Abstract
Design
Three arm, parallel group, patient randomised trial.
Intervention
Seventy-five patients who had just completed a course of treatment with four premolar extractions and fixed straight wire appliances in both jaws (0.022 inch, MBT) having had no previous orthodontics, were randomised by participant ballot sampling. To be eligible they had to be in the permanent dentition, with space deficiencies in both jaws, normal skeletal and dentoalveolar sagittal, vertical and transverse relationships, Class I molars or 3mm anterior or posterior deviation. The three retention methods were: 1) removable vacuum-formed retainer with maxillary canine-to-canine and palatal coverage plus a mandibular canine-to-canine bonded retainer (GroupV-CTC); 2) an identical maxillary vacuum-formed retainer as in Group V-CTC plus stripping of mandibular anterior teeth (Group V-S); and 3) a prefabricated positioner covering all erupted teeth in both jaws (Group P). Patients were given appliances within one hour of debonding, which were worn more for the first than second year then discontinued.
Outcome measure
Dental casts were taken at four time points; before treatment, on removal of fixed appliances, after 12 months and 24 months of retention. Twenty randomly selected casts were measured by a single blinded assessor on two separate occasions, four weeks apart, using electronic digital callipers for inter-canine width; inter-molar width; arch length; overjet; and overbite. Height and estimated compliance was recorded at every visit. Successful retention using Little's Irregularity Index was considered to be <3.5mm.
Results
Seventy-five patients were enrolled, and 69 completed, the trial. The mean active treatment time was 1.7 years and mean age was 14.4 years (SD 1.5) at start of retention. Although there were statistically significant differences for some of the parameters measured, there were no clinically significant differences between the three retention methods. All three were equally effective in retaining orthodontic treatment results and controlling relapse to a clinically significant level even when the results were adjusted for cooperation, initial crowding, growth and gender. The major part of relapse took place during the first year of retention.
Conclusions
All three retention methods, V-CTC, V-S and P, retained the orthodontic treatment results and prevented relapse within clinically acceptable levels. Most relapse took place within the first year of retention and changes during the second year were small or negligible.
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References
Littlewood SJ, Millett DT, Doubleday B, Bearn DR, Worthington HV . Retention procedures for stabilizing tooth position after treatment with orthodontic braces. Cochrane Database Syst Rev 2006; 25: CD002283.
Little RM . The Irregularity Index: a quantitive score of mandibular anterior alignment. Am J Orthod 1975; 68: 554–63.
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Additional information
Address for correspondence: Department of Orthodontics, University of Malmo, Malmo, Sweden. E-mail: gudrunedmantynelius@gmail.com
Edman Tynelius G, Bondemark L, Lilja-Karlander E. A randomized controlled trial of three orthodontic retention methods in class I four premolar extraction cases – stability after 2 years in retention. Orthod Craniofac Res 2013; 16: 105–115.
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Walker, M. No differences seen in outcomes between three different methods of orthodontic retention. Evid Based Dent 14, 81–82 (2013). https://doi.org/10.1038/sj.ebd.6400951
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DOI: https://doi.org/10.1038/sj.ebd.6400951
