Investigating Salivary pH, Buffering, and Bacterial Load Changes Post-Orthodontic Treatment

Objectives: Orthodontic treatment can impede a patient's oral hygiene, ultimately leading to altered composition and relative abundance of oral microbiota. Our study aims to assess changes in salivary pH, buffering capacity, and microbial load over the first six months following completion of orthodontic treatment.
Methods: The sample consists of 12-19-year-old males and females who concluded orthodontic treatment with metal fixed appliances.

Four total visits per subject were organized as follows: T1 (baseline, day 0, collected within one month of braces removal), T2 (one month), T3 (three months), and T4 (six months). At each visit, salivary pH and buffering capacity were assessed using Saliva-Check Buffer Kits (GC America Inc). In addition, salivary samples were collected and plated to assess the levels of Streptococcus mutans and Candida albicans present.

The salivary samples were diluted and plated on three different agar plates: Brain Heart Infusion (BHI) to assess total bacterial load, Sabouraud Dextrose (SAB) to approximate the load of C. albicans, and Mitis Salivarius-Bacitracin (MSB) to approximate the load of S. mutans.
Results: Subjects’ mean resting pH increased by 3.5 % from T1-T4. The increase in mean resting pH from T1-T4 was found to be statistically significant (p <0.01) using a repeated measures ANOVA. The mean buffering capacity increased by 7.8 %. This increase in mean buffering capacity from T1-T4 was also statistically significant (p<0.05) using a repeated measures ANOVA.

Furthermore, the total bacterial load and the representative levels of C. albicans and S. mutans all decreased after the completion of orthodontic treatment. However, observed differences were not significant (p>0.05) as assessed with a t-test.
Conclusions: Although orthodontic treatment can cause cariogenic changes in the oral microbiome, the relatively rapid recovery of both salivary pH and buffering capacity is an encouraging finding. The sizable decrease in total bacterial load and the representative levels of C. albicans and S. mutans warrants further exploration with an increased sample size.