INTRODUCTION

Retention is a necessary therapeutic phase following active orthodontic treatment, with the goal of maintaining the obtained intra-arch alignment and interarch relationships. After the conclusion of active treatment, many physiological forces can move teeth back to their original positions, including supracrestal and gingival PDL fibers, eruptive forces, and deleterious habits developed by patients.1,2 Therefore, some type of retention is thought to be required indefinitely to prevent relapse.2 Because of the importance of retention, a systematic organization of the retention phase, including choice of retainer and time management, is essential to the success of both the orthodontic treatment and the orthodontic practice.

Many factors should be considered when deciding what type of retainer to give each patient.2–4 Orthodontists in the Netherlands consider the following factors in descending order of frequency: pretreatment situation, interdigitation after treatment, oral hygiene, end result, periodontal tissue, patient motivation, and patient age.4 Studies in the United States have been limited to determining the frequency with which retainers are used and comparing types of retainers to each other.5–12 Keim et al.5 found that the use of the Hawley retainer has recently decreased while the use of clear retainers and bonded retainers has increased. Valiathan and Hughes13 showed that the Hawley retainer is the most common retainer used in the maxillary dentition, whereas a fixed lingual retainer is the most common retainer used in the mandibular dentition. Essix retainers have been shown to be equally as effective in preventing relapse, more cost-effective, and more preferred by patients when compared to Hawley retainers.6,14

According to Hughes et al.,15 businesses that thrive in a competitive environment have defined and effective strategies for clinical practice. More specifically, an efficient, successful orthodontic practice is one that capitalizes on a high number of active cases and minimizes overhead.16 Because the retention phase often involves four appointments over a 2-year period,5 missed appointments may impact the clinical efficiency of the orthodontic practice. Schulman and McGill17 found that patients are three times more likely to miss an appointment during retention than during active treatment. Therefore, it is critical that orthodontists have a protocol for patient visits during the retention phase.

Despite the inherent importance of retention, how orthodontists choose the type of retainer to use for each patient and how this choice affects the retention recall schedule have not been examined. The goal of this study was to test the null hypothesis that there is no influence of orthodontist characteristics and factors related to retainer choice on the management of the retention phase with regard to frequency and duration of follow-up care provided.

MATERIALS AND METHODS

A Web-based survey was developed to examine how orthodontists manage the retention phase. Questions asked about participant demographics, the types of retainers used, how the choice of retainer was made for each patient, and how frequently and for how long participants scheduled appointments. Following approval by the Institutional Review Board of Virginia Commonwealth University, the American Association of Orthodontists randomly selected 1000 orthodontists throughout the United States to receive the survey. The online link to the survey was then sent via e-mail to those selected, with a follow-up e-mail sent 4 weeks later in an effort to increase participation.

The results were collected and summary descriptive statistics were calculated. In order to determine the variables that were associated with the duration or frequency of the retention phase, univariate analyses (analysis of variance or correlation, as indicated) were performed using SAS software (JMP 9.0.2; SAS Institute Inc, Cary, NC).

RESULTS

The survey was sent to 1000 orthodontists and had a return rate of 89.4% (n  =  894). The demographic characteristics of the participants in the survey are shown in Figures 1 and 2. While the male-to-female ratio of participants was 4∶1, the number of years in practice of each participant was evenly distributed between 0 and >35 years. Since age, number of years in practice, and year of graduation from orthodontic residency were highly correlated (|r| > .92), practitioner experience will be described by year of graduation from orthodontic residency.

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Retainer Choice

When asked if there should be a standard of care regarding retention procedures and appliances, 56% of participants responded Yes, and 44% responded No. When determining the type of retainer to use, 54% of the respondents indicated that they do so at the end of treatment, while 43% decided during initial treatment planning, and 3% decided during treatment. Over 81% of respondents stated they use bonded, Hawley, and vacuum-formed retainers (VFRs) in their practice. The frequency of various factors considered that pertain to retainer choice and prescription are shown in Figure 3. Pretreatment malocclusion, compliance, oral hygiene, and the patient's desires were considered by more than 80% of participants, whereas the presence of third molars, gender, and insurance were each considered by less than 10% of participants. Though not statistically significant, patient desires were considered less frequently as practitioner experience increased. The participants discussed the choice of retainer 3% of the time with the patient's dentist compared to 41% of the time with the patient's periodontist, when applicable.

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For those respondents who prescribed removable retainers, 52.3% prescribed them to be worn on a part-time basis. Of this group, 99.6% asked the patients to wear the retainer only at night, as opposed to during the day only or every other day.

Time Management

Over 90% of orthodontists saw their patients for 15 minutes or less at each appointment. Figure 4 shows the frequency of appointments and duration of follow-up care during the retention phase. Follow-up care for ≤12 months was offered by 28% of orthodontists. For these orthodontists, the frequency of visits was predominantly quarterly (74%). This is in contrast to the orthodontists who offered follow-up for 13–24 months (42%) or more than 24 months (31%), with frequency of visits being predominantly semiannual (56% and 55%, respectively). Yearly visits were rare (less than 6%). For all of the following results, the number of follow-up visits was calculated by combining frequency of visits and duration of retention phase, as shown by the numbers atop each bar in Figure 4.

