저 시-비 리- 경 지 2.0 한민

는 아래 조건 르는 경 에 한하여 게

l 저 물 복제, 포, 전송, 전시, 공연 송할 수 습니다.

다 과 같 조건 라야 합니다:

l 하는, 저 물 나 포 경 , 저 물에 적 된 허락조건 명확하게 나타내어야 합니다.

l 저 터 허가를 면 러한 조건들 적 되지 않습니다.

저 에 른 리는 내 에 하여 향 지 않습니다.

것 허락규약(Legal Code) 해하 쉽게 약한 것 니다.

Disclaimer

저 시. 하는 원저 를 시하여야 합니다.

비 리. 하는 저 물 리 목적 할 수 없습니다.

경 지. 하는 저 물 개 , 형 또는 가공할 수 없습니다.

Three-dimensional changes of the

nasolabial fold and the perioral soft tissue

following orthodontic retraction of

lip protrusion

Eui Seon Baek

The Graduate School

Yonsei University

Department of Dentistry

[UCI]I804:11046-000000514837[UCI]I804:11046-000000514837[UCI]I804:11046-000000514837[UCI]I804:11046-000000514837

Three-dimensional changes of the nasolabial fold

and the perioral soft tissue following

orthodontic retraction of lip protrusion

Directed by associate prof. Chooryung J. Chung, D.D.S., Ph.D.

The Doctoral Dissertation

submitted to the Department of Dentistry,

the Graduate School of Yonsei University

in partial fulfillment of the requirements for the degree of

Ph.D. in Dental Science

Eui Seon Baek

December 2017

감사의 글

부족한 저를 애정 어린 지도와 자상한 배려로 이끌어 주신 정주령 교수님께

깊은 감사의 말씀을 전합니다. 연구자가 갖추어야 할 자세를 깨우쳐 주시고,

항상 연구의 본질에 집중하도록 이끌어 주심에 감사합니다. 매사에 편견 없이

열린 지성을 보여주시는 교수님을 진심으로 존경합니다.

논문이 완성될 때까지 바쁘신 와중에도 지속적인 관심과 도움을 주신

김경호 교수님, 학문적 예리함으로 오류를 일일이 고쳐 주신 최윤정 교수님과

황순신 교수님, 타 과의 관점으로 학문적 근거를 더욱 정교히 다듬어 주신

피부과 노미령 교수님과 미국에 계신 Tung Nquyen 교수님께도 깊은 감사의

말씀을 드립니다. 비순구 평가자로서 연구에 참여해 주신 교정과 최성환

교수님, 건양대 김훈 교수님, 성형외과 홍종원 교수님, 노태석 교수님께

감사합니다. 또한 저를 교정 의사로 거듭나게 해주시고 수련의 및 대학원생

시절 많은 가르침을 주신 박영철 교수님, 백형선 교수님, 황충주 교수님,

유형석 교수님, 이기준 교수님, 차정열 교수님과 의국 선배님들께도 이

기회를 빌어 감사의 마음을 전합니다.

통계분석에 큰 도움을 주신 정시내 선생님, 연구 기간 많은 도움을 주었던

이준구 선생 등 의국 후배들 에게도 감사의 마음을 전하고 싶습니다. 또한

항상 반갑게 맞아주는 강남 세브란스 치과병원 교정과 직원 분들께도

감사합니다.

사랑과 믿음으로 지켜봐 주신 가족에게도 감사의 마음을 전합니다.

마지막으로 늘 곁에서 지지와 격려를 해준 사랑하는 상수오빠에게 고마움을

전하며 이 기쁨을 함께 나누고 싶습니다.

2017 년 12 월

백 의 선

i

TABLE OF CONTENTS

LEGENDS OF FIGURES ······························································· iіі

LEGENDS OF TABLES ································································ iv

ABSTRACT (ENGLISH) ······························································· v

I. INTRODUCTION ····································································· 1

II. MATERIAL AND METHODS ····················································· 3

1. Subjects ················································································· 3

2. Data acquisition ······································································· 4

3. Coordinate system and landmarks ·················································· 4

4. Clinical assessments of the nasolabial folds (NLFs) ····························· 9

5. Statistical analysis ··································································· 11

III. RESULTS ············································································ 13

1. Initial soft and hard tissue characteristics ········································ 13

2. Three-dimensional changes in the facial soft tissue and the NLFs following

anterior retraction ··································································· 14

3. Clinical factors associated with the quantitative changes of the NLFs ······· 22

4. Clinical visual changes of NLFs after orthodontic treatment – GAIS ········ 26

IV. DISCUSSION ········································································ 29

ii

V. CONCLUSION ······································································· 33

VI. REFERENCES ······································································ 34

ABSTRACT (KOREAN) ······························································· 41

iii

LEGEND OF FIGURES

Figure 1. Landmarks and definitions of linear measurements ·································· 5

Figure 2. Precise landmark positioning with three-dimensional volume rendering images

and multiplanar reconstructed images ················································· 8

Figure 3. Pre and post-treatment Image templetes used for the modified Global Aesthetic

Improvement Scale (GAIS) ···························································· 10

Figure 4. Representative pre and post-treatment images indicating the changes of the

nasolabial folds using modified GAIS ················································ 26

Figure 5. An example of superimposed axial cross sectional image at NLF 2 level of

retraction group ·········································································· 30

iv

LEGEND OF TABLES

Table 1. Definitions of landmarks ·································································· 6

Table 2. Definitions of linear and angular measurements ······································ 7

Table 3. Initial characteristics of the subjects ···················································· 13

Table 4. Three-dimensional hard tissue changes of point measurements (mm) in female ··· 15

Table 5. Three-dimensional hard tissue changes of point measurements (mm) in male ····· 16

Table 6. Three-dimensional soft tissue changes of point measurements (mm) in female ···· 18

Table 7. Changes of soft tissue linear and angular measurements (mm) in female ········· 19

Table 8. Three-dimensional soft tissue changes of point measurements (mm) in male ···· 20

Table 9. Changes of soft tissue linear and angular measurements (mm) in male ··········· 21

Table 10. Differences of treatment factors and host factors between the control group and

retraction group according to age group in each gender ··························· 23

Table 11. Correlations between quantitative posterior changes of nasolabial folds and

changes of hard and soft tissue (mm, Pearson correlation tests) ·················· 25

Table 12. Differences of averaged GAIS scores and distribution of GAIS scores between

the control group and retraction group according to age group in each gender ····· 28

v

Abstract

Three-dimensional changes of the nasolabial fold

and the perioral soft tissue following

orthodontic retraction of lip protrusion

Eui Seon Baek

The Graduate School Yonsei University

Department of Dentistry

(Directed by associate prof. Chooryung J. Chung, D.D.S., Ph.D.)

The objective of this study was to evaluate the quantitative and perceived visual changes of

the nasolabial fold (NLF) after maximum retraction in adults and to determine its contributing

factors.

52 adults’ CBCTs were retrospectively collected and divided into the retraction group (age

26.2±8.26 years) that underwent maximum retraction following 4 premolar extraction and the

control group (age 23.5±4.84 years) of subjects that underwent non-extraction treatment with

minor changes of the incisors. Three-dimensional morphologic changes of hard and soft tissue

including NLF were measured by pre and post-treatment CBCTs. Clinical visual change of the

NLF was monitored using the modified Global Aesthetic Improvement Scale (GAIS). The

influence of gender, age, and initial severity of NLF was evaluated.

vi

Anterior retraction induced significant three-dimensional movement of the facial soft tissue

including the lips, perioral, paranasal and the NLF compared to the control (p<0.01). Perceived

visual changes of the NLFs was noted only in females under the age of 30 (p<0.05). For females

under the age of 30, the odds ratio (95% CI) was 2.44 (1.3461-4.4226) indicating greater

possibility for improvement of NLF esthetics in young females of the retraction group compared to

the control group.

Orthodontic retraction induced quantitative and perceived changes of the NLFs. For young

adult females under the age of 30, the appearance of the NLFs significantly improved after

maximum retraction, despite the greater posterior change of the NLFs.

Key words: Nasolabial folds, Soft tissue, Orthodontic retraction, Lip protrusion, CBCT

- 1 -

Three-dimensional changes of the nasolabial fold

and the perioral soft tissue following

orthodontic retraction of lip protrusion

Eui Seon Baek

The Graduate School Yonsei University

Department of Dentistry

(Directed by associate prof. Chooryung J. Chung, D.D.S., Ph.D.)

I. Introduction

Improvement of facial esthetics as well as occlusion has long been one of the most important

treatment objectives in adult orthodontics.1 Thus, the soft tissue changes following various

orthodontic and/or orthopedic treatment has been intensively monitored through conventional

cephalometric analysis2,3 and digital imaging4 combined with three-dimensional (3D) evaluation5,6

with the aim of proper diagnosis and prediction of ideal treatment outcome7.

For malocclusions diagnosed as bimaxillary or bialveolar protrusion, premolar extraction

followed by maximum retraction of the anterior teeth is commonly accepted as a necessary

treatment modality regardless of the relatively ideal occlusion per se,8,9 since orthodontic retraction

induces dramatic hard and soft tissue changes improving the overall facial esthetics.10-12 Following

- 2 -

orthodontic retraction, evident soft tissue changes are induced in the midsagittal perioral regions

such as the lips and the nose, but considerable amounts of soft tissue changes are also extended to

the parasagittal regions of the middle and lower 1/3 of the face such as the cheilion and the

nasolabial folds (NLFs).13,14 However, large amounts of anterior retraction in adults may result in

excessive thinning of lips and increase of prolabium,15,16 some of which resembles the

unfavorable soft tissue changes of aging.17

Together with the changes in the lips, the presence of facial folds such as the NLFs are

important factors influencing the youthful appearance. NLFs run from each side of the nose to the

corners of the mouth and separate cheeks from the upper lip. NLFs originate from sagging of the

skin, prominence of buccal fat pad, muscle function and changes in the underlying bone structure

in conjuction with the anatomical and histological features.18 Morphological or volumetric changes

in the NLFs are considered as the earliest and distinctive signs of facial aging,19 but for the young

population, thick cheek fat pad may relatively cause the NLFs to exhibit a concave appearance as

well.18 Out of these complicated structural features along with the limited nature of quantitative

methods to measure the changes in soft tissue, only a few studies have reported for objective

quantification of NLFs. 20,21

Given that orthodontic retraction induces overall dimensional changes of the perioral soft

tissue, the morphological and esthetic changes of the NLFs are also suspected as well. However,

both objective and subjective information regarding these changes in the NLFs are limited in the

literature. Thus, the objective of this study was to quantify morphologic and perceived changes of

the NLFs after maximum retraction in adults and to determine the contributing factors that may

influence the changes of the NLFs.

