A Cluster-randomized Multicenter Trial Comparing OT-Equator® Versus Locator® Attachments to Retain an Early Loaded Implant Overdenture on Two or Three Implants

Study design: A cluster-randomized multicenter trial of parallel group design and two arms. Patients with complete edentulous mandible in needed of an implant retained overdenture, will be randomly clustered to receive two or three unsplinted implants. Afterwards, patients that have been randomized to receive two implants will be randomized to receive OT Equator® attachment (Rhein'83, Bologna, Italy) in the test group, or Locator® attachment (Zest Anchors LLC, Espandido, CA, USA) in the control group.

Patients will be selected and consecutively treated in 10 private and public (University) centers in Europe, between December 2017 and December 2018. This study will be conducted in accordance with the principles outlined in the Helsinki Declaration of 1964 for biomedical research involving human subjects, as amended in 2013, and will receive ethical approval by Ethical Committees of the various centers. Patients will be duly informed about the nature of the study. A written informed consent form for surgical and prosthetic procedures, as well as for the use of the clinical and radiological data, will be obtained for each patient. The present research will be registered in the Clinical trial.gov and the manuscript will be written according to the CONSORT guidelines.

Any healthy individual (ASA 1 and 2), aged 18 years or older at the time of enrollment, with complete edentulous mandible, or a failing dentition in the mandible, scheduled to receive an implant supported overdenture, will be considered eligible for the study. Exclusion criteria are the general contraindications to oral surgery, pregnancy or nursing, intravenous bisphosphonate therapy, alcohol or drug abuse, heavy smoking (≥ 20 cigarettes/day), radiation therapy to the head or neck region within the last five years, parafunctional activity, untreated periodontitis, and allergy or adverse reactions to the restorative materials.

Preoperative photographs, panoramic x-rays, and periodontal screening have to be obtained for initial screening and evaluation. Hopeless teeth (in the mandible) have to be extracted 3 months before implant placement and new prosthesis delivery. All of the patients will receive a temporary complete removable denture before implant placement, according to the respective functional and esthetic requirements. If the actual complete removable denture is judged accurate from both patients and clinician, it could be used as temporary solution.

On the day of the surgery, a single dose of an antibiotic (either 2 g of amoxicillin or 600 mg of clindamycin or 500 mg of azitromicin or claritromicin if allergic to penicillin) will be administered 1 h before implant placement (2017 AHA). Immediately before surgery, the participants will rinse with a 0.2% chlorhexidine mouthwash for 1 min. Local anesthesia preferred by the surgeon will be administered. Flapless, or a minimally invasive mucoperiosteal flaps will be elevated. Then, the patients will be randomly clustered to receive two or three unsplinted implants according to congealed indication contained in a close enveloped and derived from a pre-generated list. Afterwards, only the patients that will be randomized to receive two implants will be randomized to receive OT Equator® attachment (Rhein'83, Bologna, Italy) in the test group, or Locator® attachment (Zest Anchors LLC, Espandido, CA, USA) in the control group.