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Purpose: The aim of this study was to investigate the biomechanical role of trabecular bone around dental implants in the mandible. Materials and Methods: The model in this study was made using micro-computed tomography data taken from a cadaver in whom endosseous implants had been in place for 15 years prior to death. Morphologic analysis and three-dimensional (3D) finite element analysis were performed to calculate the peri-implant loading path of the model in which the trabecular structure was accurately simulated. Results: As seen through multiscale analysis using the homogenization method, the trabecular bone architecture around implants was isotropic for the most part. Also, 3D finite element analysis showed that compressive stresses oblique to the implant axis were transmitted to the lower constrained surface; tensile stresses oblique to the implant axis were transmitted to the upper constrained surface, and they intersected each other with vertical loading. The highest stress in cancellous bone was observed on perpendicular loading, and stress produced in trabeculae decreased approaching horizontal loading. Conclusion: Cancellous bone architecture around the implant was generally isotropic. 3D finite element analysis showed that cancellous bone trabeculae around implants dispersed stress by forming load transfer paths. The results suggest that trabecular bone plays a major role in supporting functional pressure exerted via the implant. [ABSTRACT FROM AUTHOR]

Objective: To identify whether there is a relationship between the depth of facial wrinkles and the density of the retinacula cutis in the subcutaneous tissue of the skin. Design: Wrinkle depth was assessed with image analysis on the forehead and the lateral canthus of human cadavers. The density of the retinacula cutis was measured in Azan-Mallory-stained skin sections obtained around the wrinkles. Setting: Gross Anatomy Section, Kagoshima University Graduate School of Medical and Dental Sciences. Participants: Fifty-five male and female cadavers (35-93 years old). Main Outcome Measures: The maximum depth of each wrinkle was used to represent the wrinkle's degree. In the skin sections, the density of the retinacula cutis was measured around the deepest point of each wrinkle in a 1-mm-wide area (the wrinkle-specific area) and a 10-mm-wide area that included the wrinkle (the wrinkle-inclusive area). Results: In both the wrinkle-specific and wrinkle-inclusive areas, the retinacula cutis densities became lower in the forehead and in the lateral canthus areas. When a wrinkle was shallow, the density was lower in the wrinkle-specific area than in the wrinkle-inclusive area. With wrinkle progression, the density difference between the wrinkle-specific and the wrinkle-inclusive areas gradually decreased until there was no apparent difference. Conclusions: Facial wrinkles seem to develop above sites of reduced lower retinacula cutis density. As a wrinkle develops, the density decreases in both the wrinklespecific and the wrinkle-inclusive areas, whereas the density difference between those areas vanishes. [ABSTRACT FROM AUTHOR]

During the process of growth and development, the digastric muscle is subjected to marked functional changes, including the change from suckling to mastication. In particular, because the anterior belly of the digastric muscle, which is one of the suprahyoid muscles, plays an important role in mastication. Therefore, this muscle seems to undergo a marked functional change before and after weaning. However, the details remain unknown. Here, to clarify the changes in the muscle fibre characteristics of the anterior belly of the digastric muscle before and after weaning, we examined myosin heavy chain isoforms at the protein (immunohistochemistry) and mRNA (transcription) levels. As a control, the changes in the muscle fibre characteristics of the sternohyoid muscle, which is anatomically aligned in the same direction as the anterior belly of the digastric muscle, were analyzed. The results showed that, in the anterior belly of the digastric muscle that is involved in mandibular movements in mice, the ratio of a fast-contraction isoform with strong contractile force increased after weaning. We believe that this occurred in response to a functional change from suckling to mastication. On the other hand, there was little change in the composition of sternohyoid muscle. [ABSTRACT FROM AUTHOR]

