The enameloid of fish teeth is analogous to the enamel of mammalian teeth and similary highly mineralized. Quantitative electron microprobe analysis of the teeth of various teleost fishes when considered from the view point of their systematic classification indicates that fishes may be placed into two groups in terms of the fluoride concentration in the enameloid; one group containing fluoride of more than about 2.0% in the enameloid; and the other containing less than about 0.3%(Figs.6 and 8). The fluoride concentration in the enameloid is related to the fish phylogeny rather than to the fluoride concentration in the environmental water (Table 1, Figs.2-8). It is also not related to feeding habits, though the form, size and distribution, of the teeth show a wide range of adaptation in association with feeding habits (Figs.1and5, Table2). It seems to indicate that the evolution of the chemical composition of enameloid is completely independent of morphological adaptation of teeth. Similar phenomena have been found related to the iron concentration in enameloid.
Crystallographic investigations indicate that, in the high fluoride enameloid, apparently fluoride is present in the apatite as Ca₁₀ (PO₁) e (F, OH) or Ca₁₀ (PO₄) ₆ F₂ (Figs. 9-11).
Since the fluoride concentration in the dentin and bone is very low, in contrast the high concentration of fluoride which can be observed even in the developing enameloid, it seems that there is a peculiar mechanism under the control of the ameloblasts which concentrates the fluoride in enameloid.
The present investigations seem to provide evidence which could lead to a better understanding of the evolution of the mechanisms of tooth enamel formation (Figs. 12and13).

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The purpose of this investigation was to study the presence of bacteria chondroitinase ABC and basterial hyaluronidase in inflamed human gingiva by a fluorescence antibody technique. The presence of chondroitinase ABC was demonstrated in all of 30 cases and hyaluronidase was detected in 21 cases. Both enzymes existed on the surface of gingival epithelium, in the epithelium, in the subepithelial connective tissue and in the cytoplasm of phagocytes. The existence was mainly in the sulcular portion. The tissue or cells in which the enzymes localized suffered from destruction such as degenera-tive, atrophic and/or necrotic changes, and widened intercellluar spaces were also observed in the sulcular epithelium.
From the above results, it was indicated that chondroitinase ABC and hyaluronidase, produced in dental plaque, penetrated from the surface of gnigival epithelium by hydrolysing acid mucopolysacchalide in the space of epithelium to supepithelial connective tissue and initiated periodontal disease.

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The purpose of the present investigation was to detect bacterial chondroitinase and hyaluronidase in bacteria of 15 species as shown in Table 1.
Smear specimens obtained from their pure culturing were stained with FITC-labeled rabbit antiserum to bacterial chondroitinase and hyaluronidase. Fluorescence which indicated localization of chondroitinase was observed in Staphylococcus aureus, Staphylococcus epidermidis, Actinomyces naeslundii, Treponema macrodentium, Propionibacterium acnes and Veillonella alcalescens. That of hyaluronidase was demonstrated in only 3 species of Stereptococcus mutans, Streptococcus sanguis and Staphylococcus aureus. While the intensity of fluorescence was strongly demonstrated in Staphylococcus aureus, Actinomyces naeslundii and Treponema macrodentium, the acitivity of other bacteria which showed fluorenscence positive was very weak.

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Morphological changes in the vascular system of the jaw teeth and their development in the pleuronectid, K. baicoloratus, were observed by the India-gelatin perfusion method. The vasculars were supplied to the pulp and the odontogenetic zone with the blood capillaries forming a network in the odontogenetic zone. The capillaries were thinner in the predentine and odontoblastic layer (3-6 μm) than in the subodontoblastic layer (7-15 μm). The vascular system changed in the odontogenetic zone with the development of the tooth germ. Thus, the bell stage of the tooth germ can be divided into an early and later stage on the basis of morphological changes in the vascular system, The capillaries were supplied richly to the odontogenetic zone at both the early and later stages. However, their network became more dense at the later stage. The tooth germ developed slowly at the end of the later bell stage, which is known as a resting phase. Less capillaries were distributed to the odontogenetic zone during the resting phase. Thereafter, they were again richly distributed in the formative and eruptive phase. The complete teeth can also be divided into an early and later stage on the basis of morphological changes in the vascular system. The capillaries are supplied richly to the odontogenetic zone during the early stage of a complete teeth, as in the bell stage, but decrease at the later stage. The vessels are less distributed on the dental follicle at the bell stage. They are separated from the outer dental epithelium during the early bell stage, but come in contact at the later stage. The contact of the capillaries with the outer dental epithelium is related to the mineralization and maturation of the enameloid. The results lead to the conclusion that morphological changes in the vascular system of the jaw teeth and their germs during development are a part of the life cycle of the formative cells of the teeth.

