In vivo Investigation of Disintegration Mechanism of Ceramic Inlays.

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The quality of fired ceramic inlay restorations consisting of a feldspathic porcelain system (G-Cera Cosmotech II, GC Co., Tokyo, Japan) after 8 years was evaluated in vivo. A total of 45 fired ceramic inlays were placed in 25 patients, and all restorations were evaluated at the time of placement, and at 6 months and 1, 2, 4, 6 and 8 years after placement using modified U.S.P.H.S.criteria. Replicas made 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 82% of the fired ceramic inlay restorations at 8 years (Kaplan-Meier method). Marginal fracture was detected in 11 restorations (22%) including bulk fracture in five (11%). Marginal discoloration and recurrent caries were observed in 14 (31%) and three (7%) restorations, respectively. The SEM evaluation disclosed marginal microfracture in 77% of the restorations, wear loss of the restoration in 36%, and w … More ear of resin cement along margin in 74% at 8 years. No significant difference was observed in the incidence of each of these three characteristics between molars and premolars ( Mann-Whitney test, p<0.05). This longitudinal 8-year clinical observation suggested that fired ceramic inlay restorations are clinically acceptable.Marginal disintegration of ceramic inlays is a problem which should be urgently addressed, because it will become a critical cause of failure as a bulk fracture. The quantitative change of the marginal area of ceramic inlays was determined in vivo. Replicas of 12 premolars restored with ceramic inlays were measured quantitatively from the time of placement to eight years after restoration. An accurate CCD optical laser scanner was employed for morphological measurement of occlusal surface of restorations. Quantitative changes at the marginal area were computed by longitudinal superimposition of the cross sections with a picture analyze software. Factors which had significant influence on the quantitative change were analyzed with the Mann-Whitney test at a 95% level of confidence. The quantitative marginal changes of premolars restored with ceramic inlays for eight years were 465×10^2μm^2 at functional cusp area and 207×10^2μm^2 at non-functional cusp area. There were significant differences in marginal disintegration between functional and non-functional cusp areas. In vivo marginal disintegration of ceramic inlays was first measured quantitatively. Occlusal force may have significant effect on the marginal disintegration of ceramic inlays. Less