The dimensions of everyday class-II cavity preparations for amalgam

Six hundred and ten epoxy plastic models, made from impressions of permanent teeth in which class-II cavity preparations for amalgam restorations had been prepared by eight Scandinavian dentists, were examined. The outlines of the cavity preparations were relatively large, with mean buccolingual extensions occlusally of 50% of the intercuspal distance and proximally of 40% of the length of the circumference of the proximal surface. There was a gradual increase in the size of the cavities towards the distal part of the dental arch, measured both in millimeters and in relation to the anatomic structures. The amount of hard tissue being removed varied among the operators and was possibly influenced by the dentist's ability to handle the cutting instruments. The large cavity preparations may be the result of using procedures for cavity preparation which are not adjusted to the tremendous cutting potential of modern dental instruments to produce stereotyped 'ideally designed' cavities.