PLOS ONE

RESEARCH ARTICLE

Changes in the temporomandibular joint

clicking and pain disorders after orthognathic
surgery: Comparison of orthodontics-first
approach and surgery-first approach
Ying Zhai1, Jeong Joon Han ID2,3*, Seunggon Jung2, Min-Suk Kook2, Hong-Ju Park2, Hee-
Kyun Oh2
a1111111111 1 Graduate Dental School, Chonnam National University, Gwangju, Republic of Korea, 2 Department of Oral
a1111111111 and Maxillofacial Surgery, School of Dentistry, Dental Science Research Institute, Chonnam National
a1111111111 University, Gwangju, Republic of Korea, 3 Hard-tissue Biointerface Research Center, School of Dentistry,
a1111111111 Chonnam National University, Gwangju, Republic of Korea
a1111111111
* ooops01@snu.ac.kr

Abstract
OPEN ACCESS
The purposes of this study were to investigate the influence of the orthodontics-first
Citation: Zhai Y, Han JJ, Jung S, Kook M-S, Park
H-J, Oh H-K (2020) Changes in the approach (OFA) and surgery-first approach (SFA) on changes in the signs and symptoms of
temporomandibular joint clicking and pain temporomandibular joint disorders (TMDs) and to compare pre- and postoperative ortho-
disorders after orthognathic surgery: Comparison dontic treatment duration and total treatment duration between the two approaches. This
of orthodontics-first approach and surgery-first
retrospective study recruited 182 adult patients with malocclusions treated with OFA and
approach. PLoS ONE 15(9): e0238494. https://doi.
org/10.1371/journal.pone.0238494 SFA and recorded variables such as age, gender, skeletal classification, and signs and
symptoms of TMD (clicking and pain disorders) before the start of the surgical-orthodontic
Editor: Essam Al-Moraissi, Thamar University,
Faculty of Dentistry, YEMEN treatment and after surgery. Changes in the signs and symptoms of TMD and treatment
duration were evaluated within each approach and compared between two approaches. A
Received: June 8, 2020
binary logistic regression was performed to assess the influence of the variables on the post-
Accepted: August 18, 2020
operative signs and symptoms of TMD. There were no significant postoperative changes in
Published: September 4, 2020 temporomandibular joint (TMJ) pain for OFA and SFA, whereas a significant reduction was
Copyright: © 2020 Zhai et al. This is an open found in TMJ clicking after surgery for both approaches. According to binary logistic regres-
access article distributed under the terms of the sion, the type of surgical-orthodontic treatment (OFA or SFA) was not a significant risk factor
Creative Commons Attribution License, which
for postoperative TMJ clicking and pain, and the risk of postoperative TMJ clicking and pain
permits unrestricted use, distribution, and
reproduction in any medium, provided the original was significant only when TMJ clicking (OR = 10.774, p < 0.001) and pain (OR = 26.876, p =
author and source are credited. 0.008) existed before the start of the entire treatment, respectively. With regard to the treat-
Data Availability Statement: All relevant data are ment duration, SFA (21.1 ± 10.3 months) exhibited significantly shorter total treatment dura-
within the manuscript. tion than OFA (34.4 ± 11.9 months) (p < 0.001). The results of this study suggest that
Funding: This study was supported by a grant surgical-orthodontic treatment using SFA can be a feasible option of treatment for dentofa-
(BCRI20042) of Chonnam National University cial deformities based on the equivalent effect on TMD and shorter overall treatment period
Hospital Biomedical Research Institute and the compared to conventional surgical-orthodontic treatment using OFA.
National Research Foundation of Korea (NRF) grant
funded by the Korea government (MSIT) (No.
2020R1C1C1014734) to JJH.

Competing interests: The authors have declared

that no competing interests exist.

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PLOS ONE Changes in the temporomandibular joint clicking and pain disorders after orthognathic surgery

Introduction
Temporomandibular disorders (TMDs) are a series of clinical problems that affect the tempo-
romandibular joint (TMJ), masticatory musculatures, the surrounding bony and soft tissue
structures, or multiple combinations of these. Common signs and symptoms of TMD include
TMJ sounds and pain during mandibular function, headache, facial and neck pain, and limita-
tion in the range of mandibular movements. The etiology of TMD is generally known as com-
plicated and multifactorial [1]. Based on the relevant literature, neuromuscular factors,
mechanical and structural factors, and psychosocial factors have been suggested as a source of
TMD [2–4]. Several reviews indicate various occlusal factors contribute to development of
TMD signs and symptoms, and reported that prevalence of TMD symptoms in patients with
dentofacial deformities is higher than that in the general population [3–5].
Surgical-orthodontic treatment is a common treatment protocol for patients with dentofa-
cial deformities, and orthognathic surgery is performed to reposition the maxilla and/or man-
dible to a more balanced position. Through orthognathic surgery, dental and skeletal harmony
can be achieved, and patients can obtain improvement in masticatory function and esthetics
[3, 6, 7]. In the TMJ, the positional changes of the mandibular condyle, which is one of the
main anatomical structures of the TMJ, usually occur and the relationship between the condyle
and surrounding musculature may change after orthognathic surgery [8]. However, there is
still not good agreement about whether surgical-orthodontic treatment will improve or aggra-
vate the signs and symptoms of TMD, or have no significant effect on them. Several previous
studies have found a beneficial association between orthognathic surgery and TMD with the
reduction of the prevalence of postoperative TMD symptomatic patients [9–13]. On the con-
trary, some studies reported that the positional changes of the condyle in the glenoid fossa dur-
ing orthognathic surgery may cause TMD symptoms, even causing further deleterious effects
on the TMJ and thus worsening pre-existing symptoms and dysfunction [14, 15].
In recent decades, most surgical-orthodontic treatments were performed using the orthodon-
tics-first approach (OFA), which consists of preoperative orthodontics, orthognathic surgery, and
postoperative orthodontics. Recently, however, the application of the surgery-first approach
(SFA), with no or minimal preoperative orthodontics, has increased due to several advantages. In
SFA, the jaw bone is repositioned to a more balanced and ideal position relying on the advanced
three-dimensional plan through the surgery at the initial stage of treatment. Current literature
have reported on the shorter treatment duration [7, 16–18], earlier esthetic improvement [19],
more favorable quality of life [20, 21], similar stability [22–24], and equivalent changes of condylar
position in SFA [25]. However, considering the complexity of the diagnosis and treatment plan-
ning, and lack of initial occlusal adjustment during the preoperative orthodontic treatment in
SFA, a possible limitation of this approach may be associated with a higher risk of postoperative
complications, such as new onset or deterioration of TMD signs and symptoms. In contrast to
OFA, which has been extensively investigated for the effect on TMD [9, 10, 14, 26–28], few previ-
ous reports have examined the signs and symptoms of TMD in SFA.
Therefore, the aims of the present study were to investigate the influence of OFA and SFA
on signs and symptoms of TMD, and to compare pre- and postoperative orthodontic treat-
ment duration and total treatment duration between the two approaches. It was hypothesized
that: (1) there is a difference between the prevalence of TMD signs and symptoms in OFA and
SFA groups; (2) SFA can shorten total treatment duration significantly, compared to OFA.

