The levels of mutans streptococci in saliva and dental plaque were determined by the MUCOUNT^TM and latex agglutination tests (LA test) for mutans streptococci in 391 children aged 3 to 6 living in three areas of China, i. e. Beijing, Leshan and Hong Kong, with 0.29 ppm,0.17 ppm and 0.56 ppm of fluoride concentration in the water, respectively. MUCOUNT^TM (Showa Yakuhin Kako Co., LTD, Tokyo, Japan) estimates colonies grown in mitis-salivarius-bacitracin broth selective for mutans streptococci and determines the level of mutans streptococci in saliva. The LA test detects and quantifies the serotype specific polysaccharide antigen of mutans streptococci in dental plaque and determines the level of mutans strepto-713714cocci in the plaque.
It was found that children in Beijing with low fluoride concentration in the water have the highest caries activity among the three areas with concomitant high caries prevalence and high levels of mutans streptococci in saliva and plaque. On the other hand, children in Hong Kong, a community with water fluoridation, have the lowest caries prevalence and caries activity.
The MUCOUNT and the LA test were compared to examine their respective validity as a caries-activity test in relation to caries prevalence. The results of the LA test correlated more strikingly with caries activity, that is, the number of decayed teeth (dt and / or DT) in children aged 3 (P<0.01) and 5-to 6-year-olds (P<0.005) in the low fluoride and high caries prevalent areas (Beijing and Leshan), than did the MUCOUNT (not significant, P<0.05). In the high fluoride and low caries prevalent area (Hong Kong), however, both the MUCOUNT and the LA test were correlated significantly to the caries prevalence in children aged 6-yearolds(P<0.01), P<0.05), although neither test correlated to the caries prevalence in 3-year-old children.
These results suggest that the high fluoride content of the water supply might be effective for reduction of caries activity and that for the evaluation of the level of mutans streptococci in saliva and plaque, either the MUCOUNT or the LA test can serve as a caries-activity test.

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The purpose of this study was to find out factors which determine who brushes the child's teeth, a survey being made with questionnaires.
The subjects were 1127 mothers of nursery and kindergarten pupils ranging from one to six years of age who live in Nagoya and the suburbs.
These data were analyzed by the second class of Hayashi's quantifying theory.
The results of this study were summarized as follows;
1) In the case of children aged from one to three years, there were many children whose teeth ware burshes by their mothers. In the case of children aged from four to six years, there were many children who brushes their teeth themselves without their mother's help.
2) In the case of the children aged from one to three years, the following four factors were chosen which determine the person who brushes the child's teeth; the mother's attitude when the child does not brush, positive attitude toward tooth brushing, use of tooth paste, and the person who actually brushed the child's teeth in the starting peroid.
3) In the case of children aged from four to six years, the following four factors were chosen which determine the person who brushes the child's teeth; cooperation of child with mother's help, mother's attitude when the child does not brush, age, and order of siblings.

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We tested the application of power spectral analysis of the heart rate fluctuation in order to investigate the transition of the autonomic nervous system activity during dental practice in 63 healthy children,5 healthy adults,22 children with congenital heart diseases (CHD) and 15 children with mental retardation (MR).
Electrocardiogram QRS wave forms were recorded on a multichannel FM tape and the R-R intervals were analyzed by the maximum entropy method (MEM), which was one of the methods of power spectral analysis. Consequently, we observed an apparent low frequency peak (LEP: 0.04-0.1 Hz) and a high frequency peak (HFP: 0.2-0.4 Hz), and those peaks varied from pre- to post-local infiltration ansthesia. In healthy and CHD subjects at 3 years of age, those variable patterns of the spectral peaks showed predominantly sympathetic hypertonic patterns, in which only LFP showed, but autonomic stable patterns, in which HFP was shown to be stable, increased more as the children became older. On the other hand, in the MR subjects, even though they were from 7 to 13 years old, no autonomic stable patterns showed, and those patterns were predominantly sympathetic hypertronic patterns as well as those in healthy and CHD subjects at 3years of age.
These results suggested that variable patterns of the R-R interval spectra with local infiltration anesthesia reflects the development of the autonomic nervous system and the maturation of the emotion, and concomitantly that power spectral analysis of the heart rate fluctuation was useful for evaluation of autonomic nervous system activity during dental practice.

