Vertical Ridge Augmentation Strategies

Guided Bone Regeneration (GBR) is an invaluable and beneficial surgical technique adopted when there is the need to augment an alveolar atrophy. Strong clinical and histologic evidence exists on the effectiveness and predictability of GBR in bone augmentation of ridge deficiencies. On the other hand, it is well known that GBR remains a challenge as in the most extreme cases, it is considered a highly technique-sensitive surgical procedure. Whilst there are numerous reviews which report the average incidence of complications in GBR, there is still insufficient evidence and manuscripts reporting a direct correlation between a specific biomaterial (membrane or scaffold) and observed complications. Only one recent systematic review and meta-analysis focused on wound healing complications following GBR for ridge augmentation procedures. Authors explored the complication rate based on the membrane type and on the timing of the first sign of soft tissue complications following bone augmentation procedures. They reported a complication rate of 17% of the overall soft tissue complications, including membrane exposure, soft tissue dehiscence, and acute infection (abscess). This estimate is consistent with that reported (12%) in a more recent systematic appraisal of the evidence on all types of complications in GBR (3). However, when horizontal augmentation procedures were reviewed, a higher rate (21%) of complications was reported within the first 18 months of a GBR procedure. This estimate was inclusive of all possible biologic complications following GBR whilst the rate of membrane exposure was of 23%. Vertical bone augmentation represents one of the most challenging bone regenerative procedures in surgical dentistry. This is because of the inherent difficulties of the surgical procedure and the high risk of complications. The primary aim of this procedure is to recreate alveolar bone in a vertical direction (without the support of any pre-existing walls) and enable recreation of a more favourable anatomy for the restoration of the edentulous site. Evidence on a variety of treatment options has been produced over the last 15 years including distraction osteogenesis, onlay bone grafting, and vertical ridge augmentation (VRA). Systematic reviews evaluating the efficacy of different surgical procedures for VRA either in a staged or a simultaneous fashion, reported a range of vertical bone gain of 2-8 mm. This gain was gradually lost (1.27 to 2.0mm) between 1 to 7 years post-surgery and a wide range of complications (0- 45.5%) has been reported. The aim of this study is to assess and compare incidence of complications and percentage of vertical bone gain when using four different barrier membranes in combination with 50/50 autogenous and xenogenous bone material in VRA procedures. Secondary aims will be to evaluate and compare early and late soft tissue wound healing, gingival microvasculature and structure, patient reported outcomes and the prevalence of need for further bone augmentation and need for soft tissue grafting. Additionally, this study will also aim to assess and compare histomorphometry and histochemistry analyses of core biopsies obtained before implant placement between the four different barrier membranes.