Eight-year clinical evaluation of fired ceramic inlays

This study evaluated the quality of fired ceramic inlay restorations consisting of a feldspathic porcelain system (G-Cera Cosmotech II, GC Co, Tokyo, Japan) after eight years in vivo. Forty-five fired ceramic inlays (for 26 premolars and 19 molars; Class I in 12 teeth, Class II in 31 teeth and onlay in two teeth) were placed in 25 patients. All restorations were evaluated at the time of placement and at 6 months, 1, 2, 4, 6 and 8 years after placement using modified USPHS criteria. Replicas of the restorations were observed with a scanning electron microscope (SEM) to evaluate the degradation of the marginal area and wear loss of the restoration. Longevity was observed in 80% of the fired ceramic inlay restorations at eight years (Kaplan-Meier method), although it was 92% at the six-year observation. Marginal fracture was detected in 11 restorations (22%), including bulk fracture in five (11%), which had first occurred during the last two years. Recurrent caries was observed in three (7%) cases and marginal discoloration in 14 (31%). SEM evaluation disclosed marginal microfractures in 77% of the restorations, wear in 36% and wear of the resin cement along the margin in 74% at eight years. No significant difference was observed in each of these three characteristics between molars and premolars. This longitudinal eight-year clinical observation suggested that fired ceramic inlay restorations made by the G-Cera Cosmotech II system are clinically acceptable. However, critical failure as bulk fracture may become a future problem since marginal disintegration was detected in 77% of the restorations from microscopic and macroscopic perspectives.