Background: Two implant-retained overdenture is a minimum standard of treatment for edentulous mandible. This study aims to evaluate stress-distribution in 2-implant retained mandibular overdentures with implants placed at different positions and angulations.
Methods: The 3D models of mandible (using CBCT scan DICOM-files) and denture (using 3Shape intraoral scanner DICOM-files) were developed in Materialise-Mimics-Software. A 3D model of a dental implant (3.5 mm X 12 mm) and the Locator-male-attachment (4 mm) was developed in CAD-Solidworks-software. Two implants were inserted in each 3-D model of the mandible to investigate the effect of (i) implant positions (with different distances from midline (5, 10, 15, 20 mm), and (ii) implant angulations (with different distal-angulations (5/5, 10/10, 15/15, 0/5, 0/10, 0/15 degrees) at 10 mm distance from midline in ANSYS software under vertical load of 100N unilaterally and bilaterally on first molar. Maximum Von-Mises stresses and strain-values were recorded and analyzed.
Results: Highest stresses of 4.18 MPa (under unilateral loading) and 4.2 MPa (under bilateral loading) were observed in implants at 20 mm distance. All other implant positions showed stresses less than 2.46 MPa indicating increasing trend in stresses with increase in the distance. Highest stresses of 0.93 (unilateral loading) and 0.92 MPa (bilateral loading) were observed with implants at 15/15-degree angulations. For lesser angulations, the stresses were ranging from 0.05 to 0.87 MPa on implants.
Conclusions: Implants placed more posteriorly exhibit higher stresses compared to implants placed more anteriorly. Implants placed with greater angulations displayed higher stresses than implants placed with lesser angulations.