Morphologic relationship between the cranial base and the mandible in patients with facial asymmetry and mandibular prognathism

Discrepancies Between Objective and Subjective Outcomes of and Quality of Life During Molding Helmet Therapy for Cranial Deformities

Positional skull deformities have been on the rise for decades and can be treated with molding helmets in early childhood. Parents often fear later cosmetic stigmatization, but also a reduced quality of life (QoL) during treatment. The aim of this study was to examine therapy results in our patient collection from a new perspective. Cranial vault asymmetry (CVA), cranial vault asymmetry index (CVAI), and cranial index (CI) were compared before and after molding helmet therapy. Correction was defined by a decrease in CVA <3.5 mm and CI <90%. Subjective therapy outcome, side effects and QoL from the parents' perspective were determined using a questionnaire. There were 25 patients included. Differences between pretherapeutic and posttherapeutic CVA, CVAI, and CI were significant (P<0.01). An objective correction according to the defined values was observed in only 12% of cases. However, 76% of parents stated that their child's skull shape was normal after therapy. There were 60 side effects reported in 23 cases. The QoL of 21 children was assessed as unimpaired during helmet therapy. Even though complete normalization was rarely observed, the parameters were significantly different after therapy, and subjective reduction in skull deformity was common.

Automated localization of mandibular landmarks in the construction of mandibular median sagittal plane

OBJECTIVE

To use deep learning to segment the mandible and identify three-dimensional (3D) anatomical landmarks from cone-beam computed tomography (CBCT) images, the planes constructed from the mandibular midline landmarks were compared and analyzed to find the best mandibular midsagittal plane (MMSP).

METHODS

A total of 400 participants were randomly divided into a training group (n = 360) and a validation group (n = 40). Normal individuals were used as the test group (n = 50). The PointRend deep learning mechanism segmented the mandible from CBCT images and accurately identified 27 anatomic landmarks via PoseNet. 3D coordinates of 5 central landmarks and 2 pairs of side landmarks were obtained for the test group. Every 35 combinations of 3 midline landmarks were screened using the template mapping technique. The asymmetry index (AI) was calculated for each of the 35 mirror planes. The template mapping technique plane was used as the reference plane; the top four planes with the smallest AIs were compared through distance, volume difference, and similarity index to find the plane with the fewest errors.

RESULTS

The mandible was segmented automatically in 10 ± 1.5 s with a 0.98 Dice similarity coefficient. The mean landmark localization error for the 27 landmarks was 1.04 ± 0.28 mm. MMSP should use the plane made by B (supramentale), Gn (gnathion), and F (mandibular foramen). The average AI grade was 1.6 (min-max: 0.59-3.61). There was no significant difference in distance or volume (P > 0.05); however, the similarity index was significantly different (P < 0.01).

CONCLUSION

Deep learning can automatically segment the mandible, identify anatomic landmarks, and address medicinal demands in people without mandibular deformities. The most accurate MMSP was the B-Gn-F plane.

Three-Dimensional Analysis of the Cranial Base Structure in Patients with Facial Asymmetry

Facial asymmetry is often seen in patients with skeletal mandibular prognathism and is associated with deformities in the maxillofacial and head regions. The maxillofacial deviation is three-dimensional and affects not only the lateral deviation of the mandible and midface, but also the cranium. This study conducted a three-dimensional morphological evaluation of the cranial base morphology of patients with skeletal mandibular prognathism (ANB < 0°, Wits < 0 mm) with the aim of examining the relationship between deformities of the head region and facial asymmetry. Data obtained from computed tomography conducted during the initial examination of patients with and without skeletal mandibular prognathism with facial asymmetry were used. Differences in the position of structures present in the cranial base were measured, and the association between cranial deformities and mandibular deviation was assessed. The middle cranial base area and the lateral deviation of the mandibular fossa were significantly larger in patients with facial asymmetry compared to those without facial asymmetry. In addition, a correlation between the amount of mandibular deviation and the area of the anterior cranial base was identified in patients with significant cranial deformity (p = 0.012). Given the identified association between the structure of the head region and facial asymmetry, further studies are needed to determine the factors implicated in the growth process.

'Study of the maxillary yaw on cone beam computed tomography: A preliminary report and comparison between two different dento-skeletal malocclusions'

OBJECTIVES

To assess the skeletal and dental maxillary transverse compensation (yaw) on the cone beam computed tomography (CBCT) three-dimensional reconstructed image of the skull in two groups of patients, both clinically affected by a class III malocclusion with deviation of the lower midline.

MATERIALS AND METHODS

An observational retrospective study was designed to analyse differences in two groups of patients, the first one was composed by patients affected by horizontal condylar hyperplasia, the second one by patients affected by dento-skeletal asymmetric class III malocclusion. Each group was composed by 15 patients. Transverse analysis was performed by measuring five landmarks (three bilateral and two uneven) with respect to a mid-sagittal plane; sagittal analysis was performed by measuring the sagittal distance on the mid-sagittal plane between bilateral points. Means were compared through inferential analysis.

RESULTS

In the condylar hyperplasia group, all differences between the two sides were not statistically significant, nor for canines' difference (P = .0817), for molars (P = .1105) or for jugular points (.05871). In the class III group, the differences between the two sides were statistically significant for molars (P = .0019) and jugular points (P = .0031) but not for canines (P = .1158). Comparing the two groups, significant differences were found only for incisors' midline deviation (P = .0343) and canine (P = .0177).

CONCLUSION

The study of the yaw on CBCT should be integrated into three-dimensional cephalometry and could help in differentiating the various malocclusion patterns.

