A 5-year randomized controlled clinical trial comparing 4-mm ultrashort to longer implants placed in regenerated bone in the posterior atrophic jaw.

BACKGROUND: Short implants (up to 5-mm long) have shown good results when compared to longer implants placed in augmented bone. PURPOSE: To evaluate if 4-mm ultrashort implants could also be an alternative to bone augmentation in the severely atrophic posterior jaws. The primary aim of the study was to compare implant survival rates between study groups. MATERIALS AND METHODS: Eighty partially edentulous patients with posterior atrophic jaws (5-6 mm of bone above the mandibular canal and 4-5 mm below the maxillary sinus) were included: 40 patients in the maxilla and 40 in mandible. The patients were randomized to receive one to three 4-mm ultrashort implants or one to three implants at least 10-mm long in augmented bone. Results are reported 5 years after loading with the following outcome measures: implant and prosthetic failures, complications and peri-implant marginal bone level changes. RESULTS: Thirty-two complications were reported for the control group in 18 patients versus 13 complications in 10 patients in the test group, the difference being not statistically significant (p = 0.103). In the augmented group, 12 implants failed in 6 patients versus 7 short implants in 6 cases, and 9 prostheses failed in the control group while 4 in the test one, without statistically significant differences (p = 1.000 and 0.363, respectively). At 5 years after loading, short implants lost on average 0.58 +/- 0.40 mm of peri-implant marginal bone and long implants 0.99 +/- 0.58 mm, the difference was statistically significant (p = 0.006). CONCLUSION: Four-millimeter ultrashort implants showed similar if not better results when compared to longer implants placed in augmented jaws 5 years after loading. For this reason, their use could be in specific cases preferable to bone augmentation since the treatment is less invasive, faster, cheaper and associated with less morbidity. However, longer follow-ups and larger trials are needed.