Download Patient compliance with orthodontic retainers in the postretention

ORIGINAL ARTICLE
Patient compliance with orthodontic retainers in
the postretention phase
Michael C. Pratt,a G. Thomas Kluemper,b and Adam F. Lindstromc
Lexington, Ky
Introduction: 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. Methods: 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). Results: 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. Conclusions: 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. (Am J Orthod Dentofacial Orthop 2011;140:196-201)
T
he 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.1 Current beliefs
are in contrast to the previous position that retainers
need not be worn once remodeling of the surrounding
periodontium is complete.2
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
From the University of Kentucky, Lexington.
a
Second-year resident, Division of Orthodontics, College of Dentistry.
b
Associate professor and chief, Division of Orthodontics, College of Dentistry.
c
Senior program system analyst, Department of Statistics.
The authors report no commercial, proprietary, or financial interest in the products or companies described in this article.
Reprint requests to: Michael C. Pratt, 3468 Milam Lane, Apt #383, Lexington, KY
40502; e-mail, [email protected].
Submitted, October 2009; revised and accepted, February 2010.
0889-5406/$36.00
Copyright Ó 2011 by the American Association of Orthodontists.
doi:10.1016/j.ajodo.2010.02.035
196
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 collagenfiber network takes 4 to 6 months to remodel, and the
supracrestal fibers remain deviated for more than 232
days.3 It is generally accepted that the retention phase
is completed within a year of finishing treatment.1
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.2
A considerable amount of research has been published about orthodontic relapse. Binda et al4 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 al5 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
Pratt, Kluemper, and Lindstrom
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 Kierl6 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 al7 found high selfesteem 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 al8 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 al9 in 2006. They
concluded that there is insufficient evidence on which
to base orthodontic retention practices. Kouguchi
et al10 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 Freer11 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 vacuumformed retainers (VFRs). Hichens et al12 in 2007 surveyed
patient satisfaction with Hawley retainers and VFRs at 3and 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.12 In 1993, Stratton
and Burkland13 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
197
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.
RESULTS
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 (chisquare, 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
American Journal of Orthodontics and Dentofacial Orthopedics
August 2011 Vol 140 Issue 2
Pratt, Kluemper, and Lindstrom
198
Fig 1. The questionnaire.
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
August 2011 Vol 140 Issue 2
compliance. However, the same patient with VFRs has
only a 4% likelihood of proper retainer compliance.
Graphs were constructed to illustrate the reported
reasons for poor compliance wear. These reasons were
evaluated according to age and retainer type. Figure 2
gives reasons for noncompliance according to 3 age
groups: under 18 years old, 18 to 35 years old, and
over 35 years old. Figure 3 shows the reasons for noncompliance as a function of the types of retainers the
patient had.
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Pratt, Kluemper, and Lindstrom
199
Table. Logistic regression model predictions of patient compliance with VFR and Hawley retainers
Patient reports not being instructed to wear retainers every night
Female
VFR
Time braces off (y)
0.5
2
4
6
Hawley
Time braces off (y)
0.5
2
4
6
Age
15
87%
26%
2%
\1%
20
86%
30%
3%
\1%
15
77%
30%
5%
1%
20
75%
34%
8%
1%
30
84%
37%
6%
1%
40
81%
44%
13%
3%
30
71%
41%
17%
5%
40
67%
49%
32%
18%
Age
Male
VFR
Time braces off (y)
0.5
2
4
6
Hawley
Time braces off (y)
0.5
2
4
6
Age
15
81%
19%
1%
\1%
20
80%
21%
2%
1%
15
68%
22%
3%
\1%
20
66%
24%
5%
1%
15
91%
34%
3%
\1%
20
90%
38%
4%
\1%
15
83%
38%
7%
1%
20
81%
42%
11%
2%
30
76%
37%
4%
\1%
40
73%
34%
9%
2%
30
61%
31%
11%
3%
40
56%
38%
23%
12%
30
88%
46%
9%
1%
40
86%
54%
18%
4%
30
78%
50%
22%
8%
40
74%
58%
40%
24%
Age
Patient reports being instructed to wear retainers every night
Female
VFR
Time braces off (y)
0.5
2
4
6
Hawley
Time braces off (y)
0.5
2
4
6
Age
15
94%
45%
4%
\1%
20
93%
49%
6%
\1%
15
88%
49%
11%
2%
20
87%
53%
16%
3%
30
92%
57%
13%
2%
40
90%
64%
26%
6%
30
85%
61%
31%
11%
40
82%
68%
51%
33%
Age
DISCUSSION
An important discovery in this study was the differing
effect of time on retainer compliance based on the retainer type (P 5 0.0006). An analysis of the responses
in this study suggests that patients were more compliant
with VFRs than with Hawley retainers from the time they
were debonded until approximately 2 years after debonding. This agrees with a study by Hichens et al12
who found that retainer compliance was greater with
VFRs than with Hawley retainers at 3 and 6 months after
debonding. However, we also found that retainer compliance with VFR retainers decreased at a much faster rate
than with Hawley retainers. At approximately 2 years
postdebonding, retainer compliance was equal in patients with Hawley retainers and VFRs. After 2 years postdebonding, greater compliance was seen in patients with
Hawley retainers. Because of the greater decrease in compliance over time with VFRs, the logistic model found
that retainer compliance overall was greater with Hawley
retainers. This long-term effect of time on retainer compliance with different types of removable retainers has
never before been described in the literature.