Objective: This study aimed to control radiation doses when using a portable supine dental panoramic radiography system by measured the scattered doses., Method: The study used LPX7007 (Asahi Roentgen) for the panoramic radiography system. The subjects comprised a cylinder phantom (QualitA) and a RANDO Phantom (Alderson). The semiconductor dosimeter was an X2 survey sensor (RaySafe). The phantom was set at a height of 1 m from the floor, and the sensor was set at 1 m from the floor at the genital level and 1.5 m at the lens level. Measurements were taken at 30°intervals clockwise from 0°at distances of 0.5 m and 1 m in radius around the phantom. The occupational exposure range was defined as 0 ± 30° and the public exposure range was defined as the occupational exposure range and 30° to 150° and 210° to 330° as the public exposure range., Result: The highest doses were observed in the 120° and 240° directions, and the lowest in 0° ± 30° range. The lowest limit number of images taken in the occupational exposure range was 130 images at a distance of 0.5 m, 452 images at 1 m at the lens level for the cylinder phantom, and 320 images at 0.5 m and 1098 images at 1 m for the RANDO Phantom. In the public exposure range at the genital level, there was one image at 0.5 m and six images at 1 m for the cylinder phantom, and two images at 0.5 m and eight images at 1 m for the RANDO Phantom., Conclusion: We found that radiation exposure can be reduced by keeping a distance from the subject, avoiding working at 120° and 240° and staying within 0° ± 30° behind the panoramic radiography system., Competing Interests: Declaration of competing interest All authors declare no conflicts of interest., (Copyright © 2023 Japanese Association for Oral Biology. Published by Elsevier B.V. All rights reserved.)

Animal adaptation to environmental goals to pursue rewards is modulated by dopamine. However, the role of dopamine in the hippocampus, involved in spatial navigation, remains unclear. Here, we studied dopaminergic inputs from the ventral tegmental area (VTA) to the hippocampus, focusing on spatial goal persistence and adaptation. Mice with VTA dopaminergic lesions struggled to locate and update learned reward locations in a circular maze with dynamic reward locations, emphasizing the importance of VTA dopaminergic neurons in the persistence and adaptation of spatial memory. Further, these deficits were accompanied by motor impairments or motivational loss even when dopamine receptors in the dorsal hippocampus were selectively blocked. Stimulation of VTA dopaminergic axons within the dorsal hippocampus enhanced the mice's ability to adapt to changing reward locations. These findings provide insights into the contribution of dopaminergic inputs within the hippocampus to spatial goal adaptation., Competing Interests: The authors declare no competing interests., (© 2023 The Author(s).)

Several maze shapes are used to test spatial navigation performance and behavioral phenotypes. Traditionally, each experiment requires a unique maze shape, thus requiring several separate mazes in different configurations. The maze geometry cannot be reconfigured in a single environment to accommodate scalability and reproducibility. The reconfigurable maze is a unique approach to address the limitations, allowing quick and flexible configurations of maze pathways in a repeatable manner. It consists of interlocking pathways and includes feeders, treadmills, movable walls, and shut-off sensors. The current protocol describes how the reconfigurable maze can replicate existing mazes, including the T-shaped, plus-shaped, W-shaped, and figure-eight mazes. Initially, the T-shaped maze was constructed inside a single experimental room, followed by modifications. The rapid and scalable protocol outlined herein demonstrates the flexibility of the reconfigurable maze, achieved through the addition of components and behavioral training phases in a stepwise manner. The reconfigurable maze systematically and precisely assesses the performance of multiple aspects of spatial navigation behavior.

Fetal age is estimated widely by body length and weight and skeletal or dental development and maturation. Regarding dental development, dental development charts reported by Schour and Massler and Ubelaker are well known. We tried to calculate the calcification rate of the deciduous teeth, mandibular cortical bone, and clavicle in fetuses utilizing postmortem computed tomography (CT) image analysis. The CT values within the circumferential area of the region of interest were automatically calculated using a software, and the calcification rate was calculated by performing single regression analysis. Our results showed that deciduous tooth calcification could be detected in over 19-week-old fetuses using CT images. The calcification of bones (mandibular cortical bone and clavicle) started earlier than the calcification of deciduous teeth. However, the calcification rate of the bones was slower compared to that of the deciduous teeth. The calcification rate of the deciduous teeth in fetuses using CT value may be effective to estimate fetal age and evaluate deciduous teeth development, suggesting that our established method is effective for age estimation in forensic dentistry., (Copyright © 2021 Elsevier B.V. All rights reserved.)

