Thesis Submitted to Removable Prosthodontic Department, Faculty of Dentistry, Ain Shams University; In Partial Fulfillment of the Requirements for the Master Degree in Oral and Maxillofacial Prosthodontics

Abstract

wo identical acrylic models representing completely edentulous lower ridge were constructed to conduct this study. Four mini dental implants were placed in the symphysial region of the 1st acrylic model (model 1). Another Four mini dental implants were inserted at the same sites in the 2nd acrylic model (model 2). Two identical overdentures were constructed on these two models. The first overdenture was fitted to the mini dental implants of the 1st model using four ERA abutments with angle 0 degree. While the second overdenture was fitted to the mini dental implants of this model through four ERA abutments with angle 17 degrees. One strain gauge was installed vertically, 1mm on the distal aspect of the distal implant on each side. Posterior unilateral (vertical and oblique) and bilateral tissue ward loads were applied on the 1st molar tooth of each model using universal testing machine. Microstrains were recorded by the four channel strain meter during different loading applications. The results of this study revealed that, statistically significant higher stresses were transmitted to the distal implants of model 2 (with angled abutments) with vertical unilateral and bilateral loading. However, distal implants of model 1 (with straight abutments) received statistically significant higher stresses during oblique loading. This result suggests that angled abutments may be a suitable restorative option when implants are not placed in the ideal axial position.