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Introduction: The early diagnosis of mandibular asymmetry (MA) in patients with unilateral cleft lip and palate (UCLP) can contribute to its treatment., Objective: The aim of this study was to evaluate the occurrence and the extent of MA in UCLP patients at different growth stages., Methods: Cone-beam computed tomography (CBCT) of 47 UCLP patients were included, and divided into two groups (prepubertal stage and pubertal stage). The mandibular ramus height (Co-Go), mandibular body length (Go-Me), total mandibular length (Co-Me), gonial angle (CoGoMe), the volume of the mandibular condyles, and lateral chin deviation were evaluated. The cleft side (CS) and noncleft side (NCS) were compared using the paired t-test for dependent samples. Chin deviation and its possible association with specific sides were evaluated using the Mann-Whitney and Fisher's Exact tests, respectively. The significance level was set at 5%., Results: Comparison of CS and NCS revealed that in prepubertal stage, Co-Me was shorter (105.5 ± 5.7 mm; p = 0.036) in the CS, and that in pubertal stage, Co-Go was lower (46 ± 6 mm; p= 0.004) and Go-Me was greater (78.5 ± 5.8 mm; p = 0.026) in the CS. In both growth stages, a significant association (p< 0.05) was observed between the side to which the chin has deviated and the CS., Conclusions: Although patients with UCLP in the prepubertal and pubertal stages presented significant measurements revealing MA, only Co-Go in the pubertal stage showed a clinically relevant difference. This specific result indicates that MA must be monitored during patients' growth.

Background: Facial symmetry severely affects appearance and function. Large numbers of patients seek orthodontic treatment to improve facial symmetry. However, the correlation between hard- and soft-tissue symmetry is still unclear. Our aim was to investigate the hard- and soft-tissue symmetry in subjects with different levels of menton deviation and sagittal skeletal classes with 3D digital analysis and to investigate the relationship between the entire and individual hard- and soft-tissues., Methods: A total of 270 adults (135 males and 135 females) consisting of 45 subjects of each sex in each sagittal skeletal classification group. All subjects were further classified into relative symmetry (RS), moderate asymmetry (MA) and severe asymmetry (SA) groups based on the degree of menton deviation from the mid-sagittal plane (MSP). The 3D images were segmented into anatomical structures and mirrored across the MSP after establishing a coordinate system. Original and mirrored images were registered by a best-fit algorithm, and the corresponding root mean square (RMS) values and colormap were obtained. The Mann‒Whitney U test and Spearman correlation were conducted for statistical analysis., Results: The RMS increased with greater deviations with regard to the deviation of the menton in most of anatomical structures. Asymmetry was represented in the same way regardless of sagittal skeletal pattern. The soft-tissue asymmetry had a significant correlation with dentition in the RS group (0.409), while in the SA group, it was related to the ramus (0.526) and corpus (0.417) in males and was related to the ramus in the MA (0.332) and SA (0.359) groups in females., Conclusions: The mirroring method combining CBCT and 3dMD provides a new approach for symmetry analysis. Asymmetry might not be influenced by sagittal skeletal patterns. Soft-tissue asymmetry might be reduced by improving the dentition in individuals with RS group, while among those with MA or SA, whose menton deviation was larger than 2 mm, orthognathic treatment should be considered., (© 2023. The Author(s).)

The purpose of this study was to compare the efficacy of botulinum toxin (BoNT) in masseter muscle reduction depending on the amount of chin deviation. Exploring distinctive effects of BoNT relative to the characteristics of facial asymmetry will aid in planning and predicting treatment outcomes. Sixteen adult volunteers were classified into two groups according to the degree of menton deviation observed in posteroanterior cephalograms. Eight had a menton deviation of 3 mm or more and the other eight had less than 3 mm. A total of 25 Units of BoNT was injected into the unilateral masseter muscle of the prominent side for each participant. Changes in the volume and bulkiest height of the lower face on each side were measured with a 3D laser scan at four time points: before and 4, 8, and 12 weeks after the injection. Two-way mixed ANOVA was employed for analyses. The volume and bulkiest height of the injected side decreased over time in both types of asymmetry, with significant differences at each time point. The reductions in the volume and bulkiest height were significantly greater in subjects without chin deviation. The reductions in the volume and bulkiest height of the lower face using BoNT are more effective for subjects without chin deviation.

