Extend GBR fully or not at all: partial coverage fails to protect adjacent alveolar bone

Flap surgery in the anterior maxilla carries a predictable collateral cost: resorption of the thin labial alveolar wall (LAW) of teeth adjacent to the surgical site. Even when the implant site heals uneventfully, the neighboring alveolar bone can quietly deteriorate, compromising soft tissue support and the overall aesthetic outcome. This retrospective cohort study asked a straightforward clinical question: does extending the GBR graft to cover the LAW of adjacent teeth actually protect that bone from post-surgical resorption?

The authors enrolled 80 patients and analyzed 135 adjacent teeth, stratifying them into three groups based on intraoperative graft extension relative to the buccal bone wall (BBW): Non-Extended GBR (NE-GBR), where the graft remained confined to the edentulous site; Partially Extended GBR (PE-GBR), where the graft covered part of the BBW; and Fully Extended GBR (FE-GBR), where the graft extended to cover the entire BBW up to the alveolar crest. Outcomes were assessed at six months using superimposed pre- and post-operative CBCT scans, measuring both horizontal LAW thickness and the vertical distance from the cementoenamel junction to the alveolar crest.

The results draw a clear line between full extension and anything less. In the NE-GBR and PE-GBR groups, statistically significant horizontal resorption occurred — approximately 0.40 and 0.43 mm respectively — while the FE-GBR group showed no significant change (0.15 ± 0.75 mm, p = 0.523). Vertically, only the FE-GBR group demonstrated a dimensional gain (0.43 ± 1.10 mm, p < 0.001), whereas the other groups experienced net bone loss. Mixed-effects models reinforced these findings, identifying FE-GBR as a significant independent positive predictor for both horizontal and vertical dimensional preservation (β = 0.48 for both, p ≤ 0.001).

The clinical implication is direct and actionable. When performing GBR in the anterior maxilla, the conventional instinct to limit the graft to the edentulous defect may inadvertently expose adjacent teeth to avoidable bone loss. Extending the regenerative material fully — to the crestal margin of the neighboring buccal wall — appears sufficient to neutralize this risk. Partial extension, notably, offers no measurable advantage over no extension at all, which suggests that a half-measure here is effectively no measure.

For periodontists and implantologists working in the aesthetic zone, where even sub-millimeter changes in alveolar contour can translate into visible soft tissue recession or altered emergence profiles, this study provides a rational and technically feasible modification to standard GBR protocol. The six-month timeframe is a limitation, and longer follow-up will be needed to confirm durability. Nevertheless, the evidence supports a simple intraoperative decision: when in doubt, extend fully.