Purpose: To evaluate whether 5 × 5 mm dental implants with a novel nanostructured calcium-incorporated titanium surface could be an alternative to at least 5 × 10 mm-long implants placed in bone augmented with bone substitutes in posterior atrophic jaws.
Materials and methods: Forty 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 × 5 mm implants or one to three at least 5 × 10 mm-long implants in augmented bone at two centres. Mandibles were vertically augmented with interpositional bovine bone blocks and resorbable barriers and 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. Outcome measures were prosthesis and implant failures as well as any complication.
Results: Patients were followed to 4 months post-loading with the exception of one patient who underwent mandibular augmentation and had multiple complications at and after grafting, and subsequent graft failure, who did not want to go ahead with the treatment. This case was considered a complete failure. There were no statistically significant differences in prosthesis and implant failures. In mandibles, apart from the complete graft failure, one 5 × 10 mm implant failed at placement of the provisional prosthesis. In maxillae, one 5 × 5 mm implant failed with its provisional crown 3 months after loading. All complications occurred before loading. Significantly more intra- and postoperative complications occurred at both mandibular and maxillary grafted sites: 16 augmented patients were affected by complications versus 8 patients treated with short implants in the mandible (P = 0.022; difference in proportion = 0.40; CI 95% 0.12 to 0.68), and 5 sinus-lifted patients versus none treated with maxillary short implants (P = 0.047; difference in proportion = 0.25; CI 95% 0.06 to 0.44).
Conclusions: Short-term data (4 months after loading) indicate that 5 × 5 mm implants achieved similar results compared to longer implants placed in augmented bone. Short implants might be a preferable choice to bone augmentation especially in posterior mandibles since the treatment is faster, cheaper and associated with less morbidity. However, 5 to 10 years of post-loading data are necessary before making reliable recommendations.