Materials and methods

The authors designed and implemented a retrospective cohort study. The study population
was composed of all consecutive patients who received surgical-orthodontic treatment from

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PLOS ONE Changes in the temporomandibular joint clicking and pain disorders after orthognathic surgery

January 2009 to December 2016 at the Department of Oral and Maxillofacial Surgery in Chon-
nam National University Dental Hospital (CNUDH). All of the patients underwent orthog-
nathic surgery with OFA or SFA. Exclusion criteria were patients with syndromes or
craniofacial deformities, such as cleft lip and palate, previous history of orthognathic surgery,
the place of orthodontic treatment performed other than the same institution (Department of
Orthodontics, CNUDH), and no complete orthodontic treatment durations record. The
patients with minimum preoperative orthodontic treatment, which could be included in the
SFA in a broad sense, were also excluded. The SFA group included only patients who received
no preoperative orthodontic treatment. Due to the retrospective nature of the study and de-
identifying the records of patients before the start of the study, it was exempted from approval
of the institutional review board of the Chonnam National University Dental Hospital
(CNUDH-EXP-2020-019).
To determine which approach to proceed with surgical-orthodontic treatment, the patient’s
preferences were first reflected after explaining both OFA and SFA to the patient. When the
patient preferred SFA, postoperative orthodontic treatment including dental alignment, inci-
sor decompensation, and arch coordination was predicted and simulated using laboratory pro-
cedure and model surgery, and the construction of surgical occlusion was performed. After
this diagnosis process, the following criteria were considered to determine whether SFA could
be applied or not: 1) good predictability, 2) three or more occlusal stop between the upper and
lower arches, 3) mild to moderate curve of Spee or vertical problem, 4) no or mild transverse
discrepancy [29].
Regarding surgical procedures, the correction of the maxilla was performed using conven-
tional Le Fort I osteotomy or a two- or three-piece maxillary osteotomy for all patients requir-
ing bimaxillary surgery. For the mandibular surgery, the bilateral sagittal split ramus
osteotomy or unilateral sagittal split ramus osteotomy was performed. After splitting of the
mandible into the proximal and distal segments, bony interferences between the mandibular
segments were removed. The condyle was manually guided to the superior and anterior posi-
tion within the glenoid fossa, which was regarded as the same condylar position when the cen-
tric relation was captured in the preoperative preparation. Then, fixation of the mandibular
segments was performed. Postoperative maxillomandibular fixation was accomplished with a
surgical splint for 2 or 3 weeks, and mouth-opening exercises were started after 3 weeks of sur-
gery to gain adequate mouth-opening ability greater than 40 mm. All subjects received postop-
erative orthodontic treatment with or without preoperative orthodontic treatment in one
center (Department of Orthodontics, CNUDH), following the complete treatment plan.
The data of subjects were summarized according to the age at time of surgery, gender, skele-
tal classifications, and signs and symptoms of TMD. Skeletal classifications dividing the sub-
jects into three groups (class I, II and III) were analyzed using lateral cephalograms. The
clinical examination of TMJs consisted of the evaluation of TMJ clicking and pain disorders,
including arthralgia and muscular disorders (myalgia), and it was performed before starting
surgical-orthodontic treatment, after preoperative orthodontic treatment (for the OFA group),
and more than 6 months after surgery. TMJ clicking, that was reported by a patient, was con-
firmed by an examiner from the palpation of the TMJ during the opening and closing of the
mouth. Arthralgia was confirmed when the patients reported pain in TMJ in combination of
familiar pain with TMJ palpation or range of motion. Myalgia diagnosis was confirmed when
the patients reported pain in the masticatory muscles in combination with familiar pain in the
masticatory muscles with either muscle palpation or maximum opening. With regard to the
signs and symptoms of TMD, the patients were divided into four groups according to assess-
ment of changes in signs and symptoms: (1) pre o ! post x: patients with pre-treatment symp-
toms and whose symptoms disappeared after surgery; (2) pre o ! post o; patients with

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PLOS ONE Changes in the temporomandibular joint clicking and pain disorders after orthognathic surgery

positive symptoms before the start of the treatment and after surgery; (3) pre x ! post o:
asymptomatic patients developing symptoms after surgery; and (4) pre x ! post x: asymptom-
atic patients before the start of the treatment and after surgery. The treatment duration was
recorded as the preoperative orthodontic treatment duration and the postoperative orthodon-
tic treatment duration.
The data were analyzed using SPSS statistics 25.0 for Windows (SPSS IBM, New York,
USA). To compare the differences in demographic and clinical characteristics between OFA
and SFA groups, the Chi-square test or independent t test was performed. The agreement
between pre-treatment and postoperative TMD symptoms in each approach was determined
with the McNemar test. The difference in prevalence of TMD signs and symptoms between
OFA and SFA groups was analyzed using the Chi-square test. Changes in the TMD signs and
symptoms depending on the variables of patients were presented using the descriptive statis-
tics. To determine the influencing factors for postoperative TMD signs and symptoms, a
binary logistic regression analysis was performed for variables including age, gender, skeletal
classification, pre-treatment TMD signs and symptoms, and type of surgical-orthodontic treat-
ment approach (SFA or OFA). For the treatment durations, pre- and post-operative orthodon-
tic treatment duration and total treatment durations were presented by the mean with
standard deviation, median, minimum, and maximum values, and compared between OFA
and SFA groups using an independent t test. The correlations of treatment durations were
evaluated using Pearson’s correlation analysis. To evaluate treatment duration among three
skeletal classifications, one-way analysis of variance was performed for each group. The signifi-
cance level was set at p < 0.05.

