Four mm-long versus longer implants in augmented bone in atrophic jaws: 1-year loading RCT results

BACKGROUND: Dental implants are used to replace missing teeth for rehabilitating edentulous patients. In many patients it is not possible to place “standard length” dental implants because of the crestal bone vertical resorption. Clinicians, therefore, are faced with the dilemma of whether to attempt an augmentation procedure or to place shorter implants. Short implants could be a simpler alternative if they could provide similar clinical outcomes to longer implants placed in augmented bone. AIM/HYPOTHESIS: The aim of this RCT was to compare the outcome of 4 mm-long implants with implants at least 10 mm-long placed in posterior jaws augmented either with a mandibular interpositional equine block or with a porcine-derived granular bone placed through a lateral window below the lifted maxillary sinus. MATERIAL AND METHODS: Forty patients with atrophic posterior mandibles having 5–6 mm bone height above the mandibular canal and 40 pa- tients with atrophic maxillae having 4–5 mm below the maxillary sinus, were randomised according to a parallel group design to receive one to three 4.0 mm-long implants or one to three implants, which were at least 10 mm-long, in augmented bone. All implants had a diameter of 4.0 or 4.5 mm. Mandibles were vertically augmented with interpositional equine bone blocks and resorbable barriers. Implants were placed 4 months after interpositional grafting. Maxillary sinuses were augmented with particulated porcine bone via a lateral window and implants were placed simultaneously. Four months later, screw-retained reinforced acrylic restorations were delivered, and then replaced after 4 months by definitive screw-retained metal-composite prostheses. Outcome measures included prosthesis and implant failures, any complication and peri-implant mar- ginal bone level changes. RESULTS: One mandible fractured and the patient did not want to go ahead with the treatment. Six implant from the augmented group failed versus five 4.0 mm implants from the short implant group. There were no statistically significant differences in implant failures (P (chi-square test) = 1.000) or prostheses failures (P (chi-square test) = 0.399). At mandibular sites, nine augmented patients were affected by complications versus one patient treated with short implants (P (chi-square test) = 0.003), with the difference being statistically significant. No significant dif- ferences were found for the maxillae: eight sinus lift patients versus three patients rehabilitated with maxillary short implants were affected by complications (P (chi-square test) = 0.077). The difference in peri-implant marginal bone loss was statistically significant in the mandibles (mean difference: −0.12 mm, P (ANCOVA) = 0.006), but not in the maxillae (mean difference: −0.02 mm, P (ANCOVA) = 0.711). CONCLUSIONS AND CLINICAL IMPLICATIONS: Four months after loading 4.0 mm-long implants achieved similar results, if not better, than longer implants in augmented jaws, but were affected by fewer complications. Short implants might be a preferable choice to bone augmentation, especially in mandi- bles, since the treatment is less invasive, faster, cheaper, and associated with less morbidity, however, 5- to 10-year post-loading data is necessary before making reliable recommendations.