Hard and Soft Tissue Asymmetry in Patients with Skeletal Class III Malocclusion: A Cone-Beam Computed Tomography Study

This study aims to investigate hard and soft tissue asymmetry in skeletal Class III patients to elucidate how soft tissue thickness alters overall asymmetry and whether menton deviation is correlated with bilateral differences in hard and soft tissue prominence and soft tissue thickness. The cone-beam computed tomography data of 50 skeletal Class III adults were divided based on menton deviation into symmetric (n = 25; deviation ≤ 2.0 mm) and asymmetric (n = 25; deviation > 2.0 mm) groups. Forty-four corresponding hard and soft tissue points were identified. Bilateral hard and soft tissue prominence and soft tissue thickness were compared using paired t-tests. The correlations between bilateral differences in these variables and menton deviation were examined using Pearson's correlation analysis. In the symmetric group, no significant bilateral differences in soft and hard tissue prominence and soft tissue thickness were observed. In the asymmetric group, both hard and soft tissue prominence were significantly greater on the deviated side than the non-deviated side at most of the points; however, no significant differences in soft tissue thickness were detected except at point 9 (ST9/ST'9, p = 0.011). The difference of hard and soft tissue prominence at point 8 (H8/H'8 and S8/S'8) was positively correlated with menton deviation, whereas the soft tissue thickness at point 5 (ST5/ST'5) and point 9 (ST9/ST'9) was negatively correlated with menton deviation (p = 0.05). Soft tissue thickness does not affect overall asymmetry in the presence of underlying hard tissue asymmetry. Soft tissue thickness at the centre of the ramus may be correlated with the degree of menton deviation in patients with asymmetry; however, this correlation needs to be confirmed by further studies.

Using the anterior cranial base to provide a reliable reference plane for patients with or without facial asymmetry

INTRODUCTION

This study aimed to investigate the midsagittal reference plane (MSP) reliability derived from the 3-dimensional characteristics of patients with or without facial asymmetry in the anterior cranial base (ACB).

METHODS

We divided the cone-beam computed tomography (CBCT) images of 60 adult patients into maxillofacial symmetry and asymmetry groups. The ACB models were 3-dimensionally constructed, and then symmetrical characteristics were evaluated with surface asymmetry for each group. The reliability of the MSP derived from the symmetry of the anterior cranial base (MSPACB) was assessed in comparison with the true craniofacial symmetry plane determined using the morphometric method.

RESULTS

The ACB was symmetrical, as demonstrated by slight surface asymmetry. The MSPACB was reliable for maxillofacial asymmetrical analysis as the intraobserver and interobserver measurements using the MSPACB were of excellent agreement, and there was no significant difference between MSPACB and morphometric method in asymmetrical measurements in both groups. The MSPACB remained stable (maximum deviation <0.32 mm) when cranial landmark identification errors (1 mm and 4 mm) were simulated.

CONCLUSIONS

MSPACB is reliable for patients with or without facial asymmetry in maxillofacial asymmetry analysis, which is beneficial to patients with severe midfacial asymmetry or trauma when conventional landmarks are displaced or disappear. When using MSPACB for patients with cranial malformations or those whose ACBs differ from normal dimensions, caution should be taken.

Three-dimensional evaluation using CBCT of the mandibular asymmetry and the compensation mechanism in a growing patient: A case report

Background

This case report aims to evaluate the development and the compensation mechanisms of the mandibular asymmetry in a growing male patient using cone beam computed tomography (CBCT). In this case, the menton deviated on the right, a sporadic condition, which may be the consequence of a disorder in the mandibular growth.

Case presentation

The young male patient was treated with rapid palatal expander (RPE) and Fränkel functional regulator III (FR-3). The initial CBCT was acquired at the beginning of therapy when the patient was 8 years old, and the final CBCT was developed at the end of the treatment when the patient was 12 years old. The patient's CBCT was performed with the head oriented according to the Natural Head Position (NHP); the NHP is a physiological and reproducible posture defined for morphological analysis. The 3D image of the cranium was oriented in the Dolphin software according to NHP posture, and cephalometric measurements were taken in the software's frontal, laterolateral right and left, posteroanterior, and submentovertex views. The therapy lasted 3.8 years and ended with significant regression of the mandibular asymmetry from moderate grade (4.2 mm) to slight grade (1.3 mm).

Conclusion

The literature shows that the left hemi-mandible has grown more than the right side, which affirms that in case of deviation of the menton >4 mm, the bone volume increases on the non-deviated side.

Correlation between the position of the glenoid fossa and condylar translational movement in skeletal Class III mandibular asymmetry patients

OBJECTIVES

Understanding the mechanism of mandibular asymmetry (MA) is important to provide suggestions for occlusal treatment and to know the developmental process of masticatory dysfunction. To investigate the morphological and functional effects on MA, we evaluated the three-dimensional position of the glenoid fossa and its relationship to asymmetrical condylar translational movement.

METHODS

In this retrospective study, 50 subjects who previously underwent computed tomography for surgical purposes were divided into MA and control groups according to a menton deviation of at least 4 mm from the mid-sagittal plane. The glenoid fossae positions were evaluated using a three-dimensional analysis program. Condylar translational movements were recorded and measured by computerized axiography on protrusion. Side-to-side asymmetry was measured for each parameter. Asymmetry index value was calculated to assess the correlation between glenoid fossa position and condylar movement. Wilcoxon's signed-ranked test, Mann-Whitney U-test, and Spearman's rank correlation were used for the statistical analysis.

RESULTS

In the MA group, glenoid fossa position on the shifted side was significantly inferior and posterior as compared to that on the non-shifted side and of the control group. Condylar path length and sagittal condylar inclination were significantly greater on the shifted side versus non-shifted side, while no significant difference was found in transverse condylar inclination. The asymmetry index of the anterior-posterior glenoid fossa position was significantly correlated with that of condylar path length and bilateral transverse condylar inclination. In the control group, there were no significant correlations among the morphological and functional parameters.

LIMITATIONS

This study did not consider muscle activity and disc position, which may affect condylar movement.

CONCLUSIONS

Functional asymmetry of condylar translational movements is closely related to asymmetry of glenoid fossa position in MA patients.

