In this experiment, acid etching was applied to the surface of teeth, and the subsequent changes in the enamel surface were observed. This acid etching has been widely applied in recent years as an indispensable method in clinics. The experiment was conducted on teeth with different histories after eruption in order to find out the differences in reaction to the treatment.
For this experiment, immature permanent teeth and those which had erupted more than 20 year ealier, all of them being the lower buccal first molars, were used. The mesial half of each. of the teeth was given acid etching in the buccal surface and the process was observed immediately thereafter with SEM and TEM using the replica method. At the same time, the surface of each tooth was observed with the naked eye, and photographs were also taken. As a result, it was suggested that there were changes occurring in the reactivity of the tooth surface after eruption. It was observed that, between the immature teeth and the matured teeth, there was a differences observed immediately after acid-etching not only in the form but also some in the length of the required flattening of the enamel tooth-surface. This resulted from the changes taking place following the application of the acid-etching.
Furthermore, with regard to the flattening of the enamel-surface and the recovery of the luster in the buccal surface after the application of the acidetching, it was noted that the mechanical abrasion due to brushing was greater that has been reported in the past.

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On the basis of a clinical investigation completed in 1982, we pointed out the necessity for the improvement of some aspects of K-G posterior restorative composite resin. In the present study, in order to obtain a resin with better operability and physical properties, several posterior restorative composite resins of various consistencies were prepared on an experimental basis, and their physical properties were examined. The experiment included observation of inorganic fillers by means of scanning electron microscopy and determination of consistency, filler content, surface hardness, compressive strength, tensile strength, and bending strength.
The results were as follows:
1) The consistency softened in proportion to the decrease in the inorganic filler content.
2) With a decrease in the filler content, the knoop hardness decreased on a nonpolished surface, but remained unchanged on a polished one.
3) There was no difference in the compressive strength in relation to the filler content.
4) The tensile strength and the bending strength increased with a decrease in the filler content.
The above finding show that softening of the consistency by reducing the filler content causes no particular changes in the hardness of the polished surface or in the compressive strength, achieving favorable tensile strength and bending strength and resulting in improved operability. This seems to lead to a decrease in the incidence of body fracture in the restoration of the proximo-occulusal cavity of the deciduous posterior teeth.

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The objective of this study was to elucidate influential factors of difficulty in treating impacted teeth.
At the Pedodontics Clinic of Iwate Medical University, we investigated 67teeth in 56 cases that we uncovered and extracted the impacted teeth.
The results were as follows:
1) The most common cause of dental impaction was malposition.
2) Girls had more impacted teeth than boys with about a 2: 1 ratio.3) The most frequently impacted position appeared on the maxillary central incisor.
4) It was possible to induce the dilacerations of the maxillary central incisor, even if the angle of crown axis inclination was about 100 degrees. It was possible to preserve the dilaceration, if the angle of root axis inclination was with in 90 degrees, by inducing them so that the toot apex was not exposed on the bone and administering crown restoration to them.
5) Most of the roots when the treatment began were incomplete.
6) When the treatment began, the period of eruption were delayed about 2years as compared with normal eruption time in all tooth types.
7) All of molars were exposed, but all of maxillary central incisors and canines were both exposed and extracted.
8) The induction period was shorter in teeth with incomplete roots than teeth with complete roots, being was 13 months on an average. Therefore it is thought that the treatment should be begun before the root has been completed, if the eruption time was delayed compared with the normal time.
9) After the treatment, pulp death, and root and alveolar bone absorption were not observed in the all cases.
10) The gingival swellings of the root apex position were observed in 4 maxillary central incisors, but there was no exposure of the root apex on the alveolar mucosa.
11) Gingival retraction at the cervical margin was observed in about 20% of the cases, but it was within 0.5 mm or 1.0 mm. Moreover this retraction was not effected by the method employed in the operation.

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This study attempted to compare physiological root resorption of pulpotomized primary dog teeth in an operation involving calcium hydroxide paste (Calvital)with the control teeth with normal pulp from the histopathological standpoint.
The results were obtained as follows:
The resorption rate of the root treated primary teeth was almost the same degree as in the controls from the histopathological standpoint.

