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Three Dimensional Changes in the Pharyngeal Airway Space after Mandibular Setback Surgery

: 1 Year Follow Up

by

No Eul Kang

Major in Oral and Maxillofacial Surgery Department of Clinical Dentistry

Graduate School of Clinical Dentistry

Ajou University

Three Dimensional Changes in the Pharyngeal Airway Space after Mandibular Setback Surgery

: 1 Year Follow Up

by

No Eul Kang

A Dissertation Submitted to Graduate School of Clinical Dentistry, Ajou University in Partial Fulfillment of the Requirements

for the Degree of Master of Science in Dentistry

Supervised by

Seung-Il Song, DDS, Ph.D.

Major in Oral and Maxillofacial Surgery Department of Clinical Dentistry

Graduate School of Clinical Dentistry Ajou University

August, 2021

i – ABSTRACT –

Three Dimensional Changes in the Pharyngeal Airway Space after Mandibular Setback Surgery

: 1 Year Follow-up

Objectives: This study evaluated the long term changes up to 1 year in the pharyngeal airway space after bilateral sagittal split ramus osteotomy mandibular setback surgery and bimaxillary surgery through three-dimensional computed tomography analysis.

Materials and Methods: A total of 37 patients diagnosed with skeletal class III malocclusion underwent BSSRO setback surgery only (Group 1, n=23) or bimaxillary surgery (Group 2, n=14). Cone-beam computed tomography scan were taken before surgery (T0), 2 months after surgery (T1), 6 months after surgery (T2) and 1 year after surgery (T3). The nasopharynx (Nph), oropharynx (Oph), hypopharynx (Hph) volume and anteroposterior (AP) distance were measured through the InVivo Dental Application version 5.

Results:In Group 1, Oph volume and Hph volume were significantly decreased and maintained after the surgery (T1). In Group 2, Nph volume, Oph volume and Hph volume were decreased and relapsed at 1 year postoperatively (T3).

Conclusion: In Class III malocclusion patients, mandibular setback surgery only showed a greater reduction in pharyngeal airway space than bimaxillary surgery, and bimaxillary

ii

surgery was more stable in terms of airway. Therefore, it is important to evaluate the airway space before surgery and include it in the surgical plan.

Key words: Mandibular setback surgery, Bimaxillary surgery, Class III malocclusion,

Pharyngeal airway, CBCT

iii

TABLE OF CONTENTS

ABSTRACT ··· i

TABLE OF CONTENTS ··· iii

LIST OF FIGURES ··· iv

LIST OF TABLES ··· v

Ⅰ. INTRODUCTION ··· 1

Ⅱ. MATERIALS AND METHODS ··· 3

A. Patients ··· 3

B. CBCT examination and measurements ··· 4

C. Statistical analysis ··· 10

Ⅲ. RESULTS ··· 11

Ⅳ. DISCUSSION ··· 21

Ⅴ. CONCLUSION··· 25

REFERENCES ··· 26

국문요약 ··· 31

iv

LIST OF FIGURES

Fig. 1. Pharyngeal airway division and measurements ··· 8

Fig. 2. Pharyngeal airway volume measurement ··· 9

Fig. 3.Mean pharyngeal AP distance ··· 14

Fig. 4.Mean pharyngeal volume ··· 15

Fig. 5.SV-B distance change ··· 19

Fig. 6.Pharyngeal volume change ··· 20

v

LIST OF TABLES

Table 1. The landmarks and the reference plane ··· 6

Table 2. Pharyngeal airway measurements ··· 7

Table 3. Measurements and comparison of pharyngeal airway in group 1 (BSSRO) ··· 12

Table 4. Measurements and comparison of pharyngeal airway in group 2 (BSSRO + Le Fort I osteotomy) ··· 13

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Ⅰ. INTRODUCTION

Many patients with skeletal class III malocclusion have esthetic and functional problems, and orthognathic surgery accompanying bilateral sagittal split osteotomy (BSSRO) setback surgery is administered to improve them. This surgery provides

satisfactory results to patients by improving the mastication, pronunciation, aesthetics, and psychological factors of the patient by changing the skeletal position of mandible alone or both mandible and maxilla.

