Three-dimensional cone beam computed tomographic image reorientation using soft tissues as reference for facial asymmetry diagnosis

Hemifacial microsomia: a scoping review on progressive facial asymmetry due to mandibular deformity

PURPOSE

This scoping review explores various parameters of the mandible in progressive facial asymmetry (FA) in hemifacial microsomia (HFM) patients, highlighting its relationship with sex, population, and age group.

METHODS

The review was based on a comprehensive search of PubMed, EBSCOhost, and Web of Science. Eligible studies that met the inclusion criteria form part of the selection study. The included studies were appraised using screening and quantitative criteria of mixed-method appraisal tools. The authors utilised a pre-set data extraction form to obtain information from the included studies.

RESULTS

Eleven studies met the inclusion criteria. The mandible parameters used were angular measurements, chin point, ramal height, body length, and total length. There was no relationship between FA and sex in HFM patients in the included studies. Most of the studies were comprised of European participants (55%), followed by Americans (36%) and Chinese (9%). The age groups included in the selected studies were categorised as dentition age (18%), early-to-middle childhood (18%), and varied ages (64%). The data presented in this review only pertains to the anomalous characteristics recorded on the affected side in HFM patients. No concomitant control data was recorded in this review.

CONCLUSION

An assessment of the included studies revealed that FA does not increase with age in HFM. Hence, FA is non-progressive in HFM patients. This information is relevant to diagnosing and managing HFM patients. More reports are needed on the progression of FA in HFM patients.

Automatic extraction of facial median sagittal plane for patients with asymmetry based on the EDMA alignment algorithm

BACKGROUND

We aimed to establish a novel method for automatically constructing three-dimensional (3D) median sagittal plane (MSP) for mandibular deviation patients, which can increase the efficiency of aesthetic evaluating treatment progress. We developed a Euclidean weighted Procrustes analysis (EWPA) algorithm for extracting 3D facial MSP based on the Euclidean distance matrix analysis, automatically assigning weight to facial anatomical landmarks.

METHODS

Forty patients with mandibular deviation were recruited, and the Procrustes analysis (PA) algorithm based on the original mirror alignment and EWPA algorithm developed in this study were used to construct the MSP of each facial model of the patient as experimental groups 1 and 2, respectively. The expert-defined regional iterative closest point algorithm was used to construct the MSP as the reference group. The angle errors of the two experimental groups were compared to those of the reference group to evaluate their clinical suitability.

RESULTS

The angle errors of the MSP constructed by the two EWPA and PA algorithms for the 40 patients were 1.39 ± 0.85°, 1.39 ± 0.78°, and 1.91 ± 0.80°, respectively. The two EWPA algorithms performed best in patients with moderate facial asymmetry, and in patients with severe facial asymmetry, the angle error was below 2°, which was a significant improvement over the PA algorithm.

CONCLUSIONS

The clinical application of the EWPA algorithm based on 3D facial morphological analysis for constructing a 3D facial MSP for patients with mandibular deviated facial asymmetry deformity showed a significant improvement over the conventional PA algorithm and achieved the effect of a dental clinical expert-level diagnostic strategy.

Establishment of the mid-sagittal reference plane for three-dimensional assessment of facial asymmetry: a systematic review : Establishment of the mid-sagittal reference plane: a systematic review

OBJECTIVE

To systematically review the literature for mid-sagittal plane establishment approaches to identify the most effective method for constructing the mid-sagittal plane for the evaluation of facial asymmetry.

MATERIALS AND METHODS

Six electronic databases (PubMed, Medline (via Ovid), EMBASE (via Ovid), Cochrane Library, Web of Science, and Scopus) and grey literature were searched for the studies that computed the mid-sagittal reference plane three-dimensionally, using a combination of MeSH terms and keywords. The methodological quality and the level of evidence for the included studies were analyzed using QUADAS-2 and GRADE, respectively.

RESULTS

The preliminary search yielded 6746 records, of which 42 articles that met the predefined inclusion criteria were included in the final analysis. All the included articles reported the construction of the mid-sagittal reference plane (MSP) using varied methods. The risk of bias and concerns regarding the applicability of the included studies were judged to be 'low'. The level of evidence was determined to be 'low' for the effectiveness of the technique and 'moderate' for the ease of clinical applicability.

