DHYG 113

RESTORATIVE DENTISTRY I

Dental Cements:Liners, Bases, and Temporary Restoration

Materials

Objectives

Describe the purpose and use of: Calcium hydroxide Zinc phosphate Glass ionomer ZOE Temporary cement

Recall approximate setting times for eachDemonstrate proper mixing techniques (lab

activity)

Terminology

BaseLinerLuting agentObtundantExothermic

Dental cementPulp protectionCavity sealerDentin bonding agentVarnish

Use of Dental Cements

Luting agent = cementPulp protection = liner or baseTemporary restorationCaries controlCavity sealer = varnishDentin bonding agent

Chemistry of Dental Cements

Dental cements are typically a powder/liquid system

The liquid is an acid The powder is a base Powder must be insoluble in oral fluids but

reactive with acid

Composition of powder

Two materials used to make powders for dental cements: Zinc oxide Powdered glass

Zinc oxide

The only insoluble, nontoxic, reactive oxide or hydroxide to react w/an acid

Common additives are aluminum oxide and magnesium oxide

Has some antibacterial effects Reactivity is controlled by manufacturing

process

Powdered Glass

The chemical form- silicon oxide - is very un-reactive When oxides of sodium, calcium and potassium are

added in sufficient quantities, the glass will react with strong acid.

Made of small translucent glass particlesContains fluoride to reduce melting temp,

improve flow of molten glass, and gives cement ability to release fluoride.

Reactivity is determined by composition of glass.

Dental cement liquids

Composition or strength of acid determines reactivity of the cement liquid.

Composition is controlled by the manufacturer

Liquids used in dental cements include: Eugenol Phosphoric acid Polyacrylic acid

Eugenol

Organic liquid- weak acid Major component of oil of cloves

Derived from phenol Antibacterial Obtundant -- reduces irritation to pulp

Inhibits free radical polymerization Inhibits setting of composite restorative

materials Ethoxybenzoic acid (organic liquid) added to

formulate cements.

Phosphoric acid

Used as 2/3 acid and 1/3 water

Very acidic and irritating to tissue

Amount of water present affects reactivity of liquid by affecting ionization.

Different levels of humidity affect it

Polyacrylic acid

Aqueous solutions 30-50% polyacrylic acid by weight Very viscous liquid

Dispensing Must be very accurate – independent drops important Do not dispense liquid until ready to mix cement Do not store in refrigerator

Carboxyl groups bond to calcium in tooth Water hardening cements

Zinc oxide or glass powder mixed with anhydrous polyacrylic acid

Combined powder mixed with companion liquid (mostly water)

Polyacrylic acid dissolves in water then reacts with ZO or glass

Dental cements

Combine one of the three cement liquids… Eugenol Phosphoric acid Polyacrylic acid

With one of the two powders Zinc oxide powder Glass powder

Most commonly used

Calcium hydroxide Used as a base/liner under restorations in deep preps Used as for pulp capping

Zinc phosphate Used to lute restorations, ortho bands – also used as a

base material under restorations Zinc oxide-eugenol (ZOE)

Chalky and white, used when not concerned with aesthetics.

Obtundant – kind to pulp Glass ionomer

Used for thermal insulation under restorations, luting agent

Zinc Phosphate Cement

A. Use1. Lute inlays, crowns, bridges, ortho brackets, etc.

2. Also used as a base material under restorations.B. Related Information

When the powder and liquid are mixed, an exothermic (heat-releasing) reaction occurs. To dissipate the heat of this reaction:1. A large portion of the glass slab must be used during

mixing.2. The powder must be added in small increments.3. The mixing time must extend to 1.5 to 2 minutes.

Zinc Phosphate Mixing

Set up time is 5-9 min.

Add powder to liquid in small increments

Zinc phosphate cement/base material

Measure the powder Measure the liquid

“fluff powder”Fill scoop; do not

packDivide powder into

several small increments

Hold bottle vertically

Dispense correct # of drops of liquid

Mixing for luting consistency

Add powder in small increments

Should stretch ½ inch

Glass ionomer

A. Use 1. Base, luting agent, restorative material 2. Thermal insulating material in deep

prepsB. Characteristics

1. High strength, low solubility 2. Kind to pulp 3. Chemically bond to tooth structure; release

fluoride

C. Dispensing systems 1. Powder/liquid systems 2. Disposable capsules – mixed in

amalgamator 3. Paste/paste systems

Higher power/liquid ratio

Mix

Measured in same manner

Setting time is ~ 7 min.

Mixing time between 15-30 seconds

Add about ½ the powder at first, then the rest

Mix is determined by ratio set by manufacturer, not “feel”

Clean up with soap and water before cement sets

Mixing for base or luting

Liners

Used to protect pulp from chemical irritation Stimulate dentin formation or release fluoride Considerations:

Do not provide thermal insulation (too thin) Too weak to support restorative materials or

condensation forces (dental amalgam) Once used under composites to prevent

irritation-not much anymore

Calcium hydroxide liners and bases

Promote the formation of secondary dentin

Comes as paste/paste system One is calcium hydroxide,

one is salicylate. Titanium oxide is an added

filter Setting reaction is

accelerated by water Sets very quickly on moist

dentin

Dycal (Calcium Hydroxide)

A. Use

Calcium hydroxide may be used in pulp capping and as a base/liner under other dental restorative materials in deep preparations.