Orthognathic surgery affects not only hard tissue but also soft tissue, and affects the somatognathic system overall. The oropharyngeal complex is composed of the hyoid bone and the muscles connected to it, and is anatomically and functionally related to the

mandible, resulting in changes after orthognathic surgery with mandible movement. When the mandible is moved backward by surgery, tongue, hyoid bone and muscles attached are located posterior to its original position, and as a result, the airway volume is narrowed (Azevêdo, et al. 2016; Fernández-Ferrer, et al. 2015; Hart, et al. 2015; Hatab, et al. 2015;

He, et al. 2017; Kim, et al. 2014; Kim, et al. 2010; Li, et al. 2014). Many previous studies have shown that mandible setback surgery narrows the pharyngeal airway(He, et al. 2017;

Mattos, et al. 2011; Panou, et al. 2013; Santagata, et al. 2015). Several studies have reported that postoperative obstructive sleep apnea (OSA) occurred as a result (Hart, et al.

2015; He, et al. 2017; Mattos, et al. 2011; Santagata, et al. 2015; Uesugi, et al. 2014). On the other hand, in the case of BSSRO setback surgery with Le Fort I osteotomy, there are

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reports that the decrease in pharyngeal airway volume is less than in patients who underwent mandibular setback surgery only, and there are some studies that the

anteroposterior (AP) dimension is rather increased in the upper pharyngeal airway after the surgery(Chen, et al. 2007; Degerliyurt, et al. 2008; Hong, et al. 2011).

In the previous study, two-dimensional analysis using cephalometric radiographs was performed to investigate the change of pharyngeal airway, but there were limitations in the analysis of the three-dimensional(3D) pharyngeal airway space or volume (Liukkonen, et al. 2002; Pereira-Filho, et al. 2011). Cone beam computed tomography (CBCT) is a three-dimensional image that is very useful for preoperative diagnosis, operation planning, and evaluation of postoperative results. It also provides high quality while reducing

scanning time and irradiation compared to conventional CT. In addition, CT image is useful for evaluating pharyngeal airway including both hard tissue and soft tissue, and it is

possible to visualize a 3D image to help intuitive understanding. Nowadays, as many CT scans and programs are developed, there are some studies evaluating the volumetric evaluation of airway after surgery (Becker, et al. 2012; Burkhard, et al. 2014; Foltán, et al.

2009; Gokce, et al. 2014; Jiang 2016; Uesugi, et al. 2014). Most of them were limited to only BSSRO setback surgery, and there were not many cases that the volume change was observed for a long term until 1 year.

The purpose of our study was to evaluate the long term changes up to 1 year in the pharyngeal airway space after BSSRO surgery or bimaxillary surgery, according to each surgical method and long-term adaptation through three-dimensional CBBT analysis.

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Ⅱ. MATERIALS AND METHODS

A.Patients

From February 2014 to April 2019, 37 patients (19 men, 18 women; mean age 23.2±5.47 years) diagnosed with skeletal class III malocclusion and who underwent BSSRO setback surgery or bimaxillary surgery by the same operator at the AJOU University School of Medicine (Suwon, Korea) were included in this study. All the patients followed for more than 1 year and pre- and postorthodontic treatments were provided. Patients who had craniofacial syndromes, such as cleft lip and palate, cranial trauma or upper respiratory lesions or who underwent other surgery such as genioplasty were excluded.

Patients were divided into two groups: (1) 1 jaw surgery patients (BSSRO setback surgery only), (2) 2 jaw surgery patients (Le Fort I osteotomy and BSSRO setback surgery).

The surgical method was different for group 1 and group 2. In the case of group 1, BSSRO setback surgery was performed, followed by rigid fixation. In group 2, after Le Fort I osteotomy, maxilla was moved to the desired position, rigid fixation was performed, and mandible BSSRO setback surgery was performed as in Group 1. After surgery, all patients had to wear wafers for 2-4 weeks to stabilize occlusion, and postorthodontic treatment was performed afterwards.

Ajou University School of Medicine Institutional Review Board (AJIRB-MED-MDB- 20-078) approved the study protocol

- 4 - B. CBCT examination and measurements

CBCT scan were taken before surgery (T0), 2 months after surgery (T1), 6 months after surgery (T2) and 1 year after surgery (T3). During CT scan, in order to have a

reproducible posture, patients were asked to take natural head position (NHP). Patients were asked to stand and stare at the front mirror, and the lips, chin, and masticatory muscles were relaxed to take a reproducible posture.

