7-11岁患者上颌扩弓治疗前后软组织面部变化的CBCT与3D面部扫描对比

作者
Nafisa Molla¹, Heesoo Oh², Giseon Heo¹, Raisa Catunda³, Manuel Lagravère¹

单位

1. 加拿大阿尔伯塔大学牙科学院
2. 美国太平洋大学Arthur A. Dugoni牙科学院正畸学系
3. 加拿大阿尔伯塔大学牙科学院

通讯作者
Manuel Lagravère
manuel@ualberta.ca

关键词
快速上颌扩弓、错颌畸形、面部软组织、三维成像

摘要

背景
本研究旨在通过CBCT和3D面部扫描，评估7-11岁儿童在上颌扩弓治疗12个月后，面部软组织测量的变化，并与对照组进行比较。研究对象为存在至少5毫米上颌横向发育不足或双侧后牙反颌的患者。

材料与方法
研究纳入32名患者，分为对照组和治疗组（使用Hyrax扩弓器进行快速上颌扩弓，每日旋转1次）。每组患者在治疗前（T0）和扩弓完成后的保留期（T1，12个月后）分别接受CBCT、3D面部扫描和手腕X光检查。CBCT数据使用3D Slicer软件分析，3D面部扫描数据使用OrthoInsight 3D软件分析。评估的软组织测量指标包括：鼻翼宽度、鼻翼基底宽度、口宽、人中宽度、鼻尖突出度、鼻唇角、上下唇与E线的距离、上下唇高度、鼻高度、下面部高度及内眦宽度等。统计分析包括组内和组间变异性、测量误差计算及多元方差分析（MANOVA）。

结果
在32名患者的两组成像记录中，两组在一年的观察期内未发现统计学上的显著差异。然而，当比较CBCT成像和3D面部扫描这两种方法时，某些特定指标（如鼻翼基底宽度和内眦宽度）的相关性并不理想，可能与解剖结构、成像协议及患者相关因素有关。

结论
研究结果表明，两组儿童的面部软组织变化相似。

引言

快速上颌扩弓（RME）是正畸医生用于增加上颌横向尺寸并矫正上颌横向发育不足的治疗方法，常用于后牙反颌和上颌拥挤的病例。除了引起骨骼和牙齿变化外，RME还可能影响患者的面部软组织轮廓。一些研究表明，RME可能导致鼻宽、口宽、人中宽度及下唇与E线距离的增加。CBCT研究进一步支持了RME对硬组织和软组织的影响。

目前大多数关于非手术RME效果的研究比较了不同类型的扩弓装置，如带环式、粘接式或改良式扩弓器。少数研究将实验组与对照组进行比较，有助于区分变化是由自然生长发育还是RME的真实效果引起。不同研究采用了不同的评估方法，如侧位或前后位头影测量、CBCT或三维立体摄影测量。然而，迄今为止，尚无研究同时使用CBCT和3D面部摄影扫描作为研究手段来探讨RME相关的面部软组织变化。

本研究将利用CBCT和3D面部扫描作为研究手段，并纳入对照组进行比较分析。主要目的是确定在扩弓前（T0）和扩弓后（T1）通过CBCT和3D面部扫描获得的平均面部软组织测量值是否存在统计学上的显著差异。次要目的是通过3D面部扫描和CBCT测量，确定治疗组和对照组从T0到T1是否存在显著差异。假设两组患者及两种成像方法之间均无差异。

方法

研究在阿尔伯塔大学正畸研究生诊所进行，并获得研究伦理委员会批准（Pro00061538）。数据收集自32名患者，分为两组：

• 对照组：16名7-11岁未接受上颌扩弓治疗的患者；
• 治疗组：16名7-11岁接受上颌扩弓治疗的患者。

纳入标准为存在至少5毫米上颌横向发育不足或双侧后牙反颌的患者。排除标准为有颅面疾病或综合征病史，以及有正畸治疗或上颌扩弓史的患者。

样本量基于Santariello等（2014）的研究结果计算，使用G*Power软件估计每组92名受试者，以达到80%的统计功效和α=0.05的I型错误率。本初步研究纳入32名患者，这是研究的局限性之一。

每位患者在治疗前（T0）和扩弓完成后的保留期（T1，12个月后）分别接受CBCT、3D面部扫描、手腕X光及口内外照片检查。骨骼成熟度通过手腕X光分析Fishman骨骼成熟指数（SMI）确定。

CBCT使用I-CAT新一代设备（大视野16×13.3 cm，体素大小0.30 mm，120 kVp，18.54 mAS，扫描时间8.9秒）获取，患者Frankfort平面与地面平行，头部通过固定带稳定。患者在扫描时避免吞咽，保持最大牙尖交错位，并将舌抵住上颌中切牙的舌面。数据以DICOM格式存储并编码，使用3D Slicer软件分析。

三维面部扫描使用Facial Insight 3D扫描仪获取，患者Frankfort平面与地面平行，保持中性面部表情。所有数据编码并盲法处理。

治疗组患者使用Hyrax型扩弓器（10 mm Forestadent）进行RME治疗。扩弓器通过金属带环粘接在上颌第一磨牙上，患者每日旋转螺丝1次（0.25 mm）。所有患者均达到上颌横向发育不足的过矫正，即上颌磨牙的腭尖接触下颌磨牙的颊尖。平均扩弓量为6.53 mm（26次旋转），范围20-36次旋转。

激活期结束4个月后，Hyrax扩弓器被替换为标准被动横腭弓。数据导入3D Slicer软件进行软组织测量。3D面部扫描保存为OI3D文件，使用OrthoInsight 3D软件通过标志点和线性及角度测量进行软组织分析。标志点和测量定义见表I和表II，可视化见图2a和b。