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The mechanical properties of nine different kinds of commercially available composite resins were investigated these being diametral tensile strength, bending strength, Brinell's hardness, and the weight changes by immersion in artificial saliva. The findings were as follows.
As far as diametral tensile strength, bending strength and Brinell's hardness were concerned, the microparticle filled resins showed significantly lesser measurement values, compared with the conventional composite resins and the posterior composite resins (p<0.01). On the other hand, the posterior composite resins did not show significant differences in measurement values as compared with those of conventional composite resins (p>0.05). The weight increase of Microrest AP by immersion in artificial saliva showed a significantly higher value as compared with those of the other eight composite resins. On the other hand, the P-10 and Clearfil Posterior showed a weight decrease by the seventh day of the experiment.

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Dental examinations and the caries activity tests by Cariostat, Resazurin Disc, improved MSB broth, and enamel biopsy were performed on 62 severely handicapped hospitalized patients (32 males and 30 females) ranging in age from 5 years 5 months to 35 years 3 months (average: 17 years and 9 months) in July,1985.
The following observations were made.
1. A total of 62 patients were examined,44 (71%) of whom suffered from cerebral palsy. As for the IQ range of the patients 85.5% of them were under 25and the rest of them was between 25 and 50. As for the degree of the physical handicap of the patients,54.8% were severe and 35.5% were moderate.
2. In primary teeth, the def ratio was 43.6% and def index was 3.8; in permanent teeth, the DMF ratio was 49.6% and DMF index was 11.5.
3. The DMF ratios were statistically higher in the groups in which the patients had a low risk with rice and soft diet and needed no help when eating than the groups in which patients had a high risk with soft or mixered diet and needed help when eating.
4. The scores of the caries activity tests were as follows. Cariostat:_??_(0%), ++(3 7.1%), + (56.5%), - (6.5%)Resazurin Disc: high (51.6%), Middle (48.4%), Low (0%)Improved MSB broth:_??_(9.7%), ++(46.8%), - (32.3%), - (11.3%)
5. A statistically significant difference was obtained between the Cariostat score and DMF ratio, and DMF index. The increase of the caries pr e valance was observed with an increase in the Cariostat score. However n o relationship was observed between the caries prevalance and both of the RD Test score and the improved MSBB score.
6. A statistically significant difference was obtained between the score and the diet forms in RD Test. The number of pati e nts with a high score was significantly lower in the white rice and soft diet group than in the soft diet group, and the mixered group.
7. A statistically significant difference was obtained between the score and the number of tooth brushings in the RD Test. The number of patients with a high scor e was significantly lower in the three time brushing group than the single brushing group.
8. There was no statistically significant difference in the enamel calcium solubility between 23 patients and 16 controls by enamel biopsy (Nakagaki M e thod).
9. There was not such an inclination that the higher enamel solubility the patients showed, the higher caries prevalance they had. The minus correlation (r = 0.43) was obtained be t w een the enamel calcium solubility and DMF index.

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An epidemiological evaluation of the effect of dental health education on school children was made. The subjects were from two elementary schools located in a similar geographical and socioeconomic environment in the suburbs of Gifu city. One served as the test school and the other as the control school. The test school had approximately 1000 school children fromthe first to the sixth grades, and the control school had about 900 children. Dental health care education was given to the children in the test school through the teachers who had been well instructed in dental health education by staff members of Department of Pedodontics Asahi University School of Dentistry. Later the oral hygiene level of the children was evaluated by the visible plaque index (VPI) and the gingival bleeding index (GBI) by Ainamo & Bay.
The results were as follows. The mean VPI and GBI in the test school showed a significant decline. The tendency of this decline follows the negative acceleration curve which is characteristic of the learning process curves. In addition, the mean VPI and GBI values in the test school were significantly lower when compared with the control school and either the VPI or GBI values were higher in boys both in the test and the control school. Also the number of children with a score of 0 for the VPI and GBI values increased significantly in the test school.
From the results obtained in the present study; it was suggested that dental health program given by the teacher could be an effective approach for improving the dental health conditions of school children as far as the VPI and GBI is concerned.

