dental cements (3) dental material

ACID-BASE REACTION CEMENTSACID-BASE REACTION CEMENTS

II. Cements based on phosphoric acidII. Cements based on phosphoric acid

A.A. Zinc phosphate cementZinc phosphate cement

B.B. Silicate cementSilicate cement

C.C. Silicophosphate cementSilicophosphate cement

II. Cements based on phosphoric acidII. Cements based on phosphoric acid

Zinc oxide Fluro-alumino-silicate glass

Phosphoric acid

Silicate cementZinc-phosphate cement

Silico-phosphate cement

A. ZINC-PHOSPHATE CEMENTA. ZINC-PHOSPHATE CEMENT

Powder :Zinc oxideMagnesium oxideOther oxides and

Fluorides may be present

Liquid :Phosphoric acid30-40% WaterZnO or Al(OH)3 as

buffering agents

COMPOSITION:

ZINC-PHOSPHATE CEMENTZINC-PHOSPHATE CEMENT

MANIPULATION:MANIPULATION:


MANIPULATION:MANIPULATION: Zinc-phosphate material is mixed on Zinc-phosphate material is mixed on a a

thick,cooled glass slabthick,cooled glass slab using using stainless steel stainless steel spatulaspatula (Freeze slab technique)(Freeze slab technique) to to W.T. and W.T. and S.T.S.T.

Powder is added to liquid small increment by Powder is added to liquid small increment by small increment to help in small increment to help in buffering the acidbuffering the acid and to and to W.T. and S.T. W.T. and S.T.


MANIPULATION: (Cont.d)MANIPULATION: (Cont.d)Mixing should be done over a Mixing should be done over a wide areawide area

to help in heat dissipation to help in heat dissipation W.T. and W.T. and S.T.S.T.

Thin mixThin mix (by (byL/P ration) L/P ration) is used for is used for cementation purposescementation purposes

Thick mixThick mix (by (by L/P ratio) L/P ratio) is used as is used as cavity basecavity base or or temp. fillingtemp. filling


MANIPULATION: (Cont.d)MANIPULATION: (Cont.d)

Precautions Precautions ………………….………………….;; 1.1. Liquid bottle should be Liquid bottle should be tightly closedtightly closed (Evaporation (Evaporation

of water will reduce the reactivity of the cementof water will reduce the reactivity of the cement))

2.2. Liquid with Liquid with Cloudy appearanceCloudy appearance discardeddiscarded

3.3. Shake the powder bottleShake the powder bottle before dispensing the before dispensing the correct ratio and correct ratio and never usenever use powder of powder of other cements other cements (e.g. ZOE…) (e.g. ZOE…) oror of other manufacturer of other manufacturer


SETTING REACTION:SETTING REACTION:ExothermicExothermic chemical reactionchemical reaction of acid- of acid-

base type base type

ZnO + HZnO + H3POPO4 Zn Zn3(Po(Po4))2 + H + H2OO

Set materialSet material is composed of a is composed of a matrix of zinc matrix of zinc phosphate saltphosphate salt infiltrated withinfiltrated with non-reacted zinc non-reacted zinc oxide particlesoxide particles that are responsible for that are responsible for material’s opacitymaterial’s opacity


SETTING REACTION: (Cont.d)SETTING REACTION: (Cont.d) Control of setting timeControl of setting time

1.1. L/P ratio L/P ratio S.T. S.T.2.2. Mixing Rate Mixing Rate S.T. S.T.3.3. Particle size Particle size S.T. S.T.4.4. Temperature Temperature S.T. S.T.5.5. Buffering of the liquid Buffering of the liquid S.T.S.T.6.6. Presence of moisture Presence of moisture S.T. S.T.


CHARACTERS:CHARACTERS:1. Biological properties: Fresh mix of zinc phosphate cement is highly

acidic (pH 1.6-3.6) due to presence of strong phosphoric acid causes pulp irritation

In deep cavity, cavity liner should be used beneath

Thin mix is more irritant than thick mix Set material becomes neutral within 48 hrs


CHARACTERS: (Cont.d)CHARACTERS: (Cont.d)2. Interfacial properties: Zinc phosphate cement shows no chemical

bonding either to tooth structure or restoration surfaces (Mechanical retention and physical adhesion)

3. Chemical properties: Cement shows some degree of solubility , and it

is dependant on L/P ratio (thin mix solubility)


