Inlay-retained FRC Restorations on Abutments with Existing Restorations: 6-year Results

Objectives: This study evaluated the clinical performance of direct, inlay-retained, fiber-reinforced-composite (DI-FRC) restorations on abutments with existing restorations up to 6 years. Methods: Between May-2003 and June-2009, 35 patients (10 females, 25 males, 43-85 years old) received a total number of 49 DI-FRC restorations (n=35 mandible, n=14 maxilla) at the Dental School, Groningen, The Netherlands. Box preparations were made on the abutments. Material surfaces as well as dental tissues were conditioned accordingly. Teeth were conditioned using a three-step adhesive system (Quadrant Unibond Primer and Sealer, Cavex). All restorations were made under rubber-dam directly. Restorations were constructed with unidirectional, preimpregnated E-glass fibers (everStick C&B, StickTech) using one resin composite (Clearfil Photo Posterior, Kuraray). Colour was improved using a flowable composite (Sinfony, 3M ESPE). After baseline recordings, patients were followed at 6 months and at annual recalls. Patients were instructed to call upon experience of a failure. The evaluation protocol involved technical failures such as chipping or fracture (tooth/restoration). Results: From those of 98 abutment teeth, 22 were metal-ceramics, 20 composite, 8 amalgam, 8 glass ceramic, 6 zirconia and the rest was natural teeth. No debondings or complete fractures but two chippings were observed on the buccal surfaces in two restorations at 1 and 2-year`s recall. They were repaired using CoJet system (3M ESPE) and remained functional. Two FRC restorations could not be observed after 4 months and 8 months, respectively since the teeth under metal-ceramic crowns needed to be endodontically treated. Based on the life-tables calculated from the data, estimated survival rate up to 6 years was 95.2% (Kaplan-Meier, 95% CI). Conclusions: Direct, inlay-retained, fiber-reinforced-composite restorations on abutments with existing restorations employing the conditioning methods, fiber and the veneering composite studied, could postphone the replacement of existing restorations.