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The purpose of this study was to evaluate the possible role of the nursery environment in relation to the caries prevalence in children.
On the basis of oral examinations of 138 children (87 boys and 51 girls), their ages ranging from 3 to 6 yr., and the questionnaires to their parents, the correlation of the caries factors to nursery environment were studied.
The affects of the nursery environment on the deciduous caries incidence were evaluated using Hayashi's Quantification scaling type I.
The correlation of the factor to factor were evaluated by Stuart's coefficient.
The results obtained in the present study were as follows.
1. Each factor of nursery environment was quantified as items of caries.
(1) Every day tooth brushing before sleeping (sometimes: 3 points, certainly: 8 points)
(2) Intake of between-meal snacks regularly (8 points)
(3) Frequency of between-meal snacks per day (2 times: 8 points; less than 1 time: 12 points)
(4) Sweetened bevarages not stored in refrigerator (5 points)
(5) Intake of nothing but water and tea before sleeping (27 points)
(6) Not buying sweets by oneself (8 points)
(7) Drinks, intake chiefly of milk, hand made juice, tea and water (4 points)
(8) Good appetite (1 point)
(9) Not instructions or suggestions concerning caries or caries initiation (20points)
(10)Cariostdaat ta (0∼7 points)
2. More than 50% of the caries could be predicted with 10 nursery environmental factors: contribution rate R²=0.518.
3. A reference pattern was found by correlation of caries factors in the nursery environment.
4. It was suggested from the aforementioned results that giving a disciplined nursery environment to the child is a positive factor in caries prevention factors.
5. Controled snacks and bevarages after dinner were suggested and the methods most prefered for preventing caries initiation.

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The purpose of this study was to investigate pulp responses to an electric pulp stimulator in permanent teeth with imcompletely formed apices.169 normal permanent central incisors of 86 children, aged from six years and nine months to thirteen years and five months, were examined in this study. Root development was rated from the standardized radiographs in 3 stages. Stage I; the apical foramen is widely diverged, similar to a funnel shape. StageII; the apical foramen is open and the canal has nearly paralell walls, the root formation is imcomplete. Stage III; the apical foramen is still open and the formation of the root is almost complete.
We used an automatic“Pulp Tester”(Analytic Technology Co. ) and“Dentotest TB-08”(Malek's). The conduction media for the electric pulp testers were tooth paste (Kodomohamigaki: Lion Co. ) and electrode paste (Cardio Cream: Nihon Kohden Kohgyo Co. )
The results were as follows.
1)“Dentotest TB-08”with tooth paste: 13 cases (22.4%) out of the 58 cases in root development stage I and 2 cases (3.9%) out of the 51 cases in stage II did not respond up to the highest point on the electrometric pulp tester. In stage III, all cases responded to electric stimulation.
2)“Dentotest TB-08”with electrode paste: 7 cases (12.1%) out of the 58 cases in stage I and 1 case (2.0%) out of the 51 cases in stage II did not re-spond spond up to the highest point of the electrometric pulp tester. In stage III, all cases responded to electric stimuration.
3)“Pulp Tester”with tooth paste: 5 cases (8.6%) out of the 58 cases in stage I did not respond up to the highest point. In stage II and stage III, all cases responded to electric stimulation.
4)“Pulp Tester”with electrode paste: in stage I, there were 2 cases (3.4%)out of the 58 cases did not respond up to the highest point. In stage II and stage III, all cases responded to electric stimulation.
5) It appeared that threshold value decreased for both electrometric pulp testers when root development increased.

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Fourier analysis was used to compare the forms of the coronal and basal arches of the deciduous dentition and the permanent dentition of the normal occlussion. The materials consisted of 16 longtudinal ston casts.
The following conclusions were obtained;
1. The maxillary coronal arches showed individual variation in the permanent dentition, but the maxillary and mandibular basal arch showed in individual variation in both the deciduous dentition and the permanent dentition.
2. The average form of the maxillary coronal arch the permanent dentition was larger than that of the deciduous dentition in size and the shapes was similar to a semicircle. No differences were the observed in the average form of the mandibular coronal arch between the deciduous dentition and The permanent dentition.
3. Denfinitive differences in size were observed in the maxillary basal arch between the deciduous dentition and the but no permanent dentition differences in size were observed in the mandibular basal arch.

