Dental cement dr shabeel pn

Topic General requirements for dental cements Classification of dental cements Component and properties Setting reaction Mixing process The uses of dental cements

Definition Dental cements : materials made from two components, powder and liquid, mixed together.

Powder + Liquid Pastelike or flowable material Hardens to a rigid solid

Uses of dental cements Luting agent Pulp protection or cavity sealer Temporary cement Permanent cement Pulp protection or cavity sealer Cavity varnish Liner Base

Uses of dental cement Filling Others Temporary filling Permanent filling Others Root canal sealer Calciumhydroxide cement Bite registration material

Luting agent Luting : the use of moldable substance to seal a space between two component. Most dental treatment necessitate attachment of prostheses to the teeth by means of luting agent.

General requirements for luting agents Biocompatibility Retention High tensile strength, fracture toughness, fatique strength Good marginal seal

General requirements for luting agents Low film thickness Ease of use Radiopacity Aesthetics

Film thickness The thickness of film between two flat surface The maximum allowable thickness is 25 µm (ADA specification No. 96) Low film thickness value is preferred

Cement base A thick layer of cement (>0.75mm) is applied under restoration to protect pulp against injuries. The base should be strong enough to resist the condensation force during the placement of restoration. Well insulation ability Good sealing

Classification of dental cements Conventional cement Zinc phosphate cement Zinc oxide-eugenol cement Polycarboxylate cement Glass ionomer cement Resin-base cement Resin cement Resin modified glass ionomer cement

Conventional cement Typically powder/liquid system Liquid is an acid Powder is a base ; insoluble in oral fluid When mixed together  Acid-base reaction

Zinc Phosphate cement

Zinc phosphate cement Powder Liquid Zinc oxide Phosphoric acid Magnesium oxide Water Alumenium phosphate

ZnO HEAT Zn+ Zinc aluminophosphate gel

Unreacted ZnO Unreacted ZnO Unreacted ZnO Unreacted ZnO Zinc aluminophosphate matrix

Setting reaction Exothermic reaction Adding of water can accerlate the reaction. Loss of water can lengthen the setting reaction.

Working time and setting time Working time commonly is 3-6 minute Setting time is 2.5-8 minute(ADA specification No.96) Depending on the manufacturer instruction

How to extend the setting time ? Reducing powder/ liquid ratio {not recommended} Mixing on the cool glass slap {no moisture} Mixing over a large area. Mixing cements in increments.

Mixing procedure There are three steps: First : add the small amount of powder into the liquid To achieve the slow neutralization of the liquid. To control the reaction.

Mixing procedure Second : Larger amount of powder is added to liquid For further saturation of liquid to newly form zinc phosphate. This steps may not effect by heat released from the reaction. {because of the less amount of unreacted acid}

Mixing procedure Finally: the small amount of powder is added again To control the optimum consistency

1 2 3 4 5 6 7 8

4 5 2 3 7 6 8 1

Characteristic properties Setting time at 37O 5 – 9 minutes Minimum compressive strength 75 MPa Maximum film thickness 25 µm (for luting the prostheses) Maximum Solubility 0.2% by weight ADA specification NO.8 for Zinc phosphate cement

Effects of manipulation on some properties. Manipulative variables Properties Copressive strength Film thickness Solubility Initial acidity Setting time Decreased powder/liquid ratio Increase rate of powder incorporation Increase mixing temperature Water contamination

Biocompatibility Acid can penetrate into the dentinal tubule  irritate pulp pH of cement Liquid = 2.0 3 minutes after mixing = 4.2 1 hour = 6 48 hours = 7

Modified zinc phosphate cement Fluoride cement Add Stannous fluoride Higher solubility/ Lower strength Zinc silicophosphate Zinc phosphate + Silicate Higher strength/ lower solubility Fluoride released Translucency

Clinical applications Zinc phosphate cement Luting agent Base and temporary filling Modified zinc phosphate Luting prostheses Luting the orthodontics band

