The effects of cavity size and filling method on the bonding to Class I cavities.

Abstract

The effects of incremental filling technique and flowable liner on the bond strength of resin composite in different sized cavities were investigated in this study. Two sizes of cylindrical Class I cavities were prepared in bovine dentin (98.1 mm3 and 21.2 mm3). A light-curing resin composite (Clearfil Photocore) with a self-etching primer adhesive (Clearfil SE Bond) was used to bulk fill the cavities (C-factor 5), with and without flowable liner (Clearfil FLOW-FX) or incremental filling (2 layers, C-factor 3). As control, a 3-mm or 5-mm buildup was placed on the flat dentin surface (C-factor 0.2). After 24 h storage in 37 degrees C water, the microtensile bond strength was measured at a crosshead speed of 1 mm/min. Mode of failure in the fractured specimens was observed using a scanning electron microscope. The obtained results were statistically analyzed. In large cavities, incrementally filled and lined cavities showed higher bond strength values than the bulk-filled subgroup (p < 0.05). However, in small cavities, neither the incremental technique nor flowable liner improved the bond strength. Not only the filling techniques but also the cavity size affected the bond strength to the cavity floor in cylindrical Class I cavities.