Analysis of gap formation at tooth-composite resin interface: effect of C-factor and light-curing protocol.
OBJECTIVE
The aim of this study was to evaluate the effect of C-factor and light-curing protocol on gap formation in composite resin restorations.


METHODS
Cylindrical cavities with 5.0 mm diameter and three different depths (A=1.0, B=2.0 and C=3.0 mm) were prepared on the occlusal surface of 30 human molars and restored in a single increment with P 60. The composite resin was light-cured according to two protocols: standard - 850 mW/cm(2) / 20 s and gradual - 100 up to 1000 mW/cm(2) / 10 s + 1000 mW/cm(2) / 10 s. After storage in distilled water (37 degrees C/7 days), the restorations were cut into three slices in a buccolingual direction and the gap widths were analyzed using a 3D-scanning system. The data were submitted to ANOVA and Student-Newman-Keuls test (alpha=0.05).


RESULTS
ANOVA detected a significant influence for the C-factor and light-curing protocol as independent factors, and for the double interaction C-factor vs. light-curing protocol. Cavities with higher C-factor presented the highest gap formation. The gradual light-curing protocol led to smaller gap formation at cavity interfaces.


CONCLUSIONS
The findings of this study suggest that the C-factor played an essential role in gap formation. The gradual light-curing protocol may allow relaxation of composite resin restoration during polymerization reaction.
dos Santos
Gustavo Oliveira
GO
Department of Restorative Dentistry, School of Dentistry, Federal Fluminense University, Ingá, Niterói, RJ, Brazil.
da Silva
Antônio Henrique Monteiro da Fonseca Thomé
AH
Guimarães
José Guilherme Antunes
JG
Barcellos
Alexandre de Araújo Lima
Ade A
Sampaio
Eduardo Martins
EM
da Silva
Eduardo Moreira
EM