图1 a：水平和矢状参考平面；b：冠状参考平面及不同视角

统计方法

统计分析使用SPSS软件（版本28.0）进行，显著性水平设为α=0.05。通过组内相关系数（ICC）评估组内和组间可靠性。可靠性试验在10个CBCT扫描和10个3D面部扫描上使用5个标志点和3个线性测量在三个时间点（间隔7天）进行。组间可靠性由两名正畸医生评估。此外，还计算了测量误差以评估测量的准确性。主要分析采用多元方差分析（MANOVA）。

结果

研究最初纳入32名患者，每组16名。然而，治疗组1名患者因文件损坏无法恢复初始时间点数据，对照组1名患者因迁至其他省份退出试验。最终30名患者完成研究，每组15名。

基线特征见表III。两组在人口统计学特征上无显著差异。标志点测量的组内ICC值最低为0.98（3D面部扫描）和0.97（CBCT）。Fishman SMI的组内ICC为0.92。相比之下，CBCT和3D面部扫描比较的最低ICC为0.65。测量误差以毫米为单位计算，3D面部扫描最高为0.35 mm，CBCT最高为0.50 mm。

表IV描述了T0和T1时的平均值和95%置信区间。T0时，CBCT与3D面部扫描测量值的差异范围为0.01-1.38 mm；T1时为0.08-1.21 mm。表V描述了百分比变化的描述性统计。某些测量显示对照组的百分比变化略高于治疗组，但差异极小。

表VI总结了每组14项测量随时间的变化。负值表示减少，正值表示增加。治疗组和对照组的平均变化均约为1 mm。MANOVA结果显示，CBCT和3D面部扫描在T0和T1时的平均面部软组织测量值存在显著差异（P<0.001），但治疗组和对照组之间无显著差异。

图2 标志点和测量识别。a：正面观；b：侧面观

讨论

目前，包含对照组的研究数量有限，这有助于区分自然生长对面部软组织的潜在影响。Aljawad等比较了两种成像方法在软组织测量和分析方面的差异，发现软组织表面差异平均小于1 mm。Toma等发现大多数标志点的差异在1 mm以内，被认为是可接受的。

在确定鼻翼基底宽度（ABW）测量时，标志点的放置较为主观。患者体位误差、未保持中性面部表情以及图像定向误差可能进一步增加了局限性。由于患者年龄较小，部分患者在最大牙尖交错位时可能无意中未保持中性面部表情，从而影响口宽测量。图3a和b展示了同一患者在3D面部扫描中保持中性表情，而在CBCT图像中因最大牙尖交错位导致表情变化。

比较治疗组和对照组特定指标的百分比变化时，变化值相似。Truong等发现治疗组ABW总变化为1.95 mm，对照组为1.29 mm，差异无统计学意义。Torun等发现从RME治疗开始到保留期6个月后，ABW的变化在青春期后组为0.5 mm，青春期前组为1 mm。

除鼻唇角及上下唇与E线位置外，所有测量均显示随时间呈正向变化。后者显示角度减小及上下唇整体后缩，与先前研究结果一致。这种变化可能是由于扩弓过程中嘴唇被拉伸导致厚度减少。

在上下唇与E线的软组织测量方面，Halıcıog˘lu和Yavuz发现两项测量均减少约1 mm，保留期后（平均6.42个月）测量值与扩弓前相似。Huang等发现从扩弓前到保留期后，上唇与E线的平均差异为-0.11 mm，下唇与E线为0.42 mm，无显著差异。因此，作者认为RME可能不会引起上下唇与E线关系的临床重要变化。

比较治疗组和对照组面部软组织测量的平均变化，差异普遍小于1 mm，进一步表明RME治疗对面部软组织的临床影响不显著。Truong等发现，对于鼻高度，治疗组在扩弓后立即增加0.34 mm，2.84年后增加至4.39 mm，而对照组在2.25年内仅增加2.87 mm。两组间1.52 mm的差异无统计学意义。Truong等认为长期来看，治疗组与对照组的增益相似，RME未在治疗和未治疗患者间产生软组织测量的差异。

考虑到下面部，先前研究表明RME时下颌向下和向后旋转，这种模式也见于生长发育过程中。这可能导致下面部高度或下唇高度的增加，以及鼻和唇的软组织相关变化。本研究两组间无显著差异，与Huang等的综述结果一致。然而，由于成像协议、分析及样本量的局限性，结果需谨慎解读。

图3 3D面部。a：3D面部扫描（OrthoInsight 3D）；b：CBCT（3D Slicer）

结论

7-11岁接受上颌扩弓治疗的儿童，其面部软组织变化与未接受扩弓治疗的患者在一年内的变化相似。

资助
本研究未从任何公共、商业或非营利部门的资助机构获得特定资助。

作者贡献
N.M.分析并解释患者数据，撰写论文；R.Q.C.协助三维测量、数据分析和论文撰写；G.H.协助数据和统计分析；M.L.参与研究设计、患者招募、数据分析和论文修订。所有作者阅读并批准最终稿件。

数据可用性
当前研究中使用和分析的数据集可根据合理要求从通讯作者处获得。

伦理批准与参与同意
本研究在阿尔伯塔大学正畸研究生诊所进行，并获得阿尔伯塔大学研究伦理委员会批准（pro00061538）。

利益冲突
作者声明无利益冲突。

Comparison of soft tissue facial changes in patients 7–11 years of age with and without maxillary expansion utilizing CBCTs and 3D facial scans: A preliminary study

Nafisa Molla ¹ , Heesoo Oh ² , Giseon Heo ¹ , Raisa Catunda ³ , Manuel Lagravère ¹

Available online:

1. Department of Dentistry, Edmonton Clinic Health Academy, University of Alberta, 11400 87 Avenue, Edmonton, AB, T6G 1Z1, Canada

• 2. Department of Orthodontics, Arthur-A.-Dugoni School of Dentistry, University of the Pacific, San Francisco, CA, 94103, United States
• 3. Department of Dentistry, University of Alberta, 7-002 Katz building 11361 87 Avenue, Edmonton, AB, T6G 2E1, Canada

Correspondence:

Manuel Lagravère, 5-524 Edmonton Clinic Health Academy, 11405 – 87 Avenue NW, Edmonton, AB, T6G 1C9, Canada. manuel@ualberta.ca

Keywords

Rapid maxillary expansion Malocclusion Facial soft tissue Three-dimensional imaging

Summary

Background > The objectives of this study are to evaluate the effects of maxillary expansion over a period of 12 months on facial soft tissue measurements in children aged 7–11 years with a maxillary transverse deficiency of at least 5 mm or bilateral posterior crossbite, utilizing both CBCTs and 3D facial scans, by comparison to a control group.