- 3 -

II. Material and methods

1. Subjects

This study was approved by the Institutional Review Board. The study population consisted

of 52 Korean adults (≥18 years) treated with fixed appliances in the Department of Orthodontics,

Gangnam Severance Hospital, Yonsei University. The subjects who had pre and post-treatment

cone beam computed tomography (CBCT) images were retrospectively collected and divided into

retraction group (N=26, 4 men and 22 women, range of 18-45 years old, 26.2±8.26 years) who

underwent maximum retraction following 4 premolar extraction and control group (N=26, 9 men

and 17 women, range of 18-36 years old, 23.5±4.84 years) who underwent non-extraction

treatment with minor changes of the incisors. The inclusion criteria for the retraction group were;

Skeletal Class I to mild Skeletal Class II relationship (0°<ANB angle<6.0°), diagnosed as

bialveolar protrusion, treated following extraction of 4 premolars, finished in Class I molar and

canine relationship under maximum retraction with over 4 mm of anterior-posterior changes of the

upper and lower incisor tip when superimposed to the anterior cranial base using CBCT.22 The

inclusion criteria for the control group were; Skeletal Class I to mild Class II relationship

(0°<ANB angle<6.0°), mild crowding (arch length discrepancy <4mm) or within normal range of

lip against Ricketts’ E-line treated non-extraction, finished in Class I molar and canine relationship

with less than 1.5mm of anterior-posterior changes of the upper and lower incisor tip when

superimposed to the anterior cranial base. Patients with facial asymmetry ( >2 mm of Me’

deviation from the midsagittal reference line), deformity, previous plastic surgery, previously

injected dermal filler or botulinum toxin and distorted CBCT images were excluded.

- 4 -

2. Data Acquisition

Pre and post-treatment CBCT scans were taken using a Pax Zenith 3D (Vatech, Seoul, Korea).

Both scans were taken by an experienced radiological technologist. The patients were instructed to

stand straight in maximum intercuspal position with light contact of the lips and face relaxed. A

scan captured 632 images, with exposure parameters of 105 kV and 5.4 mAs, acquired for 24

seconds, with a voxel size of 0.3 mm and FOV (field of view) of 24 x 19 cm encompassing the

face, jaws, and entire cranial base. The obtained DICOM data were reconstructed into 3D images

using OnDemand 3D software (Cybermed Co., Seoul, Korea). The pre and post-treatment CBCT

data were superimposed by automatic voxel-by-voxel registration on stable structures in the

anterior cranial base, using the OnDemand3DTM fusion module. After approximate manual

registration, automatic registration was performed by computer which compares the gray level

intensity of each voxel in the anterior cranial base area.23,24 The superimposed images were reliable

for landmark positioning and measurements on the same reference plane.14,25

3. Coordinate system and landmarks

On the superimposed 3D CBCT images, the horizontal reference plane was established

parallel to the Frankfort plane (FH plane), which was constructed using both porion and left side

orbitale, while passing through nasion (N). The midsagittal vertical reference plane was set

according to the plane perpendicular to the FH plane and passing through the N and basion.26 The

coronal vertical reference plane was set perpendicular to the horizontal and midsagittal vertical

planes and passing through N. A cartesian coordinate system was used with N as the origin of

coordination system (0, 0, and 0) throughout the x-y, x-z, and y-z planes to represent the axial (IS),

- 5 -

coronal (LR), and sagittal planes (AP), respectively. Positive coordinate values were indicated by

values to the left, posterior, and superior to the origin. Landmarks, length and angle measurements

were defined as Table 1 and Table 2 using 3D cephalometric definitions (Fig 1).27-29

Figure 1. Landmarks and definitions of linear measurements.

A and B, Point landmarks and measurements; C, Comparison of landmarks on the superimposed CBCT

images. Red, pretreatment; green, post-treatment.

- 6 -

Table 1. Definitions of landmarks

Landmark Abbreviation Definition

Skeletal A-point A The point of maximum concavity in the midline of the alveolar process of the maxilla

B-point B The point of maximum concavity in the midline of the alveolar process of the mandible

Pogonion Pog The most anterior midpoint of the chin on the outline of the mandibular symphysis

Menton Me The most inferior midpoint of the chin on the outline of the mandibular symphysis

Dental Upper incisor incisal tip* Isi* The midpoint of the tip of the crown of each upper central incisor

Upper incisal root apex* Isa* The tip of the root apex of each upper central incisor

Lower incisor incisal tip* Iii* The midpoint of the tip of the crown of each lower central incisor

Lower incisal root apex* Iia* The tip of the root apex of each lower central incisor

Perioral

Soft tissue

Soft tissue A-point A' The most anterior concave point between subnasale and the anterior point of the upper lip

Labiale superius Ls The most anterior midpoint of the vermilion line of the upper lip

Upper lip point ULP The most anterior midpoint of upper lip

Stomion superius STMs The midpoint of the lower border of the upper lip

Stomion Inferius STMi The midpoint of the upper border of the lower lip

Lower lip point LLP The most anterior midpoint of lower lip

Labiale Inferius Li The most anterior midpoint of the vermilion line of the lower lip

Soft tissue B-point B' The most posterior midpoint on the labiomental soft tissue contour that defines the border between the lower lip and the chin

Soft tissue pogonion Pog' The most anterior midpoint of the chin

Soft tissue Menton Me' The most inferior midpoint on the soft tissue contour of the chin, located at vertical projection from menton on the soft tissue

Christa philitri* Cph* The point at each crossing of the vermilion line and the elevated margin of the philtrum

Cheilion* Ch* The point located at each labial comissure at the most lateral intersection of upper and lower lip

Nasolabial fold 1* NLF1* The deepest point on nasolabial fold at at horizontal level of initial Subnasale

Nasolabial fold 2* NLF2* The deepest point on nasolabial fold at horizontal level of 15mm below initial subnasale

Nasal

soft tissue

Pronasale Pn The most anterior midpoint of the nasal tip

Columella Cm The midpoint of the columella crest at the level of the nostril top points

Subnasale Sn The midpoint on the nasolabial soft tissue contour between the columella crest and the upper lip

Alar curvature AC* The most lateral point in the curved base line of each ala, indicating the facial insertion of the nasal wingbase

Subalare* Sa* The point at the lower limit of each alar base, where the alar base disappears into the skin of upper lip

Midfacial

soft tissue

Cheek* Ck* The point at intersection of vertical projection from primary exocanthion and horizontal projection from primary alarcurvature

Soft tissue nasion N' The midpoint on the soft tissue contour of the base of the nasal root at the level of the frontonasal suture

*Left and right landmarks used.

- 7 -

Table 2. Definitions of linear and angular measurements

Measurment Definition

Perioral

soft tissue

Basic upper lip thickness (mm) Linear distance from3mm below A-point to subnasale

Upper lip thickness (mm) Linear distance from the most prominent labial point of the maxillary incisor to labrale superius (Ls)

Upper lip strain (mm) The difference between basic upper lip thickness and upper lip thickness

Upper lip length (Sn-STMs,∆y,mm) Vertical distance from subnasale to stomion superius perpendicular to the Frankfort horizontal plane (FH plane)

Prolabium (Sn-Ls,∆y,mm) Vertical distance from subnasale to labialis superius perpendicular to the Frankfort horizontal plane (FH plane)

Upper vermilion height

(Ls-STMs,∆y,mm) Vertical distance from labialis superius to stomion superius perpendicular to the Frankfort horizontal plane (FH plane)

Basic lower lip thickness (mm) Linear distance from B-point to the deepest point of the labiomental fold

Lower lip thickness (mm) Linear distance from the most prominent labial point of the mandibular incisor to labrale inferius (Li)

Lower vermilion height

(Li-STMi,∆y,mm) Vertical distance from labialis inferius to stomion inferius perpendicular to the Frankfort horizontal plane (FH plane)

Mouth width (Ch-Ch,∆x,mm) Horizontal distance between right and left Cheilion parallel to the Frankfort horizontal plane (FH plane)

Chin thickness-H (mm) Linear distance from pogonion to its sagittal projection on the soft tissue (Pog-Pog')

Chin thickness-V (mm) Linear distance from menton to its vertical projection on the soft tissue (Me-Meʹ)

Nasal

soft tissue Alar width (AC-AC,∆x,mm) Horizontal distance between right and left alar curvature parallel to the Frankfort horizontal plane (FH plane)

Alar base width (Sa-Sa,∆x,mm) Horizontal distance between right and left Subalare parallel to the Frankfort horizontal plane (FH plane)

Nasolabial angle(°) Angle formed by intersection of Cm-Sn line and Ls-Sn line

- 8 -

Landmark positioning and measurements were performed basically on 3D volume rendering

soft tissue surface images. Subsequently multiplanar (axial, coronal and sagittal) adjustment was

performed on reconstructed two dimensional cross sectional images. All landmarks were verified

on the 360° view of the 3D soft tissue surface representation including lateral profile views, three-

quarter views, submental view and base view. Additional adjustment was performed in the axial,

coronal and sagittal cross sectional reconstructed images to enhance reliability in landmark

positioning. In sequence, additional precise calibration on the x-z plane was performed to

minimize errors along x- and z-axes for all landmarks in the superimposed CBCT surface images

displaying landmarks of pre and post-treatment simultaneously (Fig 2).

Figure 2. Precise landmark positioning with three-dimensional volume rendering images and

multiplanar reconstructed images.

A, Arbitrary positioning of NLF1 (X) on the 3D volume rendered image on soft tissue surface along the left

NLF at initial subnasale level; B, Adjusting on axial reconstructed plane; C, Adjusting on coronal

reconstructed plane; D, Adjusting on sagittal reconstructed plan; E; Final precise calibration was performed

on the superimposed CBCT surface images displaying pre and post-treatment landmarks simultaneously; Red,

preretment; green, post-treatment.

