Mandibular Volume Research Articles

Evaluation of the Relationship Between Morphology, Volume, and Density of the Mandible and Dentofacial Vertical Dimension Using Cone Beam Computed Tomography

Objective: To evaluate the relationship between mandibular shape, mandibular bone density, cortical bone thickness, and condylar volume and facial height using a cone-beam computed tomography (CBCT). Material and Methods: Fifteen female patients (16-25 years old) were included in this study. The following measurements were performed on CBCT radiographs; inter-canine and inter-molar width of the mandible at three vertical points (alveolar crest, apex and basal bone), mandibular cortical bone thickness in disto molar and canine sections, bone density of the mandibular body and condylar volume. Afterward, subjects were divided into short face, normal and long face groups according to the Frankfort-mandibular plane angle (FMA) measured on lateral cephalograms obtained from CBCTs. Data were analyzed using Pearson correlation, one-way ANOVA, and post-hoc analysis. Results: The inter-canine width of the mandible at the apical point in long face subjects was greater than in the other groups. Likewise, the cortical bone thickness was significantly higher in long face patients compared to the short face and normal subjects. There was no statistically significant difference in mandibular density or condylar volume between patients with various vertical heights (p>0.1). Conclusion: Vertical growth pattern is correlated with mandibular morphology to some extent.

Objectifying Micrognathia Using Three-Dimensional Photogrammetric Analysis.

Micrognathia occurs isolated and as part of entities like Robin sequence (RS). An objective measurement of mandible size and growth is needed to determine the degree of micrognathia and enable a comparison of treatment outcomes. A pilot study was conducted to investigate the usability of 3-dimensional (3D) facial photogrammetry, a fast, noninvasive method, to estimate mandible size and growth in a small cohort of newborns and infants. Exterior mandibular volume was estimated using a tetrahedron defined by 4 facial landmarks. Twelve patients with RS with different etiologies were selected and photogrammetric images were obtained prospectively in 3 patients with RS in whom mandibular growth in the first year of life was determined. We used 3 tetrahedra defined by 6 landmarks on mandibular computed tomography (CT) scans to estimate an interior mandibular volume, which we compared to the exterior mandibular volume in 10 patients. The exterior mandibular volume using 3D photography could be determined in all patients. Signature heat maps allowed visualization of facial dysmorphism in 3D; signature graphs demonstrated similarities of facial dysmorphism in patients with the same etiology and differences from those with other diagnoses and from controls. The correlation between interior (3D photogrammetry) and exterior mandibular volumes (CT imaging) was 0.8789. The 3D facial photogrammetry delineates the general facial characteristics in patients with different syndromes involving micrognathia, and can objectively estimate mandibular volume and growth, with excellent correlation with bony measurement. It has been concluded that 3D facial photogrammetry could be a clinically effective instrument for delineating and quantifying micrognathia.

Craniofacial Phenotyping in Chinese and Caucasian Patients With Sleep Apnea: Influence of Ethnicity and Sex.

Craniofacial abnormalities are a risk factor for obstructive sleep apnea (OSA). We have previously shown that phenotypic information derived from craniofacial photographs predict OSA in sleep clinic populations. However, there are likely ethnic and sex differences in craniofacial phenotypes related to OSA. We aimed to assess the use of craniofacial photography to identify interactions between OSA, ethnicity, and sex in craniofacial phenotype. Frontal and profile craniofacial photographs were analyzed from two sleep clinic populations of different ethnicity (Hong Kong Chinese, Australian Caucasians). OSA was defined as apnea-hypopnea index (AHI) > 10 events/h. Ten craniofacial measurements (three angles relating to jaw position and seven ratios describing proportions of the face) were examined for interactions between OSA status and sex or ethnicity) using factorial analysis of variance. A total of 363 subjects (25% female) were included (n = 200 Chinese, n = 163 Caucasian), of which 33% were controls. There were two-way interactions for OSA with both sex (mandibular plane angle [F = 7.0, P = .009], face / eye width ratio [F = 4.7, P = .032], maxillary / mandibular volume ratio [F = 9.2, P = .003]) and ethnicity (face / nose width ratio [F = 4.0, P = .045], mandibular width / length ratio [F = 5.1, P = .024], maxillary / mandibular volume ratio [F = 11.0, P = .001]). We provide evidence of ethnic and sex differences in facial phenotype related to OSA. Furthermore, we demonstrate that craniofacial photography can be used as a phenotypic tool to assess these differences and allow investigation of OSA phenotypes in large samples. This has relevance to personalizing OSA recognition strategies across different populations.

