Relationship between interincisal angles and TMJ morphology/position and trabecular structure: a retrospective study.

BACKGROUND: TMJ morphology/position and trabecular structure are influenced by various factors. The role of the interincisal angle, an indicator of the anterior occlusal relationship, on TMJ remains unclear. This study aims to investigate the morphology, trabecular bone structure, and position of the condyle, as well as the glenoid fossa's morphology in skeletal class II populations with different interincisal angles. MATERIALS AND METHODS: A total of 150 adult patients with normodivergent facial types and skeletal class II malocclusions were selected and divided into three groups based on their interincisal angles: normal, small, and large angle groups. The indexes of TMJ were measured using cone-beam computed tomography (CBCT) data and analyzed using Dolphin Imaging, Mimics, and ImageJ. RESULTS: The small angle group had the smallest anteroposterior diameter (APD), while the large angle group had a greater mediolateral diameter (MLD). The large angle group exhibited significantly the largest maximum axial area, bone surface area, and bone volume (P < 0.05). Small and large angle groups exhibited greater bone trabeculae (Tb. N) and thinner trabecular thickness (Tb. Th). Compared to the normal angle group, the small angle group exhibited a larger horizontal condylar angle and smaller bilateral condylar angles on the axial plane, while the large angle group showed the opposite trend. Small and large angle groups showed a reduced vertical condyle angle on the coronal plane, with the largest reduction observed in the large angle group (P < 0.05). Small and large angle groups had higher heights of the glenoid fossa (GFH). The large angle group exhibited the greatest GFH and width of the glenoid fossa (GFW) (P < 0.05). CONCLUSION: The large angle group had elongated oval and large condyles, and deeper glenoid fossae, while a flattened-oval and smaller condyle, and wider and shallower glenoid fossae were observed in the small angle group. Small and large interincisal angle affects the structure of condylar trabeculae, resulting in thinner Tb. Th and greater Th. N. In the condylar position, small and large angle groups exhibit condylar rotation in the axial and coronal planes. Therefore, the interincisal angle affects the morphology, position, and trabecular structure of the TMJ. This implies that we must pay attention to the impact of the interincisal angle on TMJ, and it is crucial to restore the normal interincisal angle during orthodontic treatment.

The prevalence of equine odontoclastic tooth resorption and hypercementosis and the role of interincisal angulation in disease severity in a representative cohort of horses in Switzerland.

INTRODUCTION: Equine odontoclastic tooth resorption and hypercementosis (EOTRH) is an increasingly diagnosed degenerative dental disease in aged horses. The primary aim of this retrospective study was to determine the prevalence of EOTRH in horses admitted to the Equine Hospital, University of Zurich, for dental procedures from 2004 to 2017. A secondary goal was to measure and compare interincisal angles on two-dimensional radiographs of horses with EOTRH to determine whether the interincisal angle is associated with age and severity of the disease. Radiographs were assessed for the presence of lysis and/or hypercementosis, and the number and position of the teeth affected were determined. Each tooth was also evaluated using the modified classification system introduced by Rehrl et al. (2018), in which stage 0 indicates no radiographic abnormalities and stage 3 denotes severe abnormalities. The overall stage was defined by the tooth with the most severe lesions. The interincisal angle was determined in horses that had suitable radiographs. The medical records of 838 horses admitted for dental procedures were evaluated, and 85 (10,1 %) had clinical evidence of EOTRH. The mean interincisal angle was 136,06 ° in horses with mild to moderate EOTRH and 135,10 ° (SD = 11,90 °) in severely affected patients. In conclusion, the angle measurements on lateral radiographs were highly reproducible. However, the interincisal angle was not associated with age or the severity of EOTRH. The interincisal angle and the disease pattern were not correlated.

INTRODUCTION: La résorption et l'hypercémentose odontoclastique des dents chez le cheval (EOTRH) est une maladie dentaire dégénérative de plus en plus diagnostiquée chez les animaux âgés. L'objectif principal de cette étude rétrospective était de déterminer la prévalence de l'EOTRH chez les chevaux admis à l'Hôpital équin de l'Université de Zurich pour des interventions dentaires entre 2014 et 2017. Un objectif secondaire était de mesurer et de comparer les angles inter-incisifs sur des radiographies bidimensionnelles de chevaux atteints d'EOTRH afin de déterminer si cet angle est associé à l'âge et à la gravité de la maladie. Les radiographies ont été évaluées pour la présence de lyse et/ou d'hypercémentose, et le nombre et la position des dents affectées ont été déterminés. Chaque dent a également été évaluée à l'aide du système de classification modifié introduit par Rehrl et al. (2018), dans lequel le stade 0 indique l'absence d'anomalies radiographiques et le stade 3 indique des anomalies graves. Le stade global a été défini par la dent présentant les lésions les plus sévères. L'angle inter-incisif a été déterminé chez les chevaux qui avaient des radiographies appropriées. Les dossiers médicaux de 838 chevaux admis pour des interventions dentaires ont été évalués et 85 (10,1 %) présentaient des signes cliniques d'EOTRH. L'angle inter-incisif moyen était de 136,06° chez les chevaux présentant une EOTRH légère à modérée et de 135,10° (écart-type = 11,90°) chez les patients gravement atteints. En conclusion, les mesures d'angle sur les radiographies latérales étaient très reproductibles. Cependant, l'angle inter-incisif n'était pas associé à l'âge ou à la sévérité de l'EOTRH. L'angle inter-incisif et le profil de la maladie n'étaient pas corrélés.