Effect Of Fixed Brackets and Invisalign on Oral Total Bacterial Load and Profiles of Porphyromonas Gingivalis, Streptococcus Mutans, and Streptococcus Sobrinus: A Qpcr Study

Abstract

Orthodontic treatments, particularly fixed brackets and invisalign clear aligners, are known to alter the oral microbiome, potentially influencing the prevalence of oral pathogens. This study aimed to determine the impact of these orthodontic appliances on the distribution of Porphyromonas gingivalis, Streptococcus mutans, and Streptococcus sobrinus in saliva samples using absolute quantitative real-time PCR. This cross-sectional study conducted in Erbil-Iraq from February 2025 to April 2025. Ninety subjects were divided into three groups for this analysis: thirty subjects with metallic fixed orthodontic appliances, thirty subjects with Invisalign aligners, and thirty as a control group without any orthodontic appliances. Unstimulated salivary samples were collected, and then bacterial DNA was extracted and target bacterial pathogens were quantified using absolute quantitative Real-Time PCR. The total bacterial load was significantly higher in the fixed bracket group (5.4 × 10⁵ ± 3.5 × 10⁵ CFU/μl) compared to the controls (p=0.002). Streptococcus mutans was present in all groups, with significantly higher levels in fixed bracket users (3.6 × 10⁴ ± 2.3 × 10⁴ CFU/μl) compared to clear aligner users (7.5 × 10³ ± 6.9 × 10³ CFU/μl) and controls (1 × 10³ ± 3.2 × 10³ CFU/μl). The prevalence of Porphyromonas gingivalis was higher in fixed bracket users (100%) compared to clear aligner users (93.3%) and controls (90%). There were no significant differences in the levels of Porphyromonas gingivalis, Streptococcus sobrinus, or total bacterial load between the clear aligner and control group (p>0.05). Fixed brackets contribute to higher bacterial loads, particularly Streptococcus mutans. In contrast, Invisalign clear aligners have less impact on oral pathogens, potentially offering advantages for maintaining oral hygiene during orthodontic treatment.