Perspective on Temporomandibular Joint Disorder: Foramen Tympanicum Defect.

BACKGROUND: Foramen tympanicum (FT) is a defect located anterior-inferior to the external acoustic meatus. We evaluated its prevalence, location, size, and relationship with temporomandibular joint (TMJ) disorders. METHODS: Cone beam computed tomography was performed for 200 patients who presented to the Karamanoglu Mehmetbey University Ahmet Kelesoglu Faculty of Dentistry Hospital. The location and size of the FT in the axial and sagittal planes were evaluated. Descriptive statistics were used to compare the study parameters among age and sex groups. Patients with FT were reevaluated by two maxillofacial surgeons at the study centre. RESULTS: In total, 200 images from 400 joints were examined. Unilateral and bilateral FT (19 [9.5%] and 8 [4%], respectively) was detected in 35 (17.5%) images from 27 (13.5%) patients. Examinations were performed for TMJ disorders in 24 patients. Participants with bilateral defects had the highest rates of presence of sounds and ear pain on the left and right sides (p < .05). CONCLUSION: Foramen tympanicum can lead to TMJ disorders and spread of tumours or infections from the external auditory canal to the infratemporal fossa. The increased prevalence of such disorders in patients with bilateral FT suggests an association between them.

Line of Sight in Hominoids.

OBJECTIVES: It remains unclear how the realignments of the face and basicranium that characterize humans were acquired, both phylogenetically and ontogenetically. The developmentally constrained nature of the skull has been previously demonstrated in other primates using Donald H. Enlow's mammalian craniofacial architectural relationships. Here, we compare crania of our closest relatives to gain greater understanding of how and why the relationship of the face and cranial base is developmentally constrained in order to inform instances of abnormal growth and clinical intervention. STUDY DESIGN: A method for evaluating these fundamental architectural relationships using 3D landmark data was developed, thereby taking overall size and the geometric relationships among points into account. A sample of cone-beam computed tomography scans derived from humans and extant apes were analyzed (n=10 and n=6, respectively), as well as fossil hominid crania (n=7). Landmarks for 23 craniofacial architectural points were identified and recorded. RESULTS AND CONCLUSIONS: Principal components analyses reveal that despite the similarities in craniofacial architecture between humans, extant apes and fossil hominids, appreciable trends in variation between the extant species suggest that the repositioning of the foramen magnum was only one of a constellation of traits that realigned the basicranium and face during the transition to bipedalism.

Magnetic resonance imaging of temporomandibular joint: morphometric study of asymptomatic volunteers.

BACKGROUND: The aims of this study were to determine the best suited magnetic resonance imaging scanning plane, scanning sequence, and imaging modality for the evaluation of the temporomandibular joint (TMJ) and quantitatively assess the relationship of articular disk position to condyle position. METHODS: One hundred four TMJs in 52 symptom-free heads were examined by magnetic resonance imaging. The best scanning plane, scanning sequence, and scanning parameter were determined according to the imaging time and image quality. Bilateral symmetry of the articular disk and mandibular condyle was measured by using the automatic measurement of 3.0-T GE Excite Signa MR scanner. RESULTS: Fast spin-echo sequence, oblique sagittal imaging plane, and proton density imaging were the best suited scanning sequence, scanning planes, and imaging modality, respectively. The thicknesses of the anterior and posterior bands and for the intermediate zone were not statistically different for both sides. The posterior band of the disk was found to originate in an area adjacent to the 12-o'clock position of the condyle (± 5 degrees), whereas the anterior band of the disk originated adjacent to 1-o'clock position (28 ± 6 degrees). The anteroposterior diameter and mediolateral diameter of the condylar processes were not statistically different for both sides. The axial condylar angle between the plane of the greatest mediolateral diameter of the condylar processes and the midsagittal plane were also not statistically different for both sides. CONCLUSIONS: The magnetic resonance images can depict clearly major regional anatomic structures and position in the TMJ, which can be used in the early diagnosis for the TMJ disorder.

[Sagittal photogrammetric evaluation of the soft tissue profile between two different racial groups: a comparative study]. / Caractéristiques photogrammétriques sagittales de profil des tissus mous chez deux groupes raciaux. Etude comparative.

