Effect of Buccal Implant Inclination on Stresses Around Two-Implant-Retained Overdentures with Resilient Stud Attachments

Purpose: This study aimed to evaluate the effect of buccal implant inclination on stresses around twoimplant- retained overdentures with resilient stud attachments. Materials and Methods: Four acrylic models representing a mandibular edentulous ridge were constructed. For each model, two implants were placed at canine areas. Models were classified into four types according to the degree of buccal implant inclination: Group I (GI, 0 degrees), Group II (GII, 10 degrees), Group III (GIII, 20 degrees), and Group IV (GIV, 30 degrees). Overdentures were connected to the implants with Locator attachments. Regular light-retention inserts were used for all groups, and extended range inserts were also used for GIV (GIVext), making a fifth comparison group. Four strain gauges were bonded at the buccal, lingual, mesial, and distal surfaces of each implant to monitor the stresses during bilateral and unilateral load application. Results: Tensile stresses were recorded at distal and lingual gauges, and compressive stresses were recorded at mesial and buccal gauges for all groups. GIV recorded the highest stresses, followed by GIII, GII, GIVext, and GI. Distal position recorded the highest stresses, followed by lingual, mesial, and buccal. Nonloading side was associated with significantly higher stresses than loading side. Conclusion: The peri-implant stresses increase as the buccal implant inclination increases when resilient stud attachments are used for implant overdentures. Therefore, it is recommended to insert the implants parallel to each other to decrease peri-implant stresses. However, when buccal inclination is inevitable due to anatomical limitations, it should be limited to 10 degrees for standard nylon inserts, or extended range inserts are recommended. Keywords: implant, inclinations, Locator, overdenture, stresses