Longitudinal changes in microbiology and clinical periodontal parameters after removal of fixed orthodontic appliances

The aim of this longitudinal study was to monitor patients' microbiological and clinical parameters from bracket placement up to 3 months post-treatment. Twenty-four patients (10 males and 14 females, aged 14.6 ± 1.0 years) were included in this investigation. Microbiology (sub- and supragingival), periodontal probing depth (PPD), bleeding on probing (BOP), and gingival crevicular fluid (GCF) flow were assessed at baseline (T1), at bracket removal (T2), and 3 months post-treatment (T3). A statistical comparison was made over time and between the banded, bonded, and control sites. Repeated measurements on patients were taken into account by modelling the patients as a random factor. Except for PPD and BOP, values were log-transformed before analysis. Corrections for simultaneous hypothesis testing were performed via simulation. The results demonstrated that sub- and supragingival colony-forming units ratio (CFU ratio aerobe/anaerobe) decreased significantly (relatively more anaerobes) at T2 compared with T1. Between T2 and T3 no significant increase in CFU ratio was seen, resulting in a significantly lower CFU ratio at T3 compared with T1 for subgingival plaque. The difference concerning supragingival plaque between T3 and T1 was not significant. Clinical parameters PPD, POB, and GCF flow showed a significant increase between T1 and T2. Between T2 and T3 these variables decreased significantly but remained significantly higher than at T1 [except for BOP values at the bonded sites (P = 0.0646)]. Placement of fixed orthodontic appliances has an influence both on microbial and clinical periodontal parameters, which were only partly normalized, 3 months following the removal of the appliances.