Two different reflex responses were recorded from the lateral pterygoid muscle (LPT) following controlled mechanical tapping of the chin in alpha-chloralose anesthetized cats. The short latency response (L1: 3.8±0.6 msec latency) and the long latency response (L2: 18.4±1.3 msec latency) were elicited. L1 had low threshold and its latency was similar to the mono-synaptic masseteric jaw-jerk reflex (M). L1 did not disappear after local anesthetization of the chin and temporomandibular joints (TMJs). Direct electrical stimulation of LPT evoked H-reflex in LPT. The threshold of L2 was significantly lower than that of nociceptive, short-latency jaw-opening reflex response in the digastric (DIG). L2 was diminished, like the long-latency jaw-opening reflex in DIG, by local anesthetization of the chin and TMJs. These results indicated that L1 would be the proprioceptive stretch reflex, as occurred in synchronization with activation of the jaw-closing muscles and that L2 may be non-nociceptive reflex induced by low threshold mechanoreceptors in the chin and TMJs, as synchronized with activation of the jaw-opening muscles. The responses of L1 to conditioning electrical stimulation to the oral mucosa was definitely different from those of M. These reflex properties of LPT in cats suggest that LPT would function as a stabilizer of TMJ discs and condyles during jaw-opening and closing triggered from orofacial regions.

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Authors have developed a simple method of measuring the formation of calcium phosphate precipitates using a pH electrode. Using this method, we studied the inhibitory effects of Chinese traditional (Kampo) medicine, Rikko-san and of Rikko-san plus whole saliva from human on the formation of calcium phosphate precipitates.
At the concentrations of 0.1-0.5 mg/ml, Rikko-san showed the significant inhibitory effects both on the increase of induction time and the rate of hydroxyapatite transformation. Since Rikko-san is known to have little side effects, this may be safer than synthetic chemicals (i. e, HEBP). If safety dose of Rikko-san is considered, Rikko-san may be a potent anti-calculus agent.
The diluted whole saliva from human (2-10%) showed the inhibitory effect only on the increase of induction time without the decrease of the rate of hydroxyapatite transformation. Simultaneous addition of Rikko-san and whole saliva showed their inhibitory effect independently and showed the summation of both inhibitory effects.

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We examined the morphology of the horse coronal cementum, to study Sharpey's fibers and the blood vessels which become covered with coronal cementum. Histological studies were carried out on 12 functioning mandibular molar teeth of horses, immediately after slaughter. The arrangement of fundamental microstructures composed of collagen fibers (Sharpey's fibers) in coronal cementum and the distribution of blood vessels were studied by light and scanning electron microscopy, and light microscopy was used to observe the shape and distribution of the cemento -enamel junction. The molars were hypsodont, with long crowns and short roots. The apices were open as a result of continuous growth. Pericoronal cementum had a laminated structure, which may have been formed intermittently by cementoblasts in the periodontal ligament and at the eruption in the gingiva. The diameter of Sharpey's fibers at their insertion into cementum was about 50μm. These fibers had diameters of 20-25μm in the deep layer and in the surrounding mineralized cementum. The vascular system was well developed in the concave portion on the buccal and lingual surfaces of the crown. Along the cemento-enamel junction relatively large blood vessels had entered the concave region, and along their way they gave off numerous branches in the coronal cementum. There were sinusoidlike vessels on a part of the enamel surface. The cemento-enamel junction in the horse crown had a characteristic structure: the enamel surface had a number of scallop-shaped resorption concavities, which provided firm connection between the cementum and the enamel.

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The distribution of types I and III collagen and fibronectin was investigated in the anteroposterior middle portion of the palatal shelves before (day 14.0) and after (day 16.0) the shelf elevation of mouse fetuses by the electron immunogold technique using affinity purifiedpolyclonal antibodies. In the area adjacent to the basement membrane, type I collagen was localized more densely in the nasal area than in the oral area on day 14.0 and on day 16.O. However, the distribution of type collagen showed no significant difference between the nasal area and the oral area on either days. The ratios of type I to type III collagen varied among different areas of palatal mesenchyme both on day 14.0 and on day 16.0, namely, it was higher in the nasal area than in the oral area and, in the nasal area, it was higher on day 14.0 than on day 16.0, whereas in the oral area, there was no difference between either days. By the double immunostaining technique, it was revealed that types I and III collagen were often present in the same cross-banded fibrils. Fibronectin was localized between the surface of palatal mesenchymal cells and collagen fibrils, within collagen fibers and on filamentous structures in the extracellular space. Fibronectin was also localized within the basement membrane of the palatal epithelium, both in the lamina lucida and the lamina densa. The role of types I and III collagen and fibronectin in the palatal shelf elevation is, discussed on the basis of the results obtained.