Results
Demographic and clinical characteristics of all the patients in OFA and
SFA groups
A total of 182 patients (100 males and 82 females; mean age, 22.5 ± 3.8 years; age range, 17–40
years) who met inclusion and exclusion criteria were recruited for the study. Demographics
and clinical characteristics of the study sample are summarized in Table 1. Of the 182 patients
who received surgical orthodontic treatment, 116 patients with OFA consisted of 62 males

Table 1. Demographic and clinical characteristics of study sample.

OFA (n = 116) SFA (n = 66) p value
Gender, n (%) 0.591�
male 62 (53.4) 38 (57.6)
female 54 (46.6) 28 (42.4)
Age (year), mean ± SD 23.3 ± 3.8 21.3 ± 3.3 0.001†
age distribution, n (%) 0.015�
<21 years 29 (25.0) 28 (42.4)
�21years 87 (75.0) 38 (57.6)
Skeletal classification, n (%) 0.087�
class I 13 (11.2) 5 (7.6)
class II 16 (13.8) 3 (4.5)
class III 87 (75.0) 58 (87.9)

Abbreviation: OFA, orthodontics-first approach; SFA, surgery-first approach; SD, standard deviation.
�
By Chi-square test
† By independent t test.

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PLOS ONE Changes in the temporomandibular joint clicking and pain disorders after orthognathic surgery

Table 2. Changes of TMJ clicking according to the approaches in surgical-orthodontic treatment.

Subject After preoperative orthodontic treatment Postoperatively
No clicking Clicking p value� No clicking Clicking p value�
OFA 0.143 < 0.001
Without pre-treatment clicking (n = 78) 73 (93.6%) 5 (6.4%) 74 (94.9%) 4 (5.1%)
With pre-treatment clicking (n = 38) 12 (31.6%) 26 (68.4%) 28 (73.7%) 10 (26.3%)
SFA 0.004
Without pre-treatment clicking (n = 55) 55 (100.0%) 0 (0.0%)
With pre-treatment clicking (n = 11) 9 (81.8%) 2 (18.2%)

Abbreviation: TMJ, temporomandibular joint; OFA, orthodontics-first approach; SFA, surgery-first approach.
�
By McNemar test.

https://doi.org/10.1371/journal.pone.0238494.t002

(53.4%) and 54 females (46.6%), and 66 with SFA included 38 males (57.6%) and 28 females
(42.4%) (p = 0.591). There was significant difference in mean age between the two groups
(OFA group, 23.3 ± 3.8 years; SFA group, 21.3 ± 3.3 years) (p = 0.001). The proportion
between young patients (age <21 years) and older patients (age �21 years) also exhibited a sta-
tistically significant difference (p = 0.015). 87 patients (75.0%) of 125 elderly patients received
surgical-orthodontic treatment using OFA, whereas SFA was more used for young patients
(n = 28, 42.4%). Regarding the variables of skeletal classifications, there were no significant dif-
ferences in the percentages of patients between OFA and SFA groups (p = 0.087). Of the 116
patients in the OFA group and 66 patients in the SFA group, the patients with skeletal class III
accounted for 75.0% (n = 87) in the OFA group and 87.9% (n = 58) in the SFA group.

TMD evaluation
Compared to the pre-treatment TMJ clicking, the both OFA and SFA groups exhibited a sig-
nificant reduction in TMJ clicking after surgery (OFA, p < 0.001; SFA, p = 0.004) (Table 2). Of
the 38 patients with pre-treatment clicking in OFA group, 28 patients (73.7%) exhibited
improvement in the clicking after surgery. On the other hand, 4 of 78 patients (5.1%) without
pre-treatment TMJ clicking in the OFA group developed clicking postoperatively. In the SFA
group, the clicking disappeared postoperatively in 9 of 11 patients (81.8%) with pre-treatment
TMJ clicking, and none of those who did not have it preoperatively had developed it by the fol-
low-up over 6 months. With regard to the TMJ pain, there was no statistically significant
changes for both OFA and SFA groups (OFA, p = 0.999; SFA, p = 0.125) (Table 3). Before the
surgical-orthodontic treatment, 5 patients in OFA group (arthralgia, 2 patients; myalgia, 2

Table 3. Changes of TMJ pain disorders according to the approaches in surgical-orthodontic treatment.
Subject After preoperative orthodontic treatment Postoperatively
No pain Pain p value� No pain Pain p value�
OFA 0.999 0.999
Without pre-treatment pain (n = 111) 110 (99.1%) 1 (0.9%) 108 (97.3%) 3 (2.7%)
With pre-treatment pain (n = 5) 2 (40.0%) 3 (60.0%) 4 (80.0%) 1 (20.0%)
SFA 0.125
Without pre-treatment pain (n = 61) 61 (100.0%) 0 (0.0%)
With pre-treatment pain (n = 5) 4 (80.0%) 1 (20.0%)

Abbreviation: TMJ, temporomandibular joint; OFA, orthodontics-first approach; SFA, surgery-first approach.
�
By McNemar test.

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PLOS ONE Changes in the temporomandibular joint clicking and pain disorders after orthognathic surgery

patients; both arthralgia and myalgia, 1 patient) and 5 patients in SFA group (arthralgia, 4
patients; both arthralgia and myalgia, 1 patients) exhibited pain disorders. Among the patients
with pre-treatment TMJ pain disorders, 4 patients (80.0%; arthralgia, 1 patient; myalgia, 2
patients; both arthralgia and myalgia, 1 patient) in the OFA group and 4 patients (80.0%;
arthralgia, 3 patients; both arthralgia and myalgia, 1 patient) in the SFA group had an improve-
ment of TMJ pain 6 months after surgery. 3 of 111 patients (2.7%) without pre-treatment TMJ
pain in OFA group exhibited postoperative TMJ pain (arthralgia, 2 patients; myalgia, 1
patient), while there were no patients in the SFA group who exhibited newly developed TMJ
pain after surgery. In the comparison of pre-treatment and postoperative prevalence of TMJ
symptoms between OFA and SFA groups, the SFA group showed significantly lower pre-treat-
ment (p = 0.019) and postoperative prevalence of TMJ clicking (p = 0.038) than the OFA
group (Table 4). With respect to the prevalence of TMJ pain, there were no significant differ-
ences between two groups (pre-treatment, p = 0.353; postoperative, p = 0.443). The changes in
prevalence of TMJ symptoms depending on various variables (gender, age, and skeletal classifi-
cation) are shown in Tables 5 and 6. According to binary logistic regression, the risk of postop-
erative TMJ clicking and pain was significant only when TMJ clicking (OR = 10.774,
p < 0.001) and pain (OR = 26.876, p = 0.008) existed before treatment, respectively (Table 7).
For OFA group, we evaluated the changes of TMJ clicking and pain disorders during the
preoperative orthodontic treatment. Among the 38 patients with pre-treatment clicking, TMJ
clicking disappeared in 12 patients (31.6%), although 26 patients (68.4%) still exhibited TMJ
clicking after preoperative orthodontic treatment. In addition, 5 patients who had no TMJ
clicking before the start of the treatment also showed a newly developed TMJ clicking after
preoperative orthodontic treatment. However, there were no statistically significant changes in
TMJ clicking and pain disorders during the preoperative orthodontic treatment period (TMJ
clicking, p = 0.143; pain disorders, p = 0.999).

