Salivary parameters in individuals undergoing orthodontic treatment with clear aligners: a scoping review

This scoping review aimed to map the salivary parameters investigated in children, adolescents, young adults, and adults undergoing orthodontic treatment with clear aligners, describe saliva collection and analytical assessment methods, and identify methodological gaps in the literature.

The review was reported according to PRISMA-ScR and had its protocol registered in the Open Science Framework. Searches were conducted in MEDLINE/PubMed, Scopus, Web of Science, and ProQuest, without restrictions on year or language. The initial search was performed on June 12, 2024, and updated on September 9, 2025. Two independent reviewers screened records in Rayyan, assessed full texts, and extracted data using a standardized form. Eligible studies were primary clinical investigations assessing salivary parameters in individuals undergoing clear aligner therapy. Data were synthesized descriptively, without a formal risk-of-bias appraisal.

From 3225 records, 1917 references were screened, 28 full texts were assessed, and 22 studies from 11 countries were included. The included reports comprised 880 participants across all groups (494 clear aligner and 386 comparator participants), although potential overlap between reports cannot be excluded. Most studies were prospective observational investigations, and pediatric participants were underrepresented. Invisalign™ was the most frequently investigated aligner system, although several studies used other thermoformed appliances or did not specify the brand. The included studies varied substantially in follow-up schedules, pre-sampling instructions, saliva type, collection procedures, sample processing, storage conditions, and analytical platforms. Salivary outcomes were mapped into four domains: microbiological parameters, biochemical and immunological markers, physicochemical properties, and material-related chemical eluents. Microbiological outcomes were the most frequently mapped domain, followed by inflammatory, oxidative stress, hormonal, enzymatic, physicochemical, BPA, monomer, and metabolite-related outcomes.

This scoping review provides a descriptive map of salivary parameters investigated during clear aligner therapy and the methods used for their collection and assessment. Methodological variability limits comparability across studies. Future research should prioritize standardized saliva collection, processing, storage, analytical reporting, age-stratified sampling, and transparent reporting of aligner materials and clinical context.