Three-year results from a randomised controlled trial comparing prostheses supported by 5-mm long implants or by longer implants in augmented bone in posterior atrophic jaws.

BACKGROUND: In many clinical situations it is not possible to place dental implants of ‘adequate length’ because there is less than 8 mm of residual vertical bone height. Clinicians are faced with the dilemma of whether to augment the bone or to place short implants having an intrabony length of 8 mm or less. Augmentation procedures are more technically demanding and therefore require skilful operators, as they can be associated with significant postoperative morbidity and complications, and can be more expensive and may require longer times. Short implants could be a simpler, cheaper and faster alternative if they could provide similar clinical outcomes to longer implants placed in augmented bone. AIM/HYPOTHESIS: To evaluate whether 5-mm short dental implants could be an alternative to augmentation with anorganic bovine bone and placement of at least 10-mm long implants in posterior atrophic jaws. MATERIAL AND METHODS: Fifteen patients with bilateral atrophic mandibles (5–7 mm bone height above the mandibular canal) and 15 patients with bilateral atrophic maxillae (4–6 mm bone height below the maxillary sinus), and bone thickness of at least 8 mm, were randomised according to a split-mouth design to receive one to three 5-mm short implants or at least 10-mm long implants (MegaGen Implant, Gyeongbuk, South Korea) in augmented bone. Mandibles were vertically augmented with interpositional bone blocks and maxillary sinuses with particulated bone via a lateral window. Implants were placed after 4 months, submerged and loaded, after another 4 months, with provisional prostheses. Four months later, definitive provisionally cemented prostheses were delivered. Outcome measures were: prosthesis and implant failures; any complication and peri-implant marginal bone level changes. RESULTS: Three years after loading 2 patients dropped out. Three prostheses failed in the short implant group vs. none in the long implant group. In mandibles, 1 long implant failed vs. 2 short implants in 1 patient. In maxillae, 1 long implant failed vs. 3 short implants in 2 patients. There were no statistically significant differences in the failures. Eight patients had 13 complications at short implants and 11 patients had 13 complications at long implants. There were no statistically significant differences in complications (P = 0.63, difference = 0.10, 95% CI from 0.22 to 0.42). Three years after loading in patients with mandibular implants the difference in terms of peri-implant marginal bone loss was not statistically significant (difference = 0.24 mm; 95% CI 0.01, 0.49 P = 0.059). In maxillae, patients lost on average 1.02 mm at short implants and 1.54 mm at long implants. This difference was statistically significant (difference = 0.41 mm; 95% CI 0.21, 0.60, P = 0.001). CONCLUSIONS AND CLINICAL IMPLICATIONS: Three years after loading, 5-mm short implants achieved similar results as longer implants in augmented bone. Short implants might be a preferable choice to vertical bone augmentation, especially in mandibles, since the treatment is faster and cheaper, however there are still insufficient data on the long-term prognosis of short implants.