Objective:The purpose of this in vitro study was to evaluate the effect of different implant prosthetic designs with two restorative materials on biomechanical behaviour using strain gauge analysis. Material and Methods: 6 different screw-retained implant restorations were designed and fabricated using a CAD/CAM system. These implants were divided into three main groups according to each design: group FB (fixed bridge); CB (cantilever bridge); SC (separate crowns). Each group was divided into two subgroups according to their restorative material: subgroup I -ultra translucent multi-layered zirconia (Kuraray Noritake Dental Inc, Japan); subgroup II -a combination of PEEK framework (BioHPP, Bredent, GmbH & Co.KG, Germany) and zirconia crowns (ultra-translucent multi-layered zirconia, Kuraray Noritake Dental Inc, Japan). Each subgroup was subjected to a vertical load of 100 N and their biomechanical behaviour was evaluated using a strain gauge (Kyowa, Japan) with a resistance of 120 Ω, length of 1 mm and width of 2.4 mm. For the implants, two strain gauges were positioned buccally and lingually, parallel to the long axis of the implant. For the restoration, two strain gauges were positioned buccally and lingually in the middle of it. The results were analyzed using three-way analysis of variance (ANOVA), followed by serial two-way and one-way ANOVAs at each level of the study, followed by Tukey's post hoc test P-values were adjusted for multiple comparisons using BENFORRONI correction and the significance level was set at P ≤ 0.05 for all tests. Results: FB showed the lowest strain values out of all 3 design groups. Moreover, the combination of PEEK and zirconia showed strain values smaller than full zirconia. The highest mean strain value was recorded in CB at 299.50 while the lowest mean strain peak value was recorded in group FB (74.50). The highest strain peak was recorded in CB subgroup I (3901.0 ± 195.91) and the difference had statistical significance (P-value < 0.01). Conclusion: the fixed bridge designed with PEEK framework and zirconia crowns was found to be more favorable in restoring the posterior edentulous area regarding strain measurements on the level of prosthetic components, implant and bone level.

Objective: Evaluate the effect of Implant prosthetic designs and restorative material on the stress concentration of 3-unit implant-supported restoration with two restorative materials. Material and Methods: Six different screw-retained prostheses models were virtually designed and divided according to design: fixed bridge (FB), cantilever bridge (CB), and separate crowns (SC). Then, each model was also divided into two subgroups according to the material: Ultra-translucent multi-layered zirconia (Kuraray Noritake Dental Inc., Japan); or a combination of PEEK (Polyetheretherketone) framework (BioHPP, Bredent, GmbH & Co., KG, Germany) and zirconia (ZR) crowns (ultra-translucent multi-layered zirconia, Kuraray Noritake Dental Inc., Japan). A vertical load of 100 N was applied statically perpendicular to the central fossa of each crown. The von-Mises stress was computed using Solidworks software (SolidWorks Corp, Massachusetts, USA), based on the physical parameters of the materials. Results: FB showed the lowest von Mises stress values out of all 3 design models. Moreover, the combination of PEEK and zirconia showed strain values smaller than full zirconia. The highest von Mises stress value was recorded in CB with the zirconia subgroup at (1098 MPa) while the lowest von Mises stress value was recorded in FB with combined PEEK and zirconia subgroup at (190 MPa). Conclusion: For three-unit implant supported restorations, the use of PEEK framework and zirconia crowns was found to be more favorable biomechanically regarding the prosthetic components, implant and bone stresses.

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