CUSPAL DEFLECTION IN MOLARS IN RELATION TO ENDODONTIC AND RESTORATIVEPROCEDURES

The extent of cuspal flexure following endodontic and restorative proc edures has important consequences for potential fracture. This study w as undertaken to determine the extent to which cusps of molars are wea kened by progressively larger restorative preparations and endodontic access, Cuspal flexure of 13 extracted, intact human mandibular molars was measured under controlled occlusal loading. A ramped load of 100 N was applied to the mesial cusps via a steel sphere, using a closed-l oop servohydraulic testing machine. Lateral cuspal displacement was re corded by linear measuring devices (direct current differential transf ormers) accurate to 1 mu m. Increasingly extensive MO or MOD cavity pr eparations followed by endodontic access were cut in each tooth. Cuspa l deflection increased with increasing cavity size and was greatest fo llowing endodontic access. Cuspal deflections of more than 10 mu m. we re observed. These findings reinforce the importance of cuspal coverag e to minimize the danger of marginal leakage and cuspal fracture in en dodontically treated teeth.