INTRODUCTION: Facial soft-tissue analyses made from photographic records (photogrammetric analysis of the soft tissues) showed interracial dimorphism. Standard of these facial analyses, originally obtained from Caucasian might not be appropriate for the diagnosis and treatment planning of other groups of orthodontic patients. The purpose of this study was to compare the sagittal photogrammetric soft tissue profile characteristics between Senegalese and Moroccan adults. MATERIALS AND METHODS: A cross-sectional study was performed in a group of Senegalese and Moroccan students in the Faculty of Medicine, Pharmacy and Dentistry of Dakar. Standardized facial-profile photographs were taken with each student in natural head position, centric relation, and relaxed lip posture. Twenty four linear parameters were measured on paper sheet using a graduated ruler. For each variable mean and SD were calculated. In addition independent samples t-test was performed to detect sexual and racial dimorphism. Results were regarded as significant at p = 0.05. RESULTS: Senegalese subjects had significantly more lips protrusion than Moroccan who had significantly a more elongated and more anterior positioned nose, a more chin prominence and a tendency to cutaneous class II than Senegalese. CONCLUSION: Further studies including different age groups subjects would allow having longitudinal data according to age.

A finite element model to predict the sound attenuation of earplugs in an acoustical test fixture.

Acoustical test fixtures (ATFs) are currently used to measure the attenuation of the earplugs. Several authors pointed out that the presence of an artificial skin layer inside the cylindrical ear canal of the ATFs strongly influenced the attenuation measurements. In this paper, this role is investigated via a 2D axisymmetric finite element model of a silicon earplug coupled to an artificial skin. The model is solved using COMSOL Multiphysics (COMSOL(®), Sweden) and validated experimentally. The model is exploited thereafter to better understand the role of each part of the earplug/ear canal system and how the energy circulates within the domains. This is investigated by calculating power balances and by representing the mechanical and acoustical fluxes in the system. The important dissipative role of the artificial skin is underlined and its contribution as a sound transmission pathway is quantified. In addition, the influence of both the earplug and the artificial skin parameters is assessed via sensitivities analyses performed on the model.

Is it possible to use cross-sectional and vertical facial measurements to establish the shape of the mandibular arch?

BACKGROUND: Given the benefits of radiographic cephalometric studies in determining patterns of dental-skeletal-facial normality in orthodontics, the aim of this study was to investigate the association between mandibular dental arch shape and cross-sectional and vertical facial measurements. MATERIALS AND METHODS: It was analyzed plaster casts and teleradiographs in frontal and lateral norm belonging to 50 individuals, aged between 15 and 19 years, with no previous history of orthodontic treatment and falling into four of the six Andrews's occlusion keys. The plaster models were scanned (3D) and the images of the dental arches were classified subjectively as oval, triangular and quadrangular by three calibrated examiners, with moderate inter-examiner agreement (Kappa = 0.50). After evaluation of the method error by paired t test (p > 0.05), it was carried out the analysis of cross-sectional and vertical facial measurements to be compared to the shape of the dental arch. Data were subjected to one-way analysis of variance with a significance level of 5%. RESULTS: When the VERT index was compared with the three arch shapes, no measurement showed statistically significant differences (p > 0.05): triangular (0.54); oval (0.43); and quadrangular (0.73); as well as there were no differences (p > 0.05) in the widths of the face (141.20; 141.26; 143.27); maxilla (77.27; 77.57; 78.59) and mandible (105.13; 103.96; 104.28). CONCLUSION: It can be concluded that there was no correlation between different shapes of the mandibular dental arch and the cross-sectional and vertical facial measurements investigated.

Classification, registration and segmentation of ear canal impressions using convolutional neural networks.

