A ready made metal crown and a crown distal shoe have been widely used in clinical pedodontics. These alloys are composed of nickel, cobalt and chromium. We have studied the cytotoxity in vitro which bring about these metallic ions.
The cell line, which was derived from the human gingival fibroblast, has been used and these cells were grown in Eagle's MEM with 10% calf serum in a humidified atmosphere of air with 95% of CO₂ gas fusion at 37°C. The effect of these metalic ions was tested and the results were as follows: Ni: 12.5μg/ml-50.0μg/ml, Co: 6.25μg/ml-25.0μg/ml, Cr: 0.1μg/ml-1.0μg/ml. Fibroblasts were cultivated at a density of 8×10⁴ cells/ml in the culture media without metallic ions, and were incubated for 24 hours. Then, the culture media was replaced by a fresh media, containing either one of Ni, Co and Cr ions. The number of viable cells were calculated every 24 hours for the following six days, and the morphological changes of the cultivating cells were studied with a light microscope. This study showed that each metalic ion had induced similar morphological changes of the cells, and inhibited the cell growth rate. The concentrations of each metallic ion which inhibited cell growth were estimated between 12.5μg/ml and 25.0μg/ml for Ni, about 6.25μg/ml for Co, and between 0.1μg/ml and 0.5μg/ml for Cr. These results suggested that the level of cytotoxic effects were on the order of Cr, Co and Ni.

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The purpose of the present study was to evaluate the maturation of the neuromuscular system of masticatory muscles in children. For this purpose, the examination of the stretch reflex of masseter muscles known as one type of masticatory muscle reflex, and the subsequently occuring silent period were made. In addition, the effects of muscle activities on the duration of the silent period were also discussed.
A total of 25 subjects: 1) 10 children (mean age,6y 2m), all with sound dentitions and functionally normal occlusions (designated as the CN group); 2) 10 adults (mean age,21.1y), with functionally normal occlusion and without any stomatognathic system disorder as well (designated as the AN group); and 3) 5 adults (mean age,27.2y), whose bite forces are very poor (designated as the AS group).
Stretch reflex was induced by applying chin taps with constant strength at the following positions; 1) the rest position representing voluntary isometric contraction of the muscles,2) the clenching (the maximum clenching ad libitum that the subject could maintain 10% and 50% levels respectively),3) the biting of occlusal force meter (5 kg,10 kg and Max. B., the maximum bite ad libitum respectively). The recording of muscle activities were obtained using surface electrodes applied on the bilateral masseter muscles.
The results obtained in the present study were outlined as follows:
1) The latency of the stretch reflex was shown to be longer in the rest position than at any level of clenching and biting in all groups when comparing the three groups, the latency of the CN group was shown to be longer than other two groups.
2) With the increase of muscle activities, the duration of the silent period significantly descreased. This was noted both in the CN and AN groups as well, whereas no significant change was recognized in the AS group.
3) As far as the duration of the silent period is concerned, it was the shortest in AN group, and followed by the CN, and the AS group at maximum biting.
The results obtained in the present study suggest that the growth and development of the masticatory muscles could affect the duration of silent period, in other words, the silent period was possitively influenced by the activities of masticatory muscle.

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The purpose of the present study was to disclose information on the course of malocclusion and the possible effect of the eruption sequency of lateral teeth on the formation of malocclusion of the permanent dentition.
A total 160 school children,88 boys and 72 girls who started their first year of primary school in Kagamihara city, Gifu Prefecture in 1980 were examined. The examination was subsequently carried out until 1986. Of these,48 children had to be excluded, because they had changed their school during the period of the present survey. Adhering to the registration method by Bjork et al, the Dental Stage (DS) which describes the steps in dental development, its chronological incidence, and the eruption rate of permanent teeth, the numbers and incidence of different types of malocclusion, and the sequence of eruption of lateral teeth were recorded.
The results obtained in the present study were as follows:
1) There was tendency towards a increase in maxillary protrusion, distocclusion of the first molar, deep overbite, inversion, scissors bite and crowding of the lower anterior teeth.
2) Lower anterior protrusion, open bite, scissors bite of molars and crowding of lower anterior teeth were declining.
3) Anterior protrusion is often observed in cases where the eruption sequece was 4→3→5,3·4→5 or 4→3→5 and an overbite in 4→3·5.
As far as the results obtained are concerned, it may be suggested that the eruption sequence of the lateral teeth may be related to the some types of malocclusion. Furthermore, the logitudinal survey provides the information pertinent to follow the course of the malocclusion.