Zinc oxide-eugenol cements Lower strength than Zinc phosphate cement. Sedative effect Usually used as temporary filling

Zinc oxide-eugenol cement Simple ZOE Reinforced ZOE EBA cement

Compositions of simple ZOE Powder Zinc oxide Rosin : reduce the brittleness of the set cement Zinc stearate : plastcizer Zinc acetate : improve strength Liquid Eugenol and olive oil

Setting reaction First ZnO + Eugenol -- water Zn(OH)2 Second Zn(OH)2+2HE  ZnE2+H2O

Setting reaction Water accelerates the reaction Zinc eugenolate is easily hydrolized by moisture

Manipulation Paste/paste Powder/liquid Mix two equal pastes together until it obtains the homogeneous color. Powder/liquid Usually 4/1 for maximum strength Mix the large increment, firstly Not require cool glass slap

Classification Type I Type II Type III Type IV Temporary luting cement Permanent cementation Type III Temporary restoration [for a few days] Type IV Cavity liner

ZOE

Specification requirements Type Setting time [min] Compressive strength [MPa] Solubility [%] Film thickness [µm] Type I 4-10 35 maximum 2.5 25 Type II 1.5 Type III -

Reinforced ZOE Used as the intermediate restorative materials (IRMTM) Add 10-40% resin polymer in the powder for strengthening the set cement Compressive strength 35-55 MPa

EBA cement Powder Liquid Compressive strength 55-75 MPa Add 20-30% of aluminium oxide Liquid Add 50-60% ethoxybenzoic acid in eugenol Compressive strength 55-75 MPa

Clinical applications Base Temporary cementation Permanent cementation If cement contains eugenol, it is not to use with resin restorative material.

Zinc polycarboxylate cement Or called Zinc polyacrylate cement The first adhesive cement Bond to tooth structure and metal More biocompatibility than zinc phosphate cement Polyacrylic acid have more molecular weigth Moderate strength/ moderate solubility

Composition Powder [the same as zinc phosphate cement ] Liquid Zinc oxide Magnesium oxide Stannous fluoride Liquid Aqueous solution of polyacrylic acid Other carboxylic acid

Manipulation Mix first half of powder to liquid to obtain the maximum length of working time. The reaction is thixotropic The viscosity decreases when the shear rate increases

Setting reaction Like zinc phosphate cement Retarded by cool environment

Bonding to tooth structure The polyacrylic acid is believed to react with calcium ion via the carboxyl group. The adhesion depends on the unreacted carboxyl group.

Specification requirements Setting time at 37OC: 9 minutes Maximum film thickness: 25µm Minimum compressive strength: 50 MPa Maximum solubility: 0.2%

Applications Cement inlays or crowns Used as base Temporary filling Lute the stainless steel crown

Glass ionomer cement Or called Polyalkynoate cements Conventional glass ionomercement Resin-modified glass ionomer cement [RMGICs] Powder + Liquid/ Powder + water/ Encapsulated

Composition Powder Liquid Calcium aluminum fluorosilicate glass Polyacid Copolymer of polyacrylic / itaconic acid Copolymer of polyacrylic / maleic acid Add tartaric: accelerator

Setting reaction There are three stages: Dissolution Gelation Hardening. Water hardening or water setting

Dissolution Ca2+ Al3+ F- Polyacid liquid Glass core Silica gel Hydrogen ions Ca2+ Al3+ F- Silica gel Glass core

Gelation Polyacid liquid Cross-linked polyacid -COOH Ca2+ Al3+ F-

Gelation Calcium ions have more reactivity than aluminium ions. This is critical phase of contamination.

Hardening Polyacid liquid Cross-linked polyacid -COOH Al3+

Hardening Last as long as 7 days. The reaction of aluminium ions provides the final strength of set cement.

Glass core Cross-linked polyacid Silica gel

Properties Film thickness is similar or less than zinc phosphate cement. Setting time 6 to 8 minutes from start of mixing. Less pulpal irritation. Bacteriocidal or bacteriostatic. Prevent caries.