A Volumetric Assessment Using Computed Tomography of Canine and First Molar Roots in Dogs of Varying Weight.

Mandibular volume and tooth root volumes were shown to increase at different rates at locations containing the roots of the canine (C) and mesial and distal roots of the first molar (M1). Thirty-six dogs were included in this study. Data were generated using computed tomography at locations of the mandible involving the roots of the C and M1 teeth. Software was used to trace the external surface of the mandible, calculating the volume of the mandible at each location. Similar techniques were used to trace and calculate the volume of the C and M1 roots. Mandible volume, tooth root volume, and root percentage of mandible volume were analyzed and compared using the slopes of the best fit line. At the M1 mesial and distal roots, mandible volume ( P < .001) and root volume ( P < .001) were both noted to increase, with increasing weight at different rates. The rate of change in the root percentage by weight of M1 roots was not different ( P = .214). Each location demonstrated a different increasing rate of change for mandibular volume and increasing root volume. Results show that as patient's weight increases, the mandible and root volumes increase at different rates. Root percentage by volume at all three locations was noted to decrease by the same rate. Canine and M1 roots are proportionally larger than the supporting mandibular bone in smaller patients. Care should be taken to recommend periodontal disease prevention for owners of small dogs and consideration made when performing extractions or other surgery that may destabilize the mandible.

Mandibular growth in survivors of pediatric parotid gland carcinoma treated with interstitial brachytherapy.

The aim of the study was to present long-term results of mandibular growth in pediatric parotid gland carcinoma survivors treated with interstitial brachytherapy. Twenty-five survivors of pediatric parotid gland carcinoma treated with iodine-125 seed interstitial brachytherapy were included for quantitative analysis, including three dimensional (3D) cephalometry and measurement of mandibular volume. 3D cephalometry showed that the median fore-and-aft increments of the lengths of the condyle, the ramus, and the body of the mandible were 1.23, 0.19, and 1.66mm for the affected side, respectively, and were 1.37, 1.95, and 3.42mm for the unaffected side, respectively. The difference in increments of the ramus was statistically significant between the affected side and the unaffected side (P=0.003; P<0.05). Moreover, mandibular volume measurements showed that the median fore-and-aft increments of the volumes of the condyle, the ramus, and the body of the mandible were 290.62, 220.14, and 1706.40 mm3 for the affected side, respectively, and were 269.15, 370.40, and 1469.86 mm3 for the unaffected side, respectively. The difference in increments was statistically significant between the affected side and the unaffected side for the ramus (P=0.005; P<0.05) and the body (P=0.043; P<.05). Mandibular growth was affected by interstitial brachytherapy, especially for the ramus, in pediatric parotid gland carcinoma survivors treated with interstitial brachytherapy. Nevertheless, the impact was mild in these survivors.

Using a single cone-beam computed tomography scan to obtain full occlusal details, with the mandible in centric relation and maximum intercuspation.

One obstacle with the implementation of digital technology in orthodontics is the acquisition of occlusal details while maintaining the mandible in the full interdigitation position. With 1 cone-beam computed tomography (CBCT) scan of the patient and 1 digital scan of the patient's dental models in occlusion, it might be possible to obtain full occlusal details and generate 2 volumes, with the mandible in centric relation and maximum intercuspation positions. The purpose of this article was to describe the technique. Orthodontic models of enrolled subjects were digitized in maximum intercuspation. They wore splints that were initially 2mm thick before CBCT imaging. On the CBCT volume, the mandible is separated from the rest of the skull, and the digitized dental model in maximum intercuspation is registered on the skull volume. The separated mandibular volume is then registered on the mandibular dentition using the tooth surfaces as a guide. Two CBCT volumes are rendered: original scan with teeth in minimal disclusion and the constructed one with teeth in maximum interdigitation. Mobilizing digital technology in orthodontics allows the acquisition of crucial occlusal details while sparing patients an extra radiation dose from the CBCT.