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Disturbed mineralization in the developing enamel of rat incisor induced by the single injection of colchicine which has been considered to bound to microtubular protein (tubulin) and inhibits polymerization of microtubles as well as dissociates the microtubular structure was investigated. Wistar rats weighing about 100 g were injected with colchicine (0.17mg/100g body weight) subcutaneously and were sacrificed from 6 hours to 10 days after the injection. The animals were also injected with tetracycline hydrochloride (10mg/100g body weight) 6 hours before the sacrificing in order to observe the mineralizing sites at the time of sacrificing. The longitudinal undemineralized ground sections and demineralized sections of the developing enamel of upper incisors were investigatdby means of microradiography, fluorescence microscopy and the various histological stainings.
Most characteristic change observed in the developing enamel was alternate appearance of hypomineralized and hypermineralized regions at the middle and late stages of maturation. The former was much wider in its range than the latter and was labelled intensely by tetracycline whereas the latter not labelled. These changes were observed from the surface layer to the innermost layer. The irregular arrangement and detachment of the ameloblasts were also observed mainly at the middle and late stages of maturation. However, the cellular changes and the disturbed mineralization pattern could not be correlated with the cyclical cell modulation of the maturation ameloblasts. The hypomineralized enamel was secondarily mineralized as it moves towards incisal side bythe tooth eruption. On the other hand, the very narrow hypoplastic incremental line was formed at the matrix formation stage immediately after the injection.

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To examine anticariogenic effect of the extract from husk of cacao bean (cacao husk), a glucosyltransferase inhibitor (Kuwashima et al. 1991), male S. D. rats (ca. 48g) which had been infected with Streptococcus sobrinus 6715 and fed a cariogenic diet containing no cacao husk, 0.02% or 0.2% cacao husk for 53 days. In a separate in vitro experiment, morphological effect of cacao husk on bacterial cells and insoluble glucan aggregates were observed by means of electron microscopes. Number of S. sobrinus cells adhering to molars surface and value of the dental plaque index of molars were almost equal among the three diet groups. However, in comparison of total caries scores including smooth surface, sulcal and proximal lesions, it was revealed that there are 7% and 31% suppression of caries development, responding to 0.02% and 0.2% cacao husk added to a cariogenic diet. In vitro experiment, electron microscopic observation showed that most of the bacterial cells cultured in 1% sucrose medium containing 0.02% cacao husk were clearly visible. Such finding let to assume that organic acids produced by the bacterial cells are apt to diffuse into saliva. As results of this experiment it was confirmed that cacao husk has a preventive potential against dental caries. Moreover, no toxic effect of cacao husk on rats were observed in this study. Thus, it is anticipated that cacao husk would be used for anticariogenic agent in practice.

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The localization of two distinct intracellular aspartic proteinases, cathepsins D and E, in rat oral tissues was determined by immunoprecipitation and immunohistochemistry using antibodies specific for each enzyme. In normal gingiva and tongue, almost all the hemoglobin (Hb)-hydrolyzing activity at pH 3.8 was immunoprecipitated with the antibodies specific for cathepsin D, indicating that little or no cathepsin E activity is present in these tissues. Cathepsin E was found at high levels in the cervical lymph node, which represented about 80% of the total Hb-hydrolyzing activity. In the submandibular gland, the level of cathepsin E was much less than that of cathepsin D. Intense staining by anti-cathepsin D antibody was found in the stratum granulosum of mucosal epithelium, the fibroblasts of the periodontal ligament, the osteoblasts on the bone surface, the odontoblasts of the dental pulp and the striated duct of submandibular gland, whereas staining indicating cathepsin E antigenicity was found in the striated duct of submandibular gland and the macrophage-like cells of mesenchymal tissues. The distinct localization of cathepsins D and E in these tissues suggests their different physiological significance in these tissues.

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The enamel structure of the agamid lizard, Japalura polygonata, was examined by scanning electron microscopy and electron microprobe analysis. The enamel with no prismatic structure was 20μm in thickness at the apical portion of the cusp. The pseudo-prism showing the sinusoidal arrangement of crystallites found usually in the mammal-like reptiles, and the pre-prism with a seam found in certain primitive mammals, were common structural features of the enamel in Japalura. These structures may be regarded phylogenetically as secondary or convergent developments rather than essential characteristics with an evolutional significance.
High concentration of iron was detected in the surface enamel layer 2μm in thickness. This layer was acid resistant and caused probably the pigmentation of the teeth.

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