Orthodontic treatment and oral microbiota changes: a systematic review of oral dysbiosis revealed by 16S rRNA gene analysis

Objectives: Evaluate the changes in oral microbiota linked to orthodontic treatment by analyzing the 16S rRNA gene. Materials and Methods: A total of 22 articles was included in the systematic review. The methodological quality of these studies was assessed using the Newcastle-Ottawa Scale for non-randomized studies and the Risk of Bias tool for randomized studies. Results: Orthodontic appliances significantly influenced the composition of oral microbiota. Specifically, fixed orthodontic appliances were linked to an increase in periodontopathogenic bac-teria associated with various systemic diseases. In contrast, transparent aligners correlated with an increase in Streptococcus species. Conclusions: In this study, we evaluated the changes in oral microbiota associated with ortho-dontic treatment by analyzing the 16S rRNA gene. Results revealed significant alterations in oral microbiota following orthodontic treatment; however, significant variability among studies pre-vents firm conclusions. Additional research is essential to clarify the effects on oral health. (Angle Orthod. 2026;96:114–124.).