Material and methods > Data was collected from 32 patients and consisted of two groups: control and treatment (Hyrax expansion via RME, 1 turn/day). Each patient in each group underwent CBCTs, 3D facialscans and hand-wrist radiographs at two time points: pre-treatment (T0), and after the completion of expansion at post-retention (T1, 12 months). CBCTs were assessed using 3D Slicer software and 3D facial scans were assessed using OrthoInsight 3D software. The soft tissue measurements evaluated included the following: alar width, alar base width, mouth width, philtrum width, nasal tip prominence, nasolabial angle, upper lip to E-line, lower lip to E-line, upper lip height, height of vermillion of upper lip, lower lip height, height of nose, lower facial height and intercanthal width. Statistical analysis included intra- and inter-rater variability, measurement error calculation and MANOVA tests.

Results > From a total of 32 patients with two sets of imaging records, no statistically significant differences were found between the two groups over the one-year observation. However, when comparing the two modalities utilized in this study (CBCT imaging and 3D facial scanning), the correlation was not as optimal for specific outcome variables such as alar base width and intercanthal width, potentially due to anatomic, imaging protocols and patient related factors. Conclusion > The findings of this study suggest that the children in both groups experienced similar facial soft tissue changes.

Introduction

Rapid maxillary expansion (RME) is a therapeutic modality used by orthodontists to increase the transverse dimension of the maxilla and correct transverse maxillary discrepancies [1–4]. It is a treatment option commonly used in cases presenting with posterior crossbite and maxillary crowding [1,2]. In addition to causing skeletal and dental changes, it has also been established that RME can influence the facial soft tissue profile of patients [1–3]. Some reports have shown that RME may result in significantly increased nasal width, mouth width, upper philtrum width, and distance from the lower lip to the E-line after the retention phase [2,5–7]. Further adding support to the notion that RME results in both hard and soft tissue changes are the cone-beam computer tomography (CBCT) studies [5,6]. Some studies point out that both pre- and post-pubertal groups underwent statistically significant changes in soft tissue nasal base, philtrum width, upper lip length, columella width, columella height, and cheek projection [5,6].

The majority of studies on the effects of non-surgical RME have compared different types of expansion devices such as banded, bonded or modified expanders with acrylic splints [8–13]. A small number of studies have compared experimental groups with a control group, which could potentially benefit the field of research in differentiating whether the changes are due to natural growth and development or a true expression of the effects of non-surgical RME [5,7,14,15]. Different studies have also utilized different methods of assessing the outcomes – for example using lateral or anteroposterior cephalograms, CBCTs or three-dimensional (3D) stereophotogrammetry. However, to date, no studies have investigated soft tissue facial changes associated with RME utilizing both CBCT and 3D facial photographic scanning as investigating modalities [2,6,10].

This study will leverage CBCT and 3D facial scans as investigative modalities. Additionally, a control group will be incorporated for comparative analysis, representing the primary objective of the proposed research study. The primary objective of the study is to determine any statistically significant differences in the mean facial soft tissue measurements jointly between CBCTs and 3D facial scans prior to maxillary expansion (T0) and after maxillary expansion (T1). The secondary objective of the study is to determine any statistically significant differences between treatment and control groups from T0 to T1 utilizing 3D facial scan soft tissue measurements and CBCT measurements alike. The hypothesis for both primary and secondary objectives are that there is no difference between both groups of patients and also between both imaging methodologies.

Methods

The study was conducted at the Orthodontic Graduate Clinic at the University of Alberta with ethics approval from the Research Ethics Board (Pro00061538). Data was collected from a total of 32 patients, consisting of two groups:

• control group: 16 patients between 7–11 years of age treated or not but who had not undergone maxillary expansion;
• treatment group: 16 patients between 7–11 years of age who had undergone maxillary expansion.

Patients presenting with a maxillary transverse deficiency of at least 5 mm or bilateral posterior crossbite were included. Patients with any previous history of craniofacial diseases or syndromes and any previous history of orthodontic therapy or maxillary expansion were excluded.

The sample size was calculated based on the findings of the study by Santariello et al. (2014) which examined the effect of RME on soft tissue nasal widths [16]. Using G*Power software (version 3.1.9.2; Heinrich Heine University, Düsseldorf, Germany), a sample size of 184 subjects (92 subjects per group) was estimated to provide 80% statistical power and Type I error rate a = 0.05. A total of 32 patients were used for our preliminary study, which is a limitation of the study.

Each patient underwent CBCTs, 3D facial scans, hand-wrist radiographs, and extra/intra oral photographs at two time points: pre-treatment (T0, before maxillary expansion), after the completion of expansion (T1, 12 months after T0).

Skeletal maturation was determined by analyzing hand-wrist radiographs utilizing the Fishman skeletal maturity index (SMI). Hand-wrist radiographs can serve as a complementary tool to CBCT in assessing mid-palatal suture maturation by providing an indirect yet reliable evaluation of skeletal maturity. Among these, the SMI method has shown superior diagnostic reliability compared to the MP3 method [17,18].

CBCTs were obtained by means of the I-CAT New generation (large field of view 16 13.3 cm with a voxel size of 0.30 mm, 120 kVp, 18.54 mAS over 8.9 seconds), with patients' Frankfort horizontal planes parallel to the floor and head stabilized via strips comparable to previousstudies[19,20]. Patients were also instructed to avoid swallowing and maintain maximum intercuspation as well as place their tongues against the lingual surfaces of the maxillary central incisors while the images were being taken. The files were stored in DICOM format and coded. The CBCTs were assessed using 3D Slicer software (version 4.11.20210226, Boston, MA, USA).