Side Effects of Cranial Remolding Orthoses: A Multi-Site Review

ABSTRACT

Infants with deformational head shapes may be treated with a Cranial Remolding Orthosis (CRO). Risks of CROs include skin irritations and other minor side effects. It is important to examine the incidence of complications with CRO treatment to determine if the potential benefits outweigh the risks.This study retrospectively examined surveys provided by both practitioners and caregivers regarding orthotic treatment side effects and wear time at four clinics in Canada. Statistical analysis including the Chi-square test and Fisher's exact tests were performed to examine how the side effects varied by treatment site and by reported orthotic wear time.In total, 5,025 surveys about the CRO treatment of 453 patients were reviewed. The most common side effects were pressure spots, redness lasting for more than 1 hour, excessive sweat, and foul odor; however, the vast majority reported no significant issues (87.08%). Only 2.81% of surveys reported multiple side effects, which was about three times more like to happen when the CRO was reported to have fit problems. Wear time is correlated with the report of side effects; infants who wore the CRO 18 to 23.5 hours had statistically fewer side effects than those who wore the CRO for less time. The reported incidence of side effects may be artificially inflated because infants experiencing side effects are more likely to have more frequent follow-up.Overall, the side effects of CRO treatment reported in this cohort were relatively rare and minimal, indicating CRO treatment is a safe way to treat deformational head shapes.

The three-dimensional morphology of mandible and glenoid fossa as contributing factors to menton deviation in facial asymmetry-retrospective study

Background

The aim of this study is to evaluate whether the three-dimensional (3D) morphology of the mandibular condyle, glenoid fossa, and mandible correlated with menton deviation in facial asymmetry.

Subjects and methods

Thirty adults (15 males and 15 females; mean age, 23.2 ± 3.8 years) with facial asymmetry were included. Linear, angular, and volumetric measurements of the 3D morphology of the mandibular condyle, glenoid fossa, and mandible were recorded using computed tomography (CT) images. The right/left differences were obtained by subtracting the left value from the right value, and an independent t test was used to compare the differences between the females and males. Multiple regression analysis was performed to identify the correlation between the right/left difference of the 3D morphology and menton deviation.

Results

The results of the comparative analysis did not show any statistical difference between the females and males (P > .05), so the females and males were combined. Multiple regression analysis for the mandibular condyle, glenoid fossa, and mandible showed that neck length, ramus length, and frontal ramal inclination had positive influences on menton deviation, with 76.5% of explanatory power. The neck length and head volume of the mandibular condyle when only the mandibular condyle was considered, and the ramus length and frontal ramal inclination when only the mandible was considered had positive influence on menton deviation with 69.9% and 68.6% explanatory power, respectively. On the other hand, when only considering glenoid fossa, the glenoid fossa had little effect on menton deviation with 15.7% of explanatory power.

Conclusions

In facial asymmetry, the right/left differences in mandibular condyle and mandible have more impact on the menton deviation than the right/left differences in glenoid fossa.

Trial registration

CNUDH, CNUDH-EXP-2017-016. Registered 28 September 2017

Towards an early 3D-diagnosis of craniofacial asymmetry by computing the accurate midplane: A PCA-based method

BACKGROUND AND OBJECTIVE

Craniofacial asymmetry is a common growth disorder often caused by unilateral chewing. Although an early orthodontic treatment would avoid surgical procedures later in life, the uncertainty of defining the accurate sagittal midplane potentially leads to misdiagnosis and therefore inaccurate orthodontic treatment plans. This novel study aims to 3D-diagnose craniofacial complex malformations in children with unilateral crossbite (UXB) considering a midplane which compensates the asymmetric morphology.

METHODS

The sagittal midplane of 20 children, fifteen of whom exhibited UXB, was computed by a PCA-based method which compensates the asymmetry mirroring the 3D models obtained from cone-beam computed tomography data. Once determined, one side of the data was mirrored using the computed midplane to visualize the malformations on the hard and soft tissues by 3D-computing the distances between both halves. Additionally, 31 skull's landmarks were manually placed in each model to study the principal variation modes and the significant differences in the group of subjects with and without UXB through PCA and Mann-Whitney U test analyses respectively.

RESULTS

Morphological 3D-analysis showed pronounced deformities and aesthetic implications for patients with severe asymmetry (jaw deviation > 0.8 mm) in whole craniofacial system, while initial signs of asymmetry were found indistinctly in the mandible or maxilla. We detected significant (p < 0.05) malformations for example in mandibular ramus length (0.0086), maxillary palate width (0.0481) and condylar head width (0.0408). Craniofacial malformations increased the landmarks' variability in the group of patients with UXB over the control group requiring 8 variation modes more to define 99% of the sample' variability.

CONCLUSIONS

Our findings demonstrated the viability of early diagnosis of craniofacial asymmetry through computing the accurate sagittal midplane which compensates the individual's asymmetrical morphology. Furthermore, this study provides important computational insights into the determination of craniofacial deformities which are caused by UXB, following some empirical findings of previous clinical studies. Hence, this computational approach can be useful for the development of new software in craniofacial surgery or for its use in biomedical research and clinical practice.

Mandibular and temporomandibular morphologic characteristics of patients with suspected unilateral condylar hyperplasia: a CT study

INTRODUCTION

Facial asymmetry associated with unilateral condylar hyperplasia (UCH) is a complicated clinical condition.

OBJECTIVE

The objective of this study was to describe morphological characteristics of the mandible and the temporomandibular joint in patients with facial asymmetry, using computed tomography and 3D reconstruction.

METHODS

A retrospective observational study was performed with patients displaying facial asymmetry evaluated by single photon emission computed tomography (SPECT)/CT analysis, for suspected UCH, between 2015 and 2018. The following variables were compared between the affected side (producing the asymmetry) and the contralateral side (side to where the jaw is deflected): condylar length, condylar medial and lateral pole length, mandibular ramus length, intra-articular spaces, articular eminence height and position of the posterior wall of the glenoid fossa.

RESULTS

Forty-three patients (21 women, mean age: 20.7 ± 7.25 years) with facial asymmetry were included, 19 patients presented right side deviation and 24 patients had left side deviation. Condylar length, lateral pole length, the sum of maximum values and articular eminence height were greater in the affected side (p< 0.05). A positive correlation was found between the position of the posterior wall of the glenoid fossa and the articular eminence height in the affected side (r = 0.442).