This study was aimed at investigating and comparing exposure dose of workers and the surrounding workers. In addition, worker's exposure was also measure about lens and finger. Four intraoral portable X-ray units were evaluated. The stray radiations were measured using Pitman 37D and ionization chamber (Pitman). MyDosemini (ALOKA) was used for measurement of the finger exposure dose. Without the shield became high in anterior 0.5 m. Comparing the air dose for the four models used in this study showed a high tendency for the two NOMAD models. And using the shields, the images could be taken 4.6 times of the baseline at a maximum and 3.6 times on average. The finger radiation exposure dose was low with both of the NOMAD models, with no significant difference found. By setting the baseline value without a shield, finger radiation exposure when using a shield was lower than the detection limit for the D3000, and was reduced by approximately 94-96% for other three models. All models can photograph around 100 bodies, so it is considered that it is not necessary to switch out the operator considering the operation limit. But even if it does not reach the operation limit, the stochastic effects of radiation exposure can be increased as well as the deterministic effects of the operation limit. The operator and the surrounding workers seek to protect themselves. It is important to perform exposure management that takes into account the stochastic effects to the operator and the surrounding workers., (Copyright © 2020. Published by Elsevier B.V.)

Multiple mazes are routinely used to test the performance of animals because each has disadvantages inherent to its shape. However, the maze shape cannot be flexibly and rapidly reproduced in a repeatable and scalable way in a single environment. Here, to overcome the lack of flexibility, scalability, reproducibility, and repeatability, we develop a reconfigurable maze system that consists of interlocking runways and an array of accompanying parts. It allows experimenters to rapidly and flexibly configure a variety of maze structures along the grid pattern in a repeatable and scalable manner. Spatial navigational behavior and hippocampal place coding were not impaired by the interlocking mechanism. As a proof-of-principle demonstration, we demonstrate that the maze morphing induces location remapping of the spatial receptive field. The reconfigurable maze thus provides flexibility, scalability, repeatability, and reproducibility, therefore facilitating consistent investigation into the neuronal substrates for learning and memory and allowing screening for behavioral phenotypes., Competing Interests: Declaration of Interests S.T. is an inventor on Japanese unexamined patent application publication (No. P2019-115315A, applicant: Doshisha University) pertaining to the reconfigurable maze. All remaining authors declare no conflict of interest., (Copyright © 2019 The Author(s). Published by Elsevier Inc. All rights reserved.)

The purpose of this research is to obtain morphological information about the traveling route, branching pattern, and distribution within the tongue of the lingual nerve, all of which are important for oral surgical procedures. Using 20 sides from 10 Japanese cadaveric heads, we followed the lingual nerve from its merging point with the chorda tympani to its peripheral terminal in the tongue. We focused on the collateral branches in the area before reaching the tongue and the communication between the lingual and hypoglossal nerves reaching the tongue. The collateral branches of the lingual nerve were distributed in the oral mucosa between the palatoglossal arch and the mandibular molar region. Two to eight collateral branches arose from the main trunk of the nerve, and the configuration of branching was classified into three types. More distally, the lingual nerve started to communicate with the hypoglossal nerve before passing the anterior border of the hyoglossus muscle. Nerve communications were also found in the main body and near the apex of the tongue. A thorough understanding of the collateral branches near the tongue, and the communication with the hypoglossal nerve inside the tongue, will help to prevent functional disorders from local anesthesia and oral surgical procedures associated with the lingual nerve. Clin. Anat. 32:635-641, 2019. © 2019 Wiley Periodicals, Inc., (© 2019 Wiley Periodicals, Inc.)

The mechanism of formation of facial wrinkles has not been fully clarified due to the existence of many distinct influential factors. To clarify the relationship between facial wrinkles and structures in the skin, especially sebaceous glands, image analysis was performed on the forehead and lateral canthus regions of cadaveric skin specimens; 58 male and female donated cadavers (age range at death 20s - 90 s) were included in the study. Specimens were obtained from forehead and lateral canthus region after measuring wrinkle depth. Then tissue slices were prepared to observe the sebaceous gland and its density was measured and analyzed in relation to wrinkle depth, retinacula cutis density, dermal thickness, and solar elastosis degree. A correlation was found between sebaceous gland density and wrinkle depth in forehead specimens with a lower retinacula cutis density. Wrinkles were shallower in specimens with a higher sebaceous gland density. However, no such correlation was found in lateral canthus wrinkles, presumably due to the lack of sebaceous glands in that region. In addition, specimens with a higher sebaceous gland density tended to have a thicker dermis and/or less solar elastosis. Sebaceous gland density seems to be one of the multiple factors that prevent wrinkle deepening, and that is why wrinkles are deeper in the lateral canthus area than in the forehead. Functional studies will elucidate the mechanism of wrinkle formation in the future., (© 2015 Wiley Periodicals, Inc.)

