Mandibular Overdenture Retained by 1 or 2 Implants: a Cost-effectiveness Analysis

This randomized clinical trial alongside a cost-effectiveness analysis will include 48 edentulous individuals who meet eligibility criteria. New maxillary and mandibular dentures will be fabricated for all participants following a standardized protocol. Then, participants will be randomized into one of the treatment groups: mandibular overdenture retained by two implants group or single-implant mandibular overdenture group. Each participant allocated to the single-implant mandibular overdenture group will then receive a Straumann® Standard Plus SLActive® regular neck implant (Straumann 0.33.051S/052S/053S Institute Straumann AG, Basel, Switzerland) in the mandibular midline, and the mandibular overdenture retained by two implants group will receive two implants of the same specification, in the interphoramen region. A healing abutment will be connected and the implant will be allowed to heal for approximately 3 weeks. Then, a 3.4mm retentive titanium anchor abutment (Straumann 048.439, Institute Straumann AG, Basel, Switzerland) will be connected and tightened to 35 N.cm with a torque wrench. The matrix will be incorporated to the denture using self-curing acrylic resin and the patient will be instructed to keep the upper and lower dentures firmly occluded in the habitual position until the final polymerization of the resin. Outcomes (satisfaction with the dentures and oral health-related quality of life) will be measured at baseline and at the 6- and 12-month follow-up. Direct costs related to therapies in both groups will be identified, measured and valuated for one year after treatment. Incremental cost-effectiveness ratios will be estimated and graphically presented on cost-effectiveness planes. Sensitivity analysis on the most important assumptions will be performed in order to assess the robustness of the model.