Thesis & Dissertations

Purpose: to compare the translucency and fracture resistance of crowns fabricated using three different ceramic materials. Materials and Methods: a human maxillary right premolar was prepared to a 0.4 mm chamfer finish line with 6 degrees convergence angle and 1.5 mm occlusal clearance. Using industrial silicon (Body Double, Smooth-On), a mold was poured to construct 20 identical resin dies using acrylic resin (vertex). After scanning the resin dies, 10 ultratranslucency monolith zirconia crowns and 10 supertranslucency monolith zirconia crowns were milled and sintered according to manufacturer directions.The same premolar was further prepared to a 0.6 mm chamfer finish line, and 10 resin dies were constructed and scanned using same technique. Ten IPS e.max crowns were milled accordingly and sintered according to manufacturer directions. All specimens were tested for translucency using spectrophotometer (Nippon Densmoku industries), against white and black colored resin dies. All specimens were then subjected to fracture resistance test using universal testing machine (The Testometric Company Limited) at cross head speed 0.5 mm/min with force direction 90 degrees angle to the occlusal table. Results: Viewing the mean of translucency between studied groups, group STZ (21.03±4.41) scored the highest TP followed by group UTZ (19.42±4.31) then group IPS e.max (19.29±4.49). Regarding mean fracture strength (Newton), group UTZ scored the highest value (1009.91±360.20) followed by group STZ (847.18±329.92) then group IPS e.max (821.51±175.69). One-way ANOVA revealed no significant difference between groups in either translucency (P=0.621) or fracture strength (P=0.328). Conclusions: The two tested hybrid ceramics could present an acceptable treatment option for fabricating monolith ceramic crowns. There was no significant difference in either translucency or fracture resistance between all tested groups. Key words: IPS e.max, ultratranslucency zirconia, supertranslucency zirconia, translucency, fracture resistance.