Thesis (M.Sc.) - Cairo University - Faculty of Oral and Dental Medicine - Department of Prosthodontics

All ceramic restorations surpass porcelain fused to metal restorations in esthetics and biocompatibility. Previously, it was used with caution in the posterior area due to its inherent weakness, but nowadays with the introduction of zirconium oxide, the material was used frequently and successfully in the posterior area. Zirconia frameworks undergo several critical steps to achieve a mechanically and biologically acceptable restoration. Milling process is considered as a crucial step contributing directly in marginal and internal accuracy. This study was done to evaluate the effect of three different construction techniques on the marginal and internal fit for three unit zirconia frameworks. Recent advances in ceramic materials and introduction of CAD/CAM technology was claimed to improve the fitting quality of restorations.The samples were divided in to three groups; each group consisted of five zirconia frameworks. The first group was milled using a CAD/CAM technology, the second group was fabricated by digitization of wax patterns (CAM technique), and the last group was constructed using copy-milling technique. Each group was evaluated for marginal fit using a stereomicroscope at 10X magnification at different points on all aspects, and digital image analysis software. Internal fit measurements were done using silicone elastomeric material, which is sectioned into four quadrants by a razor blade and examined under the same stereomicroscope and software (replica technique). The results were tabulated and statistically analyzed revealing that CAD/CAM showed the least marginal and internal gap compared with the wax digitization (CAM) and copy milling techniques. Wax digitization showed better internal fit than copy milling, whereas both techniques showed similar marginal fit

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