrosurgery is to be done

adjacent to metallic restorations.

Composition

Natural gums Copal Rosin

Synthetic resins Organic solvents

Alcohol Acetone ether

Medicinal agents

Chlorbutanol Thymol Eugenol flouride

Properties

Do not possess mechanical or Thermal insulation Film thickness ranges from 2-40 microns Solubility is low- virtually insoluble in

distilled water.

Precautions

Bottle should be tightly capped immediately

Should be applied in thin consistency Excess varnish should not be left on the

margins of the restorations as it prevents proper finishing of the margin of the restorations.

Should be confined to dentin when using silicate or silicophosphate restoration.

Contraindications

Composite resins Glass ionomer When therapeutic action is expected

from the overlying cement. Eg. ZOE, calcium hydroxide.

Application process Applied with either a small disposable

applicator or a cotton pellet. Thin coating of the varnish on the walls,

floor, and margin of the cavity preparation. Air dry and reapply the varnish Air dry again to see a shiny hard surface

which is ready to receive the gold or amalgam restoration.

Varnishes-cont’dVarnishes-cont’d

Commercial Examples:

•Solvent: Film Formers:

a. Solution Liners:Copalite = Mixture Copal ResinHydroxyline = Mixture PMMA Resin, CHChembar = Chloroform PS Resin, CH,

ZnOTubilitec = Chloroform PS Resin, CH,

ZnO, F, Dithymol-I2

b. Suspension Liners:Pulpdent = Water Methyl Cellulose, CHHypocal = Water Ethyl Cellulose, CH

Fig. 44-5 Location for placement of cavity varnish.

Dental bases

Types High strength

Thermal as well as mechanical protection Eg. Zinc phosphate, polycarboxylate, glass

ionomer, and reinforced ZOE. Low strength

minimum strength and rigidityact as barrier and provide therapeutic

benefiteg. Calcium hydroxide and ZOE

Properties

Protection against chemical insults- Should serve against barrier against

irritating constituents. Ca Hydroxide and ZOE are the most effective.

Thermal properties- Thermal conductivity should be similar to

tooth structure For effective protection a minimum of 0.75

mm thickness required

Therapeutic effect Some bases are used for their therapeutic

effects. Strength-

Should withstand the forces of condensation

Withstand fracture or distortion under masticatory stresses

Also it should harden rapidly Minimum strength req- 0.5 to 1.2 MPa

•Interference with the setting reaction and properties of the permanent restorative material•Discoloration of permanent restorative material•Combination of different intermediary base materials.

Compatibility of intermediary base materials with restorative materials and techniques

Interference with setting reaction

any polymer

can depolymerize

the set polymer

discoloration

polymeric

Non polymeric

Interaction with other IBMs

Polycarboxylate , GIC,

methyl cellulose carried calcium

hydroxide

Physical and

mechanical

compatibility

Unmodified ZOE

insufficient for amalgam direct gold

and cast alloy restoration

ZOE


No effect

discoloration

Does not discolor

Thin transluscent tooth colored fillings-chalky

patch


Only in methyl

cellulose form

Organic solvents of varnishes and some

monomers of resins could dissolve it

Physical and

mechanical

compatibilityFor

amalgam- in methyl

cellulose or alkyl

salicylate chelate

For cast and direct gold-

needs protection from Zn

phosphate

Calcium hydroxide


Does not interfere

discoloration

If used in colors other than

yellow


Completely

compatible

Physical and

mechanical

compatibility

Most rigid,

durable, and

tough

Zinc phosphate


Does not interfere

discoloration

Does not discolor

Only if RM is thin

transluscent


All but ZOE & film

forming resinous material

Physical and

mechanical

compatibility

Durable enough to withstand

the manipulative forces

Polycarboxylate cement


Do not interfere

Can be dissolved by monomers

discoloration

Can form dark line around

resin restoration


Organic solvents can dissolve Ca hydroxide

Can be dissolved by

polycarboxylate and GIC

Physical and

mechanical

compatibility

Are nor affected by

manipulative forces

Film forming resinous materials

THANK YOU

1.PHILLIP’S SCIENCE OF DENTAL MATERIALS, 11TH EDITION

2.CRAIG’S RESTORATIVE DENTAL MATERIAL, 12TH EDITION

3.OPERATIVE DENTISTRY, MODERN THEORY AND PRACTICE BY M.A.MARZOUK

4.LINERS VARNISHES AND BASES, LECTURE BY 2007-2008, Stephen C. Bayne, Ann Arbor, MI 48109

5.LINERS BASES AND CEMENTS, AN IN DEPTH REVIEW, BY RANDY WEINER

6. INTERNET

dental liners bases and varnishes

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