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Lead-EDTA which was reported to be a stable chelate compound, combined less with the tissue protein than with acid acetate, excreted rapidly, had a low toxicity and was used for both intraperitoneal or subcutaneous injection.
In this study we examined the methods, doses in using lead-EDTA and the methods for embedding the materials.
In this experiment four healthy puppies from 2 to 3 months old were used and received intraperitoneal and subcutaneous injections of 10,20,30,40,50 mg lead-EDTA/kg body weight daily at fixed times, this was performed for a total of six times.
They were fixed in 10% formalin and the tissues were decalcified in 0.2N HC1 for a week using the modified decalcifying apparatus. The decalcified materials were then embedded in the usual way in celloidin, paraffin, celloidinparaffin, or carbowax without alcohol. After that the sections were cut and placed in gold chloride.
The results were as follows.
1. Based on the use of the modified decalcifying apparatus, the particular odor of H₂S decreased remarkably and besides that the condition of the decalcification was good.
2. Concerning the methods of giving lead-EDTA, labeling lines appeared almost the same both by the intraperitoneal and by the subcutaneous injection.
3. Concerning the embedding methods, the labeling lines appeared most clearly with carbowax and paraffin.
4. Looked at on the whole, the condition in which the labeling lines were certain to appear was with a subcutaneous injection of 30 mg/kg of body weight of lead-EDTA and by embedding in paraffin.

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Mutastein, derived from a strain of Aspergillus terreus, has been shown to inhibit specifically the glucosyltransferase (GTase) of Streptococcusm utans in in vitro experiments. In the present study, the caries-inhibitory effect of mutastein was examined in an animal experimental system. Growing cells of S. mutans MT6265R (serotype c), B13R (d) and 6715 (g) exhibited a marked adherence to a glass surface in the presence of sucrose. However, addition of mutastein to the sucrose medium resulted in a significant reduction of cell adherence. Furthermore, crude GTase prepared from each strain of S. mutans synthesized insoluble glucan from sucrose. The amount of insoluble glucan produced from sucrose by the GTase decreased markedly when increasing amounts of mutastein were added to the reaction mixture.
The inhibitory effect of mutastein on caries induction was examined in SPF rats infected with S. mutans MT6265R, B 13R or 6715 and fed diet 2000. Mutastein was incorporated in the diet and the drinking water in various concentrations from one day before the inoculation of S. mutans through to the end of the experiment. Administration of mutastein significantly inhibited caries induction by serotype d and g S. mutans. Also, caries induction by serotype c S. mutans decreased in the presence of mutastein, but the difference was not significant.

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Caries-inducing activity of TG syrup was examined in vitro and in animal experiments. The syrup contains mono- and oligosaccarides, with isomaltose and panose as its principal constituents. TG syrup can be utilized as the substrate for acid production by Streptococcus mutans MT8148R (serotype c) and 6715(g). Growing cells of S. mutans produced a marked adherence to a glass surface in 1% sucrose, while minimum adherence was recognized in 1% TG syrup. The adherence gradually decreased as the amount of TG syrup in the reaction mixture increased. The amount of insoluble glucan produced from sucrose by crude GTase of S. mutans decreased markedly when increasing amounts of TG syrup were added to the reaction mixture containing 1% sucrose. TG syrup developed weak caries in SPF rats infected with S. mutans MT8148R or 6715, whereas sucrose induced notable dental caries.
These results indicate the low cariogenicity of TG syrup and the possibility of being utilized as a sucrose substitute.

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Strains of Streptococcus mutans were isolated from plaque and softened dentin from 28 2-7 year old children. Serotypes and extracellular bacteriocin (mutacin)production were investigated. The total number of isolated strains was 288. Distribution of serotypes c, d, e, f and g were 71.2%,7.7%,14.9%,4.5% and 1.7%, respectively. Serotypes a and b were not isolated. The higher the caries activity and the higher the caries severity index the more serotypes other than c were isolated. Strains of 222 in 288,77.1%, produced mutacin against indicator strains S. sanguis ATCC 10556R, S. sanguis OMZ 9HR1, and S. salivarius HT9R by the stab culture method,33 strains (11.5%) against the same indicator strains by the drop assay method, and 30 strains (10.4%) against indicator strains S. mutans (serotypes a to g) by the drop assay method. There were three strains which produced mutacin against S. sanguis and S. salivarius but not against S. mutans. The medium influenced on mutacin production. Mutacin in the Todd Hewitt broth revealed the most bacteriocin-like activity against S. mutans. The second was the Tryptose phosphate broth, the third was the Brain Heart Infusion broth, and the last was the Trypticase Soy broth. Serotypes c and f of indicator S. mutans showed wide susceptibility to mutacin from various strains of S. mutans isolated from children, and serotype g showed narrow susceptibility.

