The time of the eruption of the deciduous and permanent dentition in a total 46,698 Japanese children (23,610 boys 23,088 girls), was examined transversally. The present program was carried out by the staff members of the Department of Pedodontics of all the dental schools in Japan under the sponsorship of the Japanese Association for Dental Science.
Examinations were made, excluding the subjects who had either systemic or local diseases which would possibly have influenced the time of eruption and made the determining of the stage of eruption difficult. The criteria for erupting teeth were; part of the teeth, either the incisal edge or cusp erupt within 1 mm above gingiva. Based on the data statistically determined, the following results were obtained.
1) The Chronology for the diciduous dentition is as shown on Table 2,3.
2) The Chronology for the permanent dentition is as shown on Table 4,5.
3) The rate of the eruption in the deciduous dentition, at one month and six months intervals respectively are shown on Table 6,7.
4) The rate of the eruption in the permanent dentition, at one month and six months intervals are shown on Table 8,9.
5) The most frequent order of the eruption of the deciduous dentition was AB-C-D-E on both the maxilla and mandible.
6) There was no difference according to sex for the time of eruption, except for the lower central incisor, which generally is more advanced in boys than girls.
7) A typical order of the eruption of the permanent dentition was 6-1-2-4-3-5-7-8 in the maxilla, and 1-6-2-3-4-5-7-8 in the mandible.
8) Generally, the teeth of girls erupt slightly earlier than those of boys in the permanent dentition.
9) The Chronological chart of the dentitions developed by Schour,1. Massler M. was modified and presented based on the present data obtained from Japanese children.

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The purpose of this study was to ascertain the masticatory movement in children. A total of 20 normal children from IIA to IIIB according to Hellman's dental age were examined. The mandibular movements studied involved such foods as raisins, chewing-gum, and peanuts and were recorded with the Saphon Visi-Trainer CII.The mastication at each dental age of the children were observed according to classification of the masticatory strokes with each type of food.
The results were as follows:
1. The type of mastication characterized by closing at the working side and opening at the same side was found most frequently (74.8%) with all types.
2. The mastication of children who have primary dentition at IIA (5y6m) was similar to the one in adults.
3. The masticatory pattern for raisins was similar to that for chewing-gum. This pattern concerning both foods in children showed a stability similar to the one in adults.
4. The difference of masticatory patterns between the periods from IIA to IIIA and IIIB was found to be significantry clear. This difference was clearer with raisins than with chewing-gum, but it was not very clear with peanuts.

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The purpose of this study was to investigate the eating functional development.
The subject were 480 healthy one year and six months old children who visited the public Health Center. We sat questionaries about the present state of their mastication, living environment of meals, and the history of weaning prosses and we examined the eruption of decidious tooth of them.
The results obtained were as follows.
1) Almost children can't eat meals by themselves skillfully.
2) There are few children who have meals alone.
3) Over 50% children can't chew their food well.
4) 1/4 children have some kind of problems about the eating function.
5) Children who have functional problems tend to have many likes and dislikes.
6) A lot of parents who cared a hardness or a size of baby food answer that their children can chew their food well.
7) 1st deciduous molars are already erupted with 80% of the children.
8) We think the eruption of 1st deciduous molar is related to the mastication a little.

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The flow ratio of unpolymerized resin monomer, the thickness of the air inhibited layer and the temperature change during the polymerization process for both the auto-activated and photo-activated fissure sealants were measured. Also, several methods for removing unpolymerized resin monomer remaining of the acid etched enamel surface were evaluated.
The following results were obtained.
1. The flow ratio of unpolymerized resin monomer for the photo-activated sealants showed a significantly lower ratio than that of the auto-activated sealants.
2. The thickness of the air inhibited layer of the photo-activated sealants was significantly thinner than that of the auto-activated sealants.
3. Unpolymerized resin monomer remaining on the acid etched enamel surface was able to be removed by either acetone irrigation and scrrubing with a rotating brush, but not by water irrigation.
4. The micro structure of the acid etched enamel was preserved after removal of the unpolymerized resin monomer by means of acetone irrigation, but it was destroyed with brush scrubbing. Conclusion
1. From the standpoint of clinical utilization, the usage of photo-activated sealant is recommended.
2. The insufficiently sealed portion at pits and fissures could be supplemented by adding newly prepared resin after water irrigation and air blast dehydration.
3. When fluoride application is planed for the acid etched enamel surface where it has been covered by unpolymerized resin monomer, it is recommended that removal of resin monomer by means of a rotating brush should be prepared before the application.