CONCLUSIONS

In patients with suspected UCH, evaluated through CT, craniofacial measurements showed significantly larger condylar length and the condylar sum of maximum values in the affected side. A positive correlation was found between the increased dimensions of the articular eminence and the more posterior position of the glenoid fossa in the affected side.

Significant Factors in Cranial Remolding Orthotic Treatment of Asymmetrical Brachycephaly

This retrospective chart review focuses on determining the most effective time to begin cranial remolding orthosis (CRO) treatment for infants with asymmetrical brachycephaly. Subjects with asymmetrical brachycephaly started CRO treatment between 3 and 18 months of age. These infants had a cranial vault asymmetry index (CVAI) ≥ 3.5 and a cranial index (CI) ≥ 90. Subjects were excluded if they had any comorbidities affecting growth, dropped out of treatment, were lost to follow-up, or were noncompliant. Factors which were found to statistically influence treatment outcomes were subject initial age, initial CVAI, and initial CI. Overall, younger subjects were more likely to achieve a corrected head shape. The presence of prematurity or torticollis had statistically nonsignificant effects on the success of treatment. Initial CI was found to be a stronger predictor than initial CVAI as to which subjects achieved correction. The less severe the starting CI, the more likely the subject was to achieve full correction. The clinical understanding is that it requires more cranial growth to "round out" a full posterior skull flattening than an asymmetry. Based on the study results, infants with asymmetrical brachycephaly should be treated as early as possible to increase chances of achieving full correction of the deformity.

Skeletal open bite cranial base characteristics in young Latin-American individuals with class I, II and III malocclusions: An observational study

OBJECTIVE

This study aimed to compare cranial base linear and angular measurements between individuals with skeletal open bite and different sagittal skeletal relationships.

MATERIALS AND METHODS

This observational and cross-sectional study included 101 lateral radiographs of young Latin-American individuals with skeletal open bite that met the inclusion criteria and were collected from a private radiological centre. Three groups were formed. Groups 1, 2 and 3 included individuals with skeletal open bite (negative overbite and FMA>30°) and Class I (n=31), II (n=35) and III (n=35) sagittal skeletal relationship, respectively. The anterior and posterior cranial bases (SN and SBa), and cranial base angles (BaSN and ArSN) were measured. Groups were compared with one-way analysis of variance and post-hoc Scheffé tests. The influence of predictor variables on the cranial base were evaluated with linear regressions (α=0.05).

RESULTS

The cranial base angles were significantly smaller (approximately 3° to 5°) in the skeletal open bite Class III group (BaSN=127.97°± 5.86°, ArSN=120.19°±6.12°) when compared with the other groups. BaSN angle, Class I versus Class III (p<0.001) and Class II versus Class III (p<0.001). ArSN angle, Class I versus Class III (p=0.005) and Class II versus Class III (p=0.026). Multiple linear regressions showed that sex had a significant influence on both cranial base dimensions with men showing larger values than women.

CONCLUSIONS

Skeletal open bite Class III individuals show a smaller cranial base angle than Skeletal open bite Class I or II individuals.

Application of the foramina of the trigeminal nerve as landmarks for analysis of craniofacial morphology

Objective

The objective of this study was to develop new parameters based on the foramina of the trigeminal nerve and to compare them with the conventional cephalometric parameters in different facial skeletal types.

Methods

Cone-beam computed tomography (CBCT) scans and cephalograms from 147 adult patients (57 males and 90 females; mean age, 26.1 years) were categorized as Class I (1° < ANB < 3°), Class II (ANB > 5°), and Class III (ANB < −1°). Seven foramina in the craniofacial area—foramen rotundum (Rot), foramen ovale (Ov), infraorbital foramen, greater palatine foramen, incisive foramen (IF), mandibular foramen (MDF), and mental foramen (MTF)—were identified in the CBCT images. Various linear, angular, and ratio parameters were compared between the groups by using the foramina, and the relationship between the new parameters and the conventional cephalometric parameters was assessed.

Results

The distances between the foramina in the cranial base did not differ among the three groups. However, the Rot-IF length was shorter in female Class III patients, while the Ov-MTF length, MDF-MTF length, and Ov-MDF length were shorter in Class II patients than in Class III patients of both sexes. The MDF-MTF/FH plane angle was larger in Class II patients than in Class III patients of both sexes. Most parameters showed moderate to high correlations, but the Ov-MDF-MTF angle showed a relatively low correlation with the gonial angle.

Conclusions

The foramina of the trigeminal nerve can be used to supplement assessments based on the conventional skeletal landmarks on CBCT images.

Are There Mandibular Morphological Differences in the Various Facial Asymmetry Etiologies? A Tomographic Three-Dimensional Reconstruction Study

PURPOSE

Facial asymmetries (FAs) have been classified according to the mandibular morphological differences to obtain better diagnostic and treatment decisions. The purpose of the present study was to establish diagnostic differentiation among FAs using computed tomography (CT) and 3-dimensional (3D) reconstruction.

MATERIALS AND METHODS

We performed a cross-sectional study of patients with a diagnosis of FA, who had been evaluated by CT and 3D reconstruction in the same clinical center from 2015 to 2018. The following mandibular anatomic characteristics were compared between the 2 sides (deviated side vs contralateral side) and type of FA: condylar length, mandibular ramus length and width, mandibular body length, and symphysis deviation.

RESULTS

The 53 patients included 23 men and 30 women (age range, 16 to 25 years). Six categories of FA were identified: hemimandibular elongation (n = 25), hemimandibular hyperplasia (n = 2), hybrid hyperplasia (n = 3), asymmetric mandibular prognathism (n = 14), asymmetry of the glenoid fossa (n = 2), and functional laterognathism (n = 7). The condylar length and mandibular ramus width were greater in the displaced side than in the contralateral side, with differences of -2.0 ± 2.8 mm (P < .001) and -0.5 ± 1.7 mm (P = .009), respectively. The mandibular body length was greater on the contralateral side (mean difference, 2.1 ± 3.5 mm; P < .001). The symphysis deviation was 5.0 ± 3.4 mm, and those with a hybrid form presented with a greater deviation, with values greater than 10 mm, followed by those with hemimandibular elongation.

