الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Objective: Recently, minimal invasive preparations with less invasive finish line and reduced ceramic thickness are required. The aim of this study was to evaluate the fracture resistance and failure modes of three-units fixed dental prostheses (FDPs) made of two ceramic systems fabricated with two preparation designs using different manufacturing procedures. Materials and methods: Ni-Cr master model was made with missing mandibular left central to fabricate three-unit FDPs with mandibular lateral and central abutments. A total of 28 FDPs were divided into two main groups according to preparation design. 14 FDPs for group H (Horizontal): abutments with long chamfer finish line and 14 FDPs for group V (Vertical) abutments with feather edge finish line. Each main group was subdivided into two subgroups according to the material used. group C (Celtra Press) zirconia-reinforced glass ceramics and group K (Katana) monolithic zirconia. After cementation on Ni-Cr master model with self-adhesive resin cement, all specimens subjected to thermal cycling and mechanical loading and then loaded until fracture. Failure types were evaluated using Scanning Electron Microscope (SEM). Results: There was no statistical significant difference of fracture resistance between horizontal and vertical preparations in Celtra press group and Katana group. However, when comparing the fracture resistance of horizontal preparation of both groups there was high statistically significant difference. Furthermore, when comparing the fracture resistance of vertical preparation of both groups there was also a high statistically significant difference. Conclusions: Vertical preparation design represents a promising alternative to horizontal type. Both zirconia groups (Katana) had greater fracture resistance than the same groups of zirconia reinforced lithium silicate (Celta prss). Zirconia reinforced lithium silicate groups showed more favorable fracture than zirconia groups tested using both preparation design.