- 9 -

Basic upper lip thickness was selected to represent the individual’s initial soft tissue thickness

because underlying subnasale (Sn) reportedly is the most stable landmark on the midsagittal plane

throughout the aging process,30 while cheek landmarks (Ck) were set to represent the thickness of

the soft tissue lateral to the NLFs, as the cheek typically represents subcutaneous fat thickness.31

To measure quantitative changes of NLFs area, total of four landmarks both on the deepest

point of the left and the right sides were defined along NLFs at the pretreatment Sn level (NLF1)

and 15mm vertically downward from pretreatment Sn level (NLF2). Considering vertical

positional change of Sn between pre and post-treatment, NLF1 and NLF2 on post treatment image

were calibrated on the x-z plane to the same vertical level of pretreatment in the superimposed

image. Vectors and amounts were determined at each landmark between the pre and post-treatment,

representing changes between time points. In bilateral landmarks, each vectors and amounts were

averaged between the right and the left.

4. Clinical assessments of the NLFs

To categorize the initial condition of the NLF, Winkle Severity Rating Scale (WSRS), a

specific scale for quantifying facial folds,32 was applied by looking at the initial CBCT soft

tissue images by one investigator. Scoring of fold severity is based on visual assessment of the

length and apparent depth of the NLF without reference to baseline. Conventionally, WSRS uses

a five point scale: 1= absent, no visible NLF; 2= mild, shallow but visible NLF with a slight

indentation with minor facial feature; 3= moderate, moderately deep NLF with clear facial

feature visible at normal appearance but not when stretched; 4= severe, very long and deep NLF

with prominent facial feature and <2mm visible fold when stretched; 5= extreme, extremely

deep and long NLF detrimental to facial appearance and 2–4mm visible V-shaped fold when

stretched.32

- 10 -

Clinical visual change of the NLF was evaluated using the modified Global Aesthetic

Improvement Scale (GAIS), a reproducible grading system based on visual subjective assessment

of the length and apparent depth of the fold,33,34 by six experienced specialists; two dermatologists,

one plastic surgeon, three orthodontists, with > 7 years of clinical experience. For the evaluation

template, a pair of pre and post-treatment reconstructed soft tissue surface CBCT images below the

eyes for each subject were presented on one slide, representing either frontal or three-quarter views

from the left side (Fig 3).

Figure 3. Pre and post-treatment Image templetes used for the modified Global Aesthetic

Improvement Scale (GAIS).

Total of 124 sets of pre and post-treatment CBCT reconstructed soft tissue surface image slides (52 sets of

frontal views, 52 sets of three-quarter views and additional 20 duplicated sets to evaluate intra-observer

consistency) were presented to the investigators in random order.

- 11 -

The modified GAIS uses a three-point scale: 1= improved, obvious improvement in appearance

from the initial condition; 0 = no change, the appearance is essentially the same as the initial

condition; -1 = worsen, the appearance is worse than the initial condition. A total of 124 templates

(52 sets of frontal views, 52 sets of three-quarter views and additional 20 duplicated sets to evaluate

intra-observer consistency) were presented to the investigators in random order of subjects from both

the retraction and control groups. Assessments were conducted independently and the investigators

were not informed of the treatment regime. GAIS scores drawn by 6 specialists for both the frontal

and the three-quarter view per subject were averaged for statistical evaluation.

5. Statistical Analysis

To validate the reliability of landmark positioning, the measurements were repeated for 10

randomly selected CBCT data by the same operator at 2-week intervals. Intraclass correlation

coefficients (ICCs) and Dahlberg’s method error for each landmark in all 3 axes (x, y and z) were

assessed to test intra-observer reliability. Averaged ICCs were > 0.94 in all landmarks. The

Dahlberg’s method errors were < 1mm (range of 0.20-0.94), which is considered clinically

acceptable.35

To assess intra-observer reliability of the WSRS scores, ICC was used. ICC for intra-observer

reliability of the WSRS was 0.96. To assess intra-observer reliability of the GAIS for each

investigator, weighted kappa coefficient as well as the mean and 95% confidence interval (CI) was

estimated. Weighted kappa coefficients for intra-observer consistency ranged from 0.36 to 0.71

(mean 0.65, 95% CI 0.53–0.78), which indicates fair to good agreements. The sample size was

calculated with a power of 80%.36

The differences of displacement vectors and amounts between pre and post-treatment were

analyzed by means of a paired t-test. The comparisons between the control and retraction group

- 12 -

were performed using independent two sample t-test. To determine age and gender effect to the

changes of NLFs, independent t-test and chi-square test was used. To identify correlations among

quantitative changes of NLFs, Pearson’s correlation was analyzed. Generalized estimating

equations were used to compare distribution of GAIS score and odds ratio was calculated. All of

the measurements were statistically calculated using SAS version 9.3(SAS Institute, Cary, NC,

USA) and SPSS version 23(SPSS institute, Chicago, IL, USA).

- 13 -

III. Results

1. Initial soft and hard tissue characteristics

The overall features of facial profiles were similar between females and males within the

control and retraction groups. However, males tended to indicate thicker perioral soft tissue

compared to females, and this was significant within the control group (p<0.001). Considering that

intrinsic factors such as gender and soft tissue volume affect the overall changes of the facial soft

tissue,30,37-39 the measurements were divided based on gender for further evaluation (Table 3).

Table 3. Initial characteristics of the subjects

Control group (Mean±SD)

(N=31)

Retraction group (Mean±SD)

(N=32)

Female (n=17)

(Mean±SD)

Male (n=9)

(Mean±SD) P value

Female (n=22)

(Mean±SD)

Male (n=4)

(Mean±SD) P value

ANB (°) 2.5±1.81 2.0±1.60 NS 3.5±1.72 2.6±1.54 NS

U1 to A-Pog (mm) 6.8±2.12 7.6±2.63 NS 12.3±1.79 11.8±1.83 NS

L1 to A-Pog (mm) 4.5±2.33 4.0±1.99 NS 7.9±1.86 8.9±1.69 NS

U1 to SN (°) 103.4±7.86 105.5±5.66 NS 111.3±5.59 104.3±6.04 0.031

IMPA (°) 91.1±10.40 88.3±7.37 NS 96.4±7.19 92.8±4.47 NS

Upper lip to E-line (mm) -1.9±0.94 -0.7±1.64 NS 0.8±1.47 1.4±0.58 NS

Lower lip to E-line (mm) -0.3±2.08 1.3±2.09 NS 2.8±1.68 4.1±1.57 NS

Basic upperlip thickness (mm) 13.1±1.52 16.5±1.64 <0.001 15.6±1.99 17.5±1.59 NS

Upper lip thickness (mm) 12.0±1.15 14.9±1.00 <0.001 11.0±1.81 12.9±2.06 NS

Lower lip thickness (mm) 12.3±0.83 15.30±1.38 <0.001 12.4±1.84 13.2±1.07 NS

Treatment duration (months) 23.6±7.78 16.0±8.69 0.032 32.0±6.49 30.8±6.89 NS

U1, upper incisal tip; A-Pog, A-point to pogonion line; L1, lower incisal tip; SN, sella-nasion line; IMPA, lower incisor

mandibular plane angle; E-line, Ricketts’ E-line; ANB, A-point-Nasion-B-point angle; WSRS, Wrinkle Severity Rating Scale;

SD, standard deviation; NS indicates P >0.05.

- 14 -

2. Three-dimensional changes in the facial soft tissue and the NLFs following

anterior retraction

Large amounts of changes in Isi and Iii in the AP axis were noted in the retraction group

(6.4±0.57 and 5.4±1.73 mm for females and 5.4±1.36 and 5.6±1.65 mm for males), while these

changes were not noted in the control group (p<0.001). Hard tissue landmarks, A, B, Pog and Me

did not show significant changes after treatment in both control and retraction groups (Table 4 and

Table 5).

- 15 -

Table 4. Three-dimensional hard tissue changes of point measurements (mm) in female

∆x ∆y ∆z

Landmark

Control group

(N=17)

Retraction group

(N=22)

p-value†

Control group

(N=17)

Retraction group

(N=22)

p-value†

Control group

(N=17)

Retraction

group

(N=22) p-value†

(Mean±SD) (Mean±SD) (Mean±SD) (Mean±SD) (Mean±SD) (Mean±SD)

Skeletal

A 0.0±0.10 -0.1±0.47 NS 0.0±0.27 -0.1±0.66 NS 0.5±0.95 0.98±1.25 NS

B -0.2±0.69 0.1±0.32 NS 0.0±0.67 -0.5±1.33 NS -0.6±1.14 -0.7±3.10 NS

Pog 0.0±0.25 0.0±0.32 NS 0.3±0.68 -0.1±1.31 NS -0.1±0.80 0.0±1.28 NS

Me 0.0±0.01 0.3±0.88 NS 0.2±0.76 -0.2±1.43 NS 0.2±0.86 0.1±0.80 NS

Dental

Isi 0.1±0.68 -0.5±0.76 0.009 0.1±0.88 -6.4±0.57 <0.001 0.4±0.20 0.4±0.89 NS

Isa -0.2±0.49 -0.6±1.31 NS 0.0±1.03 -2.2±1.41 <0.001 0.4±0.03 -0.4±2.71 NS

Iii -0.3±0.67 -0.4±1.95 NS -0.5±0.92 -5.4±1.73 <0.001 -0.3±1.24 -0.5±1.31 NS

Iia -0.1±0.59 -0.2±1.10 NS -2-0.3±0.95 -2.5±1.02 <0.001 -1.1±0.91 -0.2±1.34 0.031

A, A-point; B, B-point; Pog, pogonion; Me, menton; Isi, upper incisor incisal tip; Isa, upper incisor root apex; Iii, lower incisor incisal tip; Iia, lower incisor root apex; p-value†,

Independent two sample t-test between control group and retraction group; NS indicates P >0.05.

