Patient compliance with orthodontic retainers in

the postretention phase

Michael C. Pratt,
a
G. Thomas Kluemper,
b
and Adam F. Lindstrom
c
Lexington, Ky
Introduction: Retention is an important, even critical, component of orthodontic treatment. There is little re-
search 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 nished full xed
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 regres-
sion 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 rst 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 fromHawley retainers to VFRs. An unexpected nding was that patients reported fewesthetic
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 reten-
tion therapy have changed and continue to change
over the years. It is currently believed that ortho-
dontic 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 reten-
tion phase and a postretention phase of therapy. The re-
tention phase consists of the time during which the
periodontium remodels after the skeletal and dental
changes associated with orthodontic treatment. The var-
ious components that constitute the periodontium
complete this process over varying lengths of time. For
example, reorganization of the periodontal ligament oc-
curs over a 3- to 4-month period. The gingival collagen-
ber network takes 4 to 6 months to remodel, and the
supracrestal bers remain deviated for more than 232
days.
3
It is generally accepted that the retention phase
is completed within a year of nishing treatment.
1
The postretention phase of treatment continues for
the remainder of the patients 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 re-
tainers should be worn during these posttreatment
phases vary among orthodontists.
2
A considerable amount of research has been pub-
lished about orthodontic relapse. Binda et al
4
found
that posttreatment changes were more pronounced in
males than in females, and less pronounced in older pa-
tients. These authors also discovered that signicant re-
lapse occurs for at least 5 years after treatment. In
a study of beagle dogs, van Leeuwen et al
5
found that
the duration of the retention phase was inversely corre-
lated to the total amount of relapse. Moreover, the abil-
ity of retention to prevent relapse was also inversely
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 nancial interest in the prod-
ucts or companies described in this article.
Reprint requests to: Michael C. Pratt, 3468 Milam Lane, Apt #383, Lexington, KY
40502; e-mail, mcprat2@uky.edu.
Submitted, October 2009; revised and accepted, February 2010.
0889-5406/$36.00
Copyright 2011 by the American Association of Orthodontists.
doi:10.1016/j.ajodo.2010.02.035
196
ORIGINAL ARTICLE
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 per-
sonal 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
6
at-
tempted to predict orthodontic cooperation with re-
tainers by looking at attitudes toward treatment, social
desirability, need for approval, and need for achieve-
ment. None of these variables proved to be a reliable
predictor of compliance. Mehra et al
7
found high self-
esteem and self-condence to be positively correlated
with retainer compliance. In their study of factors asso-
ciated with patient compliance with intraoral elastics
and headgear wear, Egolf et al
8
found the associated
pain and inconvenience of those appliances to be in-
versely 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 reten-
tion was completed by Littlewood et al
9
in 2006. They
concluded that there is insufcient evidence on which
to base orthodontic retention practices. Kouguchi
et al
10
showed that 60% to 70% of patients and parents
had forgotten the necessity of retainer wear after ortho-
dontic treatment. A 2006 survey study of retainer com-
pliance by Wong and Freer
11
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
12
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.
12
In 1993, Stratton
and Burkland
13
reported that less acrylic coverage on
the palate reduced speech difculties and decreased
gagging reexes. This in turn led to increased patient
comfort.
Many sources have conrmed 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 nished full xed appli-
ance therapy in either the orthodontic graduate clinic or
the orthodontic faculty practice at the University of Ken-
tucky between 6 months and 6 years from the time the
questionnaire was mailed. Patients who had been out
of full xed appliance therapy for less than 6 months
were not surveyed because they were considered to be
in the retention phase of treatment. The returned ques-
tionnaires did not identify the respondents. One thou-
sand eighty-ve 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 rst 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 identiers that
allowed the respondents to be classied into subgroups.
These identiers 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 rst 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 re-
minder 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 classied 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 signicant 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 signicant
variables. There were interaction effects for 2 pairs of
Pratt, Kluemper, and Lindstrom 197
American Journal of Orthodontics and Dentofacial Orthopedics August 2011 Vol 140 Issue 2
these variables, leading to subtleties in the model inter-
pretation. 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.
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 non-
compliance as a function of the types of retainers the
patient had.
Fig 1. The questionnaire.
198 Pratt, Kluemper, and Lindstrom
August 2011 Vol 140 Issue 2 American Journal of Orthodontics and Dentofacial Orthopedics
DISCUSSION
An important discovery in this study was the differing
effect of time on retainer compliance based on the re-
tainer 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 de-
bonding. This agrees with a study by Hichens et al
12
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 compli-
ance with VFR retainers decreased at a much faster rate
than with Hawley retainers. At approximately 2 years
postdebonding, retainer compliance was equal in pa-
tients with Hawley retainers and VFRs. After 2 years post-
debonding, greater compliance was seen in patients with
Hawley retainers. Because of the greater decrease incom-
pliance 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 com-
pliance with different types of removable retainers has
never before been described in the literature.
