Yoriaki Kanri

Use of Microfocus X-ray Computer Tomography for 3D-image Construction and Quantitative Morphoanalysis

Abstract Microfocus X-ray computed tomography (μCT) is becoming widely used in various research fields relevant to the oral sciences. This technology, in conjunction with computer-assisted 3D reconstruction and quantitative structural analysis, is most suitable for investigating hard tissues in a non-invasive way. Despite this recognition, it still remains a concern whether the data acquisition process is conducted properly and accurately in order to ensure the reproducibility of 3D imaging and the determination of structural parameters such as bone volume (BV) and surface area (BS). In this report, we aim to provide an overview of the experimental procedures and conditions that are necessary for optimizing the acquisition of gray-scale CT images and their conversion into digital images (TIFF or JPEG) prior to 3D reconstruction and measurements. Towards these objectives, we collected μCT images of a 4-week-old mouse temporomandibular joint using a μCT apparatus (Nittetsu ELEX Co., ELE-SCAN model). Data proceedings and measurements were conducted using software (RATOC System Engineering Co., TRI-BON and TRI-SRF2). Special care was taken in optimizing experimental conditions and variables, e.g., X-ray tube voltage and current, selection of an adequate shiftvalue to compensate the mismatching between the specimen-rotating center and incident X-ray beam, and window level and width for contrast adjustment. The results of our empirical approach showed that careful selection of the experimental conditions and computation variables ensures the high quality of the 3D images and the accuracy and reproducibility of the quantitative measurements. The magnitude of errors associated with each of the determined structural parameters was confirmed to be within 3% of the determinations. Further knowledge and refinement of μCT technology and data acquisition will help to improve our understanding of the architecture and dynamic modeling of hard tissues.

Patterning of Molar Tooth Roots in Mammals

Abstract Tooth morphogenesis is regulated by reciprocal interactions between the dental epithelium and odontogenic mesenchyme. As tooth roots are fundamental structures of the tooth support system, the morphology and functions of the roots are very important. However, basic information on the morphology of tooth root patterning and the molecular mechanism of root morphogenesis is largely unavailable. Following tooth crown formation, the dental epithelium forms a double-layered Hertwigs epithelial root sheath (HERS) derived from inner and outer enamel epithelium. Previous studies have reported that HERS plays an important role in tooth root development. Here, we report the correlation between the number of major cusps of the tooth crown and number of tooth roots of first molar and last premolar teeth in several extant mammals. We also discuss the molecular mechanism of tooth root patterning by introducing studies of mouse mutants and human syndromes associated with an abnormal molar morphology.

Solubility Properties of Carbonatoapatites with Discrete Stoichiometric Compositions

Acquisition of substantial amounts of carbonate, acid phosphate and other impurities is encountered universally in biogenic apatites in vertebrates. To date, however, much still remains to be elucidated about the driving force behind carbonatoapatite formation in physiological environments and whether the solubility of carbonatoapatites depends on their stoichiometric composition and types of carbonate substitution. We here used discrete groups of carbonatoapatites prepared under various aqueous conditions and determined their solubility during acid equilibration. We selected a stoichiometry model to describe these crystal compositions, i.e., (Ca) 5-x (HPO4) v (CO3) w (PO4) 3-x (OH)1-x. All apatite products were equilibrated in phosphoric acid solutions at 25° for a maximum of 28 days under a constant partial pressure of CO2 i.e., 1.8% CO2/N2. After this long-term equilibration, each of the apatite samples was verified to reach a plateau of the ionic activity product (IP), which was calculated on the basis of the experimentally determined stoichiometries. Notably, the solubility product values of carbonatoapatites were confirmed to depend primarily on their carbonate contents. Importantly, analysis of the solubility data and electron microscopic observation validated that the incongruent equilibration, i.e., dissolution of the original crystal and coprecipitation of projections formed on the original crystals, was most prominent for batches of B-type carbonatoapatites originally prepared at alkaline conditions. In contrast, the solubility of A, B-type carbonatoapatites, which were originally prepared at neutral conditions, yielded the so-called central-core dissolution without morphologic evidence for projection-type precipitation. The results obtained support the hypothesis that the stoichiometry and solubility properties of carbonatoapatites depend primarily on the solution environment, including the gas atmosphere, where crystal precipitation has occurred, so that a congruent equilibration of biogenic or synthetic carbonatoapatites might be pursued under conditions similar to the originally precipitating milieu.