- 16 -

Table 5. Three-dimensional hard tissue changes of point measurements (mm) in male

∆x ∆y ∆z

Landmark

Control group

(N=17)

Retraction group

(N=22)

p-value†

Control group

(N=17)

Retraction group

(N=22)

p-value†

Control group

(N=17)

Retraction

group

(N=22) p-value†

(Mean±SD) (Mean±SD) (Mean±SD) (Mean±SD) (Mean±SD) (Mean±SD)

Skeletal

A 0.0±0.01 0.0±0.09 NS -0.1±1.50 0.1±0.34 NS 0.2±1.51 1.6±2.85 NS

B -0.1±0.44 0.1±1.98 NS -0.7±0.95 -0.3±1.03 NS 0.9±2.24 1.0±2.55 NS

Pog 0.1±0.43 0.0±0.0 NS -0.7±0.81 -0.3±1.29 NS 0.8±0.79 -0.2±0.99 NS

Me 0.0±0.05 0.0±0.0 NS -0.6±1.18 0.5±0.55 NS 0.5±0.83 -0.1±0.43 NS

Dental

Isi -0.1±0.83 -0.5±0.96 NS 0.3±1.33 -5.4±1.36 <0.001 0.0±0.64 -0.9±2.07 NS

Isa -0.3±0.66 -0.6±1.34 NS -0.6±0.68 -2.3±1.48 NS 1.1±0.87 -0.5±2.76 NS

Iii -0.3±0.53 -0.5±1.89 NS 0.2±1.27 -5.6±1.65 <0.001 -0.1±1.23 -0.82±1.47 0.006

Iia 0.1±0.49 -0.3±1.20 NS 0.0±0.47 -2.4±1.07 NS 0.8±5.12 -0.3±1.31 NS

A, A-point; B, B-point; Pog, pogonion; Me, menton; Isi, upper incisor incisal tip; Isa, upper incisor root apex; Iii, lower incisor incisal tip; Iia, lower incisor root apex; p-value†,

Independent two sample t-test between control group and retraction group; NS indicates P >0.05.

- 17 -

Similar to the overall changes of the teeth, significant changes in the soft tissue landmarks

were noted in the AP axis and the IS axis only in the retraction group. For females, A’ moved

posteriorly and downward, B’ moved posteriorly and upward and Pog’ moved posteriorly only in

the retraction group and not in the control group (p<0.05). Landmarks representing lip soft tissue

(ULP, LLP and Ch) and the paranasal region (Sn and Sa) moved posteriorly only in the retraction

group and not in the control group (p<0.01).

Vertical changes (IS axis) were more prominent in the landmarks representing medial soft

tissue in the nasal (Pn, Cm, Sn and Sa) (p<0.01), perioral ( A’ and B’) (p<0.05), and lip area (Cph,

Ls, ULP and Li) (p<0.01) than parasagittal soft tissue such as the Ch and AC, which showed no

significant vertical changes in both groups. Upper lip vermilion border (Ls and Cph) and ULP

moved downward, while Li moved upward only in the retraction group and not in the control

group (p<0.01). The length of prolabium significantly increased by 1.0±1.2mm, while upper and

lower vermilion height significantly decreased by 1.3±0.94 and 1.6±1.20mm, respectively only in

the retraction group (p<0.01). Consistent basic upper lip thickness and decrease of upper lip

thickness resulted in decrease of upper lip strain by 2.0±1.31mm only in the retraction group as

well (p<0.001).

NLF1 and NLF2, indicated posterior movement only in the retraction group by 0.8±0.66 and

1.2±0.78mm, respectively, which was significantly different compared to control group (p<0.001)

(Table 6 and Table 7).

Although the overall changes were similar in males in the retraction group, significant

changes in the paranasal soft tissue and vertical changes in the upper lip, such as lengthening of

prolabium and decrease of upper vermilion height were not noted in males unlike females. In

males, posterior movement of NLF1 and NLF2 in the retraction group was not significant

compared to the control group. (Table 8 and Table 9).

- 18 -

Table 6. Three-dimensional soft tissue changes of point measurements (mm) in female

Control group (N=17) Retraction group (N=22) Comparison

Landmark

∆x p-value

†

∆y p-value

†

∆z p-value

†

∆x p-value

†

∆y p-value

†

∆z p-value

†

∆x ∆y ∆z

(Mean±SD) (Mean±SD) (Mean±SD) (Mean±SD) (Mean±SD) (Mean±SD) p-value‡ p-value‡ p-value‡

Midfacial

soft tissue

Ck 0.0±0.20 NS 0.3±1.09 NS 0.0±0.20 NS 0.0±0.25 NS -0.4±1.11 NS 0.0±0.19 NS NS NS NS

N' 0.0±0.12 NS 0.2±0.60 NS 0.0±0.23 NS 0.0±0.02 NS 0.0±0.66 NS 0.0±0.27 NS NS NS NS

Nasal

soft tissue

Pn 0.0±0.29 NS 0.1±0.58 NS 0.0±0.49 NS 0.0±0.33 NS -0.1±0.60 NS 0.9±0.71 <0.001 NS NS <0.001

Cm 0.0±0.60 NS 0.2±0.95 NS 0.2±0.61 NS -0.2±0.32 0.015 -0.1±0.62 NS 0.8±0.67 <0.001 NS NS 0.003

Sn 0.0±0.35 NS 0.0±0.62 NS 0.1±0.68 NS -0.1±0.40 NS -0.6±0.71 0.001 0.8±0.66 <0.001 NS 0.014 0.004

AC 0.0±0.27 NS -0.1±0.63 NS 0.3±0.57 NS 0.0±0.26 NS -0.4±0.71 0.026 0.2±0.82 NS NS NS NS

Sa -0.1±0.45 NS 0.2±0.69 NS 0.1±0.37 NS 0.0±0.49 NS -0.8±0.55 <0.001 0.7±0.71 <0.001 NS <0.001 0.002

Perioral

soft tissue

A' 0.0±0.44 NS 0.1±0.81 NS 0.1±0.60 NS -0.2±0.85 NS -2.4±0.94 <0.001 1.4±0.94 <0.001 NS <0.001 <0.001

B' 0.0±0.09 NS 0.7±3.4 NS -0.3±1.51 NS 0.1±0.69 NS -2.4±1.82 <0.001 -1.7±1.75 <0.001 NS 0.001 0.013

Pog' 0.0±0.53 NS 0.0±1.16 NS 0.6±2.36 NS -0.3±1.12 NS -1.0±1.77 0.011 1.1±3.32 NS NS 0.037 NS

Me' -0.1±0.32 NS 0.0±1.17 NS 0.0±1.23 NS 0.7±3.81 NS 0.0±1.44 NS 0.1±0.90 NS NS NS NS

Lip

Cph 0.2±0.92 NS 0.0±0.93 NS 0.2±0.62 NS -0.1±0.79 NS -2.4±0.94 <0.001 1.9±0.85 <0.001 NS <0.001 <0.001

Ls 0.1±0.63 NS 0.2±0.91 NS 0.1±0.72 NS -0.2±0.56 NS -2.7±1.20 <0.001 1.9±1.09 <0.001 NS <0.001 <0.001

ULP 0.0±0.91 NS 0.2±0.83 NS 0.2±0.58 NS -0.1±0.70 NS -2.7±1.22 <0.001 1.68±1.17 <0.001 NS <0.001 <0.001

STMs -0.1±0.22 NS 0.5±0.95 NS -0.1±0.87 NS -0.3±0.87 NS -3.8±1.37 <0.001 0.5±0.96 0.017 NS <0.001 NS

STMi -0.1±0.75 NS 0.25±1.34 NS -0.1±0.75 NS -0.3±0.71 NS -3.8±1.59 <0.001 0.3±0.87 NS NS <0.001 NS

LLP -0.1±0.79 NS 0.0±1.06 NS -0.2±0.81 NS -0.1±0.61 NS -4.3±1.41 <0.001 -0.3±1.59 NS NS <0.001 NS

Li -0.1±0.63 NS -0.2±1.06 NS 0.1±0.76 NS 0.1±0.48 NS -3.9±1.29 <0.001 -1.3±1.61 0.001 NS <0.001 0.002

Ch 0.1±0.48 NS 0.1±1.35 NS 0.1±0.42 NS 0.0±0.93 NS -4.1±1.71 <0.001 0.5±1.48 NS NS <0.001 NS

Nasolabial

folds

NLF1 0.1±0.39 NS 0.1±0.63 NS 0.1±0.42 NS 0.1±0.55 NS -0.8±0.66 <0.001 0.2±0.26 0.008 NS <0.001 NS

NLF2 -0.3±0.55 NS 0.3±0.78 NS 0.1±0.29 NS 0.0±0.42 NS -1.2±0.78 <0.001 0.0±0.23 NS NS <0.001 NS

Ck, cheek; N', soft tissue nasion; Pn, pronasale; Cm, columella; Sn, subnasale; AC, alar curvature; Sa, subalare; A', soft tissue A-point; B', soft tissue B-point; Pog', soft tissue

pogonion; Me', soft tissue menton; Cph, christa philtri; Ls, labialis superius; ULP, upper lip point; STMs, stomion superius; STMi, stomion inferius; LLP, lower lip point; Li,

labialis inferius; Ch, cheilion; NLF, nasolabial fold; p-value†, Paired t-test; p-value‡, Independent two sample t-test between control group and retraction group; SD, standard

deviation; NS indicates P >0.05.

- 19 -

Table 7. Changes of soft tissue linear and angular measurements (mm) in female

measurment

Control group

(N=17) Retraction group (N=22) Comparison

Diff

p-value†

Diff

p-value†

Diff

p-value‡

(Mean±SD) (Mean±SD) (Mean±SD)

Nasal

soft tissue

Alar width -0.7±1.19 0.026 -0.7±1.11 0.006 0.0±0.37 NS

Alar base width -0.4±1.58 NS -0.1±1.18 NS -0.3±0.44 NS

Nasolabial angle (°) 1.6±3.47 NS -8.3±5.42 <0.001 9.9±1.43 <0.001

Perioral

soft tissue

Chin thickness-H -0.4±0.84 0.047 0.0±0.87 NS -0.4±0.28 NS

Chin thickness-V 0.0±1.02 NS 0.1±0.97 NS -0.1±0.32 NS

Lip

Basic upperlip thickness 0.1±0.53 NS 0.1±1.18 NS -0.1±0.28 NS

Upper lip thickness 0.3±0.98 NS -1.9±1.20 <0.001 2.2±0.36 <0.001

Upper lip strain -0.2±1.11 NS 2.0±1.31 <0.001 -2.2±0.40 <0.001

Upper lip length 0.1±1.04 NS 0.2±0.89 NS -0.1±0.31 NS

Prolabium 0.0±1.02 NS -1.0±1.21 0.001 1.0±0.37 0.010

Upper vermilion height 0.1±1.03 NS 1.3±0.94 <0.001 -1.1±0.32 0.001

Basic lower lip thickness 0.2±1.10 NS 1.1±1.71 0.007 -0.9±0.45 NS

Lower lip thickness -0.2±1.11 NS -0.4±0.86 NS 0.1±0.33 NS

Lower vermilion height -0.1±0.49 NS 1.6±1.20 <0.001 -1.7±0.31 <0.001

Mouth width -0.5±1.55 NS -0.4±2.40 NS -0.1±0.64 NS

Nasolabial

folds

NLF1 width 0.1±0.76 NS 0.5±1.48 NS -0.4±0.39 NS

NLF2 width 0.0±0.61 NS 0.6±1.37 NS -0.6±0.33 NS

NLF, nasolabial fold; p-value†, Paired t-test; p-value‡, Independent two sample t-test between control group and retraction

group; Diff., difference between control group and retraction group; SD, standard deviation; NS indicates P >0.05.