Radiobiological Analysis for Osteoradionecrosis in Patients Treated With IMRT for Head and Neck Cancer: A Department of Veterans Affairs Experience

Previous publications by our group regarding osteoradionecrosis (ORN) induced by head and neck (H&N) radiation therapy (RT) have focused on the total physical dose deposited at the lesion site within the mandible. Furthermore, there seems to be a volume effect predicting increasing chance of ORN with a larger proportion of mandible receiving higher total dose. As with most published results, a relatively scarce number of cases limits the validity of findings, and biological consequence of spatial variation of dose per fraction is often ignored. In this study, we have pooled cases of ORN from two Veteran Affairs (VA) radiation oncology facilities, and analyze the pattern of failure based on the concept of biologically effective dose (BED). Ten patients treated with H&N radiation therapy were identified to have ORN (median time from RT completion to diagnosis of ORN was 6 months; range: 3.2 to 52.8 months). All were male veterans, with median age of 63.5 when receiving initial treatment. Five had primary oropharyngeal cancer, 3 had oral cavity cancer, and 2 were treated for unknown H&N primary. All ORN sites were localized toward the posterior portion of the mandible or retromolar area. Concurrent platinum-based chemotherapy was given to 5 patients and Cetuximab to 3. One had salvage mandibulectomy before developing ORN, the other had partial glossectomy before being treated with hypofractionated RT along with Cetuximab. Dosimetric outcomes were analyzed retroactively for 8 cases with available detailed treatment plans, using BED and linear-quadratic equivalent dose based on 2-Gy per fraction (LQED2). The average LQED2 based on the prescribed fractionation scheme was 69.3±1.4 Gy (BED of 115.6±2.4 Gy3). At the ORN lesion site, the average LQED2 was 76.0±4.1 Gy (BED of 126.7±6.8 Gy3), representing a 9.7% increase over the prescribed dose. For the entire mandible (average total volume of 74.0±14.5 cc), the average percent volumes receiving minimal LQED2 of 70 (V70) Gy (corresponding to BED of 116.7 Gy3) was 12.4±15.5%, corresponding to an absolute mandibular volume of 8.3±10.1 cc. Thus, while the mandible might be considered as a serial organ as far as ORN is concerned, it might be associated with a moderate volume effect. ORN can result from increased LQED2 or BED which may not be conspicuous from a dosimetric plan based solely on physical dose display. This study demonstrates the utilization of radiobiologically sound dosimetry which clinicians can use to quantify risk of late complications due to the “double trouble” arising from altered fractionation schemes. For the mandible, DVH guidelines based on BED or LQED2 might be better representations to predict true incidence of ORN, and useful when constructing the dose-response relation as a normal-tissue complication probability (NTCP) curve.

Quantitative evaluation of facial hypoplasia and airway obstruction in infants with syndromic craniosynostosis: relationship with skull base and splanchnocranium sutural pattern.

Craniosynostostic syndromes are due to multisuture synostoses and affect the entire craniofacial skeleton. This study analyzed the facial complex and airways to quantify the relationship between insufficient facial growth, airways obstruction, and the sutural pattern of the splanchnocranium and cranial fossae. Preoperative high-resolution CT images in 19 infants with syndromic craniosynostosis were quantitatively analyzed. Because all children showed involvement of minor sutures/synchondroses coursing in the posterior cranial fossa, they were divided into three groups according to the synostotic involvement of "minor" sutures/synchondroses coursing in anterior (ACF) and middle (MCF) cranial fossae: group 1 (ACF), group 2 (MCF), and group 3 (ACF-MCF). Analysis of the facial complex and airway was performed. Each group was compared with age-matched healthy subjects. Premature closure of skull base synchondroses of ACF and MCF was found only in groups MCF and ACF-MCF. Group MCF showed synostosis in the posterior branch of the coronal ring and reduced anterior hemifossae lengths while group ACF-MCF showed synostosis in the anterior branch of the coronal ring and reduced middle hemifossae lengths. No group showed reduced maxillary or mandibular volumes but group MCF showed synostosis of the zygomaticomaxillary sutures and maxillary retrusion. All groups showed reduced airway volume but group 2 had a higher degree of airway hypoplasia. The skull base synostotic process drives the changes in facial complex growth and airway obstruction. Premature closure of synchondroses/sutures in the posterior branch of the coronal ring causes insufficient facial growth, maxillary retrusion, and more severe airway reduction.