Introduction: The purposes of this study were to (1) evaluate facial asymmetry 3 dimensionally using cone-beam computed tomography (CBCT) and (2) compare the right and left facial hard and soft tissues volumetrically and their interferences on each other., Methods: The CBCT data of 49 asymmetric (soft tissue menton deviation, ≥4 mm; distance from the facial midline) (mean age, 19.9 ± 5.6 years) and 39 symmetric patients (soft tissue menton deviation, <4 mm) (mean age, 17.8 ± 5.5 years) were exported to the MIMICS software program (version 13.0; Materialise, Leuven, Belgium). Linear, surface distance, angular, volumetric, and surface area measurements were performed 3 dimensionally to assess and compare intragroup and intergroup differences., Results: In the asymmetry group, linear measurements such as ramus height, mandibular effective and corpus length, and absolute mandibular volumetric measurements were significantly decreased (P <0.001), whereas facial mandibular, and soft and hard tissue volumetric measurements made on 3-dimensional images, and linear measurements on 2-dimensional images were increased (P <0.001) on the deviation side., Conclusions: Facial hard and soft tissue asymmetries can be precisely quantified using CBCT. However, especially in the gonial region where the surface topography shows alterations caused by asymmetry, many anatomic landmarks should be chosen for the assessment of asymmetry. At the gonial level, the compensation of the soft tissues for the hard tissues was found on 2-dimensional images; nevertheless, 3-dimensional right and left volumetric soft tissue evaluations provide evidence for asymmetry., (Copyright © 2016 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.)

Sagittal split ramus osteotomy (SSRO) benefits patients through the wide bone contact between the proximal and distal segment, which contributes to postoperative stability. Recently, a posterior bending osteotomy (PBO), an additional vertical osteotomy performed posterior to the second molar after SSRO, has been introduced to avoid positional changes of the condyle from bony interference in patients with facial asymmetry, which leads to decreases in bone contact. The aim of this study was to investigate postoperative stability after SSRO with PBO. Forty patients with facial asymmetry were enrolled and divided into two groups according to the surgical method used on the deviated side: PBO (n = 18) and grinding method (n = 22). Cephalometric analysis was performed. In addition, adaptation and bone healing of the PBO segments were assessed with 3-month postoperative three-dimensional computed tomography depending on the fixation of the PBO segment. The two groups showed no significant difference in postoperative relapse. Most PBO segments were well-adapted to the proximal segment. Twelve segments with fixation exhibited good bone healing. Two of three segments without fixation, however, had poor bone healing. In summary, PBO did not cause postoperative instability, and the PBO segments were well-healed with rigid fixation., (Copyright © 2013 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.)

Introduction: Lateral cephalometric radiographs are traditionally required for orthodontic treatment, yet rarely used to assess asymmetries., Objective: The objective of the present study was to use lateral cephalometric radiographs to identify existing skeletal and dentoalveolar morphological alterations in Class II subdivision and to compare them with the existing morphology in Class I and II relationship., Material and Methods: Ninety initial lateral cephalometric radiographs of male and female Brazilian children aged between 12 to 15 years old were randomly and proportionally divided into three groups: Group 1 (Class I), Group 2 (Class II) and Group 3 (Class II subdivision). Analysis of lateral cephalometric radiographs included angular measurements, horizontal linear measurements and two indexes of asymmetry that were prepared for this study., Results: In accordance with an Index of Dental Asymmetry (IDA), greater mandibular dental asymmetry was identified in Group 3. An Index of Mandibular Asymmetry (IMA) revealed less skeletal and dental mandibular asymmetry in Group 2, greater skeletal mandibular asymmetry in Group 1, and greater mandibular dental asymmetry in Group 3., Conclusion: Both IDA and IMA revealed greater mandibular dental asymmetry for Group 3 in comparison to Groups 1 and 2. These results are in accordance with those found by other diagnostic methods, showing that lateral cephalometric radiography is an acceptable method to identify existing skeletal and dentoalveolar morphological alterations in malocclusions.

