Difference in pain experience between manual and motor-driven methods of interproximal enamel reduction: a single centre randomized controlled trial

Abstract Background Interproximal enamel reduction (IER) is a common orthodontic procedure used to correct tooth-size discrepancies, create space, and reduce black triangles. Although several studies have examined the effects of IER on enamel roughness, caries risk, and periodontal health, none have investigated patient-reported pain associated with different IER techniques. As pain is a key patient-reported outcome, understanding how it varies between manual and motor-driven techniques can help clinicians improve patient comfort, refine treatment planning, and enhance informed consent discussions. Objectives The primary objective was to compare pain experienced during IER using manual abrasive strips versus motor-driven abrasive strips in patients undergoing orthodontic treatment at Royal Surrey County Hospital NHS Foundation Trust. Null Hypotheses There is no significant difference in patient-reported pain between manual and motor-driven IER methods in the lower labial segment. Methods This prospective, randomised, crossover clinical trial used visual analogue scale (VAS) questionnaires to measure pain. In accordance with a power calculation based on detecting a 10 mm difference in VAS scores as statistically significant, a total of 68 subjects were required. A total of 34 participants (due to the crossover design) aged 16 years or older were recruited. Participants were randomly assigned via concealed allocation into two groups. Group A underwent manual IER first, followed by motor-driven IER after a 6-week washout period; Group B underwent the reverse sequence. Due to the practical nature of the interventions, blinding of participants and operators was not possible. Randomisation, data measurement, and statistical analysis were conducted by clinicians blinded to allocation. Participants recorded their pain levels on a VAS immediately before and after each IER session. The difference in pre- and post-procedure scores represented the pain outcome. Two independent, blinded assessors measured VAS scores to ensure inter- and intra-rater reliability. Inclusion criteria required participants to be, over 16 years old and undergoing fixed appliance therapy involving IER. Exclusion criteria included systemic health conditions, chronic pain disorders, or previous hypersensitivity to IER procedures. Results All 34 participants completed the study, with no dropouts or adverse events. The mean increase in VAS pain score following manual IER was 18.5 mm (SD 16.6; 95% CI 15.6–21.3), compared with 15.6 mm (SD 16.0; 95% CI 12.9–18.3) for motor-driven IER. The mean difference in pain between techniques was 2.9 mm (SD 2.0; 95% CI −1.0 to 6.8), which was not statistically significant. No significant effects were observed for intervention order, age, or gender. Inter- and intra-rater agreement for VAS scoring was excellent (ICC = 1.00 for both). No participant reported harm, discomfort, or undue stress during participation. Conclusion No significant difference in pain was found between manual and motor-driven IER techniques in orthodontic patients. Therefore, the choice of technique should be based on operator preference, efficiency, and patient comfort rather than pain expectations. Further research could explore other patient-reported outcomes, including treatment duration, anxiety, and perceived ease of procedure. Trial Registration ClinicalTrials.gov: NCT02455700