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Occulusional movements of the pharyngeal bones of two cyprinid fishes, Acheilognathus tabira and Gnathopogon coeulescens were compared on the bass of the shapes of the pharyngeal dentitions, pharyngeal and masticatory processes of the basioccipital bones and several muscles inserted in the pharyngeal bones.
In A. tabira, the tooth rows consisted of teeth with narrow and long occulusional surfaces, and both sides fromed a chewing area that was adaptable to the back and forth movements. The lavator arcus branchialis V muscle (LAB V) was well-developed and the occulusional line is horizontal. Therefore, the chewing force was produced by only LAB V, and the retractor os pharyngeus inferioris muscle (ROPI) cannot play the role of chewing. Because ROPI contracts along the oesophageal spincter that is well-developed, it cannot adduct the pharyngeal bones. Therofore, ROPI merely retracted the pharyngeal bones. The pharyngeal bones were lavated strongly by LAB V and moved back and forth with the retraction of ROPI and protraction of the subarcualis rectus communis muscle (SRC) in A. tabira.
On the other hand, in G. coerulescens, the transversus ventralis V muscle (TV V) was welldeveloped.The pharyngeal bones move transversally with the adduction of TV V and ROPI and the abduction of the cleithropharyngeus superficialis muscle (CPS). Beceuse the occulusionaline descends backward, the chewing force results from the contractions of LAB V and ROPI. Thus, ROPI has several functions, the retraction, chewing and adduction of the pharyngeal bones, in G. coencle-scens. The pharyngeal bones move back and forth during weak chewing and transversally during strong chewing. Arrangement of the rows of spinal tubercles on the occulusional surface is adaptable to the movements of the pharyngeal bones.

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The lingual dorsal surface of the musk shrew, Suncus murinus, was examined by scanning electron microscopy after removal of the extracellular material by acid hydrolysis. The tongue of this species is long and slender with a narrowly protruding tip. Filiform papillae were distributed over the entire dorsal surface of the tongue excepting the lingual radix zone. The upper part of the conical filiform papillae was branched into several twigs while the middle anterior revealed a round slope. A relatively small number of fungiform papillae were seen scattered among the filiform papillae. The dome-shaped fungiform papillae were shorter and wider than the filiform papillae.
Microridges were widely distributed on the epithelial cell surface between the filiform and fungiform papillae. The free surface of the filiform, fungiform and circumvallate papillae, however, were devoid of distinct microridges. The results were discussed in relation to the possible role of microridges in the keratinization of the lingual epithelial cells.

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Occulusal fissures of newly erupted teeth are well known as susceptible sites for dental caries. The rate of fissure caries, however, rapidly decrease as the teeth grow older.
For elucidation of the above phenomena, the fissure of upper premolars from 8 to 75 year olds, noncarious to the naked eye, were investigated by means of microradiography, transmitted light with differential interference contrast, scanning electron microscopy and energy dispersive X-ray microanalysis.
It is known that fissures are unsusceptible against caries caused by morphology and hardly by flat occulusal surfaces and calcification. Morphology of caries unsusceptible fissures in old premolars is not wide and shallow V-shaped but rather narrow and deep IU (slit) and IK (kolben) shaped. The reason is that most of these old fissures have native selants composed of dental calculi., which are apt to attach the entrance of the narrow fissures and soon seal them. Moreover they are hard to remove owing themselves to to the difficulty of cleaning.
Old fissure enamel frequently have prismless enamel on the surfaces and minute decalcified zones on the subsurfaces. Hence, it is considered that the prismless enamel is effective in delaying incipient caries when decalcified zones appear. If the calculus selants are formed during the delay, decalcification may cease to advance and in some cases recalcification may occur.

