The Effects of Different Framework Designs and Different Materials of Implant-supported Single Crowns After Aging

Objectives: To evaluate the effect of different abutment-framework designs and different layering materials on the fracture strength of implant-supported zirconia-based single crowns following artificial aging. Materials and methods: Seventy ti-base abutments (Conelog 4.3-0.8mm, C2242.4308, Camlog® Implant, Basel, Switzerland) were screwed onto dental implants (Conelog 4.3-11mm, C1062.4311, Camlog® Implant, Basel, Switzerland). Abutment-implant complexes were randomly divided into seven groups (n = 10) according to the design of the zirconia abutment and framework (VITA YZ T, VITA Zahnfabrik, Germany) as follows: uniform-thickness zirconia abutment and uniform-thickness zirconia framework layered with feldspathic porcelain (Group 1); layered with indirect composite material (Group 2); uniform-thickness zirconia abutment and anatomic design zirconia framework layered with feldspathic porcelain (Group 3); layered with indirect composite material (Group 4); anatomic design zirconia abutment and anatomic design zirconia framework layered with feldspathic porcelain (Group 5); layered with indirect composite material (Group 6); uniform-thickness zirconia abutment and monolithic zirconia crown (Group 7). All fabricated zirconia abutments were cemented on ti-base abutments, and then all crowns were cemented on ti-base-zirconia abutment complexes. All specimens were exposed to 10,000 thermal cycles between 5°C and 55°C and then tested for fracture strength. The data were statistically analysed using 3-way ANOVA and Bonferroni-corrected t tests (p≤0.05). Results: The mean fracture strength values of groups were found to be statistically different with a ranking from highest to lowest as follows: Group 7 > Group 5 > Group 3 > Group 1 > Group 6 > Group 4 > Group 2 (p0.05). Anatomical abutment and framework designs showed significantly higher strength compared to uniform abutment and framework designs regardless of layering material (p0.05). Porcelain-layered groups had significantly higher fracture strength values in comparison to the groups layered with indirect composite (p0.05). Conclusions: A framework design with anatomical form supported by an anatomical abutment design increases fracture resistance in implant-supported zirconia-based restorations. Indirect composite material and porcelain perform similarly to layering materials on zirconia frameworks. Fabricating monolithic zirconia crown onto zirconia abutment may be recommended for higher strength. Keywords: ti-base, zirconia, implant-supported, layering material, framework