Effect of implant position on clinical outcomes of two implant overdentures: a 3-year randomized clinical trial

BACKGROUND: Reviewing the literature, the optimal implant position for 2-implant retained mandibular overdentures, which would be associated with improved peri-implant tissues, higher retention values, and better patient satisfaction, remains uncertain. The study was designed to assess the effect of the implant position of two implant-retained mandibular overdentures on clinical outcomes (peri-implant soft tissue health, bone loss, retention, and patient satisfaction). MATERIALS AND METHODS: Ninety edentulous patients with unsatisfactory retention of their mandibular conventional dentures were included in this study and received 2-implant mandibular overdentures with Locator attachments. The patients were randomly divided into three groups based on the positions of the implants. Group LA (implants in lateral incisor positions), Group CA (implants in the canine positions), and Group PM (implants in the premolar positions). Changes in the peri-implant soft tissue health (plaque, gingival scores, and probing depth) and the retention values of overdentures were evaluated at prosthesis insertion (T0), 6 months (T6), and 12 months (T12) after insertion. The peri-implant marginal bone loss changes were evaluated one year (T12), 2 years (T24), and three years after insertion (T36). A visual analog scale (VAS) assessed patient satisfaction for conventional dentures (CD), LA, CA, and PM at T6. RESULTS: At T6 and T12, the highest plaque and gingival scores were noted with the PM, followed by LA, and the lowest scores were observed with CA. For all observations, the highest pocket depth was noted with PM, followed by CA, and the lowest pocket depth was noted with LA. CA and PM showed significantly higher bone loss compared to LA. The highest retention forces were exhibited by PM, followed by CA, and the lowest retention values were noted with LA. Regarding retention, stability, occlusion of the mandibular prosthesis, and ease of chewing, the PM group had the greatest patient satisfaction, then CA and LA. The lowest satisfaction scores were noted with CD. CONCLUSIONS: In selecting the implant position for two-implant mandibular overdentures, it is crucial to balance several key clinical outcomes. The chosen location for the implants should effectively prioritize bone preservation, the health of peri-implant soft tissues, retention, and overall patient satisfaction. Positioning the implants near the lateral incisors is advantageous for minimizing bone loss, while placement near the canines supports optimal soft tissue health. Conversely, positioning them near the premolars maximizes retention and enhances patient satisfaction. CLINICAL TRIAL REGISTRY NUMBER: (NCT06166316) (12/13/2023).