Timing of alveolar bone surgery as a predictor of guided bone regeneration success: results of a retrospective cohort study.

The physiological condition of bone prior to regenerative procedures has received little attention, with concerns more often related to technical and biomaterial issues. The primary aim of the study was to test whether pathophysiological changes in bone following tooth extractions or other alveolar bone surgery have an additional impact on bone growth in guided bone regeneration (GBR) with collagen membranes. A total of 33 consecutive patients with vertical and horizontal atrophy of the alveolar ridges, comprising 70 dental sites, treated with staged GBR using collagen membranes and a resorbable graft material, were analyzed in terms of the specific results of the procedure. The effect of defect morphology and recent bone surgery on the critical dimensions of the alveolar ridge was assessed by superimposing serial cone-beam computed tomography (CBCT) images before the augmentation procedure and after the bone healing period. Complex defects and recent bone surgeries, not older than 6 months, showed the greatest increase in crest width: 6.42 mm (P < 0.001) and 5.46 mm (P = 0.003) respectively, as well as in height: 2.80 mm (P = 0.007) and 1.99 mm (P = 0.028) respectively, while common defects and bone surgery older than 1 year led to null or negative results. Guided bone regeneration using collagen membranes was significantly influenced by the pre-existing morpho-physiological state of the bone, which could be explained by the increased osteogenic potential of the bone walls under the effect of the regional acceleratory phenomenon triggered by tooth extraction or other surgical interventions on the alveolar bone.