The aim of this study was to document the historical change of dental caries lesions in the Japanese people. The majority of carious lesions in historical populations from the Jomon to Edo period were located in the neck and/or root of the approximal surface (NRAS). Caries on the occlusal surface (OS) were rare in both the Jomon and Kofun populations, but there was a relatively high rate (17.6-24.7%) in the Kamakura, Muromachi and Edo periods. People in both the Jomon and Kofun periods had severe dental attrition; therefore, due to the disappearance of fissures and pits, caries on the OS did not arise. However, after the Kamakura period, the attrition was moderate, so occlusal caries increased. Caries on the lingual surface (LS) and the neck and/or root of the lingual surface (NRLS) were rare in all Japanese periods. The incidence may be associated with a self-cleaning action with the tongue and the saliva. In the modern population, the most frequent lesion is on the approximal surface (AS), followed by the NRAS and the OS. The rate of coronal caries is higher than that of root caries only in modern times. It seems reasonable to suppose that the former is a modern type of caries, and the latter is ancient. Furthermore, it can be said that from the Jomon to Kofun or from the Kofun to Kamakura periods, and from the Edo to modern times, are turning points for different types of caries in the history of Japan. The type of carious lesion is a good indicator of oral health condition, including dietary habits, subsistence and lifestyle in each period.

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The purpose of this study was to determine the time course of masticatory recovery after severance of the unilateral medial branch of the hypoglossal nerve (HN). In severed-nerve cats, food intake rate recovered up to 80% in 2 weeks with tongue deviation during mastication. Each genioglossus EMG (30% in the cutting side and 150% in the intact side) stabilized after 25 days. Masseter muscle EMGs in both sides stabilized at an almost normal level in 25 days. Although digastric muscle EMGs in the HN cutting side stabilized at an almost normal level after 25 days, those on the HN intact side were at 50%. The extent of jaw opening decreased by up to 70-80% and the masticatory period increased 1.5 times for 25 days.
The balance of co-operative mastication after severance persisted for one month.

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The purpose of this study was to investigate the clonal types of black-pigmented anaerobes isolated from infected root canals and subgingival plaque. Twelve patients, who had single-rooted teeth with selected chronic apical periodontitis and had not undergone endodontic treatment, were chosen for thisstudy. Microbiological specimens from the root canals were collected with three sizes of H-files, and thosefrom six subgingival sites of the same teeth were collected with paper points. The isolates were identified by the 16S rRNA gene-directed PCR method, and the gene types were determined by the arbitrarily primed PCR (AP-PCR) method. Porphyromonas gingivalis and Prevotella nigrescens were the most frequently isolated species from the root canals (41.7%) and from subgingival plaque samples (50.0%) in 12 patients, respectively. Four patients simultaneously harbored the same species in the root canal and subgingival plaque (three patients harbored P. nigrescens and one patient P. gingivalis). The AP-PCR patterns of isolates from the root canal and subgingival plaque were identical in at least three out of 12 patients. These results support the hypothesis that the pocket is one of the possible sources of root-canal infection.

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To study which physical properties of a food bolus trigger swallowing during mastication of gelatinous food, we measured the texture of a bolus immediately prior to swallowing by texture profileanalysis. Filter paper soaked in 0.2M tartaric acid (acid stimulation) or distilled water (DW stimulation) was placed on the dorsal surface of the tongue of 10 healthy adult participants for 1 minute before they masticated rice cake (RC) or gummy candy (G). The G bolus was significantly (p<0.05) harder immediately prior to swallowing after acid stimulation than after DW stimulatien. On the other hand, hardness, adhesive. ness and cohesiveness of the RC bolus did not differ significantly between the two masticatory conditions (after acid stimulation and DW stimulation). After DW stimulation, the texture of the RC bolus during the middle stage of mastication was compared with that just before swallowing. The RC bolus at the middle stage was significantly harder (p<0.001) and more adhesive (p<0.05) than just before swallowing. These results suggest that the degree of adhesiveness of a bolus might be closely related to the swallowing threshold for gelatinous food such as rice cakes.

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The electrophysiological and pharmacological properties of the voltage-gated Ca²⁺ channels in MC3T3-E1 cells were analyzed using the perforated whole-cell patch-clamp technique. When the voltage was depolarized by step pulses from a holding potential of -104mV, the cells displayed transient inward currents (-4.25±0.25pA/pF, n=16) in 10mM Ba²⁺ solution. The activation threshold for the inward Ba²⁺current was about -60mV and the peak existed between -40 and -20mV. The steady state activation and inactivation properties of the inward Ba²⁺ current generated a window current in the range of -70 to -40 mV. Gd²⁺ (0.1mM) inhibited the inward Ba²⁺ currents by about 60%. Ni²⁺ (0.1mM, a blocker for T-type and R-type Ca²⁺ channels at this concentration), nifedipine (5μM, L-type Ca²⁺ channel blocker), ω-conotoxin GVIA (3μM, N-type Ca²⁺ channel blocker) and ω-agatoxin TK (200nM, a P/Q-type Ca²⁺ channel blocker) did not inhibit the currents. Bay K 8644 (0.5μM, a dihydropyridine agonist for L-type Ca²⁺ channel) also did not affect the Ba²⁺ currents. The results suggest that Ca²⁺ channels with novel properties are expressed in MC3T3-E1 cells.

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Lingual papillae and the connective tissue core (CTC) of Japanese serow and Bighorn sheep, which belong to the grass eating animals of artiodactyla, were studied by light and scanning electron microscopies and compared to those of other animal species. Concerning the external form of filiform papilla, both species had a thick main process and several slender small processes. The CTC of the filiform papillae of Japanese serow showed only a U-shaped arrangement of slender protrusions, while that of Bighorn sheep consisted of numerous protrusions arranged in a U-shape but with several posterior protrusions fused with each other. The CTC of the fungiform papillae was columnar in shape and had several shallow hollows for taste buds in both species. Large conical papillae were found on the lingual prominence and their CTCs were covered with numerous small spines of secondary CTC. The number of vallate papillae was about 20 in Japanese serow with several in Bighorn sheep and showed a U-shaped arrangement in the posterior area of the lingual prominence. Numerous taste buds were distributed in the grooved side epithelium of the central vallate papillae, and numerous serous gland ducts opened to the base of the groove in both species. Foliate papillae were not found and the surface of the lingual root was flat and smooth with mucous glands in the lamina propria in both species.
From the above results, the CTC of filiform papillae of Japanese serow was very similar to that in rabbits which showed a simple U-shaped arrangement. The CTC of the filiform papillae of Bighorn sheep had an intermediate stereo structure between Japanese serows and pronghorns. It is thought that these structures became more complicated from Japanese serow to Bighorn sheep, Pronghorns, Rocky mountain goats and to Shiba goats and finally fused type of cattle in artiodactyla.

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