This study focuses on the comparison of different implant abutment connections configurations in implant supported screw retained fixed dental prostheses assessing their clinical and radiographic outcomes and to evaluate which implant abutment connection configuration have less biological and technical complications.

Study design: This study is designed as a parallel group randomized controlled trial with an allocation ratio of 1:1. The (PICO) study design: population will be patients from Jordan University Hospital aged 18 years or older, patients who will receive 2 internal connection dental implants to replace 3 posterior missing teeth in the mandible with a 3 unit screw-retained FDP with sufficient bone volume and controlled oral hygiene. The intervention group will receive a screw-retained FDP with conical engaging and non engaging abutment configuration, while the comparator group will a screw-retained FDP with both conical non engaging abutment configuration. The primary outcome is changes in marginal bone levels, and the secondary outcomes include technical and mechanical complications, biological complications, and patient satisfaction. Both groups will receive 2 internal connection implants in the posterior mandible in healed sites of at least 3 months (guided implant surgery). The surgical procedure will follow standardized protocols, with no variations between groups other than the types of implant abutment connections used. Blinded assessors will perform radiographic and clinical evaluations at designated follow-up visits: definitive loading, after 6 months of loading, after 2 years loading.