Hawley retainers full- or part-time? A randomized clinical trial

The aim of this trial was to compare two different orthodontic retention regimens: is night-only wear of upper and lower Hawley retainers for 1 year as effective as 6 months full-time followed by 6 months night-only wear? Sixty-seven consecutive patients attending for orthodontic debond were randomly allocated to wear upper and lower Hawley retainers either for 1 year night-only (group 1) or for 6 months full-time followed by 6 months night-only (group 2). In group 1, 41.2 per cent were males and 58.8 per cent were females and their mean age was 15.6 years [standard deviation (SD) 1.6 years]. In group 2, 24.2 per cent were males and 75.8 per cent were females and their mean age was 15.8 years (SD 1.2 years). Study models were taken at the start (T0) and end (T1) of treatment and 1 year post-debond (T2). Digital callipers were used to measure upper and lower labial segment irregularity using Little’s index and upper and lower labial segment crowding. To evaluate differences between groups 1 and 2 t-tests were used. There were no statistically significant differences between the two retention regimens at T2 for labial segment irregularity or crowding (P > 0.05). Since both retention regimens were equally effective during the 1 year retention period, it would seem clinically acceptable to ask patients to wear their retainers at night only.