2019 Volume 39 Issue 3 Pages 190-197
[Introduction] Cuspid protected occlusion is an occlusal pattern classified based on the contact relationship between the upper and lower teeth during lateral movement, and it is defined as an occlusal pattern in which only the upper and lower canines contact and slide on the working side during lateral movement, separating the molars. It is considered that the horizontal component of mandibular eccentric movement harmful to the natural molars can be avoided by cuspid guidance and its mechanical effectiveness has been proposed, but fewer studies reported its scientific basis. In this study, using 3-dimensional finite element analysis, mechanical behaviors of the teeth and mandibular body induced by cuspid protected occlusion were investigated. [Materials and Methods] To analyze mechanical phenomena per tooth, a model of lateral loading on the molar region (analysis model 1) and mechanical behavior analysis model of the teeth and mandibular body with and without cuspid guidance (analysis model 2) were prepared from actual CT image data of a patient, input in finite element analysis software, MECHANICAL FAINDER version 9.0 (Center for Computational Mechanics Research, Tokyo), and analyzed. [Results] 1) Analysis model 1: Based on the displacement diagram, it was clarified that the teeth receive horizontal movement of the lower jaw. Large stress concentration on the cervix in the tooth and strong stress concentration on the root furcation in the alveolar bone region were observed during lateral movement compared with those in vertical loading. These were consistent with clinical symptoms, such as cervical abfraction and furcation involvement considered mechanical phenomena. 2) Analysis model 2: The stress level was high near the canine in the model with cuspid guidance and near the anterior tooth in the model without cuspid guidance. When the direction of the reaction force from the articular disc was compared, the mandibular head received the reaction force from the posterior side in the model without cuspid guidance compared with that in the model with cuspid guidance, showing that it was going to move backward.
