A survey of protocols and trends in orthodontic retention
Andriekute et al. Progress in Orthodontics
A survey of protocols and trends in orthodontic retention
Alvyda Andriekute 0
Arunas Vasiliauskas 0
0 Clinic of Orthodontics, Lithuanian University of Health Sciences , Lukšos-Daumanto st. 6, LT-5016 Kaunas , Lithuania
Background: The objectives of this study were to evaluate retention procedures and protocols which are used by the orthodontists in Lithuania and to identify commonly used types of dental retainers. Methods: One hundred seven questionnaires in total with 28 multiple-choice questions were sent to all members of the Lithuanian Orthodontic Society. The questionnaire was organized into eight sections representing specific information about socio-demographic status of the respondents, selection of a retention system, details of commonly used fixed and removable retainers, the duration of the retention period, supervision of the retainers, instructions for patients, and necessity of common retention guidelines. Results: The overall response rate was 75.7%. All of the respondents prescribed retainers after the orthodontic therapy. More than 40% of the respondents combined fixed and removable retainers in different clinical situations, but the first-choice option after an expansion of the maxillary dental arch was the removable retainer (54.3%); meanwhile, a fixed retainer was used after a correction of any rotations of the mandibular anterior teeth (49.4%). The Hawley retainer was preferred by 90.1% of the respondents for a maxillary dental arch, and 74.1% of them preferred it for a mandibular dental arch. The most preferable fixed retainer was the retainer bonded to all six anterior teeth (in the upper dental arch-by 71.6%; in the lower one-by 80.2%). There was no consensus on the duration of a retention period. Most of the orthodontists checked up retainers three times during the first year (fixed ones-by 42.0%; removable ones-by 30.0%) and once per year after the 1-year retention period (fixed ones-by 44.4%; removable ones-by 40.7%). All orthodontists gave instructions for taking care of an orthodontic retainer. It was observed that the orthodontists with less than 10 years of experience used a protocol based on the skills learned during their postgraduate studies, while orthodontists with more than 10 years of experience used retention procedures based on their orthodontic work practice (p < 0.05). Conclusions: A combination of fixed and removable retainers was the most often used in an orthodontic retention. Evidence-based guidelines are desired for a common retention protocol.
Retention; Hawley retainer; Fixed retainer
There is no doubt that teeth after an active orthodontic
treatment have a tendency to move into the previous
position, and a relapse can occur at any age [
supragingival and transseptal fibers are most commonly
associated with a relapse; occlusal factors, soft tissue
pressures, and further growth are also some influencing
]. A relapse affects patients’ time and finances
and can cause esthetic discomfort because unfavorable
changes often appear in the front teeth. This situation
negatively affects both the patient and the doctor.
Orthodontic retainers which are made to be worn after
dental braces in order to maintain teeth in their correct
position are used to minimize any relapse.
Nevertheless, there is no agreement among the
orthodontists concerning the need for any retention, choosing
the type of a retainer, or determining how long retainers
should be worn after an orthodontic treatment. A large
number of variations in retention strategies, different
materials for retention, or individual patient factors can
lead to challenges of choosing retention protocols.
Orthodontic materials and methods are constantly
changing and manufacturers suggesting new alternatives.
Despite the fact that a growing number of surveys of
protocols and trends in orthodontic retention that have
been conducted in different countries have revealed
some tendencies between the orthodontists [
further studies are needed for the development of a
retention protocol. The common retention protocol is an
attempt to systemize and standardize retention
procedures which would be useful for orthodontists.
Meanwhile, no research has been accomplished on the most
often used dental retention system among Lithuanian
orthodontists. The main purposes of this study were to
evaluate the protocols and trends used in an orthodontic
practice and to identify any commonly used types of
The survey questionnaire was developed according to
similar studies [
] and edited and prepared in the
Lithuanian language. The questionnaire consisted of 28
multiple-choice questions, and it was divided into eight
parts representing some specific information. It was
possible to select one or even multiple answers from the list
Socio-demographic status of the respondents
Firstly, there was a socio-demographic status of the
respondents included, and they were asked to identify
their gender, university where they have completed their
postgraduate studies, the work sector, and length of their
independent work as an orthodontist after having
finished postgraduate studies.
Selection of a retention system
The second section examined if orthodontists used
retention appliances after orthodontic treatment, which
types of retainers were typically used for applied
treatment, conditions or malocclusions (for patients with
anterior open bite, impacted anterior teeth, etc.), and
factors influencing their selection of the retainer type.
