The influence of initial defect morphology of alveolar ridge on volumetric change of grafted bone following guided bone regeneration in the anterior maxilla region: an exploratory retrospective study

BACKGROUND: This study aimed to explore the influence of initial ridge defect morphology on the outcome of guided bone regeneration (GBR) in the anterior maxilla region. METHODS: Cone beam computed tomography (CBCT) examinations of patients who participated in a previous randomized controlled trial were used to assess linear and volumetric changes of bone grafts (LCB and VCB) from immediately (T0) to 6 months (T1) after surgery. The three-dimensional (3D) surface rendering of the initial defect was reconstructed, and morphological variables were defined in mesial-distal, buccal-lingual, and coronal-apical directions. The Spearman correlation, logistic regression model, and receiver operating characteristic (ROC) analyses were used to assess the possible association between initial defect morphological variables and VCB. RESULTS: A total of 62 eligible patients were included in this study. The median value of LCB was less than 20% at different levels, while the corresponding value of VCB was 52.0%. The Spearman correlation analysis showed that the standard deviation of buccal-lingual distance (BL(SD)) was negatively associated with VCB (r=−0.315, P=0.013), whereas the ratio of maximum coronal-apical/mesial-distal distance (R(mCA/mMD)) was positively related to VCB (r=0.607, P<0.001). The multivariate regression analysis revealed that the prognosis effect of BLSD (OR: 0.220, 95% CI: 0.074 to 0.655, P=0.0047) and R(mCA/mMD) (OR: 7.045, 95% CI: 2.361 to 21.024, P=0.0017) remained significant. ROC curve analysis showed that R(mCA/mMD) could be used to correctly classify VCB in 78.9% patients and BLSD in 71.0% of patients, as classified by the median of VCB. The discrimination value of BLSD and R(mCA/mMD) revealed the areas under curve (AUC) of 0.71 (95% CI: 0.545 to 0.883) and 0.74 (95% CI: 0.573 to 0.913), respectively. CONCLUSIONS: Within the limitations of this study, the present data confirmed the effect of initial ridge morphology on the GBR outcome in the anterior maxilla region. Specifically, a defect morphology with more BLSD and/or lower R(mCA/mMD) may significantly decrease the resorption amount of grafted bone.