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 oxide
Magnesium oxide
Other oxides and
Fluorides may be
present
Liquid :
Phosphoric acid
30-40% Water
ZnO or Al(OH)3 as
buffering agents
COMPOSITION:

ZINC-PHOSPHATE CEMENTZINC-PHOSPHATE CEMENT
MANIPULATION:MANIPULATION:

MANIPULATION:MANIPULATION:
 Zinc-phosphate material is mixed onZinc-phosphate material is mixed on aa
thick,cooled glass slabthick,cooled glass slab usingusing stainless steelstainless steel
spatulaspatula (Freeze slab technique)(Freeze slab technique) toto ↑↑ W.T. andW.T. and
S.T.S.T.
 Powder is added to liquid small increment byPowder is added to liquid small increment by
small increment to help insmall increment to help in buffering the acidbuffering the acid
and toand to ↑↑ W.T. and S.T.W.T. and S.T.

MANIPULATION: (Cont.d)MANIPULATION: (Cont.d)
Mixing should be done over aMixing should be done over a wide areawide area
to help in heat dissipationto help in heat dissipation ↑↑ W.T. andW.T. and
S.T.S.T.
Thin mixThin mix (by(by↑↑L/P ration)L/P ration) is used foris used for
cementation purposescementation purposes
Thick mixThick mix (by(by ↓↓L/P ratio)L/P ratio) is used asis used as
cavity basecavity base oror temp. fillingtemp. filling

MANIPULATION: (Cont.d)MANIPULATION: (Cont.d)
PrecautionsPrecautions ………………….………………….;;
1.1. Liquid bottle should beLiquid 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 withLiquid with Cloudy appearanceCloudy appearance discardeddiscarded
3.3. Shake the powder bottleShake the powder bottle before dispensing thebefore dispensing the
correct ratio andcorrect ratio and never usenever use powder ofpowder of other cementsother cements
(e.g. ZOE…)(e.g. ZOE…) oror of other manufacturerof other manufacturer

SETTING REACTION:SETTING REACTION:
ExothermicExothermic chemical reactionchemical reaction of acid-of acid-
base typebase type
ZnO + HZnO + H3POPO4 ZnZn3(Po(Po4))2 + H+ H2OO
Set materialSet material is composed of ais composed of a matrix of zincmatrix of zinc
phosphate saltphosphate salt infiltrated withinfiltrated with non-reacted zincnon-reacted zinc
oxide particlesoxide particles that are responsible forthat 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 ratioL/P ratio ↑↑ S.T.S.T.
2.2. ↑↑ Mixing RateMixing Rate ↓↓ S.T.S.T.
3.3. ↑↑ Particle sizeParticle size ↑↑ S.T.S.T.
4.4. ↑↑ TemperatureTemperature ↓↓ S.T.S.T.
5.5. ↑↑ Buffering of the liquidBuffering of the liquid ↑↑ S.T.S.T.
6.6. Presence of moisturePresence 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)

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

5. Thermal properties:
 Has low thermal diffusivity used as cavity bases
under metallic restorations
6. Film thickness:
 As low as 15 µm 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 restoration
2. Cavity base
3. Temporary filling material
4. Cementation of orthodontic bands
5. Build the lost dentine up under amalgam
restorations.

RELATED MATERIALS:RELATED MATERIALS:
 Either copperEither copper (Copper cement)(Copper cement) or silver saltor silver salt
(Silver cement)(Silver cement) is added to cement powderis added to cement powder
 Resultant materials haveResultant materials have bactericidal effectbactericidal effect
 They can be used forThey can be used for filling 1ry teethfilling 1ry teeth andand
cementing orthodontic bandscementing orthodontic bands

B. SILICATE CEMENTB. SILICATE CEMENT
 Results from theResults from the reaction of phosphoric acidreaction 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 estheticesthetic
restorativerestorative long time agolong time ago
 ItsIts drawbacksdrawbacks (Acidity, solubility, shrinkage,(Acidity, solubility, shrinkage,
discolorationdiscoloration,…),…) andand thethe development of newdevelopment 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 aIt is a hybridhybrid ofof silicatesilicate andand zinc phosphatezinc phosphate
cementscements
 Powder :Powder : Mixture of zinc oxide and alumino-Mixture of zinc oxide and alumino-
silicate glasssilicate glass
 Liquid:Liquid: Phosphoric acidPhosphoric acid
 Applications:Applications:
1.1. Luting agentLuting agent
2.2. Filling of 1ry teethFilling of 1ry teeth
3.3. 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 acid
2. Has lower acidity (higher pH) than
phosphoric acid
3. Provide chemical adhesion with natural
tooth structure, base metal alloys, and tin
plated Noble metal alloys

ADHESION OF PAA-BASED CEMENTSADHESION OF PAA-BASED CEMENTS
TO TOOTH STRUCTURETO 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 Cawith Ca++++
of hydroxyapatiteof hydroxyapatite
Beech DR (1973):Beech DR (1973):
StrongStrong ionic bondsionic bonds between polyacrylate andbetween polyacrylate and
surface Casurface Ca++++
of apatiteof apatite

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 ofInitial adhesion is achieved by formation of
strong hydrogen bondingstrong hydrogen bonding, then, then replaced withreplaced with
ionic bondsionic bonds after a period of timeafter a period of time
Wilson et al. (1983):Wilson et al. (1983):
Polyacrylic ions enter the molecular structure ofPolyacrylic ions enter the molecular structure of
hydroxyapatite,hydroxyapatite, displacing and replacingdisplacing and replacing
phosphate ionsphosphate ions

TO TOOTH STRUCTURE (Cont.d)TO TOOTH STRUCTURE (Cont.d)
Wilson and McLean (1988):Wilson and McLean (1988):
Bonding of PAA toBonding 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 intermediateFormation of intermediate layer of Carbonato-layer of Carbonato-
apatiteapatite between cement and dentinebetween cement and dentine

A. ZINC-POLYCARBOXYLATEA. ZINC-POLYCARBOXYLATE
CEMENTCEMENT

A. ZINC-POLYCARBOXYLATEA. ZINC-POLYCARBOXYLATE
CEMENTCEMENT
Powder :Powder :
Zinc oxideZinc oxide
Magnesium oxideMagnesium oxide
Stannous fluorideStannous fluoride inin
some productssome products
Liquid :Liquid :
Poly-acrylic acidPoly-acrylic acid (30-(30-
40%)40%)
waterwater
COMPOSITION AND
PRESENTATION:
1. Powder / liquid system

ZINC-POLYCARBOXYLATEZINC-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

CEMENTCEMENT
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

CEMENTCEMENT
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

CEMENTCEMENT
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.

CEMENTCEMENT
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

CEMENTCEMENT
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

CEMENTCEMENT
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

CEMENTCEMENT
6. Film thickness:
Similar to zinc-phosphate cement (15 µm ), 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

CEMENTCEMENT
APPLICATIONS:
1. Final cementation of cast metal restorations
2. Cavity base
3. Temporary filling material
4. Cementation of orthodontic bands

dental cements (3) dental material

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