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By The Name of GodPS OF COMPOSITE MATERIALS Mohammad H Nabulsi BDS, MFDS RCS(Ireland), JDB Cons
Road mapI. Basic part 1. Definition of composite. 2. Mechanism of PS. 3. Factors affecting amount of PS. 4. Amount of PS. 5. Direction of PS. 6. Consequences of PS. 7. Factors affecting amount of PSS.II. Clinical part: 1. Manufacturer methods. 2. Operator methods.
Clinical situations But, in clinical situation No
Clinical situations Versluis A, Tantbirojn D, Douglas WH. Do dental composites always shrink toward the light? J Dent Res 1998;77:1435-1445.
Clinical situations• The direction of PS was not significantly affected by the orientation of the incoming curing light.• Instead, the direction of the PS vectors determined by: 1. The cavity shape. 2. The bond quality.
Clinical situations• The study concluded that: • The contraction patterns between SC & VLC composites were similar in clinical situation.• PS occurs toward the strongest bonded walls of cavity preparations (which is enamel margin), regardless of the initiator mode.[89,90]
PS of resin composite materialsWHAT DOES PS CAUSE?
C-Factor Feilzer AJ, de Gee AJ & Davidson CL. Setting Stress in Composite Resin in Relation to Configuration of the Restoration. J Dent Res 1987;66:1636-1639.
C-Factor BONDED walls C-Factor = FREE walls(Feilzer AJ, de Gee AJ & Davidson CL. J Dent Res 1987;66:1636-1639)
C-Factor reduce the PS & PSS Which provide more free surface for flowWe aretrying toreduce theC-factor
C-FactorHow we can utilize C-factor concept in ourwork?
C-Factor • Change the cavityOne configuration • Change the incrementTwo configuration • BothThree
C-FactorBox form V-shape form
C-Factor• By using “oblique incremental layering technique”.
Operator methodsINCREMENTAL PLACEMENTTECH
Incremental placement techIncremental placement tech is the mostproofed, commonly used tech to reduce theeffect of setting contraction.
Incremental placement tech• How it’s work? 1. Reducing the bulk of resin composite cured at a time.  2. Reducing C-Factor. 
Incremental placement tech• Three variations of the basic oblique- layering tech are described: 1. Successive cusp buildup. (video) 2. Separate dentin & enamel buildup. 3. Separate dentin & enamel buildup using an index.
Operator methodsBONDED-BASE TECH
Bonded-base tech Vitrabond (3M-ESPE)
Bonded-base tech Vitremer (3M-ESPE)
Bonded-base tech• The tech is indicated when: 1. Gingival margin of a Cl II preparation is in enamel, but within 1 mm of the CEJ. 2. If it’s in the dentin.
Bonded-base tech reduce the PS & PSS reducing the bulk of composite materialsPlacingRMGIbelowcompositerestoration
Bonded-base techBonded-base tech has demonstrated goodclinical performance. [169-172,259]
Bonded-base techThe first evaluation used a conventionalGIC showed poor clinical longevity. However, use of an RMGI has proven to bea viable tech. [169-172,259]
Operator methodsELASTIC BONDING CONCEPT
Elastic bonding conceptTo understand the “elastic bonding concept”we should answer the following question.
Elastic bonding conceptWhat’s the relationship between PS, SS andcomposite composition?
Elastic bonding concept Kleverlaan CJ, Feilzer AJ. Polymerization shrinkage and contraction stress of dental resin composites. Dent Mater 2006;21:1150–5
Elastic bonding conceptHigher filler content →reduce PSBut, produces higher PSS !!!due to increase EM
Elastic bonding conceptHow we can solve this problem ?Elastic bonding concept
Elastic bonding concept to relieve PSS of the provide restorative sufficient composite elasticityStretching ofviscousintermediatelayer