Current Therapeutic Options for Implant-Supported Rehabilitation of Severely Atrophic Mandibles

The implant-supported rehabilitation of atrophic mandibles (AM) with severe bone resorption is challenging for both surgical and prosthetic procedures due to the high risk of mandible fracture during implant surgery and postoperatively due to the masticatory load. The aim of case presentations was to demonstrate treatment alternatives for patients with AM who required oral rehabilitation with osseointegrated implants (OIs) according to the residual mandibular bone volume. When bone is 9 mm in height, the ideal treatment is the use of narrow, short OIs. When the bone height is 5 to &lt; 9 mm, mandibular reinforcement with reconstruction plates using the intraoral approach and simultaneous placement of osseointegrated implants are proposed. In cases where bone height is &lt; 5 mm, the choice of treatment is mandibular reconstructive surgery with an autogenous bone graft and biomaterials. The fundamental principles of this protocol are to reduce the morbidity and complications associated with the surgical procedure, which would reduce both the time and cost of full dental rehabilitation. The choice of the technique for mandibular reconstruction should be indicated according to the magnitude of the atrophy.

Volumetric mandibular change after angle ostectomy and outer cortex grinding

BackgroundMandibular angle ostectomy is one of the most common surgical procedures for facial contouring in Asian women. However, some patients complain about mandibular angle hypertrophy recurrence after surgery. The present study evaluated volumetric change of the mandible after angle ostectomy and outer cortex grinding. MethodsTwenty-four patients who underwent bilateral mandibular angle ostectomy and outer cortex grinding from 2013 to 2016 were enrolled. Three-dimensional computed tomography data were used to evaluate the preoperative, immediate postoperative, and long-term follow-up (≥12 months) volume of the mandible. The volumetric change between different groups was analyzed. ResultsThe results of software measurements showed that the preoperative mandible volume was significantly larger than immediate and long-term postoperative volumes (P = 0.000), and there was no significant difference between immediate and long-term postoperative mandibular volume (P > 0.05). Mean bone regeneration at long-term follow-up was 1.42% ± 3.84% for those who underwent mandibular angle ostectomy with outer cortex grinding alone and 1.69% ± 2.45% on the left and 2.59% ± 3.61% on the right sides of patients who underwent this procedure along with advancement genioplasty. ConclusionMandibular angle ostectomy can effectively change the facial contour to achieve a more oval-shaped face favored by most Asians. Postoperative bone remodeling is mostly regenerated, although bone absorption did occur. However, the mean bone volume did not reach preoperative levels, and the difference between preoperative and long-term postoperative bone volume at follow-up (≥12 months) was significant.

The Pierre Robin Mandible is Hypoplastic and Morphologically Abnormal.

For Pierre Robin sequence (PRS) patients, there is incomplete characterization of 3D differences and effects of mandibular distraction osteogenesis (MDO) on the mandible compared to normal controls. PRS infants who underwent MDO at 2 craniofacial referral centerals with pre- and postoperative computed tomography (CT) scans were identified. A group of age-matched control patients with CTs were identified in the PACS database. Demographic and perioperative data were recorded. Mandibular lengths, angles, and volumes were measured. Morphologic and outcomes data were analyzed in a case-control comparison. Sixty-three CT scans were analyzed. Fifteen pre-op PRS patient and 15 control CTs were well matched in terms of age and sex. Mandibular volume (78%), ramus length (87%), and body length (95%) were all decreased in the PRS patients. Anterior symphyseal angle (84%) was significantly reduced in PRS patients while mandibular angle (102%) was maintained. Eighteen post-op PRS patient and 15 control CTs were well matched in terms of age and gender. Mandibular volumes (106%) were normalized following distraction with shorter mandibular rami (88%) and longer mandibular bodies (109%). Postoperatively, mandibular angle (100%) and anterior symphyseal angle (99%) were ultimately indistinguishable from controls. The mandible in PRS is dysmorphic compared to age-matched controls. Overall, they have a smaller volume, shorter ramus, and an obtuse symphyseal angle. MDO improves mandibular volume and normalizes the symphyseal angle, but results in a longer mandibular body and shorter mandibular ramus.