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A new visible-light-curing calcium hydroxide product named “Prisma VLC Dycal” (VLC Dycal) was subjected to study. VLC Dycal is the improved type of “Dycal” which is used generally as the pulp capping agent.
The purpose of this study was to examine the physico-chemical quality as well as the dental pulp reaction towards this agent when it was used as the indirect pulp-capping agent. The acid resistance of VLC Dycal was evaluated by applying 60% phosphoric acid to the agent. The physical property of VLC Dycal was also evaluated by measuring the compressive strength of the agent.
The results obtained were as follows:
1) The compressive strength of VLC Dycal was about ten times greater than that of Dycal.
2) The acid resistance of VLC Dycal was remarkably greater than that of Dycal.
3) The pulp response of VLC Dycal was not inferior to that of Dycal.

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The purpose of this study was to elucidate the skull, the dentfacial complex and the dental arch of extremely immature infants and very low birth weight infants, what we call “the face of the immatured infant”, with the objective measuring and analyzing of the craniometric points and the dental arch model.
The materials consisted of plaster models and Roentgen Cephalograms (Lateral and Postero-Anterior) obtained from 20 children (mean age 3yllm) having no problems with their general condition and whose weight at birth was lower than 1500 g. They were treated by the department of pedodontics, school of dentistry, Showa University.
The findings were as follows:
1. The dental arch was generally small, narrow in width and was shown to be almost standard in the U-shaped arch. The height of the palate was almost standard in the anterial part and tended to be shallow in the posterial part.
2. In the Roentgen Cephalogram (lateral), the growth of the dentfacial complex was almost standard based on angular analysis using the craniometric points. But the ramus mandibula was poor analysis of the length showed that the antero-posterial length tended to be long in the braincase, almost standard in the mesofacial part, and small in the mandibulo-facial part. From the measurement of the area of the tubella sella triangle, the growth of the mandibula was poor and the area of the occiput was enlarged. Also the points of the depth of the skull were rather longer than the heights.
3. In the Roentgen Cephalogram (Postero-Anterior), the width of the cranial bone was narrow in each cranial breadth.
The results obtained showed that the morphological characteristics of the skull at the age of 4 years were narrow width, short antero-posterial length, poor growth of the mandibula, and the dental arch were effected.

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The purpose of this study was to compare the objective chromatical values of the primary teeth color of the Japanese children measured with the Murakami Color Research Laboratory Light Guided Color Difference Meter CD-270 using the improved light guide (Improved CD-270), the CD-270 using the CD-270light guide (CD-270) and the Nippon Denshoku Co. Color and Color Difference Meter 1001 DP using the 1001 DP light guide (1001 DP).
The diameter of the CD-270 light guide head whic h receives the light from the objects was 7 mm. The light was placed on objects with a 45° angle from the center of the light guide. The light from the objects was received by the circumferential part of the light guide (center-circumferent lighting system). However, the diameters of the light guide head of the Improved CD-270 and 1001DP were 2 mm and the light was placed on the objects from the circumferential part of the light guide and the light from the objects was received by the center of the light guide with a 0° angle (circumferent-center lighting system) suitable for measuring small objects such as primary teeth.
The normal primary anterior tooth colors of 30 Japanese children ranging from 3 years to 5 years 2 months of age (average; 3 years 11 months) were chromatically measured using the Improved CD-270. The data was compared with that of the chromatical measuring of 18 Japanese children aged 3 years 8 months to 6 years 6 months (average; 5 years) using the 1001 DP and 30 Japanese children aged 2 years 4 months to 6 years 5 months (average; 4 years 3 months)using the CD-270 which were reported on previously.
The following results were obtained.
1) The mean chromatical values of XYZ, L*a*b*, xy and VCH showed different value patterns among the measurements with the color differen c e meters.
2) The mean chromatical values of a*b* of the various kinds of primary anterior teeth measured with the Improved CD-270 were approximately z e r o and almost white, the same as the values measured with the 1001 DP.
3) However, the mean chromatical values of a*b* of the various kinds of primary anterior teeth measured with the CD-270 were higher and show ed different types of colors.
4) In the mean chromatical valucs, ΔE* between the upper primary central incisors and the other primary anterior teeth showed different values among the measurements with the color difference meters.
5) Chromatical values of the primary teeth color were influenced by the difference of the inserted light volume and sensitivity of the light guide caus e d by the diameter of the light guide head, the difference lighting system and the individual difference of the color difference meters and light guides.6) Additional basic study is required for clinical use of the light guided color difference meters.