Total treatment duration

The analysis of treatment durations in OFA and SFA groups are shown in Table 8. The mean
preoperative orthodontic duration in the OFA group was 22.4 ± 10.6 months. The total treat-
ment duration of OFA and SFA groups was 34.4 ± 11.9 months and 21.1 ± 10.3 months,
respectively. Though postoperative orthodontic treatment duration was significantly longer in
the SFA group (21.1 ± 10.3 months) than in the OFA group (12.0 ± 7.4 months) (p < 0.001),
the SFA group exhibited significantly shorter total treatment duration than the OFA group
(p < 0.001).
In the correlation analysis between pre- or postoperative orthodontic treatment duration
and total treatment duration, the positive correlation between preoperative and total treatment
durations in OFA group was stronger (r = 0.712, p < 0.001), comparing the correlation
between postoperative and total treatment durations (r = 0.438, p < 0.001). Table 9 represents

Table 4. Comparison of pre-treatment and postoperative prevalence of TMJ symptoms between orthodontics-
first approach and surgery-first approach groups.
Comparison between two groups (p value� )
Pre-treatment 6-month postoperatively
TMJ clicking 0.019 0.038
Pain disorders 0.353 0.443

Abbreviation: TMJ, temporomandibular joint.

�
By Chi-square test.

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PLOS ONE Changes in the temporomandibular joint clicking and pain disorders after orthognathic surgery

Table 5. Changes in TMJ clicking before the start of the surgical-orthodontic treatment and after surgery.
OFA (n = 116) SFA (n = 66)
pre o ! post x pre o ! post o pre x ! post o pre x ! post x pre o ! post x pre o ! post o pre x ! post o pre x ! post x
Gender
male n 14 7 0 41 7 0 0 31
% 12.1% 6.0% 0.0% 35.3% 10.6% 0.0% 0.0% 47.0%
female n 14 3 4 33 2 2 0 24
% 12.1% 2.6% 3.4% 28.4% 3.0% 3.0% 0.0% 36.4%
Age
<21years n 7 2 2 18 2 1 0 25
% 6.0% 1.7% 1.7% 15.5% 3.0% 1.5% 0.0% 37.9%
�21years n 21 8 2 56 7 1 0 30
% 18.1% 6.9% 1.7% 48.3% 10.6% 1.5% 0.0% 45.5%
Skeletal classification
class I n 4 0 2 7 2 0 0 3
% 3.4% 0.0% 1.7% 6.0% 3.0% 0.0% 0.0% 4.5%
class II n 4 2 1 9 0 0 0 3
% 3.4% 1.7% 0.9% 7.8% 0.0% 0.0% 0.0% 4.5%
class III n 20 8 1 58 7 2 0 49
% 17.2% 6.9% 0.9% 50.0% 10.6% 3.0% 0.0% 74.2%

Abbreviation: TMJ, temporomandibular joint; OFA, orthodontics-first approach; SFA, surgery-first approach; pre o ! post x, patients with pre-treatment symptoms
and whose symptoms disappeared after surgery; pre o ! post o, patients with the positive symptoms before the start of the treatment and after surgery; pre x ! post o,
asymptomatic patients developing symptoms after surgery; pre x ! post x: asymptomatic patients before the start of the treatment and after surgery.

https://doi.org/10.1371/journal.pone.0238494.t005

Table 6. Changes in TMJ pain disorders before the start of the surgical-orthodontic treatment and after surgery.
OFA group (n = 116) SFA group (n = 66)
pre o ! post x pre o ! post o pre x ! post o pre x ! post x pre o ! post x pre o ! post o pre x ! post o pre x ! post x
Gender
male n 1 1 2 58 2 1 0 35
% 0.9% 0.9% 1.7% 50.0% 3.0% 1.5% 0.0% 53.0%
female n 3 0 0 51 2 0 0 26
% 2.6% 0.0% 0.0% 44.0% 3.0% 0.0% 0.0% 39.4%
Age
<21years n 2 1 0 26 1 1 0 26
% 1.7% 0.9% 0.0% 22.4% 1.5% 1.5% 0.0% 39.4%
�21years n 2 0 2 83 3 0 0 35
% 1.7% 0.0% 1.7% 71.6% 4.5% 0.0% 0.0% 53.0%
Skeletal classification
class I n 1 0 1 11 1 0 0 4
% 0.9% 0.0% 0.9% 9.5% 1.5% 0.0% 0.0% 6.1%
class II n 0 0 1 15 0 0 0 3
% 0.0% 0.0% 0.9% 12.9% 0.0% 0.0% 0.0% 4.5%
class III n 3 1 1 82 3 1 0 54
% 2.6% 0.9% 0.9% 70.7% 4.5 1.5% 0.0% 81.8%

Abbreviation: TMJ, temporomandibular joint; OFA, orthodontics-first approach; SFA, surgery-first approach; pre o ! post x, patients with pre-treatment symptoms
and whose symptoms disappeared after surgery; pre o ! post o, patients with the positive symptoms before the start of the treatment and after surgery; pre x ! post o,
asymptomatic patients developing symptoms after surgery; pre x ! post x: asymptomatic patients before the start of the treatment and after surgery.