CONCLUSIONS

The evaluation of the CT images and 3D reconstructions in patients with FA provided detailed information of the mandibular structure that is useful to compare the differences between sides and to classify the entities associated with FA.

Diagnosis and Surgical Outcomes of Facial Asymmetry According to the Occlusal Cant and Menton Deviation

PURPOSE

Morphologic differences and surgical outcomes were compared between the ipsilateral type of facial asymmetry, in which the menton deviates to the side of the upward frontal occlusal plane (FOP) cant (FOP_UP), and the contralateral type, in which the menton deviates to the side of the downward FOP cant (FOP_DOWN), by using cone beam computed tomography (CBCT) images.

MATERIALS AND METHODS

This retrospective study included consecutive patients with skeletal Class III malocclusion and facial asymmetry who had undergone bimaxillary orthognathic surgery and serial CBCT before, 1 month after, and 1 year after surgery. CBCT images were reconstructed and analyzed for predictor (group and timing) and outcome (CBCT measurements over time) variables. The data were analyzed using independent t tests and paired t tests.

RESULTS

The contralateral group (n = 12) was selected first; the ipsilateral group (n = 12) was selected by matching age, gender, and degree of FOP cant with those of the contralateral group. Before surgery, in the ipsilateral group, the ramal length was longer on the nondeviated (N-Dev) side than on the deviated (Dev) side (P < .05) whereas the mandibular body length showed no significant difference (P > .05). In the contralateral group, the ramal length was longer on the Dev side (P < .05) whereas the mandibular body length was longer on the N-Dev side (P < .01). One year after surgery, most measurements were corrected symmetrically in both groups (P > .05); however, the hemi-lower facial area remained asymmetrical in the contralateral group (P < .05).

CONCLUSIONS

Differences in ramal lengths in the ipsilateral group and mandibular body lengths in the contralateral group between the Dev and N-Dev sides seemed to be the main cause of facial asymmetry. Although facial asymmetry improved after surgery in both groups, asymmetry in the soft tissue remained in the contralateral group 1 year after surgery.

Helmet Treatment of Infants With Deformational Brachycephaly

Deformation of the cranium in infancy represents a spectrum of deformity, ranging from severe asymmetric yet proportional distortion of the skull in plagiocephaly, to nearly symmetric yet disproportional distortion in brachycephaly. As such, the condition is best described as deformational plagiocephaly-brachycephaly with isolated plagiocephaly and/or isolated brachycephaly being at either ends of the spectrum. Due to its symmetric appearance, deformational brachycephaly is often incorrectly dismissed as being less concerning, and it has sometimes erroneously been reported that brachycephaly cannot be treated successfully with a cranial orthosis. We prospectively report on 4205 infants with isolated deformational brachycephaly treated with a cranial orthosis from 2013 to 2017. These results demonstrate that the orthosis is successful in the treatment of deformational brachycephaly with an 81.4% improvement toward normal (95.0 to 89.4) in cephalic index. We furthermore demonstrate that entrance age influences treatment results, with younger infants demonstrating both improved outcomes and shorter treatment times.

Asymmetric Protrusion of the Midface in Young Adults

PURPOSE

This study evaluated midfacial asymmetry using an alternative method that involved comparing bilateral patterns of the zygomaticomaxillary prominence in a young adult population.

MATERIALS AND METHODS

Three-dimensional reconstructed images based on computed tomography scans of 100 Koreans (mean age, 24.7 years) were evaluated with reference to lines spaced at 30° intervals and radiating from the center of an interporion line in a superior view. The surface inclination of the zygomaticomaxillary region was quantified on the same reference lines using a 3-dimensional ruler.

RESULTS

The 30°-interval line (at the level of the zygomaticotemporal suture) was longer on the left side than the right side in both males and females, whereas the left 60°-interval line (at the level of the zygomaticofrontal suture) was longer in females. Comparing the surface protrusion revealed that the zygomaticomaxillary region was more prognathic and inflated on the left side.

CONCLUSION

Functional deviations are considered to be causes of asymmetric craniofacial growth. Postnatal growth allometry across the circummaxillary sutures as elucidated by this study could be useful information in craniofacial surgery.

Facial Malformation in Crouzon's Syndrome Is Consistent with Cranial Base Development in Time and Space

Supplemental Digital Content is available in the text.

Background:

In Crouzon’s syndrome, cranial base deformities begin sequentially in the anterior cranial fossa initially, and later to the posterior cranial base. Facial characteristics are likely related to cranial base development. The temporal correlation between cranial base development and facial features is in need of clarification in Crouzon’s patients, to clarify initial sites of deformity, which may impact surgical decision making.

Methods:

Thirty-six computed tomography scans of unoperated Crouzon’s syndrome patients and 54 controls were included and divided into 5 age-subgroups. All the planes used for analysis were set as perpendicular to a defined “midplane” to offset the confounding factor caused by potential asymmetry.

Results:

The angle between Sella-Nasion plane and Frankfort horizontal plane was significantly increased before 6 months of age (P = 0.014), with an average 70% (P < 0.001) increase ultimately into adulthood. The angle between SN and maxillary plane and the angle between Sella-Nasion and occlusal planes increased consistently through infancy to adulthood (124% and 42%, respectively, both P < 0.001). The relative angle of mandibular plane to Frankfort horizontal plane increased before 6 months (28%, P = 0.007) with a peak timeframe from 2 to 18 years. Facial lateral curvature related measurements indicate the whole face is inclined posteriorly and inferiorly direction in relation to the anterior cranial base.

Conclusion:

Crouzon’s facial malformation development is synchronous and positionally correlational with cranial base deformity. It transmitted from orbit to mandible, with the most evident morphologic changes are in the orbit and midface.

Mandibular asymmetries and associated factors in orthodontic and orthognathic surgery patients

OBJECTIVES

To estimate the prevalence of mandibular asymmetries in orthodontic and orthognathic surgery patients and to investigate demographic and skeletal factors associated with this disharmony.