Osteoradionecrosis of the mandible in patients with oropharyngeal carcinoma treated with intensity-modulated radiotherapy.

Osteoradionecrosis (ORN) of the mandible is a late toxicity affecting patients treated with radiotherapy for head and neck malignancies. To the authors' knowledge, ORN has no standardized grading system and its reporting is based on retrospective findings in heterogeneous patient populations. The rate of ORN in the era of intensity-modulated radiotherapy (IMRT) still is unknown. The authors report the incidence of ORN from prospectively collected data regarding 1196 patients who were diagnosed with squamous cell carcinoma of the oropharynx and treated with curative-intent IMRT, with or without concomitant systemic treatment, from January 2005 to December 2014. Each case of ORN was graded according to its severity. Clinical and dosimetric comparisons were performed between patients with ORN and a matched control cohort of patients without ORN. The actuarial rate of ORN of the mandible was 3% at 1 year, 5% at 3 years, and 7% at 5 years. On multivariable analysis, smoking (hazard ratio, 1.9; 95% confidence interval, 1.07-3.4 [P = .03]) and T classification (hazard ratio, 1.78; 95% confidence interval, 1.02-3.1 [P = .041]) were found to be statistically significant risk factors. The presence of cardiovascular comorbidities, use of bisphosphonates, and pre-IMRT dental extractions were found to be different between the matched cohorts. The mandibular volume receiving 50 grays (Gy) (in cm3 ) and the volume receiving 60 Gy (in cm3 ) were found to be associated with ORN on multivariable analysis in the matched cohort patients receiving an IMRT regimen of 2 Gy per fraction. ORN is relatively uncommon among patients with oropharyngeal carcinoma who are treated with IMRT, but continues to occur beyond 5 years after treatment. Modifiable risk factors that are associated with higher rates of ORN include smoking and the use of bisphosphonates. Minimizing the volumes of the mandible receiving >50 Gy or > 60 Gy also may have an effect on the ORN rate. Cancer 2017;123:3691-3700. © 2017 American Cancer Society.

Relationship Between Mandibular Ramus Height and Masticatory Muscle Function in Patients With Unilateral Hemifacial Microsomia.

To clarify the relationship between mandibular ramus height and function of masticatory muscles in patients with hemifacial microsomia. Retrospective study of imaging and physiological data. Images and physiological data were obtained from the records of Sapporo Medical University Hospital. A total of 29 patients with hemifacial microsomia who showed Pruzansky grades I, II deformity. Mandibular ramus height and masticatory muscle volume were evaluated with multi-detector row computed tomography. The electromyographic value was measured by the K7 Evaluation System. The hemifacial microsomia patients were classified into three groups based on the mandibular ramus height ratio of the affected and unaffected sides: group 0, >1.00; group 1, 1.00 to 0.85; group 2, <0.85. The Tukey-Kramer method and Games-Howell method were used to determine correlations between parameters. Decreased mandibular ramus height was significantly correlated with both reduced electromyographic values of the masseter muscle (P < .05) and the amount of mandibular lateral deviation at the time of maximum opening (P < .05) on the affected side. These differences were prominent in unilateral hemifacial microsomia patients classified as group 2. Decreased mandibular ramus height may cause dysfunction of the masseter muscles but not the temporal muscle on the affected side in patients with hemifacial microsomia.

Does Mandibular Distraction Vector Influence Airway Volumes and Outcome?