Objective: To investigate discrepancies in results of facial asymmetry analysis using different cone beam computed tomography (CBCT) image reorientation methods and the effectiveness of soft tissue as a reorientation reference for analysis of facial asymmetry., Materials and Methods: An asymmetric group of 30 patients with 4 mm or more of chin point (menton [Me]) deviation and a symmetric group of 30 patients with less than 4 mm of deviation of Me were chosen as study subjects. Three orientation methods were used to calculate and compare Me deviation values of the 60 subjects. Two methods used only skeletal landmarks for reference, and one method included the soft tissue landmarks around the eye. Preferences of an expert group for the facial midline as determined by each reorientation method were also examined., Results: The examinations showed significant discrepancies in Me deviation values between the three reorientation methods. The expert group showed the greatest preference for the facial midline reorientation method that incorporated soft tissue landmarks of the eye., Conclusions: These study findings suggest that the inclusion of soft tissue landmarks, especially those around the eyes, is effective for three-dimensional CBCT image reorientation for facial asymmetry analysis.

Introduction: The purpose of this study was to determine whether Angle Class II subdivision malocclusions have skeletal or dental asymmetries between the Class II and Class I sides., Methods: A sample of 54 untreated Angle Class II subdivision patients with pretreatment photos and cone-beam computed tomography (CBCT) scans was used. The photos were used to identify the Class II subdivision malocclusion and to record the amount of crowding per quadrant. Landmarks were plotted on each CBCT volume so that direct 3-dimensional measurements could be made to compare the positions and dimensions of the skeletal and dental structures on the Class II side vs the Class I side., Results: Significant differences were found for 2 skeletal measurements: the position of the maxilla relative to the cranial base, and the mandibular dimension from the mandibular foramen to the mental foramen. Statistically significant dental differences were found for the position of the mandibular first molars and canines in relation to the maxilla and the mandible. Statistically significant differences were found for the maxillary first molars and canines in relation to the mandible., Conclusions: There were significant skeletal and dental differences between the Class I and Class II sides. The dental asymmetries accounted for about two thirds of the total asymmetry., (Copyright © 2013 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.)

Objectives: The three-dimensional (3D) asymmetric structure of the mandible makes it necessary to analyze both its size and angle. Currently the developing 3D analysis techniques are not able to perform the simultaneous linear and angular measurements. Our aim was to evaluate mandibular asymmetry using a vector-based system by constructing 3D vectors for the mandibular functional units., Material and Methods: We analyzed the 3D computed tomography images of normal control (N = 27) and asymmetric mandibles (N = 40). We created 3D vectors for the condylar, coronoid, body, gonial, and symphyseal functional units and compared the corresponding pairs of 3D vectors by calculating vector operations., Results: The vector difference and other vector components represented the individual 3D architectural pattern and severity of the asymmetric mandible. The body unit contributed most to mandibular asymmetry followed by the condylar unit., Conclusions: The results indicate that 3D vector analysis can improve our understanding of the 3D architecture of asymmetric mandibles. This type of 3D vector analysis can be a useful tool for the comprehensive evaluation of its asymmetric mandibular structure., (Copyright © 2012 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.)

The aim of this study was to evaluate and compare postero-anterior (PA) cephalograms and cone-beam computed tomography (CBCT) images for the detection of mandibular asymmetry. Six asymmetric anonymous dry human skulls with visible chin deviation were available for this study. Metallic markers were glued on the anatomical landmarks to avoid identification error. PA cephalograms and CBCT scans were made by means of a standardized set-up. Each scan and cephalogram was measured three times by a single observer and the means used for analysis. Asymmetry was defined by the subtraction of the left side and right side measurements. CBCT was reliable [intraclass correlation coefficient (ICC) > 0.957] and very accurate (within 0.5 mm) in detection of all asymmetry. PA cephalograms were not accurate in detection of asymmetry of the mandibular ramus length, the mandibular body length, and the total mandibular length. PA cephalograms were the least reliable in determining the mandibular body length asymmetry (ICC = 0.686). The use of CBCT to detect mandibular asymmetry was validated with this study. CBCT images are very reliable and accurate for the detection of asymmetry and should be considered over conventional PA cephalometry when a chin deviation is present.