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MSB agar was compared with TYCSB agar regarding with the selectivity and the recovery of mutans streptococci from fresh plaque samples in 68 Japanese children 2-10 years old. The yields of freshly isolated strains of mutans streptococci on TYCSB agar were significantly higher than on MSB agar (p<0.05). However, the ratios of the number of mutans streptococci to that of the total microorganisms on TYCSB agar was lower than on MSB agar (p<0.01). Furthermore, extraneous microorganisms were too crowded on TYCSB agar to calculate the number of mutans streptococci in 5 subjects out of the 57 subjects in which mutans streptococci was detected on the MSB agar.
The number of mutans streptococci calculated by MBS agar (p<0.0001) was found to relate more strikingly to the number of decayed tooth surfaces than the number calculated by TYCSB agar (p<0.05).
These results suggest that MSB agar was better in usual practice in. Japanese children to monitor the number of mutans streptococci and to isolate fresh clinical strains of mutans streptococci.

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There have been various reports on dental problems in juvenile diabetic patients, but none has clearly shown how to deal with these children from the point of view of dental care. We performed oral examinations on 62 children with diabetes and investigated how to maintain their dental health.
The results and conclusions were as follows:
1) There was no significant difference in the incidence of dental caries between the patients with diabetes and normal subjects, although some reports have shown a higher rate in diabetic children.
2) There was a tendency for gingivitis to be worse in children in the higher grades of elementary school or in junior high school. Marked deposits of dental plaque and calculus were observed. It thus appears necessary to conduct periodic dental check-ups and to build up a daily self-care routine through dental health guidance and treatment.
3) If possible, annual radiography should be performed to prevent dental caries or chronic inflammation of the jaws associated with oral infections. Juvenile diabetic patients should thus undergo proper dental health guidance and treatment to reduce the physical, mental, and financial burden of dental caries.

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The effect of palatinit on caries induction by mutans streptococci was examined in in vitro and in an experimental caries system, using specific pathogen-free (SPF)Sprague-Dawley rats. Streptococcus mutans MT8148R and Streptococcus sobrinus 6715did not utilize palatinit to produce sufficient acid to demineralize tooth enamel. Palatinit induced no significant dental caries in SPF rats infected with these mutans streptococci.
These results indicate that palatinit is useful as a non-cariogenic sweetener.

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Calcium intake in our country ranks low in the world. Moreover, our presentday diet does not rectify the state of calcium deficiency. At the same time, no report has yet been made on methods for effectively improving debilitated bone tissue.
The authors therefore gave calcium deficient food to three-week-old rats of the Wistar strain and induced a state of bone debility in them. The rats were then given a mixed food of calcium-rich sardine powder and standard food, namely high calcium food, and the effect on bone construction in the mandibular condyle was investigated.
The results were as follows:
1. In the radiological findings, administration of high calcium food resulted in clear osseous layers and an increase in and a regularity of the trabeculae.
2. In the findings from analysis with X-ray micro-analyzer, administration of high calcium food increased both the relative Ca ratio and the relative P ratio, and the values of the calcium-deficient food group and high calcium food group approximated those of the control group.
3. In the histopathological findings, administration of high calcium food showed active findings in the bone formation such as a decrease in width of the cartilagenous layer, an increase in width of the trabecula and an increase in number.
4. In the scanning electron microscopic findings, administration of high calcium showed active formation of the longitudinal matrix and active formation of the trabeculae in the subchondral bone formation zone. When compared with the control group, however, every aspect was still unsatisfactory.
On the basis of the foregoing findings, administration of a mixed food of calcium-rich sardine powder and standard food, namely high calcium food to debelitated bone tissue in the mandibular condyle accelerated the growth of the chondrocyte layer and bone construction in the bone tissue. The state of the restoration however was shown to be insufficient.

