A Cochrane review [Abstract] 1 included 13 studies with a total of 324 subjects. Three studies (n=106) dealt with horizontal and 10 studies (n=218) with vertical augmentation. Since different techniques were evaluated in different trials, only one meta-analysis could be performed. Two studies (n=100) evaluated whether vertical bone augmentation procedures are needed to allow placement of longer implants or whether shorter implants could be used instead; vertical augmentation of resorbed mandibles with inlay techniques resulted in more implant failures (OR 5.74, 95% CI 0.92 to 35.82; borderline significance p=0.06) and complications (OR 4.97, 95% CI 1.10 to 22.40) than simple placement of short implants. However, the long-term prognosis of shorter implants is yet unknown.
No significant differences were observed between various horizontal augmentation techniques (3 studies). When comparing various vertical bone augmentation techniques (8 studies) no statistically significant differences were observed with the exception of 3 trials which showed that more vertical bone gain could be obtained with osteodistraction than with inlay autogenous grafts (MD 3.25 mm, 95% CI 1.66 to 4.84), and with a bone substitute rather than autogenous bone in guided bone regeneration (MD 0.60 mm; 95% CI 0.21 to 0.99) in posterior atrophic mandibles, and that patients preferred a bone substitute block than a block of autogenous bone taken from the iliac crest (OR 0.03, 95% CI 0.00 to 0.64).
Comment: The quality of evidence is downgraded by study quality (unclear allocation concealment) and by imprecise results (few patients and wide confidence intervals).
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