Adhesive restorations replacing cusps

Abstract

This study addressed a clinical problem in dentistry. The problem concerns the occurrence of complete fracture of a cusp of premolars with an existing Class II restoration, and the required treatment after this cusp fracture. The traditional treatment in these cases is the making of a crown. Crown preparation requires the removal of (sound) tooth tissue. Adhesive restorations, which require less tissue removal, may offer a tissue saving alternative. The general objective was to develop clinical procedures for adhesive cusp-replacing restorations and to investigate their clinical performance. The main questions were: (1) can we rely solely on the adhesion to the remaining tooth surfaces that are exposed after cusp fracture or do we have to alter the cavity configuration and (2) which are the optimal restorative procedures for successful adhesive cusp-replacing restorations? To find answers to the research questions, in vitro load tests, finite element analyses and a clinical study were performed. After fracture of a cusp in a restored premolar and removal of the existing restoration, a large cavity remains that involves the major part of the clinical crown. The point of departure of the treatment in this study was to restore those fractured premolars by a tissue saving technique. This minimal invasive restorative procedure is characterized by the removal of carious tooth tissue and grinding of a bevel; further preparation is omitted. The results suggest that the remaining cavity does not need adaptation. Consequently, the tooth tissue saving approach should be considered in case of cusp fracture in premolars. From the laboratory studies, no essential differences were shown regarding several restoration procedures. Since there are no indications that the clinical behavior of direct and indirect restorative procedures show differences, the preferences of the dentist and the patient dictate the restorative technique of choice.