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In 432 subjects, analysis was made of erupted teeth according to the kinds of teeth and according to the groups of teeth and of the carious conditions at Hirogamimura, Kitauonuma-gun, Niigata Prefecture during a 9-year-period from 1981 to 1989. In addition, examination was made of the effectiveness of the results of evaruation based on the caries activity test (Cariostat®) at the start of the reuption of the permanent teeth as a mean of prediction of carious conditions kinds of teeth and the groups of teeth. The results were as follows:
1) The kind of tooth eariest susceptible to caries was the mandibular first molar (about 70% suffered from caries 2 years post-eruptively), followed by the maxillary first molar (about 50% suffered from caries 2 years post-eruptively). The second molar showed a similar caries inclination as the first molar.
2) The kind of tooth least susceptible to caries was the mandibular cuspid tooth, followed by the maxillary cuspid tooth and the mandibular incisors.
3) By groups according to time of birth, the group involving later birth showed lower caries-suffering inclination, and this was noted for the first molar, maxillary incisors and bicuspid teeth and especially to a remarkable extent for first molar from three years after eruption on.
4) The results of evaruation by Cariostat at the start of eruption of the permanent teeth and the DMF ratio following eruption of permanent teeth showed a positive correlation concerning the kinds and groups of teeth having a high tendency to suffer from caries and to an especial extent for the mandibular and maxillary first molars. On the other hand, no such correlation was noted concerning the kinds and groups of teeth having a low tendency to suffer from caries. The group of maxillary incisors showed such positive correlation in conncidence with the time-course of caries-suffering condition.
5) The relationship between the results of evaruation by Cariostat at the start of eruption of permanent teeth and D ratio, F ratio following eruption of the permanent teeth showed different aspects according to the kinds and groups 788of teeth, indicating a positive correlation almost in coincidence with the cariestreating condition.
6) Mandibular bicuspid teeth showed an age rerayed tendency to suffering from caries and correlations with DMF ratio, D ratio and F ratio were poor.
7) The above results suggested Cariostat at the start of eruption of permanent teeth to be an effective index of prediction of the aged carious condition of permanent teeth according to the kinds and groups of teeth.

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The present study was designed to discuss the clinical application of the occlusal analyzer“T-Scan system”in the case of children. In the first experiment, the possibility of insertion of the sensor into the mouths of 112 children with primary and/or mixed dentition was examined. Also in order to confirm the accuracy of the representation of the tooth contacts on the T-Scan system clinically, in artificial premature contact,300μm in height, was applied to the teeth which were going to be treated by composite resin, or inlay or steel crowns in 20 children with mixed dentition. Occlusal changes were observed in three sessions; ie, before tooth preparation, before occjusal adjustment and after occlusal adjustment by using two analyzing modes of the T-Scan system; ie, the force snap shot and time analyzing modes. In each analyzing mode, the accuracy was evaluated using three grades; ie, good, relatively good and poor, in accordance with whether the T-Scan system could detect and represent the premature contact or not.
The results obtained in the present study were summarized as follows;
1) The sensor of the system was too large to apply to the children with primary dentition.
2) It was possible to detect occlusal changes accurately in 50% and relatively accuracy in 40% of 20 children by using the system. As far as the results of the present study is concerned, it is suggested that the T-Scan system would be appropriate for examining the occlusal contacts in children with mixed dentition.