Aim: The purpose of this study was to evaluate the use of the Levandoski Panoramic Analysis in the diagnosis of dental and mandibular asymmetries and its contribution to clinical patient's evaluation and treatment planning. MATERIALS AND METHODS: Thirty-one randomly selected panoramic radiographs of children from 7 to 14 year old were analysed using 10 linear measurements. Right and left values were compared with Student's paired T tests. For each value, mean and standard deviation were computed separately for each side., Results: Statistics. A dominance for the left side over the right side was observed. The data obtained were not statistically significant with the exception of maxillary length: the right side length of the maxilla was shorter (p<0.05) compared to the left side., Conclusions: Levandosky Panoramic Analisys represents a useful screening method in the diagnosis of dental and mandibular asymmetries.

Introduction: The purpose of this study was to use cone-beam computed tomography to compare mandibular dimensions in subjects with asymmetric skeletal Class III malocclusion and those with normal occlusion., Methods: Cone-beam computed tomography scans of 38 subjects with normal occlusion and 28 patients with facial asymmetry were evaluated and digitized with Invivo software (Anatomage, San Jose, Calif). Three midsagittal and 13 right and left measurements were taken. The paired t test was used to compare the right and left sides in each group. The Mann-Whitney U test was used to compare the midsagittal variables and the differences between the 2 sides of the group with normal occlusion with those of asymmetry patients., Results: The posterior part of the mandibular body showed significant differences between the deviated and nondeviated sides in asymmetric Class III patients. The difference of the asymmetry group was significantly greater than that of the normal occlusion group for the mediolateral ramal and the anteroposterior condylar inclinations (P = 0.007 and P = 0.019, respectively)., Conclusions: The asymmetric skeletal Class III group showed significant differences in condylar height, ramus height, and posterior part of the mandibular body compared with the subjects with normal occlusion. These results might be useful for diagnosis and treatment planning of asymmetric Class III patients., (Copyright © 2012 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.)

Purpose: A systematic classification is needed for the diagnosis and surgical treatment of facial asymmetry. The purposes of this study were to analyze the skeletal structures of patients with facial asymmetry and to objectively classify these patients into groups according to these structural characteristics., Patients and Methods: Patients with facial asymmetry and recent computed tomographic images from 2005 through 2009 were included in this study, which was approved by the institutional review board. Linear measurements, angles, and reference planes on 3-dimensional computed tomograms were obtained, including maxillary (upper midline deviation, maxilla canting, and arch form discrepancy) and mandibular (menton deviation, gonion to midsagittal plane, ramus height, and frontal ramus inclination) measurements. All measurements were analyzed using paired t tests with Bonferroni correction followed by K-means cluster analysis using SPSS 13.0 to determine an objective classification of facial asymmetry in the enrolled patients. Kruskal-Wallis test was performed to verify differences among clustered groups. P < .05 was considered statistically significant., Results: Forty-three patients (18 male, 25 female) were included in the study. They were classified into 4 groups based on cluster analysis. Their mean age was 24.3 ± 4.4 years. Group 1 included subjects (44% of patients) with asymmetry caused by a shift or lateralization of the mandibular body. Group 2 included subjects (39%) with a significant difference between the left and right ramus height with menton deviation to the short side. Group 3 included subjects (12%) with atypical asymmetry, including deviation of the menton to the short side, prominence of the angle/gonion on the larger side, and reverse maxillary canting. Group 4 included subjects (5%) with severe maxillary canting, ramus height differences, and menton deviation to the short side., Conclusion: In this study, patients with asymmetry were classified into 4 statistically distinct groups according to their anatomic features. This diagnostic classification method will assist in treatment planning for patients with facial asymmetry and may be used to explore the etiology of these variants of facial asymmetry., (Copyright © 2012 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.)

