cementation in Fixed prosthodontics

transcript

Cementation in Fixed ProsthodonticsBY : ABDEL RAHMEN M. ABDEL HAMEED

Content

Clinical importance

Bonding mechanismsClassification of luting cementsIdeal criteria of luting cementsCement selection

Cementation

Special consideration:

Content

Clinical importance

Cementation

Clinical importance

Content

Clinical importance

Cementation

Bonding Mechanisms

Mechanical bonding

Molecular Adhesion

Micromechanical bonding

Bonding Mechanisms

Mechanical bonding

Molecular Adhesion

Mechanical bonding:

Bonding Mechanisms

Mechanical bonding

Molecular Adhesion

Molecular adhesion include the use of chemical

bonding between tow materials. Such as chemical

bonding, occur between the COOH group of the zinc

polycarboxylate and glass ionomer (GIC) cements

and the tooth structure.

Silane coupling agent is another example for

molecular bonding mechanism

Bonding Mechanisms

Mechanical bonding

Molecular Adhesion

This mechanism use the microstructure of the tooth structure to provide retention.

The bond strength of micromechanical bonding mechanism sometimes

exceed the cohesive bond of enamel.

Ceramics can be etched with hydrophloric acid and silanated, before using

resin cement with it. Metals also can be prepared by electrolytic etching,

chemical etching or sandblasting before using the resin cement with it.

Content

Clinical importance

Cementation

Classification of luting cements

According to the duration in

clinical performance

definitive

Provisional

According to reaction

mechanism

acid base reaction

polymerization reaction

Content

Clinical importance

Cementation

Ideal criteria of luting cements

Physical properties

Biocompatibility

Sealing and Anticariogenic Activity

Adhesion

Mechanical properties

Fatigue strength

Fracture toughness

Elastic Modulus

Handling and radiopoacity

Ease of use

long working time

short setting time

Radiopoacity

Esthetic

Content

Clinical importance

Cementation

Cement selection

Zinc phosphate cementZinc polycarboxylate cementGlass Ionomer cementsZinc oxide eugenol cements:Resin cementsResin modified glass ionomer

Cement selection

Zinc phosphate cement

Compressive strength (st): 96-110

Tensile st: 9.3 Mpa

PH during cementation: 3.5

Film thickness: 10-20 um

Cement selection

Zinc polycarboxylate cement

Compressive st: 50-80 Mpa

Tensile St: 7-10 Mpa

Bond strength to tooth structure: 9

Mpa for Enamel and 3.3 Mpa for

Dentin.

PH during cementation: 4.8

Film thickness: 13-20 um

Cement selection

Glass Ionomer cements

Compressive st: 127 Mpa

Tensile st: 8Mpa

Bond st to tooth structure: 9 Mpa for enamel and 3 Mpa for

dentin

Film thickness: 9.5 – 16 um

advantages

fluoride

Bond to tooth structure

good esthetic properties

less soluble than zinc phosphate cement

GIC is 65% more retentive than zinc phosphate cement.

disadvantages

high acidity

sensitive to both moisture and dehydration

. GIC is translucent

Cement selection

Zinc oxide eugenol cements:

Cement selection

Zinc phosphate cementZinc polycarboxylate cementGlass Ionomer cementsZinc oxide eugenol cementsResin cementsResin modified glass ionomer

Resin cements

Compressive st: 200-250 Mpa

Tensile st: 40-50Mpa

Film thickness: 25 um

Solubility in water: Insoluble

Resin cements are composed of organic matrix such as BISGMA or UDMA and inorganic fillers

Advantages

high mechanical properties

good seal abilities

good bond strength

no solubility

excellent esthetic

disadvantages

polymerization shrinkage

pulpal irritation

difficulty of removing the hardening

excess cements.

Classification of resin cement

According to the adhesive

scheme

Self-etching Self-adhesive

Total etching

According to the mode of

polymerization

Chemical cure Light cure Dual cure

Total etching resin cements

use three step bonding technique

Acid etching

Bonding

Cement application

Self-etching

The bonding agent is applied directly to

the tooth structure and cured, and then

the resin cement is applied.

Self-adhesive resin cements

The adhesive resin cement can be applied

directly to the tooth structure. It provide the

best retention with dentin.