Objectives: Although carotid artery structural variations have been detected by ultrasound, their clinical significance is not fully understood. The objective of this study was to determine whether the angle between the common carotid artery (CCA) and the internal carotid artery (ICA), designated angle α, an ultrasound-detectable carotid artery structural variation, is related to carotid artery intima-media thickness (IMT), a surrogate marker for carotid atherosclerosis., Methods: As a cross-sectional study, we measured angle α in routine carotid artery ultrasounds from 176 subjects (130 men) with atherosclerotic disease/risk factors that attended Kouseiren Hospital in Kagoshima City, Japan between August 2007 and April 2009. We evaluated the correlation between the angle α and CCA- or ICA-IMT., Results: Angle α was weakly correlated with age but significantly correlated with ICA-IMT. The correlation was stronger in subjects with an ICA-IMT ≥ 0.5 mm than in those with an ICA-IMT < 0.5 mm (Right side r = 0.475 vs. 0.246, Left side r = 0.498 vs. 0.301, respectively). Upon multivariate logistic regression analysis, angle α and serum low-density lipoprotein cholesterol were independent explanatory variables for ICA-IMT., Conclusion: Angle α is related to ICA-IMT in subjects with atherosclerotic disease or risk factors in this study.

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.

Objective: To identify whether there is a relationship between solar elastosis and the development of wrinkles in human skin., Design: Wrinkle depth was measured on the forehead and lateral canthus of human cadavers using image analysis. The thickness of the dermis was measured in skin sections obtained around wrinkles and stained with Elastica-van Gieson., Setting: Gross Anatomy Section, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan., Subjects: Fifty-eight male and female cadavers (age range at death, 29-93 years)., Main Outcome Measures: The ratio of solar elastosis dermal thickness to full dermal thickness (elastosis ratio) was calculated and compared between the deepest point of a wrinkle (wrinkle point) and a point within 1 mm where no wrinkle existed (nonwrinkle point). The relationship between elastosis ratios and wrinkle depths was investigated., Results: Advanced solar elastosis was present at nonwrinkle points but was present a little bit at wrinkle points. On the forehead, a positive correlation between elastosis ratios and wrinkle depths was observed at nonwrinkle points but not at wrinkle points. On the lateral canthus, a positive correlation between elastosis ratios and wrinkle depths was observed at nonwrinkle points, as well as at wrinkle points until the wrinkle became deeper than one-half of the original dermal thickness (0.6 mm). Solar elastosis on the lateral canthus ceased developing at this point, but the wrinkle developed further., Conclusions: Solar elastosis tends to commence with the development of a wrinkle until the wrinkle becomes deeper than 0.6 mm. This tendency is less evident at wrinkle points than at nonwrinkle points.

Mini-implants are increasingly being used for orthodontic anchorage in the palate. The anatomical structure of the jaw must be properly evaluated prior to use; however, there are a few research reports providing basic data regarding the palate. Bone thickness was measured and bone morphology evaluated in the palates of Japanese people. The palates of five Japanese adult cadavers and 15 skulls were examined. The samples were imaged and measured using the micro-CT system. In the mid-palatine suture region, the cortical bone had a complex mesh-like structure and was thicker than surrounding areas. Cortical bone thickness varied depending on the site. The mid-palatine suture region is an ideal site for mini-implant insertion; however, because bone and cortical bone thickness markedly decrease in the lateral region, careful attention should be paid when inserting mini-implants in the mid-palatine suture.

Given the length of axons reaching to distal regions, all peripheral nerves must derive nutrient supply not only for the nerve cell body, but also for the peripheral parts. Along the course of a peripheral nerve, in general, nutrient vessels accompany nerve fibers to peripheral regions in the form of "vasa nervorum" derived from the epineurium, reaching the endoneurium through the perineurium and forming a capillary plexus. In addition, in reconstructive procedures in plastic surgery, anastomosis of not only nerves, but also the vasa nervorum, has been reported to achieve improved outcomes. The present study therefore observed morphological features of the blood supply to the distal portion of the facial nerve in 14 sides of 14 adult cadavers (age at death, 46-86 years) under stereo microscopy after dye injection. The region of the epineurium was also observed under scanning electron microscopy (SEM). The vasa nervorum was seen to derive from a complex reticulation structure formed mainly by the superficial temporal, facial, transverse facial and zygomatico-orbital arteries with collateral supply from the supraorbital, deep temporal, buccal arteries and parotid branches. SEM showed that one capillary accompanied each perineurium in each nerve fascicle.

