Presentation on theme: "Dental cements أحمد عبد العزيز الحسين"— Presentation transcript:
1Dental cements أحمد عبد العزيز الحسين أخصائي تركيبات سنيه في وزارة الصحة الأردنيةمحاضر غير متفرغ في جامعة العلوم والتكنولوجيا الأردنيةAhmad Abdul Aziz AlhussienProsthodontist at M.O.HPart time lecturer at J.U.S.TBSc , MSc, Jor. Board/ prosthodontics
4Cavity varnisha 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.
5Cavity varnish Application method: The varnish is applied in a thin layerThe solvent evaporates within 5 –15 secondsA second layer is appliedThe resin component protects pulp by:Sealing dentinal tubulesReducing microleakageReduce staining
6Dispensing and clinical considerations 2 bottles: Varnish: 90% solvent, 10% resin (copal)Solvent to dilute varnish if solvent evaporatesThe lid should be kept tightly closedVarnishes have been largely replaced by bonding agents since varnishes wash out quickly
7Liners/low strength base Calcium hydroxide Clinical uses:Liner to protect pulpDirect and indirect pulp cappingDispensing:2 paste system “Self-cured”Base: Calcium phosphate, calcium tungstate, Zinc oxide, Glycol salicylateCatalyst: Calcium hydroxide, zinc oxide, zinc stearate in ethylene toluene sulfonamideLight cured cement: UDMA + Ca hydroxide + barium sulfate filler and low viscosity monomer
8Liners/low strength base Calcium hydroxide Set cement is calcium disalicylateProperties:Has an alkaline Ph 9-11(stimulates dentine formation)Setting time: 2-7 minutesWeak compressive strengthThermal insulatorHigh solubility
9Liners/low strength base ZnO/Eugenol Uses:Pulpal protection in deep cavitiesProperties:WeakSedative effectLittle thermal insulation
10High strength base (>0.5mm) Function:InsulatorSupport for restorationMaterials used:GICResin modified-GICPolymer reinforced ZnO/EProperties required for high strength bases:High strength that develop quicklyLow thermal conductivityModerate elastic modulus
11Luting cements Desirable features: Good wettability Good flow Thin film thickness: 25 µm or less to fill the space between tooth structure and restoration.
12RestorationsPermanent: cements are rarely used as restorations due to:Low strengthLow wear resistanceHigh solubilityThe exception is GIC, used for class V cavities and primary teeth.
15Zinc oxide eugenol Advantages: Disadvantages Wide variety of uses Sedative to the pulpEasily manipulatedDisadvantagesLow strengthHigh solubilityNot used under composite resin
16Zinc oxide eugenol Some are resin or EBA reinforced New products are eugenol free “cavit”Properties:Sedative effect on pulp and antibacterialBiocompatible .. irritant if in direct contact with pulpEugenol interferes with setting of resinModerate strengthRetention is mechanicalWater and temperature increase accelerate setting
17Zinc phosphate Used to be used as a permanent luting agent Composition:Powder: zinc oxideLiquid: phosphoric acid and water buffered by Al + Zn to slow settingSetting reaction: 5-9 minutes, exothermic, controlled by incremental incorporation of powder into liquid. Cement is porous.
18Zinc phosphate Properties Initial acidity with pH of 4.2, becomes neutral after 48 hours.Retentive by mechanical retention sandblasting of crowns or inlaysSimilar strength to GIC, high CS, low tensile strength.Low solubility once setFast settingMoisture adversely affects cement
19Zinc phosphate Manipulation Powder is dispensed and divided into 4-6 portionsLiquid is dispensed according to manufacturerMixing is gradual at 15 seconds intervals for secondsLarge strokes over a large area
20Zinc polycarboxylate Uses: Composition: High strength base Final cementation of indirect restorationsComposition:Powder: zinc oxideLiquid: polyacrylic acid
21Properties:Lower compressive strength than other cementsMild acidityHigher viscosity when mixed but reasonable flowLiquid should not be dispensed before needed, to avoid water evaporation and viscosityRetention is chemical and mechanicalTo increase working time use a cold slabManipulation: powder liquid systems, 90% of powder added first then the rest is mixed with liquid to adjust consistency
22Glass ionomer cements Composition Main components are: PolyacidWaterTartaric acidDifferent types and combinations of polyacid and glass create different versions of GIC
23GlassThree main components:Silica SiO2Alumina Al2O3Calcium fluoride CaF2In 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
24LiquidLiquid: co-polymers of polyacrylic acid and waterE.g. of copolymers used:Acrylic acid and itaconic acidAcrylic acid and maleic acidViscosity of the liquid depends on molecular weight and polyacid concentration.Tartaric acid influences working ad setting time
25DISPENSING2 bottle system hand mixed:PowderLiquidAnhydrous cement: powder (glass and freeze dried polyacid) and distilled waterCapsules (pre-measured powder and liquid) mixed using a triturator (mixer). Easy to use, GIC is directly dispensed into cavity, eliminate errors from manual mixing.
26Acid base reaction. Three overlapping steps: DissolutionGelationHardening
27Glass ionomer cements Composition and reaction explained previously Uses:low/high strength bases (in deep cavities use calcium hydroxide instead)Luting agentsCore build upRestorative material (e.g. class V)Manipulation
28Resin modified-GIC Uses: Permanent cementation of crowns and bridges Core build upLinersBonding of orthodontic brackets
29Resin modified-GIC Properties: Fluoride release Low solubility once setEarly low pH then increasesHigh fracture toughness but lower than resin cementsProblem of water sorption (contraindicated for all-ceramic restorations, may cause cracking due to expansion)Manipulation: capsules, powder liquid systems
30Resin-based cementsThey are modified composites … Microfill or microhybridProperties:Insoluble and high wear resistantGood esthetic under all-ceramic crownsBonded by etching and bonding, sandblasting of internal surface of restorationSetting:Chemical cureLight cureDual cure: most versatile
31Compomer cements Composition: Properties: Powder: fluorosilicate glass, sodium fluoride, self-cured and light-cured initiatorsLiquid: polymerized-methacrylate-carboxylic acid monomer, water, acrylate-phosphate monomer, diacrylate monomerProperties:Fluoride releaselow solubilityhigh bond strengthhigh fracture toughness and strength