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The interest of the present study was focused on a clinical and statistical survey of 191 traumatized teeth of 162 children who had first visited the Pedodontic Clinic of Tohoku University between 1981 and 1990.
The results are summarized as follows.
1) The age distribution of the patients ranged up to 10. The most frequently affected age was 2 years of age.
2) The rate of incidence of the trauma was 6.9 and 4.1 % in the primary dentition period and the mixed dentition period, respectively.
3) The most frequently affected teeth were the upper central incisors in both the primary and permanent teeth. It was also shown that the rate of affected primary upper central incisors was two times higher in the left side than that in the right side.
The following was forcused on a clinical and statistical survey of 367 traumatized teeth of 223 children aged up to 10, who had visited our hospital between 1971 and 1990.
1) The ratios of affected boys and girls was 1.3: 1 for the primary teeth, and was 1: 1 for the permanent teeth, respectively.
2) Most of the affected children visited our hospital within 24 hours of the injury.
3) The most frequently observed cause of trauma was the collision with the primary teeth and striking of the permanent teeth, respectively.
4) The rate of incidence of trauma was 5.8% in the children with normal occlusion and 4.1 % in the children with malocclusion, indicating that there was no difference in the incidence of trauma between the normal occlusion and malocclusions. Among the malocclusions, however, trauma occured still more in the children with horizontal open bite.
5) The types of trauma in the primary teeth were in the order of others, luxation and fracture. The types of trauma in the permanent teeth were in the order of fracture, concussion or displacement and falling out.
6) For the treatment of the primary teeth, observation, extraction and fixation were in the order preferred and the observation, the fixation and the crown restoration for the permanent teeth.

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The purpose of this study was to investigate the cavity form for the conposite resin in the deciduous molars.
The materials were 57 buccolingually continuous nondcacicified ground specimens which were made from 15 lower second deciduous molars with composite resin restoration, having shown good progress up to the exchange of the successive permanent teeth.
The relationship between the cavity floor and the enamel-dentin junction was was examined and the distance from the cavity to the pulp chamber was measured.
The results were as follows:
1. The cases in which the cavity floor was in the enamel came to 5 of 15 teeth (33%). This ratio was smaller in comparison with that of the upper second deciduous molars (75%).
2. The obervation area in which the cavity floor was frequently in the enamel was in the center of the tooth (40.0%).
3. The minimum distance from the cavity to the pulp chamber was 1.12∼27mm at the mesio-buccal and lingual horn of the pulp chamber. The maximum distances were 2.11∼2.17 mm at the central fossa. The distance from the cavity to the pulp chamber was 1.12∼2.17 mm in all of the cavities.
4. The distance from the cavity to the pulp chamber tended to be shorter at the mesial and distal sides than at the center sides.

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The developmental change in the occlusal contacts is one of the very important aspects in clarifying the development of occlusal functions in children.
In the present study, the number, the area of occlusal contacts, and the degree of bite force were investigated in children from Hellman's dental stage II A to III B with use of the pressure detecting sheets called“Occlusal Prescale”. The results were as follows:
1. The number of occlusal contacts at the molar region was 4.7 in II A,8.2 in II C,6.8 in III A and 6.1 in III B.
2. The area of occlusal contacts at the molar region was 1.31 mm² in II A,3.35mm² in II C,2.43 mm² in III A, and 3.66 mm² in III B.
3. The degree of bite force at the molar region was 68.6N in II A,172.4N in II C,130.3N in III A, and 200.9N in III B.
It was also indicated that the first molar began to play an important role in occlusal contacts just after their eruption. The primary molars also filled in important function concerning occlusai contacts, and that the aspects of occlusal contacts at the molar region could be different from time to time due to the development of the dentition.

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The purpose of this study was to examine the experience of the operator and a method of cleaning for pits and fissures which have an influence on the effects of pit and fissure sealant. This study was performed by clinical evaluation of pit and fissure sealant after two years. It was examined that the relationship among the change in the result of pit and fissure sealant, the change in the method of cleaning of pit and fissure, the experience of the operators. The results obtained were as follows;
1. The retension rate of the sealant became higher after the change in cleaning method than before. Especially the inexperienced operators improved with the change in cleaning methods.
2. There is no difference in the retension rate of the sealant among the four first permanent teeth, maxillary right, maxillary left, mandibular right, mandibular left. The retension of the sealant improved with the change in cleaning method, especially in the bilateral maxillary first molars.
3. The retension rate of the sealant is related to the clinical experience periods of the operators.
4. All of the results related to the improvement of the retension rate were affected by the presence of some unskilled operators.