Objective: To identify a relationship between dermal thinning and wrinkle formation., Design: We assessed the wrinkle depth of the forehead and lateral canthus of 58 male and female human cadavers (range of age at death, 29-93 years) using image analysis and measured the dermal thicknesses in Azan-Mallory-stained skin sections obtained around the wrinkles., Setting: Gross Anatomy Section, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan., Main Outcome Measures: The maximum depth of the wrinkle was obtained from the forehead and lateral canthus. The dermal thickness was measured at the deepest point of the wrinkle (wrinkle point) and at a location where no wrinkle existed within 1 mm of its surface (nonwrinkle point). The ratio of the dermal thickness at the wrinkle point to the dermal thickness at the nonwrinkle point was calculated., Results: The dermal thickness underneath a wrinkle decreased as the depth of the wrinkle increased (P < .001). When the dermis became thinner than one-half of its original thickness, the dermis stopped thinning. Microscopic observations revealed that the junction between the dermis and subcutaneous layers under advanced wrinkles curved downward with invaginations of the dermis into the subcutaneous layer., Conclusions: The dermis under a wrinkle becomes thinner in association with the progression of wrinkles until the dermis becomes thinner than one-half of its original thickness. When the dermis stops thinning, wrinkles develop further by dermal invagination into the subcutaneous layer.

The aim of this study was to identify the load transfer paths in cortical bone and trabecular structure of cancellous bone in the jawbones for loads from endosseous implants. Maxillae were resected from beagle dogs 6 months after implant surgery and imaged using micro-computed tomography (micro-CT). A three-dimensional structure was produced based on the CT data and peri-implant trabecular structure was observed. Load transfer paths were analyzed from the results of three-dimensional finite element analysis. Furthermore, buffer actions in bone trabeculae when strain increased during stress analysis and when loads were applied were observed. Peri-implant bone trabeculae were seen extending into the upper and lower cortical bone from the fixture. The direction of bone trabecular alignment corresponded with the load transfer paths. In addition, analysis with increased strain confirmed that trabecular structures could serve as load buffers. These results suggest that bone trabeculae supporting load transfer from implants undergo remodeling.

This study reports the existence of previously unknown muscle fascicles in Japanese adult cadavers. A bundle of these muscle fascicles diverged from the pretarsal portion of the orbicularis oculi muscle and coursed in a lateral direction superficial to this muscle. When observed with the naked eye, the bundle seemed to originate at the medial canthus and run along or near the edge of the upper eyelid. However, its boundary with the orbicularis oculi muscle was indistinguishable until it crossed superficial to this muscle. Throughout our observations, the thin muscle bundle was identified with high frequency (94%, 49 of 52 individual cadavers), and is thus unlikely to be an artifact. Light microscopy revealed that, in sagittal sections, the thin muscle bundle was located on the superficial side of the lateral portion of the orbicularis oculi muscle, while in horizontal sections, it ran in a superficial plane to the orbicularis oculi muscle in a medial to lateral direction. Despite having some similarity to a muscular raphe, the lateral canthal band, and to one of the previously known inferior muscles of the orbicularis oculi muscle, the results of our anatomical study suggest that the bundle is none of these. Rather, it is a previously unreported muscle that likely contributes to the surface morphology at the lateral canthus.

The attachments of muscles onto the hyoid bone were observed macroscopically, and the lengths and widths of each muscles onto the hyoid bone were measured. The tongue-pharyngeal block as a whole obtained from 50 cadavers were used. Each muscle was colored by acrylic pigments for identification. The results showed that the mylohyoid muscles were attached onto the lower anterior surface of the hyoid bone body. The geniohyoid muscles had many types of attachment forms and significant individual differences. The hyoglossal muscles showed various attachments at the posterior end of the greater cornu. The middle pharyngeal constrictor muscles attached with two bundles in some cases. The sternohyoid muscles and omohyoid muscles were classified by their positional relationship with each other. The thyrohyoid muscles were classified by the conditions of their overlaps with the omohyoid muscles and the sternohyoid muscles. From the aforementioned results, the following muscles were found attached to the hyoid bone in a further developed state: mylohyoid muscles, geniohyoid muscles, hyoglossal muscles, thyrohyoid muscles and hyoglossal muscles.