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PLOS ONE Changes in the temporomandibular joint clicking and pain disorders after orthognathic surgery

Table 7. Results of the logistic regression analysis to determine significant variables affecting postoperative TMJ clicking and pain.
Postoperative TMJ clicking Postoperative TMJ pain
OR (95% CI of OR) p value OR (95% CI of OR) p value
Age 0.959 (0.830–1.107) 0.566 0.865 (0.593–1.261) 0.451
Gender 0.508 (0.162–1.590) 0.245 7.108 (0.543–93.089) 0.135
Skeletal classification
class I (reference) 1 0.875 1 0.441
class II 1.258 (0.149–10.637) 0.833 1.344 (0.061–29.526) 0.851
class III 0.837 (0.144–4.867) 0.843 0.287 (0.022–3.838) 0.347
Pre-treatment clicking 10.774 (3.064–37.882) < 0.001 1.434 (0.181–11.346) 0.733
Pre-treatment pain 0 0.999 26.876 (2.397–301.324) 0.008
Treatment approach (OFA or SFA) 2.955 (0.568–15.371) 0.198 3.393 (0.289–39.786) 0.331

TMJ, temporomandibular joint; OR, odds ratio; CI: confidence interval; OFA, orthodontics-first approach; SFA, surgery-first approach.

https://doi.org/10.1371/journal.pone.0238494.t007

the treatment duration with OFA and SFA to evaluate the skeletal classifications as an inde-
pendent variable. Skeletal classifications had no significant influence on the preoperative, post-
operative, and total treatment duration in OFA group. However, in SFA group, there were
significant differences in total treatment duration among three skeletal classifications (p =
0.028; class I vs class II, p = 0.128; class II vs class III, p = 0.024; class III vs class I, p = 0.999),
where the average duration of total treatment in SFA groups was 21.4 ± 13.7 months for class
I, 36.3 ± 5.0 months for class II, and 20.3 ± 9.7 months for class III patients.

Discussion
To our knowledge, this is the first study to evaluate the changes of TMD signs and symptoms
in patients with dentofacial deformities who were treated by OFA and SFA. The prevalence of
diagnostic TMJ clicking in OFA and SFA groups decreased after surgical-orthodontic treat-
ment. According to results of logistic regression, the type of surgical-orthodontic treatment
(OFA or SFA) was not a significant risk factor for postoperative TMJ clicking and pain. Total
treatment duration in the SFA group was significantly shorter than that in the OFA group.
Thus, the first hypothesis would be rejected, but the second confirmed.
In our study, the prevalence of pre-treatment TMJ clicking in patients with dentofacial
deformities was 32.8% in the OFA group and 16.7% in the SFA group, and the prevalence of
pre-treatment TMJ pain was 4.3% in the OFA group and 7.6% in the SFA group. In OFA
group, the prevalence of preoperative TMJ symptoms after preoperative orthodontic treatment
was 26.7% for TMJ clicking and 3.4% for pain disorders. However, the prevalence of TMD can

Table 8. Comparison of treatment durations between orthodontics-first approach and surgery-first approach groups.
OFA group SFA group
Mean ± SD Med Min Max Mean ± SD Med Min Max p value�
Preop-OTD 22.4 ± 10.6 20.0 6.0 71.0 0.0 0.0 0.0 0.0 < 0.001
Postop-OTD 12.0 ± 7.4 10.0 4.0 45.0 21.1 ± 10.3 18.0 8.0 51.0 < 0.001
Total-TD 34.4 ± 11.9 32.0 17.0 75.0 21.1 ± 10.3 18.0 8.0 51.0 < 0.001

Data are presented in months.

Abbreviation: OFA, orthodontics-first approach; SFA, surgery-first approach; SD, standard deviation; Med, median value; Min, minimum value; Max, maximum value;
Preop-OTD, preoperative orthodontic treatment duration; Postop-OTD, postoperative orthodontic treatment duration; Total-TD, total treatment duration.
�
By independent t test.

https://doi.org/10.1371/journal.pone.0238494.t008

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PLOS ONE Changes in the temporomandibular joint clicking and pain disorders after orthognathic surgery

Table 9. Comparison of treatment durations among skeletal classifications in orthodontics-first approach and surgery-first approach groups.
OFA group SFA group
class I class II class III p value� class I class II class III p value�
Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD
Preop-OTD 20.9 5.3 22.6 9.6 22.5 11.4 0.873 0.0 0.0 0.0 0.0 0.0 0.0 -
Postop-OTD 9.3 5.2 10.9 5.1 12.6 7.9 0.271 21.4 13.7 36.3 5.0 20.3 9.7 0.028
Total-TD 30.2 7.6 33.6 9.4 35.1 12.8 0.374 21.4 13.7 36.3 5.0 20.3 9.7 0.028

Data are presented in months.

Abbreviation: OFA, orthodontics-first approach; SFA, surgery-first approach; SD, standard deviation; Preop-OTD, preoperative orthodontic treatment duration;
Postop-OTD, postoperative orthodontic treatment duration; Total-TD, total treatment duration.
�
By one-way analysis of variance.

https://doi.org/10.1371/journal.pone.0238494.t009

be affected by race, age, and investigation methods, and a systematic review of Al-Riyami,
Cunningham [30] showed that the pre-existing signs and symptoms of TMD in patients who
had undergone orthognathic surgery ranged from 5% to 86%. Regarding the factors that pre-
dispose TMD symptoms, several authors have reported that female patients with a class II
facial profile seem to be an increased risk for preoperative TMD symptoms. However, in the
present study, there were no statistical differences in the prevalence of preoperative TMJ symp-
toms between male and female patients for both OFA and SFA groups. With respect to the
effect of skeletal classification on preoperative TMD symptoms, it was difficult to draw a gen-
eral conclusion due to the relatively small number of patients of class II facial profile in this
study. In Asian countries, most patients undergoing surgical-orthodontic treatment have a
skeletal class III facial profile, and, in our study, 87 of 116 patients of the OFA group and 58 of
66 patients of the SFA group had a class III facial profile, while only 16 patients of the OFA
group and three patients of the SFA group had a class II facial profile preoperatively.
Although there have been previous reports of the effect of orthognathic surgery on TMD,
the effect of orthognathic surgery on the signs and symptoms of TMD is still controversial [13,
14, 27, 28, 31]. Westermark, Shayeghi [13] reported that the prevalence of TMD symptoms
decreased from 43% to 28% after surgery, although the overall positive effect on TMD was less
effective in patients with mandibular retrognathism. Abrahamsson, Henrikson [26] also
reported a positive effect in respect of TMD pain in patients who received surgical-orthodontic
treatment for correction of dentofacial deformity. In a study using clinical and magnetic reso-
nance imaging findings [32], the disc position was improved by accurate repositioning of the
condylar-disc complex after surgical-orthodontic treatment in class II patients. In contrast, in
the study by Wolford, Reiche-Fischel [14], no TMJ pain relief was observed after surgery in
patients with preoperative pain, and, furthermore, six patients experienced postoperative con-
dylar resorption. They concluded that patients with preexisting TMJ dysfunction are more
likely to have worsening of the TMJ dysfunction after orthognathic surgery, especially after
mandibular advancement. For SFA, there was only one previous report that studied the effect
of SFA on the TMJ [12]. Pelo, Saponaro [12] assessed TMD signs and symptoms in 24 patients
who were treated with SFA, and reported a significant improvement or resolution of the TMD
signs and symptoms postoperatively in the majority of patients with preoperative TMD. In our
study, we assessed the changes in signs and symptoms of TMD after surgical-orthodontic
treatment and compared them between OFA and SFA. Although, there was no statistically sig-
nificant improvement in the prevalence of TMJ pain, 4 of 5 patients with pre-treatment pain
in the OFA group and 4 of 5 patients with pre-treatment pain in the SFA group exhibited relief
of TMJ pain after surgery. With respect to TMJ clicking, the prevalence of TMJ clicking

