This systematic review is aimed at evaluating the effectiveness of synthetic block materials for bone augmentation in preclinical in vivo studies. An electronic search was performed on Pubmed, Scopus, EMBASE. Articles selected underwent risk-of-bias assessment. The outcomes were: new bone formation and residual graft with histomorphometry, radiographic bone density, soft tissue parameters, complications. Meta-analysis was performed to compare new bone formation in test (synthetic blocks) vs. control group (autogenous blocks or spontaneous healing). The search yielded 214 articles. After screening, 39 studies were included, all performed on animal models: rabbits (n = 18 studies), dogs (n = 4), rats (n = 7), minipigs (n = 4), goats (n = 4), and sheep (n = 2). The meta-analysis on rabbit studies showed significantly higher new bone formation for synthetic blocks with respect to autogenous blocks both at four-week (mean difference (MD): 5.91%, 95% confidence intervals (CI): 1.04, 10.79%, p = 0.02) and at eight-week healing (MD: 4.44%, 95% CI: 0.71, 8.17%, p = 0.02). Other animal models evidenced a trend for better outcomes with synthetic blocks, though only based on qualitative analysis. Synthetic blocks may represent a viable resource in bone regenerative surgery for achieving new bone formation. Differences in the animal models, the design of included studies, and the bone defects treated should be considered when generalizing the results. Clinical studies are needed to confirm the effectiveness of synthetic blocks in bone augmentation procedures.

OBJECTIVE: The aim of this systematic review was to determine the most effective alveolar augmentation technique for vertical bone gain.
METHODS: A systematic search to select clinical trials and retrospective studies done on patients with reduced vertical bone height was conducted. The intervention of interest was autogenous block graft done compared to procedures such as distraction osteogenesis (DO), particulate grafting, block plus particulate grafting with titanium mesh, and tent pole technique in systematically healthy adult patients age 18 and older. The following electronic databases were explored: PubMed, CINAHL, and Dental and Oral Science. A supplementary manual search of published full-text articles from January 2005 to December 2017 was done using Google Scholar. Grey literature was also sought using greylit.org. The review protocol was registered at the Prospero registry (CRD # 42017072432). The risk of bias of the included studies was assessed using EPOC criteria. Meta-analysis was performed using Review Manager for studies with quantitative data on mean values of vertical bone gain and bone resorption achieved with various bone augmentation techniques. Random effect model was used. Heterogeneity among studies was evaluated using the I2 statistic.
RESULTS: A total of 2322 articles were found. After excluding the irrelevant papers, only 8 papers were finally selected for the detailed evaluation. Of these 8, 5 were clinical trials, and 3 were retrospective studies. Four studies were on DO, 2 on particulate grafting, 1 on autogenous block grafting plus particulate grafting, and 1 on tent pole grafting. The control group in all studies were autogenous block graft. Meta-analysis revealed no significant difference between DO and autogenous block grafting for vertical bone gain (mean difference 0.82 [-1.28, 2.91]). Similarly, no significant difference was observed in the 2 techniques for bone resorption (mean difference 0.38 [-0.23, 0.99]).
CONCLUSIONS: DO was not superior to autogenous block grafting for vertical bone augmentation. Both techniques were associated with a number of complications. There was no difference in the bone resorption observed in the 2 techniques. No conclusive results can be drawn on other techniques on account of limited data.

Autogenous intraoral block grafting is the gold standard augmentation technique for moderate-to-severe horizontal ridge deficiency. However, the graft undergoes variable resorption during healing that might jeopardize the outcome of the procedure. Several studies hypothesized that covering the graft with a membrane decreases the amount of graft resorption, but this effect is not established in the literature.
The objective of this study is to assess the clinical value of covering intraoral block grafts with membranes in horizontal ridge augmentation regarding graft resorption (primary outcome), graft success, net bone gain, and complications (secondary outcomes).
Till August 2017, the review team conducted an electronic search including PubMed, EMBASE, Cochrane, and LILACS databases; we also identified other articles through hand searching. The search terms included alveolar ridge augmentation, bone transplantation, block graft, guided bone regeneration, membranes, resorbable membrane, and nonresorbable membrane.
The review included human randomized controlled trials, controlled clinical trials, cohort studies, and case-control studies in English that compared membrane coverage to no membrane coverage of autogenous intraoral block grafts and reported the amount of graft resorption after > 3-month follow-up.
Two authors independently assessed the risk of bias using the Cochrane risk of bias tool, and the third reviewer was the judge in case of conflict.
Two authors independently filled the effective practice and organization of care form for data extraction, and the third reviewer revised the data.
The statistical method of choice was the generic inverse variance, and the results were pooled using random-effect models, with the effect size measure being mean difference (MD) for continuous outcomes and risk ratio (RR) for dichotomous outcomes.
The review members screened 2266 records; we excluded 2231 records by the title and abstract and screened 35 full-text records for eligibility, from which we excluded 32 articles for certain reasons (the most common were a different comparison and excluded study design). Three randomized controlled trials were included in the quantitative and qualitative analyses of this review, providing the data for 41 participants with 49 sites. Data analysis showed a statistically significant potential benefit of membrane coverage in decreasing the amount of graft resorption of intraoral block grafts (MD: -1.20 mm, 95% confidence interval [CI]: -2.11 to -0.30, P = .009). There was no statistically significant benefit from the use of membranes regarding graft success (RR: 1.02, 95% CI: 0.89-1.17, P = .79) and net bone gain (MD: 0.46, 95% CI: -0.16 to 1.09, P = .15). The use of membranes did not show a statistically significant increase in the incidence of complications (RR: 1.80, 95% CI: 0.55-5.96, P = .33). The reviewers judged all the studies as of fair quality regarding the risk of bias.
The use of membranes decreased the graft resorption, but there was no difference regarding graft success and net bone gain. The use of membranes did not increase complications. Furthermore, properly conducted studies should be used to justify the adjunctive use of barrier membranes with block grafts.