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This paper concerns a case of hyperplasia of the pericoronal fibrous connective tissue resulting in impaction of the bilateral secondary molars of both the mandible and maxilla. The patient was a 15-year-old boy with retarded eruption of the secondary molars discovered during a loutine dental examination. His family and past histories were non-contributory. Upon examination, nonremarkable changes in general and facial finding were found. X-ray examination revealed well circumscribed and wide radiolucent lesions around the crowns of the impacted secondary molars, and the clinical diagnosis of a follicular cyst (dentigerous cyst) of the secondary molar region was made. Surgical findings revealed that the pericoronal lesions of the bilateral secondary molars of the mandible and maxilla were composed of grayish white soft tissue, and no cystic spaces were found in any of the lesions. Histopathological examination showed that marked hyperplasia of the pericoronal fibrous connective tissue of the secondary molars, i. e., proliferation of the collagenous fibrous tissue wi th dense and irregular arrangement, and islands of reduced odontogenic epithelia were scattered in the fibrous tissue. Based on these histopathological findings, this case was diagnosed pathologically as hyperplasia of the pericoronal fibrous connective tissue of the secondary molars. The pathological cause of hyperplasia of the pericoronal fibrous connective tissue was considered, but no final conclusion was reached.

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We experienced a rare case in which the over root canal filling with Vitapex in the deciduous tooth was the cause of a transposition and a dentinogerous cyst formation on the maxillary left permanent central incisor germ.
On filling the maxillary left deciduous central incisor of a three-year and nine-month-old female with Vitapex, heavy material 3×11 mm in size was extruded from the apex into the center of the permanent tooth germ. Six months later, there were no subjective symptoms, but unusual bony swelling occurred at the labial plate of the maxillary left deciduous central incisor. On the roentgenograms the extruded material was no longer seen but radiolucency resembling a dentinogerous cyst appeared around the crown. We treated the case by extracting the deciduous tooth and by marsupialization at the lesion of the permanent tooth. Consequently the lost filling material remained at the lingual side of the permanent tooth germ and was forced down against the labial side. Furthermore two years later, the permanent tooth germ moved a little to the lingual side, the radiolucency surround the permanent tooth germ disappeared, and the root formation started.
The results were as follows,
1. With deciduous teeth filling with Vitapex, excessive root canal filling must be avoided.
2. At the stage of crown completion, transposition and dentinogerous cyst formation may lead to root delaceration, the transposition of teeth or the discontinuity of permanent tooth development. It was best that we undertook marsupialization treatment actively in order to avoid these impedimentia.

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Well-demarcated tumorous lesions are often observed in the oral cavity. However, these are commonly found in adults and rarely in infants except in cases of congenital epulis. Such lesions arise on the gingiva, buccal mucosa, tounge, lips and palate, most of which are inflammatory fibrous hyperplasia while the true fibroma is rare.
This report is concerned with a case of fibrous hyperplasia which was observed in a 9-old male child. A pedunculated, firm mass was noted on the area of palatal mucosa behind the upper left deciduous central incisor. When he was 11 months old, it was surgically excised.
Histopathologically, there were a few considerably cellular foci of plump fibroblasts which resembled fibromatous growth, but for the most part, the lesion consisted of an excessive bulk of collagen fibers interspersed with a number of small blood vessels and inflammatory cell infiltration. The lesion was covered by parakeratinized stratified squamous epithelium. The histopathological diagnosis was therefore fibrous hyperplasia. Hyperplastic growth of the fibrous element in this lesion was attributed to an inflammatory process resulting from chronic irritation.
In general, hyperplasia of the fibrous element may arise from the periodontal membrane, including that of the supernumerary teeth. Two impacted supernumerary teeth in the maxillary incisal region in the present case, however, were thought to be unrelated to the fibrous hyperplasia of the palate.

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This is a case of teratoma of the buccal mucosa in an infant. Histological examination revealed that this tumor consisted of two germ-layers, i. e., ecto- and meso-dermal tissue, with several toothgerms.
We further reviewed 70 cases of teratomas in the oral and nasopharyngeal regions reported in Japanese literature, and the following findings were obtained.
1. This tumor occurred predominantly in infants under one year of age, and about78% of the reported cases were females.
2. This tumor occurred most frequently in the nasopharyngeal region, and the palatal region when limited to the oral cavity.
3. Complicated deformity (cleft lip and palate, etc. ) was often observed.