In an effort to clarify the morphologic characteristics of the palatopharyngeal muscle, we examined its origin, insertion, and positional relationship with other muscles. We found that the origin of the palatopharyngeal muscle was both the oral and the nasal side of the soft palate; it was also attached to both the palatal aponeurosis and the soft palate median. However, in some cases the muscle originated on the nasal side was lacked. When the palatopharyngeal muscle originated from both the oral and the nasal side, it traveled through its insertion via the levator muscle of the palatine velum. This insertion was seen in a wide area and could be divided into three parts: the pharynx anterior, central, and posterior walls. In the central pharyngeal wall, insertion into the pharyngeal aponeurosis, inferior constrictor pharyngeal muscle, and esophagus were observed. The present results suggest that the palatopharyngeal muscle has a close positional relationship with the levator and tensor muscles of the palatine velum, the pharyngeal constrictor muscles, and the esophagus.

In nonhuman mammals, sinus hairs grow around the nostrils and serve for tactile sensation. The hair follicles of sinus hairs are rooted in vibrissal capsular muscles connected to the underlying, deeper orbicularis oris, thereby enabling the voluntary movement of sinus hairs. These vibrissal capsular muscles as well as the sinus hairs are believed to have been lost during human evolution, and no previous reports can be found on the existence of vestiges of sinus hairs in humans. Our study, however, has now verified the existence of vestigial muscles of vibrissae in the human upper lip. Using conventional histological techniques, microscopic observations were made on specimens obtained from the upper lips of human adult cadavers. In 35% of these individuals, several striated muscle fascicles diverging from the underlying orbicularis oris and reaching the hair follicles were observed. Histological findings of the vibrissal capsular muscle complex suggest that these fascicles are a vestigial remnant of the sinus hair muscle.

Previously, bio-mechanical studies on the temporomandibular joint have concentrated mainly on the mandibular condyle while the articular eminence has been largely overlooked. Furthermore, research on the mechanical properties of bone using finite element analysis has focused on the cortical bone in preference to cancellous bone. In this study morphorogical changes in the internal structure of the articular eminence as related to child growth were examined using Micro-CT. Morphometric analysis of samples of cancellous bone representing both deciduous and early mixed dentitions showed an increase in the bone volume fraction and trabecular thickness in the early mixed dentition, and finite element analysis indicated directional transmission of stress as well. These results suggest that the morphology of the trabecular bone was altered to adapt to the functional growth progressed from the deciduous to the early mixed dentition.

To elucidate the effects of teeth on muscle fibers in the tongue during the developmental process, we examined the expression of muscle contractile proteins and the genes for those proteins in normal mice and microphthalmic (mi/mi) mice with impaired tooth eruption. The mice were observed during the growth period, including weaning, which is when feeding movements undergo major changes. Expression of the myosin heavy chain (MyHC)-2a protein, whose contraction speed is relatively slow, disappeared after weaning in normal mice, while it remained in high concentrations even after weaning in mi/mi mice. The presence of MyHC-2a after weaning in mice with no tooth eruption was attributed to a compensation for lack of proper masticatory function and sucking-like movements, as MyHC-2a is necessary for these movements.

The mandibular angle is one of the areas of the mandible that are prone to bone fractures, and the presence of an impacted third molar has been found to be associated with increased risk of angle fractures. The factors involved in bone fractures are the amount and direction of load, and the biomechanical and anatomical properties of bone. In the present study, micro-focused X-ray computed tomography was performed to observe and analyze the three-dimensional (3D) bone microstructure of the mandibular angle, and finite element analysis was conducted to examine the relationship between angle fractures and the presence or absence of mandibular third molars. 3D bone microstructure showed no marked difference between mandibles with and without third molars. Finite element analysis showed that, in the mandible with a third molar, stress was concentrated around the root apex of the third molar, and was transmitted in a direction matching the clinical findings of angle fractures. The results obtained in this study suggest that the presence of an impacted third molar changes the concentration and transmission of stress in the mandible, thus increasing the risk of an angle fracture.