CBCT (Dinnova3, HDX, Seoul, Korea) of Ajou University Dental Hospital was used, and the imaging conditions were 80kVp, 7.0mA, and scan time for 20 seconds. The slice thickness was 0.3mm and the distance between slices was 1.0mm. CT digital image files were exported using the Digital Imaging and Communications in Medicine (DICOM) format and imported into the InVivo Dental Application version 5 (Anatomage, San Jose, Calif). The landmarks, reference planes and measurement points used in this study are as follows (Table 1, 2). Since the measured value varies according to the head position, re- orientation was performed by setting the nasion as the origin point, the FH plane passing through the orbitale and the porion as the horizontal reference plane, and the SV plane passing through the sella and basion as the sagittal reference plane (Table 1).

The pharyngeal airway is surrounded by soft tissue, and the airway space from the top of the pharynx to the epiglottis plane is defined as the whole pharynx, and the nasal cavity and oral cavity are excluded. The pharynx was divided into three areas based on the PNS plane and the P plane, and defined as nasopharynx (Nph), oropharynx (Oph), and

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hypopharynx (Hph) from above (Fig. 1). It was measured through the InVivo Dental Application version 5 (Fig. 2).

- 6 - Table 1. The landmarks and the reference plane

Landmark (Abbreviation) Definition

Landmarks

Nasion (Na) "V" notch of frontal, and nasal bones Ba (Basion) Most inferior point of the occipital bone Or (Orbitale) Most inferior point of orbital contour

Po (Porion) Most superior point of external auditory meatus Se (Sella) Center of sella turcica

Anterior nasal spine (ANS) Tip of the anterior nasal spine Posterior Nasal Spine (PNS) Tip of the posterior nasal spine

B point (B) Deepest point between pogonion and lower incisal alveolus

P point (P) The most inferior point of soft palate E point (E) Base of epiglottis

Reference plane

Frankfort horizontal (FH) plane Faces through right porion and both side of orbitales Midsagittal plane A plane perpendicular to the FH plane passing through Na

and Ba

Sella vertical (SV) plane A plane perpendicular to the FH plane passing through Se, Ba, and Na

PNS plane Axial plane passing through Posterior Nasal Spine Soft palate plane Axial plane passing through most inferior point of soft

palate

Epiglottis plane Axial plane passing through base of epiglottis on anterior pharyngeal wall

- 7 - Table 2. Pharyngeal airway measurements

Measurements Definition

Nph AP Nasopharyngeal airway distance, antero-posterior distance from PNS to pharyngeal airway posterior wall on PNS plane

Oph AP Oropharyngeal airway distance, antero-posterior distance from P to pharyngeal airway posterior wall on soft palate plane

Hph AP Hypopharyngeal airway distance, antero-posterior distance from E to pharyngeal airway posterior wall on Epiglottis plane

Nph vol Nasopharyngeal airway volume, top of the pharyngeal airway to PNS plane

Oph vol Oropharyngeal airway volume, between the PNS plane and the soft palate plane

Hph vol Hypopharyngeal airway volume, from soft palate plane to Epiglottis plane

Whole pharynx volume Sum of the Nph volume, Oph volume and Hph volume SV-B The distance from the Sella vertical (SV) plane to the B point

- 8 -

Fig 1. Pharyngeal airway division and measurements. (A) The airway space divided into three areas based on reference planes. (1) posterior nasal spine plane; (2) soft palate plane;

(3) epiglottis plane; A, the nasopharyngeal volume (Nph vol); B, oropharyngeal volume (Oph vol); C, hypopharyngeal volume (Hph vol); (a) Nph AP: nasopharyngeal antero- posterior distance; (b) Oph AP: oropharyngeal anteroposterior distance; (c) Hph AP:

hypopharyngeal antero-posterior distance. (B) Measurement of SV-B. (d) SV-B: the distance from the sella vertical (SV) plane to the B point.

- 9 -

Fig 2. Pharyngeal airway volume measurement. Volume was measured through the InVivo Dental Application version 5

- 10 - C. Statistical analysis

Methodological errors in the measurement were minimized by double recording of the same investigator. The shapiro-wilk test was performed for the normalization test. A paired t test was used to evaluate surgical changes of pharyngeal space (T1-T0) and relapse (T2-T1, T3-T2) in each group. Probability values less than 0.05 was deemed statistically significant.