MATERIALS AND METHODS

Cone-beam computed tomography images of 1178 individuals aged 19 through 60 years with complete dentitions were analyzed. Outcomes were classified as relative mandibular symmetry, moderate asymmetry, and severe asymmetry. Factors recorded included sex, age, side of mandibular deviation, sagittal jaw relationship, vertical skeletal pattern, angle of the cranial base, and maxillary asymmetry. Ordinal logistic regression was used to estimate simple and adjusted odds ratios (OR) for the individuals with moderate and severe mandibular asymmetry, as well as 95% confidence intervals.

RESULTS

Prevalence values of 55.2%, 27.2%, and 17.6% were observed for relative mandibular symmetry, moderate asymmetry, and severe asymmetry, respectively. An independent association with the side of mandibular deviation and the presence of maxillary asymmetry was observed, both for subjects with moderate mandibular asymmetry (left side: OR = 1.50; 95% CI: 1.01-2.24 / maxillary asymmetry: OR = 2.07; 95% CI: 1.11-3.76) and for those with severe asymmetry (left side: OR = 2.09; 95% CI: 1.27-3.44 / maxillary asymmetry: OR = 4.93; 95% CI: 2.64-9.20).

CONCLUSIONS

Moderate and severe mandibular asymmetries were present in 44.8% of the sample, being associated with the side of mandibular deviation and with maxillary asymmetry.

Accuracy of two midsagittal planes in three-dimensional analysis and their measurement in patients with skeletal mandibular deviation: a comparative study

Our aim was to evaluate the accuracy of two midsagittal planes (MSP) to provide a better reference plane for studying the 3-dimensional structural symmetry in patients with skeletal mandibular deviation. Thirty adult patients with facial asymmetry were admitted to the Department of Orthodontics, Hospital of Stomatology, between January 2015 and 2017. The DICOM data were collected and reconstructed using ProPlan CMF^® 2.0 (Materialise). Two sets of reference planes were set up. In the orbital margin plane group, the plane crossing the nasion (N) point and perpendicular to the frontozygomatic (FZ) suture line was used as the MSP. In the skull base plane group, the MSP was established using the sella turcica (S), N, and basion (Ba). The distances from the craniofacial skeletal and soft tissue midline landmarks to the two MSP were separately measured, and the significance of differences between measurements corresponding to two reference planes were assessed using the paired t test. Except for the posterior nasal spine (PNS)-MSP, the distances from other soft and hard tissue landmarks to the MSP in the orbital margin plane group were significantly shorter than those in the skull base plane group. In the 3-dimensional measurement analysis, the skeletal and soft tissue anatomical midline landmarks were closer to the MSP in the orbital margin plane group. The MSP crossing point N, perpendicular to the FZ suture line, was more accurate and suitable.

Three-dimensional analysis of cranial base morphology in patients with hemifacial microsomia

BACKGROUND

Many researchers have studied the relationship between facial asymmetry and cranial base morphology, but they have failed to reach a consensus. In this study, we aimed to verify whether the cranial base is involved in hemifacial microsomia (HFM).

METHODS

We included 66 patients with HFM who were treated at the Plastic and Reconstructive Surgery Department of Shanghai Ninth People's Hospital from January 2013 to October 2016. The patients were divided into three groups according to Pruzansky and OMENS classifications, separately. The controls were 20 patients diagnosed with mandibular angle hypertrophy but with no facial asymmetry. Angular and linear measurements of the cranial base were obtained for all patients.

RESULTS

The two classification methods yielded similar results. The intersection angle between two planes showed differences in the severe group. In the moderate and severe groups, the middle and posterior cranial angles were significantly different and the CIP and SP lengths were shorter in the affected side. Landmarks such as the carotid canal and internal acoustic canal could be considered as references.

CONCLUSIONS

The cranial base is involved in hemifacial microsomia. This relationship supports the hypothesis of HFM pathogenesis and opens new avenues to classification methods.

Association between 3-dimensional mandibular morphology and condylar movement in subjects with mandibular asymmetry

INTRODUCTION

The purpose of this study was to evaluate the hypothesis that 3-dimensional mandibular morphology is correlated with condylar movement in patients with mandibular asymmetry.

METHODS

Subjects were classified into 2 groups (n = 25 each): mandibular asymmetry with a menton deviation greater than 4 mm and no mandibular asymmetry with a menton deviation less than 4 mm. Linear and volumetric measurements of 3-dimensional mandibular morphology were recorded using computed tomography. Mandibular functional movement was recorded by computerized axiography (CADIAX; Gamma Dental, Klosterneuburg, Austria), and condylar path length, sagittal condylar inclination, and transverse condylar inclination on protrusion were measured. We calculated side-to-side asymmetry (shifted side vs nonshifted side) in mandibular morphology and assessed condylar movement by using an asymmetry ratio (nonshifted side/shifted side).

RESULTS

Significant differences in mandibular morphology and condylar movement were found between the 2 groups. In the group with menton deviation greater than 4 mm, significant correlations were found between the asymmetry ratio of mandibular morphology and condylar movement: ie, condylar path length and transverse condylar inclination. No significant correlations were found between any of these measurements in the group with menton deviation less than 4 mm.

CONCLUSIONS

In support of our hypothesis, the results suggested that 3-dimensional mandibular morphologic asymmetry is associated with condylar movement in subjects with mandibular asymmetry.

Craniofacial features affecting mandibular asymmetries in skeletal Class II patients

OBJECTIVES

The aim of this study was to evaluate the characteristics affecting different intensities of mandibular asymmetry in skeletal Class II adults using three-dimensional images. This study is clinically relevant since it allows professionals to evaluate the morphological components related to these deformities and more carefully obtain correct diagnosis and treatment plan for such patients.