Today, fitting bespoke hearing aids involves injecting silicone into patients' ears to produce ear canal molds. These are subsequently 3D scanned to create digital ear canal impressions. However, before digital impressions can be used they require a substantial amount of effort in manual 3D editing. In this article, we present computational methods to pre-process ear canal impressions. The aim is to create automation tools to assist the hearing aid design, manufacturing and fitting processes as well as normalizing anatomical data to assist the study of the outer ear canal's morphology. The methods include classifying the handedness of the impression into left and right ear types, orienting the geometries onto the same coordinate system sense, and removing extraneous artifacts introduced by the silicone mold. We investigate the use of convolutional neural networks for performing these semantic tasks and evaluate their accuracy using a dataset of 3000 ear canal impressions. The neural networks proved highly effective at performing these tasks with 95.8% adjusted accuracy in classification, 92.3% within 20° angular error in registration and 93.4% intersection over union in segmentation.

Axisymmetric versus three-dimensional finite element models for predicting the attenuation of earplugs in rigid walled ear canals.

The axisymmetric hypothesis of the earplug-ear canal system geometry is commonly used. The validity of this hypothesis is investigated numerically in the case of a simplified configuration where the system is embedded in a rigid baffle and for fixed boundary conditions on the earplug lateral walls. This investigation is discussed for both individual and averaged insertion loss predictions of molded silicon earplugs. The insertion losses of 15 earplug-ear canal systems with realistic geometries are calculated using three-dimensional (3D) finite element models and compared with the insertion losses provided by two-dimensional equivalent axisymmetric finite element models using 6 different geometry reconstruction methods [all the models are solved using COMSOL Multiphysics (COMSOL, Sweden)]. These methods are then compared in order to find the most reliable ones in terms of insertion loss predictions in this simplified configuration. Two methods have emerged: The usage of a variable cross section (with the same area values as the 3D case) or the usage of a constant cross section (with the same length and volume as the 3D case).

A reference line on temporomandibular joint MRI.

PURPOSE: The aim of this study was to establish a reference line and the 12 o'clock position on sagittal MRI images of the temporomandibular joint (TMJ) for close observation of early changes in disk position. MATERIALS AND METHODS: The study included 106 joints of 53 consecutive male and female patients (mean age 13.3 years) with available MRI and limited cone-beam computed tomography (LCBCT) images, from a pool of postorthodontic patients who had finished phase I or phase II orthodontic treatment between March 2006 and March 2008 in a private orthodontic office. High-resolution (0.1 pixel) LCBCT images taken in natural head position in the same time period and adjusted to the same magnification were superimposed on corresponding MRI images. The true horizontal line (THL) determined by natural head position on the LCBCT image was transferred to the MRI image. A clinically easy-to-use reference line (RL) approximating THL was drawn by connecting two readily locatable anatomical landmarks, the most inferior point of the articular eminence and the center of the auditory canal, and correspondence between THL and RL was assessed. RESULTS: The mean angle formed by THL and RL on the MRI images of the TMJs studied was 2.2° (SD 2.8°) clockwise around the center of the auditory canal, and the angulations of THL and RL on MRI images of the TMJs studied demonstrated a high positive correlation (r = 0.84). CONCLUSIONS: THL can be established directly on MRI images using the THL-RL angle obtained by this study in patients without advanced disk displacement resulting in bony changes of the joint. The deepest point on the glenoid fossa that meets the THL can be used as the 12 o'clock position for evaluation of incipient disk position change.

A cephalometric study to determine the center of anteroposterior curve of occlusion in the cranium.

Proper management of the occlusal plane is an essential consideration when multiple long span posterior restorations are designed. When restorations are added to an existing tooth arrangement characterized by rotated, tipped or extruded teeth, excursive interferences may be incorporated. The curve of Spee which exists in natural dentition, allows harmony to exist between the anterior teeth and the condylar guidance. Broadrick fag or occlusal plane analyzer is used to assist in the reproduction of tooth morphology that is commensurate with the curve of Spee when posterior restorations are designed; its use prevents the introduction of protrusive interferences. The current study determines the relationship of the center of anteroposterior curve of occlusion in the cranium and its relationship to other cephalometric landmarks and also evaluates the relationship of anteroposterior curve of occlusion to the condyle.

Determining the sagittal relationship between the maxilla and the mandible: a cephalometric analysis to clear up the confusion.