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The purpose of this study was to investigate the influence of the structural difference of the color difference meters and light guides on the chromatical values.
The Murakami Color Research Laboratory Light Guided Color Difference Meter CD-270 using the center-circumferent lighting system light guide with the 7mmφlight guide head, the Murakami Color Research Laboratory Light Guided Color Difference Meter CD-270 using the circumferent-center lighting system light guide with the 2mmφlight guide head, and the Nippon Denshoku Co. Color and Color Difference Meter 1001 DP using the circumferent-center lighting system Optical Head OFC-1001 DP with the 2mmφlight guide head were used. The composite resin shade guides of the Photo-Clearfil-A (Kuraray Co. )and Silux (3M Co. ) were chromatically measured with these color difference meters and light guides, and the obtained chromatical values were compared.
The following results were obtained.
1) The mean chromatical values of XYZ, L*a*b* and xy showed different value patterns among the measurements with the various color difference meters and the light guides.
2)The ΔE* between the same shade guides showed remarkable differences among the measurements with the various color difference meters and the light guides.
3) The chromatical values of the shade guides were influenced by the structural difference of the color difference meters and light guides such as the inserted light volume and sensitivity of the light guide caused by the diameter of the light guide head, the difference in lighting system and the individual difference of the color differnce meters and the light guides.

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The purpose of the present study was to investigate the correlations between the increase of the biting force, EMG activities of the masticatory muscle and increase of the grip forces and EMG activities of the flex or anterior muscle of the forearm in term of the development from deciduous, mixed and permanent dentition.
A total of forty persons were investigated; 10 with deciduous dentition (designated as G1),10 with early mixed dentition (as G2),10 with late mixed dentition (as G3) and 10 with permanent dentition (as G4), none of whom had any gnatho-facial dysfunction. EMGs were taken from the right temporal and masseter muscles using bipolar surface electrodes, and the biting forces were measured at the right 2nd deciduous molars (G1, G2) and the right first permanent molars (G3, G4) using bite transducer. The grip forces were measured at the right hand using hand dynamometer and EMGs were takenfrom the right anterior flexion muscles with bipolar surface electrodes.
The results obtained in the present studies were as follows:
1) Though MBF (maximum bite force) showed an increase with age, it was more enhanced during the late mixed, and permanent dentition (G3, G4), when the first permanent molars function in chewing. Conversely the time required to reach MBF (MBFT) is decreased.
2) As the bite forces increased, speed for the maximum bite also acceralated, hence the momentary bite forces of the masticatory muscle increased with age.
3) As to the muscle activities between temporalis and masseter muscle, temporalis muscle activities were predominant during the deciduous and early mixed dentition period, then they shifted to the masseter muscle at the period of later mixed and permanent dentition, when the first molars function positively in chewing.
4) There are positive correlations between the maximum grip force (MGF), the speed of maximum grip (MGS), the maximum bite force (MBF), the speed of maximum bite (MBS). Biting forces were shown to be stronger than grip forces, similarly the momentary bite force was higher than the momentary grip force.
The results obtained in the present study disclosed that a noticeable increase in bite force and momentary bite force may depend on the prominent development of the masseter muscles occuring after later mixed dentition. Grip forces and momentary grip forces may also be associated with the muscle development of the forearm.

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The purpose of this study was to explain the growth and development changes of oral morphology in infants.
Nineteen infants were included in this study. In addition to dental growth measurements, records were obtained of birth weight, birth history. One infant was breast fed and eighteen infants were bottle fed. The materials were the serial dental casts (with at least 4 months of follow up) obtained from 8 males and 11 females during the first one year of life at one month intervals.
Growth changes were studied by three-dimentional measurement of the casts.
The following conclusions emerged:
1) All alveolar lengths in the maxillary and madibular showed a tendency to increase. Especially the anterior portion of the mandibular increased very much from the 1st month to the 4th month, but exhibited little change thereafter. The posterior portion of maxillary and mandibular increased from the 7th month to the 12th month.
2) All alveolar width in maxillary and mandibular increased more markedly from the 1st month to the 6th month than from the 7th month to the 12th month. In the posterior portion, growth changes continued from the first month to the 12th month. But the palatal width increased very little during the 1st month to the 12th month.
3) Palatal hight increased only slightly during the 1st month to the 12th month.
4) Segittal morphlogy palate showed S-line's shape.
5) The para alveolar wall was clear from the 1st month to the 2nd month, but it gradualy became unclear thereafter.

