Effect of restorative procedures and occlusal loading on cuspal deflection.

This study examined the extent of cuspal flexure caused by progressively larger cavity preparations, including endodontic access, and progressive simulated occlusal loading with 50N, 100N and 150N. Ten intact extracted maxillary premolars were embedded in acrylic resin, and a small ball was attached to each cuspal tip as a reference point for intercuspal distance measurements. The teeth were subjected sequentially to the following procedures: conservative MO cavity preparation, extensive MO cavity preparation, endodontic access step and MOD cavity preparation. After each cavity preparation procedure, the specimens were subjected to increasing loads of 50, 100 and 150 N, and the intercuspal distance was recorded by means of a digital caliper. The extension of cavity preparation and the magnitude of occlusal load significantly influenced cuspal deflection. After 50 and 100 N loading, a similar cuspal deflection was exhibited by conservative and extensive MO preparations with or without the endodontic access step. With 150 N loading, the endodontic access step was related to a statistically larger cuspal deflection versus the deflection recorded for conservative and extensive MO preparations. The removal of both marginal ridges in MOD cavity preparation with endodontic access produced a dramatic increase in cuspal deflection for the three loads tested.