Part 3 referred to the most often used fixed retainers
and the details of commonly used fixed retainers
(material, type, form, and diameter) and examined which teeth
were used for bonding in the upper and lower dental
arches and the methods and contraindications of
bonding a fixed retainer in finished cases.
The fourth section gathered information about the most
often used removable retainers (Hawley retainer, Begg
retainer, clear (vacuum-formed) retainer, etc.) for the
upper and lower dental arches.
The duration of the retention period
The fifth section consisted of questions about a
retention period—respondents were asked to note the
duration of the primary retention, prescription of wearing a
removable retainer during and after the primary
retention period, and details of wearing a fixed retainer.
Supervision of the retainers
Part 6 was dedicated to question who is responsible for
patients in retention and information on the number of
any follow-up visits per year after the prescription of
fixed or removable retainers.
Instructions for patients
The seventh part requested information if orthodontists
gave any instructions for the patient/patient’s parents
(written or verbal) about the maintenance of removable
or fixed retainers, which instructions are provided after
the bonding of a fixed retainer, which oral hygiene
measures are recommended for fixed retainers, and what are
the recommendations in case there are some issues with
retainer. Also, we gathered information if general
practitioners are involved in the maintenance of fixed
retainers and what are the recommendations if a dentist
during the examination has noticed a disengaged/broken
The necessity of common retention guidelines
Finally, respondents were asked to specify the reasons
for using a retention protocol and if they felt the
necessity of a general retention procedure protocol.
A questionnaire study was conducted from January to
March 2016 by handing out anonymous paper
questionnaires to orthodontists or sending electronic ones. The
names and email addresses of the orthodontists were
collected from the Lithuanian Association of
Orthodontists. Email remainders were sent a week later to those
who have not completed or partially completed the
survey. This action was repeated 2 weeks later. All members
of the Lithuanian Orthodontic Society were included in
A statistical analysis was performed by collecting data
and analyzing with the software package SPSS 21.0. The
data were expressed as a frequency and percentage.
Significance between differences was evaluated by a
chisquare test. The p value of < 0.05 was considered as
statistically significant. Binary logistic regression analyses
were carried out to identify any factors associated with
the choice of a retention according to the length of the
Socio-demographic status of the respondent
One hundred seven questionnaires were sent out, and
81 were returned completed. The attained response rate
was 75.7%. Altogether, 72 orthodontists and 9
postgraduate students returned the submitted surveys: 86.4%
of them were females and 13.6% were males. The
majority of the respondents (55.6%) were working only in the
full-time private practice sector, 19.8% mentioned a
combination of the public and the private practice
sectors, 2.5% worked at the university, and 1.2% were
retired (partly). Another 14.8% of the respondents worked
in the private practice sector, at the university, and in
the public clinic, while 6.2% of the orthodontists noted
the university and the public clinic as their workplaces.
A total of 74 orthodontists were trained in Lithuania
(56.8% at the Lithuanian University of Health Sciences,
43.2% at the Vilnius University), and the remaining 7
orthodontists were trained in other countries. The
orthodontists were asked to specify their work experience: 38
(46.9%) respondents had less than 10 years of experience
in the treatment of orthodontic patients, while 43
(53.1%) orthodontists had more than 10 years of working
Selection of a retention system
All respondents prescribed retainers after the orthodontic
treatment—bonded, removable, or both. A total of 87.7%
of the respondents to the question “What are the main
factors influencing the choice of a retention?” answered
that the main factor was the patient’s dental condition
before the treatment. The final result of the treatment,
interdigitation between the teeth, patient’s oral hygiene, and
periodontal tissue status were mentioned by the majority
of the orthodontists as the factors affecting orthodontists’
choice of the retention (Fig. 1).
A combination of a bonded and a removable retainer
was mostly used by the orthodontists in both dental
arches, except after expansion of the upper dental arch
when a removable retainer was dominant, and after the
correction of a rotation of the permanent mandibular
anterior teeth, the orthodontists preferred a fixed
retainer (Tables 1 and 2).
Three respondents (3.7%) used only removable
retainers, whereas 17 respondents (21.0%) used both fixed
and removable retainers in all cases.
The most preferred fixed retainer was the retainer
bonded to all anterior teeth (canine to canine). 80.2% of
respondents bonded a fixed retainer in the lower jaw to
all six anterior teeth, and 71.6% of them did it in the
upper jaw (Table 3).