The preparation of vascular corrosion casts enables us to observe the minute features of blood vessels. For mice and rats, reports on the macroscopical appearance of testicular arteries with the cast technique have been quite limited. Therefore, in the present study, we tried to prepare corrosion casts of such arteries in order to observe the three-dimensional structures in mice and rats. Vascular casts of testicular arteries were produced by intravenous injection of a polymethylmethacrylate solution, followed by treatment of the whole animal bodies with NaOH. Additionally, the gross appearance of human testicular arteries in cadavers was compared with that of the vascular casts. The results showed that the testicular arteries of humans, mice, and rats run from the abdominal aorta to the testes, with various configurations (straight, meandering, spiral, or coiled forms), and each species exhibits a specific pattern. The specific forms of testicular arteries may play several roles in protection of normal spermatogenesis, such as allowing wide mobility of the testes on physical attack, heat emission with the entwined pampiniform plexus, and reduction of the blood flow rate. The great extension of the testicular arteries during the fetal period from the upper abdomen to the scrotum when the testes descend might be another feature of the specific development of their running configuration.

Several studies have reported that growth and differentiation of cultured myoblasts can be facilitated by applying appropriate mechanical stimulus. However, the effects of mechanical stimulus on the characteristics of muscle fibers have not yet been fully elucidated. In this study, we gave mechanical stress to C2C12 cells, which were myoblasts derived from mice skeletal muscle. The following myosin heavy chain (MHC) isoforms were investigated in order to clarify muscle characteristics: MHC-2b, 2d and 2a, all of which are fast-twitch fibers. After inoculating cells on a silicone chamber, the chamber was mechanically stretched, and a LightCycler was used to measure the mRNA expression of each MHC isoform at several times. The results showed that, with mechanical stretching, the expression of MHC-2b was initially high. On the other hand, without stretching, the expression of MHC-2d increased over time, but with stretching, it was hardly seen. Furthermore, the expression of MHC-2a was significantly high in the stretching group. These results of this study suggest that, when intermittently stimulated, myoblasts express increased levels of MHC-2a isoform. Therefore, it is indicated that myocytes respond to environmental changes not only to facilitate growth and differentiation, but also to alter muscle function actively at the MHC isoform level.

Terminal arrangements of communicating branches between the buccal nerve (V) and the facial nerve (VII) have yet to be precisely determined. To clarify distributions and relationships to facial muscles, detailed morphological examination of the two nerves was performed in the buccal region. The facial skin and underlying tissues of three cadavers were removed en bloc from the surface of the skulls and dissected from outside and inside. Arrangements of the facial muscles, nerves, and associated structures were observed. In all specimens, the communicating buccal nerve (CBN) was detected, largely covering the buccal region. The CBN gave off multidirectional twigs around the facial vein, some of which reached the anterior part of the zygomaticus major muscle. Several twigs of the CBN joined proximally with the zygomatic and buccal branches of the facial nerve. Ramified junctions that interconnected the lower zygomatic and upper buccal branches of the facial nerve were observed near sites where the CBN joined. Anterior twigs of the CBN supplied the longitudinal area lateral to the mouth, where many muscles converged. This study presents a precise morphological pattern of the CBN, suggesting functional contribution of the CBN to control of orofacial movements.

To determine in selected, staged human embryos the time period and manner of formation of the sensory nerves to the mucosa on the dorsum of the tongue, cranial nerves V(3) and IX and their lingual branches were traced microscopically. These two cranial nerves along with cranial nerve VII are present in the dorsal part of their respective pharyngeal arch 1, 2, and 3 at Stage 13. All three nerves grow ventrally at Stage 16, and the lingual branches of V(3) and IX become closer to the developing tongue region. The lingual fibers begin to enter the tongue substance at Stage 17 when they appear as large short branches that terminate 100-400 microm from the dorsal mucosal basement membrane; of the fibers that are in the tissue deep to the surface mucosa, those in the posterior tongue segment terminate the closest and those in the anterior segment the farthest. Chorda tympani nerve fibers are joined with V(3) at Stage 20. At this stage nerve fibers reach the basement membrane in the posterior tongue segment and by Stage 23 they terminate at the basement membrane throughout the tongue, being sparsest in the anterior segment. Primordial papillae appear as small mucosal projections throughout the tongue at Stage 20 and are innervated by Stage 23. The study found that innervation to the dorsum of the tongue develops during the second month of prenatal life. During the 4-week period, Stages 13-23, an innervation pattern was observed based on the relative time fibers terminate at the basement membrane. The pattern begins caudally in the root, then moves rostrally lateral to the middle tongue segment, proceeding then to the tip of the tongue. The last area to become innervated is the medial part of the middle segment or central portion of the tongue., (Copyright 2004 Wiley-Liss, Inc.)