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The aims of this study were to present a new quantitative method for evaluation of condyle and disk movement with respect to opening and closing mouth movements by MRI, and to evaluate condyle and disk movement in the TMJ patients in comparison with normal adults by using a new method.
The subjects of this study were seven normal people (N group) and seven anterior disk dysplacement (ADD) patients with reduction (T1 group) and eight ADD patients without reduction (T2 group). The following results were obtained.
1. The reproducibility of expression by the XY coordinates for condyle and disk movement by this new method was found.
2. In the N group, the amount of horizontal movement change was large in the following order, condyle>the front point of disk>the back point of disk.
3. The movement of the condyle and disk was different among the three groups.

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Lateral slow expansion is often applied as an initial treatment for maxillary constriction and offers good prognosis. The purpose of this study was to examine the effect on interdental widths, concurrent with slow maxillary expansion in mixed dentitions.
Nineteen Japanese children were selected for the present study. The sample included 10 females and 9 males. The average age of the entire sample was 8.6years. After complete records for orthodontic treatment including dental casts were taken, a removable split-acrylic appliance with an expansion screw was fitted to each patient. Activation of the appliance was initiated one week after the placement. By turning the screw 90° once a week, the appliance was expanded laterally by 0.2 mm per week. Dental casts were taken again after more than 3 months from the start of the activation. Interdental widths were measured between the mesiolingual cusps of opposing molars and between the tips of the primary canines with automatic calipers (Mitsutoyo, Tokyo) to an accuracy of 0.1 mm. Changes in the interprimary canine, interprimary first molar, interprimary second molar, and interfirst molar widths of the maxilla and mandible were calculated by measuring them on the pre- and posttreatment dental casts. Each change obtained in the present study was compared with corresponding estimated growth derived from average changes of interdental widths in 128 normal Japanese children from 6 to 13 years of age studied by Ootubo.
There were significant differences between the changes and corresponding estimated growths in all the maxillary interdental widths (Wilcoxon signed-rank test; p<0.01). Furthermore there were significant differences between the changes and corresponding estimated growths in the mandibular interprimary second molar and interfirst molar widths(Wilcoxon signed-rank test; p<0.002). In the mandibular interprimary canine and interprimary first molar, however, there were no significant differences between the changes and corresponding estimated growths.
The results suggest that perhaps primary second molars and first permanent molars have enough area to produce sufficient force to maintain the antagonists upright. As for primary canines and primary first molars, contact areas where the occlusal forces are exerted are so small that significant occlusal forces may not be applied to the lower teeth, and hence have no impact on their alignment.

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The purpose of this study was to ascertain the caries control effect of oxofluoromolybdate {(NH₄)₂MoO₂F₄} in clinical pediatric dentistry.
10% (NH₄)₂MoO₂F₄ solution was applied as a tooth surface application and investigated.
The subjects consisted of 26 children who visited the pediatric dental clinic of Iwate Medical University and involved 48 deciduous teeth. The following results obtained:
1) As to the labial (buccal) surface caries, on investigation of the area change of the caries lesion, it was found that the efficiency rate of the subject teeth was 62.1% and had significant differences (p<0.05).
2) As to the proximal surface caries of the deciduous molar, based on X-ray photographs, it was found that the efficiency rate of the subject teeth was 93.8%. It seemed that compared with the control teeth (75.0%), it did not show any significant differences but was efficient.
3) It was found that no cases showed reaction to pulp and discoloration of the teeth.
4) 10% (NH₄)₂MoO₂F₄ solution can be applied as a caries control medicine clinically.

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