Comparative Evaluation of Periodontal Pathogen Load and Health in Patients Treated With Fixed Orthodontic Appliances Versus Clear Aligners: A Prospective Clinical Study.

INTRODUCTION: Orthodontic appliances can alter the oral microbial ecosystem and predispose patients to plaque accumulation and periodontal inflammation. Fixed appliances introduce bracket-wire complexes that favor biofilm retention, whereas clear aligners are removable and may allow better maintenance of oral hygiene. This study aimed to compare short-term changes in clinical periodontal parameters and subgingival colonization by Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans in patients undergoing orthodontic treatment with fixed appliances or clear aligners. MATERIALS AND METHODS: This prospective study was conducted in the Department of Orthodontics, where 40 healthy adults aged 18-30 years were enrolled and equally divided into two groups: fixed appliances (n=20) and clear aligners (n=20). Baseline professional prophylaxis was administered to all patients before appliance placement. Clinical assessments, including plaque index, bleeding on probing, and probing depth, were recorded at baseline (T0) and after three months (T1). Subgingival plaque samples were collected from the second premolars and lateral incisors, and bacterial loads of P. gingivalis and A. actinomycetemcomitans were quantified by quantitative polymerase chain reaction (qPCR). Statistical analyses included independent t-tests for clinical parameters and Mann-Whitney U tests for bacterial loads, with significance set at p<0.05. RESULTS: At baseline, the two groups were comparable with no significant differences in clinical parameters or microbial counts. After three months, the fixed appliance group showed significantly greater deterioration in periodontal parameters than the clear aligner group. The mean increase in plaque index was 0.54±0.26 for fixed appliances versus 0.20±0.16 for clear aligners (p<0.001). Bleeding on probing and probing depth also worsened in the fixed appliance group. Microbiological analysis revealed higher bacterial loads for both pathogens in the fixed appliance group. Median P. gingivalis levels were 150.5×10⁴ copies/mL in fixed appliances versus 98×10⁴ copies/mL in clear aligners, while A. Actinomycetemcomitans was more abundant in fixed appliances, particularly at premolar sites. CONCLUSION: Fixed orthodontic appliances were associated with significantly greater increases in periodontopathogen loads and deterioration in periodontal health during the early treatment period than clear aligners. Therefore, clear aligners may be a more favorable option for patients in whom periodontal preservation is a priority.