CONCLUSION

Despite methodological heterogeneity, this review substantiates the comparable efficacy of cephalometric and morphometric MSP construction methods. A fully automated morphometric MSP holds promise as a viable option for routine clinical use. Nevertheless, future prospective studies with an emphasis on the impact, accuracy, and clinical applicability of MSP construction techniques in cases of facial asymmetry are required.

CLINICAL RELEVANCE

The present review will assist clinicians in selecting the most suitable method for MSP construction, leading to improved treatment planning and ultimately more favorable treatment outcomes.

The accuracy and reliability of different midsagittal planes in the symmetry assessment using cone-beam computed tomography

Symmetry is an essential component of esthetic assessment. Accurate assessment of facial symmetry is critical to the treatment plan of orthognathic surgery and orthodontic treatment. However, there is no internationally accepted midsagittal plane (MSP) for orthodontists and orthognathic surgeons. The purpose of this study was to explore a clinically friendly MSP, which is more accurate and reliable than what is commonly used in symmetry assessment. Forty patients with symmetric craniofacial structures were analyzed on cone-beam computed tomography (CBCT) scans. The CBCT data were exported to the Simplant Pro software to build four reference planes that were constructed by nasion (N), basion (Ba), sella (S), odontoid (Dent), or incisive foramen (IF). A total of 31 landmarks were located to determine which reference plane is the most optimal MSP by comparing the asymmetry index (AI). The mean value of AI showed a significant difference (p < 0.05) among four reference planes. Also, the mean value of AI for all landmarks showed that Plane 2 (consisting of N, Ba, and IF) and Plane 4 (consisting of N, IF, and Dent) were more accurate and stable. In conclusion, the MSP consisting of N, Dent, and IF shows more accuracy and reliability than the other planes. Further, it is more clinically friendly because of its significant advantage in landmarking.

Skeletal facial asymmetry: reliability of manual and artificial intelligence-driven analysis

OBJECTIVES

To compare artificial intelligence (AI)-driven web-based platform and manual measurements for analysing facial asymmetry in craniofacial CT examinations.

METHODS

The study included 95 craniofacial CT scans from patients aged 18-30 years. The degree of asymmetry was measured based on AI platform-predefined anatomical landmarks: sella (S), condylion (Co), anterior nasal spine (ANS), and menton (Me). The concordance between the results of automatic asymmetry reports and manual linear 3D measurements was calculated. The asymmetry rate (AR) indicator was determined for both automatic and manual measurements, and the concordance between them was calculated. The repeatability of manual measurements in 20 randomly selected subjects was assessed. The concordance of measurements of quantitative variables was assessed with interclass correlation coefficient (ICC) according to the Shrout and Fleiss classification.

RESULTS

Erroneous AI tracings were found in 16.8% of cases, reducing the analysed cases to 79. The agreement between automatic and manual asymmetry measurements was very low (ICC < 0.3). A lack of agreement between AI and manual AR analysis (ICC type 3 = 0) was found. The repeatability of manual measurements and AR calculations showed excellent correlation (ICC type 2 > 0.947).

CONCLUSIONS

The results indicate that the rate of tracing errors and lack of agreement with manual AR analysis make it impossible to use the tested AI platform to assess the degree of facial asymmetry.

A mathematical algorithm of the facial symmetry plane: Application to mandibular deformity 3D facial data

The three-dimensional (3D) symmetry reference plane (SRP) is the premise and basis of 3D facial symmetry analysis. Currently, most methods for extracting the SRP are based on anatomical landmarks measured manually using a digital 3D facial model. However, as different clinicians have varying definitions of landmarks, establishing common methods suitable for different types of facial asymmetry remains challenging. The present study aimed to investigate and evaluate a novel mathematical algorithm based on power function weighted Procrustes analysis (PWPA) to determine 3D facial SRPs for patients with mandibular deviation. From 30 patients with mandibular deviation, 3D facial SRPs were determined using both our PWPA algorithms (two functions) and the traditional PA algorithm (experimental groups). A reference plane, defined by experts, was considered the 'truth plane'. The 'position error' index of mirrored landmarks was created to quantitatively evaluate the difference among the PWPA SRPs and the truth plane, including overall differences and regional differences of the face (upper, middle and lower). The 'angle error' values between the SRPs and the truth plane in the experimental groups were also evaluated in this study. Statistics and measurement analyses were used to comprehensively evaluate the clinical suitability of the PWPA algorithms to construct the SRP. The average angle error values between the PWPA SRPs of the two functions and the truth plane were 1.21 ± 0.65° and 1.18 ± 0.62°, which were smaller than those between the PA SRP and the truth plane. The position error values of mirrored landmarks constructed using the PWPA algorithms for the whole face and for each facial partition were lower than those constructed using the PA algorithm. In conclusion, for patients with mandibular deviation, this novel mathematical algorithm provided a more suitable SRP for their 3D facial model, which achieved a result approaching the true effect of experts.