3D image technology provides a very effective tool for evaluating, characterising, and drawing up the surgical treatment plan for potential orthognathic surgery patients. Patients with dysmorphic syndromes or incorrect jaw positions frequently show facial asymmetry. The objective of this cross-sectional survey is to evaluate facial asymmetry by means of three-dimensional computed tomography (CT) reconstructions. Twenty one consecutive patients were diagnosed using a CT scan. 3D reconstructions of the patients' skulls were made and then measurements taken of different craniometric landmarks and of the various structures presenting asymmetry. The gonion emerged as the most asymmetrical point in all subjects, and the anterior nasal spine showed least deviation. The t test produced statistically significant differences (p < 0.05) between symmetric and asymmetric patients at all landmarks. The lateral inclination of the mandibular ramus was shown to present the greatest asymmetrical deviation, followed by the frontal inclination of the mandibular ramus. The angulation of the mandibular ramus, on both frontal and lateral planes, determines apparent facial asymmetry, as well as conditioning the surgical treatment plan for patients with craniofacial asymmetry.

Introduction: The purpose of this study was to investigate the dimensional changes in each skeletal unit in the mandibles of patients with facial asymmetry and mandibular prognathism., Methods: The patients consisted of 50 adults with mandibular prognathism, divided into the symmetry group (n = 20) and the asymmetry group (n = 30) according to the degree of menton deviation. Three-dimensional computed tomography scans were obtained with a spiral computed tomography scanner. Landmarks were designated on the reconstructed 3-dimensional surface models. The lines to represent condylar, coronoid, angular, body, and chin units were used. Ramal and body volumes were measured in the hemi-mandibles., Results: In the asymmetry group, condylar and body unit lengths were significantly longer, and coronoid unit length was significantly shorter on the nondeviated side than on the deviated side (P <0.01). Angular and chin unit lengths were not significantly different between the 2 sides (P >0.05). Ramal volume was significantly greater on the nondeviated side (P <0.01), but body volume was not significantly different between the 2 sides (P >0.05)., Conclusions: Both condylar and body units appeared to contribute to mandibular asymmetry, with a more central role of the condylar unit., (Copyright © 2010 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.)

Introduction: The objective of this study was to compare the degrees of skeletal and dental asymmetry between subjects with Class II subdivision malocclusions and subjects with normal occlusions by using cone-beam computed tomography., Methods: Thirty subjects with Angle Class II subdivision malocclusions (mean age, 13.99 years) and 30 subjects with normal occlusions (mean age, 14.32 years) were assessed with 3-dimensional cone-beam computed tomography scans. Independent t tests were used to compare orthogonal, linear, and angular measurements between sides and between groups., Results: Total mandibular length and ramus height were shorter on the Class II side. Pogonion, menton, and the mandibular dental midline were deviated toward the Class II side. Gonion and the anterior condyle landmark were positioned more posteriorly on the Class II side. The mandibular dental landmarks were located more latero-postero-superiorly, and the maxillary dental landmarks more latero-antero-superiorly on the Class II side. There was loss of maxillary arch length, and the mandibular molar was closer to the ramus on the Class II side., Conclusions: The etiology of Class II subdivision malocclusions is primarily due to an asymmetric mandible that is shorter and positioned posteriorly on the Class II side. A mesially positioned maxillary molar and a distally positioned mandibular molar on the Class II side are also minor contributing factors., (Copyright © 2010 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.)

Objective: Three-dimensional computed tomography (CT) was used to investigate which skeletodental factors are related to chin point deviation of facial asymmetry in skeletal class III malocclusion (SCIII) patients., Study Design: Forty Korean adult female patients with SCIII, who had a three-dimensional CT taken 1 month before orthognathic surgical surgery, were assigned to group 1 (symmetry) or group 2 (asymmetry) according to the amount of chin point deviation from facial midline. Midfacial, mandibular, and cranial base variables were measured with software and statistically analyzed., Results: Group 2 showed higher positions of the upper canine and first molar, shorter ramus height, more superior-posterior positioning of gonion (Go) on the deviated side, and more mesial inclination of the ramus and medial positioning of Go on the opposite side., Conclusion: Facial asymmetry in SCIII patients occurs due to greater growth and mesial inclination of the ramus and greater maxillary vertical excess in the opposite side.

