Posterior atrophic jaws rehabilitated with prostheses supported by 5 × 5 mm implants with a novel nanostructured calcium-incorporated titanium surface or by longer implants in augmented bone. Preliminary results from a randomised controlled trial

Purpose: To evaluate whether 5 × 5 mm dental implants with a novel nanostructured calciumincorporated titanium surface could be an alternative to implants at least 10 mm long placed in bone augmented with bone substitutes in posterior atrophic jaws. Materials and methods: A total of 40 patients with atrophic posterior (premolar and molar areas) mandibles having 5 to 7 mm of bone height above the mandibular canal and 40 patients with atrophic maxillae having 4 to 6 mm below the maxillary sinus, were randomised according to a parallel group design to receive one to three 5 mm implants or one to three at least 10 mm-long implants in augmented bone at two centres. All implants had a diameter of 5 mm. Mandibles were vertically augmented with interpositional bovine bone blocks and resorbable barriers. Implants were placed after 4 months. Maxillary sinuses were augmented with particulated porcine bone via a lateral window covered with resorbable barriers and implants were placed simultaneously. All implants were submerged and loaded after 4 months with provisional prostheses. Four months later, definitive screw-retained or provisionally cemented metal-ceramic or zirconia prostheses were delivered. Patients were followed up to 1 year post-loading and the outcome measures were prosthesis and implant failures, any complications and peri-implant marginal bone level changes. Results: One maxillary grafted patient dropped out before the 1-year evaluation. In mandibles, 1 grafted patient did not want to go ahead with the treatment because of multiple complications and graft failure, and another grafted patient did not receive his prostheses due the loss of 2 implants. In maxillae, one 5 × 5 mm implant failed with its provisional crown 3 months post-loading. There were no statistically significant differences in prostheses and implant failures. Significantly more complications occurred at both mandibular and maxillary grafted sites: 17 augmented patients were affected by complications versus 8 patients treated with short implants in the mandible (P = 0.0079; difference in proportion = -0.45; 95% CI -0.67 to -0.15), and 5 sinus-lift patients versus none treated with maxillary short implants (P = 0.047; difference in proportion = -0.25; 95% CI -0.44 to -0.06). Patients with mandibular short implants lost on average 0.94 mm of peri-implant bone at 1 year and patients with 10 mm or longer mandibular implants lost 1.03 mm. Patients with maxillary short implants lost on average 0.87 mm of peri-implant bone at 1 year and patients with 10 mm or longer maxillary implants lost 1.15 mm. There were no statistically significant differences in bone level changes up to 1 year between short and longer implants in maxillae (mean difference -0.28 mm, 95% CI -0.56 to 0.01, P = 0.051) and in mandibles (mean difference -0.09 mm, 95% CI -0.26 to 0.08, P = 0.295).