Histomorphometric Analysis of Development and Morphogenesis of Mouse Temporomandibular Joints

Abstract The temporomandibular joint (TMJ) is a multicomponent organ including the condyle, mandibular fossa, articular disc and clefts, and surrounding tissues. In the present study, we reported the chronology of TMJ development and associated tissue-marker expression in C57BL/6 mice. Wild-type mice of embryonic day 12.5 (E12.5) through postnatal day 7 were examined by histochemistry (HE, metachromasia by toluidine blue), enzyme-histochemistry for alkaline and acid phosphatases (ALP and TRAP) and immunohistochemistry for BrdU and type II collagen. The results confirmed that: 1) the condylar blastema was first designated as a troop of ALP-positive cells at E13.5, and some of those cells also displayed BrdU incorporation, 2) after differentiation of the blastema, condylar morphogenesis progressed from the anterior to the posterior direction, while the mandibular fossa of discrete origin developed inversely, and 3) development of the articular disk and superior/inferior clefts appeared to link intimately with the articular function. Histomorphometric analysis, in conjunction with BrdU administration, further revealed that condylar growth during development can be divided into three stages: the initial slow growth due to cell proliferation by E13.5, the second rapid growth between E14.5 and E17.5 due to production of extracellular matrices instead of acceleration of cell proliferation, and the last functional adaptation after birth that progresses at a steady growth rate coupled with systemic body growth. The current observation also supported the spatial linkage of the condylar blastema with a group of the mesenchymal cell population that is involved in mandibular bone development. Further analysis in conjunction with three-dimensional reconstruction of ALP-positive cell condensation is required to clarify the origin and spatio-temporal development of condylar blastema in detail.

Sexual dimorphism of porcine amelogenins: male-specific amelogenins have strong adsorption properties onto apatite crystals.

Abstract The present studies were undertaken to investigate the sexual dimorphism of porcine amelogenins and to gain information as to whether excesses of male amelogenins, if any, possess functional significance in protein-crystal interactions. Enamel proteins, including the intact full-length amelogenins and their degraded polypeptides, were isolated from the secretory enamel of male and female pigs. To identify the amelogenins among the separated pools of male- and female-matrix proteins, rabbit anti-C13 and C25 peptide sera were used, which reacted specifically with the conserved C-terminal domain. Immunoblotting showed that a few extra members of the amelogenins, sharing common epitopes at the C-terminus, were recognized in male products. The apparent yield of the male amelogenins was only marginal, on the basis of their stained intensities on the gel, but the secreted male amelogenins demonstrated selective (probably the strongest among the amelogenins) adsorption properties onto apatite crystals. Reflecting the general symmetric electrophoretic profiles of the male- and female-enamel proteins in toto, there were no sex-linked differences in the protein-crystal interaction and the resulting regulatory function of crystal precipitation.

Metastasis of colon adenocarcinoma to the mandible: A case report

Abstract Metastatic tumors to the oral cavity are uncommon. In this article, we report a case of metastatic adenocarcinoma of the colon to the mandible with imaging features. A 73-year-old man with a history of colon cancer and liver metastasis was referred to our hospital with a chief complaint of swelling and pain in the right mandible. Panoramic radiograph revealed a radiolucency with ill-defined margin. Computed tomography showed an osteolytic lesion with cortical bone destruction. Magnetic resonance imaging showed a round-shaped homogeneous intensity mass expanding from the mandible. Histopathological diagnosis revealed metastatic adenocarcinoma of the colon.

Glandular odontogenic cyst: a report of four cases

Abstract A glandular odontogenic cyst is a developmental cyst that is a clinically rare and histopathologically unusual type of odontogenic cyst. In this article, we describe four cases of glandular odontogenic cyst. Glandular odontogenic cyst was defined as a well-defined unilocular lesion on panoramic radiographs and multidetector computed tomography. Furthermore, the connection of the cyst to the periodontal tissue was one of the common features of the four cases. The results of the present study indicate the clinical and imaging features of glandular odontogenic cyst.

Central giant cell lesion of the mandible in a 2-year old girl

Central giant cell lesions are rare, benign, osteolytic, pseudocystic, solitary, localized lesions that are common in the skeletal structure, but less so in the maxillofacial region. Furthermore, to perform panoramic radiography and cone-beam computed tomography, it is necessary to prepare patients properly and to position their heads carefully. However, this can be difficult in pediatric patients, who may be anxious. In this report, we describe the case of a central giant cell lesion of the mandible in a 2-year-old girl that was evaluated with multidetector computed tomography.