Bone and Furcation Changes in Molars After Comprehensive Orthodontics.

BACKGROUND: This study assessed the impact of comprehensive full-mouth fixed orthodontic treatment on molar periodontal bone levels, furcation involvement, and post-treatment tooth loss in periodontitis-affected adults following phase I non-surgical periodontal therapy with regular maintenance. MATERIALS AND METHODS: Molar periodontal status was assessed at pretreatment (T0) and posttreatment (T1), with survival at follow-up (T2). Independent variables included baseline bone level, furcation involvement, periodontal surgical history, craniofacial and dentoalveolar parameters, treatment-related cephalometric changes, opposing occlusion, and three-dimensional molar movement. Univariable analyses were followed by logistic regression to identify predictors of bone level and furcation deterioration and tooth loss. RESULTS: Seventy subjects were included, with 395 molars assessed at T1 and 180 at T2. Periodontal deterioration occurred in 5.3% (bone level loss) and 5.1% (furcation involvement) of molars during orthodontic treatment. Deterioration was associated with compromised baseline periodontal support, prior regenerative periodontal surgery, and orthodontic factors including molar extrusion, antagonist teeth intrusion, and greater axial uprighting. Craniofacial and dentoalveolar characteristics also influenced risk. At follow-up, 3 molars (1.7%) were lost for periodontal reasons, with post-orthodontic furcation involvement increasing extraction risk. CONCLUSION: Even with regular periodontal maintenance, compromised baseline molars remained vulnerable to orthodontic-related deterioration, influenced by occlusal stress and craniofacial characteristics. CLINICAL RELEVANCE: Meticulous orthodontic management is essential in clinical decision-making to preserve function and periodontal health. Occlusal stress appeared clinically relevant in the context of regular periodontal maintenance. Careful biomechanical planning and monitoring of occlusal loading may help mitigate these risks during comprehensive orthodontic treatment.