الفهرس 
Title: Evaluation of the fracture strength of Acetal and Poly-methyl methacrylate as a temporary restoration for mandibular implant supported fixed denture: (An In-vitro study)
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Abstract
Aim: The aim of this in-vitro study was to evaluate the fracture strength of temporary fixed dentures made from Acetal on four mandibular implants compared to PMMA regarding the fracture load and fracture pattern. Methodology: The present study was conducted on 6 temporary fixed dentures made from same design on CAD software by milling from Acetal and PMMA blocks; 3 from each group.These fixed dentures were cemented on the same mandibular model containing 4 implants alternatively. Each fixed restoration was tested by applying load from a universal testing machine using a T shaped load applicator at cross-head speed of 5mm/min. The load at failure manifested by an audible crack and confirmed by sharp DROP at load-deflection curve recorded using the computer software. The load required to fracture was recorded in Newton. All these parameters were subjected to statistical analysis. Results: The highest mean value was found in (Acetal) (5366.67 ± 10.69)N, the lowest mean value was found in (PMMA) (1128.00 ± 13.89)N with a statistical significant difference between the 2 groups. Also the fracture pattern in the PMMA group was more catastrophic. Conclusions: Acetal showed to be stronger and withstands higher stress than the PMMA when used at the cantilevered part of the prosthesis with more favorable pattern of failure