6-mm-short and 11-mm-long implants compared in the full-arch rehabilitation of the edentulous mandible: A 3-year multicenter randomized controlled trial.

OBJECTIVE: The aim of this multicenter parallel-group randomized controlled trial is to compare 6-mm-short with 11-mm-long implants in the rehabilitation of totally edentulous mandible in a completely comparable clinical situation, from anatomical, surgical, and prosthetic point of view. MATERIAL AND METHODS: Thirty patients were selected in three study centers to receive a fixed full-arch mandibular rehabilitation supported by five inter-foraminal implants. Patients were randomly allocated, at the time of surgery, half to the test group (6-mm-long implants) and half to the control group (11-mm-long implants). No bone augmentation procedure was performed. After 3 months, a screw-retained full-arch prosthesis with distal cantilevers was positioned (baseline). Peri-implant marginal bone level change (MBLc), implant and prosthesis survival rate, and biological/technical complications were evaluated after 1 and 3 years. RESULTS: Thirty subjects (150 implants) were evaluated after 1 year and 28 (140 implants) after 3 years. No implant or prosthesis loss occurred. No significant inter-group difference for biological/technical complications was registered. No statistically significant (p > .025) intra-group or inter-group difference in the mean MBLc values was registered. The mean MBLc was 0.01 +/- 0.19 mm and -0.04 +/- 0.21 mm at 1 year, and -0.10 +/- 0.24 mm and 0.02 +/- 0.25 mm at 3 years (test and control groups, respectively). CONCLUSIONS: 6-mm-short implants may be a reliable option when used in the rehabilitation of total edentulous mandibles. These results need to be confirmed by longer follow-up data from well-designed randomized controlled clinical trials.