One possible explanation for the faster decrease in re-
tainer compliance with VFRs is differences in durability
between the 2 retainer types. Because VFRs cover the oc-
clusal 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. An-
other factor that might inuence compliance is the in-
creased time required to maintain and clean a VFR. The
wear and the exibility of the VFR make it more suscep-
tible to fractures, stains, and absorption of oral uids.
One might think that the initially higher rate of com-
pliance with VFRs could be explained by esthetic consid-
erations. 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 re-
tainers 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
Table. Logistic regression model predictions of patient compliance with VFR and Hawley retainers
Patient reports not being instructed to wear retainers every night
Female Male
VFR Age VFR Age
Time braces off (y) 15 20 30 40 Time braces off (y) 15 20 30 40
0.5 87% 86% 84% 81% 0.5 81% 80% 76% 73%
2 26% 30% 37% 44% 2 19% 21% 37% 34%
4 2% 3% 6% 13% 4 1% 2% 4% 9%
6 \1% \1% 1% 3% 6 \1% 1% \1% 2%
Hawley Age Hawley Age
Time braces off (y) 15 20 30 40 Time braces off (y) 15 20 30 40
0.5 77% 75% 71% 67% 0.5 68% 66% 61% 56%
2 30% 34% 41% 49% 2 22% 24% 31% 38%
4 5% 8% 17% 32% 4 3% 5% 11% 23%
6 1% 1% 5% 18% 6 \1% 1% 3% 12%
Patient reports being instructed to wear retainers every night
Female Male
VFR Age VFR Age
Time braces off (y) 15 20 30 40 Time braces off (y) 15 20 30 40
0.5 94% 93% 92% 90% 0.5 91% 90% 88% 86%
2 45% 49% 57% 64% 2 34% 38% 46% 54%
4 4% 6% 13% 26% 4 3% 4% 9% 18%
6 \1% \1% 2% 6% 6 \1% \1% 1% 4%
Hawley Age Hawley Age
Time braces off (y) 15 20 30 40 Time braces off (y) 15 20 30 40
0.5 88% 87% 85% 82% 0.5 83% 81% 78% 74%
2 49% 53% 61% 68% 2 38% 42% 50% 58%
4 11% 16% 31% 51% 4 7% 11% 22% 40%
6 2% 3% 11% 33% 6 1% 2% 8% 24%
Pratt, Kluemper, and Lindstrom 199
American Journal of Orthodontics and Dentofacial Orthopedics August 2011 Vol 140 Issue 2
of Kentucky is to have several retainer checks during the
rst year after debonding. These visits typically occur
at 6 weeks, 3 months, 6 months, and 1 year after debond-
ing. After the rst year, retainer checks typically occur
annually. However, not all patients return for their
retainer-check appointments. Retainer checks have sev-
eral benets, including reinforcing proper retainer wear,
examining retainers for breakages and wear, evaluating
the t 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. Al-
though 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 pop-
ulation if there had been more respondents. It is reason-
able to assume that nonrespondents were less compliant
on average with orthodontic retainers than those who did
respond. Therefore, the actual averages of retainer
compliance are most likely lower than those reported
here. It was not possible in this study to estimate the de-
gree of difference if everyone who was surveyed had re-
sponded.
There seems to be a shift occurring among practicing
orthodontists in the type of removable retainers they pre-
scribe. Historically, the Hawley has been the favored re-
tainer 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 sug-
gests that perhaps this shift in retention protocol should
be reevaluated. However, this proposed shift in orthodon-
tists retainer preferences is anecdotal. No published stud-
ies could be found to support or refute this observation.
Several other trends were identied in the logistic re-
gression model. Female patients were more likely to wear
their retainers than males (P 50.0022). 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
Fig 3. Reasons for noncompliance by retainer type.
Fig 2. Reasons for noncompliance by age.
200 Pratt, Kluemper, and Lindstrom
August 2011 Vol 140 Issue 2 American Journal of Orthodontics and Dentofacial Orthopedics
compliance were more likely to be compliant than those
who did not (P 5 0.0001). Overall, compliance with re-
tainer 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 approxi-
mately coincide with the transition between the reten-
tion and postretention phases. The results of this study
also suggest that, although compliance is better with
Hawley retainers than with VFRs, overall patient compli-
ance with removable retainers is not acceptable, and
xed retention should be evaluated as a potentially pre-
ferred alternative to removable retainers.
CONCLUSIONS
The results of this study supported the following
conclusions.
1. Patient compliance is greater with VFRs initially but,
overall, is greater with Hawley retainers.
2. The following variables were signicant determi-
nants of patient compliance: the patients under-
standing of proper retainer compliance, the
amount of time since debonding, the patients
age, the patients sex, and the type of retainer.
3. Esthetic concerns were not a signicant determi-
nant of patient compliance.
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