[A method for constructing three-dimensional face symmetry reference plane based on weighted shape analysis algorithm]

OBJECTIVE

To establish a novel method based on three-dimensional (3D) shape analysis and weighted Procrustes analysis (WPA) algorithm to construct a 3D facial symmetry reference plane (SRP), automatically assigning weight to facial anatomical landmarks. The WPA algorithm suitability for commonly observed clinical cases of mandibular deviation were analysed and evaluated.

METHODS

Thirty patients with mandibular deviation were recruited for this study. The 3D facial SRPs were extracted independently based on original-mirror alignment method. Thirty-two anatomical landmarks were selected from the overall region by three times to obtain the mean coordinate. The SRP of experimental groups 1 and 2 were using the standard Procrustes analysis (PA) algorithm and WPA algorithm, respectively. A reference plane defined by experts based on regional iterative closest point (ICP) algorithm, served as the ground truth. Three experts manually selecting facial regions with good symmetry for original model, and common region was included in the study. The angle error values between the SRP of WPA algorithm in the experimental group 1 and the truth plane were evaluated in this study, and the SRP of PA algorithm of experimental group 2 was calculated in the same way. Statistics and measurement analysis were used to comprehensively evaluate the clinical suitability of the WPA algorithm to calculate the SRP. A paired t-test analysis (two-tailed) was conducted to compare the angles.

RESULTS

The average angle error between the SRP of WPA algorithm and the ground truth was 1.53°±0.84°, which was smaller than that between the SRP of PA and the ground truth (2.06°±0.86°). There were significant differences in the angle errors among the groups (P < 0.05). For the patients with severe mandibular deviation that the distance between pogonion and facial midline greater than 12 mm, the average angle error of the WPA algorithm was 0.86° smaller than that of the PA algorithm.

CONCLUSION

The WPA algorithm, based on weighted shape analysis, can provide a more adaptable SRP than the standard PA algorithm when applied to mandibular deviation patients and preliminarily simulate the diagnosis strategies of clinical experts.

Quantification of three-dimensional facial asymmetry for diagnosis and postoperative evaluation of orthognathic surgery

Background

To evaluate the facial asymmetry, three-dimensional computed tomography (3D-CT) has been used widely. This study proposed a method to quantify facial asymmetry based on 3D-CT.

Methods

The normal standard group consisted of twenty-five male subjects who had a balanced face and normal occlusion. Five anatomical landmarks were selected as reference points and ten anatomical landmarks were selected as measurement points to evaluate facial asymmetry. The formula of facial asymmetry index was designed by using the distances between the landmarks. The index value on a specific landmark indicated zero when the landmarks were located on the three-dimensional symmetric position. As the asymmetry of landmarks increased, the value of facial asymmetry index increased. For ten anatomical landmarks, the mean value of facial asymmetry index on each landmark was obtained in the normal standard group. Facial asymmetry index was applied to the patients who had undergone orthognathic surgery. Preoperative facial asymmetry and postoperative improvement were evaluated.

Results

The reference facial asymmetry index on each landmark in the normal standard group was from 1.77 to 3.38. A polygonal chart was drawn to visualize the degree of asymmetry. In three patients who had undergone orthognathic surgery, it was checked that the method of facial asymmetry index showed the preoperative facial asymmetry and the postoperative improvement well.

Conclusions

The current new facial asymmetry index could efficiently quantify the degree of facial asymmetry from 3D-CT. This method could be used as an evaluation standard for facial asymmetry analysis.

[Visual sensitivity threshold of lateral view of nasolabial Angle changes in edentulous jaw patients]

OBJECTIVE

To study the visual sensitivity threshold of physician's naked eye to the difference of nasolabial angle in edentulous jaw patients, and to provide a reference value for the study of aesthetic evaluation of soft tissue profile for the difference of nasolabial angle that can be recognized by human eyes.

