A comparison between indirect and objective wear-time assessment of removable orthodontic appliances

Background/Objectives: Patients do not always adhere to the wear times prescribed for removable orthodontic appliances. We evaluated the validity and usability of indirect wear-time assessment methods by comparing wear-time estimates with microelectronically measured wear times in patients with removable orthodontic appliances. Methods: Wear times of 33 expansion plates, 34 functional appliances, and 42 retention plates of patients aged 6-20 years (12.3 +/- 2.9 years, 50.5% female) were indirectly determined by practitioners using a questionnaire assessing five parameters on a 5-point Likert scale: appliance handling, appliance appearance, bite shift, tooth movement, and appliance fit. The perceived difficulty in assessing each parameter was rated. Actual wear times were evaluated with microelectronic sensors in the appliances. Results: Regression analyses revealed that practitioners' decisions about wear times varied depending on the type of appliance and criteria used, with only one standard criterion best predicting estimated wear time for each appliance. Different standard criteria were better predictors of measured wear time: 22.3% of wear-time variability was explained by expansion plate appearance, 31.2% by functional appliance handling, and 18.8% by retainer fitting. However, practitioners rated the difficulty of assessment in most cases as 'easy'. Limitations: The study was not double blinded for technical reasons, and practitioners may have considered the evaluation criteria more carefully than in normal daily practice. Conclusions: Practitioners' decisions about wear times based on standard criteria strongly vary depending on the type of appliance and criteria used.