We investigated three-dimensional decrease in the volume of the pulp chamber caused by age-related secondary dentin formation using micro-CT and evaluated the applicability of the results to evaluation of age taking into account sex, age and tooth type. Decrease was slightly higher in females than in males, and a higher correlation between decrease and aging was observed in females. A comparison between age-groups revealed that decrease progressed between the fifties and sixties in males, and the forties and fifties in females. A stronger correlation between aging and decrease was observed in the mandibular central incisors than in the mandibular second premolars. This correlation was higher than other correlations between sexes and age-groups.

The lateral pterygoid muscle has unique anatomical, physiological and functional properties. Since it is attached to the temporomandibular joint (TMJ) disc, its pathologies are closely related to TMJ disorders, which affect many people worldwide. Muscle structures and units are characterized by their morphological appearance, nerve distribution and function. In the present study, we examined the intramuscular innervation pattern of the lateral pterygoid muscle using modified sihler's method. Two types of innervation pattern were evident. In type I, representing the majority of the samples, a total of three branches arising from the main trunk of the mandibular nerve and the buccal nerve innervated the inferior head of the muscle, while branches from the buccal nerve innervated the superior head. In type II, divisions of the lateral pterygoid nerve branched from the buccal nerve located between the heads of the lateral pterygoid muscle and innervated each head separately. Interestingly, muscle bundles with a stronger tendineous structure showed much more innervation than other parts of the muscle. Future studies including quantitative analysis of the nerve distribution to the muscle bundles are warranted.

The aim of this study was to clarify the influence of shear modulus on the analytical accuracy in peri-implant jaw bone simulation. A 3D finite element (FE) model was prepared based on micro-CT data obtained from images of a jawbone containing implants. A precise model that closely reproduced the trabecular architecture, and equivalent models that gave shear modulus values taking the trabecular architecture into account, were prepared. Displacement norms during loading were calculated, and the displacement error was evaluated. The model that gave shear modulus values taking the trabecular architecture into account showed an analytical error of around 10-20% in the cancellous bone region, while in the model that used incorrect shear modulus, the analytical error exceeded 40% in certain regions. The shear modulus should be evaluated precisely in addition to the Young modulus when considering the mechanics of peri-implant trabecular bone structure.