Dental cements

الحسين العزيز عبد أحمداألردنية الصحة وزارة في تركيباتسنيه أخصائي

األردنية والتكنولوجيا العلوم جامعة في متفرغ غير محاضرAhmad Abdul Aziz Alhussien Prosthodontist at M.O.HPart time lecturer at J.U.S.TBSc , MSc, Jor. Board/ prosthodontics

Uses of dental cements

• Pulpal protection (liners, bases, varnishes)• Luting cementation (crowns, inlays, onlays

veneers)• Restorations (temporary and permanent)• Surgical dressing (e.g. periodontal surgery)

Cavity varnish

• a thin layer placed on the floor and wall of the cavity to seal dentinal tubules and minimize microleakage.

• Composition: – Natural resin (copal)– Synthetic resin dissolved in solvent such as alcohol

or chloroform.

Cavity varnish

Application method: – The varnish is applied in a thin layer– The solvent evaporates within 5 –15 seconds– A second layer is applied

The resin component protects pulp by:– Sealing dentinal tubules – Reducing microleakage– Reduce staining

Dispensing and clinical considerations• 2 bottles:– Varnish: 90% solvent, 10% resin (copal)– Solvent to dilute varnish if solvent evaporates

• The lid should be kept tightly closed• Varnishes have been largely replaced by

bonding agents since varnishes wash out quickly

Liners/low strength baseCalcium hydroxide

Clinical uses:– Liner to protect pulp– Direct and indirect pulp capping

Dispensing: • 2 paste system “Self-cured”– Base: Calcium phosphate, calcium tungstate, Zinc oxide, Glycol

salicylate– Catalyst: Calcium hydroxide, zinc oxide, zinc stearate in ethylene

toluene sulfonamide• Light cured cement: UDMA + Ca hydroxide + barium

sulfate filler and low viscosity monomer

Liners/low strength baseCalcium hydroxide

• Set cement is calcium disalicylate• Properties: – Has an alkaline Ph 9-11(stimulates dentine

formation)– Setting time: 2-7 minutes– Weak compressive strength– Thermal insulator– High solubility

Liners/low strength baseZnO/Eugenol

• Uses: – Pulpal protection in deep cavities

• Properties:– Weak– Sedative effect– Little thermal insulation

High strength base (>0.5mm)• Function:

– Insulator– Support for restoration

• Materials used:– GIC– Resin modified-GIC– Polymer reinforced ZnO/E

• Properties required for high strength bases:– High strength that develop quickly– Low thermal conductivity– Moderate elastic modulus

Luting cements

• Desirable features:– Good wettability– Good flow– Thin film thickness: 25 µm or less to fill the space

between tooth structure and restoration.

Restorations

• Permanent: cements are rarely used as restorations due to:– Low strength– Low wear resistance– High solubility

• The exception is GIC, used for class V cavities and primary teeth.

Zinc oxide eugenol temporary filling

Dental cements

ZnO cementsGlass ionomer cementsResin cementsCompomer cementsHybrid ionomersZinc phosphateZinc polycarboxylate

Zinc oxide eugenol

• Advantages:1. Wide variety of uses 2. Sedative to the pulp3. Easily manipulated

• Disadvantages1. Low strength2. High solubility3. Not used under composite resin

Zinc oxide eugenol

• Some are resin or EBA reinforced• New products are eugenol free “cavit”• Properties:– Sedative effect on pulp and antibacterial– Biocompatible .. irritant if in direct contact with pulp– Eugenol interferes with setting of resin– Moderate strength– Retention is mechanical– Water and temperature increase accelerate setting

Zinc phosphate

• Used to be used as a permanent luting agent• Composition:– Powder: zinc oxide– Liquid: phosphoric acid and water buffered by Al +

Zn to slow setting• Setting reaction: 5-9 minutes, exothermic,

controlled by incremental incorporation of powder into liquid. Cement is porous.

Zinc phosphate

• Properties– Initial acidity with pH of 4.2, becomes neutral after

48 hours.– Retentive by mechanical retention sandblasting of

crowns or inlays– Similar strength to GIC, high CS, low tensile strength.– Low solubility once set– Fast setting– Moisture adversely affects cement

Zinc phosphate

• Manipulation• Powder is dispensed and divided into 4-6

portions• Liquid is dispensed according to manufacturer• Mixing is gradual at 15 seconds intervals for

60-120seconds• Large strokes over a large area

Zinc polycarboxylate

• Uses:– High strength base– Final cementation of indirect restorations

• Composition:– Powder: zinc oxide– Liquid: polyacrylic acid

• Properties: – Lower compressive strength than other cements– Mild acidity – Higher viscosity when mixed but reasonable flow– Liquid should not be dispensed before needed, to avoid water

evaporation and viscosity – Retention is chemical and mechanical– To increase working time use a cold slab

• Manipulation: powder liquid systems, 90% of powder added first then the rest is mixed with liquid to adjust consistency

Glass ionomer cements

Composition• Main components are:– Glass– Polyacid– Water– Tartaric acid

• Different types and combinations of polyacid and glass create different versions of GIC

• Glass• Three main components:o Silica SiO2o Alumina Al2O3o Calcium fluoride CaF2• In addition to sodium and aluminium fluorides, and

calcium or aluminum phosphates.• Components are fused at high temperatures, shock

cooled then ground to a powder. Particle size depends on application

Liquid• Liquid: co-polymers of polyacrylic acid and water• E.g. of copolymers used:• Acrylic acid and itaconic acid• Acrylic acid and maleic acidViscosity of the liquid depends on molecular

weight and polyacid concentration.Tartaric acid influences working ad setting time

DISPENSING• 2 bottle system hand mixed:o Powdero Liquid• Anhydrous cement: powder (glass and freeze dried

polyacid) and distilled water• Capsules (pre-measured powder and liquid) mixed using

a triturator (mixer). Easy to use, GIC is directly dispensed into cavity, eliminate errors from manual mixing.

Acid base reaction. Three overlapping steps:• Dissolution• Gelation• Hardening

Glass ionomer cements

Composition and reaction explained previouslyUses:• low/high strength bases (in deep cavities use

calcium hydroxide instead)• Luting agents• Core build up• Restorative material (e.g. class V)• Manipulation

Resin modified-GIC

Uses:• Permanent cementation of crowns and

bridges• Core build up• Liners• Bonding of orthodontic brackets

Resin modified-GICProperties:• Fluoride release• Low solubility once set• Early low pH then increases• High fracture toughness but lower than resin cements• Problem of water sorption (contraindicated for all-

ceramic restorations, may cause cracking due to expansion)

• Manipulation: capsules, powder liquid systems

Resin-based cements

• They are modified composites … Microfill or microhybrid• Properties:

– Insoluble and high wear resistant– Good esthetic under all-ceramic crowns– Bonded by etching and bonding, sandblasting of internal surface

of restoration

• Setting:– Chemical cure– Light cure– Dual cure: most versatile

Compomer cements

• Composition:– Powder: fluorosilicate glass, sodium fluoride, self-cured and

light-cured initiators– Liquid: polymerized-methacrylate-carboxylic acid monomer,

water, acrylate-phosphate monomer, diacrylate monomer• Properties:– Fluoride release– low solubility– high bond strength– high fracture toughness and strength