- 20 -

Table 8. Three-dimensional soft tissue changes of point measurements (mm) in male

Control group (N=17) Retraction group (N=22) Comparison

Landmark

∆x p-value

†

∆y p-value

†

∆z p-value

†

∆x p-value

†

∆y p-value

†

∆z p-value

†

∆x ∆y ∆z

(Mean±SD) (Mean±SD) (Mean±SD) (Mean±SD) (Mean±SD) (Mean±SD) p-value‡ p-value‡ p-value‡

Midfacial

soft tissue

Ck 0.0±0.18 NS -0.2±0.94 NS 0.0±0.21 NS 0.0±0.23 NS -0.2±1.23 NS 0.0±0.18 NS NS NS NS

N' 0.0±0.25 NS 0.1±0.71 NS 0.0±0.38 NS 0.0±0.01 NS 0.1±0.61 NS 0.0±0.26 NS NS NS NS

Nasal

soft tissue

Pn 0.0±0.27 NS -0.2±0.59 NS 0.3±0.622 NS 0.0±0.30 NS -0.1±0.57 NS 0.7±0.80 <0.001 NS NS NS

Cm 0.0±0.38 NS 0.0±0.74 NS 0.6±0.59 NS -0.1±0.36 NS -0.1±0.63 NS 0.8±0.67 <0.001 NS NS NS

Sn 0.0±0.63 NS -0.2±0.45 NS 0.4±0.61 NS -0.1±0.41 NS -0.6±0.66 <0.001 0.77±0.61 <0.001 NS NS NS

AC 0.1±0.25 NS -0.4±0.40 NS -0.2±0.47 NS -0.1±0.28 NS -0.4±0.67 NS 0.1±0.80 NS NS NS NS

Sa 0.0±0.29 NS -0.2±0.44 NS 0.2±0.50 NS 0.0±0.48 NS -0.7±0.59 <0.001 0.7±0.65 <0.001 NS NS NS

Perioral

soft tissue

A' 0.0±0.14 NS 0.0±1.12 NS 0.2±0.47 NS -0.1±0.82 NS -2.3±0.96 <0.001 1.5±0.94 <0.001 NS 0.023 <0.001

B' 0.5±1.67 NS -0.4±0.63 NS -0.2±1.50 NS 0.1±0.66 NS -2.3±1.73 <0.001 -1.8±1.65 <0.001 NS 0.014 NS

Pog' -0.4±0.76 NS -0.4±0.76 NS 0.6±1.68 NS -0.2±1.06 NS -0.7±1.86 NS 0.6±3.76 NS NS 0.038 NS

Me' 0.0±0.14 NS -0.3±1.34 NS 0.2±1.16 NS 0.6±3.51 NS 0.0±1.38 NS 0.1±0.85 NS NS NS NS

Lip

Cph -0.2±0.78 NS -0.1±1.20 NS 0.5±1.05 NS -0.1±0.74 NS -2.4±0.977 <0.001 1.7±0.94 <0.001 NS 0.009 NS

Ls -0.2±0.87 NS 0.0±1.36 NS 0.7±1.08 NS -0.1±0.59 NS -2.6±1.27 <0.001 1.8±1.03 <0.001 NS 0.025 NS

ULP -0.1±0.69 NS -0.1±1.42 NS 0.4±1.27 NS 0.0±0.68 NS -2.6±1.26 <0.001 1.5±1.15 <0.001 NS NS NS

STMs 0.0±0.0 NS 0.0±1.59 NS 0.2±1.09 NS -0.2±0.87 NS -3.6±1.51 <0.001 0.5±0.97 0.025 NS 0.031 NS

STMi 0.0±0.0 NS 0.4±1.42 NS 0.1±0.92 NS -0.2±0.73 NS -3.8±1.60 <0.001 0.2±0.88 NS NS 0.001 NS

LLP 0.0±0.63 NS 0.0±1.05 NS 0.6±1.29 NS 0.0±0.60 NS -4.3±1.36 <0.001 -0.5±1.66 NS NS <0.001 0.024

Li 0.0±0.84 NS -0.3±1.05 NS 0.4±1.27 NS 0.2±0.51 NS -3.9±1.24 <0.001 -1.3±1.58 <0.001 NS <0.001 0.035

Ch 0.1±1.14 NS -0.3±1.15 NS 0.2±0.62 NS 0.1±0.91 NS -4.0±1.61 <0.001 0.4±1.38 NS NS <0.001 NS

Nasolabial

folds

NLF1 0.0±0.32 NS -0.2±0.43 NS 0.1±0.51 NS 0.1±0.51 NS -0.7±0.64 <0.001 0.2±0.26 0.002 NS NS NS

NLF2 0.0±0.30 NS -0.2±0.67 NS 0.0±0.45 NS 0.0±0.39 NS -1.1±0.82 <0.001 0.0±0.25 NS NS NS NS

Ck, cheek; N', soft tissue nasion; Pn, pronasale; Cm, columella; Sn, subnasale; AC, alar curvature; Sa, subalare; A', soft tissue A-point; B', soft tissue B-point; Pog', soft tissue

pogonion; Me', soft tissue menton; Cph, christa philtri; Ls, labialis superius; ULP, upper lip point; STMs, stomion superius; STMi, stomion inferius; LLP, lower lip point; Li,

labialis inferius; Ch, cheilion; NLF, nasolabial fold; p-value†, Paired t-test; p-value‡, Independent two sample t-test between control group and retraction group; SD, standard

deviation; NS indicates P >0.05.

- 21 -

Table 9. Changes of soft tissue linear and angular measurements (mm) in male

measurment

Control group

(N=17) Retraction group (N=22) Comparison

Diff

p-value†

Diff

p-value†

Diff

p-value‡

(Mean±SD) (Mean±SD) (Mean±SD)

Nasal

soft tissue

Alar width 0.0±0.50 NS -0.9±1.99 NS 1.0±1.01 NS

Alar base width -0.6±1.02 NS -0.9±0.80 NS 0.3±0.58 NS

Nasolabial angle (°) 0.9±3.17 NS -7.1±7.08 NS 8.1±2.75 0.014

Perioral

soft tissue

Chin thickness-H -0.4±1.05 NS 0.0±0.77 NS -0.3±0.59 NS

Chin thickness-V -0.2±0.67 NS -0.3±0.65 NS 0.1±0.40 NS

Lip

Basic upperlip thickness 0.2±0.82 NS 0.1±0.35 NS 0.1±0.32 NS

Upper lip thickness 0.1±0.90 NS -2.5±0.43 0.001 2.7±0.48 <0.001

Upper lip strain 0.1±0.69 NS 2.6±0.16 <0.001 -2.5±0.24 <0.001

Upper lip length 0.2±1.08 NS 0.7±0.85 NS -0.6±0.62 NS

Prolabium -0.3±0.71 NS -0.7±0.58 NS 0.4±0.41 NS

Upper vermilion height 0.5±1.04 NS 1.4±0.81 0.038 -0.9±0.60 NS

Basic lower lip thickness 0.1±0.86 NS 0.3±1.83 NS -0.2±0.73 NS

Lower lip thickness -0.1±1.04 NS -1.8±0.45 0.004 1.7±0.55 0.010

Lower vermilion height -0.2±0.64 NS 1.3±0.16 NS -1.5±0.49 0.011

Mouth width -0.8±2.21 NS -0.1±1.81 NS -0.7±1.27 NS

Nasolabial

folds

NLF1 width -0.6±0.93 NS -0.2±0.59 NS -0.4±0.51 NS

NLF2 width -0.5±0.74 NS 0.0±0.77 NS -0.4±0.45 NS

NLF, nasolabial fold; p-value†, Paired t-test; p-value‡, Independent two sample t-test between control group and retraction

group; Diff., difference between control group and retraction group; SD, standard deviation; NS indicates P >0.05

- 22 -

3. Clinical factors associated with the quantitative changes of the NLFs

Intrinsic factors, such as gender39, age,38 initial soft tissue thickness,40 initial severity of NLFs

(WRSR),41 or changes of the surrounding fat pad18 may directly or indirectly influence the overall

changes of the NLFs. Accordingly, we evaluated the influences of these candidate factors along

with the quantitative changes of NLFs. Given that morphologic profile change occurs in spurts

from the second to the third decades especially in females,30 the subjects were subcategorized

according to age subgroups of under the age of 30 (< 30 yrs) and over the age of 30 (30 yrs ≤).

The initial basic upper lip thickness was significantly greater in the retraction group

compared to control group especially in females (p<0.05), but the distribution pattern of initial

WSRS score was comparable between subgroups. Following the posterior movement of anterior

teeth (Isi and Iii) and the lips (ULP, LLP and Ch), significant posterior movement of the Ck, NLF1

and NLF2 was noted in females of less than 30 yrs compared to the corresponding control group

(P<0.001). However, no significant changes were noted in Ck, NLF1 and NLF 2 for females of

equal or greater than 30 yrs and males compared to the corresponding controls (Table 10).