METHODS

Three-dimensional facial images of three edentulous patients with different diagnostic dentures introoral were obtained. Lateral screenshots of each patient's three-dimensional facial image with the same scale were obtained by using reverse engineering software (Geomagic studio 2014).The screenshot of the patient's three-dimensional facial image with suitable lip support (The suitable lip support was confirmed by both patients and prosthodontists who had clinical experience for more than 20 years) was taken as the reference picture, and the remaining pictures were grouped with it respectively. All the pictures were observed in random order by the subjects. Fifteen dentists were asked to judge the difference of nasolabial angle between the two pictures of each group on the computer screen. The difference of nasolabial angle between the two pictures in each group was measured and calculated. The ROC curve was drawn, and the best cut-off value was calculated as the visual sensitivity threshold.

RESULTS

The data of the 15 subjects were used to draw ROC curves separately. The maximum and minimum best cut-off values were 5.55 degrees and 3.12 degrees respectively. The ROC curve of the whole 15 subjects was drawn after data aggregation, and the best cut-off value was 5.36 degrees (AUC=0.84>0.5, P=0.000<0.05). When the difference of nasolabial angle was above 5.36 degrees, the subjects could recognize it effectively.

CONCLUSION

There is a visual limit in the observation of the nasolabial angle with the naked eye. In this study, a visual sensitivity threshold of 5.36 degrees for the difference of the nasolabial angle was obtained. The difference of nasolabial angle below this value can be regarded as no clinical significance. This result provides a reference value for human eyes to recognize the difference of nasolabial angle in soft tissue profile aesthetic evaluation. It can be applied to the aesthetic evaluation of soft tissue profile and can be used as the error level of related research with nasolabial angle as an index for accuracy evaluation.

[Using three-dimensional craniofacial images to construct horizontal reference plane]

OBJECTIVE

To compare four different three-dimensional horizontal planes and detect anatomical landmarks so as to provide theoretical reference for horizontal reference plane constructed by three-dimensional cephalometry.

METHODS

The subjects of this study were 32 facial symmetry patients (menton from midsagittal plane ≤2 mm). Cone-beam computed tomography (CBCT) was obtained before orthodontic treatment, and the data were imported into Dolphin imaging soft in DICOM format. The sagittal plane was passing through the Nasion, Sella and Dent. Four horizontal reference planes were constructed by three points of bilateral porion and bilateral orbitale. Plane 1: horizontal reference plane constructed by right porion and bilateral orbitale. Plane 2: horizontal reference plane constructed by left porion and bilateral orbitale. Plane 3: horizontal reference plane constructed by bilateral porion and right orbitale. Plane 4: horizontal reference plane constructed by bilateral porion and left orbitale. Pitch, yaw, roll for four planes were measured three dimensionally. All the samples were measured two times by one judge at an interval of two weeks. The two times measuring results were evaluated with Intraclass correlation coefficient (ICC) for verifying reliability. The multiple sets of repeated measurement analysis were used to compare the four different planes. Based on ages, the samples were divided into two groups (group 1: ages 13 to 17, group 2: over 18 years), the mean and standard deviation of landmark coordinates measured with Dent as the origin point, the circumference formula was applied to calculate the change of landmark position generated by head rotation.

RESULTS

No significant differences of pitch, yaw and roll among the four planes (P=0.196, 0.314, and 0.341). One degree of pitch rotation made changes of porion and orbitale approximate 0.5 mm, and 1.6 mm, respectively. One degree of yaw rotation made changes of porion and orbitale approximate 1.1 mm, and 1.5 mm, respectively. One degree of roll rotation made changes of porion and orbitale approximate 1.2 mm, and 0.7 mm, respectively.

CONCLUSION

There was no significant difference among the four horizontal planes constructed by any three points of bilateral orbitales and bilateral porions. It has the highest concordance using bilateral orbitales and one porion to construct horizontal plane in this study, probably the best option in clinical practice. Different head rotation generated different distance changes of anatomical landmarks.

Theoretical Basis for Virtual Skull Orientation According to Three-Dimensional Frankfort Horizontal Plane for Computer-Aided Surgical Simulation

PURPOSE

Computer-aided surgical simulation (CASS) is an evolving technology which has significantly affected surgical correction of dentofacial deformities, a key step of which is orientation of the virtual skull model to allow for analysis and treatment planning. Explored in this study is the coplanarity of a 3-dimensional Frankfort horizontal plane (3D FHP).