Three-dimensional facial scans were obtained by means of the Facial Insight 3D Scanner (Motion View LLC, Chattanooga, TN, USA). The facial scans were taken with the patients' Frankfort horizontal planes parallel to the floor, while maintaining a neutral facial expression similarly to described by Kim et al. [21] (figure 1a–c). All data collected were coded and blinded for the purposes of the study.

Patients in the treatment group underwent RME using a Hyraxtype expander (10 mm Forestadent, Pforzheim, Germany). The Hyrax expander consisted of metal bands cemented on the maxillary first molars using Ultra Band-lok (Orthodontic Supply Canada, Fredericton, Canada), which was soldered to a midline

Figure 1 a: horizontal and sagittal reference planes; b: coronal reference plane and from different view

palatal jackscrew and metal arms that extended to maxillary deciduous first molars or first premolars. The patients were then instructed to turn the jackscrew at a rate of one turn or 0.25 mm per day. All patients underwent activation until overcorrection of the maxillary transverse deficiency, once the palatal cusps of the maxillary molars touched the buccal cusps of the mandibular molars was achieved. On average, the patients underwent 6.53 mm of expansion (26 turns), with an overall range between 20–36 turns.

Four monthsfollowing the last day of activation of the appliance, the Hyrax expander was then replaced with a standard passive transpalatal arch with bands cemented on the maxillary first molars using Band-lok.

Data was transferred to the 3D Slicer software (version 4.11.20210226, Boston, MA, USA) for the soft tissue measurements. The 3D facialscans were saved as OI3D files. OrthoInsight 3D software (Version 7.7.5570; Motion View LLC, Chattanooga, TN, USA) was used to perform the soft tissue analysis using landmarks and linear and angular measurements. The definitions of the landmarks used are summarized in tables I and II. The landmarks and measurements can be visualized in figure 2a and b.

TABLE I

Twenty-two soft tissue landmarks with definitions

Soft tissue landmark	Definition
Alare (Al)*	Most lateral point on each alar contour
Alare base (Ab)*	Point where the nasal alar intersects the face on the inferior margin of the nose
Pronasale (Prn)	Most anterior midpoint of the apex of the nose
Subnasale (Sn)	Midpoint between columella nasi and philtrum of upper lip
Labiale superius (Ls)	Midpoint of the vermillion of the upper lip
Upper lip anterior point (Ulap)	Point at the most anterior point of the upper lip
Lower lip anterior point (Llap)	Point at the most anterior point of the lower lip
Stomion (Stm)	Midpoint of the horizontal labial fissure
Chelion (Ch)*	Point at each labial commissure
Columella (Col)	Point of inferior margin of the nasal septum linking the nasal tip to the nasal base
Crista philtri (Cph)*	Point of crossing of the vermillion of the upper lip and elevated margin of the philtrum
Soft tissue nasion (Na)	Intersecting point between soft tissue profile and the sella-nasion line
Soft tissue menton (Me)	Most inferior midpoint on soft tissue contour of the chin
Soft tissue pogonion (Pg)	Most anterior midpoint on soft tissue contour of the chin
Endocanthion (En)*	Point at the inner commissure of the fissure of the eye
Exocanthion (Ex)*	Point at the outer commissure of the fissure of the eye

*: indicates located on right side and left side.

TABLE II Thirteen linear measurements and one angular measurement with definitions

Linear and angular measurements	Definition
Alar base width (ABW)	Most lateral point of the base of insertion of each nostril
Alar width (AW)	Most lateral point to the contour of each nostril
Mouth width (MW)	Right labial commissure to left labial commissure
Philtrum width (PW)	Right to left christa philtri at the vermillion border of the upper lip
Height of nose (HofN)	Soft tissue nasion to subnasale
Nasolabial angle (NL)	Angle between soft tissue nasion, subnasale and labrale superioris
Height of upper lip (HofUL)	Subnasale to stomion
Height of vermillion of upper lip (HofVUL)	Labiale superius to stomion
Height of lower lip (HofLL)	Stomion to soft tissue menton
Lower facial height (LFH)	Subnasale to soft tissue menton
Upper lip to E-line (ULtoE)	Upper lip to E-line (pronasale to soft tissue pogonion)
Lower lip to E-line (LLtoE)	Lower lip to E-line (pronasale to soft tissue pogonion)
Nasal tip prominence (NTP)	Ala to pronasale
Intercanthal width (ICW)	Right to left endocanthion

Figure 2 Landmark and measurement identification. a: in frontal view; b: in lateral view

Statistical methods

The statistical analysis was performed using the Statistical Package for Social Science (IBM SPSS, version 28.0, SPSS Inc., Armonk, NY, USA). The statistical significance level was set at Type I error rate, a = 0.05.

Intra-rater and inter-rater reliability were conducted using the intraclass correlation coefficient (ICC). The reliability trials were performed on ten CBCT scans and ten 3D facialscans utilizing five landmarks and three linear measurements at three timepoints, seven days apart. Inter-rater reliability was performed between two orthodontists. Additionally, measurement errors were also calculated to assess the accuracy of the measurements. Main analyses were performed using multivariate analysis of variance (MANOVA).

Results

There were initially 32 patients included in the study with 16 patients in each group. However, one study participant in the treatment group did not have data available for the initial timepoint due to a corrupt file that could not be recovered. Another study participant in the control group did not complete the trial and dropped out due to a move to a different province. Each of the 30 included patients underwent CBCTs, 3D facial scans, hand-wrist radiographs, and extra/intra oral photographs at two time points: pre-treatment (T0, before maxillary expansion), after the completion of expansion (T1, 12 months after T0).

Baseline characteristics for the participants of the study are shown in table III. No statistically significant differences were found between the treatment and control groups regarding the demographic characteristics.

