The ultrastructural changes in the terminal secretory units of the labial salivary glands, in which was demonstrated light microscopically the characteristic appearance of Sjogren's syndrome, were investigated in 12 cases. A small number of lymphocytes appeared interspersed in the dilated interepithelial spaces. Acinar cells showed regressive changes of various degrees, i. e. in the mature acinar cells the secretory granules were irregularly shaped and often found fused to each other while the intracytoplasmic organellae were swollen and destroyed in the immature acinar cells. These findings suggested that both the productive and secretory processes of the secretory granules in the acinar cells were disturbed. And finally the acinar cells appeared completely destroyed and their whole intracytoplasmic contents spilled into the acinar lumen. In some of the terminal units which consisted of immature acinar cells, the acinar cells were arranged irregularly and showed a syncytial appearance. This finding might suggest the socalled tubular metaplasia or canalicular regression. There was no regenerative appearance of the acinar cells. The myoepithelial cells, located in the basal portion of the acinar cells, were more resistant to the inflammatory changes than the acinar cells, however, pyknosis of the cytoplasm, formation of many thin cytoplasmic processes and increase in the number of pinocytotic vesiclae were found in the advanced stage. There were no proliferative changes in the myoepithelial cells.

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The synaptic basis of the efferent discharge in the digastric nerveevoked by the stimulation of the cortical masticatory area (orbital gyrus) was analyzed firstof all by the intracellular recording from the anterior digastric motoneurons in the cats anesthetized with α-chloralose. Secondly, the role of the bulbar reticular formation in this cortical effect was studied by the transection of the brain stem at the level of the rostral border ofthe medulla oblongata. Thirdly, the synaptic mechanism responsible for the reversal of the orbital cortical effect on the masseteric monosynaptic reflex from depression to facilitation by the ponto-bulbar brain stem transection was analyzed by the intracellular recording from the jaw closer motoneurons. The following results were obtained: 1) Before the brain stem transection, the orbital cortical stimulation evoked excitatory postsynaptic potentials (EPSPs) in the anterior digastric motoneurons with a latency that was longer by one synaptic delay than that of the spike potentials evoked by the orbital cortical stimulation in the medial bulbar reticular neuronsforming direct excitatory synaptic linkages with the anterior digastric motoneurons. After the brain stem transection, the cortically evoked EPSPs were virtually abolished, but no inhibitory postsynaptic potential was revealed. Thus, the abolition of the cortically evoked efferentdigastric nerve discharge after the brain stem transection was due to the drastic reduction or even complete loss of the EPSPs (disfacilitation) in stead of the active inhibition of the anterior digastric motoneurons. 2) After the brain stem transection, stimulation of the orbital gyrus evoked EPSPs in the jaw closer motoneurons, indicating that the facilitation of the masseteric reflex was due to the EPSPs instead of the disinhibition of the jaw closer motoneurons.
It was concluded that the orbital cortical excitatory effect on theanterior digastric motoneurons was mediated by the bulbar reticular formation, and the excitatory premotor neurons involved in this cortical effect were virtually all located in the bulbar reticular formation, while the excitatory premotor neurons projecting to the jaw closer motoneurons were located rostrally to the medulla oblongata.

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The purpose of this study was to observe the pathological changes in the exposed pulp in the germ-free Wistar rats compared with those in the conventional rats.
Pulp tissues of the rats were exposed with No. 19 carborundum point or No. 1/2 round bur and the exposures were left unsealed. In order to study the growth of the newly produced calcified tissues, the rats were injected intraperitoneally every 5 days with an aqueous solution of lead disodium ethylene diamine tetraacetate. The animals were sacrificed at 14 and 28 days after the pulp exposure.
The results obtained were as follows:
1. In the pulp tissues of the conventional rats, a high percentage of extensive necrosis and inflammatory cell infiltration was observed and even periapical abscess was recognized frequently. Dentine bridge formation was not seen.
2. In the pulp tissues of the germ-free rats, although odontoblast disturbance, proliferation of fibroblasts and slight infiltration of the inflammatory cells were observed, dentine bridge formation occurred in 30 per cent of the teeth in 14 days and 57 per cent in 28 days after the pulp exposure.
The lead lines by the time-marking method, however, were not clearly seen in the dentine bridge.
3. Pulp tissues exposed with a round bur were more damaged than those exposed with a carborundum point in both the conventional and germ-free rats.
4. There was no apparent difference between the histologic changes of the injured pulp tissues in the 8 to 11-week-old germ-free rats and those in the 29-week-old rats.