METHODS

Cone-beam computed tomography data of 120 Class II patients (40 with relative symmetry, 40 with moderate asymmetry, and 40 with severe asymmetry) were imported to SimPlant Ortho Pro^® 2.0 software (Dental Materialise, Leuven, Belgium). Three reference planes were established and linear measurements were performed from specific landmarks to these planes, comparing the deviated side and the contralateral side in each group, as well as the differences between groups. The correlation between midline mandibular asymmetry and other variables was also evaluated. Statistical analyses considered a significance level of 5%.

RESULTS

Comparing the values obtained on the deviated side and on the contralateral side, there were significant differences for patients with moderate asymmetry and severe asymmetry. However, differences were seen more often in severe mandibular asymmetries. In those patients, there was a significant correlation of the gnathion deviation with lower dental midline deviation, difference in the lateral gonion positions, difference in the mandibular rami heights, and difference in the jugale vertical displacements.

CONCLUSIONS

For skeletal Class II patients with mandibular asymmetry, some craniofacial features are related to chin deviation and require proper evaluation, including the bilateral differences in the ramus height, mandibular body length, transverse and vertical positioning of the gonion and jugale points.

The genial tubercle: A prospective novel landmark for the diagnosis of mandibular asymmetry

INTRODUCTION

Identifying menton (Me) on posteroanterior cephalograms and three-dimensional (3D) cone-beam computed tomography (CBCT) images is difficult, because the midpoint of the symphyseal area is not identifiable after the mandibular symphysis fuses at an early age. The aim of this study was to evaluate the reliability of the identification of the genial tubercle (GT) in patients with mandibular asymmetry and to compare it with that of the traditional landmark, Me.

METHODS

The samples comprised 20 CBCT images of adults with mandibular asymmetry. Two examiners performed the identifications and measurements. Me and GT were marked, and the anteroposterior, vertical, and transverse distances to the three reference planes were measured on 3D-reconstructed CBCT images. The intra- and inter-examiner reliability of landmark identification of Me and GT were assessed using the intraclass correlation coefficient (ICC) and Bland-Altman plots.

RESULTS

The Me and GT landmarks showed excellent reliability (ICC ≥ 0.993) three-dimensionally. In the transverse evaluation, the ICC values of the GT (range, 0.997-0.999) tended to be slightly higher than those of Me (range, 0.993-0.996). In the Bland-Altman plots for the two separate assessments, Me showed a maximum error of 1.76 mm in the transverse direction, whereas the GT showed a maximum error of 0.96 mm in the 95% limit.

CONCLUSIONS

Our results suggest that both Me and GT are clinically reliable and equally useful landmarks for the evaluation of mandibular asymmetry on CBCT images.

Internet Access to Advanced 3-Dimensional Software for the Prototyping and Design of Complex and Precise Custom Mandibular Implants

A large percentage of patients with microgenia requesting chin augmentation also exhibit an associated component of micrognathia with either narrow or acutely angled mandibular bodies and/or hypoplasia of the gonial angles. Augmentation of the face and mandible should optimally address all regions of deficiency and can now be customized with a high degree of accuracy using software that can be accessed over the Internet. We discuss the advanced capabilities of merging a sophisticated software system (Geometric Freeform® software; Morrisville, North Carolina) and computed tomography (CT) imaging to design precise, total custom mandibular implants over the Internet without the need for physical modeling. In revision cases, this process also allowed for the implant to be removed and replaced within a single-stage procedure. We retrospectively reviewed 34 cases in an outpatient surgical center and described the preoperative evaluation, imaging protocol, customization process, and surgical procedure for custom mandibular and custom total mandibular augmentation. Between January 2004 and June 2015, 25 patients underwent total mandibular augmentation and 9 had custom extended mandibular angle and body augmentation. All patients received solid silicone rubber implants that were customized using virtual or acrylic prototypes digitally designed via real-time video conferencing. This custom process achieved an enhanced level of satisfaction with an improved ability to achieve symmetry based on quantitative measurements during the interactive design process, alloplastic facial implants can be customized with a high degree of accuracy, precision, and fit by combining the capabilities of 3-dimensional CT and advanced computer design software accessed via the Internet.

A comparative study of the deviation of the menton on posteroanterior cephalograms and three-dimensional computed tomography

Purpose

Facial asymmetry has been measured by the severity of deviation of the menton (Me) on posteroanterior (PA) cephalograms and three-dimensional (3D) computed tomography (CT). This study aimed to compare PA cephalograms and 3D CT regarding the severity of Me deviation and the direction of the Me.

Materials and Methods

PA cephalograms and 3D CT images of 35 patients who underwent orthognathic surgery (19 males and 16 females, with an average age of 22.1±3.3 years) were retrospectively reviewed in this study. By measuring the distance and direction of the Me from the midfacial reference line and the midsagittal plane in the cephalograms and 3D CT, respectively, the x-coordinates (x₁ and x₂) of the Me were obtained in each image. The difference between the x-coordinates was calculated and statistical analysis was performed to compare the severity of Me deviation and the direction of the Me in the two imaging modalities.

Results

A statistically significant difference in the severity of Me deviation was found between the two imaging modalities (Δx=2.45±2.03 mm, p<0.05) using the one-sample t-test. Statistically significant agreement was observed in the presence of deviation (k=0.64, p<0.05) and in the severity of Me deviation (k=0.27, p<0.05). A difference in the direction of the Me was detected in three patients (8.6%). The severity of the Me deviation was found to vary according to the imaging modality in 16 patients (45.7%).

Conclusion

The measurement of Me deviation may be different between PA cephalograms and 3D CT in some patients.

Positional symmetry of porion and external auditory meatus in facial asymmetry

Background

The porion (Po) is used to construct the Frankfort horizontal (FH) plane for cephalometrics, and the external auditory meatus (EAM) is to transfer and mount the dental model with facebow. The classical assumption is that EAM represents Po by the parallel positioning. However, we are sometimes questioning about the possible positional disparity between Po and EAM, when the occlusal cant or facial midline is different from our clinical understandings. The purpose of this study was to evaluate the positional parallelism of Po and EAM in facial asymmetries, and also to investigate their relationship with the maxillary occlusal cant.