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Since it is considered that caries susceptibility depends on enamel maturation such as mineralization, cristallization or decrease of organic substances in the tooth enamel, studies were conducted to discover the mechanisms of the posteruptive maturation. As the first step, changes and interrelationships among representative mineral (Ca, P. CO₃, and F) concentration, crystallinity and organic components in bovine teeth enamel were examined.
The following results were obtained:
1. During the stage of amelogenesis, great increases of calcium and phosphorus concentrations in the enamel powder were observed, while carbonate, fluoride and organic substances showed a marked decrease in the same specimen. The crystallinity of hydroxyapatite, crystal growth in the a-axis direction increased but in the caxis direction was almost complete, at that time.
2. In the early stage of root formation, the concentrations of calcium and phosphorus were still increasing. However, the rates of their increase in this stage were lower than in the stage of amelogenesis. Also, there was no change in the concentrations of carbonate and fluoride. The crystal growth in the a-axis direction or the decrease of organic substances in the enamel powder was found to he at the same rate as in the first stage.
3. In the late stage of root formation, there was no change in the concentrations of the constituents and the crystal growth.
4. During the stage of tooth eruption, concentrations of calcium and phosphorus increased while those of the carbonate and organic substances decreased. Both of those changes were less than in the stage of amelogenesis.

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At the dental clinic of the Department of Pedodontics, School of Dentistry, Tokushima University, the relationship between the behavioral reactions of children and their personality factors were evaluated in 32 three-to-seven-year old children. The personality factors were evaluated with the “Young Children's Social Development Test”, “Matching Test” and “Children's Concepts of Dental Clinic, Operations, and Illness”. The results are summarized as follows:
1. The children who showed a cooperative behavior in the dental chair also showed a higher degree of social development in the field of “ Exercise·Safety ” and “ Behavior in the Masses ” than the children who showed an uncooperative behavior in the dental chair.
2. Reflection-impulsivity tested with the “ Matching Test ” did not correlate to the adaptability to dental treatment.
3. The consciousness of the children toward dental health did not correlate to the adaptability to dental treatment but the ability to tolerate did.

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The purpose of this investigation was to evaluate cephalometrically the mechanisms of class II malocclusion cases treated with a Bionator for a period of 20 to 24 months. Before treatment and after treatment skull films of centric occlusion were analyzed.
The results were as follows.
1) The cephalometric findings after treatment showed a favorable relationship between the results of the skeletal and dental changes.
2) The changes with skeletal and dental problems which contributed to class II malocculusion resulted in a lingual improvement of the incisor.
3) There were 2 directions of mandibular growth using a Bionator. One was a downward movement and the other was a downward and forward movement.

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In 1940 Ellis and van Creveld described three infants with this disorder. The Ellis-van Creveld syndrome is characterized by polydactly, ectodermal dysplasia and congenital cardiac defects.
The patients were monozygotic twin sisters,3 years of age. As far as their family history is concerned, there were no congenital malformations in the case of the parents and relatives. No contributory event was noted during the course of pregnancy. Dental examination showed that the superior right deciduous central incisor was missing only in the case of the elder sister. There were many severe caries present. Calcification of the deciduous teeth seemed to be complete. The developing buds of the permanent teeth were present and development would seem to be normal for a child of this age. The upper and lower lips were not connected to the gingiva with frenula except in the case of the labium frenum of the younger sister. Further studies based on accumulated cases will be necessary.

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The purpose of the “ Mother Class ” in Pedodontics is to make the parents understand the meaning of pedodontic treatment and the importance of children's oral health care over long periods of time. To make the "Mother Class" produce results, the mothers of children who visited at the Department of Pedodontics, School of Dentistry, Tokushima University from October 1977to December 1986 were asked about their knowledge of oral health care.
The results are summarized as follows:
1. During last ten years, the chiefcomplaint of dental caries decreased and that of malocclusion increased. There was an increase in the percentage of parents who selected the university hospital because of its specialization in pedodontics, and who expect not only caries treatment but also total oral health care with a recall system.
2. The caries initiation age did not change during the last ten years.
3. There was an increase in the percentage of zero-to-five-year old children who had a habit of brushing their teeth.
4. There was an increase in the percentage of zero-to-five-year old children who had experience in topical application of fluoride.
5. The percentage of parents who had knowledge of the methods of caries prevention increased, but about 35% of parents did not have this knowledge.
6. Only 76.2% of parents had a habit of brushing their teeth regularly.
7. About 30% of the mothers had attended lectures or studied by themselves. The lectures were at the oral health center, the university hospital and the private dental clinics. The means of study included books or television.

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