MATERIALS AND METHODS

The 122 17.0 cm field-of-view cone-beam computed-tomogram (CBCT) scans were oriented to a 3D FHP using right porion, right orbitale, and left orbitale. The distance between the 3D FHP and left porion was then measured. The 18 CBCT scans were found to have external fiducial markers which were used for orientation into natural head position (NHP). The distance between left porion and a true horizontal plan coincidental with the right porion was measured. Concordance reliability measures were calculated to compare NHP to 3D FHP.

RESULTS

The average distance of left porion to 3D FHP was found to be -0.107 mm (SD = 1.148), and the average distance from the coincidental left porion in NHP was found to be 0.846 mm (SD = 2.611). Concordance reliability calculations shows little consistency between the 2 methods of orientation (P = 0.838).

CONCLUSIONS

The data shows coincidence between left porion and 3D FHP. Orientation of the virtual skull model according to 3D FHP offers a quick and easy method for this important step in CASS. Further study is needed for evaluation of this method in vivo.

Association between palatally displaced maxillary central incisors and lateral incisors: A retrospective cone-beam computed tomographic study

INTRODUCTION

The objective of this study was to investigate the location, orientation and root development of maxillary lateral incisors in patients with palatally impacted central incisors. Comparison was made between the lateral incisor on the affected side and that on the normally erupted side.

METHODS

Cone-beam computed tomographic images from 20 patients (10 boys, 10 girls, mean age (9.01 ± 1.52 years old) with unilateral palatally impacted maxillary central incisors were imported into Dolphin imaging software 11.8 for 3-dimensional reconstruction and reorientation. Software measurement tools were used to measure the root length, crown distance, angle to palatal plane, distance to midline, and angle to midsagittal plane of the maxillary lateral incisors on both the impacted and unaffected sides.

RESULTS

The Wilcoxon signed rank test indicated that lateral incisors on the impacted side were more proclined, at a mean angle difference of 29.47° in the sagittal plane (P < 0.001). The mean length of the roots of the lateral incisors was 1.21 mm shorter (P < 0.05) on the affected side compared with the normal side, and the lateral incisor crowns on the impacted side were located at an average of 4.57 mm closer to the palatal plane than on the normally erupted side (P < 0.001). The angle of long axis of the lateral incisors on the affected side had a greater angulation to the midsagittal plane compared with the unaffected side, with a mean difference of 30.27° (P < 0.001).

CONCLUSIONS

Maxillary lateral incisors adjacent to palatally impacted maxillary central incisors side had abnormal root development and demonstrated angulation and position change compared with those adjacent to normally erupted central incisors.

Comparison of Lip Line Cant Change After 1-Jaw and 2-Jaw Surgery

OBJECTIVES

The purpose of this study was to compare the lip line cant (LLC) changes after 1 and 2-jaw surgery, and to evaluate the correlations of the craniofacial factors affecting LLC.

METHODS

The study subjects were selected (LLC amount within 1.5-6.0°) from among the patients diagnosed with Class III malocclusion who underwent one (n = 20) or 2-jaw surgery (n = 20). Cone beam computed tomography images were obtained immediately before the operation (T1) and 6 months after the operation (T2). Preoperative and postoperative craniofacial measurements were obtained.

RESULTS

The study subjects showed 3.12° LLC on average before undergoing 1-jaw surgery, and their LLC changed to 1.27° after the surgery. As for 2-jaw surgery, the subjects showed 3.38° LLC on average before the surgery and 0.98° after the surgery. LLC at pre-treatment may be more affected by a cant of the occlusal plane in the mandible than maxilla. In the comparison of the value of changes of LLC, the value of 2-jaw surgery was bigger than the value of 1-jaw surgery but the difference was statistically insignificant.

LIMITATIONS

This study had a limitation in that the muscles were not considered. And the metal bracket or metal crown and bridge, however, can cause noise and blurring artifacts in CT, which can lead to a low resolution. And the limited number of the patients should be considered.

CONCLUSIONS

In correlation analysis, both pre-surgery LLC and change of LLC have correlation with almost all the craniofacial measurement. Lip-line cant of patients with facial asymmetry has higher correlation with mandibular cant than with other cants. To improve the LLC, a surgical plan should be established to minimize the mandibular cant using the computer simulation as well as the maxillary cant.

