Objective: The purpose of this study was to investigate if incremental-filling technique and cavity size would affect the bond strength of resin composite.
Methods: Two sizes of Class I cavities were prepared in bovine dentin (large cavities: pi x (5/2)2 x 5 mm3; small cavity: pi x (3/2)2 x 3 mm3). Light-cure resin composite (Clearfil Photocore) with a self-etching primer adhesive (Clearfil SE Bond) was placed into the cavities by bulk filling (C-factor=5) or incremental filling (two layers, C-factor=3) and light-cured. As a control, 3 or 5mm thick resin composite was bonded to the flat dentin surface. After 24h storage in 37 degrees C water, the micro-tensile bond strength was measured at a crosshead speed of 1mm/min. The results obtained were statistically analyzed using two-way ANOVA and t-test at a significance level of P=0.05.
Results: The results obtained showed that there was no significant difference among the filling techniques in small cavities (P>0.05). However, in large cavities, bulk filling presented the lowest bond strength (P<0.05).
Significance: Not only the filling technique affected the bonding strength to the cavity floor, but the cavity size was also an influential factor in Class I cavities.