- 23 -

Table 10. Differences of treatment factors and host factors between the control group and retraction group according to age group in each

gender

Female Male

<30 yrs (n=28) 30 yrs ≤ (n=11) <30 yrs (n=13) 30 yrs ≤ (n=0)

Control group

(n=13)

Retraction

group

(n=15)

p-value

Control

group

(n=4)

Retraction

group

(n=7)

p-value

Control

group

(n=9)

Retraction

group

(n=4)

p-value Control

group

Retraction

group

p-

value

Basic upper lip thickness

(mm) 13.4±1.54 16.4±0.82 <0.001* 12.1±1.01 13.9±1.08 0.020* 16.5±1.64 17.5±1.59 NS*

Not available

WSRS

score

1 53.8% (7) 46.7% (7)

NS†

25.0% (1) 0.0% (0)

NS†

100% (9) 75.0% (3)

NS†

2 46.2% (6) 40.0% (6) 75% (3) 71.4% (5) 0.0% (0) 25.0% (1)

3 0.0% (0) 13.3% (2) 0.0% (0) 28.6% (2) 0.0% (0) 0.0% (0)

Total 100% (13) 100% (15) 100% (4) 100% (7) 100% (9) 100% (4)

Isi ∆y (mm) -0.1±0.85 -6.4±1.67 <0.001* 0.9±0.38 -6.5±1.46 <0.001* 0.3±1.33 -5.4±1.36 <0.001*

Iii ∆y (mm) -0.6±0.81 -5.6±1.61 <0.001* -0.2±1.32 -5.0±2.04 0.002* 0.2±1.27 -6.6±0.47 <0.001*

ULP ∆y (mm) 0.7±0.55 -2.4±1.25 <0.001* 0.7±0.41 -3.4±0.89 <0.001* 1.1±0.83 -1.9±1.41 <0.001*

LLP ∆y (mm) 0.8±0.68 -4.4±1.44 <0.001* 0.9±0.51 -4.2±1.44 <0.001* 0.9±0.46 -4.2±1.27 <0.001*

Ch ∆y (mm) 0.0±1.49 -3.8±1.80 <0.001* 0.5±0.71 -4.7±1.43 <0.001* -0.3±1.15 -3.3±0.52 <0.001*

Ck ∆y (mm) 0.4±0.13 -0.6±1.17 0.027* -0.1±0.99 0.3±0.65 NS* -0.2±0.94 0.3±1.85 NS*

NLF1 ∆y (mm) 0.1±0.69 -0.9±0.68 <0.001* 0.1±0.43 -0.5±0.52 NS* -0.2±0.44 -0.5±0.48 NS*

NLF2 ∆y (mm) 0.4±0.83 -1.4±0.81 <0.001* 0.0±6.22 -0.7±0.54 NS* -0.2±0.67 -0.6±1.00 NS*

Isi, upper incisor incisal tip; Iii, lower incisor incisal tip; ULP, upper lip point; LLP, lower lip point; Ch, cheilion; NLF, nasolabial fold; WSRS, Wrinkle Severity Rating Scale;

GAIS, Global Aesthetic Improvement Scale; Data presented as % (n); p-value*, Independent two sample t-test; p-value†,Chi-square test (fisher’s exact test); NS indicates P >0.05.

- 24 -

For females less than 30 yrs, quantitative changes of NLFs (NLF1 ∆y and NLF2 ∆y) showed

moderate to high positive correlation with hard (Isi ∆y and Iii ∆y), and soft tissue (ULP ∆y, LLP

∆y, Ch ∆y and Ck ∆y) changes following retraction (p<0.001, r= 0.59-0.79). However, for

females of equal or greater than 30 yrs, NLF1 ∆y or NLF2 ∆y showed limited correlation only

with lip soft tissue (ULP∆y, LLP∆y and Ch∆y) (r= 0.66-0.71, p<0.05). For males, NLF1 ∆y and

NLF2 ∆y indicated significant moderate to high correlation only with Ck ∆y (r=0.67-0.71, p<0.05)

(Table 11)

- 25 -

Table 11. Correlations between quantitative posterior changes of nasolabial folds and changes of hard and soft tissue (mm, Pearson correlation

tests)

` Female Male

<30 yrs (n=28) 30 yrs ≤ (n=11) <30 yrs (n=13) 30 yrs ≤ (n=0)

NLF1 ∆y NLF2 ∆y NLF1 ∆y NLF2 ∆y NLF1 ∆y NLF2 ∆y

Not

available

r p-value r p-value r p-value r p-value r p-value r p-value

Isi ∆y 0.663 <0.001 0.754 <0.001 0.494 NS 0.591 NS 0.323 NS 0.25 NS

Iii ∆y 0.719 <0.001 0.762 <0.001 0.253 NS 0.517 NS 0.189 NS 0.185 NS

ULP ∆y 0.645 <0.001 0.748 <0.001 0.679 0.022 0.713 0.014 0.070 NS 0.17 NS

LLP ∆y 0.697 <0.001 0.789 <0.001 0.502 NS 0.664 0.026 0.216 NS 0.185 NS

Ch ∆y 0.59 0.001 0.741 <0.001 0.574 NS 0.687 0.019 0.374 NS 0.176 NS

Ck ∆y 0.655 <0.001 0.692 <0.001 0.233 NS 0.367 NS 0.666 0.013 0.712 0.006

NLF, nasolabial fold; Isi, upper incisor incisal tip; Iii, lower incisor incisal tip; ULP, upper lip point; LLP, lower lip point; Ch, cheilion; NS indicates P >0.05.

- 26 -

4. Clinical visual changes of NLFs after orthodontic treatment – GAIS

In addition to the quantitative changes of NLFs, GAIS score was evaluated to monitor the

perceived visual changes of the NLFs following orthodontic treatment. Despite similar amount of

anterior teeth retraction, various clinical visual changes in NLFs were found as shown in Fig 4.

Figure 4. Representative pre and post-treatment images indicating the changes of the nasolabial

folds using modified GAIS.

A, age 24, female, posterior changes in upper incisor (Isi ∆y, -7.3mm), majority scored ‘GAIS 1, improved’ ;

B, age 23, female, posterior changes in upper incisor (Isi ∆y, -8.3mm), majority scored ‘ GAIS 0, no change’ ;

C, age 34, female, posterior changes in upper incisor (Isi ∆y, -7.3mm), majority scored ‘GAIS -1,worsened’.

- 27 -

The majority of GAIS score were within no change criteria (GAIS 0), followed by improved

(GAIS 1) and worsen (GAIS -1) criteria, but higher averaged GAIS score was noted in the

retraction group of females less than 30 yrs compared to the corresponding control group

(p<0.05). Accordingly, significant difference in each score category distribution was found only

between the retraction group of females less than 30 yrs and the corresponding control group

(p<0.01). For females less than 30 yrs, the odds ratio (95% CI) was 2.44 (1.3461-4.4226)

indicating that the possibility for improvement of GAIS score in the retraction group was 2.44

times greater than the control group. For females of equal or greater than 30 yrs and for males, no

statistical significance was noted for GAIS between the retraction and control groups (Table 12).

- 28 -

Table 12. Differences of averaged GAIS scores and distribution of GAIS scores between the control group and retraction group according to age

group in each gender

Female Male

<30 yrs (n=28)

30 yrs ≤ (n=11)

<30 yrs (n=13)

30 yrs ≤ (n=0)

Control

group

(n=13)

Retraction

group

(n=15)

p-

value

Control

group

(n=4)

Retraction

group

(n=7)

p-

value

Control

group

(n=9)

Retraction

group

(n=4)

p-

value

Control

group

Retraction

group

p-

value

Averaged GAIS score 0.2±0.16 0.4±0.27 0.022* 0.1±0.28 0.0±0.48 NS* 0.2±0.12 0.3±0.43 NS*

Not available

GAIS score

1 22.4% (35) 42.8% (77)

0.003†

25.0% (12) 33.3% (28)

NS†

24.1% (26) 43.8% (21)

NS†

0 68.6% (107) 52.2% (94) 62.5% (30) 33.3% (28) 68.5% (74) 45.8% (22)

-1 9.00% (14) 5% (9) 12.5% (6) 33.3% (28) 7.4% (8) 10.4% (5)

Total 100% (156) 100% (180) 100% (48) 100% (84) 100%

(108) 100% (48)

OR

(95% CI) 2.44 (1.3461-4.4226) NS NS

Data presented as % (n); GAIS, Global Aesthetic Improvement Scale; p-value*, Independent two sample t-test; p-value†, Generalized estimating equations; NS indicates P >0.05.

- 29 -

IV. Discussion

3D evaluation of the soft tissue indicated that the changes in occlusion by maximum

retraction induces quantitative and perceived changes of the NLFs. However, these changes in the

NLFs are influenced not only by the amount of tooth movement, but also by the intrinsic factors

such as age and gender.

Quantitatively, NLFs moved posteriorly along with the perioral soft tissue following anterior

retraction and the amount of its change positively correlated with the amount of changes of

surrounding tissue; anterior teeth and the lips in medial side and cheek area in lateral side

especially in young females under 30 years old. The posterior movement of the deepest area of the

NLFs may imply deepening of the folds which results in unfavorable facial appearance. However,

unlike our concerns, the appearance of NLFs did not worsen, but rather improved in young

females.

Anatomically, the medial side of NLFs is tightly associated with the muscle fibers and fixed

to the maxilla by the ligaments, while the lateral side of the NLFs contains relatively large amount

of subcutaneous fat which is very mobile and readily undergo obesity- and age-related changes of

adipose tissue or decrease of dermal elasticity.38,41 Clinically, changes in the NLFs are classified

into skin sagging type, manifested as a deep furrow but disappears in supine position; bone

retrusion type, manifested as a concave depression due to the retrusion of bone around the

pyriform aperture; muscular type, manifested as a deep furrow in both upright and supine position

due to the high tension resulting from muscle contraction; and cheek fat pad type, manifested as

broad concave depression due to the relatively thick soft tissue mass in the lateral side of the

NLFs.18 Given that the skin elasticity and soft tissue thickness decreases with redistribution of

subcutaneous adipose tissue with aging,31,38 we initially hypothesized that greater perceived

changes may be noted in the older age group. However, our subjects were composed of relative

- 30 -

young adults, where skin sagging type is reportedly rare to start with,18 and changes of bony

structure similar to the bone retrusion type were not noted as well. Thus, unlike the conventional

physiologic changes of the NLFs due to major volumetric changes of the lateral side of the fold,

active reorientation of both the soft and hard tissue in the medial side of the NLFs (i.e. the perioral

region) induced by orthodontic retraction may have overwhelmed the quantitative posteior

changes of the NLFs per se and improved the overall esthetic aspects of the NLF (Fig 5). For

females in under the age of 30, the combination of minor posterior change of lateral side of NLFs

(i.e. the cheek region) may have also contributed to the improvement of GAIS as well.