SPSS Statistics version 23.0 software (SPSS Inc., Chicago, IL, USA) was used for all statistical analyses

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Ⅲ. RESULT

The measurements before surgery (T0), 2 months after surgery (T1), 6 months after surgery (T2) and 1 year after surgery (T3) in group 1 are shown in Table 3. Data for group 2 are shown in Table 4.

A. Nasopharyngeal airway change

In group 1, the average Nph AP was 18.5mm preoperatively, and there was no significant change from 18.84mm immediately after surgery to 18.32mm at 1 year

postoperatively (P>0.05). The mean preoperative Nph vol was measured to be 3.53 cm³ and was 3.45 cm³ at 1 year postoperatively, with no difference before and after surgery like Nph AP (P>0.05) (Table 3, Fig. 3, 4).

In group 2, the Nph AP was 18.37mm, which was similar to the preoperative average of group 1, but the average was 19.79mm at 2 months after surgery, which was significantly increased by 1.42mm (P<0.05) and remained at 19.46mm at 1 year after surgery.

The average Nph vol decreased from 3.24 cm³ preoperatively to 2.11 cm³ at 2 months postoperatively and 1.07 cm³ decreased to 2.17 cm³ at 6 months postoperatively (P<0.01). At 1 year postoperatively, it relapsed with an increase of 0.07 cm³ to 2.24 cm³ (P>0.05) (Table 4, Fig. 3, 4).

A

B

- 12 -

Table 3. Measurements and comparison of pharyngeal airway in group 1 (BSSRO)

T0: Before surgery; T1: 2 months after surgery; T2: 6 months after surgery; T3: 1 year after surgery; Nph AP: Anteroposterior distance of nasopharynx; Oph AP: Anteroposterior distance of oropharynx; Hph AP: Anteroposterior distance of hypopharynx; SV-B: distance from the sella vertical (SV) plane to the B point; *Significant at P<0.05, **Significant at P<0.01.

Variable

T0 T1 T2 T3

T0-T1 T0-T2 T0-T3 T1-T2 T2-T3 Mean±SD

Nph AP 18.52±4.15 18.84±3.98 18.70±3.50 18.32±3.48

Oph AP 12.53±4.57 10.70±4.61 10.43±4.15 11.36±4.28 ** ** *

Hph AP 15.62±4.43 14.13±3.69 14.45±3.16 15.24±4.04 **

Nasopharynx volume 3.53±1.94 3.88±2.03 3.66±1.63 3.45±1.79

Oropharynx volume 7.15±3.01 6.12±2.57 5.99±2.61 5.75±2.75 * *

Hypopharynx volume 8.37±4.46 7.00±4.41 7.09±3.24 7.07±4.28 ** * * Whole-pharynx volume 19.47±1.44 16.99±1.54 16.73±6.02 16.27±7.20 * ** * SV-B 65.08±7.38 60.12±5.46 60.52±6.09 60.86±5.51 ** ** **

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Table 4. Measurements and comparison of pharyngeal airway in group 2 (BSSRO + Le Fort I osteotomy)

T0: Before surgery; T1: 2 months after surgery; T2: 6 months after surgery; T3: 1 year after surgery; Nph AP: Anteroposterior distance of nasopharynx; Oph AP: Anteroposterior distance of oropharynx; Hph AP: Anteroposterior distance of hypopharynx; SV-B: the distance from the sella vertical (SV) plane to the B point; *Significant at P<0.05, **Significant at P<0.01.

Variable

T0 T1 T2 T3

T0-T1 T0-T2 T0-T3 T1-T2 T2-T3 Mean±SD

Nph AP 18.37±4.03 19.79±4.24 19.15±1.18 19.46±1.04 * *

Oph AP 15.48±4.70 14.21±4.30 12.56±0.95 14.69±0.96 * *

Hph AP 15.75±2.74 15.63±2.95 15.28±0.65 15.88±0.74

Nasopharynx volume 3.24±0.98 2.11±0.67 2.17±0.23 2.24±0.29 ** **

Oropharynx volume 9.20±4.85 8.28±4.43 8.14±1.18 9.83±1.18 **

Hypopharynx volume 7.77±0.98 8.30±0.96 6.93±0.85 8.40±0.94

Whole-pharynx volume 20.21±2.22 18.68±1.98 17.24±1.93 20.47±2.04 *

SV-B 63.93±2.11 57.13±1.99 57.35±1.71 57.51±1.76 ** ** **

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Fig 3. Mean pharyngeal AP distance. (A) Group 1 (BSSRO). (B) Group 2 (BSSRO + Le Fort I osteotomy). T0: Before surgery; T1:

2 months after surgery; T2: 6 months after surgery; T3: 1 year after surgery; Nph AP: Anteroposterior distance of nasopharynx; Oph AP: Anteroposterior distance of oropharynx; Hph AP: Anteroposterior distance of hypopharynx

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Fig 4. Mean pharyngeal volume. (A) Group 1(BSSRO). (B) Group 2 (BSSRO + Le Fort I osteotomy). T0: Before surgery; T1: 2 months after surgery; T2: 6 months after surgery; T3: 1 year after surgery; Nph volume: volume of nasopharynx; Oph vol: volume of oropharynx; Hph vol: volume of hypopharynx; Whole vol: Sum of the Nph vol, Oph vol and Hph vol.

- 16 - B. Oropharyngeal airway change

In group 1, the average preoperative measurement of Oph AP was 12.53mm and decreased to an average of 10.70mm at 2 months after surgery (P<0.01), and the value of 10.43mm decreased the most at 6 months after surgery (P<0.01). After that, it regressed somewhat, resulting in a decrease of 1.17mm to 11.36mm after 1 year (P<0.05). Oph vol gradually decreased from 7.15cm³ preoperatively to 5.99 cm³ at 6 months postoperatively (P<0.05) and decreased to 5.75cm³ at 1 year postoperatively (P<0.05) (Table 3, Fig. 3, 4).

In group 2, the preoperative mean of Oph AP was 15.48mm and decreased to 12.56mm until 6 months postoperatively (P<0.05), and then returned to 15.88mm at 1 year postoperatively. Oph vol decreased from an average of 9.20cm³ preoperatively to 8.14cm³ 6 months postoperatively and then returned to 9.83cm³ at 1 year postoperatively, but was not significant (P>0.05) (Table 4, Fig. 3, 4).

C. Hypopharyngeal airway change

In group 1, the Hph AP value decreased significantly from 15.62mm

preoperatively to 14.13mm at 2 months postoperatively (P<0.01) and gradually increased to 15.24mm after 1 year postoperatively. Hph vol decreased from 8.37cm³ preoperatively to 7.00 cm³ at 2 months postoperatively (P<0.01) and decreased to 7.09cm³ at 6 months and 7.07 cm³ at 1 year postoperatively (P<0.05) (Table 3, Fig. 3, 4).

In group 2, Hph AP was 15.75mm preoperatively and no change was observed until 1 year postoperatively. The average Hph vol value was 7.77 cm³ preoperatively, and no significant change was observed until the first year (P>0.05) (Table 4, Fig. 3, 4).

D. Whole-pharynx volume change

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Whole-pharynx volume is the sum of the nasopharyngeal, oropharyngeal, and hypopharyngeal airway volume values. Whole pharynx volume in group 1 significantly decreased from 19.47cm³ preoperatively to 16.99cm³ at 2 months postoperatively by 2.44cm³ (P<0.05) and decreased the most to 16.73cm³ at T2 (P<0.01). At T3 the value increased to 16.27cm³ and significantly decreased compared to the preoperative period (P<0.05) (Table 3, Fig. 4).

In Group 2, whole-pharynx volume decreased from 20.21cm³ before surgery to 18.68cm³ at 2 months after surgery and 17.24cm³ after 6 months, but there was no significant change in comparison (P>0.05). In addition, when comparing whole pharynx volume at T2 with T3, the average increased significantly from 17.24cm³ to 20.47cm³ (P<0.05) and regressed to a similar value to the preoperative average of 20.21 cm³ (Table 4, Fig. 4).

E. B point change (Setback amount)

SV-B is the distance from the sella vertical plane to the B point, which is

measured to know the setback amount and relapse tendency. The difference between the SV- B values before and after surgery means the setback amount.

In group 1, the average preoperative SV-B was 65.08mm, and in group 2, the average preoperative SV-B was 63.93mm. The amount of change in SV-B value T0 and T1 was 4.96 mm in group 1 and 6.8 mm in group 2. In both groups, the SV-B value decreased significantly at T1 (P<0.01), and the decreased value was maintained until T3 (Table 3, 4, Fig. 5).