Control of anterior segment using an antero-posterior lingual sliding retraction system: a preliminary cone-beam CT study

BACKGROUND

This study was performed to evaluate the treatment effects of the antero-posterior lingual retractor (APLR), focusing on the 3-dimensional (3D) tooth movement of the maxillary anterior teeth and their alveolar bone levels.

METHODS

En masse retraction was performed using either the C-lingual retractor (CLR, C-group, n = 9) or the antero-posterior lingual retractor (APLR, AP-group, n = 8). We evaluated 3D movement of the maxillary anterior teeth and alveolar bone levels, root length of the central incisors, long axes of the maxillary canines, and occlusal plane changes from CBCT images.

RESULTS

After retraction, the central incisors were more significantly intruded and their root apex was more retracted in the AP-group. The long axis of the canine was well maintained in the AP-group. There were no differences in the steepness of occlusal plane and the incidence of alveolar bone loss or of root resorption during en masse retraction with the two retractors.

CONCLUSIONS

The clockwise bowing effect of the anterior segment was less with the APLR, which prevented unwanted canine movement.

Facial asymmetry: a current review

The term "asymmetry" is used to make reference to dissimilarity between homologous elements, altering the balance between structures. Facial asymmetry is common in the overall population and is often presented subclinically. Nevertheless, on occasion, significant facial asymmetry results not only in functional, but also esthetic issues. Under these conditions, its etiology should be carefully investigated in order to achieve an adequate treatment plan. Facial asymmetry assessment comprises patient's first interview, extra- as well as intraoral clinical examination, and supplementary imaging examination. Subsequent asymmetry treatment depends on patient's age, the etiology of the condition and on the degree of disharmony, and might include from asymmetrical orthodontic mechanics to orthognathic surgery. Thus, the present study aims at addressing important aspects to be considered by the orthodontist reaching an accurate diagnosis and treatment plan of facial asymmetry, in addition to reporting treatment of some patients carriers of such challenging disharmony.

Facial asymmetry revisited: Part I- diagnosis and treatment planning

Facial asymmetry is an individualized characteristic and is commonly observed sub clinically in overall population. However, clinically significant facial asymmetry with associated morphologic, esthetic and stomatognathic problems warrant investigation of the underlying etiology and comprehensive clinical examination in conjunction with imaging studies for diagnosis, localization of asymmetry and treatment planning. The principal aim of this article is to present an invaluable insight into etiopathogenesis, myriad classifications and various systematic diagnostic approaches indispensable for formulation of treatment plan and appropriate management of facial asymmetry.

Three-Dimensional Anthropometric Database of Attractive Caucasian Women: Standards and Comparisons

The aim of this paper is to develop a database to determine a new biomorphometric standard of attractiveness. Sampling was carried out using noninvasive three-dimensional relief methods to measure the soft tissues of the face. These anthropometric measurements were analyzed to verify the existence of any canons with respect to shape, size, and measurement proportions which proved to be significant with regard to the aesthetics of the face. Finally, the anthropometric parameters obtained were compared with findings described in the international literature.

The study sample was made up competitors in the Miss Italy 2010 and 2009 beauty contest. The three-dimensional (3D) scanning of soft tissue surfaces allowed 3D digital models of the faces and the spatial 3D coordinates of 25 anthropometric landmarks to be obtained and used to calculate linear and angular measurements. A paired Student t test for the analysis of the means allowed 3 key questions in the study of biomorphometric parameters of the face to be addressed through comparison with the data available in the literature.

The question of statistical evidence for the samples analyzed being members of the populations samples reported in literature was also addressed.

The critical analysis of the data helped to identify the anthropometric measurements of the upper, middle, and lower thirds of the face, variations in which have a major influence on the attractiveness of the face. These changes involve facial width, height, and depth. Changes in measurements of length, angles, and proportions found in the sample considered were also analyzed.

Lip line changes in Class III facial asymmetry patients after orthodontic camouflage treatment, one-jaw surgery, and two-jaw surgery: A preliminary study

OBJECTIVE

To evaluate the effects of orthodontic camouflage treatment (OCT), one-jaw surgery, and two-jaw surgery on the correction of lip line cant (LLC) and to examine factors affecting the correction of LLC in Class III craniofacial asymmetry patients.

