Cusp movement in molar teeth using dentine adhesives and composite filling materials.

Forty extracted molar teeth were stored in saline. After MOD cavities were prepared and the dimensions of each cavity recorded, the teeth were restored with either a microfine or hybrid composite in conjunction with a dentine adhesive. Cusp movements were recorded from two linear variable displacement transducers attached to the cusps. Three types of movement were identified, one in which the opposing cusps moved towards one another, the second where no movement occurred at all, and the third where both cusps moved in the same direction. The degree of movement observed with the microfine material was nearly double that recorded with the hybrid. The movement appeared to relate to the polymerization shrinkage values of the materials and to the failure of the adhesive bond between the tooth and the composite-adhesive complex.