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PLOS ONE Changes in the temporomandibular joint clicking and pain disorders after orthognathic surgery

reduced significantly from 32.8% (38 of 116) before the beginning of the treatment to 12.1%
(14 of 116) after surgery in the OFA group, and from 16.7% (11 of 66) to 3.0% (2 of 66) in the
SFA group. Clicking disappeared in 73.2% (28 of 38) of pre-treatment symptomatic patients in
the OFA group and in 81.82% (9 of 11) in the SFA group.
Despite the positive effect of orthognathic surgery on TMD, several investigators have sug-
gested that postoperative TMJ dysfunction may develop after surgery in patients with no pre-
operative TMD signs and symptoms [10, 28, 33]. In a study by Karabouta and Martis [33],
3.7% of patients with no TMJ dysfunction preoperatively presented postoperative TMJ dys-
function. Togashi, Kobayashi [28] reported that TMJ signs and symptoms developed in 9.7%
of preoperative asymptomatic patients. In our study, 3 of 111 patients (2.7%) with no pre-treat-
ment TMJ pain in the OFA group and none of the patients in the SFA group exhibited postop-
erative development of TMJ pain. Postoperative clicking developed in 4 of 78 (5.1%) of
patients with no pre-treatment clicking in the OFA group, and none in the SFA group. Regard-
ing the predictive factors for postoperative TMD signs and symptoms, pre-existing TMJ click-
ing and pain were detected as significant factors for postoperative symptoms. Our results are
consistent with other previous studies [10, 34]. In a study in which postoperative TMD was
assessed in patients with class III malocclusion by Scolozzi, Wandeler [34], anamnestic TMJ
clicking and bimaxillary surgery were suggested as clinical predictive factors predisposing to
the envelopment or worsening of clinical dysfunction in TMDs. Kretschmer, Baciut [10] also
reported that preoperative clicking and preoperative crepitus were significant factors for post-
operative symptoms.
The present findings indicate that the average total treatment time with OFA is 34.4
months, which is possibly longer than indicated by results of previous studies, which vary
from 21.9 months as found by Jacobson [35] to 32.8 months reported by O’Brien, Wright [36].
This could be influenced by a greater number of appointments or slightly longer appointment
interval schedule. No clinically significant association between preoperative and postoperative
treatment duration was found, so there was no evidence to suggest that the period of preopera-
tive orthodontic treatment is associated with a decreased or increased postoperative orthodon-
tic treatment time. In the comparison between OFA and SFA, total treatment duration in SFA
was significantly shorter than that in OFA, which might be due to the reduction or elimination
of pre-surgical orthodontic treatment time [37]. Furthermore, the increase in osteoclastic
activities and metabolic changes (regional acceleratory phenomenon) after orthognathic sur-
gery might accelerate orthodontic tooth movement [17]. In a biological evaluation after
orthognathic surgery using SFA, Zingler, Hakim [38] reported that the concentration of
remodeling factors in the crevicular fluid increased at later postoperative time points and sug-
gested that accelerated orthodontic tooth movement might be related to elevated levels of
these factors.
This study has several limitations. First, the total number of patients is not sufficient to
draw generalized strong conclusions. Thus, future studies including greater number of patients
are needed. In addition, more long-term evaluation is necessary because TMD may develop
even after the entire surgical-orthodontic treatment, including postoperative orthodontic
treatment. Another limitation of this study is the difference in the age of patients between
OFA and SFA groups. This is probably because most of the patients who start the surgical-
orthodontic treatment after graduating from high school prefer SFA to receive orthognathic
surgery before starting social life or entering college. The age difference between two groups
could have contributed to the signs and symptoms of TMJ. Although magnetic resonance
imaging (MRI) analysis of patients with TMD was not performed in this study, the evaluation
of disc position using MRI may provide a better understanding of the effect of orthognathic
surgery on TMJ.

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PLOS ONE Changes in the temporomandibular joint clicking and pain disorders after orthognathic surgery

Conclusions
The type of surgical-orthodontic treatment (OFA or SFA) was not a significant risk factor for
postoperative TMJ clicking and pain after orthognathic surgery. Total treatment duration in
the SFA group was significantly shorter than that in the OFA group. The results of this study
suggest that surgical-orthodontic treatment using SFA can be a feasible option for treatment of
dentofacial deformities based on the equivalent effect on TMD and shorter overall treatment
period compared to conventional surgical-orthodontic treatment using OFA.

Author Contributions
Conceptualization: Jeong Joon Han.
Data curation: Ying Zhai, Jeong Joon Han.
Formal analysis: Ying Zhai, Jeong Joon Han.
Investigation: Ying Zhai, Jeong Joon Han, Seunggon Jung, Min-Suk Kook, Hong-Ju Park,
Hee-Kyun Oh.
Writing – original draft: Ying Zhai.
Writing – review & editing: Jeong Joon Han, Hee-Kyun Oh.