CHARACTERS: (Cont.d)CHARACTERS: (Cont.d)4. Mechanical properties: Zinc phosphate cement is stronger than ZOE

(So it can be used for final cementation and as cavity bases), but it is weaker than glass ionomer and silico-phosphate cements

5. Esthetic properties: Set cement is opaque (due to presence of non-

reacted ZnO particles), so it can not be used for cementing ceramic restorations


CHARACTERS: (Cont.d)CHARACTERS: (Cont.d)5. Thermal properties: Has low thermal diffusivity used as cavity bases

under metallic restorations

6. Film thickness: As low as 15 m can be used for final cementation

7. Practicability: Needs well-trend operator due to its short S.T. Material is successfully used for a long time


APPLICATIONS:APPLICATIONS:

1. Final cementation of cast metal restoration2. Cavity base3. Temporary filling material4. Cementation of orthodontic bands5. Build the lost dentine up under amalgam

restorations.


RELATED MATERIALS:RELATED MATERIALS:

Either copper Either copper (Copper cement)(Copper cement) or silver salt or silver salt (Silver cement)(Silver cement) is added to cement powder is added to cement powder

Resultant materials have Resultant materials have bactericidal effectbactericidal effect They can be used for They can be used for filling 1ry teethfilling 1ry teeth and and

cementing orthodontic bandscementing orthodontic bands

B. SILICATE CEMENTB. SILICATE CEMENT

Results from theResults from the reaction of phosphoric acid reaction of phosphoric acid with fluoro-alumino-silicate glass powderwith fluoro-alumino-silicate glass powder

This type of cement was used asThis type of cement was used as esthetic esthetic restorative restorative long time agolong time ago

Its Its drawbacksdrawbacks (Acidity, solubility, shrinkage, (Acidity, solubility, shrinkage, discolorationdiscoloration,…) ,…) andand thethe development of new development of new materialsmaterials ( (Composite resin, Glass ionomer,..Composite resin, Glass ionomer,..) ) limited its uselimited its use

C. SILICO-PHOSPHATE CEMENTC. SILICO-PHOSPHATE CEMENT

It is a It is a hybridhybrid of of silicatesilicate and and zinc phosphatezinc phosphate cementscements

Powder :Powder : Mixture of zinc oxide and alumino- Mixture of zinc oxide and alumino-silicate glasssilicate glass

Liquid:Liquid: Phosphoric acid Phosphoric acid

Applications:Applications:1.1. Luting agentLuting agent2.2. Filling of 1ry teethFilling of 1ry teeth3.3. Die materialDie material

ACID-BASE REACTION CEMENTSACID-BASE REACTION CEMENTS

II. Cements based on polyacrylic acidII. Cements based on polyacrylic acid

(polyalkenoate cements)(polyalkenoate cements)

A.A. Zinc polycarboxylate cementZinc polycarboxylate cement

B.B. Glass-Ionomer cementGlass-Ionomer cement

Cements based on poly-acrylic acidCements based on poly-acrylic acid(polyalkenoate cements)(polyalkenoate cements)

Zinc oxide Fluro-alumino-silicate glass

Poly-acrylic

acid

Glass-Ionomer cement

Zinc-polycarboxylate

cement

CEMENTS BASED ON POLY-CEMENTS BASED ON POLY-ACRYLIC ACIDACRYLIC ACID

CHARACTERS OF PAA:CHARACTERS OF PAA:1. Viscous acid with higher molecular

weight than that of phosphoric acid2. Has lower acidity (higher pH) than

phosphoric acid3. Provide chemical adhesion with natural

tooth structure, base metal alloys, and tin plated Noble metal alloys


ADHESION OF PAA-BASED CEMENTS ADHESION OF PAA-BASED CEMENTS TO TOOTH STRUCTURE TO TOOTH STRUCTURE

Several postulations were drawn;Several postulations were drawn; Smith DC (1968):Smith DC (1968): ((The inventor of polycarboxylates)The inventor of polycarboxylates)

ChelationChelation with Ca with Ca++ ++ of hydroxyapatiteof hydroxyapatite Beech DR (1973):Beech DR (1973):

Strong Strong ionic bondsionic bonds between polyacrylate and between polyacrylate and surface Casurface Ca++++ of apatite of apatite


