6 mm short vs. 11 mm long inter-foraminal implants in the full-arch rehabilitation of edentulous non-atrophic mandibles: 5-year results from a multicenter randomized controlled trial.

OBJECTIVE
The aim of this multicenter parallel-group randomized controlled trial is to compare, in the same clinical scenario, 6 mm short with 11 mm long implants for the rehabilitation of completely edentulous non-atrophic mandibles.


MATERIALS AND METHODS
30 patients in three study centers received a fixed full-arch mandibular rehabilitation supported by five inter-foraminal implants, with no need for bone augmentation procedures. Patients were randomly allocated (1:1 ratio), at the time of surgery, to test (6 mm implants) or control group (11 mm implants). After 3 months a screw-retained full-arch prosthesis was positioned (baseline). Peri-implant marginal bone level change (MBLc, primary outcome) together with implant and prosthesis survival rate, and biological/technical complications (secondary outcomes) were evaluated up to 5 years.


RESULTS
27 patients were controlled at 5 years (3 drop-outs). No implant or prosthesis loss occurred. No significant inter-group difference for biological/technical complications (p>0.05, Fisher exact test), and no significant intra-group and inter-group difference in the MBLc values were registered (test -0.03 ± 0.17 mm and control -0.13 ± 0.32 mm at 5-years; p>0.025, one-sided Mann-Whitney U-test).


CONCLUSIONS
When used in comparable anatomic, surgical and prosthetic conditions, no difference in the clinical and radiographic outcomes between 6-mm and 11-mm implants was observed at 5 years of follow-up. Short implants showed to be a reliable option for the rehabilitation of completely edentulous non-atrophic mandibles. There is growing clinical evidence supporting the use of short implants, even in the case of non-atrophic sites.