Figure 5. An example of superimposed axial cross sectional image at NLF 2 level of retraction group.

Posterior changes of lip has overwhelmed the posteior changes of the NLFs per se; Gray area, pretreatment;

Red area, post-treatment.

In general, soft tissue and dermis is thicker42 with abundant dermal blood flow in males,43 and

facial aging feature are reportedly different between males and females.30,37 Clinically, greater soft

tissue response after incisor retraction is noted with patients with thinner lips,44 and soft tissue

change after orthodontic treatment are reportedly greater and more extensive in females than in

- 31 -

males.39,45,46 Similarly, in our study, quantitative and perceived changes of the NLFs were more

distinct in young females, while males were less sensitive to the overall soft tissue changes.

However, due to the relative small sample size of males in this study, age-matched larger scale

investigation is required to confirm the positive gender difference.

Parasagittal perioral soft tissue showed volumetric change as well as the midsagittal soft

tissue following maximum retraction. These changes were short-term phenomenon not shown in

controls, which implies that the changes were purely derived by anterior retraction. Landmarks

along the midline reportedly indicate most prominent posterior changes while the changes

gradually decreased to the outer area after anterior retraction.13 Accordingly, similar but more

prominent differences in midsagittal vs. parasagittal soft tissue were noted in the vertical

dimension. Vertical changes following retraction were more prominent in the landmarks

representing medial area of nasal soft tissue, perioral soft tissue (A’ and B’) and lips than the

parasagittal soft tissue such as AC and Ch. Facial aging process involves vertical changes of soft

tissue; increase of prolabium, decrease of vermilion height and descending nose midsagittally, or

descending mouth corners or sagging cheeks parasagittaly.15 Among these changes, the earliest

signs of aging appear in the parasagittal area of surrounding the eye and the NLFs, rather than the

midsagittal area.37 Although the vertical changes of the NLFs could not be detected based on our

landmark evaluation, it is noteworthy that major vertical soft tissue changes following retraction

were limited to the midsagittal area unlike the physiologic nature of facial aging.

Conventionally, MRIs or facial scans are used to monitor the morphologic changed in

NLF,20,21 but this study applied CBCT images. CBCT provides both the 3D hard and the soft tissue

quantification, and the fast superimposition techniques allowed additional adjustment for precise

landmark positioning.47,48 Although facial scans or photos can be applied for GAIS templates,33

according to our pilot study, GAIS result were influenced by lighting conditions of clinical photos,

presented facial angles, facial make-up, and the examiner’s field of expertise. Due to the

- 32 -

retrospective nature of the study, we then applied the reconstructed CBCT facial images without

color and texture to avoid the external features such as lighting or facial make up that may

influence the esthetic aspects of the NLFs. Both the frontal and the three-quarter view images were

presented in random order and averaged scores from 6 investigators of different specialties,

orthodontists, plastic surgeon, and dermatologists were used for the final statistical evaluation.

NLF contains several muscle insertions,49 and is known as the ‘smile line’ which is

emphasized when facial muscles function. Thus, resting muscle activity should be considered

prudently and additional dynamic analysis of NLFs in functional state combined with the

perceived and volumetric analysis would be helpful for further investigations.

- 33 -

V. Conclusion

Orthodontic retraction induced quantitative and perceived changes of the NLFs. The changes

in the NLFs were also affected by intrinsic factors such as age and gender. Especially, for young

adult females under the age of 30, the appearance of the NLFs significantly improved after

maximum retraction, despite the posterior change of the NLFs.

- 34 -

VI. References

1. Ackerman JL, Proffit WR, Sarver DM. The emerging soft tissue paradigm in orthodontic

diagnosis and treatment planning. Clin Orthod Res 1999;2:49-52.

2. Janson G, Fuziy A, de Freitas MR, Castanha Henriques JF, de Almeida RR. Soft-tissue treatment

changes in Class II Division 1 malocclusion with and without extraction of maxillary premolars.

Am J Orthod Dentofacial Orthop 2007;132:729.e721-728.

3. Bravo LA. Soft tissue facial profile changes after orthodontic treatment with four premolars

extracted. Angle Orthod 1994;64:31-42.

4. Metzger TE, Kula KS, Eckert GJ, Ghoneima AA. Orthodontic soft-tissue parameters: a

comparison of cone-beam computed tomography and the 3dMD imaging system. Am J Orthod

Dentofacial Orthop 2013;144:672-681.

5. Nguyen T, Cevidanes L, Cornelis MA, Heymann G, de Paula LK, De Clerck H. Three-

dimensional assessment of maxillary changes associated with bone anchored maxillary

protraction. Am J Orthod Dentofacial Orthop 2011;140:790-798.

6. LeCornu M, Cevidanes LH, Zhu H, Wu CD, Larson B, Nguyen T. Three-dimensional treatment

outcomes in Class II patients treated with the Herbst appliance: a pilot study. Am J Orthod

Dentofacial Orthop 2013;144:818-830.

7. Plooij JM, Maal TJ, Haers P, Borstlap WA, Kuijpers-Jagtman AM, Berge SJ. Digital three-

dimensional image fusion processes for planning and evaluating orthodontics and orthognathic

surgery. A systematic review. Int J Oral Maxillofac Surg 2011;40:341-352.

- 35 -

8. Leonardi R, Annunziata A, Licciardello V, Barbato E. Soft Tissue Changes Following the

Extraction of Premolars in Nongrowing Patients With Bimaxillary Protrusion. The Angle

Orthodontist 2010;80:211-216.

9. Kim K, Choi S-H, Choi E-H, Choi Y-J, Hwang C-J, Cha J-Y. Unpredictability of soft tissue

changes after camouflage treatment of Class II division 1 malocclusion with maximum anterior

retraction using miniscrews. Angle Orthod 2017;87:230-238.

10. Park Y-C, Choi Y-J, Choi N-C, Lee J-S. Esthetic segmental retraction of maxillary anterior

teeth with a palatal appliance and orthodontic mini-implants. Am J Orthod Dentofacial Orthop

2007;131:537-544.

11. Choi YJ, Shin S, Kim K-H, Chung CJ. Orthodontic retraction of autotransplanted premolar to

replace ankylosed maxillary incisor with replacement resorption. Am J Orthod Dentofacial

Orthop 2014;145:514-522.

12. Choi N-C, Park Y-C, Jo Y-M, Lee K-J. Combined use of miniscrews and clear appliances for

the treatment of bialveolar protrusion without conventional brackets. Am J Orthod Dentofacial

Orthop 2009;135:671-681.

13. Ahn HW, Chang YJ, Kim KA, Joo SH, Park YG, Park KH. Measurement of three-dimensional

perioral soft tissue changes in dentoalveolar protrusion patients after orthodontic treatment

using a structured light scanner. Angle Orthod 2014;84:795-802.

14. Solem RC, Marasco R, Guiterrez-Pulido L, Nielsen I, Kim SH, Nelson G. Three-dimensional

soft-tissue and hard-tissue changes in the treatment of bimaxillary protrusion. Am J Orthod

Dentofacial Orthop 2013;144:218-228.

- 36 -

15. Iblher N, Kloepper J, Penna V, Bartholomae JP, Stark GB. Changes in the aging upper lip--a

photomorphometric and MRI-based study (on a quest to find the right rejuvenation approach).

J Plast Reconstr Aesthet Surg 2008;61:1170-1176.

16. Sforza C, Grandi G, Binelli M, Dolci C, De Menezes M, Ferrario VF. Age- and sex-related

changes in three-dimensional lip morphology. Forensic Sci Int 2010;200:182.e181-187.

17. Ramos AL, Sakima MT, Pinto Ados S, Bowman SJ. Upper lip changes correlated to maxillary

incisor retraction--a metallic implant study. Angle Orthod 2005;75:499-505.

18. Zhang L, Tang MY, Jin R, Zhang Y, Shi YM, Sun BS et al. Classification of nasolabial folds in

Asians and the corresponding surgical approaches: By Shanghai 9th People's Hospital. J Plast

Reconstr Aesthet Surg 2015;68:914-919.

19. Lemperle G, Holmes RE, Cohen SR, Lemperle SM. A classification of facial wrinkles. Plast

Reconstr Surg 2001;108:1735-1750; discussion 1751-1732.

20. Gosain AK, Klein MH, Sudhakar PV, Prost RW. A volumetric analysis of soft-tissue changes in

the aging midface using high-resolution MRI: implications for facial rejuvenation. Plast

Reconstr Surg 2005;115:1143-1152; discussion 1153-1145.

21. Gosain AK, Amarante MT, Hyde JS, Yousif NJ. A dynamic analysis of changes in the

nasolabial fold using magnetic resonance imaging: implications for facial rejuvenation and

facial animation surgery. Plast Reconstr Surg 1996;98:622-636.

22. Cevidanes LH, Motta A, Proffit WR, Ackerman JL, Styner M. Cranial base superimposition for

3-dimensional evaluation of soft-tissue changes. Am J Orthod Dentofacial Orthop

2010;137:S120-129.

- 37 -

23. Weissheimer A, Menezes LM, Koerich L, Pham J, Cevidanes LH. Fast three-dimensional

superimposition of cone beam computed tomography for orthopaedics and orthognathic

surgery evaluation. Int J Oral Maxillofac Surg 2015;44:1188-1196.

24. Baek ES, Hwang S, Kim KH, Chung CJ. Total intrusion and distalization of the maxillary arch

to improve smile esthetics. Korean J Orthod 2017;47:59-73.

25. Lee TY, Kim KH, Yu HS, Kim KD, Jung YS, Baik HS. Correlation analysis of three-

dimensional changes of hard and soft tissues in class III orthognathic surgery patients using

cone-beam computed tomography. J Craniofac Surg 2014;25:1530-1540.

26. Kim G-W, Kim J-H, Lee K-H, Hwang H-S. Reproducibility of asymmetry measurements of

the mandible in three-dimensional CT imaging. Korean J Orthod 2008;38:314-327.

27. Swennen GRJ. 3-D Cephalometric Soft Tissue Landmarks Three-Dimensional Cephalometry:

A Color Atlas and Manual. Berlin, Heidelberg: Springer Berlin Heidelberg; 2006. p. 183-226.

28. Ludlow JB, Gubler M, Cevidanes L, Mol A. Precision of cephalometric landmark

identification: cone-beam computed tomography vs conventional cephalometric views. Am J

Orthod Dentofacial Orthop 2009;136:312.e311-310; discussion 312-313.