References
1. Durham J, Newton-John TR, Zakrzewska JM. Temporomandibular disorders. BMJ. 2015; 350:h1154.
https://doi.org/10.1136/bmj.h1154 PMID: 25767130
2. Chisnoiu AM, Picos AM, Popa S, Chisnoiu PD, Lascu L, Picos A, et al. Factors involved in the etiology
of temporomandibular disorders—a literature review. Clujul medical. 2015; 88:473–8. https://doi.org/10.
15386/cjmed-485 PMID: 26732121
3. Magnusson T, Ahlborg G, Finne K, Nethander G, Svartz K. Changes in temporomandibular joint pain-
dysfunction after surgical correction of dentofacial anomalies. International journal of oral and maxillofa-
cial surgery. 1986; 15(6):707–14. https://doi.org/10.1016/s0300-9785(86)80111-9 PMID: 3100672
4. Al-Moraissi EA, Perez D, Ellis E 3rd. Do patients with malocclusion have a higher prevalence of tempo-
romandibular disorders than controls both before and after orthognathic surgery? A systematic review
and meta-analysis. Journal of cranio-maxillo-facial surgery: official publication of the European Associa-
tion for Cranio-Maxillo-Facial Surgery. 2017; 45(10):1716–23.
5. Egermark I, Magnusson T, Carlsson GE. A 20-year follow-up of signs and symptoms of temporoman-
dibular disorders and malocclusions in subjects with and without orthodontic treatment in childhood.
Angle Orthod. 2003; 73(2):109–15. https://doi.org/10.1043/0003-3219(2003)73<109:AYFOSA>2.0.
CO;2 PMID: 12725365
6. Guo J, Wang T, Han JJ, Jung S, Kook MS, Park HJ, et al. Corrective outcome and transverse stability
after orthognathic surgery using a surgery-first approach in mandibular prognathism with and without
facial asymmetry. Oral Surg Oral Med Oral Pathol Oral Radiol. 2018.
7. Hernandez-Alfaro F, Guijarro-Martinez R, Peiro-Guijarro MA. Surgery first in orthognathic surgery: what
have we learned? A comprehensive workflow based on 45 consecutive cases. Journal of oral and maxil-
lofacial surgery: official journal of the American Association of Oral and Maxillofacial Surgeons. 2014;
72(2):376–90.
8. Han JJ, Hwang SJ. Three-dimensional analysis of postoperative returning movement of perioperative
condylar displacement after bilateral sagittal split ramus osteotomy for mandibular setback with different
fixation methods. Journal of cranio-maxillo-facial surgery: official publication of the European Associa-
tion for Cranio-Maxillo-Facial Surgery. 2015; 43(9):1918–25.
9. Dervis E, Tuncer E. Long-term evaluations of temporomandibular disorders in patients undergoing
orthognathic surgery compared with a control group. Oral surgery, oral medicine, oral pathology, oral
radiology, and endodontics. 2002; 94(5):554–60. https://doi.org/10.1067/moe.2002.128021 PMID:
12424447
10. Kretschmer WB, Baciut G, Baciut M, Sader R. Effect of bimaxillary orthognathic surgery on dysfunction
of the temporomandibular joint: a retrospective study of 500 consecutive cases. The British journal of
oral & maxillofacial surgery. 2019; 57(8):734–9.

PLOS ONE | https://doi.org/10.1371/journal.pone.0238494 September 4, 2020 11 / 13

PLOS ONE Changes in the temporomandibular joint clicking and pain disorders after orthognathic surgery

11. Panula K, Somppi M, Finne K, Oikarinen K. Effects of orthognathic surgery on temporomandibular joint
dysfunction. A controlled prospective 4-year follow-up study. International journal of oral and maxillofa-
cial surgery. 2000; 29(3):183–7. PMID: 10970079
12. Pelo S, Saponaro G, De Angelis P, Gasparini G, Garagiola U, Moro A. Effect of Surgery First Orthog-
nathic Approach on the Temporomandibular Joint: A Clinical Evaluation. Journal of Craniofacial Sur-
gery. 2018; 29:1. https://doi.org/10.1097/SCS.0000000000004342 PMID: 29283959
13. Westermark A, Shayeghi F, Thor A. Temporomandibular dysfunction in 1,516 patients before and after
orthognathic surgery. The International journal of adult orthodontics and orthognathic surgery. 2001; 16
(2):145–51. PMID: 11482293
14. Wolford LM, Reiche-Fischel O, Mehra P. Changes in temporomandibular joint dysfunction after orthog-
nathic surgery. Journal of oral and maxillofacial surgery: official journal of the American Association of
Oral and Maxillofacial Surgeons. 2003; 61(6):655–60; discussion 61.
15. Yin Q, Bi R, Abotaleb B, Jiang N, Li Y, Zhu S. Changes in the position of the condyle after bilateral sagit-
tal split ramus osteotomy in patients with mandibular retrusion and protrusion: a new condyle: fossa
matching concept. The British journal of oral & maxillofacial surgery. 2019; 57(10):1086–91.
16. Han JJ, Jung S, Park HJ, Oh HK, Kook MS. Evaluation of Postoperative Mandibular Positional Changes
After Mandibular Setback Surgery in a Surgery-First Approach: Isolated Mandibular Surgery Versus
Bimaxillary Surgery. Journal of oral and maxillofacial surgery: official journal of the American Associa-
tion of Oral and Maxillofacial Surgeons. 2019; 77(1):181 e1–e12.
17. Liou EJ, Chen PH, Wang YC, Yu CC, Huang CS, Chen YR. Surgery-first accelerated orthognathic sur-
gery: orthodontic guidelines and setup for model surgery. Journal of oral and maxillofacial surgery: offi-
cial journal of the American Association of Oral and Maxillofacial Surgeons. 2011; 69(3):771–80.
18. Min BK, Choi JY, Baek SH. Comparison of treatment duration between conventional three-stage
method and surgery-first approach in patients with skeletal Class III malocclusion. The Journal of cra-
niofacial surgery. 2014; 25(5):1752–6. https://doi.org/10.1097/SCS.0000000000001002 PMID:
25148615
19. Yu HB, Mao LX, Wang XD, Fang B, Shen SG. The surgery-first approach in orthognathic surgery: a ret-
rospective study of 50 cases. International journal of oral and maxillofacial surgery. 2015; 44(12):1463–
7. https://doi.org/10.1016/j.ijom.2015.05.024 PMID: 26573566
20. Brucoli M, Zeppegno P, Benech R, Boffano P, Benech A. Psychodynamic Features Associated With
Orthognathic Surgery: A Comparison Between Conventional Orthognathic Treatment and "Surgery-
First" Approach. Journal of oral and maxillofacial surgery: official journal of the American Association of
Oral and Maxillofacial Surgeons. 2019; 77(1):157–63.
21. Park JK, Choi JY, Yang IH, Baek SH. Patient’s Satisfaction in Skeletal Class III Cases Treated With
Two-Jaw Surgery Using Orthognathic Quality of Life Questionnaire: Conventional Three-Stage Method
Versus Surgery-First Approach. The Journal of craniofacial surgery. 2015; 26(7):2086–93. https://doi.
org/10.1097/SCS.0000000000001972 PMID: 26468790
22. Han JJ, Chong JH, Ryu SY, Oh HK, Park HJ, Jung S, et al. Postoperative changes in mandibular posi-
tion after mandibular setback surgery via the surgery-first approach in relation to the increase of vertical
dimension and the amount of mandibular setback. Oral Surg Oral Med Oral Pathol Oral Radiol. 2016;
122(6):666–71. https://doi.org/10.1016/j.oooo.2016.07.016 PMID: 27717716
23. Ko EW, Hsu SS, Hsieh HY, Wang YC, Huang CS, Chen YR. Comparison of progressive cephalometric
changes and postsurgical stability of skeletal Class III correction with and without presurgical orthodon-
tic treatment. Journal of oral and maxillofacial surgery: official journal of the American Association of
Oral and Maxillofacial Surgeons. 2011; 69(5):1469–77.
24. Lian YK, Hsieh AMC, Tsai MS, Jiang HR, Yen CY, Hsia YJ, et al. Treatment efficiency and stability of
skeletal Class III malocclusion with a surgery-first approach. Orthodontics & craniofacial research.
2018; 21(2):90–5.
25. Wang T, Han JJ, Oh HK, Park HJ, Jung S, Kook MS. Comparison of Orthodontics-First and Surgery-
First Approach in Positional Changes of the Condyle After Mandibular Setback Surgery Using Three-
Dimensional Analysis. Journal of oral and maxillofacial surgery: official journal of the American Associa-
tion of Oral and Maxillofacial Surgeons. 2016; 74(12):2487–96.
26. Abrahamsson C, Henrikson T, Nilner M, Sunzel B, Bondemark L, Ekberg EC. TMD before and after cor-
rection of dentofacial deformities by orthodontic and orthognathic treatment. International journal of oral
and maxillofacial surgery. 2013; 42(6):752–8. https://doi.org/10.1016/j.ijom.2012.10.016 PMID:
23159168
27. Aghabeigi B, Hiranaka D, Keith DA, Kelly JP, Crean SJ. Effect of orthognathic surgery on the temporo-
mandibular joint in patients with anterior open bite. The International journal of adult orthodontics and
orthognathic surgery. 2001; 16(2):153–60. PMID: 11482294