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In order to elucidate morphological change of pulpal nerves with the advance of age, the distribution, organization and ultrastructure of pulpal nerves in the intact permanent teeth extracted from human 8 to 60 years of age were neurohistologically investigated.
The increase of distribution density of nerves in the pulp core, subodontoblastic nerve plexus and pulpodentinal border zone and the irregularity of pattern of coursing predentinal nerve fibers were indicated as the change of pulpal nerves with advancing years. Whereas, the following findings were not changed with avdancing years: that all sensory nerve fibers terminate as a free nerve ending, that nerve fibers in the pulpodentinal border zone are classified into four types (I-IV type), that the ending of nerve fibers distributed in the predentin and innermost layer of dentin selectively contacts with odontoblast processes, and forms a special organization or “mechanoreceptive complex” for the reception of dentin sensitivity, that the external boundary of dentinal innervation is less than 100μm behind the odontoblast-predentinal border.
Especially the increase of distribution density of pulpal nerves was remarkable till 20-30 years old, this would suggest that the development of pulpal nerves which was initiated at the early stage of tooth germ has continued till such a period. The increase of nerve fibers in the pulpodentinal border zone, which would play a leading part in the reception of dentin sensitivity, supposes that the susceptibility of dentin sensitivity might be also changed with the advance of age.

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The dissected incisor tooth germ in the mandible of a Wistar male rat, weighing 100-120g, was cultured in a medium consisting of Ham F12 supplemented with 10 per cent fetal calf serum, 100μ/ml penicillin and 100μg/ml streptomycin. The explants placed on cover glass and epoxy resin slide were cultivated in a humidified incubator at an atmosphere of 5% CO₂ in air and closed system at 37°C.
The outgrowing cells were star-shaped and migrated in a pavement-like pattern, not separately. The cells were a mixed population of mesenchymal cells and epithelial cells originating from the incisor tooth germ. After one week of cultivation, a keratinized cell was observed by staining with Papanicolaou. A nest of epithelial cells was seen in the monolayer cell sheet after 3 weeks of cultivation, which enlarged gradually, but it shrank at 3 weeks after their fisrt appearance. Ultrastructually, mesenchymal cells during their early stage of cultivation were similar to undifferentiated fibroblast of the dental papilla of rat in vivo. They were characterized by a large ovoid nucleus, mitochondria rER, lysosome, small oil drops and several cytoplasmic processes. At a later stage, the mesenchymalcell was flattened on the glass surface, and included microfilament and 10 nm filament. The cultured epithelial cell included relatively more tonofilament than odontogenic epithelial cell of the tooth germ in vivo.
The present method seems to be useful as a experimental system for analysis of the cellular function of fibroblast originating from dental papilla.

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Using Wistar rats from 14 days to 20 days in gestation, we observed the three dimensional growth rate of the lower incisor tooth, through measurement by microphotographs and wax reconstruction of the tooth germs.
The average Crown-rump length increased 10.1mm in a 14-day fetus to 37.8mm in 20 days.The rate of the antero-posterior length growth of the lower incisor increased 223.0-Em in a 15-day fetus to 3240.0μm in 20 days. The crescentic enamel organ was nearly formed completely at 18 days of gestation.

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Oral Treponema, a gram-negative, motile microbe and endogenous to the human oral cavity is one of the predominant microorganisms in the periodontal pockets. In cell-free extracts prepared from this microbe, acid phosphatase with high optimal temperature was detected.
In this report, the partial purification and characterization of acid phosphatase from oral Treponema sp. S-173 were studied.
The enzyme was stable at neutral pH and low temperature region but catalyzed optimally the hydrolysis of p-nitrophenylphosphate to p-nitrophenol and to ortho-phosphate at pH 4.5 and 50°C. Menten-Michaelis constant was 4×10^-3 M in regard to p-nitrophenylphosphate. Oral treponemal acid phosphatase was accelerated by Mg²⁺ (optimal final concentration: 8×10^-4 M) and the enzyme activity was reduced by Hg²⁺by means of competitive inhibition.

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