Changes in the pH and the Flow Rate of Saliva During Orthodontic Treatment with Fixed Orthodontic Appliances: A Systematic Review

This systematic review aimed to assess salivary flow and pH changes at various stages of orthodontic treatment with fixed appliances. A comprehensive searches in electronic databases, including Medline, ResearchGate, Web of Science, SAGE Journals, Cochrane Oral Health Group’s Trials Register, and ScienceDirect, without any publication date restrictions until January 2022 was conducted. The Pre-ferred Reporting Items for Reporting Systematic Reviews and Meta Analyses (PRISMA 2020 version) protocol was adopted and the risk of bias assessments were performed using the Cochrane ROBINS-I tool for non-randomized studies. Out of 4902 articles, 25 were fully evaluated, and seven studies that met the inclusion criteria were included in the review. The results showed that orthodontic treatment with fixed orthodontic appliances increased the stimulated salivary flow rate during various stages of treatment. However, the unstimulated salivary flow rate showed different changes. Furthermore, stimulated salivary pH increased, whereas unstimulated salivary pH significantly decreased, depending on the specific period of orthodontic treatment. Overall, fixed orthodontic appliances have an impact on salivary flow rate and pH during different stages of treatment. Nevertheless, the current literature is insufficient to draw definitive conclusions. More well-designedrandomized studies with larger sample sizes are necessary to confirm these findings.