Fracture resistance of all-ceramic and metal-ceramic inlays

Purpose: Metal-ceramic inlay designs were developed to determine if the est hetic qualities of all-ceramic inlays could be duplicated and at the same t ime improve their strength and stability. The objectives of this study were to: (1) compare the fracture resistance of metal-ceramic inlays with that of all-ceramic inlays; (2) determine the correlation between the degree of preparation taper and fracture resistance; and (3) determine the correlatio n between marginal gap width and fracture resistance. Materials and Methods : Inlay preparations were made on 60 Dentoform teeth, with 30 teeth allocat ed for metal-ceramic inlays and 30 teeth for all-ceramic inlays. Each group was further subdivided into 5-, 10-, and 20-degree taper preparations. Met al-ceramic inlays were fabricated using Goldtech Bio 2000 metal and Ceramco porcelain extending to the margin, while all-ceramic inlays were made from Empress II ceramic. Marginal gap widths were measured at six critical area s after fabrication. The load at failure was measured using an Instron Univ ersal Testing Machine. Results: The mean fracture load for all-ceramic inla ys and metal-ceramic inlays at 5, 10, and 20 degrees was 70 +/- 40 N, 48 +/ - 37 N, 33 +/- 7 N, and 40 +/- 23 N, 29 +/- 22 N, and 14 +/- 4 N, respectiv ely. The mean gap width was 105 mum and 126 mum for all-ceramic and metal-c eramic inlays, respectively. Conclusion: The mean fracture load for Empress inlays was significantly higher than that for metal-ceramic inlays. Inlays with a 5-degree taper were significantly more fracture resistant than thos e with a 20-degree taper. There was no relation between marginal gap width and fracture resistance.