Microleakage and cusp fracture resistance of heat-treated composite resin inlays.

The purpose of this study was to examine the microleakage and cusp fracture resistance of heat-treated composite resin inlays. One hundred and twenty extracted human bicuspid teeth were prepared with MOD Class II preparations and divided into 12 experimental groups. Ten extracted human teeth were kept sound as positive controls and 10 of the prepared teeth were left unrestored as negative controls for the cusp fracture resistance experiment. The remaining prepared teeth were grouped and restored with the following restorations: bulk or incremental placement, light-cured inlays, heat-treated inlays "cemented" with enamel bonding agent, enamel bonding agent/glass ionomer "sandwich", or a dentinal bonding agent. Heat-treated inlays showed significantly (P less than 0.05) less microleakage than all other groups. The cusp fracture resistance of the heat-treated inlays was in the same magnitude as that of the traditionally placed composite resin restoration. All restorations were significantly (P less than 0.05) lower in cusp fracture resistance than sound non-carious teeth.