PLOS ONE | https://doi.org/10.1371/journal.pone.0238494 September 4, 2020 12 / 13

PLOS ONE Changes in the temporomandibular joint clicking and pain disorders after orthognathic surgery

28. Togashi M, Kobayashi T, Hasebe D, Funayama A, Mikami T, Saito I, et al. Effects of surgical orthodontic
treatment for dentofacial deformities on signs and symptoms of temporomandibular joint. Journal of
Oral and Maxillofacial Surgery, Medicine, and Pathology. 2013; 25:18–23.
29. Baek SH, Ahn HW, Kwon YH, Choi JY. Surgery-first approach in skeletal class III malocclusion treated
with 2-jaw surgery: evaluation of surgical movement and postoperative orthodontic treatment. J Cranio-
fac Surg. 2010; 21(2):332–8. https://doi.org/10.1097/SCS.0b013e3181cf5fd4 PMID: 20186090
30. Al-Riyami S, Cunningham SJ, Moles DR. Orthognathic treatment and temporomandibular disorders: A
systematic review. Part 2. Signs and symptoms and meta-analyses. American Journal of Orthodontics
and Dentofacial Orthopedics. 2009; 136(5):626.e1–.e16.
31. Jerjes W, Hamdoon Z, Abbas S, Algamal Z. Temporomandibular joint dysfunction in orthognathic sur-
gery: systematic review. British Journal of Oral & Maxillofacial Surgery—BRIT J ORAL MAXILLOFAC
SURG. 2011; 49.
32. Gaggl A, Schultes G, Santler G, Karcher H, Simbrunner J. Clinical and magnetic resonance findings in
the temporomandibular joints of patients before and after orthognathic surgery. The British journal of
oral & maxillofacial surgery. 1999; 37(1):41–5.
33. Karabouta I, Martis C. The TMJ dysfunction syndrome before and after sagittal split osteotomy of the
rami. Journal of maxillofacial surgery. 1985; 13(4):185–8. https://doi.org/10.1016/s0301-0503(85)
80045-x PMID: 3860598
34. Scolozzi P, Wandeler PA, Courvoisier DS. Can clinical factors predict postoperative temporomandibular
disorders in orthognathic patients? A retrospective study of 219 patients. Oral Surg Oral Med Oral
Pathol Oral Radiol. 2015; 119(5):531–8. https://doi.org/10.1016/j.oooo.2015.01.006 PMID: 25767066
35. Jacobson A. Duration of orthodontic treatment involving orthognathic surgery. American Journal of
Orthodontics and Dentofacial Orthopedics. 1999; 116:A1.
36. O’Brien K, Wright J, Conboy F, Appelbe P, Bearn D, Caldwell S, et al. Prospective, multi-center study of
the effectiveness of orthodontic/orthognathic surgery care in the United Kingdom. American Journal of
Orthodontics and Dentofacial Orthopedics. 2009; 135(6):709–14. https://doi.org/10.1016/j.ajodo.2007.
10.043 PMID: 19524829
37. Jeong WS, Choi JW, Kim DY, Lee JY, Kwon SM. Can a surgery-first orthognathic approach reduce the
total treatment time? International journal of oral and maxillofacial surgery. 2016; 46(4):473–82. https://
doi.org/10.1016/j.ijom.2016.12.006 PMID: 28043746
38. Zingler S, Hakim E, Finke D, Brunner M, Saure D, Hoffmann J, et al. Surgery-first approach in orthog-
nathic surgery: Psychological and biological aspects—A prospective cohort study. Journal of cranio-
maxillo-facial surgery: official publication of the European Association for Cranio-Maxillo-Facial Sur-
gery. 2017; 45(8):1293–301.

PLOS ONE | https://doi.org/10.1371/journal.pone.0238494 September 4, 2020 13 / 13