Search

Purpose to compare fracture resistance of endodontically treated teeth restored with different lengths of fiber posts.Materials and methods: Thirty- two freshly extracted sound mandibular premolars of approximate sizes, were mounted centrally and vertically in 12 x 12 x 20 mm acrylic block. Then, decoronated 2 mm above the cemento-enamel junction and were endodontically treated.Teeth were randomly divided between 4 main groups (n= 8). For all groups, post holes were prepared (group A; post hole less than the crown length (3 mm), group B; post hole equal to the crown length (5 mm), group C; post hole half of the root length (7 mm), group D; post hole 2/3 of the root length (9 mm). Posts were cemented using self-adhesive resin cement. Using core former and light-cured core composite, cores for all specimens were built. A 0.5 mm finish line was prepared with 2 mm ferrule, to receive metal coping. Using universal testing machine, axial loadwas applied at crosshead speed of 0.5 mm/min, parallel to long axis of the tooth until failure.Results: Group D scored the highest mean fracture resistance values (2670 ± 597.37 N) followed by Group A (2668 ±316.67 N) and Group B (2609 ±523.15 N). Group C scored the lowest fracture resistance values (2517 ±464.35 N). One-way ANOVA revealed no significant difference between groups (P=0.9). Chi-squre test also revealed no significant difference in restorability between the studied groups. (P=0.2).Conclusions: The tested post lengths had no significant effect on fracture resistance of endodontically treated teeth. Posts having radicular lengths equal to half of the root, showed the most non-restorable fracture pattern among all tested groups.

Purpose: To compare the translucency and fracture resistance of crowns fabricated using 3 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. After scanning the resin dies, 10 ultratranslucency monolith zirconia (UTZ) crowns and 10 supertranslucency monolith zirconia (STZ) crowns were milled and sintered according to manufacturer directions. The same premolar was further prepared to a 0.6mm chamfer finish line, and 10 resin dies were constructed and scanned using same technique to perform ten IPS e.max crowns which were milled accordingly and sintered according to manufacturer directions. All specimens were tested for translucency using spectrophotometer (Nippon Densmoku industries). 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, at the central fossa. Results: Viewing the mean of translucency between studied groups, group STZ scored the highest TP (21.03±4.41), followed by group UTZ (19.42±4.31), then group IPS e.max (19.29±4.49). Regarding mean fracture strength, group UTZ scored the highest value (1009.91±360.20 N) followed by group STZ (847.18±329.92 N) then group IPS e.max (821.51±175.69 N). 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.