Cement selection

Zinc phosphate cementZinc polycarboxylate cementGlass Ionomer cementsZinc oxide eugenol cementsResin cementsResin modified glass ionomer

Resin modified glass ionomer

Compressive st: 150 Mpa

Tensile st: 25-35 Mpa

Film thickness: 20 um

Resin modified glass ionomer combine the strength and the insolubility advantages of the resin cements and the fluoride release of the GIC

Content

Clinical importance

Cementation

Cementation with Zinc phosphate cementCementation with Zinc polycarboxylate cementCementation with glass ionomer cementsCementation with resin cements

Cementation

Cementation with Zinc phosphate cement

tips for cementation :

Complete isolation is necessary during the whole process.

Vital teeth ---> two layers of varnish or bonding agent should be applied first.

Non-vital teeth ---> No need for varnish.

Liquid/Powder Proportions: six drop of liquid for each crown.

Do not dispense the liquid until just before mixing.

Divide the powder in small increments each of 3 mm thickness.

Mixing time is 10-20 seconds for each increment.

Mix in circular motion. Mix over wide area of the glass slab introduce the powder slowly in to the liquid check the consistency Bruch the cement inside the fitting surface

grooves, pins, and inlays ---> fill them before seating the restoration

If necessary use the retraction cord in the sulcus.

seat the restoration ask the patient to close over a plastic wafer Leave the cement to fully set then remove

the excess.

Cementation

Cementation with Zinc polycarboxylate cement

Tips for cementation: Isolation wash the restoration and clean it with

alcohol sandblast the fitting surface coat the outer surface with petroleum Powder/Liquid Proportion : according to

manufactures instructions

working time: 30 seconds

brush the cement inside the restoration,

seat the restoration, ask the patient to bite

over aplastic wafer

setting time: 3 minutes

Remove the excess either before or after the

cement become rubbery.

Cementation

Cementation with glass ionomer cements

tips for cementation isolation coat outside the restoration with petroleum Clean the tooth with brush and pumice. don’t

use acid etch for this step Don not use varnish Powder / Liquid proportions : one scoop of

powder/ two drops of liquid working time: 60 seconds setting time : 3 minutes

mix rapidly until the mix become creamy

capsule form is now available in the market

Brush the restoration with the cement; seat the restoration, ask the patient to occlude over the plastic wafer.

Wait until the cement become brittle but before complete setting and remove the excess cement.

Coat the crown margin with varnish or petroleum

Cementation

Cementation with resin cements

Tooth preparation : isolation ( rubber dam is a must) clean the tooth with pumice and brush, clean and

dry if total etching system is used :

apply the acid etch ( phosphoric acid 37% ) 30 seconds for enamel and 10 seconds for dentin

wash and dry ( don’t dissipate dentin) apply the bond with brush, wait for 1 minute, cure

for 20 seconds

if self-etching system is used

apply the self-etching bond , wait for 1 minutes and

If total etching system will be used the tooth not

need any preparation more than cleaning with brush.

treatment of the fitting surface of the restoration :

The fitting surface of the restoration is treated before receiving the resin cement by two ways Roughening the surface to increase the surface

area and create a microspores In the restoration surface

Increase the wettability of the restoration surface with silane coupling agent.

Roughnining of the fitting surface can be achieved by various techniques depending on the type of the restoration.

Content

Clinical importance

Cementation

Cementation of ceramic restorationsBonding of resin to zirconia: Cementation of posts Cementation of partial coverage restorationCementation of the gold alloy:

Cementation of ceramic restorations

tooth preparation

restoration preparation differ according to the type of the ceramic material: Feld spathic porcelain ( HF + S )

Lucite reinforced ceramics (IPS Empress): ( sand + S )

Lithium disilicate (IPS Emax( ( Sand + HF + S )

Zirconia Lava ( Silica )

Cercon ( Silica + MDP )

other types such as IPS Emax zircad and Ketana (Phosphoric acid monomer containing primer)

Bonding of resin to zirconia:

sandblasting and silanation of zirconia

Plasma spraying

Porcelain particles infusion

Cementation of posts

Metallic posts

Fiber posts

Cementation of partial coverage restoration

Cementation of the gold alloy:

cementation in Fixed prosthodontics

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