Shintaro Kondo

Comparison between cone-beam and multislice computed tomography depicting mandibular neurovascular canal structures.

OBJECTIVE The most common diagnostic imaging modalities for cross-sectional imaging in dental implant planning are currently cone-beam computed tomography (CBCT) and multislice CT (MSCT). However, clinical differences between CBCT and MSCT in this task have not been fully clarified. In this investigation, the detection of fine anatomical structures in the mandible was assessed and compared between CBCT and MSCT images. STUDY DESIGN The sample consisted of 28 patients who had undergone CBCT and MSCT. The bifid mandibular canal in the mandibular ramus, accessory mental and buccal foramina, and median and lateral lingual bony canals were observed in 2-D images, and the findings were compared between CBCT and MSCT. RESULTS Four of 19 canals observed in CBCT were not observed in MSCT images. Three accessory mental foramina in 2 patients and 28 lateral lingual bony canals in 18 patients were observed consistently using the two methods. CONCLUSION Depiction of fine anatomic features in the mandible associated with neurovascular structures is consistent between CBCT and MSCT images.

Assessment of Maxillary Sinus Septa Using Cone-Beam Computed Tomography: Etiological Consideration

BACKGROUND Septum presence in the maxillary sinus complicates sinus floor elevation surgery, and so it is important that septa are accurately diagnosed on preoperative imaging. PURPOSE Septa were observed regarding their relationship with the bony palate using cone-beam computed tomography (CT). MATERIALS AND METHODS Thirty maxillary sinuses with dentate jaws of 15 dry skulls and a cone-beam CT unit were used. A septum was defined as a pointed bone structure, and an exostosis was defined as a rounded bone structure. The occurrence and locations of maxillary sinus septa and exostoses of more than 2 mm in height were evaluated. Also, angles between the direction of septum and median palatine suture were measured on axial images. RESULTS Twelve septa of 11 maxillary sinuses (37%) and nine exostoses of nine maxillary sinuses (30%) were observed. Also, 42% of septa and 67% of exostoses were antero-posteriorly aligned according to the transverse palatine suture. Moreover, the mean septum angle was 57.9 degrees in the anterior maxillary sinus region, and 101.8 degrees in the transverse palatine suture region, and significant differences were noted between them. CONCLUSION Maxillary sinus septa and exostoses could be clarified regarding their relationship with the bony palate using cone-beam CT.

Retinal Projections in the House Musk Shrew, Suncus murinus, as Determined by Anterograde Transport of WGA-HRP

Retinal projections in the house musk shrew (Suncus murinus) were determined by the anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). Unilateral injection of WGA-HRP into the vitreous body resulted in the terminal labeling of the optic projections in the suprachiasmatic nucleus (SCH), the ventral (CGLv) and dorsal (CGLd) lateral geniculate nuclei, the intergeniculate leaflet (IGL), the pretectum, the superficial layers of the superior colliculus (CS), and the dorsal terminal nucleus (DTN) of the accessory optic system (AOS). Labeling of the SCH was bilateral, with ipsilateral predominance, and covered the whole dorsoventral extent of the nucleus. Immunohistochemical studies revealed that VIP-like immunoreactive neurons and fibers were present in almost all parts of the SCH. No hypothalamic regions other than the SCH received the optic fibers. The ipsilateral projections to the CGLv, CGLd, and IGL were sparse, and a considerable number of uncrossed retinal fibers were found in the pretectal olivary nucleus. No retinal projections to the lateral posterior thalamic nucleus (LP) were found. Ipsilateral optic fibers projected sparsely to the medial part of the CS. The AOS consisted of a small DTN with a very few crossed retinal projections but no lateral and medial terminal nuclei. In addition, the AOS had no inferior fascicle.

How Does the Pulpal Floor of a Molar Tooth Develop

Abstract Development of the pulpal floor was reviewed from both macroscopic and microscopic perspectives, and relations between individual variation in tooth roots and their development are considered. It has been thought that the pulpal floor of a molar tooth is formed as a continuation of the coronal dentine in rodents. In humans, the interradicular dentine develops from a separate mineralization center or centers (subpulpal lobe), and only later does it unite with the coronal dentine. The subpulpal lobe appears in the tooth germ of some mammals other than humans, but it is absent in mice. The molars of Suncus have a large pulpal floor, and are useful as a model of the development of the bifurcation area. The calcified process of the pulpal floor in Suncus is divided into two stages : (1) the primary subpulpal lobe appears, and (2) a secondary subpulpal lobe forms aggregated by the small calcified centers. The number of secondary subpulpal lobes determines the root number. The connecting line among the subpulpal lobes on the completed tooth becomes a ridge (interradicular crista) on the external surface, and a groove (isthmus) on the internal surface. The pattern of the interradicular crista seems to depend on the number of roots. We addressed the following three macroscopic variants and these developments ; (1) three-rooted mandibular molar, (2) enamel projection, and (3) gutter-shaped root. These structures relate to developmental events.

