الفهرس 
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Abstract
Esthetics and minimally invasive procedures are two main concepts that patients and dentists seek for today; this increased the demand for a high esthetic and more conservative restorations that have high fracture resistance which could withstand the occlusal forces. This study was designed to compare the fracture resistance of all-ceramic zirconia ceramics fabricated by two different techniques (glass infiltrated and manual milling) with two different marginal designs (heavy chamfer and shoulder). An extracted first maxillary premolar was prepared with heavy chamfer margin (0.7 mm). Fourteen impressions were taken using polyvinylsiloxane impression material. The impressions were poured with epoxy resin to fabricate the dies. The same tooth was retrieved and heavy chamfer finish line was converted into shoulder one (1 mm). Another fourteen impressions were taken for the tooth prepared with shoulder finish line and another fourteen epoxy resin dies were fabricated. Fourteen zirconia copings were constructed by glass infiltrated technique and Fourteen zirconia copings were constructed by manual milling technique. All specimens were cemented on the epoxy resin dies using adhesive resin cement (multilink speed). Each specimen was mounted on a universal testing machine. The force was applied to the occlusal surface of the zirconia copings without veneers till fracture occurred. The cross-head speed was 0.5 mm/ min. Fracture load were recorded. Data were tabulated, statistically analyzed using Two-Way ANOVA test. Descriptive statistics of results revealed that the highest mean value of fracture resistance was for manually milling technique of zirconia copings with heavy chamfer finish line (1372.1±83.7N), while the lowest mean value was for glass infiltration technique with shoulder finish line (749.9±67.4N). Conclusions: Within the limitations of this in-vitro study the following conclusions could be obtained; 1.The heavy chamfer finish line is recommended than shoulder finish line in both the tested zirconia copings. 2.The fracture resistance of the zirconia copings constructed by manual milling technique is better than zirconia constructed by glass infiltrated technique.