The purpose of this study was to investigate the determinability of the distance between the pulp horns (PHD) radiographically under routine clinical conditions. This study was carried out on 36 maxillary and 28 mandibular first and second molars which were extracted because of periodontal diseases. Prior to extraction two radiographs were taken from each tooth, one using the bisecting-angle technique and the other by using the bitewing technique. After the extractions, each tooth was burred on the distal and mesial approximal surfaces and pulp horns were found. The distance between the pulp horns was measured (anatomical measurement). Using bisecting-angle and bitewing radiographs, 11 clinicians measured the PHD values of each tooth (radiographic measurement). In our study the residual error in mandibular molar teeth was statistically lower when compared to maxillary molar teeth (p < 0.01). Statistically significant differences were found between anatomic and radiographic measurements (p< 0.01) in maxillary molars. No statistically significant difference was found between anatomical and bisecting-angle measurements in mandibular first and second molars. As a result, it is concluded that bisecting-angle techniques are useful in correctly determining the PHD values in mandibular molars. (J. Oral Sci. 40, 143-146, 1998)

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The nerve regenerative process has been investigated by many studies. However, the quantification of the degree of crush of peripheral nerves has not yet been performed. The aim of this study was to determine and standardize the ligature intensity and crush level of the hypoglossal nerve of guinea pigs. The compound action potentials evoked by electric stimulation were used as an index of the degree of nerve crush. To demonstrate nerve regeneration after ligating and crushing of the right hypoglossal nerve, fluorescein isothiocynate conjugated cholera toxin-B subunit (CTb-FITC) was injected into the intact fiber of the left hypoglossal nerve, and the central side from the crushed region of the right hypoglossal nerve fiber. The total cross sectional area of the retrograde-labeled hypoglossal motoneurons was investigated under a confocal laser scanning microscope. The results of the evaluation using CTb-FITC indicated that the nerve regeneration occurred from two weeks after crush and recovered in six weeks. (J. Oral Sci. 40, 147-152, 1998)

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In the atrioventricular canal (AVC) and outflow tract (OT) of the developing heart, endothelial cells transform specifically to mesenchymal cells. The mesenchymal cells migrate into the underlying acellular matrix termed cardiac jelly and form endocardial cushion tissue. It is believed the that the highly hydrated nature of cardiac jelly is ascribed to sulfated glycoconjugates in the components of jelly matrix. In the present study, we have visualized the distribution and its temporal changes of sulfated glycoconjugates in the embryonic heart from stage 12 to 26 using whole mount alcian blue (AB) histochemistry. Atrial matrix was AB-negative in all the stages examined. Cardiac jelly in the AVC and OT were positive and the staining intensity increased as heart development proceeded, while AB-positive staining in the matrix of the ventricle became negative by stage 19. At stages later than 19, AB-positive matrix was localized in only the AVC and OT where endothelially-derived mesenchymal cells populated. (J. Oral Sci. 40, 153-157, 1998)

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The mesencephalic projection pattern of axons arising from the medullary dorsal horn (MDH) was studied on the basis of axonal transport of Phaseolus vulgaris Leucoagglutinin (PHA-L). After large injections of PHA-L into both the superficial and deep laminae of the MDH, labeled fibers were observed in the anterior pretectal area (ATP), internal gray matter of the superior colliculus (InG), and rostral linear raphe nucleus (RLi) in the contralateral mesencephalon, and also in the ipsilateral parabrachial nucleus (PBA). Restriction of PHA-L to only the superficial laminae resulted in heavy axon labeling and varicosity in the APT and little labeling in the lateral part of the InG of the contralateral mesencephalic nuclei and the dorsal part of the ipsilateral PBA. On the other hand, after injections into the deep laminae, labeled axons were distributed mainly in the contralateral InG and RLi. Therefore, it is concluded that there are two different major pain pathways from the superficial and deep laminae of the MDH to the mesencephalic nuclei, processing nociceptive information in the trigeminal system. (J. Oral Sci. 40, 159-163, 1998)

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The effects of propofol, a hydrophobic intravenous anaesthetic, and fentanyl, an opiate analgesic, on extracellular concentrations of γ-aminobutyric acid (GABA) in the nucleus accumbens of rats were studied using in vivo brain microdialysis. The concentrations of GABA in the microdialysate of the nucleus accumbens reached a stable baseline value approximately 24 h after probe insertion and were not affected over the ensuing 250 min by intravenous injection of vehicle (1.0 ml/kg) or perfusion of tetrodotoxin (2 μM) into the nucleus accumbens via the dialysis membrane. Propofol (2.5 mg/kg and 10.0 mg/kg i.v.) did not significantly affect the accumbal microdialysate concentration of GABA over the 250 min of quantification. Fentanyl (100 μM) infused for 25 min into the nucleus accumbens via the dialysis membrane produced a marked and transient increase in accumbal GABA concentration to a maximum of approximately 1200 % at its peak effect that occurred at 25 min after cessation of the fentanyl infusion. (J. Oral Sci. 40, 165-170, 1998)

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A study was conducted to investigate the relationship between osteoporosis and alveolar bone loss. Alveolar bone loss was evaluated by radiographic and visual inspection of rats with experimental osteoporosis. Twenty 4-week-old female Sprauge-Dawley rats were divided into the following groups : Group A-ovariectomized and given a standard solid diet; Group B-ovariectomized and given a calcium-deficient diet; Group C-sham-overiectomized and given a standard solid diet; and Group D-sham-ovariectomized and given a calcium-deficient diet. After 4 weeks, the rat were euthanatized. The maxillae, mandibles, femurs, and tibias were removed carefully and fixed in 10% neutral buffered formalin. The bone mineral density of each bone and the alveolar bone loss were measured. The bone mineral densities of the maxillae, mandibles, femurs and tibias in Group C were significantly higher than those in Groups B and D, but not higher than those in Group A. However, there were no significant differences between any of the groups with regard to alveolar bone loss from the cemento-enamel junction to the molar bone crest. Therefore, it was concluded that osteoporosis itself may not be capable of causing periodontal destruction, and thus may not be a major factor in periodontal disease. (J. Oral Sci. 40, 171-175, 1998)

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