The majority of the orthodontists (76.5%) adjusted the
arch wire retainers clinically. While choosing the
material for a fixed orthodontic retainer, 71.6% of the
respondents noted a stainless steel wire. Braided wire was
chosen by 75.3% of the specialists, and the dominant
form was a rectangular one (66.7%).
The most frequently mentioned contraindications for
fixed retainers were caries, a periodontal disease, poor
oral hygiene, deep bite, incomplete treatment result, and
the anatomical characteristics of the teeth (Fig. 2).
The most popular removable retainers in the upper and
lower dental arches were the Hawley and the
vacuumformed retainers (Table 4).
Request of parents/patient
Anatomy of teeth
Interdigitation between the teeth after
The final result of treatment
Situation before treatment
Values are presented as numbers (%)
The duration of the retention period
The duration of the retention period was from 1 month
to the entire life, and 1 year was the most frequently
mentioned as the first retention period by the
orthodontists (30.9%). The patients during this period should
wear their removable retainers for a certain amount of
time, and the range of this time varied from 6 to 24 h.
The most often mentioned answers were 24 h per day/
7 days per week (29.6% of the respondents). Thirty seven
percent of the orthodontists in total noted that the
removable retainers should be worn for 5 years and more
after the completion of an active tooth movement, while
others (34.6%) recommended to wear removable
retainers for 1–2 years. A vast majority of the respondents
(92.6%) did not remove any fixed retainers after the first
retention period unless the treatment of anterior teeth
was planned (49.4%) or the patient had a poor oral
Supervision of the retainers
The answers to the question “Who is responsible for the
regular inspections during retention period?” were
divided into three camps: 53.1% of the respondents
indicated that the orthodontists are responsible for the
regular inspections of retainers, whereas 40.7%, the
patients/their parents. The remaining respondents noted
general dentists as an option. The orthodontists
recommended three appointments during the first year for
inspection of retainers (fixed ones—by 42.0%; removable
ones—by 30.0%) and once per year after the 1-year
retention period (fixed ones—by 44.4%; removable
Instructions for patients
All orthodontists gave instructions for retainers. These
instructions included information about any detachment
and breakage of the retainers (95.1%), nutrition (66.4%),
follow-up visits (87.7%), and oral hygiene (93.8%). The
patients wearing removable retainers were given oral
(63.0%), written (32.1%), or oral/written (4.9%)
information, and the patients with fixed retainers were informed
orally (66.7%), in writing (29.6%), or in both ways (3.7%).
Oral hygiene tools such as a toothbrush, dental floss,
mouthwash, interdental brushes, and oral irrigators were
recommended by more than 50% of the respondents.
More than 90% of the respondents recommended to
inform the orthodontist in case of problems that can
arise with all types of retainers. 48.1% of the
orthodontists in total communicated with general dentists
regarding any inspection and repair of the retainers. The
orthodontists (74.1%) noted that general dentists should
refer the patients to the orthodontists if the fixed
retainer has broken or became loose.
analysis showed that two factors influencing the decision
for the retention protocol in use were associated with
the work experience in orthodontics. Younger
orthodontists with less than 10 years of experience were 3.85
more likely (95% CI 1.40–10.63) to choose “Knowledge
and skills gained in orthodontic residency” as compared
to those orthodontists with more than 10 years of
experience. The orthodontists working more than 10 years
in practice were 7.78 more likely (95% CI 2.03–29.87) to
choose a “clinical experience.” The years of work
experience appear to be a significant determinant for choosing
the retention protocol. It can be predicated that
specialists with less than 10 years of experience used a
retention protocol based on the skills learned during the
postgraduate studies while orthodontists with more than
10 years of experience used a retention protocol based
on the orthodontic work practice (p < 0.05) (Table 5).
A common retention protocol would be helpful; such
an opinion was prioritized by the orthodontists in
The necessity of common retention guidelines
The participating orthodontists were asked to identify
factors influencing the decision for the retention
protocol in use. The results of a binary logistic regression
There are currently many different types of removable
and fixed retainers, and it is unclear which retainers are
the best and how long they should be used [
Poor oral hygiene, periodontal
Occlusion (deep bite)
Incomplete treatment result
Type of treatment
study investigated the existing retention protocols used by
the orthodontists in Lithuania. A survey involving all 98
licensed Lithuanian orthodontists was conducted, and the
obtained data represented the opinions of the specialists
on the retention procedures. Nine postgraduate students
were also included in the survey, thus demonstrating that
their opinions as ones of future professionals are
significant, although the inclusion of postgraduate students
might not be that straightforward, because normally, they
use the retention protocols of the clinical instructors and
are not free to develop their own choice based on clinical
experience. The response rate of 75.7% was relatively high
compared with the surveys conducted in the other
]. It showed that this study was relevant to the
interests of the orthodontists. On the other hand, some
orthodontists noted that the questionnaire was too long
and it took a lot of time.