- 18 -

In Group 1, Oph volume and Hph volume were significantly decreased after the surgery (T1) and maintained. In Group 2, Nph volume, Oph volume and Hph volume were decreased and relapsed at 1 year postoperatively (T3) (Fig. 6).

- 19 -

Fig 5. SV-B distance change. (A) Group 1(BSSRO). (B) Group 2 (BSSRO + Le Fort I osteotomy). T0: Before surgery; T1: 2 months after surgery; T2: 6 months after surgery; T3: 1 year after surgery; SV-B: the distance from the sella vertical (SV) plane to the B point

- 20 -

Fig 6. Pharyngeal volume change. Group 1 (BSSRO); Group 2 (BSSRO + Le Fort I osteotomy). T0: Before surgery; T1: 2 months after surgery; T2: 6 months after surgery; T3:

1 year after surgery

- 21 -

IV. DISCUSSION

BSSRO setback surgery and bimaxillary surgery are often used to treat class III malocclusion patients. Since there is a possibility of OSA after surgery, it is necessary to evaluate the pharyngeal airway before and after surgery. Because of its relatively simple and inexpensive advantage, many studies have used lateral cephalograms for preoperative and postoperative airway evaluation.

Riley & Powell said that both CT and cephalometry are quite accurate for

measuring the airway volume (Riley and Powell 1990). However, Lenza et al argued that the airway could not be represented accurately by linear measurements only on cephalogram (Lenza, et al. 2010). Because of its low exposure and intuitive viewing of 3D structures, CBCT is widely used in hospitals these days. Since it is taken before and after surgery, during diagnosis, planning, and follow-up, it is possible to evaluate hard tissue and soft tissue in 3D for pharyngeal airway. There have been many studies on pharyngeal airway analysis through CT after mandible setback surgery, and various reference points, planes and measurements were used (Hatab, et al. 2015; Park, et al. 2012; Uesugi, et al. 2014). In this study, the changes in pharyngeal airway after two types of mandibular setback surgery were investigated. The Invivo5 program was used for CT analysis, and since the measured values for the airway may vary depending on the posture, re-orientation was performed based on the right porion and the FH plane passing through the orbitales with nasion as the origin. The landmarks, Se, PNS, P, E, B point, were indicated, and Nph AP, Oph AP, Hph AP were measured for AP distance, and Nph vol, Oph vol, Hph vol and whole pharyngeal volume

- 22 -

were measured to obtain volumetric change. The SV-B distance was measured to find out the amount of mandible setback and the tendency to relapse.

Holmberg et al found that Nph is not influenced by mandibular setback surgery (Holmberg and Linder-Aronson 1979). Wenzel et al reported that after BSSRO setback surgery, Nph AP decreased by 2.3mm after surgery and maintained until 1 year (Wenzel, et al.

1989). In the present study, there was no significant change in both Nph AP and Nph vol after surgery in Group 1 patients, and this was the same as that of Hatab, Park et al, and Uesugi et al (Hatab, et al. 2015; Park, et al. 2012; Uesugi, et al. 2014). Most of the studies reported that Nph measurements were not related to surgery in both Group 1 and Group 2, but in our study, Nph AP increased after surgery in group 2 patients, but Nph vol decreased, which was the same as the result of Kim et al (Kim, et al. 2015). Kim observed that in Le Fort 1 osteotomy with posterior impaction and mandibular setback surgery patients, the distance from PNS to the posterior pharynx wall significantly increased by an average of 1.68 mm after 6 months of surgery. In this study, most of the Le Fort 1 osteotomy surgery in group 2 was accompanied by posterior impaction, which caused the PNS to move anteriorly and upward with clockwise rotation. The Nph AP appeared to increase due to the forward movement of the PNS, and the volume was predicted to decrease due to the decrease in the Nph height with the PNS upward movement.

Enacar et al found that the volume of the oropharyngeal airway remained reduced for more than 1 year and 6 months in mandibular setback surgery patients (Enacar, et al.

1994). The hyoid bone and lower tongue point moved down, and accordingly, the hypopharyngeal airway space was significantly reduced. Tselink and Hochban, however, found that the oropharyngeal airway reduced postoperatively and recovered (Hochban, et al.