One possible explanation for the faster decrease in retainer compliance with VFRs is differences in durability
Male
VFR
Time braces off (y)
0.5
2
4
6
Hawley
Time braces off (y)
0.5
2
4
6
Age
Age
between the 2 retainer types. Because VFRs cover the occlusal surfaces, they tend to break down under the stresses
of functional and parafunctional activities. For the most
part, Hawley retainers do not cover the occlusal surfaces
and are therefore less vulnerable to wear over time. Another factor that might influence compliance is the increased time required to maintain and clean a VFR. The
wear and the flexibility of the VFR make it more susceptible to fractures, stains, and absorption of oral fluids.
One might think that the initially higher rate of compliance with VFRs could be explained by esthetic considerations. It stands to reason that if a patient is going to
wear a retainer full time (as is done in the retention phase),
he or she would be more likely to wear a clear retainer that
is less conspicuous. However, this study did not support
that speculation. Our data demonstrated that only 5%
of the noncompliant subjects reported esthetics as the
reason. Furthermore, the percentages of people who listed
esthetic concerns as a reason for not wearing their retainers were equal for patients with Hawley retainers
and VFRs. Therefore, the reason for greater compliance
with VFRs after debonding has yet to be explained.
One issue that was not addressed in this study was the
frequency of follow-up visits. The policy at the University
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Pratt, Kluemper, and Lindstrom
200
Fig 2. Reasons for noncompliance by age.
Fig 3. Reasons for noncompliance by retainer type.
of Kentucky is to have several retainer checks during the
first year after debonding. These visits typically occur
at 6 weeks, 3 months, 6 months, and 1 year after debonding. After the first year, retainer checks typically occur
annually. However, not all patients return for their
retainer-check appointments. Retainer checks have several benefits, including reinforcing proper retainer wear,
examining retainers for breakages and wear, evaluating
the fit of the retainers, and identifying any other problems
related to retention. In this study, we did not identify the
frequency of the respondents’ retainer checks. It is likely
that those who returned for these follow-up visits would
be more likely to have proper retainer compliance.
Another factor that might affect our results was the
high percentage of nonrespondents in this study. Although this model is a good indicator of how the above
factors impact patient compliance with retainers, the
model would most likely better represent the general population if there had been more respondents. It is reasonable to assume that nonrespondents were less compliant
on average with orthodontic retainers than those who did
respond. Therefore, the actual averages of retainer
August 2011 Vol 140 Issue 2
compliance are most likely lower than those reported
here. It was not possible in this study to estimate the degree of difference if everyone who was surveyed had responded.
There seems to be a shift occurring among practicing
orthodontists in the type of removable retainers they prescribe. Historically, the Hawley has been the favored retainer type, but recently the VFR seems to have gained
favor. Fabrication of VFRs is less expensive and can be
completed in-house in many practices.12 This study suggests that perhaps this shift in retention protocol should
be reevaluated. However, this proposed shift in orthodontists’ retainer preferences is anecdotal. No published studies could be found to support or refute this observation.
Several other trends were identified in the logistic regression model. Female patients were more likely to wear
their retainers than males (P 5 0.0022). Younger patients
were more likely to initially be complaint with retainer
wear than older patients; however, as time out of braces
increased, the compliance of younger patients decreased
at a faster pace than that of older patients (P 5
0.0029). Patients who understood proper retainer
American Journal of Orthodontics and Dentofacial Orthopedics
Pratt, Kluemper, and Lindstrom
compliance were more likely to be compliant than those
who did not (P 5 0.0001). Overall, compliance with retainer wear decreased as time out of braces increased
(P \0.0001).
A treatment recommendation based on the data from
this study might be that improved patient compliance
would result from initial use of a VFR, followed by the
long-term prescription of a Hawley retainer. Timing for
the change should be about 2 years and could approximately coincide with the transition between the retention and postretention phases. The results of this study
also suggest that, although compliance is better with
Hawley retainers than with VFRs, overall patient compliance with removable retainers is not acceptable, and
fixed retention should be evaluated as a potentially preferred alternative to removable retainers.
CONCLUSIONS
The results of this study supported the following
conclusions.
1.
2.
3.
Patient compliance is greater with VFRs initially but,
overall, is greater with Hawley retainers.
The following variables were significant determinants of patient compliance: the patient’s understanding of proper retainer compliance, the
amount of time since debonding, the patient’s
age, the patient’s sex, and the type of retainer.
Esthetic concerns were not a significant determinant of patient compliance.
201
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