Previous surveys conducted in certain countries have
raised the main questions related to the selection of a
retainer and the duration for wearing a retainer. Although
the orthodontists chose different retainers for different
orthodontic situations, some trends were observed.
Surveys performed in the other European countries [
4, 5, 8,
], USA , Saudi Arabia [
], and Australia and New
] showed that fixed retainers for a lower
dental arch were dominant, except in Ireland [
], where vacuum-formed retainers were the
most popular choice. The opinions regarding an
orthodontic retention in the upper dental arch were various:
fixed retainers were most often chosen in Switzerland
] and the Netherlands [
], Hawley retainers in the
] and Saudi Arabia [
], and vacuum-formed
retainers in the UK [
], Ireland [
], and Malaysia [
combination of a fixed and removable retainer (a
vacuum-formed retainer) was the most commonly used
in Norway [
], and this was in agreement with our study;
however, the orthodontists in Lithuania gave priority to
the Hawley retainers. Lithuanian orthodontists preferred
a combination of a fixed and removable retainer in the
upper and lower arches, except after an expansion of the
maxillary dental arch or correcting any rotations of the
mandibular anterior teeth. The reason for a “double”
retention might be that the orthodontists were worried
about the relapse tendency and about the patients who
might forget to wear their removable retainer as
specified. Additionally, the findings of the study by Atack et
] showed similar results between fixed and
removable retainers and confirmed that a relapse in the lower
front teeth can occur with both types of retainers.
More than 70% of the orthodontists in Lithuania
preferred retainers to be fixed to all six anterior teeth, and
this way of fixation was dominant in upper and lower
arches. In that aspect, our results were in line with a
study conducted by Keim et al. [
], which showed that
fixed retainers bonded to all anterior teeth (3–3)
particularly in the mandibular arch which were in the
ascendant. Orthodontic canine-to-canine retainers were
considered to be effective [
] and invisible [
could ensure permanent retention and alignment of the
anterior teeth [
]. Other advantages were
mentioned by the researchers: good patient acceptance 
and low failure rate [
]. Nevertheless, fixed retainers
could cause difficulties for patients to reach areas with a
toothbrush or a dental floss, increase plaque
accumulation, and influence the periodontal health . However,
another study showed that fixed retainers allow patients
to maintain good hygiene and periodontal status [
The frequency and the duration of wearing a retainer
are still widely discussed today among orthodontists. A
Values are presented as numbers (%) by a chi-square test
*p < 0.05
Work experience (years)
≤ 10 years (n = 38)
majority of the Lithuanian orthodontists (30.9%)
considered that 1 year is the optimal time interval for the first
retention period. This view was supported by the study
conducted by Parker [
] which demonstrated that at
least 232 days of retention are needed to ensure the
regeneration of the fibers surrounding the apical, middle,
and marginal areas of the root and to provide the
stability after an orthodontic treatment. Destang and Kerr
] compared the retention time in the maxillary arch
and found that the 1-year retention showed a better
stability of the teeth position than the one of 6 months.
One year after the braces were taken off, more than 90%
of Lithuanian orthodontists left the retainers bonded in
place for an unlimited time. If the oral hygiene of a
patient was poor and it could not be improved or a dental
treatment was planned for the front teeth, the fixed
retainer was removed. Similar results were obtained in
other countries such as the Netherlands [
], UK [
], Ireland [
], USA [
], Malaysia [
Saudi Arabia [
] where orthodontists tended to leave
fixed retainers indefinitely.
