Direct composite inlays versus conventional composite restorations: three-year clinical results

A clinical trial of direct composite inlays versus conventionally (incrementally) placed restorations made from the same material was started in January 1989. Restorations were randomly allocated to matched pairs of cavities. This study reports the 3-year performance of 71 of the 100 pairs of restorations placed over a 2-year period and followed-up every 6 months. Clinical assessments were made using USPHS criteria (indirect measurements of occlusal wear were made using Ivoclar standard dies) and annual bite wing radiographs. Direct inlays showed significantly less occlusal wear than conventional restorations, but the difference was small. The clinical performance of both types of restoration was similar and compared favourably with studies of other materials. No secondary decay was diagnosed. The direct inlays, however, took longer to place and did not reduce postoperative sensitivity or failure rate (8% failure of inlays and 4% of conventional composites over 3 years). Contouring of proximal and occlusal aspects was not facilitated with direct inlays but may be easier with indirect inlays on removable dies.