# Comparison of the effects of clear aligners and fixed appliances on the oral microbiota and reactive oxygen species: a prospective study

## TL;DR

This study compares how clear aligners and fixed braces affect oral bacteria and oxidative stress, finding that fixed appliances may increase periodontitis risk.

## Contribution

The study provides new insights into the microbial and oxidative stress differences between clear aligners and fixed appliances during orthodontic treatment.

## Key findings

- Fixed appliances increased pathogenic bacteria and oxidative stress markers compared to clear aligners.
- Clear aligners were associated with health-related bacteria and lower periodontal inflammation.
- Prevotella showed strong correlations with oxidative stress and other bacterial genera across treatment groups.

## Abstract

This study aimed to compare the effects of clear aligners (CA) and fixed appliances (FA) on periodontal indices, oral microbiota, and oxidative stress markers. Potential associations between microbial changes, oxidative stress, and periodontal health were also explored.

Twenty-four orthodontic patients matched at baseline were randomly allocated to the CA (n = 12) and FA (n = 12) groups. Saliva, supragingival plaque, and gingival crevicular fluid (GCF) were collected at baseline (T0), 3 months (T1), and 6 months (T2). Periodontal indices, including plaque index (PI), gingival index (GI), probing depth (PD), bleeding on probing (BOP) were recorded. Microbial composition was assessed via 16S rDNA sequencing. 8-Hydroxy-2’-deoxyguanosine (8-OHdG, a stable biomarker of oxidative DNA damage reflecting ROS levels) in saliva and GCF was quantified using double-antibody sandwich ELISA. Associations were analyzed using Spearman correlation.

PI was significantly higher in the FA group than CA group at T1 (P < 0.01) and T2 (P < 0.05). BOP was higher in the FA group than CA group at T2 (P < 0.05). Pathogenic genera (Prevotella, Veillonella) were enriched in the FA group, while health-associated Rothia and Lautropia predominated in the CA group (P < 0.05). In GCF, 8-OHdG levels were higher in the FA group than CA group at T2 (P < 0.001). In saliva, Prevotella positively correlated with 8-OHdG in the FA group (r = 0.61, P < 0.05); Prevotella negatively correlated with Rothia in both groups (r = -0.90, P < 0.001).

Fixed appliances were associated with enrichment of pathogenic taxa, elevated oxidative stress markers, and worse periodontal indices, potentially linked to higher periodontitis risk. Clear aligners showed less microbial disruption and health-associated taxa enrichment. The Prevotella-8-OHdG-Rothia axis highlights microbiota and oxidative stress interactions as promising targets for preventing orthodontic treatment related periodontal complications.