effects of length and inclination of implants on terminal abutment teeth and implants in mandibular cl1 removable partial denture assessed by three-dimensional finite element analysis

objectives: this study sought to assess the effects of length and inclination of implants on stress distribution in an implant and terminal abutment teeth in an implant assisted-removable partial denture (rpd) using three-dimensional (3d) finite element analysis (fea).   materials and methods: in this in vitro study, a 3d finite element model of a partially dentate mandible with a distal extension rpd (derpd) and dental implants was designed to analyze stress distribution in bone around terminal abutment teeth (first premolar) and implants with different lengths (7 and 10 mm) and angles (0°, 10° and 15°). results: stress in the periodontal ligament (pdl) of the first premolar teeth ranged between 0.133 mpa in 10mm implants with 15° angle and 0.248 mpa in 7mm implants with 0° angle. the minimum stress was noted in implants with 10mm length with 0° angle (19.33 mpa) while maximum stress (25.78 mpa) was found in implants with 10mm length and 15° angle. in implants with 7 mm length, with an increase in implant angle, the stress on implants gradually increased. in implants with 10 mm length, increasing the implant angle gradually increased the stress on implants. conclusion: not only the length of implant but also the angle of implantation are important to minimize stress on implants. the results showed that vertical implant placement results in lower stress on implants and by increasing the angle, distribution of stress gradually increases.