UNLABELLED: Establishing the sagittal jaw relationship is a key component to developing a diagnosis when treating an orthodontic patient. Several measurements, including the Wits Appraisal, ANB angle and nasion perpendicular have been and are currently used by practitioners to diagnose the sagittal jaw relationship. Unfortunately, all of these measurements have their limitations. The Cannon Analysis was created in an attempt to help overcome these limitations. METHODS: One hundred untreated patients from the Vanderbilt University Medical Center database were selected, and their initial lateral cephalometric radiographs were digitally traced utilizing the Cannon Cephalometric Analysis. All of these patients had an orthognathic profile, a Class I occlusion and a good skeletal balance as judged by the authors. Normative values were established for the Cannon Analysis and then broken down by sex and age (8-11, 12-18, 19 and over). An example case was analyzed using the Cannon Analysis and several diagnostic scenarios were reviewed. RESULTS: The variance or difference between Porion to A Point (Po-A) and Porion to B Point (Po-B) was found to be 12.6 mm. This value remained relatively constant throughout life, with only slightly higher values for males versus females. CONCLUSION: The Cannon Analysis is an effective way to accurately establish the sagittal jaw relationship since it is not affected by the anterior / posterior position of nasion, the steepness of the mandibular plane angle, nor an improperly drawn occlusal plane.

Determination of vertical dimension of occlusion in dentate patients by cephalometric analysis--pilot study.

OBJECTIVES: The concept of vertical dimension of occlusion (VDO) refers to a measure in the vertical plane that establishes the relation between the maxilla and the mandible when the posterior teeth, both from the maxillary and from the mandibular arches, are occluded, regardless of whether they are natural or prosthetic, healthy or restored. This measure is subject to change, and when this occurs, it can compromise both the function and the facial aesthetics. This study proposed to develop a methodology based on cephalometric analysis by studying the 31 lateral teleradiographs of adult, dentate individuals to determine the VDO, based on bone structures that are not dependent on the presence or absence of posterior teeth. The final goal was to make this application accessible to individuals who have undergone alterations of the lower portion of the face. MATERIALS AND METHODS: The cephalometric analysis of this study, called Seraidarian-Tavano, was verified through facial angles (upper and middle angles) that, when correlated, determine the lower position of the face. RESULTS: The analysis of results showed that no statistically significant difference between the angles studied could be observed (superior angle 50.29 ± 3.35 e median angle 49.95 ± 3.37). In the same manner, no variation in the results regarding gender in the measure of these angles could be observed. CONCLUSION: This cephalometric analysis can be applied to determine the VDO, regardless of the presence or absence of posterior teeth.

Intraexaminer and interexaminer reliabilities of landmark identification on digitized lateral cephalograms and formatted 3-dimensional cone-beam computerized tomography images.

INTRODUCTION: The purposes of this study were to determine and compare the intraexaminer and interexaminer reliabilities of commonly used cephalometric landmarks identified on digitized lateral cephalograms and formatted cone-beam computerized tomography (CBCT) images. METHODS: CBCT images from 10 randomly selected adolescent patients were obtained from the orthodontic records of a private practice. Measurement errors, and intraexaminer, and interexaminer reliability correlation coefficients (ICC) were obtained for all landmark coordinates. RESULTS: Intraexaminer and interexaminer reliabilities for all coordinates for most landmarks on the digital lateral cephalograms and CBCT images were greater than 0.9 (ICC value). The means of landmark locations differed by approximately 1 mm in most coordinates from the lateral cephalograms and were predominantly higher than 1 mm for all coordinates from the CBCT images. CONCLUSIONS: Intraexaminer and interexaminer reliabilities were high for most landmarks. Coordinates with greater measurement errors in the lateral cephalograms (condylion, gonion, porion, mandibular incisor apex, and posterior nasal spine) were in structures without clearly defined borders. In the CBCT images, gonion, condylion, and porion were located on surfaces that were flat or curved, making it difficult to recognize a specific reference point. Other less reliable landmarks (anterior nasal spine, posterior nasal spine, mandibular incisor apex) were located in structures with lower densities and could not be visualized with 3-dimensional reconstruction; thus, they had high measurement errors.

Soft tissue morphology of Jordanian adolescents.