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Human saliva is supersaturated with respect to calcium phosphate. In order to detect the factor which stabilizes this supersaturated condition, a new assay system was developed. This system measures the ability of the saliva and its components to inhibit calcium phosphate precipitation by monitoring the turbidity on the Sienco Aggregation Meter. By this method, the inhibitory activities of the human parotid saliva in 12 individual were examined and the inhibition rate ranged from 10% to 90%.
The proteins which inhibit calcium phosphate precipitation were isolated from the human parotid saliva as well as from the submandibular-sublingual saliva by sequential chromatography on Sephadex G50, DEAE-cellulose and phospho-cellulose. The amino acid compositions of these two proteins were characterized by the high content of glutamic acid, proline and glycine but lacked methionine and tyrosine. These compositions were similar to that of protein C (Bennick & Connell, 1971).
It was also found that these proteins showed affinity for hydroxyapatite as revealed by hydroxyapatite column chromatography. From the above results, it was suggested that these proteins might be involved in the inhibition of dental calculus deposition and at the same time in the formation of the acquired pellicle.

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For the one hundred and four decayed permanent molars in the mouth, classes I and II, MOD and proximal cavities were prepared with the minimum necessary reduction based on the biological approach. These preparations were restored ramdomly by four adhesive composite resins for posterior use: Bellfirm P, Clearfil posterior, P-10 and Microrest. The restorations were initially evaluated as the baseline at the time of the subsequent appointment for finishing and polishing, and, thereafter, reexamined at six-month intervals.
The occlusal replicas of the restorations were observed also serially with SEM for examining the wear pattern. The following findings were obtained:
1) By the baseline examination, the sensitivity to cold water was observed in 21 per cent of the restorations. Most of them disappeared gradually with time except in only one case which needed an endodontic treatment.
2) Marginal fractures of the restorations were observed in 9 cases at six months. These fractures were found mainly in the margin located on the functional cusp. Also, the average marginal angle of the fractured portions was 48.. and the maximum angle was 67...
3) The four resins showed clinically no evidence of occlusal wear after six months to one year. SEM observation, however, revealed a minimum roughening of the resin surfaces with time.
4) Some patients had complained of occlusal pain due to the premature contact at the time of the baseline examination, and some cases of Bellfirm P restorations had been discolored peculiarly to light brown.

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Pressures being exerted on the buccal and lingual surfaces of the first lower molar from the surrounding cheek and tongue during various mouth functions were investigated to make clear the functionally acceptable buccal-lingual position of the artificial posteriors in a complete denture.
Five subjects who were missing only their first lower molars participated in this study and the pressures were recorded by miniature pressure sensors placed on both the buccal and lingual surface at the area where the teeth are missing. Two kinds of movements consisting of the specially conditioned and swallowing were selected from the various mouth functions in this report. Pulling their mouth corners backward by themselves, intentional occlusion, thrusting their lips, thumb-sucking and mandibular lateral movement were included in the former. The findings were as follows;
1. A distinct high value of pressures was obtained on the buccal surface by pulling their mouth corners backward and by intentional occlusion 1 (maximal biting) . On the other hand, a slight pressure was recorded on both surfaces by thrusting their lips, intentional occlusion 2 and mandibular lateral movement, and also on the lingual surface by pulling their mouth corners backward.
However, variations in the pressure values recorded among the subjects were recognized, and not only positive but also negative values were indicated on the lingual surface by thumb-sucking.
2. High pressure values and time-pressure integrals were obtained by swallowing, and the value of pressure by empty swallowing was higher than by water swallowing. Moreover, pressures recorded on the lingual surface by swallowing were often greater than on the buccal surface.

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In order to define the biological significance of the double innervation in the tooth pulp, architectonic observations of the pulpal nerves were made electron microscopically on the teeth of the tupaias, monkeys and rats. The results obtained are as follows: 1. The architectonic features of the pulpal nerves are similar to each other in the teeth of the tupaia and monkey and rat molars, consisting of many myelinated fibers and some unmyelinated fibers. 2. They have no special anatomical relation to the blood vessels. 3. In the apical pulp of the constantly growing rat incisor, all of the nerve fibers are unmyelinated, and they were classified into the polyaxonal and monoaxonal fibers. 4. In the upper part of the incisor pulp the nerve fibers were classified into the myelinated monoaxonal and unmyelinated polyaxonal fibers. 5. In the denervated pulp it was shown that the monoaxonal unmyelinated and the myelinated fibers are derived from the trigeminal ganglion cells and the polyaxonal unmyelinated fibers from the cervical sympathetic ganglion cells. 6. The biological significance of the double innervation of the pulp was discussed: the sympathetic nerve may act as an inhibitor of the aging of pulp and the trigeminal nerve as the excitor of the dentine formation as well as the conveyor of the pulpal sensation.

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