Longitudinal evaluation of salivary biomarkers and white spot lesion development in patients undergoing fixed orthodontic treatment: A prospective cohort study.

BACKGROUND

This prospective study aimed to evaluate the longitudinal changes in salivary biomarkers in relation to white spot lesion (WSL) development during fixed orthodontic treatment.

METHODS

This prospective longitudinal cohort study enrolled 56 systemically healthy patients (aged 18-30years) with mild Class I malocclusion undergoing non-extraction-fixed orthodontic treatment. The participants were classified into two groups based on the development of incident white spot lesions (WSL-present vs. WSL-absent) over a 12-month period. Unstimulated whole saliva was collected at baseline, 6months, and 12months to measure pH; buffering capacity; calcium, phosphate, and fluoride concentrations; and counts of mutans streptococci and Lactobacillus spp. Between-group comparisons were performed using repeated-measure mixed models. Associations with WSL development were examined using univariate and multivariate logistic regression with least absolute shrinkage and selection operator (LASSO) variable selection.

RESULTS

Over 12months, 22 patients (39%) developed WSLs (112 lesions in total) predominantly affecting the maxillary lateral incisors and canines. Baseline characteristics were comparable between the groups (all P>0.05). Repeated-measures analysis showed significant group×time interactions for salivary pH (F=40.09, P<0.001), fluoride (F=10.27, P<0.001), calcium (F=5.14, P=0.009), and phosphate (F=11.78, P<0.001), indicating a steeper decline in the WSL-present group. Multivariable logistic regression of longitudinal changes revealed that greater declines in pH and fluoride levels were independently associated with WSL development. No significant associations were observed for buffering capacity, calcium, phosphate, or microbial count.

CONCLUSION

Longitudinal decreases in salivary pH and fluoride levels were independently associated with WSL development during fixed orthodontic treatment. Monitoring these non-invasive parameters may support risk stratification and targeted preventive care.

ETHICAL APPROVAL: This study was conducted in the Department of Orthodontics, Kothiwal Dental College and Research Centre, Moradabad, India in accordance with ethical guidelines and was approved by the Institutional Ethical Review Board (KDCRC/IERB/SS/2023/06).