OBJECTIVE: To determine soft tissue cephalometric norms of a sample of Jordanian adolescents and to compare them with those of North Americans. MATERIALS AND METHODS: Forty-one subjects aged 14 to 17 years were selected from a larger random and representative sample of 320 adolescents attending 12 schools in the capital of Jordan, Amman. Seven reference lines were identified and traced according to definitions by Holdaway and Ricketts, and 2 angular and 12 linear measurements were analyzed. RESULTS: Significant differences were found between males and females in measurements of soft tissue facial angle, H angle, subnasale to H line, basic upper lip thickness, upper lip thickness and labrale inferius and superius to E line (P < .05). Males had a more prominent upper lip in relation to the overall soft tissue profile, while the lips of females were considerably more retrusive in relation to the nose and chin. Jordanian norms were similar to those of North Americans, with only two exceptions: the H angle and skeletal convexity which were 5.4 degrees and 3.2 mm greater in Jordanians, respectively. CONCLUSIONS: Jordanian soft tissue norms were similar to American norms with the exception of the former having a more prominent upper lip position in relation to the overall soft tissue profile.

Comparison of dentoalveolar protrusion values in Moroccans and other populations.

SUMMARY: The aim of this retrospective study was to evaluate bimaxillary protrusion among Moroccans and to compare the Moroccan population with other Arabic, Caucasian, and Mediterranean populations. Cephalometric radiographs of 102 Moroccan adult university students (73 females and 29 males, mean age: 21 years 6 months +/- 1 year 6 months) with a normal occlusion were traced. Fifteen measurements concerning the upper and lower incisors, upper and lower lips, and the Frankfort to mandibular plane angle were assessed. Statistical analysis of the data was undertaken using independent t-tests. Eight angular and six linear measurements were statistically significantly different compared with Caucasian cephalometric norms (P < 0.001). Significant differences were observed compared with other adult Arabic populations (Palestinians and Saudis) and with Turkish Anatolian adults. Relative to Caucasian cephalometric norms, Moroccans showed bimaxillary protrusion and, therefore, these norms cannot be applied to Moroccan faces. In general, there was a great similarity in incisor position between the Moroccan and Saudi populations.

Accuracy and reliability of linear cephalometric measurements from cone-beam computed tomography scans of a dry human skull.

INTRODUCTION: The purpose of this study was to determine the accuracy and reliability of 3-dimensional craniofacial measurements obtained from cone-beam computed tomography (CBCT) scans of a dry human skull. METHODS: Seventeen landmarks were identified on the skull. CBCT scans were then obtained, with 2 skull orientations during scanning. Twenty-nine interlandmark linear measurements were made directly on the skull and compared with the same measurements made on the CBCT scans. All measurements were made by 2 operators on 4 separate occasions. RESULTS: The method errors were 0.19, 0.21, and 0.19 mm in the x-, y- and z-axes, respectively. Repeated measures analysis of variance (ANOVA) showed no significant intraoperator or interoperator differences. The mean measurement error was -0.01 mm (SD, 0.129 mm). Five measurement errors were found to be statistically significantly different; however, all measurement errors were below the known voxel size and clinically insignificant. No differences were found in the measurements from the 2 CBCT scan orientations of the skull. CONCLUSIONS: CBCT allows for clinically accurate and reliable 3-dimensional linear measurements of the craniofacial complex. Moreover, skull orientation during CBCT scanning does not affect the accuracy or the reliability of these measurements.

A 3-dimensional method for analyzing facial soft-tissue morphology of patients with jaw deformities.

INTRODUCTION: Traditional cephalometric radiographs can analyze facial soft-tissues 2 dimensionally. Because they cannot provide information about the nose, lips, cheeks, and mouth, another method is needed to analyze these soft tissues. We introduce a new method for analyzing the 3-dimensional (3D) shape and size of facial soft-tissue morphology. METHODS: A 3D average face model was constructed based on 3D computed tomography images of Japanese male and female adult volunteers who had well-balanced faces and normal occlusions. To test the feasibility of evaluating the quantitative effects of surgery, preoperative and postoperative 3D computed tomography images of facial soft tissues of 1 man and 1 woman were superimposed on the average faces. RESULTS: This quantitative assessment provided a comprehensive evaluation of the characteristics that separate size and shape. It was possible to view the superimposed images from any desired angle on a personal computer. CONCLUSIONS: This method provides easy-to-understand information for patients and appears to be useful for clinical diagnosis and pretreatment and posttreatment soft-tissue morphologic evaluations of patients with jaw deformities.