This study intended to evaluate the morphological characteristics of the cranial base and maxillomandibular structures of facial asymmetry in adult patients, so as to determine whether mandibular asymmetry is a result of primary mandibular deformity or if it is influenced by cranial base deformity. Forty-two adult patients with dentofacial deformity were placed into two groups according to the deviation of the chin: Asymmetry group (n = 24) and Non-asymmetry group (n = 18). They were compared with three-dimensional (3D) CT reformatted images using a 3D visualization and analyzing program. The differences between the two groups, the correlation between the cranial base and maxillomandibular asymmetry were evaluated statistically. The degree of cranial base asymmetry in the Asymmetry group was not statistically different from the Non-asymmetry group. The asymmetric condyle position was found to be associated with skull base characteristics. The 3D position of the condyle and cranial base, however, was not closely related with mandibular asymmetry. The results showed that the cranial measurement variables were not the dominant factors that determined the degree of facial asymmetry. It seems that the mandibular skeletal factors itself, functional or intrinsic asymmetric growth potential, compensate or aggravate the influence of cranial asymmetry during the growth period.

Objective: The present study was undertaken to document whether mandibular length could be increased by distraction osteogenesis in children and what happens to the mandibular position 1 year after the distraction., Methods: Five patients with hemifacial microsomia (four unilateral, one bilateral) had distraction osteogenesis performed to lengthen the mandible. All patients had cephalometric and panoramic radiographs obtained before and 3, 6, and 12 months after the distraction osteogenesis., Results: The total mandibular length (Co-Gn) on the affected side was increased by 11.2 mm after the distraction and remained stable during a 1-year observation period. However, the increased mandibular length tended to move the chin downward (8 mm) more than forward (2 mm) during the same period., Conclusions: Distraction osteogensis can be used to lengthen the hypoplastic mandible. However, most of the increased mandibular length moved the chin downward more than forward.

Objective: The purpose of this study was to retrospectively investigate mandibular asymmetry in unilateral cleft lip and palate individuals (UCLP) in relation to chronologic age and in relation to lower facial asymmetry., Design: The longitudinal records of 34 UCLP individuals and 142 controls treated in the Department of Orthodontics, Eastman Dental Center, Rochester, NY, were included in the study. Posteroanterior and oblique cephalometric radiographs were analyzed for lower facial asymmetry and mandibular asymmetry, respectively. Mandibular asymmetry in UCLP was analyzed relative to three age groups (6-10, 11-14, and 15 or greater) and compared to controls. Moreover, mandibular asymmetry was analyzed relative to lower facial asymmetry., Results: UCLP individuals showed no significant differences in mandibular asymmetry compared to controls. In addition, no significant correlation was found between mandibular asymmetry and lower facial asymmetry in UCLP., Conclusions: The degree of mandibular asymmetry in UCLP appears not to be the major contributing factor to the lower facial asymmetry noted on these individuals. Possible cranial-base/temporal-region anomalies may be involved in unilateral cleft lip and palate and be responsible of the asymmetry noted in the lower facial skeleton.

The aim of the present investigation was to determine the relative extent of geometric error and errors in point identification in postero-anterior roentgenography. In one series of tests a group of dry human skulls was used, and the same cephalometric landmarks were identified twice by two orthodontists, using postero-anterior roentgenographs, first using the dry skulls as such, and then the same skulls with metal markers inserted to show the exact locations of the cephalometric points. Consistency and normal variation in the reproducibility of head position in the cephalostat between repeated roentgenographs were studied by a photographic technique in a group of young healthy adults, measuring the extent of minor head movements. Geometric error was calculated using a computer-aided design program (CAD) by rotating the three-dimensional co-ordinates of the cephalometric landmarks and thus obtaining projection error in the frontal view. Accuracy in cephalometric point identification was best in dental landmarks and vertical orientation of superior orbital margins. Geometric error was least when landmarks near the anterior midsagittal plane, such as upper and lower dental midlines or point gonion were compared with each other. Width measurements from frontal-view cephalograms are most sensitive to minor movements in head posture. Due to combined errors, the use of width measurements in facial asymmetry diagnosis should not be used since variance in errors in landmark identification can be larger than that in actual landmark location.