Purpose: To identify and assess differences in oral hygiene parameters in patients undergoing orthodontic treatment with clear aligners compared to fixed appliances.
Materials and Methods: Published and unpublished literature was searched in seven databases until May 31st 2021. Representative keywords included ‘orthodontic aligner’, ‘fixed appliance’, ‘oral hygiene’, ‘plaque index’, ‘caries’. Study selection, data extraction, risk of bias and certainty of evidence assessment were undertaken independently by three reviewers. Random effects meta-analyses with respective confidence intervals (95% CI) were conducted, where applicable.
Results: A total of 882 unique records were screened, with a final number of 21 articles being eligible for qualitative synthesis, while 4 of those contributed to meta-analyses. Risk of bias was rated within the range of low to high or serious overall, while certainty of evidence was low to very low according to GRADE. For periodontal parameters, adults undergoing aligner orthodontic treatment presented summary plaque scores 0.58 lower than those treated with fixed appliances, within the first 6 to 12 weeks (4 studies: mean difference: -0.58; 95%CI: -0.82, -0.34; p < 0.001; I2 squared: 71.3%), while no evidence of difference was recorded for inflammation indices. Microbiologic parameters such as presence of S. mutans and lactobacilli were more pronounced in patients with fixed appliances for the first 3 to 6 months (synthesised data from 2 studies).
Conclusions: In the short-term after initiation of orthodontic treatment, patients treated with aligners and no additional attachments/adjuncts presented potentially higher levels of oral health overall. However, the evidence is supported by low to very low certainty.