1997; Tselnik and Pogrel 2000). In the present study, oropharyngeal and hypopharyngeal

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volume significantly decreased and maintained for up to 1 year in group 1. Park et al and GRECO et al suggested that the Oph was affected more by mandible retrusion because it is close to mandible and the tongue anatomically (Greco, et al. 1990; Park, et al. 2012). In this study, in group 2, Oph AP, Hph AP, oropharyngeal volume and hypopharyngeal volume decreased immediately after surgery and then gradually increased until 1 year

postoperatively and relapsed, but this was not significant. This is consistent with the results of previous papers that the reduction of airway diminished after surgery (Chen, et al. 2007;

Degerliyurt, et al. 2008; Park, et al. 2012).

The change of whole pharynx volume was significantly decreased and maintained in group 1, but in group 2, there was a tendency to relapse after postoperative reduction, and no significant change was observed. The whole pharynx volume change was calculated by adding Nph vol, Oph vol, and Hph vol, respectively, and whole pharynx volume change was similar to that of Hph and Oph. The proportion of the whole pharynx was Hph, Oph, and Nph in order (Table 2,3, Fig. 4). Accordingly, the whole pharynx volume change seems to be affected by the change of Hph and Oph.

In the present study, no patients complained of postoperative OSA or severe and persistent snoring. However, after orthognathic surgery, especially when only mandibular setback was performed, the volume and distance of the pharyngeal airway were decreased.

Joss et al argued that relapse was caused by the upper airway and soft palate adapted to the shortened mandible after mandibular setback surgery (Joss and Vassalli 2009).

In this study, group 1 had an average postoperative setback of 4.96mm, an average of 0.74mm relapse at 1 year postoperatively, and about 14.92% relapse. In group 2, the setback amount was 6.8mm on average, which was larger than that in group 1. 1 year after surgery,

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the setback amount was relpased by 0.38mm, resulting in 5.59% relapse. Through this, it can be said that bimaxillary surgery is more stable in terms of relapse than 1 jaw surgery.

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Ⅴ. CONCLUSION

In Class III malocclusion patients, mandibular setback surgery only showed a greater reduction in pharyngeal airway than bimaxillary surgery, and bimaxillary surgery was more stable in terms of airway. Therefore, it is important to evaluate the airway before surgery and include it in the surgical plan.

- 26 - REFERENCES

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턱교정 수술 후 상기도 공간의 3 차원적 변화 : 1 년 추적 검사

아주대학교 임상치의학대학원 임상치의학과/구강악안면외과학 전공

강 노 을

(지도교수 : 송 승 일)

목적 : 본 연구의 목적은 편악 BSSRO 하악후퇴술 또는 Le Fort I 절골술을

동반하는 BSSRO 하악후퇴술을 시행한 환자에서 컴퓨터단층화 영상 검사를 통해 1 년동안 추적 검사를 통하여 3 차원적인 상기도 공간의 변화를 알아보는 것이다.

재료 및 방법 : 아주대학교 치과병원에서 골격성 III 급 부정교합을 진단받은 37 명의 환자를 편악 BSSRO 하악후퇴술을 시행한 그룹과 (Group 1, n=23) Le Fort I 절골술을 동반한 BSSRO 하악후퇴술을 시행한 그룹(Group 2, n=14)로 나누었다. 콘빔 컴퓨터단층화 영상을 수술 전(T0), 수술 2 달 후(T1), 수술 6 개월 후(T2), 수술 1 년 후(T3)에 시행하였다. 상기도 공간을 비인두공간, 구강인두공간 및 하인두공간으로 나누고 각각의 부피와 전후방 길이를 Invivo Dental Application version 5 를 통해 측정하였다.

결과 : 그룹 1 에서 구강인두공간 및 하인두공간의 부피는 수술 후(T1)

유의미하게 감소한 후 유지되었다(P<0.05). 그룹 2 에서 비인두공간, 구인두공간

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및 하인두공간의 부피는 수술 후 감소하였으나 수술 후 1 년째(T3)에 회귀 되어 수술 전 상기도공간의 부피로 회복되었다.

결론 : 골격성 III 급 부정교합 환자에서 하악후퇴술만 시행한 환자들이 양악수술을 시행한 환자에 비해 상기도공간이 더 크게 감소하였다. 기도의 안정성 측면에서 양악 수술이 더 안정적인 결과를 나타냈다. 그러므로 수술 전 CT 를 통해 기도를 평가하고 이를 수술계획에 반영하는 것이 중요하다.

Key words: 하악후퇴술, 양악수술, III 급 부정교합, 상기도 공간, CBCT