Salivary biomarkers during en-masse retraction into recent and healed extraction sites: A randomised controlled trial

To explore changes in salivary biomarkers and rate of tooth movement during en-masse retraction into recent and healed extraction sites.

A total of 20 patients with prominent anterior maxillary teeth requiring en-masse retraction were randomly allocated into two groups. First premolar extractions were carried out either at the start of orthodontic treatment (healed extraction group) or immediately before the commencement of en-masse retraction (recent extraction group). Unstimulated saliva samples and study models were collected at five time points: before the start of orthodontic treatment; after alignment and levelling; and at 2, 8 and 12 weeks after the initiation of retraction. Changes in concentrations of salivary biomarkers were assessed as primary outcomes. Rate of tooth movement was evaluated as a secondary outcome. A mixed analysis of variance was used to evaluate changes in salivary biomarker concentrations over time and between groups. The rate of tooth movement was compared between groups using an independent t-test.

Both groups demonstrated an increase in salivary receptor activator of nuclear factor kappa-B ligand (RANKL) levels and a decrease in osteoprotegerin (OPG) levels during the 12-week retraction period. Significant time and group interaction was observed for the RANKL:OPG ratio (P < 0.05). Between-group differences at individual time points were not statistically significant after correction for multiple comparisons. A statistically significantly higher rate of tooth movement was found in the recent extraction group (mean difference: 0.07 mm/week, 95% confidence interval 0.04-0.09; P < 0.05), although this difference is probably not clinically significant.

The RANKL:OPG ratio may reflect the biological activity during orthodontic tooth movement better than individual biomarker concentrations and extraction timing may influence the rate of space closure.

Trial was prospectively registered with the Clinical Trials Registry India (https://ctri.nic.in/Clinicaltrials) CTRI/2020/12/029660 and approved by the Institutional Ethics Committee of All India Institute of Medical Sciences, Jodhpur (AIIMS/IEC/2019-20/977), Rajasthan, India.