B. Protective Properties

Calcium hydroxide serves as a protective barrier between tooth tissues (dentin and pulp) and acid-containing cements and restorative materials.

C. Measuring

Dispense small, but equal, amounts on a paper mixing pad

D. Mixing

Mix thoroughly with the crook of a small, ball-pointed instrument until a uniform color is achieved

Mixing should be completed within 10 seconds.

Calcium Hydroxide, con’t

E. ApplicationUse the tip of the ball-pointed instrument to place the mixed material on the floor of the cavity preparation. Avoid placing the mixed material on walls and margins, and avoid placing it in large amounts.

F. SettingThe setting time of mixed calcium hydroxide is 2 to 3 minutes on the mixing pad at normal room temperature.The setting time for a pulp capping or base/liner will be greatly decreased in the mouth because of the moisture of dentin.

Varnishes Copal Varnish

Resins dissolved in a solvent

Painted onto entire cavity preparation

Solvent evaporates, leaving thin resin layer

Used under amalgamsNOT used with

composites (interferes with adhesion)

Cavity Sealer

Cements as Pulp Protectors

Use Protective properties

One of the least irritating dental materials

1. Temporary cement 2. Insulating base

under permanent

restorations 3. Provide obtundant

filling for sensitive

tooth

Thermal traumaSedative, soothing

effect on dental pulp

Zinc-oxide eugenol (ZOE)

Powder Liquid

Use scoop provided by manufacturer

Place 1 scoop of powder onto glass slab or paper pad

Dispense 2 drops of eugenol by holding dropper perpendicular to slab/pad

Drops should not touch powder, but should be near to it

Measuring ZOE

Mixing ZOE cement

Hold spatula in “flat” positionDraw about half of powder into liquidUse small area of mixing slab/padPush powder into liquid with quick motionContinue incorporating small portions of

powderMix should be complete in 1.5 minutes Sticky consistency – use for cementing

temporary crownThick, putty-like consistency – use for base or

temporary filling

Reinforced ZOE IRM

Stronger, less soluble than ZOE

Temp restorationsIntermediate basesAdditives include:

Alumina Resins

Intermediate Restorative Material

Mixing IRM

Measure 2 scoops of powder onto glass slab/paper pad

Place 1 drop of liquid onto slab/padHold spatula in “flat” position Draw about ½ of powder into the liquidUse small mixing area; spatulate with quick

motionContinue incorporating powder into the mix by

pressing powder into the mixMix must be thick, putty-likeComplete mix in about 1.5 minutes

Application

Gather IRM into one mass on the mixing slab/pad

May be rolled with fingers to form a ballUse flat-bladed instrument to carry portions

of material to the cavity prepMay dip instrument into excess powder to

prevent stickingSets up in about 3 – 3.5 minutesGlass slab may be cleaned with alcohol wipe

Temp Bond Properties

High flow to permit ease of seating restoration

Strong enough to withstand forces of chewing

Allow restoration to be easily removed

Temporary Cement

Measuring Mixing

Two tubesCatalystBase

Squeeze equal lengths of material onto pad

Mix together in 30 sec.Homogenous colorShould form a string

when stretched from mixing pad

Apply thin layer to restoration, sets in 2 min.

Temporary Cement

Temporary Crown

Temporary crown Crown prep leaves an exposed tooth which can

be painful. Temp crowns usually made of plastics and formed

in mouth. Also made of metal or plastic formed outside of

mouth. Temporary cement used to apply temp crown. Placed at crown prep appointment, lasts few days

or weeks.

How Temporary Restorations are used:

Remove all or part or decay from tooth, then allow pulp to heal before determining treatment.

Patients with many carious lesions (more than 10) to make the oral environment noncariogenic

A temporary filling on an “open” tooth in endodontic therapy.

Exposure controls/personal protection with Eugenol

Respiratory protection: In well ventilated areas respiratory protection is not normally required. In confined, poorly ventilated area respiratory protection may be necessary

Hand protection: Wear impervious gloves

Eye protection: Wear eye protection. e.g. Safety glasses/goggles

What you need to know to stay safe

As with most dental materials …read the label and look for hazardous or toxic products in the materials

Be aware of potential for allergic reactions Follow OHSA exposure limits

Generic and brand names of base materials

Bases: Shofu base cement (Shofu) Ketac bond capsules (ESPC) Zinc Phosphate (Mizzy) ZOE B&T (Caulk)- Eugenol-containing material

Generic and brand name Liners

Liners:Heavy filled glass ionomers: Fuji IX GP in capsule or powder/liquid form. ESPE: provisional filler, larger non-stress-bearing

build ups SHOFU

Light cured resin modified glass ionomer Vitre-bond (3M) Fuji Lining Cement LC (G-C)

Group Activity

Divide up into 5 groups – about 4 to a group

Discuss the case study your group is given, and answer thesequestions:

1. What material will you select for your patient?2. Why did you select that material?3. How will you mix/apply the material?4. How long would you expect the material to last?