Effects of incremental curing on contraction stresses associated with various resin composite buildups.
OBJECTIVE
The purpose of this study was to photoelastically evaluate contraction stresses associated with various resin composite build-up procedures, including incremental curing and the use of flowable composite for pulpless molars.


METHODS
Life-sized photoelastic models of an endodontically treated molar were fabricated. The cavity represented a conservative access preparation and included four lateral walls. The following materials were used for buildup: dual-cured hybrid composite (Cleafil DC Core [DC], BIS-CORE [BC]); light-cured flowable composite (AELITEFLO LV [ALV]); and chemical-cured flowable composite (CORE-FLO [CF]). The photoelastic models were built up with the following techniques: bulk-cured (BDd [dual-cured DC], BDc [chemically-cured DC], BBd [dual-cured BC], and BC [CF]); and incremental-cured (1 mm gingivally + 3.5 mm occlusally; IAB [ALV + BC], ICB [CF + BC], and IBB [BC + BC]). Isochromatic fringes developed in the models were recorded photographically in the field of a circular polariscope, and maximum fringe order was determined. Five specimens were tested for each condition.


RESULTS
Stress intensity of the build-up methods fell into two categories: high (BDd, BBd, BC, and IAB) and low (BDc, ICB, and IBB). The difference between high and low groups was statistically significant, except between BC and ICB. The maximum fringe order was developed around the point angles at the cavity floor for all the conditions tested.


CONCLUSIONS
Type and setting mechanism of resin composite build-up technique had considerable influence on contraction stress. Incremental buildup using composites with low elastic modulus did not reduce contraction stress intensity compared with bulk-cured techniques.
Tachibana
Kana
K
Section of Crown and Bridge Prosthodontics, Department of Oral Functional Science, Hokkaido University, Graduate School of Dentistry, Sapporo, Japan.
Kuroe
Toshifumi
T
Tanino
Yukinori
Y
Satoh
Noriyuki
N
Ohata
Noboru
N
Sano
Hidehiko
H
Caputo
Angelo A
AA
D017609:Barium Compounds / Q000737:chemistry; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003188:Composite Resins / Q000737:chemistry*; D003737:Dental Cavity Preparation / Q000145:classification; D003793:Dental Restoration, Permanent / Q000379:methods*; D017220:Dentin-Bonding Agents / Q000737:chemistry; D004548:Elasticity; D006801:Humans; D008689:Methacrylates / Q000737:chemistry; D008953:Models, Anatomic; D008963:Molar; D010781:Photography; D019279:Resin Cements / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D019553:Tooth, Nonvital / Q000628:therapy
C121035:Aeliteflo; D017609:Barium Compounds; C103506:Bis-GMA, BPDM, HEMA dental-bonding resin; C469237:Clearfil Core; D003188:Composite Resins; D017220:Dentin-Bonding Agents; D008689:Methacrylates; D019279:Resin Cements; C111840:flowable hybrid composite; C074669:Clearfil Photo Bond; D017438:Bisphenol A-Glycidyl Methacrylate; D012822:Silicon Dioxide