A comparative review of the oral microbiome in clear aligners and fixed orthodontic appliances.

Abstract

A commentary on: Lucchese A, Marcolina M, Mancini N et al. A comparison of the alterations of oral microbiome with fixed orthodontic therapy and clear aligners: a systematic review. J Oral Microbiol 2025; 17: 2372751.

Data sources: The review searched multiple electronic databases (PubMed, Cochrane Library, Embase, Web of Science, Scopus, Ovid, Dentistry and Oral Sciences Source) and gray literature (OpenGray) up to May 30, 2023.

Study selection: The selection of the studies was processed according to PRISMA guidelines. Two reviewers independently screened titles and abstracts, with disagreements resolved by a third reviewer. Full-text articles were then assessed for eligibility based on pre-defined inclusion/exclusion criteria (RCTs, nRCTs, cohort studies; at least two time points for analysis; minimum 10 patients; clear aligners vs. fixed appliances or comparison between them; patients with good systemic health not taking medications).

Data extraction and synthesis: Data extraction from the included studies was carried out by two reviewers in consultation with a third reviewer to define the variables for extraction and resolve any disagreements. Extracted data included study characteristics (author, year, design, sample size, patient age), intervention details, sample collection methods (saliva, plaque), microbial analysis methods (16S rRNA sequencing, PCR, BANA test), and microbiological outcomes. A qualitative synthesis was performed due to the heterogeneity of the included studies, precluding meta-analysis.

Results: A total of 484 articles were identified, with 9 studies that met the inclusion and exclusion criteria: eight non-randomized controlled trials and one randomized controlled trial. Sample sizes ranged from 10 to 77 participants. Various microbial analysis methods were employed, including 16S rRNA gene sequencing (5 studies), PCR (3 studies), and the BANA test (1 study). Following the application of rating scales, 1 article was classified as having a low risk of bias, 6 as having a moderate risk, and 2 as having a serious risk of bias.

Conclusions: The review suggests that clear aligners may be associated with a less detrimental impact on the oral microbiome compared to fixed appliances, possibly due to improved oral hygiene. Both therapies alter the oral microbiome; however, the changes caused by aligners are more conducive to better oral health compared to fixed appliances.