Methods

The 67 subjects were classified into three groups. Group I had normal subjects with facial symmetry (1.05 ± 0.52 mm of average chin deviation) with minimal occlusal cant (<1.5 mm). Asymmetry group II-A had no maxillary occlusal cant (average 0.60 ± 0.36), while asymmetry group II-B had occlusal cant (average 3.72 ± 1.47). The distances of bilateral Po, EAM, and mesiobuccal cusp tips of the maxillary first molars (Mx) from the horizontal orbital plane (Orb) and the coronal plane were measured on the three-dimensional computed tomographic images. Their right and left side distance discrepancies were calculated and statistically compared.

Results

EAM was located 10.3 mm below and 2.3 mm anterior to Po in group I.  The vertical distances from Po to EAM of both sides were significantly different in group II-B (p = 0.001), while other groups were not. Interside discrepancy of the vertical distances from EAM to Mx in group II-B also showed the significant differences, as compared with those from Po to Mx and from Orb to Mx.

Conclusions

The subjects with facial asymmetry and prominent maxillary occlusal cant tend to have the symmetric position of Po but asymmetric EAM. Some caution or other measures will be helpful for them to be used during the clinical procedures.

Cone-beam computed tomography based evaluation of rotational patterns of dentofacial structures in skeletal Class III deformity with mandibular asymmetry

Objective

The purpose of this study was to assess rotational patterns of dentofacial structures according to different vertical skeletal patterns by cone-beam computed tomography (CBCT) and analyze their influence on menton deviation in skeletal Class III deformity with mandibular asymmetry.

Methods

The control group consisted of 30 young adults (15 men, 15 women) without any severe skeletal deformity. The asymmetry group included 55 adults (28 men, 27 women) with skeletal Class III deformity and at least 3-mm menton deviation from the midsagittal plane; it was divided into the hyperdivergent and hypodivergent subgroups using a mandibular plane angle cutoff of 35°. Fourteen rotational variables of the dental arches and mandible were measured and compared among the groups. Correlations between menton deviation and the other variables were evaluated.

Results

The asymmetry group showed significantly larger measurements of roll and yaw in the mandible than the control group. The hypodivergent subgroup showed significant differences in maxillary posterior measurements of yaw (p < 0.01) and maxillary anterior shift (p < 0.05) compared with the hyperdivergent subgroup. All the mandibular measurements had significant correlations with menton deviation (p < 0.01). Most measurements of roll were positively correlated with one another (p < 0.01). Measurements of yaw and roll in the posterior regions were also positively correlated (p < 0.05).

Conclusions

Menton deviation in skeletal Class III deformity with mandibular asymmetry is influenced by rotation of mandibular posterior dentofacial structures. The rotational patterns vary slightly according to the vertical skeletal pattern.

Medidas faciais em indivíduos adultos sem queixas orofaciais: compatibilidade entre medidas antropométricas e percepção facial

OBJETIVO: verificar a compatibilidade entre os achados de medidas faciais mensuradas pelo paquímetro e a percepção das características faciais realizada subjetivamente por um avaliador experiente. MÉTODOS: foram avaliados 24 sujeitos do sexo feminino e 24 do sexo masculino, pareados por sexo e idade, sem queixas morfológicas e funcionais do sistema estomatognático. Foram avaliados os aspectos de simetria entre os terços médio e inferior, altura e largura da face, e canto externo dos olhos direito e esquerdo às comissuras do lábio direita e esquerda, respectivamente. Cada medida foi realizada três vezes por paquímetro digital para consideração da média entre estes valores, considerando-se assimétricas comparações com diferenças superiores à 4 milímetros. A largura da face foi obtida por meio do paquímetro digital adaptado com prolongamento de 10 centímetros. Já a avaliação da percepção das características faciais foi realizada por um avaliador cegado quanto às medidas obtidas, devendo assinalar simetrias e assimetrias nestes mesmos aspectos avaliativos. RESULTADOS: por meio do teste de concordância de Kappa e Qui-quadrado, pode-se verificar uma boa compatibilidade entre as avaliações realizadas, demonstrando-se a fidedignidade entre os métodos utilizados. Além disso, verificou-se que existe uma relação entre a simetria dos terços da face e a atribuição da tipologia facial na avaliação perceptiva, observando-se simetria em faces médias e curtas e ausência de um padrão determinante para faces longas. CONCLUSÃO: a caracterização da simetria facial por paquímetro apresenta uma boa compatibilidade com a percepção subjetiva de um avaliador experiente.

Cranial-base morphology in adults with skeletal Class III malocclusion

INTRODUCTION

The objectives of this study were to clarify the characteristics of cranial-base morphology in adults with skeletal Class III malocclusion and investigate factors relating to the establishment of a skeletal Class III malocclusion.

METHODS

Initial lateral cephalograms of women were examined. Subjects with an ANB angle of 0° to 4°, normal overjet and overbite, and a Class I molar relationship were classified as Class I (n = 86). Those with an ANB angle less than -1°, a Wits appraisal less than 2 mm, a negative overjet, and a Class III molar relationship were the Class III group (n = 86) in this study. Angular, linear, and coordinate measurements were made. Multivariate analysis of variance and the Student t test were used to analyze significant differences between the 2 groups. Discriminant analysis, logistic regression analysis, and decision analysis were used to identify which cranial-base and maxillomandibular variables influenced the establishment of a skeletal Class III malocclusion.

RESULTS

The Class III group had smaller values for NSBa, SeSBa, FH-SSe, and FH-SBa. Sphenoidale and basion were more inferior and anterior than those of the Class I group. There was no difference in the anterior and posterior cranial-base lengths between the groups. Greater mandibular length was the first major characteristic in the Class III group, followed by smaller values for SeSBa and NSBa.

CONCLUSIONS

Cranial-base morphology in adults with a skeletal Class III malocclusion is different from that in a skeletal Class I malocclusion. Smaller cranial-base angles, steeper posterior cranial bases, more inferiorly positioned sphenoidale, and more anteriorly positioned basion are major characteristics of skeletal Class III malocclusions. These characteristics play important roles in the establishment of a skeletal Class III malocclusion.