For the landmark measurements, the lowest intra-rater ICC value for 3D facial scans was 0.98 (95% CI, 0.96–0.99) and that of CBCTs was 0.97 (95% CI, 0.94–0.99). For the Fishman's SMI, the intra-rater ICC was 0.92 (95% CI, 0.85– 0.97).

TABLE III
Mean values of baseline demographic characteristics between groups

Characteristics	Control group (n = 15)	Treatment group (n = 15)	Comparison between groups
	M W SD or frequency (%) (95% CI)	M W SD or frequency (%) (95% CI)
Chronologic age (years)	9.72 1.23 (9.04, 10.40)	9.76 1.42 (8.98, 10.55)	t(28) = 0.08, P = 0.94
Sex
Females	7 (46.7%)	12 (80.0%)	x2 (1) = 3.59
Males	8 (53.3%)	3 (20.0%)	P = 0.06
SMI	2.93 0.88 (2.44, 3.42)	2.93 0.96 (2.40, 3.47)	t(28) = 0.00
			P = 0.99

M: mean; SD: standard deviation; CI: confidence interval.

TABLE IV

Descriptive statistics including mean difference, SD, min, max and 95% CI for 14 outcome variables at pre-treatment (T0) and posttreatment (T1)

	Mean	Standard deviation	Minimum	Maximum	95.0% lower CL for mean	95.0% upper CL for mean	Time
ABW	–1.24	1.13	–4.38	1.72	–1.67	–0.82	Pre-treatment
AW	–0.79	1.00	–3.36	1.51	–1.17	–0.42	Pre-treatment
MW	–0.34	1.10	–3.11	1.27	–0.75	0.07	Pre-treatment
PW	–0.19	0.59	–1.20	0.90	–0.41	0.03	Pre-treatment
HofN	–0.75	0.91	–2.94	0.53	–1.09	–0.41	Pre-treatment
NL angle	–0.51	1.34	–3.25	2.08	–1.01	–0.01	Pre-treatment
HofUL	–0.76	0.82	–2.34	0.75	–1.07	–0.46	Pre-treatment
HofVUL	–0.01	0.56	–1.49	0.93	–0.22	0.20	Pre-treatment
HofLL	–0.99	1.17	–3.87	2.19	–1.43	–0.55	Pre-treatment
LFH	–0.88	1.11	–2.89	1.05	–1.30	–0.47	Pre-treatment
UliptoE	0.02	0.37	–0.69	0.87	–0.12	0.16	Pre-treatment
LliptoE	0.01	0.40	–0.64	0.70	–0.14	0.16	Pre-treatment
NTP	–0.15	0.86	–1.91	1.45	–0.47	0.17	Pre-treatment
ICW	–1.38	0.80	–2.98	0.79	–1.68	–1.08	Pre-treatment
ABW	–1.08	0.99	–4.55	0.86	–1.45	–0.71	Post-expansion
AW	–0.63	0.84	–2.04	1.17	–0.95	–0.32	Post-expansion
MW	–0.51	1.05	–2.34	2.14	–0.90	–0.12	Post-expansion
PW	–0.18	0.57	–1.09	1.17	–0.39	0.03	Post-expansion
HofN	–0.61	0.89	–2.54	0.96	–0.95	–0.28	Post-expansion
NL angle	–0.32	1.27	–3.99	1.85	–0.80	0.15	Post-expansion
HofUL	–0.76	0.77	–2.19	0.72	–1.05	–0.47	Post-expansion
HofVUL	0.08	0.49	–1.24	1.05	–0.11	0.26	Post-expansion
HofLL	–0.92	1.07	–3.15	1.07	–1.32	–0.52	Post-expansion
LFH	–0.94	1.20	–2.62	1.74	–1.38	–0.49	Post-expansion
UliptoE	–0.04	0.28	–0.64	0.45	–0.14	0.07	Post-expansion
LliptoE	0.09	0.26	–0.32	0.61	–0.01	0.18	Post-expansion
NTP	–0.15	0.77	–1.51	1.35	–0.44	0.14	Post-expansion
ICW	–1.21	0.85	–2.64	1.27	–1.53	–0.89	Post-expansion

ABW: alar base width; AW: alar width; MW: mouth width; PW: philtrum width; HofN: height of nose; NL: nasolabial angle; HofUL: height of upper lip; HofVUL: height of vermillion of upper lip; HofLL: height of lower lip; LFH: lower facial height; ULtoE: upper lip to E-line; LLtoE: lower lip to E-line; NTP: nasal tip prominence; ICW: intercanthal width.

In comparison, the lowest ICC for comparison between CBCT and 3D facial scans was 0.65 (95% CI, 0.06–0.90). The measurement errors in millimeters were calculated as an average value of within-subject standard deviations, and the highest was 0.35 mm for 3D facial scans and 0.50 for CBCTs.

Mean and 95% CI are described in table IV. At T0 the mean valuesindicating the difference between CBCT and 3D facialscan measurements ranged from 0.01–1.38 mm and similarly, at T1, the mean values ranged from 0.08–1.21 mm.

Average percentages and 95% CI are described in table V. Some measurements showed slightly higher percentage changes for the control group as opposed to the treatment group. For example, alar base width (ABW) mean percentage change was 4.92% in the control group whereas it was slightly lower in the treatment group at 4.08%. However, it is important to note that the mean percentage difference between the two groups was only 0.84%, which is very minimal.

In table V, for the 3D facial scanning modality, in the treatment group, the mean percentage change for the U lip to E-line was –47.54% with a standard deviation of 149.98%, a minimum of –553.85%, and a maximum of 61.83%. The mean percentage change seen for the L lip to E-line in the same group was –46.09%, with a standard deviation of 116.58%, a minimum of –456.67% and a maximum of 36.41%.

