Oral Health-Related Quality of Life (OHRQoL), Pain and Side Effects in Adults Undergoing Different Orthodontic Treatment Modalities: A Systematic Review and Meta-Analysis

<b>Background</b>: The present study aimed to identify the differences between experiences, in terms of oral health-related quality of life, pain, side effects and/or other complications, of adults undergoing orthodontic treatment using removable aligners and fixed labial or lingual appliances. <b>Methods</b>: The review was registered with PROSPERO, and a comprehensive electronic search was undertaken without language or date restrictions. Randomised and non-randomised trials and prospective cohort and cross-sectional studies along with case series were included. The Cochrane Collaboration's Risk of Bias 2 Tool, Newcastle-Ottawa Scale and The Risk Of Bias In Non-Randomized Studies-of Interventions tools were used to assess quality. Data were grouped in terms of oral health-related quality of life, pain side effects and/or other complications. <b>Results</b>: Data from 35 studies were included; 9 were eligible for meta-analysis. Thus 2611 participants were included related to removable aligners (n = 513), fixed labial (n = 1816) and lingual (n = 218) appliances or a combination (n = 64) of appliances. The standardised mean differences in visual analogue scale pain reports between 24 h and 7 days were -10.02 (95% CI: -11.13, -8.91) for aligners and -6.40 (95%CI: -10.42, -2.38) for labial appliances (<i>p</i> = 0.09). There was a significant improvement in dental self-confidence following fixed labial appliance treatment (<i>p</i> = 0.001). <b>Conclusions</b>: No difference was detected in short-term pain with aligners and labial appliances. Aligners may have less impact on oral health-related quality of life measures compared to labial appliances. Lingual appliances have a persistent impact on speech, despite some adaptability. Any deterioration in oral health-related quality of life measures during treatment appears temporary. Further randomised trials using validated assessment tools and comparing aligners and labial and lingual appliances are required.