The orthodontists seemed to be split in our study into
two camps with regard to the duration of wearing a
removable retainer after an orthodontic treatment, and
they recommended to wear a removable retainer for 1–
2 years or 5 years and more. Some studies showed that
the orthodontic treatment results are not stable in the
long term and even after 10 or 20 years, the stability and
good alignment of teeth are not guaranteed [
confirmed the opinion that orthodontic patients should
wear their retainers for life in order to maintain their
stable results as long as possible [
dental arches became narrower and shorter over time in
patients after an orthodontic treatment. The same
tendency was observed in untreated patients, and it showed
that this is associated with physiological processes or
dental arch maturation. Natural aging processes also
could affect the occlusion, and it could cause some
overcrowding or changes in the dental arch dimensions [
]. Anyway, a long-term retention and regular checkups
for any orthodontic patients are desirable because they
could prevent a relapse in the lower front teeth and
changes in the occlusion [
24, 25, 28
Only half of the orthodontists communicated with
general dentists regarding an inspection and repair of
the retainers, and it showed that there is no close
connection between general dentists and orthodontists. A
similar situation to that in Lithuania was observed in
], where 62% of the orthodontists
maintained a successful relationship with general dentists.
General dentists are important because they not only
choose the orthodontist according to their good
relationships with the general dentist, reputation, and other
] but they are also involved in the treatment
]. If appropriate, patients after an orthodontic
treatment return to their general dentists in order to
undertake any needed dental treatment including their oral
hygiene, extractions, restorations, or implantation. This
confirms that common retention protocol is desirable,
and teamwork plays an important role in the treatment
and the final result.
A combination of fixed and removable retainers was the
most often used in the orthodontic retention. The
Hawley appliance was a predominant removable retainer.
The bonded wire from canine to canine was the most
frequent fixed retainer. Evidence-based guidelines are
desired for a common retention protocol.
AA carried out the data collection and statistical analysis and prepared the
manuscript. AV and AA performed the literary research and interpretation
under the supervision of AS. AV took the lead role as the corresponding
author. AV and AS reviewed the manuscript and provided critical revisions.
All authors contributed to the study design. All authors read and approved
the final manuscript.
Ethics approval and consent to participate
Ethical approval for the study was obtained from the Kaunas Regional
Biomedical Research Ethics Committee (Nr. BE-2-12).
The authors declare that they have no competing interests.
Springer Nature remains neutral with regard to jurisdictional claims in
published maps and institutional affiliations.
1. Little RM , Riedel RA , Artun J. An evaluation of changes in mandibular anterior alignment from 10 to 20 years postretention . Am J Orthod Dentofac Orthop . 1988 ; 93 ( 5 ): 423 - 8 .
2. Melrose C , Millett DT . Toward a perspective on orthodontic retention? Am J Orthod Dentofac Orthop . 1998 ; 113 ( 5 ): 507 - 14 .
3. Wong PM , Freer TJ . A comprehensive survey of retention procedures in Australia and New Zealand . Aust Orthod J. 2004 ; 20 ( 2 ): 99 - 106 .
4. Renkema AM , Sips ET , Bronkhorst E , Kuijpers-Jagtman AM . A survey on orthodontic retention procedures in The Netherlands . Eur J Orthod . 2009 ; 31 ( 4 ): 432 - 7 .
5. Singh P , Grammati S , Kirschen R . Orthodontic retention patterns in the United Kingdom . J Orthod . 2009 ; 36 ( 2 ): 115 - 21 .
6. Meade MJ , Millett D. Retention protocols and use of vacuum-formed retainers among specialist orthodontists . J Orthod . 2013 ; 40 ( 4 ): 318 - 25 .
7. Pratt MC , Kluemper GT , Hartsfield JK Jr, Fardo D , Nash DA . Evaluation of retention protocols among members of the American Association of Orthodontists in the United States . Am J Orthod Dentofac Orthop . 2011 ; 140 ( 4 ): 520 - 6 .
8. Vandevska-Radunovic V , Espeland L , Stenvik A . Retention: type, duration and need for common guidelines. A survey of Norwegian orthodontists . Orthodontics (Chic) . 2013 ; 14 ( 1 ): e110 - 7 .
9. Lai CS , Grossen JM , Renkema AM , Bronkhorst E , Fudalej PS , Katsaros C. Orthodontic retention procedures in Switzerland . Swiss Dent J. 2014 ; 124 ( 6 ): 655 - 61 .
10. Ab Rahman N , Low TF , Idris NS . A survey on retention practice among orthodontists in Malaysia . Korean J Orthod . 2016 ; 46 ( 1 ): 36 - 41 .
