The structural characteristic aspects of the masticatory muscle spindles in the pangolin were investigated electron microscopically. The results obtained were as follows:
1 . Each muscle spindle consists of a thin outer capsule and intrafusal muscle fibers ranging from one to seven in number and occupied by abundant collagenous fibrils.
2. The outer capsule consists usually of two lamellated capsule cells and sometimes of more than two, that is, four at the neuro-vascular passage.
3. The periaxial lymphatic space is very wide, being occupied by many blood capillaries, myelinated nerve fibers and abundant collagenous fibrils.
4. The inner capsule consists of one lamellated cell, being devoid of the basement membrane and continuous with the innermost layer of the outer capsule. This cell envelopes each of the intrafusal muscle fibers with its branched cytoplasmic processes, by which the intraaxial space is subdivided into compartments, one for each muscle.
5. The intrafusal muscle fibers showed an undulated contour. Beneath the sarcolemma were found specific laminated structures, elaborate membranous networks of the T. system and elaborate sarcoplasmic processes having glycogen-like granules and projecting into the caverns packed with homogeneous filaments. These structures may be of reductive products following the disuse atrophy of the masticatory muscle resulting from the poor jaw movement.
6. Many satellite cells were seen, some of which appeared to anchor two adjacent intrafusal muscle fibers.
7. The sensory terminals were classified into the annulospiral (primary) type and the flower-spray (secondary) one, the former being smaller in number and size than usual and the latter being dominant. The sensory cross-terminals are found to be frequent.
8. The gamma motor end-plate was seen near the polar region of the intrafusal muscle fibers.
9. Blood capillaries enter the periaxial lymphatic space through the spindle capsule to reach the axial space. Some of them enter the periaxial space through the polar aperture of the capsule.
In summary of the results mentioned above, it can be emphasized that the masticatory muscle spindles of the pangolin showed a tendency of atrophy. In other words, they still retain the traces of their youthful features (their early stage of development) . This phenomenon would be highly relative to the undeveloped masticatory mechanism in the pangolin.

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[in Japanese]

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In this study, an attempt was made to evaluate the effect of training on the dental students in the health centers. The subjects used in this research were 82 fourth year students of Tokyo Medical and Dental University. A group of 3-5 students visited one of the three health centers and they gave health counseling, dental examination and dental health education of the infants (1-3 years of age) with their mothers.
The assessment was obtained by means of reporting their random thoughts and impressions just after the training. The students' random thoughts and impressions were made on the following items: 1) The activities in public health and preventive medicine, 2) mothers and infants, 3) the students themselves, 4) the staff of the health center, 5) the functions and equipments of the health center, 6) activities of the health center, 7) science of dentistry and dentist and 8) miscellaneous.
Through this training, the students seemed to develop a greater change in their opinions toward the outgoing community involvement and to giving positive regard to the patients as a person.

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The fissures of the rat molars were examined by the SEM technique with the purpose of demonstrating the change in the bacterial colonization according to the period of tooth eruption. The bacteria began to adhere to the entrance of the fissures as soon as the molars appear in the oral cavity and the colonization extended up to the deeper places of the fissures with eruption.
At the completion of eruption, the bacteria were observed at the lower part of the fissure. Only a slight difference was found in the formation ofthe bacterial plaque in the fissures when the rats were given different diets.
Extracellular polysaccharide was observed in the fissures of rats provided with diet containing sucrose.

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The sialogram expresses the stage of salivary gland disease by the image of the duct system produced by an X-ray contrast medium. To understand the relationship between the stages of salivary gland diseases and the X-ray signs of sialograms, an investigation was made on the microradiograms of the mouse parotid glands with reduced saliva-excretion function.
The microradiograms of the mouse parotid glands were analyzed in three groups of male mice; mice with the major excretory duct ligated, newborn mice and senile mice. The excised parotid glands werephotographed by microradiography of the glands infused with an X-ray contrast medium. Theresults were as follows. First, the microradiograms of duct-ligated parotid glands revealed a dilatation of the ducts, contrast medium leakage from the ducts and gland destruction. Second, the microradiograms of newborn mouse parotid glands showed fewer ducts, which were mostly due to a lower capacity of the ducts for contrast medium infiltration. Third, the microradiograms of senile mouse parotid glands showed fewer ducts and partial destruction of the gland. Thus, these results indicated that the microradiograms showed glands with reduced saliva-excreting functionas the signs of fewer ducts, dilatation, contrast medium leakage from the ducts and gland destruction.
It was concluded that these signs of the microradiogram may appear in the order as described above with the progression of mouse parotid gland diseases and that a similar relationship may exist in the clinical sialogram.

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The five-week progressive changes in the canine displacement in two directions of bucco-lingual and axial and the masticatory movement during gum chewing in the frontal plane were measured using a non-contact sensor system and SAPHONVISI-TRAINER on six subjects with the lingual incline of the canine by overlay ten degrees steeper. The displacement of the canine in the bucco-apex direction was almost straight loading from the lingual side. In five of the six subjects, the length of the outward path gradually increased with time after the overlay insertion, reaching the peak in 1 or 2 weeks, and after the overlay removal returned to almost the same value as before the overlay insertion. The progressive changes in the horizontal width of the intercuspal position showed a contrary tendency. Statistically, a close correlation between the canine displacement and the chewing cycle was found.

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The purpose of this study was to examine the propriety of the application of the computed tomography (CT) to clinical orthodontics.
The following three items were quantitatively tested by using the CT-images of the models, consisting of acrylic sticks and water, simulating the dental roots in the alveolar bone.
1) Spacial resolving power
1. As the X-ray-tube current or the slice width increased, the resolving power increased slightly.
2. The shape or size of the acrylic sticks, made a difference in the resolving power.
3. The maximum resolving power was 0.5mm.
2) Accuracy of linear mesurements
1. As the X-ray-tube current or the slice width increased, the absolute errors tended to decrease.
2. The shape of the acrylic sticks made a difference in the absolute errors.
3. As the diameter size of the acrylic sticks decreased, the relative errors became larger.
4. Under some conditions, the maximum absolute errors were within 0.5mm.
3) Accuracy of angular mesurements
At various angles, the absolute error was within 1 degree.
These findings suggested basically that the CT was sufficiently useful for the orthodontic morphometrical evaluation of the dento-craniofacial associations.

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For the purpose of investigating the tissue reaction of the sutural site stimulated by about 6O-70μm tensions in width, produced by the orthodontic rapid expansion screw, the following organ culture called the hanging technique was performed using the parietal bones including the interparietal suture of 1-day old wistar strain albino rats. The bones were incubated in the natural media containing 75% horse serum and 25% chick embryo extract and gassed with 95% O₂-5% CO₂. After the period of the culture these tissues were observed histologically both O by light and electron microscopes.
The results were as follows:
1) The tensile stimulus changed not only the growth direction of the bone but also the depository site of the immature bone-like tissue.
2) Judging from the electron microscopic observations, this organ culture system can be useful in clarifying the initial response induced by the one or two-day culture of the interparietal suture expanded by the tensile stimulus.
3) It was strongly suggested that the initial calcification mechanism of the immature bone -like tissue on the extended collagen fibers in this study may depend upon the matrix vesicles because of the observations of the particles like the matrix vesicles in the tension group.

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