MATERIALS AND METHODS

A sample of 30 Class III craniofacial asymmetry patients was divided into OCT (n = 10), one-jaw surgery (n = 10), and two-jaw surgery (n = 10) groups such that the pretreatment LLC was similar in each group. Pretreatment and posttreatment cone-beam computed tomography scans were used to measure dental and skeletal parameters and LLC. Pretreatment and posttreatment measurements were compared within groups and between groups. Pearson's correlation tests and multiple regression analyses were performed to investigate factors affecting the amount and rate of LLC correction.

RESULTS

The average LLC correction was 1.00° in the one-jaw surgery group, and in the two-jaw surgery group, it was 1.71°. In the OCT group it was -0.04°, which differed statistically significantly from the LLC correction in the other two groups. The amount and rate of LLC correction could be explained by settling of skeletal discrepancies or LLC at pretreatment with goodness of fit percentages of approximately 82% and 41%, respectively.

CONCLUSIONS

Orthognathic surgery resulted in significant correction of LLC in Class III craniofacial asymmetry patients, while OCT did not.

Comparison of cone-beam computed tomography cephalometric measurements using a midsagittal projection and conventional two-dimensional cephalometric measurements

Objective

This study investigated whether it is possible to use a two-dimensional (2D) standard in three-dimensional (3D) analysis, by comparing the angles and lengths measured from a midsagittal projection in 3D cone-beam computed tomography (CBCT) with those measured by 2D lateral cephalometric radiography (LCR).

Methods

Fifty patients who underwent both LCR and CBCT were selected as subjects. CBCT was reoriented in 3 different methods and the measuring-points were projected onto the midsagittal plane. Twelve angle values and 8 length values were measured on both LCR and CBCT and compared.

Results

Repeated measures analysis of the variance revealed statistically significant differences in 7 angular and 5 linear measurements among LCR and 3 types of CBCT (p < 0.05). Of these 12 measurements, multiple comparisons showed that 6 measurements (ANB, AB to FH, IMPA, FMA, Co-Gn, Go-Me) were not significantly different in pairwise comparisons. LCR was significantly different from 3 types of CBCT in 3 angular (SN to FH, interincisal angle, FMIA) and 2 linear (S-Go, Co-ANS) measurements. The CBCT method was similar for all measurements, except for 1 linear measurement, i.e., S-N. However, the disparity between the mean values for all parameters was within the range of clinical measurement error.

Conclusions

3D-CBCT analysis, using midsagittal projection, is a useful method in which the 2D-LCR normative values can be used. Although the measurements changed with reorientation, these changes were not clinically significant.

Three-dimensional assessment of facial asymmetry: A systematic review

For patients with facial asymmetry, complete and precise diagnosis, and surgical treatments to correct the underlying cause of the asymmetry are significant. Conventional diagnostic radiographs (submento-vertex projections, posteroanterior radiography) have limitations in asymmetry diagnosis due to two-dimensional assessments of three-dimensional (3D) images. The advent of 3D images has greatly reduced the magnification and projection errors that are common in conventional radiographs making it as a precise diagnostic aid for assessment of facial asymmetry. Thus, this article attempts to review the newly introduced 3D tools in the diagnosis of more complex facial asymmetries.

KPG index versus OPG measurements: a comparison between 3D and 2D methods in predicting treatment duration and difficulty level for patients with impacted maxillary canines

Aim. The aim of this study was to test the agreement between orthopantomography (OPG) based 2D measurements and the KPG index, a new index based on 3D Cone Beam Computed Tomography (CBCT) images, in predicting orthodontic treatment duration and difficulty level of impacted maxillary canines. Materials and Methods. OPG and CBCT images of 105 impacted canines were independently scored by three orthodontists at t₀ and after 1 month (t₁), using the KPG index and the following 2D methods: distance from cusp tip and occlusal plane, cusp tip position in relation to the lateral incisor, and canine inclination. Pearson's coefficients were used to evaluate the degree of agreement and the χ² with Yates correction test was used to assess the independence between them. Results. Inter- and intrarater reliability were higher with KPG compared to 2D methods. Pearson's coefficients showed a statistically significant association between all the indexes, while the χ² with Yates correction test resulted in a statistically significant rejection of independency only for one 2D index. Conclusions. 2D indexes for predicting impacted maxillary canines treatment duration and difficulty sometimes are discordant; a 3D index like the KPG index could be useful in solving these conflicts.