Cusp movement of molar teeth with composite filling materials in conventional and modified MOD cavities.

One hundred and twenty caries-free molar teeth were stored in saline. Three types of cavities were prepared in these teeth: conventional MOD, parallel-sided MOD with no buccal or lingual extensions, and a slit cavity. Cavity dimensions were recorded. Each group of teeth were restored with either a microfine or conventional composite, used in conjunction with a dentine adhesive. Cusp movement was recorded via two linear variable displacement transducers attached to the cusps. Using dye penetration studies, the marginal adaptation of the material to the teeth was assessed. In a small number of cases, the amount and type of cuspal movement and the degree of dye penetration was variable, depending on cavity design and the composite used, but generally cusp movement was unaffected by variation in cavity outline.