Table VI presents descriptive analyses summarizing the change in measurements over time for each of the 14 measurements by the two modalities. Negative values indicate decreases in outcomes and positive are increases. When evaluating the data in table VI, the mean values presented are nearly 1 mm on average for the linear measurements, and the mean changes in soft

TABLE V

Descriptive statistics for percentage change in 3D facial scan and CBCT measurements by study groups

Group		Mean	Standard deviation	Minimum	Maximum	95.0% lower CL for mean	95.0% upper CL for mean	Assessment method
Control	ABW % change	3.66	2.50	–0.60	8.78	2.27	5.04	3D facial scan
	AW % change	1.73	2.81	–3.55	6.42	0.17	3.29	3D facial scan
	MW % change	3.12	2.88	–0.85	8.16	1.53	4.71	3D facial scan
	PW % change	10.60	9.86	–5.51	31.82	5.14	16.06	3D facial scan
	HofN % change	2.56	2.55	–1.11	8.18	1.15	3.98	3D facial scan
	NLangle % change	–0.46	1.50	–2.80	2.05	–1.29	0.37	3D facial scan
	HofUL % change	3.87	3.56	–2.01	8.79	1.90	5.84	3D facial scan
	HofVUL % change	13.94	11.76	–1.67	36.48	7.43	20.46	3D facial scan
	HofLL % change	5.21	2.02	1.23	7.89	4.09	6.33	3D facial scan
	LFH % change	3.26	1.67	0.21	6.07	2.33	4.18	3D facial scan
	UliptoE % change	42.96	66.44	–46.94	197.10	6.17	79.76	3D facial scan
	LliptoE % change	–8.83	63.66	–177.89	74.42	–44.08	26.42	3D facial scan
	NTP % change	5.87	4.02	–2.76	10.17	3.64	8.10	3D facial scan
	ICW % change	1.52	1.57	–0.52	4.33	0.65	2.39	3D facial scan
Treatment	ABW % change	4.02	4.06	–0.35	11.16	1.77	6.27	3D facial scan
	AW % change	2.62	3.22	–0.90	7.57	0.83	4.40	3D facial scan
	MW % change	3.80	2.92	–1.23	9.27	2.18	5.42	3D facial scan
	PW % change	10.35	8.95	–4.16	25.62	5.39	15.30	3D facial scan
	HofN % change	1.61	3.06	–2.81	6.67	–0.08	3.30	3D facial scan
	NLangle % change	–1.65	1.88	–3.26	2.91	–2.69	–0.61	3D facial scan
	HofUL % change	5.86	6.83	–4.64	25.01	2.07	9.64	3D facial scan
	HofVUL % change	8.23	10.89	–10.57	29.37	2.20	14.26	3D facial scan
	HofLL % change	3.26	3.26	–2.38	11.99	1.46	5.07	3D facial scan
	LFH % change	2.34	1.66	–0.31	5.05	1.42	3.26	3D facial scan
	UliptoE % change	–47.54	149.98	–553.85	61.83	–130.60	35.51	3D facial scan
	LliptoE % change	–46.09	116.58	–456.67	36.41	–110.65	18.47	3D facial scan
	NTP % change	4.71	3.07	0.29	9.48	3.01	6.41	3D facial scan
	ICW % change	1.18	0.92	–0.20	3.23	0.68	1.69	3D facial scan

TABLE V (Continued).

Group		Mean	Standard deviation	Minimum	Maximum	95.0% lower CL for mean	95.0% upper CL for mean	Assessment method
Control	ABW % change	4.92	3.00	–1.18	10.34	3.26	6.59	CBCT
	AW % change	2.56	2.32	0.16	8.20	1.28	3.85	CBCT
	MW % change	2.59	3.52	–3.75	7.56	0.64	4.54	CBCT
	PW % change	11.23	10.08	–3.27	28.16	5.65	16.82	CBCT
	HofN % change	3.20	2.95	–1.18	10.65	1.56	4.83	CBCT
	NLangle % change	–0.15	2.07	–3.36	4.73	–1.30	0.99	CBCT
	HofUL % change	3.54	4.18	–3.42	9.03	1.23	5.86	CBCT
	HofVUL % change	13.85	12.43	–0.62	41.64	6.96	20.73	CBCT
	HofLL % change	5.12	2.85	1.14	12.77	3.55	6.70	CBCT
	LFH % change	3.09	2.10	–0.29	7.82	1.93	4.25	CBCT
	UliptoE % change	80.67	159.71	–60.39	582.35	–7.77	169.12	CBCT
	LliptoE % change	–3.99	67.59	–178.57	93.00	–41.43	33.44	CBCT
	NTP % change	5.93	4.32	–1.49	15.30	3.54	8.33	CBCT
Treatment	ABW % change	4.08	3.27	0.22	9.91	2.27	5.89	CBCT
	AW % change	2.84	3.08	–2.31	8.42	1.14	4.55	CBCT
	MW % change	3.74	3.70	0.31	13.41	1.70	5.79	CBCT
	PW % change	9.70	7.18	–0.58	20.70	5.72	13.68	CBCT
	HofN % change	1.72	2.86	–2.79	6.11	0.14	3.30	CBCT
	NLangle % change	–1.61	1.93	–3.33	2.59	–2.68	–0.54	CBCT
	HofUL % change	6.58	6.36	–6.55	21.87	3.06	10.10	CBCT
	HofVUL % change	9.53	11.97	–9.41	37.38	2.90	16.16	CBCT
	HofLL % change	3.96	4.49	–2.50	16.37	1.47	6.44	CBCT
	LFH % change	2.48	1.80	–0.08	5.97	1.48	3.48	CBCT
	UliptoE % change	–72.12	255.22	–975.00	56.59	–213.45	69.21	CBCT
	LliptoE % change	–34.95	98.17	–379.07	34.10	–89.32	19.41	CBCT
	NTP % change	4.66	3.52	–1.01	11.27	2.71	6.62	CBCT
	ICW % change	1.33	1.29	–1.18	3.04	0.62	2.05	CBCT

TABLE VI Changes in facial soft tissue measurements in the control and treatment groups, n = 15

