This study aims to test the combined effects of different loading protocols and surgical approaches on clinical and patient-reported outcome measures (PROMs) following the use of four mini implants for mandibular overdenture retention.~Main study hypotheses:~There are significant improvements in PROMs following implant intervention compared to baseline measures;~Immediately loaded mini implants have similar failure rates compared to mini implants receiving a delayed 6-week protocol;~Flapless surgery has similar post-insertion outcomes compared to flapped surgery.~Statement of clinical relevance:~Mini implants are an alternative to standard implants for overdentures. They are suitable for insertion in narrow ridges, are less invasive, simpler, less costly, and faster to perform, and are especially advantageous for older and frail patients who would benefit from more conservative and less burdensome treatments. Although previous studies reported favorable outcomes regarding patient oral comfort and function, there is a need for implant/attachment systems with higher predictability on implant survival and retention performance in the long-term. This study aims to provide clinical evidence on the newly developed 2.4mm one-piece TiZr mini implant with a miniaturized carbon-based coating attachment.~Methods:~This is a randomized clinical trial using a factorial design, to test the effectiveness of a mandibular overdenture retained by four mini implants. Participants will be randomized using a 2×2 factorial design: immediate/delayed loading (factor 1) and flapless/flapped surgery (factor 2). New conventional complete dentures will be provided as the baseline treatment. Next, eligible participants will be those who completed a 6-month period of denture usage, and are in need of implants to improve the function of the mandibular denture. Imaging exam should present a minimum of 5.4 mm of ridge width in the interforaminal region (recommended for flapless surgery).~Included subjects to take part in the RCT will be randomized to the treatment groups according to the combined study factors - loading protocols: immediate (IL) or delayed (DL); and surgical approaches: flapless (FLS) or flapped (FPS) surgery. Hence, the combined factors will results in four groups:~IL/FLS (Group I)~IL/FPS (Group II)~DL/FLS (Group III)~DL/FPS (Group IV) Considering the patient's perspective this study design assumed a worst protocol (delayed and flapped - Group IV) and a best protocol (flapless and immediate - Group I) and two other intermediary conditions (flapped/immediate and flapless/delayed).~All participants will receive four Straumann® Mini Implant System (one-piece Tissue Level implants) with an Optiloc® prosthetic connection and PEEK matrix inserts. Surgery will follow the workflow for the surgical procedure for the Straumann® Mini Implant System concerning preoperative planning, implant bed preparation and implant insertion. For the prosthetic procedures, we will perform a chairside incorporation of the retentive inserts to convert the existing well-fitting and well-functioning lower denture into an overdenture with the Optiloc® Retentive System/Straumann® Mini Implants.~Outcomes will include short-term outcomes (Patient perceived burdens in surgery, postoperative swelling and pain, consumption of analgesics and surgical time) and long-term - 1-year (implant survival and success, peri-implant marginal bone level changes, PROMs, retention force, prosthodontic events) outcomes. Sample size calculation resulted in a total of 74 participants, 18 in each of the four groups. Data analysis will include descriptive and bivariate analyses, Kaplan-Meier curves and regression models using Generalized Estimating Equations (GEE) for longitudinal data.
This study aims to test the combined effects of different loading protocols and surgical approaches on clinical and patient-reported outcome measures (PROMs) following the use of four mini implants for mandibular overdenture retention.~The main study hypotheses are:~There are significant improvements in PROMs following implant intervention compared to baseline measures;~Immediately loaded mini implants have similar failure rates compared to mini implants receiving a delayed 6-week protocol.~Flapless surgery has similar post-insertion outcomes compared to flapped surgery.