Does layering minimize shrinkage stresses in composite restorations?
Polymerization shrinkage of resin composites may impair restoration longevity. It is hypothesized that layering, rather than bulk, techniques result in less stress in the tooth-restoration complex. The aim of this study was to compare shrinkage stresses for different restorative techniques used for cusp-replacing restorations with direct resin composite. In a 3-D FE model, the dynamic process of shrinkage during polymerization was simulated. Time-dependent parameters (shrinkage, apparent viscosity, Young's modulus, Poisson ratio, and resulting creep), which change during the polymerization process, were implemented. Six different restorative procedures were simulated: a chemically cured bulk technique, a light-cured bulk technique, and 4 light-cured layering techniques. When polymerization shrinkage is considered, a chemically cured composite shows the least resulting stress. The differences seen among various layering build-up techniques were smaller than expected. The results indicate that the stress-bearing locations are the interface and the cervical part of the remaining cusp.
Kuijs
R H
RH
(PCT 117) Department of Preventive and Community Dentistry and Pedodontology, University Medical Centre Nijmegen, PO Box 9101, 6500 HB Nijmegen, The Netherlands. R.Kuijs@dent.umcn.nl
Fennis
W M M
WM
Kreulen
C M
CM
Barink
M
M
Verdonschot
N
N
D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003188:Composite Resins / Q000737:chemistry*; D003198:Computer Simulation; D003737:Dental Cavity Preparation; D003743:Dental Enamel / Q000502:physiology; D003793:Dental Restoration, Permanent / Q000379:methods*; D004548:Elasticity; D020342:Finite Element Analysis; D006801:Humans; D008422:Materials Testing; D008954:Models, Biological; D011108:Polymers / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D019237:Tooth Cervix / Q000502:physiology; D014783:Viscosity
D003188:Composite Resins; D011108:Polymers