EFFICACY OF TEMPORARY FIXED RETENTION FOLLOWING ...

Horowitz and Hixon (1969, p 4) described physiologic recovery as, “The
type of posttreatment changes that represent a rebound or reversion toward the
original malocclusion.” Based on this premise, it could be assumed that cases
that exhibit greater severity of pretreatment malocclusion and undergo the most
in-treatment changes could be expected to exhibit a greater degree of
posttreatment relapse. This was demonstrated in a recent study at the University
of Washington involving 86 patients was undertaken to identify factors
associated with stability (Ormiston et al. 2005). The authors found the initial
severity of malocclusion to be negatively correlated with posttreatment stability.
They concluded that patients with more severe index scores before treatment
tended to be less stable.
This common trend also was evident in the present study (Figure 5-2).
There is a significant statistical association between the amount of change during
treatment and the amount of relapse (P = 0.0084). Prediction of the amount of
relapse from the treatment change takes the form of Y = 1.26 – 0.13(X) for the 166
cases in this study, meaning that a 1.0 mm change in Incisor Irregularity is
associated with 0.13 mm of relapse.
The premise of posttreatment orthodontic retention is based on
histological research that shows that it takes time for the surrounding
periodontal tissues to reorient themselves following tooth movement (Reitan
1959, 1967; Rygh et al. 1986). Reorganization of the periodontal ligament is
estimated to occur over a 3 to 4 month period of time following treatment (Reitan
1959, 1967, 1969; Melrose and Millett 1998), whereas the gingival collagen-fiber
network typically takes 4 to 6 months to be remodeled, and the elastic
supracrestal fibers have been shown to remain deviated for more than 232 days
(Reitan 1967; Melrose and Millett 1998). According to Paulson (1992), bonded
retainers should be left in place for only 3 to 4 years, except in cases involving
adolescent patients still undergoing their adolescent growth spurt, because any
longer than 4 years exceeds the recommendation from Reitan’s work (1959, 1969)
in regards to the time necessary for elastic fiber reorganization. The results of the
present study do not support this. In the sample of 166 cases at an average of 15
years postretention, there existed only a 0.6 mm difference in mandibular Incisor
Irregularity between those cases receiving mandibular fixed retention for
approximately 2-3 years and those receiving only removable Hawley retainers
for the same period of time.
Despite no apparent long-term benefit, some orthodontists might consider
that the use of temporary fixed retention affords other benefits. Typically, most
comprehensive treatment is completed around the age of 16. By instituting fixed
retention for a couple of years at this age, the patient is carried through
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