The goal of mandibular distraction in the Pierre-Robin sequence is to maximally expand the oropharyngeal airway. It has been hypothesized that a steep oblique distraction vector might allow greater airway enlargement compared with horizontal distraction. This study compared vector orientation in relation to airway volume and overall clinical outcome. Micrognathic infants who underwent mandibular distraction with sufficient computed tomographic data were retrospectively reviewed. Demographic, diagnostic, perioperative, and distraction data were recorded. Groups were separated based on distraction vector (group 1, horizontal; group 2, oblique). Airway and mandibular volumes were measured using Mimics (Materialise, Leuven, Belgium). Morphologic and outcomes data were analyzed. Statistics involved 2-tailed t test, Pearson correlation, and analysis of covariance (ANCOVA). Mean age at distraction was 40days, with devices maintained for 82days on average. Fifty percent of patients were girls and 65% had cleft palate. Forty computed tomograms were analyzed. Airway (1,234 vs 3,501mm3; P < .01) and mandibular (5,457 vs 11,827mm3; P < .01) volumes, minimal airway area (12.5 vs 63.7mm2; P < .01), and posterior airway space distance (2.3 vs 9.8mm; P= .04) were significantly increased after distraction. Patients also had clinically improved sleep studies after distraction (apnea hypopnea index, 51.3 vs 5.5; P < .01). Vector analysis showed an average of 5.3° and 14.0° in groups 1 and 2, respectively (n= 10 each). Intergroup analysis showed a trend toward increased airway volume in horizontal vectors (548 vs 255% of preoperative volume; P= .058), with slightly longer distraction length (20.3 vs 16.6mm; P= .17). However, ANCOVA regression analysis showed no difference in the relation between vector and length. Other morphologic data and sleep study outcomes (apnea hypopnea index,7.0vs 3.9; P= .09) also were not statistically different between groups. Longer lengths of distraction correlated with narrower anterior mandibular angle and longer mandibular body length. Substantial airway enlargement occurs after mandibular distraction. Final airway volumes were similar between groups regardless of vector, which was confirmed by multivariate ANCOVA regression. The 2 methods achieved airway stabilization, with clinical outcomes similar between the 2 groups.

Commentary: Does Mandibular Distraction Vector Influence Airway Volumes and Outcome?

Commentary: Does Mandibular Distraction Vector Influence Airway Volumes and Outcome?

Growth hormone receptor gene variant and three-dimensional mandibular morphology.

To examine the relationship between three-dimensional mandibular morphology and growth hormone receptor (GHR) gene variants in a healthy Japanese population. The subjects, who were unrelated Japanese orthodontic patients, consisted of 64 men and 114 women. Using the Taqman genotyping assay, GHR gene rs6184 and rs6180 variants were detected in genomic DNA extracted from saliva. Mandibular volume and length were measured from cone-beam computed tomography images that were analyzed using Analyze image-processing software. The relationship between GHR gene variants and three-dimensional mandibular morphology was statistically examined. Statistical significance for the relationship between the distance between the left and right coronoid processes and rs6180 was noted (P < .05). Our results indicate that the GHR variant rs6180 is associated with the distance between the left and right coronoid process in the Japanese subjects.

Chronic fluoride exposure during gestation and lactation increases mandibular bone volume and impairs dental eruption in the rat offspring

Chronic fluoride exposure during gestation and lactation increases mandibular bone volume and impairs dental eruption in the rat offspring

A Comparison of Vascularity, Bone Mineral Density Distribution, and Histomorphometrics in an Isogenic Versus an Outbred Murine Model of Mandibular Distraction Osteogenesis

