Impact-fracture energy of human premolar teeth.

The fracture strength of contralateral pairs of premolar teeth was determined by an in vitro method wherein impact loads of equal energy were applied to the medial aspects of the buccal cusps. Absorbed energy values quantified the fracture resistance of unprepared teeth and teeth restored with MOD amalgams, MOD amalgam overlays, MOD gold overlays, and full gold crowns. It was established that unprepared lower premolar teeth had a greater resistance to fracture than upper premolar teeth, and lower first premolar teeth were more resistant to fracture than the other premolar teeth; the fracture resistance of premolar teeth restored with MOD amalgams was significantly reduced compared with unprepared control teeth; MOD amalgam overlays in premolar teeth produced fracture resistances not significantly different from those for the unprepared controls; and restoration of premolar teeth with MOD gold overlays and full gold crowns enhanced fracture resistance to a level much greater than that of the unprepared control teeth.