Measurement	Control group (n = 15)
	3D facial scan		CBCT
	M W SD	[Min, max] (95% CI)	M W SD	[Min, max] (95% CI)
Alar base width (ABW)	1.12 0.76	[–0.16, 2.57] (0.70, 1.54)	1.41 0.78	[–0.29, 2.58] (0.98, 1.85)
Alar width (AW)	0.55 0.94	[–1.22, 2.41] (0.03, 1.07)	0.81 0.72	[0.05, 2.55] (0.41, 1.20)
Mouth width (MW)	1.26 1.14	[–0.34, 3.22] (0.63, 1.90)	1.01 1.39	[–1.57, 3.22] (0.24, 1.78)
Philtrum width (PW)	0.91 0.77	[–0.56, 2.17] (0.48, 1.34)	0.95 0.81	[–0.33, 2.27] (0.50, 1.40)
Height of nose (HofN)	1.06 1.03	[–0.46, 3.17] (0.49, 1.63)	1.29 1.14	[–0.46, 3.97] (0.66, 1.92)
Nasolabial angle (NL)	–0.60 1.76	[–3.56, 2.43] (–1.57, 0.37)	–0.27 2.24	[–4.30, 4.20] (–1.51, 0.97)
Height of upper lip (HofUL)	0.83 0.76	[–0.37, 2.01] (0.40, 1.25)	0.73 0.85	[–0.65, 1.82] (0.26, 1.20)

TABLE VI (Continued).

Measurement	Control group (n = 15)
	3D facial scan		CBCT
	M W SD	[Min, max] (95% CI)	M W SD	[Min, max] (95% CI)
Height of vermillion of upper lip (HofVUL)	0.92 W 0.70	[–0.08, 2.32] (0.54, 1.31)	0.97 W 1.02	[–0.03, 3.31] (0.41, 1.54)
Height of lower lip (HofLL)	2.21 W 0.87	[0.62, 3.61] (1.73, 2.69)	2.11 W 1.22	[0.55, 5.54] (1.44, 2.78)
Lower facial height (LFH)	2.12 W 1.13	[0.11, 4.17] (1.50, 2.75)	1.94 W 1.37	[–0.21, 5.15] (1.18, 2.70)
Upper lip to E-line (ULtoE)	0.19 W 0.79	[–1.16, 1.36] (–0.25, 0.63)	0.15 W 1.01	[–1.38, 1.98] (–0.40, 0.71)
Lower lip to E-line (LLtoE)	0.15 W 0.97	[–1.69, 2.09] (–0.39, 0.69)	0.32 W 1.18	[–2.00, 2.39] (–0.33, 0.97)
Nasal tip prominence (NTP)	1.47 W 0.96	[–0.65, 2.53] (0.94, 2.00)	1.47 W 0.99	[–0.34, 3.54] (0.93, 2.02)
Intercanthal width (ICW)	0.50 W 0.52	[–0.17, 1.40] (0.21, 0.79)	0.82 W 0.66	[–0.29, 1.81] (0.45, 1.18)
	Treatment group (n = 15)
Alar base width (ABW)	1.21 1.22	[–0.12, 3.36](0.53, 1.88)	1.24 0.99	[0.07, 3.14] (0.69, 1.79)
Alar width (AW)	0.87 1.06	[–0.29, 2.57] (0.29, 1.46)	0.93 1.02	[–0.84, 2.83] (0.36, 1.49)
Mouth width (MW)	1.60 1.16	[–0.55, 3.45] (0.95, 2.24)	1.51 1.37	[0.14, 4.92] (0.75, 2.27)
Philtrum width (PW)	0.96 0.83	[–0.42, 2.65] (0.50, 1.42)	0.95 0.70	[–0.05, 2.32] (0.56, 1.33)
Height of nose (HofN)	0.68 1.33	[–1.28, 2.57] (–0.06, 1.42)	0.73 1.25	[–1.34, 2.69] (0.03, 1.42)
Nasolabial angle (NL)	–1.93 2.19	[–3.87, 3.34] (–3.14, –0.71)	–1.89 2.26	[–3.90, 3.10] (–3.14, –0.64)
Height of upper lip (HofUL)	1.16 1.23	[–1.04, 4.19] (0.48, 1.84)	1.26 1.16	[–1.41, 3.68] (0.62, 1.90)
Height of vermillion of upper lip (HofVUL)	0.52 0.64	[–0.72, 1.68] (0.17, 0.88)	0.66 0.74	[–0.84, 1.97] (0.25, 1.07)
Height of lower lip (HofLL)	1.35 1.31	[–1.23, 4.55] (0.63, 2.08)	1.59 1.73	[–1.29, 6.03] (0.63, 2.54)
Lower facial height (LFH)	1.50 1.03	[–0.21, 3.21] (0.93, 2.08)	1.58 1.17	[–0.05, 3.94] (0.93, 2.23)
Upper Lip to E-line (ULtoE)	–0.23 0.80	[–1.85, 1.03] (–0.67, 0.21)	–0.30 0.71	[–1.81, 0.67] (–0.69, 0.09)
Lower Lip to E-line (LLtoE)	–0.28 0.90	[–1.64, 0.89] (–0.78, 0.22)	–0.30 0.89	[–1.90, 0.89] (–0.80, 0.19)
Nasal tip prominence (NTP)	1.20 0.75	[0.09, 2.38] (0.78, 1.61)	1.21 0.89	[–0.27, 2.83] (0.71, 1.70)
Intercanthal width (ICW)	0.40 0.33	[–0.06, 1.15] (0.22, 0.58)	0.43 0.41	[–0.36, 0.98] (0.21, 0.66)

M: mean; SD: standard deviation.

tissue facial measurements for 3D facial scans are similar to those measurements for CBCT imaging. When reviewing the values in table VI, it may suggest that changes occurred in a similar way in both control and treatment groups. In the treatment group, the average increase is also about 1 mm.

According to the MANOVA test results demonstrating P < 0.001, there are statistically significant differences in the mean facial soft tissue measurements jointly between CBCTs and 3D facial scans at pre-treatment (T0) and posttreatment (T1). There is no statistically significant difference between treatment and control groups from T0 to T1 utilizing 3D facial scan soft tissue measurements and CBCT measurements alike.