29. Lee YJ, Park JT, Cha JY. Perioral soft tissue evaluation of skeletal Class II Division 1: A lateral

cephalometric study. Am J Orthod Dentofacial Orthop 2015;148:405-413.

30. Torlakovic L, Faerovig E. Age-related changes of the soft tissue profile from the second to the

fourth decades of life. Angle Orthod 2011;81:50-57.

31. Sato S, Demura S. Regional subcutaneous fat characteristics stratified by sex, age, and obesity,

and their relationships with total and visceral fat in a Japanese population. J Physiol Anthropol

- 38 -

2009;28:231-238.

32. Day DJ, Littler CM, Swift RW, Gottlieb S. The wrinkle severity rating scale: a validation study.

Am J Clin Dermatol 2004;5:49-52.

33. Ahn JY, Lee SH, Park KY, Hong CK, Song HJ, Park MY et al. Clinical comparison of two

hyaluronic acid-derived fillers in the treatment of nasolabial folds: Mesoglow(R) and IAL

System(R). Int J Dermatol 2012;51:601-608.

34. Narins RS, Brandt F, Leyden J, Lorenc ZP, Rubin M, Smith S. A randomized, double-blind,

multicenter comparison of the efficacy and tolerability of Restylane versus Zyplast for the

correction of nasolabial folds. Dermatol Surg 2003;29:588-595.

35. Lagravere MO, Low C, Flores-Mir C, Chung R, Carey JP, Heo G et al. Intraexaminer and

interexaminer reliabilities of landmark identification on digitized lateral cephalograms and

formatted 3-dimensional cone-beam computerized tomography images. Am J Orthod

Dentofacial Orthop 2010;137:598-604.

36. Hyun MY, Lee Y, No YA, Yoo KH, Kim MN, Hong CK et al. Efficacy and safety of injection

with poly-L-lactic acid compared with hyaluronic acid for correction of nasolabial fold: a

randomized, evaluator-blinded, comparative study. Clin Exp Dermatol 2015;40:129-135.

37. Ezure T, Yagi E, Kunizawa N, Hirao T, Amano S. Comparison of sagging at the cheek and

lower eyelid between male and female faces. Skin Res Technol 2011;17:510-515.

38. Ezure T, Amano S. Involvement of upper cheek sagging in nasolabial fold formation. Skin Res

Technol 2012;18:259-264.

39. Kim YI, Kim JR, Park SB. Three-dimensional analysis of midfacial soft tissue changes

- 39 -

according to maxillary superior movement after horizontal osteotomy of the maxilla. J

Craniofac Surg 2010;21:1587-1590.

40. Louis PJ, Austin RB, Waite PD, Mathews CS. Soft tissue changes of the upper lip associated

with maxillary advancement in obstructive sleep apnea patients. J Oral Maxillofac Surg

2001;59:151-156.

41. Ghassemi A, Prescher A, Riediger D, Axer H. Anatomy of the SMAS revisited. Aesthetic Plast

Surg 2003;27:258-264.

42. Kalha AS, Latif A, Govardhan SN. Soft-tissue cephalometric norms in a South Indian ethnic

population. Am J Orthod Dentofacial Orthop 2008;133:876-881.

43. Seidenari S, Zanella C, Pepe P. Echographic evaluation of sodium lauryl sulfate (SLS)-induced

irritation in mice. Contact Dermatitis 1994;30:41-42.

44. Oliver BM. The influence of lip thickness and strain on upper lip response to incisor retraction.

Am J Orthod 1982;82:141-149.

45. Kolokitha OE, Chatzistavrou E. Factors influencing the accuracy of cephalometric prediction

of soft tissue profile changes following orthognathic surgery. J Maxillofac Oral Surg

2012;11:82-90.

46. Mobarak KA, Krogstad O, Espeland L, Lyberg T. Factors influencing the predictability of soft

tissue profile changes following mandibular setback surgery. Angle Orthod 2001;71:216-227.

47. Fernandes TM, Adamczyk J, Poleti ML, Henriques JF, Friedland B, Garib DG. Comparison

between 3D volumetric rendering and multiplanar slices on the reliability of linear

measurements on CBCT images: an in vitro study. J Appl Oral Sci 2015;23:56-63.

- 40 -

48. Almukhtar A, Ju X, Khambay B, McDonald J, Ayoub A. Comparison of the accuracy of voxel

based registration and surface based registration for 3D assessment of surgical change

following orthognathic surgery. PLoS One 2014;9:e93402.

49. Rubin LR. The anatomy of the nasolabial fold: the keystone of the smiling mechanism. Plast

Reconstr Surg 1999;103:687-691; discussion 692-684.

- 41 -

국문요약

교정적 후방 견인 후 비순구 및 입 주위 연조직의 삼차원적 변화 양상

<지도교수: 정 주 령, D.D.S., Ph.D.>

연세대학교 대학원 치의학과

백 의 선

돌출입 환자에 있어 소구치 발치를 동반한 교정적 후방견인은 안면 부위의

광범위한 연조직 변화를 유발한다. 이러한 연조직 변화는 입술을 비롯한 치아 주변

조직 뿐 아니라, 코 부위 및 비순구 부위까지 확장될 수 있다고 알려져 있다. 하지만,

교정 치료에 따른 비순구의 형태적인 변화 및 이로 인한 심미성의 변화양상에

대해서는 알려져 있지 않다.

본 연구의 목적은 돌출입 환자에서 소구치 발치를 동반한 교정치료 후 전,후

CBCT를 이용하여 비순구를 포함한 연조직 변화를 삼차원적으로 정량화하고

비순구의 심미적인 개선여부를 평가하여 대조군과 비교함으로써 교정치료에 따른

비순구의 변화에 영향을 추적하고 이에 영향을 끼치는 기여인자를 알아보는 것이다.

이 연구에서는 18 세 이상 52 명의 성인 환자들을 소구치 발치후 4mm 이상

전치부 후방이동이 일어난 후방 견인 군(n=26)과 전치부 전후방 변화량 1.5mm

- 42 -

이내의 대조군(n=26)으로 분류하였다. 전,후 CBCT및 두개저 중첩을 이용하여 코,

입 주변 연조직, 입술, 비순구 부위의 객관적,정량적 변화를 계측하였다. CBCT를

이용한 연조직 표면 영상을 통해 초진시 주관적 비순구 severity를 Winkle Severity

Rating Scale (WSRS)로 평가하였고, 각 분야 6 명의 전문가가 비순구 부위의

주관적 개선, 변화 없음, 악화 여부를 를 Global Aesthetic Improvement Scale

(GAIS)로 평가 하였다. 비순구 부위의 주관적 또는 객관적 변화에 대한 기여 요인을

알아보기 위해 성별과 30 세를 기준으로 두 연령군으로 나누어 치료 요인(전치부

이동량, 입술 변화량, 비순구 변화량)과 내적 요인(초진 비순구 severity 및 초진

연조직 두께)을 분석하였다.

전치부 후방 견인에 따라 비순구, 입술, 입 주위 연조직, 코 주위 연조직에서

대조군에 비해 유의한 삼차원적 변화가 관찰되었다. 후방 견인 군에서는 여자에서

상,하악 전치에 각각 6.4±0.57, 5.4±1.73mm 의 후방이동이, 남자에서 각각

5.4±1.36, 5.6±1.65mm 의 후방이동이 일어났다. 여자 후방 견인 군에서 광범위한

전후방적, 수직적인 연조직 이동이 일어났다. 후방이동은 상순 (2.7±1.22mm), 하순

(4.3±1.41mm), cheilion (4.1±1.71mm) 뿐만 아니라 비순구 (NLF1 0.8±0.66mm,

NLF2 1.2±0.78mm) 에서 대조군에 비해 유의하게 일어났고, 코에서도 상순과의

경계인 subnasale (0.6±0.71mm), subalare (0.8±0.55mm)에서 유의한 후방이동이

일어났다. 수직적으로 상순 vermilion border상의 점들은 하방 이동 했고 labialis

inferius는 상방이동 하면서 prolabium이 1.0±1.21mm 길어지고 상순과 하순의

vermilion height가 각각 1.3±0.94, 1.6±1.20mm 짧아졌다. 수직 이동은 코, 입 주변

연조직, 입술의 정중 시상면 근처의 점들에서 유의했고 (p<0.05), alar curvature와

cheilion과 같은 측방의 점들에서는 유의하지 않았다.

- 43 -

남자 후방 견인 군에서는 여자 후방 견인군과 비슷한 변화가 관찰되었으나, 코

부위 연조직은 유의한 이동을 보이지 않았고, 상순에서의 수직적 변화도 유의하지

않아서, prolabium 길이와 상순 vermilion height에서 유의한 증감을 보이지 않았다.

남자 후방 견인 군에서 비순구의 후방이동량은 대조군과의 유의한 차이를 보이지

않았다.

비순구의 정량적 후방 이동량은 전치부 후방 이동량 및 입술 후방 이동량과

유의한 양의 상관관계를 나타냈다. (r>0.5, p<0.001) 성별과 나이에 따라 분류한 후

treatment factor와 host factor를 비교 했을 때 여자 30 세 이하 군에서, 후방 견인

군이 대조군에 비해 비순구의 후방 이동량이 유의하게 컸음에도 불구하고 평균 GAIS

score가 유의하게 컸으며 (p<0.05), 비순구 부위가 치료 전보다 개선될 확률이

대조군에 비해 2.44 배 컸다. (p<0.01)

결론적으로 교정적 후방 견인에 따른 연조직의 삼차원적 변화는 전반적으로

여자가 남자보다 광범위하게 일어났다. 후방 견인에 따라 비순구 부위에서 0.7-

1.2mm의 유의한 후방이동이 일어났으며 이는 전치부 후방이동량 및 입술 후방

이동량과 비례했다. 비순구 부위의 객관적, 주관적 평가는 서로 직접적인 연관이

없었고, 연령 및 성별과 같은 개체 요인과 연관이 있었다. 특히 교정적 후방 견인 후

30 세 이하 성인 여자에서, 남자 또는 30 세 이상 성인에 비해 비순구 부위의 정량적

후방 이동량이 더 컸음에도 불구하고 주관적 평가는 오히려 개선되었다.

핵심 단어: 비순구, 연조직, 교정적 후방 견인, 입술 돌출, CBCT