ADHESION OF PAA-BASED CEMENTS ADHESION OF PAA-BASED CEMENTS TO TOOTH STRUCTURE (Cont.d)TO TOOTH STRUCTURE (Cont.d)

Wilson AD (1974):Wilson AD (1974): ((The inventor of glass ionomerThe inventor of glass ionomer ) )

Initial adhesion is achieved by formation of Initial adhesion is achieved by formation of strong hydrogen bondingstrong hydrogen bonding, then , then replaced with replaced with ionic bondsionic bonds after a period of time after a period of time

Wilson et al. (1983):Wilson et al. (1983):Polyacrylic ions enter the molecular structure of Polyacrylic ions enter the molecular structure of hydroxyapatite, hydroxyapatite, displacing and replacing displacing and replacing phosphate ionsphosphate ions


ADHESION OF PAA-BASED CEMENTS ADHESION OF PAA-BASED CEMENTS TO TOOTH STRUCTURE (Cont.d)TO TOOTH STRUCTURE (Cont.d)

Wilson and McLean (1988): Wilson and McLean (1988): Bonding of PAA to Bonding of PAA to collagencollagen !!! !!! (bond to enamel (bond to enamel is better than bond to dentine)is better than bond to dentine)

Geiger et al. (1993):Geiger et al. (1993):Formation of intermediate Formation of intermediate layer of Carbonato-layer of Carbonato-apatiteapatite between cement and dentine between cement and dentine

A. ZINC-POLYCARBOXYLATE A. ZINC-POLYCARBOXYLATE CEMENTCEMENT

A. ZINC-POLYCARBOXYLATE A. ZINC-POLYCARBOXYLATE CEMENTCEMENT

Powder :Powder :Zinc oxideZinc oxideMagnesium oxideMagnesium oxideStannous fluoride Stannous fluoride in in

some productssome products

Liquid :Liquid :Poly-acrylic acid Poly-acrylic acid (30-(30-

40%)40%)waterwater

COMPOSITION AND PRESENTATION:

1. Powder / liquid system

ZINC-POLYCARBOXYLATE ZINC-POLYCARBOXYLATE CEMENTCEMENT

COMPOSITION: (Cont.d)

2. Single bottle system Poly-acrylic acid is supplied as a dry powder blended

with cement powder

This mixture is mixed with regular water to get a cement mix

3. Capsules

Recently available for automatic mixing


MANIPULATION:

Mixing of cement powder and liquid is carried out on a glass slab using a stainless steel spatula

PAA is viscous and needs more effort during mixing of material

Thin mix (P/L ratio= 1.5:1) used for cementing purposes

Thick mix (P/L ratio = 2.5:1) used as cavity base


MANIPULATION: (Cont.d)

Polycarboxylate cement adhere to stainless steel instrument, so any metallic instrument should be cleaned while cement still unset

To achieve better bonding to tooth structure;

1. Tooth surface should be cleaned and dried from saliva

2. Mixed cement should be applied to tooth structure as fresh as possible


SETTING REACTION:

Chemical reaction of acid-base type

Zinc oxide + PAA Zinc-polycarboxylate

Set material: composed of zinc-polycarboxylate matrix with un-reacted zinc oxide particles dispersed in providing the cement its opacity

Speed of the reaction is affected by temperature, P/L ratio, powder particle size, and mixing rate.


CHARACTERS:

1. Biological properties:

Very little irritating effect on the pulp because

1. Large molecular size of PAA acid, hinders its passage through dentinal tubules

2. Lower acidity of the PAA

3. Chemical bonding of PAA to tooth enamel and dentine


CHARACTERS: (Cont.d)

2. Interfacial properties:

PAA provides chemical adhesion to tooth structure, base metal alloys, and tin-plated noble alloys

3. Chemical properties:

Polycarboxylate cement is more soluble in water than zinc-phosphate cement



4. Thermal properties:

Set cement has low thermal diffusivity (can be used as cavity base)

5. Esthetic properties:

Set cement is opaque due to presence of un-reacted zinc oxide particles not used to lute ceramic restorations



6. Film thickness:

Similar to zinc-phosphate cement (15 m ), so can be used for final cementation of cast metal restorations

7. Practicability:

Little more difficult to mix than other cement with less viscous liquid


APPLICATIONS:

1. Final cementation of cast metal restorations

2. Cavity base

3. Temporary filling material

4. Cementation of orthodontic bands

Education

dental cements (3) dental material