Comparing 4-mm dental implants to longer implants placed in augmented bones in the atrophic posterior mandibles: One-year results of a randomized controlled trial.

BACKGROUND: Short implants have been proposed as an alternative for the rehabilitation of atrophic edentulous areas. PURPOSE: To evaluate the efficacy of 4-mm implants vs longer implants in the atrophic posterior mandibles. MATERIALS AND METHODS: Eleven patients with bilateral atrophic mandibles were rehabilitated with two to four 4-mm implants and 10 or 8-mm long implants in augmented bone using Guided Bone Regeneration procedure. One side of the mandibles was randomly allocated to vertical augmentation with mixed autogenous bone and allograft. Implants were placed in both sides of the mandible after 6 months, and loaded after another 2 months. Subsequently, implant and prosthesis failures, marginal bone levels changes, and any complication were evaluated after 1-year follow-up. RESULTS: In this study, one patient dropped out and no failures occurred. However, 4-mm implants loss of 0.30 +/- 0.34 mm peri-implant marginal bone and long implants loss of 0.47 +/- 0.54 mm marginal bone were observed after 1-year of follow-up. The difference between the two groups was not statistically significant (difference = -0.16 +/- 0.68 mm; P = 0.46). Eight complications occurred in five augmented sites of the patients, and no complication was found to occur in the short implants sites. CONCLUSIONS: One-year after loading, 4-mm implants had similar outcomes as long implants in augmented bone. Therefore, short implants might be a feasible treatment in atrophic mandibles.