A retrospective randomized double-blind comparison study of the effectiveness of Hawley vs vacuum-formed retainers

OBJECTIVE: To compare Hawley with vacuum-formed retainers. MATERIALS AND METHODS: Eighty-two patients who had received treatment with upper and lower fixed appliances were randomly assigned either a Hawley or a vacuum-formed retainer. Study models were fabricated for each patient on day of debond and 2 months, 6 months, and 12 months after debond. Using a specially constructed pantograph, four variables were measured for each set of models at each of these time periods. These were upper and lower intermolar widths, intercanine widths, arch length, and a modified Little's index of irregularity. Method error was determined by repeating the measurements on 10 sets of models. RESULTS: For each of the variables under test and at each of the four time periods, there were no statistically significant differences (α = .05) between each of the two retainers, vacuum-formed and Hawley. CONCLUSION: The degree of relapse that is likely to occur following a course of fixed appliance therapy is unlikely to be affected by the choice of retainer, vacuum-formed or Hawley. Therefore, when deciding on the type of retainer to be fitted following fixed appliance therapy, other factors such as cost may play a more significant role.