Objective evaluation of compliance after orthodontic treatment using Hawley or vacuum-formed retainers: A 2-center randomized controlled trial over a 3-month period.

INTRODUCTION

The aim of this 2-arm parallel trial was to assess patient compliance objectively with Hawley or vacuum-formed retainers in the maxillary arch in a 3-month period after active orthodontic treatment through the use of the thermosensitive microsensor TheraMon.

METHODS

Patients who had just completed orthodontic treatment in the Postgraduate Orthodontic Clinic, School of Dentistry, National and Kapodistrian University of Athens and in a private orthodontic practice were randomly allocated to either the Hawley or vacuum-formed group for retention. Eligibility criteria included patients aged 12-18 years who had undergone orthodontic treatment in both arches for ≤ 5 years. The main outcome was the average objective daily difference in compliance measured with TheraMon between patients receiving either Hawley or vacuum-formed retainers in the maxillary arch for 3 months. Secondary outcomes pertained to the average objective difference in compliance between the 2 retainers for the first month in retention and the association between objective measurements of compliance and diary-reported duration of wear for both the first and 3- month periods. Randomization was implemented with a computer-generated randomization list; allocation was concealed in sequentially numbered, sealed, opaque envelopes. Blinding to the study protocol was not feasible either for the patient or orthodontist. Patients were instructed to wear the retainer full-time. Data were analyzed using nonparametric statistics and linear regression with standard errors based on the bootstrap method.

RESULTS

Seventy-seven patients (median age 14.8 years; interquartile range 1.5; range 12.1-17.6) were randomized in a 1:1 ratio to either a Hawley or vacuum-formed retainer. Baseline characteristics did not present significant differences between groups. One patient from the Hawley group was excluded from 3 months' follow-up owing to a microsensor fault. Objectively assessed median daily wear time for the Hawley group was 15.3 hours (interquartile range 6.8), whereas for the vacuum-formed group it was 18.3 hours (interquartile range 4.6) for the 3-month interval. Patients allocated to vacuum-formed retainers had higher wearing values of 2.10 h/d compared with the Hawley group, after adjusting for trial settings (mean difference 2.10; 95% confidence interval 0.32-3.89; P = 0.02). Patients from private orthodontic practice had an increased potential for compliance of 2.16 h/d compared with university settings after adjusting for type of appliance (mean difference 2.16; 95% confidence interval 0.34-3.97; P = 0.02). A significant correlation was detected between objective assessment and self-reported compliance for both retention protocols in the first and 3-month intervals. No harm was observed during follow-up.

CONCLUSIONS

This study found relatively high compliance in the short-term retention phase for both appliances. Vacuum-formed retainers were better accepted by adolescent patients, whereas those proceeding to private orthodontic practice were more compliant. There was a positive and statistically significant correlation between objective and subjective measures of compliance.

REGISTRATION

This trial was registered in ClinicalTrials.gov: NCT03683862.

FUNDING

No funding or conflict of interest to be declared.

PROTOCOL

The protocol was not published before trial commencement.