Retention is an important, even critical, component of orthodontic treatment. There is little research on practice protocols and patient compliance with long-term or short-term retention. This lack of information leaves our specialty with many opinions and practice protocols. The purposes of this study were to evaluate and quantify orthodontic retainer wear according to several variables, including patient age, sex, time in retention, and retainer type, and to identify predictors of compliance and reasons for noncompliance with removable orthodontic retainers.
Questionnaires were mailed to patients who finished full fixed appliance therapy in either the orthodontic graduate clinic or the orthodontic faculty practice at the University of Kentucky within the past 6 years. Of the 1085 questionnaires mailed, 280 were returned (25.8%). A logistic regression model that described the probabilities of retainer wear was created ( P <0.0001).
Patient compliance was greater with vacuum-formed retainers (VFRs) for the first 2 years after debonding. However, compliance with VFRs decreased at a much faster rate than with Hawley retainers. Because of this, patient compliance was greater with Hawley retainers at any time longer than 2 years after debonding, and patient compliance overall was greater with Hawley retainers.
This evidence disagrees with the current anecdotal trend of orthodontists who favor switching from Hawley retainers to VFRs. An unexpected finding was that patients reported few esthetic concerns about retainers, and the few that were reported were equally distributed between Hawley retainers and VFRs.
The practice and the theory of orthodontic retention therapy have changed and continue to change over the years. It is currently believed that orthodontic patients should wear their retainers nightly throughout their life after treatment if they desire to maintain optimal dental alignment. Current beliefs are in contrast to the previous position that retainers need not be worn once remodeling of the surrounding periodontium is complete.
After orthodontic treatment, there are both a retention phase and a postretention phase of therapy. The retention phase consists of the time during which the periodontium remodels after the skeletal and dental changes associated with orthodontic treatment. The various components that constitute the periodontium complete this process over varying lengths of time. For example, reorganization of the periodontal ligament occurs over a 3- to 4-month period. The gingival collagen-fiber network takes 4 to 6 months to remodel, and the supracrestal fibers remain deviated for more than 232 days. It is generally accepted that the retention phase is completed within a year of finishing treatment.
The postretention phase of treatment continues for the remainder of the patient’s life. During this phase, movement of teeth can occur in response to changing forces in the periodontium caused by continued growth and development. Orthodontic retainers are worn during this phase to offset the effects of these changing forces. Practices regarding the frequency and length of time retainers should be worn during these posttreatment phases vary among orthodontists.
A considerable amount of research has been published about orthodontic relapse. Binda et al found that posttreatment changes were more pronounced in males than in females, and less pronounced in older patients. These authors also discovered that significant relapse occurs for at least 5 years after treatment. In a study of beagle dogs, van Leeuwen et al found that the duration of the retention phase was inversely correlated to the total amount of relapse. Moreover, the ability of retention to prevent relapse was also inversely correlated with the amount of tooth movement during treatment.
Because most orthodontic retainers are removable, patient compliance is an important factor in almost all cases. Many studies have focused on identifying personal characteristics strongly correlated with a compliant orthodontic patient. However, the data from much of this research have been contradictory, and other studies have yielded inconclusive results. Nanda and Kierl attempted to predict orthodontic cooperation with retainers by looking at attitudes toward treatment, social desirability, need for approval, and need for achievement. None of these variables proved to be a reliable predictor of compliance. Mehra et al found high self-esteem and self-confidence to be positively correlated with retainer compliance. In their study of factors associated with patient compliance with intraoral elastics and headgear wear, Egolf et al found the associated pain and inconvenience of those appliances to be inversely correlated with compliance. It stands to reason that this inverse relationship would apply to retainer wear as well.
Little research has been published regarding retainer compliance. A systematic review of orthodontic retention was completed by Littlewood et al in 2006. They concluded that there is insufficient evidence on which to base orthodontic retention practices. Kouguchi et al showed that 60% to 70% of patients and parents had forgotten the necessity of retainer wear after orthodontic treatment. A 2006 survey study of retainer compliance by Wong and Freer concluded that there was a strong relationship between retainer compliance and how comfortable the patient thought the retainer was to wear.
There have also been few published studies regarding retainer compliance with Hawley retainers vs vacuum-formed retainers (VFRs). Hichens et al in 2007 surveyed patient satisfaction with Hawley retainers and VFRs at 3- and 6-month posttreatment intervals. They found that patients in orthodontic retention experienced equal levels of discomfort regardless of the retainer type. Patients with VFRs reported an overall higher level of satisfaction and fewer breakages. In 1993, Stratton and Burkland reported that less acrylic coverage on the palate reduced speech difficulties and decreased gagging reflexes. This in turn led to increased patient comfort.
Many sources have confirmed a lack of evidence on orthodontic practice protocols and patient compliance with retention. This leaves our specialty with a multitude of opinions and practice protocols. The purposes of this study were to evaluate and quantify retainer compliance during the postretention phase according to several variables, including patient age, sex, time in retention, and retainer type. Our goal was to identify predictors of compliance and reasons for noncompliance.
Material and methods
This study was conducted via a questionnaire that was mailed to patients who had finished full fixed appliance therapy in either the orthodontic graduate clinic or the orthodontic faculty practice at the University of Kentucky between 6 months and 6 years from the time the questionnaire was mailed. Patients who had been out of full fixed appliance therapy for less than 6 months were not surveyed because they were considered to be in the retention phase of treatment. The returned questionnaires did not identify the respondents. One thousand eighty-five patients were surveyed, ranging in age from 8 to 72 years. The questionnaire was sent twice to these patients, with the second mailing arriving 3 months after the first as a reminder to those who had not yet responded. The surveyed patients included those from both rural and urban environments with various socioeconomic backgrounds. The study was conducted between January and July 2008.
The questionnaires included several identifiers that allowed the respondents to be classified into subgroups. These identifiers included age, length of time since debonding, sex, and retainer type. In addition, each respondent was asked to identify how often he or she was instructed to wear the retainers, how often the retainers were actually worn, and any reasons for not wearing the retainers as instructed. This questionnaire is shown in Figure 1 .
The first batch of questionnaires was mailed in January 2008, resulting in 185 completed and returned questionnaires. Three months later, a second copy of the questionnaire was sent with a reminder. The reminder yielded an additional 95 responses for a total of 280 (25.8%) questionnaires returned. Not everyone completed the entire questionnaire as instructed, so some data could not be classified into certain subgroups. For example, some respondents did not identify their sex.
A logistic regression model, which described the probabilities of retainer wear, was created based on the data. A likelihood ratio testing of model parameters was used to identify significant relationships (chi-square, 124.0485; df, 11 abbreviations). This logistic regression model found age, sex, amount of time out of braces, retainer type, and patient interpretation of proper retainer compliance to be statistically significant variables. There were interaction effects for 2 pairs of these variables, leading to subtleties in the model interpretation. The Table describes retainer compliance based on this model. It shows the predicted proper retainer compliance at ages 15, 20, 30, and 40. It is broken down to identify differences in instructions, retainer types, times out of braces, and sexes. For example, the Table indicates that a 40-year-old man who understands that he should wear his retainers every night and has been in retention for 6 years with Hawley retainers has a 24% probability of demonstrating proper retainer compliance. However, the same patient with VFRs has only a 4% likelihood of proper retainer compliance.
|Patient reports not being instructed to wear retainers every night|
|Time braces off (y)||15||20||30||40||Time braces off (y)||15||20||30||40|
|Time braces off (y)||15||20||30||40||Time braces off (y)||15||20||30||40|