Analysis of gap formation at tooth-composite resin interface: effect of C-factor and light-curing protocol

• Main Authors: Gustavo Oliveira dos Santos, Antônio Henrique Monteiro da Fonseca Thomé da Silva, José Guilherme Antunes Guimarães, Alexandre de Araújo Lima Barcellos, Eduardo Martins Sampaio, Eduardo Moreira da Silva
• Format: Article
• Language: English
• Published: University of São Paulo 2007-08-01
• Series: Journal of Applied Oral Science
• Subjects: Composite resins; C-Factor; Light-curing protocol; Gap formation; Polymerization shrinkage
• Online Access: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1678-77572007000400006

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. Material and 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/cm² / 20 s and gradual - 100 up to 1000 mW/cm² / 10 s + 1000 mW/cm² / 10 s. After storage in distilled water (37°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.