Discussion

At the time of thisstudy, there were a limited number of existing studies that included a control group, which would be beneficial in identifying any potential effect on the facial soft tissues from natural growth; thereby, this was an important factor to consider in this study [2,6,10,12,13,22].

A study by Aljawad et al. compared the two different imaging modalities with respect to soft tissue measurements and analyses [23]. The authors found and concluded that the soft tissue surface differences on average were less than 1 mm [23]. In the study by Toma et al., it was found that most of the 21 facial landmarks that were identified were within 1 mm and considered acceptable, with a range from 0.39 to 1.49 mm [24]. The author of this study found it prudent that, based on the current body of available evidence, variations in measurements between the two imaging modalities for outcome variables less than 1 mm are clinically acceptable with respect to accuracy and validity of comparison [23–28].

When landmarking to determine the ABW measurements for both modalities, the placement of measuring landmarks was more subjective as opposed to the placement of measuring landmarks for other variables. The presence of patient

Figure 3 3D face. a: 3D facial scan (OrthoInsight 3D); b: CBCT (3D slicer)

positioning errors, patients not having a relaxed lip posture of neutral facial expression, and potential errors in image orientations could have further contributed to the limitations. Given the younger age of the patients, some patients may have inadvertently not maintained a neutral facial expression when biting down in maximum intercuspation, and thereby affected the mouth width measurements in particular. An example of this isillustrated in figure 3a and b, wherein in the 3D facialscan, the patient has maintained a neutral facial expression but in the CBCT image of the same patient at the same observation timepoint, the facial expression is no longer neutral when in maximum intercuspation.

When comparing the percentage change for one particular outcome variable for both treatment and control groups, the percentage changes were similar in value. This finding is quite comparable to that found in the study by Truong et al. which showed that the treatment group underwent a total change in ABW of 1.95 1.8 mm while the control group underwent a total change in ABW of 1.29 1.4 mm [14]. These changes were not statistically significant, and due to the arithmetic closeness of the differences seen in the treatment and control groups, the authors declared that the effect of RME on this soft tissue outcome variable, among many others, was not clinically significant [14]. Interestingly, Torun et al. found that from the beginning of RME therapy to six months post-retention, the difference in ABW over time was only 0.5 mm for the postpubertal group and 1 mm for the prepubertal group [7].

All the measurements demonstrated positive changes over time, except for the nasolabial angle in both treatment and control groups; and the position of upper and lower lips to E-line in the treatment group. The latter demonstrated decreases in the angle and an overall retruded position of the upper and lower lip and is similar to findings in other previously conducted studies [2,7,12]. This decrease in values may potentially be explained by the lip being stretched with expansion and thereby decreasing in thickness, as also reported by Kim and Lagravère [29].

With respect to the soft tissue measurements of the upper and lower lip to E-line, a study by Halıcıog?lu and Yavuz found that both measurements decreased by approximately 1 mm. Then after retention (average of 6.42 months), measurements were similar to pre-expansion values [30]. Similarly, Huang et al. found that from pre-expansion to post-retention evaluating two relevant studies, the effect estimate mean difference was –0.11 mm for the upper lip to E-line measurement and 0.42 mm for the lower lip to E-line measurement and thereby non-significant, similar to this study [2]. Therefore, the authors concluded that RME likely did not cause clinically important changes in the relationships of the upper and lower lips to the E-line. Any changes that may have been caused acutely by RME post-expansion quickly and significantly relapsed following retention, and this relapse was likely due to maxillary and mandibular movement and rotation [2].

Comparing mean changes in facial soft tissue measurements between the treatment and control groups reveals minimal differences, generally less than 1 mm, further suggesting the clinically insignificant effects of RME therapy on facial soft tissues. In comparison to this finding, the study by Truong et al. found that, for the height of the nose, the treatment group underwent an increase of only 0.34 mm immediately post-expansion which then increased to 4.39 mm over 2.84 years. Meanwhile the control group underwent an increase of only 2.87 mm over 2.25 years. This difference of 1.52 mm between the groups wasfound to be statistically non-significant [8]. Truong et al. concluded in this study that in the long term, any gains seen in the treatment group as opposed to the control group were clinically similar. Additionally, the authors supported the idea that REM did not produce differences in soft tissue measurements between treated and untreated patients [8]. When considering the lower facial third, previous studies have indicated that the mandible rotates downwards and backwards with RME, and similarly, this pattern is also seen with growth and development [1,12,31]. This may lead to a subsequent increase in the lower facial height or lower lip height as well as soft tissue related changes in the nose and lips. In this study, there were no significant differences between the treatment and control groups, when considering both modalities. These findings are supported by the results of the review by Huang et al., in which the mean lower facial height changed by 0.42 mm and the mean lower lip height changed by 0.48 mm from pre-expansion to post-retention and were not statistically significant [2]. However, in this study, given the limitations regarding imaging protocols, analysis and limited sample size, the results are to be interpreted with caution.

Conclusion

Children aged 7–11 years treated with maxillary transverse deficiency with RME experience facialsoft tissue changessimilar Original article

to those of patients without any expansion over a period of one year.

Funding : This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Authors' contributions : N.M. analyzed and interpreted the patient data regarding the expansion outcomes and three-dimensional measures and was a major contributor in writing the manuscript; R.Q.C. assisted in three-dimensional measurements, data analysis and writing of the manuscript; G.H. assisted in data and statistical analysis; M.L. contributed with the research design, patient recruitment, data analysis and manuscript revision. All authors read and approved the final manuscript.

Data availability : The datasets used and/or analysed during the current study are available from the corresponding author upon reasonable request.

Human ethics and consent to participate : This research study was conducted at the orthodontic graduate clinic at the University of Alberta with ethics approval from the Research Ethics Board (pro00061538) from the University of Alberta.

Disclosure of interest : The authors declare that they have no competing interests.

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