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The presence of third molars and whether the patients were “special needs” were the only factors considered when choosing the type of retainer that had a significant impact on the number of follow-up visits (Table 1). Orthodontists who considered the presence of third molars had significantly more follow-up visits than those who did not (mean  =  5.4 visits vs 4.8 visits; P  =  .03). Orthodontists who considered special needs had significantly more follow-up visits than those who did not (mean  =  5.1 versus 4.7; P  =  .02).

Table 1. Number of Follow-up Visits vs Factors Considered When Choosing the Type of Retainer^a

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The type of retainer chosen was unrelated to the number of follow-up visits (P > .08) except for orthodontists who used a VFR (Table 2). For orthodontists who used a VFR, the average number of visits was eight, compared to five for orthodontists who did not use a VFR (P  =  .02). Full- versus part-time removable retainer use was not related to the number of follow-up visits (P > .07).

Table 2. Number of Follow-up Visits vs Type of Retainer Used^a

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As practitioner experience increased, so did the number of prescribed retention visits (P < .0001; Table 3). Those who graduated prior to 1980 averaged 5.4 visits, which was significantly greater than the average number of visits (4.5) for those who graduated as recently as 1990.

Table 3. Number of Follow-up Visits vs Year of Graduation From Orthodontic Residency^a

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Slightly more than half (51%) of the surveyed orthodontists considered retention as a joint responsibility between the orthodontist and the patient, while 47% considered the responsibility to fall on the patient, and less than 3% considered the responsibility to fall solely on the orthodontist. Orthodontists who considered the primary responsibility of retention to fall on the patient had significantly fewer (P < .0001) follow-up visits than those who considered it either a joint or orthodontist-only responsibility (mean  =  4.5 vs 5.2, respectively). Of those who graduated prior to 1990 and viewed retention as fully or partially their own responsibility, 44% recommended more than a 2-year follow-up period. Of the recent graduates (1990 and after) who viewed retention as fully or partially their own responsibility, 28% recommended more than a 2-year follow-up period.

DISCUSSION

The null hypothesis was rejected because the frequency and duration of follow-up visits during the retention phase was affected by practitioner experience, whether VFRs were used, whether the orthodontist considered the presence of third molars or special-needs patients when choosing the type of retainer, and to whom the orthodontist attributed responsibility during the retention phase.

Orthodontists rarely considered the presence of third molars when deciding what type of retainer to prescribe. However, despite evidence that the presence or absence of third molars does not impact alignment of incisors following retention,18 orthodontists who did consider the presence of third molars had significantly more follow-up visits (P  =  .03) during the retention phase than those who did not. This increase in visits may have been in part due to patient concerns and the general perception that third molars cause anterior crowding, even without supporting scientific evidence.

Although orthodontists considered whether the patients were special needs only 48% of the time when deciding what type of retainer to prescribe, those that did had significantly more follow-up visits than those who did not (mean  =  5.1 versus 4.7; P  =  .02). Special-needs patients are often more challenging to treat due to behavioral issues,19 so it was not surprising that orthodontists wanted to see these patients more often to ensure that the final results of treatment were maintained.

When a VFR was prescribed, there was a significantly smaller average number of visits compared to when other retainers were prescribed (P  =  .02). These findings were consistent with those from the study of Valiathan and Hughes13 that showed retention appointments were scheduled at longer time intervals when orthodontists prescribed VFRs. VFRs have been shown to have smaller increases in the Irregularity Index and smaller decreases in PAR (peer assessment rating) scores six months following debonding.20 Therefore, it is reasonable to assume that when orthodontists prescribed VFRs, they were less worried about the relapse than they would have been had they prescribed other retainers. However, because patient compliance with VFRs has been shown to decrease more rapidly 2 years after debonding than with Hawley retainers, it would be prudent to monitor patients who receive VFRs for more than 2 years.21

Overall, most orthodontists averaged the same number of visits (approximately four) for the patients during the retention phase, indicating that orthodontists placed a similar importance on retention. However, the distribution of the visits varied greatly. For those orthodontists who saw patients for ≤12 months, the patients were typically seen quarterly, thus averaging four visits. For those orthodontists who saw patients for 12–24 months, the patients were typically seen semi-annually, also averaging four visits. However, when examining orthodontists with regard to experience level, the number of visits significantly increased (P < .0001) as practitioner experience increased. These results were similar to the findings of Valiathan and Hughes13 that orthodontists with less than 16 years of experience scheduled retention appointments less frequently. More experienced practitioners might have been more dubious of patient compliance over the long term, having seen more cases of relapse over the length of their career.

Furthermore, when examining orthodontists with regard to their belief as to who bears responsibility during the retention phase, those who believed that the patient bears sole responsibility had significantly fewer visits (P < .0001). The number of visits increased as orthodontists' perception of their own responsibility increased. Orthodontists who considered retention a joint or orthodontist-only responsibility probably wanted to keep a closer watch on their patients than those who believed otherwise.

CONCLUSIONS

• The number of follow-up visits increased if the orthodontists considered the presence of third molars or special needs patients when deciding the type of retainer to use.

• The number of follow-up visits increased as practitioner experience increased.

• The number of follow-up visits decreased when a VFR was used and when orthodontists considered the primary responsibility for retention to fall on the patient.