11. Al-Jewair TS , Hamidaddin MA , Alotaibi HM , Alqahtani ND , Albarakati SF , Alkofide EA , et al. Retention practices and factors affecting retainer choice among orthodontists in Saudi Arabia . Saudi Med J. 2016 ; 37 ( 8 ): 895 - 901 .
12. Littlewood SJ , Millett DT , Doubleday B , Bearn DR , Worthington HV . Retention procedures for stabilising tooth position after treatment with orthodontic braces . Cochrane Database Syst Rev . 2016 ; doi:10.1002/ 14651858.
13. Atack N , Harradine N , Sandy JR , Ireland AJ . Which way forward? Fixed or removable lower retainers . Angle Orthod . 2007 ; 77 ( 6 ): 954 - 9 .
14. Keim RG , Gottlieb EL , Nelson AH , Vogels DS III. 2008 JCO study of orthodontic diagnosis and treatment procedures, part 1: results and trends . J Clin Orthod . 2008 ; 42 ( 11 ): 625 - 40 .
15. Artun J , Spadafora AT , Shapiro PA . A 3-year follow-up study of various types of orthodontic canine-to-canine retainers . Eur J Orthod . 1997 ; 19 ( 5 ): 501 - 9 .
16. Zachrisson BU. Clinical experience with direct-bonded orthodontic retainers . Am J Orthod . 1977 ; 71 ( 4 ): 440 - 8 .
17. Booth FA , Edelman JM , Proffit WR . Twenty-year follow-up of patients with permanently bonded mandibular canine-to-canine retainers . Am J Orthod Dentofac Orthop . 2008 ; 133 ( 1 ): 70 - 6 .
18. Naraghi S , Andrén A , Kjellberg H , Mohlin BO . Relapse tendency after orthodontic correction of upper front teeth retained with a bonded retainer . Angle Orthod . 2006 ; 76 ( 4 ): 570 - 6 .
19. Rody WJ Jr, Elmaraghy S , McNeight AM , Chamberlain CA , Antal D , Dolce C , et al. Effects of different orthodontic retention protocols on the periodontal health of mandibular incisors . Orthod Craniofac Res . 2016 ; 19 ( 4 ): 198 - 208 .
20. Parker GR . Transseptal fibers and relapse following bodily retraction of teeth: a histologic study . Am J Orthod . 1972 ; 61 ( 4 ): 331 - 44 .
21. Destang DL , Kerr WJ . Maxillary retention: is longer better? Eur J Orthod . 2003 ; 25 ( 1 ): 65 - 9 .
22. Yu Y , Sun J , Lai W , Wu T , Koshy S , Shi Z. Interventions for managing relapse of the lower front teeth after orthodontic treatment . Cochrane Database Syst Rev . 2013 ; doi:10.1002/14651858.
23. Morais JF , Freitas MR , Freitas KM , Janson G , Castello BN . Postretention stability after orthodontic closure of maxillary interincisor diastemas . J Appl Oral Sci . 2014 ; 22 ( 5 ): 409 - 15 .
24. Sadowsky C , Schneider BJ , BeGole EA , Tahir E. Long-term stability after orthodontic treatment: nonextraction with prolonged retention . Am J Orthod Dentofac Orthop . 1994 ; 106 ( 3 ): 243 - 9 .
25. Little RM . Stability and relapse of mandibular anterior alignment : University of Washington studies. Semin Orthod . 1999 ; 5 ( 3 ): 191 - 204 .
26. Thilander B . Orthodontic relapse versus natural development . Am J Orthod Dentofac Orthop . 2000 ; 117 ( 5 ): 562 - 3 .
27. Mauad BA , Silva RC , Aragón ML , Pontes LF , Silva Júnior NG , Normando D. Changes in lower dental arch dimensions and tooth alignment in young adults without orthodontic treatment . Dental Press J Orthod. 2015 ; 20 ( 3 ): 64 - 8 .
28. Nanda RS , Nanda SK . Considerations of dentofacial growth in long-term retention and stability: is active retention needed? Am J Orthod Dentofac Orthop . 1992 ; 101 ( 4 ): 297 - 302 .
29. Kothari H , Pruzansky DP , Park JH . What influences a pediatric dentist to refer to a particular orthodontist? J Clin Orthod . 2016 ; 50 ( 4 ): 231 - 8 .
30. Bibona K , Shroff B , Best AM , Lindauer SJ . Communication practices and preferences between orthodontists and general dentists . Angle Orthod . 2015 ; 85 ( 6 ): 1042 - 50 .