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A total of 146 young permanent teeth of dogs were pulpotomized in groups of 6. In group I, IV and II, V, the pulp stumps were treated with 2% or 5%glutaraldehyde (GA) for 5 min. Thereafter, the pulp stumps were covered with calcium hydroxide paste in group I and II, and zinc oxide-GA paste in group IV and V. As controls, the calcium hydroxide technique was used in group III and the FG technique was used in group VI. The dogs were killed after 2,4,8 weeks and the materials were evaluated histologically.
The results may be summarized as follows:
1) Four weeks after the operation, the teeth in group I, II, III showed a dentinlike hard tissue barrier, but only one tooth in group IV, V, VI had a hard tissue barrier. It seemed that the pulp covered with the zinc oxide-GA paste made no hard tissue barrier, but the pulp covered with cal c ium hydroxide made one.
2) The pulp treated with 5% GA (group I, IV) showed more severe inflammation than those treated with 2% GA (group II, V).
3) Two weeks after the operation, the teeth in. group I demonstrated a large amount of bone-like hard tissue barrier. As compared with the teeth in group III, initiation of the forming of the dentin-like hard tissue barrie r in group I was late. However, after 8 weeks, the width of the hard tissue barrier observed in group I was larger than that in group III. The results show that GA used with calcium hydroxide may be useful as a pulp dressing.

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Fourier analysis was used to compare the forms of the coronal and basal arches of the normal occlusion and the malocclusion. The materials consisted of 16 longitudinal stone casts of the normal occlusion and 8 longitudinal stone casts of the malocclusion.
The follo w ing conclusions were obtained;
1. Upon Measuring the interdental space of deciduous dentition, the malocclusion was found to be smaller than the normal occulusion.
2. The coronal arches of the normal occulusion showed individual variations compared with the normal occlusion in the deciduous dentition.
3. No differences were observed in the size of the basal arches between the deciduous dentition and the permanent dentition of the malocclusion.
4. The sizes of the maxillary basal arches of the malocculusion was smaller than that of the normal occulusion in the deciduous dentition.
5. Definitive differences of shape were observed in the maxillary coronal arch, maxilary basal arch of the permanent dentition between the normal occulusion and the malocculusion.

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In order to trace the relationship between deciduous dentition and permanent dentition, we measured the maxillary basal arch length and the width of 3 stages, the deciduous first term, the deciduous last term and the permanent term. The materials consisted of 16 longtudinal ston cates of the normal occlusions and 8 longtudinal ston cates of the malocclusion.
The following conclusions were obtained:
1. Measuring of the basal arch width of the primary canine, showed that the malocclusion was smaller than the normal occlusion in deciduous last term.
2. In the normal occlusion, the basal arch width of the primary canine increased in the deciduous dentition.
3. In the malocclusion, no differences were observed in the width of the basal arches of the primary canine in the deciduous dentition.
4. Growth of the basal arch width of the primary canine, was a very important factor for the normal occlusion.

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We have conducted a survey on oral examinations of handicapped children belonging to the IV, V, VI, and VII (groups according to Uehara's classification 341 handicapped children (199 males,142 females) were examined during the first and recall visits.
The results were as follows:
The most of cases were revealed to have congenital heart diseases, which were of 154 patients. There were shown of 99 cases with systemic diseases,46cases with hematologic diseases and 42 cases with speech distrubances respectively.
Their ages ranged from 2 to 6 years, which were 65% of total cases. The average age was 5.9 years. Their chief complaints were caries, occupying 313cases out of total 341 patients (91.8%). Most of the patients were referred by Pediatric Department of our medical hospital.
Apparently, poor oral hygiene was contributed to significant increase of severe dental caries, which were prominent especially in the CHD patients as compared with normal children. Upon analysis of dental treatment given to the deciduous teeth, it was found that restoration of the crown was the most common treatment, accounting for 41.2%. Pulp treatment, extraction of mild teeth and prophylaxis were necessary treatments accordingly.
As for permanent teeth, it was found that restoration of the crown, accounted for 39.4% of the patiens. Prophylaxis, pulp treatment and extraction of teeth were necessary treatments accordingly.
More new caries development were found in comparison with secondary caries on recall visits. Prophylaxis is the most important treatment in handicapped children, especially CHD patients in order to prevent for their development of dental caries. The periodical examination is essential for this purpose.