The human brain represents an elaborate product of hominizing evolution. Likewise, its supporting vasculature may also embody evolutionary consequences. Thus, it is conceivable that the human tendency to develop cerebral vascular accidents (CVAs) might represent a disease of hominization. In a search for hominizing changes on the arterial circle of Willis (hWAC), we attempted an anatomical comparison of the hWAC with that of the mouse (mWAC) by injecting aliquots of resin into the vasculature of the mouse and then creating vascular endocasts of the mWAC. The internal carotid artery of the mouse (mICA) unites with the mWAC midway between the middle cerebral artery (mMCA) and posterior cerebral artery (mPCA). The mWAC does not complete a circle: the mWAC nourishes the anterior portion of the circle which branches out to the olfactory artery (OlfA) and mPCA, along with the mMCA, and the basilar artery (mBA) does not connect to the mPCA. The OlfA is thicker than the mMCA. The relative brain weight of the mouse was 74 g on average for a 60 kg male and 86 g for a 60 kg female, respectively, as compared with 1424 g for a 60 kg man. These findings are consistent with the mouse being a nocturnal carnivore that lives on olfactory information in contrast to the human that lives diurnally and depends on visual and auditory information. In man, the human ICA (hICA) unites with the hWAC at a point where the human middle cerebral artery (hMCA) branches out, and thus, blood from the hICA does not flow through the hWAC but drains into the hMCA directly. The hMCA is thicker than the anterior cerebral artery. The hPCA receives blood from the hBA rather than from the hICA, and thus, the entire hWAC forms a closed circuit. Since the hICA drains directly into the hMCA without flowing a distance through the hWAC, the capacitor and equalizer functions of the WAC will be mitigated so much that the resultant hemodynamic changes would render the hMCA more likely to contribute to CVAs. Thus, anatomical findings and possibly functions of the arterial circle of Willi may vary from one species to another, depending on one's specific cerebral evolution.

The chondroglossus muscle was macroscopically studied to clarify its fundamental morphology. This muscle was present in all of the 100 tongue halves examined in Japanese cadavers. In 14% of the specimens, however, the muscular fibers were sparse and vestigial. Originating mainly from the medial side of the lesser cornu of the hyoid bone, the chondroglossus muscle passed upward to penetrate the inferior longitudinal muscle of the tongue, and immediately entered the genioglossus muscle. Ascending inside the genioglossus muscle, it's bundles spread, taking a broom head or a fan-like shape. Thereafter it reached the submucosal layer in the root of the tongue, changed the direction from upward to forward, and terminated diffusely, never going past the sulcus terminalis. The origin, course, and spreading manner of the chondroglossus muscle were quite different from those of the hyoglossus muscle. The nerve fiber supplying the chondroglossus muscle was a ramus from the first lateral branch of the hypoglossal nerve. It should be considered a separate extrinsic lingual muscle independent of the hyoglossus muscle, although they have a phylogenetically close relationship.

The placement of dental implants in the molar region of the maxilla is often difficult because of the presence of the maxillary sinus. It has recently been postulated that the pillar of bone consisting of the maxillary tuberosity, the pterygoid process of the sphenoid bone, and the pyramidal process of the palatine bone, which is located at the posterior part of the maxilla, is suitable for fixing implants in the maxilla. In this study, we morphometrically examined the figure of the pillar of bone in dentate and edentulous maxillary bone specimens. The posterior part of the maxilla, including the pterygoid process of the sphenoid bone and pyramidal process of the palatine bone was embedded in polyester resin. Serial transverse sections 500 microns thick were prepared, and soft X-ray photographs were taken. Three-dimensional images of the pillar of bone were reconstructed from the contour in the soft X-ray images, and the height inclination angles, and volume of the pillar were measured. In dentulous specimens, the imaginary approximation line of the center of the gravity of the pillar of bone in the posterior part of the maxilla was inclined antero-posteriorly at an angle of 76.5 +/- 3.0 degrees from the anterior to posterior direction against the Frankfurt horizontal plane and bucco-palatally at 17.2 +/- 2.7 degrees to the medial direction against the sagittal plane. In edentulous specimens, the pillar of bone was inclined antero-posteriorly at 67.3 +/- 5.0 degrees against the Frankfurt horizontal plane and bucco-palatally at 14.1 +/- 2.1 degrees against the sagittal plane. The volume of the pillar of bone was greater in edentulous specimens than those in the dentulous specimens. The present results will enable setting up a standard for implant surgery dentulous specimens.