Comparison of force distribution with finite element stress analysis in multi-unit monolithic zircon bridges fabricated on Hex and Non-hex titanium-base abutment

Knowledge about the stress value created by the use of hex and non-hex abutments in multi-unit implant supported restorations in the anterior maxillary region on the implant system and surrounding bone tissue is insufficient. The aim of this study was to evaluate the stresses on the implant, abutment and bone when hex and non-hex abutments are used with different combinations in multi-unit monolithic zirconia bridges on implants. For this purpose, maxillary partially edentulous bone model was created from tomography data for finite element stress analysis. Six unite monolithic zirconia bridges on three implants were designed for the 13, 11 and 23 numbered teeth. Five models were created in which hex and non-hex abutments were used in different combinations. In each model, a total force of 300 N was applied to each tooth at an angle of 45° in the palatolabial direction from the cingulum region of the restorations. Maximum and minimum principal stress values in cortical and trabecular bone, Von Mises stress values on implant neck and abutments were calculated. The maximum principal stress values in the cortical bone range from 3,43 to 30,82 MPa, and the minimum principal stress values range from -4,29 MPa to -11,39 MPa. Maximum principal stress values for trabecular bone range from 1,29 to 1,96 MPa, and minimum principal stress values range from -0,47 MPa to -0,79 MPa. When Von Mises stresses are examined, values between 56,70-98,97 MPa are obtained for the implant neck, while the stress values at the abutments are in the range of 73,50-123,07 MPa. Similar stress values on cortical and trabecular bone was calculated for hex and non-hex abutment systems in platform-switch conical connection implants. Hex abutments had higher stresses on the implant neck, while lower values were observed on the abutments.