Strength The 24-hour compressive strength is greater than zinc phosphate cement. The compressive strength increase to 280MPa between 24 hours to 1 year after initial setting.

Bonding It can be chemically bonded to the tooth structure. The mechanism of bonding is the same as polyacrylate cement. The dentine bond strength may be lower than polyacrylate because of technique sensitivity.

Modified GI Cermet Resin-modified GI Combination of glass and metal No significantly improve the strength More wear resistance and short setting time Resin-modified GI

Resin-modified glass ionomer cement Add polymerizable function groups Both chemical & light curing Overcome moisture sensitive & low early strength Names: Ligth cured GICs, Dual-cured GICs, Tri-cured GICs, Hybrid ionomer, Compomers, Resin-ionomers

Setting reaction Polymerization Acid-base reaction initial setting Acid-base reaction maturing process & final strength Heat released from the polymerization reaction.

Properties Higher strength than conventional GI Higher adhesion to resin material Less water sensitivity Can be polished after curing

Relative properties of a glass ionomer and a resin-modified GI cements Property GIC RMGIC Working time 2 min 3 min 45 sec Setting time 4 min 20 sec Compressive strength 202 MPa 242 Mpa Tensile strength 16 Mpa 37 Mpa

Applications Type I : Luting agent Type II : Filling material Type III : Base and liner

Conventional GI for cementation

GI filling material

Adhesive resin cement Occur later from the direct filling resin Become popular because of the improved properties, high bond strength. Resin cement is flowable composite resin.

Composite resin cement Resin matrix + inorganic filler Silane coated

Composition Filler Matrix Silica Bis-GMA (polymer) The fillers binds with matrix by silane coupling agent

Setting reaction Polymerization Chemical activation Light activation Dual activation [chemical and light]

Preparations Powder / liquid Chemical, light, or dual cure 2 paste system [base / catalyst] Single paste Light cure

Bonding system Bond with the tooth surface by enamel an dentine bonding system. Bond with metal by using metal primer. Bond with ceramic restoration by treating the surface of porcelain with silane coupling agent

Properties Very good bond strength High compressive strength Water sensitive Might irritate pulpal tissues

Applications Tooth color filling materials Luting cements

Calcium hydroxide cement Used as base and liner High pH value Good biocompatibility

Composition 2 Pastes system Base Catalyst Salicylate  reaction Calcium tungstate and barium sulfate  radiopacity Catalyst Calcium hydroxide

Properties Lower compressive strength than others Resist to the condensation force of amalgam filling High pH 9.2-11.7 [Alkaline] Bactericidal High solubility

Properties Stimulate the secondary dentine formation in the area of thin dentine [<0.5mm] Stimulate the dentine formation in the exposed-pulp lesion [Direct pulp capping]

Comparable properties of cements

Compressive strength [MPa] Zhen Chun Li and Shane N. White, 1999

Bond strength Separation forces [MPa] Sule Ergin and Deniz Gemalmaz, 2002

Film thickness [µm] Shane N. White, Zhaokun Yu, 1992

Others Solubility Irritation to pulp tissues ZOE > Polycarboxylate > Zinc phosphate~GIC > Resin cement Irritation to pulp tissues Resin~Zinc phosphate > GIC > Polycarboxylate > ZOE~Calcium hydroxide

References Textbooks Kenneth J. Anusavice Phillips’ science of dental materials 11th edition W.B. Saunders company 2003

References Textbook Robert G. Craig Restorative dental materials 9th edition Mosby company 1993

References Textbook Richard van Noort Introduction to dental materials 2nd edition Mosby company 2002

References Journals Li ZC, White SN. Mechanical properties of dental luting cements. J Prosthet Dent 1999;81(5):597-609 White SN, Yu Z. Film thickness of new adhesive luting agents. J Prosthet Dent 1992;67(6):782-90 Ergin S, Gemalmaz D. Retentive properties of five luting cements on base and noble metal copings. J Prosthet Dent 2002;885:491-97