Comparative evaluation of RANKL and OPG levels in gingival crevicular fluid and saliva during orthodontic treatment...

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.

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.

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).

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.

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.