Electromyographic activity of masseter and temporal muscles with different facial types.

OBJECTIVES: To compare the electromyographic (EMG) activity of the masseter and anterior portion of temporal muscles in different vertical facial types. MATERIALS AND METHODS: Clinical examination, cephalometric analysis, and electromyographic examination were performed in 44 volunteers ranging from 18 to 35 years old. The volunteers were classified on the basis of their vertical facial characteristics into three groups-brachyfacial, mesofacial, and dolicofacial-by the grouping analysis. The EMG records were obtained with three repetitions during mandibular rest, maximum voluntary contraction in intercuspidation, and simultaneous bilateral isotonic contraction. The Kolmogorov-Smirnov and Levene tests were applied to verify the normality and homogeneity of variance. Analysis of variance and the Kruskal-Wallis test identified statistical differences among groups that did not present normality and homogeneity of distribution, respectively. Significance for all statistical tests was set at P < .05. RESULTS: At rest, only the right temporal and masseter muscles presented statistically significant differences among the groups. The differences were observed between groups 1 and 2 (P = .02) and 1 and 3 (P = .038) for the right temporal muscle, and between groups 1 and 2 (P = .029) for the right masseter muscle. Generally, group 1 presented the lowest EMG values for the four muscles evaluated during rest. For isotonic evaluation, none of the groups of muscles presented statistically significant differences. CONCLUSION: Different vertical facial types do not determine distinct patterns of EMG activity for the masseter and anterior portion of temporal muscles during rest and bilateral mastication.

Developing an automatic lateral cephalometric landmark identification program and evaluating its performance.

PURPOSE: To evaluate the accuracy of detecting cephalometric landmarks automatically by computer. MATERIALS AND METHODS: Digital image processing algorithms (edge-based and morphological) in addition to mathematical algorithms (knowledge-based) were used to develop a program for the identification of 15 lateral cephalometric landmarks on digital cephalograms. RESULTS: The automatic landmark identification system was clinically acceptable (p > 0.05 comparing with 2-mm error range) for five landmarks. CONCLUSION: The automatic landmark identification is accurate for only some landmarks. Additional studies may be necessary to improve this method.

A Novel Noninvasive Patient-Specific Navigation Method for Orbital Reconstructive Surgery: A Phantom Study Using Patient Data.

BACKGROUND: The correction of orbital deformities is an ongoing challenge in maxillofacial surgery. Computer-assisted navigation can improve surgical outcomes. However, conventional registration methods for navigation are not appropriate for orbital reconstructive surgery. This study proposes an accurate, noninvasive, patient-specific navigation method and demonstrates its feasibility. METHODS: A noninvasive, patient-specific registration frame based on the external auditory canals and upper front teeth was designed using software developed in-house. A three-dimensional craniofacial model was segmented from patient computed tomographic data for the registration frame. A customized craniofacial phantom was also made using this three-dimensional model, with 20 embedded target points on the orbital model and 21 landmark points on the reference standard model. The proposed method was compared with two conventional registration methods: the dental splint-based method and the invasive marker frame-based method. Twenty trials were conducted for evaluation. Target registration error and surface registration error were computed to measure accuracy. RESULTS: The proposed method showed a target registration error of 1.05 ± 0.52 mm, with greater accuracy than conventional methods (dental splint, 2.10 ± 0.63 mm; invasive marker frame, 1.22 ± 0.46 mm). The proposed method yielded the best results for surface registration error, with 0.38 mm of deviation (dental splint, 0.82 mm; invasive marker frame, 0.60 mm). CONCLUSION: The proposed noninvasive patient-specific registration method demonstrated superior results for both target registration error and surface registration error compared with other conventional registration methods for computer-assisted navigation in orbital reconstructive surgery. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, V.