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

To compare Hawley with vacuum-formed retainers.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.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.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.