Comparative evaluation of RANKL and OPG levels in gingival crevicular fluid and saliva during orthodontic treatment using thermoformed and direct-printed aligners.

INTRODUCTION: Orthodontic tooth movement (OTM) is regulated by alveolar bone remodeling through the receptor activator of nuclear factor kappa-B ligand (RANKL) and osteoprotegerin (OPG) axis. Clear plastic aligners (CPAs), available as thermoformed and direct-printed variants, differ in force delivery and material properties, influencing biomarker responses. OBJECTIVE: This prospective pilot randomized study compared salivary and gingival crevicular fluid (GCF) levels of RANKL and OPG during treatment with thermoformed and direct-printed aligners, and evaluated correlations between saliva and GCF. MATERIAL AND METHODS: Eight healthy adults (18-40 years) requiring orthodontic treatment were randomly assigned to thermoformed or direct-printed aligners. GCF and unstimulated saliva were collected at baseline and at 1, 2, 3, 4, and 6 weeks. RANKL and OPG were quantified using ELISA, and data were analyzed with SPSS v21.0 (IBM, USA). RESULTS: Thermoformed aligners exhibited a peak in GCF RANKL at 3 weeks, followed by a decline at 6 weeks. Direct-printed aligners showed a gradual reduction, with significantly lower RANKL at 4 and 6 weeks (p < 0.05). OPG levels were consistently higher in the direct-printed group across all time points in saliva and GCF (p < 0.05). Salivary OPG strongly correlated with GCF OPG at baseline, 3, and 6 weeks, while RANKL correlations were higher during later treatment phases. CONCLUSION: Aligner types elicited biomarker responses consistent with bone remodeling. Direct-printed aligners demonstrated a trend toward a more stable, OPG-dominant biological response. These findings should be interpreted cautiously, due to the pilot nature of the study. Saliva correlated with GCF, supporting its use as a non-invasive biomarker source. Larger longitudinal studies are warranted.