The vascularity, bone mineral density distribution, and histomorphometric data between the inbred, isogenic Lewis rat and the outbred, nonisogenic Sprague Dawley rat within mandibular distraction osteogenesis (MDO) were evaluated to allow future researchers to compare the results generated from these 2 animals. We hypothesized that little difference would be found between the 2 strains within these metrics. We implemented a comparative study between the Lewis and Sprague Dawley rat strains within MDO. The sample was composed of 17 male Lewis and 17 male Sprague Dawley rats that underwent surgical external fixation and distraction. The rats' hemimandibles were distracted to a total distance of 5.1mm. After 28days of consolidation, 9 rats from each group underwent bone mineral density distribution analysis. The remaining rats from each group were analyzed for the vascular and histologic metrics. Descriptive and bivariate statistics were computed, and the P value was set at .05. We demonstrated successful MDO in all the rats, with no significant difference found in the histologic or bone mineral density distribution metrics. No significant differences were found in any of the vascular metrics, with the exception of vascular separation, which was not normalized to the mandibular volume (P= .048). The results of the present study have demonstrated that little dissimilarity exists between the isogenic Lewis and outbred Sprague Dawley models of MDO. Thus, researchers can confidently compare the gross results between the 2 strains, with consideration of the very small differences between the 2 models. For studies that require an isogenic strain, the Lewis rat is an apt surrogate for the Sprague Dawley strain.

Evaluation of mandibular volume classified by vertical skeletal dimensions with cone-beam computed tomography.

To investigate the relationship between anteroposterior and vertical differences in maxillofacial morphology and mandibular volume. Subjects comprised 213 Japanese adults (84 males and 129 females) who were divided into three groups based on mandibular basal arch (ANB) and Wits, measured in a cephalometric analysis: Class I (-1° ≤ ANB < 4°,-1 mm ≤ Wits < 0 mm), Class II (ANB ≥ 4°, Wits ≥ 0), and Class III (ANB <-1°, Wits <-1 mm). Subjects were also divided into three groups based on the mandibular plane angle (Mp), as follows: hypodivergent (Mp < 23°), normodivergent (Mp = 23-30°), and hyperdivergent (Mp > 30°) groups. Mandibular volume was measured from cone-beam computed tomographic images that were analyzed using Analyze™ image processing software and compared among the three groups in each classification. No significant differences were noted in mandibular volume among Classes I, II, and III. An inverse relationship was found between mandibular volume and Mp, and a significant difference was noted in mandibular volume between the hypodivergent and hyperdivergent groups. In addition to two-dimensional analysis, such as lateral cephalometry, three-dimensional information such as volume, provided by cone-beam computed tomography, contributes to a more detailed assessment of maxillofacial morphology.

Craniofacial photography for prediction of obstructive sleep apnoea in a Hong Kong sleep clinic population

Introduction: Craniofacial morphology is a risk factor for obstructive sleep apnoea (OSA). Facial phenotyping by photography has been shown to be useful in identifying OSA in a Caucasian sleep clinic population. However ethnic differences in risk factors may result in a different facial profile in a Chinese population. Materials and methods: Calibrated frontal and profile facial photos were taken of patients undergoing sleep studies in a Hong Kong Sleep Centre. Facial measurements including linear distances, angles, areas and volumes were computed from surface landmarks identified on the digital images. Facial measurements were compared between those with andwithout OSA (apnoea–hypopnea index [AHI] < 10 h−1) and prediction models using logistic regression were developed to assess the utility of facial measurements for identifying OSA. Facial phenotype was compared with body mass index (BMI) as a predictor of the presence of OSA. Results: Two hundred patients were included in the study, 54 control and 146 OSA patients. The OSA group contained more males (77% vs. 61%) and were more obese (BMI 28.9 ± 4.8 kg m2 vs. 25.7 ± 3.4 kg m2, p < 0.001) than the non-OSA controls. The OSA group had larger face width (15.0 ± 0.8 vs. 14.5 ± 0.7 cm, p < 0.001) and mandibular volume but a more retropositioned maxilla and mandible (smaller maxillary and mandibular depth angles). The best logistic regression model contained three facial measurements: cervicomental angle, face width-depth angle and mandibular length, with a receiver operating characteristic (ROC) area under the curve (AUC) of 0.80 (0.74–0.87 95% CI, p < 0.001). Facial measurements performed better than BMI (AUC 0.736, 0.661–0.811 95% CI, p < 0.001) in classifying patients. Addition of BMI to the facial photo prediction model did not enhance prediction. Conclusion: Facial photographic metrics differ between those with and without OSA. In a Hong Kong sleep clinic, facial photography performed similarly in identifying OSA patients compared with previous Caucasian samples. OSA riskmay be similarly reflected in facial phenotype despite any differences in underlying skeletal and obesity risk factors.