Protuberance or fossa on the lateral surface of the mandible in primates.

In order to clarify the morphological characteristics and function of the protuberance and/or fossa on the lateral surface of the mandible, we examined 778 mandibles of 9 genera, 19 species of non-human primates. Both protuberance and fossa were found in Macaca, Chlorocebus, and Cercocebus at frequencies ranging from 0% to 60%. The protuberance was composed of compact bone and was similar to the mandibular torus in humans. A well-developed protuberance extended from the fourth premolar to third molar region, and was situated at the central part of the mandibular body, or continued on the oblique line. Sometimes the protuberance localized on the mandibular base. A deep and large fossa was found in all individuals of Papio, Theropithecus, and Mandrillus, and the bone width was thin in the center of the fossa. The fossa extended from the third premolar to the second molar region, and the deepest area was the first molar region. In Macaca, Chlorocebus, and Cercocebus, the curvature of the external table of the mandible created a fossa. In Colobus, and Hylobates, the external surface of the mandible looked concave because of the thickened mandibular base. These concavo-convex structures have some biological functions and represent an adaptive change for mastication.

Overview: The Mechanisms Controlling Root Morphogenesis in Mammalian Molars: —Morphological Relevance of the Tooth Root and Crown, Developmental Mechanisms, and Phylogenetic Aspect of the Tooth Roots—

Abstract Diet is one of the most important factors driving the process of natural selection in evolution. The dentition is adapted for the diet, contributing to the diversification and adaptation of extant vertebrates. Importantly, the structure of the molar shows marked variation in extant mammals to facilitate the processing of many kinds of food and support the occlusal force effectively. A tooth root is an important element, connecting a tooth with the jaw to support the occlusal force. However, morphological studies on teeth mainly focus on the crown, whereas there has been an insufficient accumulation of information on the morphogenic control mechanism of tooth root structures. There have been some reports on the root form in humans due to clinical demand, and recent studies on Hertwigs epithelial root sheath (HERS), which plays an important role in root development, have progressed rapidly. However, studies on the regulatory mechanism of the tooth root structure in relation to the jaw and crown are still awaited. In this paper, we highlight the following three issues : the morphological relevance of the tooth root and crown, and developmental mechanisms and phylogenetic aspects of the tooth roots. HERS produces several signaling molecules including bone morphogenic protein (BMP), Sonic Hedgehog (Shh), Wnt, ectodysplasin (Eda), and fibrobast growth factor (FGF). These factors regulate the closure of the pulp chamber floor to determine the numbers and width of the tooth roots, and then regulate the fusion, curve, and length. The tooth root differentiates and develops in conjunction with its crown. However, few studies have examined the tooth root from an evolutionary perspective. We need to advance research on the tooth root including the whole tooth in developmental biology, evolutionary biology, and comparative odontology.

Observation of Lateral Mandibular Protuberance in Taiwan macaque (Macaca cyclopis) Using Computed Tomography Imaging

Morphological characteristics of the protuberance on the external surface of the mandible in Taiwan macaque (Macaca cyclopis) was investigated using cone-beam computed tomography. We observed 49 skulls of M. cyclopis. Of 7 skulls with deciduous and mixed dentitions in which M2s did not erupt, the protuberance was not found. Of the 13 skulls with mixed and permanent dentitions in which M2s had erupted, a palpable protuberance was found in one specimen. Of the 29 samples in which M3s had erupted completely, a perceptible protuberance was found in 2 samples, and palpable protuberance was found in 8 samples. Thus, the protuberance was found in 10 samples of the 29 samples with complete dentitions (34.5%), and the emergence of the protuberance may have been related to mandibular growth. In the case of the well-developed protuberance, it extended from the P4 to M3 region but did not extend to the mental foramina. By using cone-beam computed tomography, it was determined that the protuberance was composed of cortical bone and was the thickest in M2 region. Since the protuberance consisted of homogeneous cortical bone, it was considered to be the result of normal bone growth similar to the mandibular torus in humans.

Geographical variations in the cranium ofSaguinus geoffroyi

In terms of craniometry, we examinedHershkovitzs hypotheses that, inSaguinus geoffroyi, populations on the western shore of the Rio Atrato were closely related toS. leucopus, and that a morphocline could be traced from the easternS. geoffroyi population to the western one. We detected a morphological sequence from east to west (or east to west) but did not find any evidence supporting the former hypothesis.