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The process of enamel maturation during the period from enamel formation to tooth eruption was studied in the thin sections prepared from bovine incisors. The degree of mineralization and the concentrations of Ca, P and some trace elements (Mg and Cl) were measured at 4 sites on the sections from incisal to cervical.
The results were as follows:
1. At the stage of 1/2 crown formation, concentrations of Ca and P in the enamel were 50% of the level of an erupted tooth. When crown formation was completed, the Ca and P concentrations had reached levels higher than 80% of the erupted tooth enamel. Analyses using microradiography indicated that the degree of enamel calcification was below 1% of the too t h at the time of eruption. Mg and Cl concentrations showed a slow incr e ase.
2. In the early stage of root formation, the concentrations of Ca and P were equal to those in the erupted tooth enamel. However the level of calci f i cation was still low and kept rising. The concentrations of Mg and C l were going up at the same rate as in the former stage.
3. In the late stage of root formation, there was no change in the concentrations of Ca and P. However a remarkable increase in the level o f calcification was observed, and was higher in the inner enamel than on the enamel surface. The greatest increase of Mg concentration was found on t h e enamel surface up to a depth of 60, um, whereas, the inner layer of the enam e l had a lower level of concentration. The continuing increase of Cl co n centration was also found in this stage.
4. During the stage of tooth eruption, there was no change in the concentrations of Ca, P and Mg, but the degree of enamel calcification was rising. It was found that the level of calcification in the erupted part of the enamel was higher than that of the unerupted part. The concentration of Cl had increased at the inner layer, and reached almost the same level in whole area.

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Reactive hyperplasia arises frequently in adult gingiva, but rarely in infant gingiva.
This paper reports on a case of fibrous hyperplasia of palatal gingiva in a 2 year-8 month-old girl and which contains histologically many epithelial islands. The islands were classified into 2 types: dental lamina-like and squamous epithelium-like.
Some squamous epithelium-like epithelial islands showed calcifications. The relationship of the covering epithelium (oral mucosa) and the epithelial islands were studied with 100 numbers of serial section under light microscopy in order to determine the origin of the epithelial islands, to discover if it is odontogenic epithelium or not. The results suggested that the epithelial islands in this case originated from the covering epithelium.

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The Silver-Russell syndrome is a type of intrauterine growth retardation, characterized by low birth weight at term, shortness of stature, asymmetry of body, variation in sexual development, pseudohydrocephalus, triangular shape of face and inverted V shape of mouth, and so on.
This syndrome is described in a 4-year,1-month-old girl, who had a low birth weitht at term, shortness of stature, asymmetry of body, pseudohydrocephalus, triangular shape of face, in-curved fifth fingers, micrognathia and low set ears. In addition to these general findings, this case also disclosed the following dental findings:
1) Each of the mesiodistal lengths of all primary teeth were smaller than the standard size.
2) The form of the mandibular dental arch was asymmetrical.
3) Roentgenogram revealed large pulp chambers in the primary teeth, especially in primary canines and primary molars.
4) The mandibular body and ramus showed insufficient growth, according to cephalogram analysis.

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This paper reports on a case of eruption sequestrum, an anomaly associated with the eruption of teeth in children, found in lower left first molar region of 6year-old boy. Intra-oral examination revealed, that a tiny hard tissue fragment yellowish white in colour and with bone-like hardness in consistency on the occlusal surface of the lower left first molar which was erupting. This hard tissue fragment showed roentogenologically a bone-like radiopacity, and was easily remoned from the gingiva under local anaesthesia. The resected specimen was irregular in shape, and was composed histopathologically of necrotic compact bone (sequestrum)which was surrounded by bacterial aggregates. Chronic inflammation was seen in the gingiva which was in close contact with the sequestrum.

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[in Japanese]

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