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We conducted treatment of dental caries and examined regulary the oral conditions of The handicapped children in two institutions of Tokyo Infant Recuperation Hospital, one, Institution A for the children with mainly cerebral palsy and the other Institution B for the children with several and multi-handicappes.
This paper concerns the investigation on the actual state of dental treatment with or without general anesthesia during the past five years, from Feb.1980 to Dec.1984.
The results obtained were as follows.
1) The average age of the children of Institution A in 1984 was less than in 1980. On the other hand, The average age of the children of Institution B in 1984was greater than in 1980.
2) In the past five years (1980-1984), only the number of patients with cerebral palsy decreased. The proportion of patients with not only cerebral palsy but epilepy, mental retardation, or other syndromes had increased.
3) The number of patients treated under general anesthesia showed a tendency to decrease. The number of patients treated at The ambalatory clinic increased.
4) The most commonly preferred kind of restoration in cases treated under general anesthesia was composite resin. The mean number of treated teeth under general anesthesia was 12.2. During the first two years, as for dental treatment at ambulatory clinic, extraction was the most common procedure. After three years, however, the most commonly preferred kind of restoration n cases treated at The ambulatory clinic was also composite resin.
5) The cases in which endodontic procedures were performed under general anesthesia decreased. On the other hand, the number of similar cases at The ambulatory clinic increased especially for permanent teeth.
6) The rate of DMF (def): The rate of D (d) (1984) decreased at both of institutions. The rate of F (f) (1984) increased, especially for the multihandicapped children.
7) CARIO STAT was used for determing the caries activity. The number of children who showed low caries activity (-∼+) increased.

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Dental treatment under general anesthesia has become a valuable procedure for the management of handicapped children. In our clinic, general anesthesia was introduced about 19 years ago and since then its significant role in treatment has been fully recognized. The purpose of the present study is to survey the cases of dental treatment performed under general anesthesia at our clinic during the past 19 years. The results are summarized as follows:
1) 105 patients (76 boys and 29 girls) were treated under general anesthesia during this period. The number of patients per year was less than 10 during the years 1967-1982, although a gradual increment has been recognized since 1983. There were differences in several respects concerning the ages and diseases of patients, as well as the therapeutic procedures when the cases treated during the years 1967-1975 (first term) were compared to those treated during the years 1980-1985 (last term).
2) In the first term,77% of patients were under 10 years of age, half of whom were handicapped with cerebral palsy. On the other hand,93% were over 11 years in the last term, one third of whom were affected with emotional disturbances.
3) The mean number of treated teeth per patient was 10.6 in the first term, the majority of which were deciduous teeth, either extracted or filled with amalgam. On the other hand,7.1 teeth per patient were treated in the last term, most of which were permanent teeth, and more than half of which were restored with inlays or cast crowns.

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Caries prevalence among the primary teeth and the permanent first molars was surveyed in 1000 out-patients who visited the Pedodontic Clinic of Tsurumi University Dental Hospital from May 1984 to November 1985.
The number of def teeth and the def teeth ratios were calculated in comparison with those of our previous report in 1972, and the following results were obtained:
1. The caries prevalence of the patients was more than 90% in age groups of over 3 years old.
2. The mean def-t and def-t ratios showed a consistent decrease in all current age groups, being particularly significant in the 2 to 3-year-old groups.
3. The def-t ratios of the upper primary incisors and the canines showed a re-. markable decrease in the 2 to 3-year-old groups, suggesting delayed initiation of dental caries, whereas the decrease in the primary molars was not significant and the incremental ratios with age were rather similar to the 1972 data. The dental caries prevalence of the permanent first molars showed no significant difference between the 1972 and the current groups.
4. The def-s ratios decreased on the labial surfaces of the upper primary incisors and the canines as well as in the occlusal surfaces of the primary first molars, suggesting that the early and multiple surface caries initiation, as well as its rapid progress had declined. Interproximal caries of the primary molars increased in contrast to the decrease of occlusal caries. This might be due to the improved caries detection technique and to the relative increase of contacting proximal surfaces. Although permanent first molars showed a rapid progress of caries immediately after the eruption, further investigation in older children is necessary to evaluate the caries prevalence of the first molars.

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10 submerged deciduous molars in 5 children were studied longitudinally, until the eruption of their successors. The results were as follows: 1.
The situation of the occurrence.
1) There were no differences according to sex.
2) The 10 affected teeth were distributed: 4 lower first deciduous molars,4 lower second deciduous molars,1 upper first deciduous molars, and 1 upper second deciduous molars. The mandibular deciduous molars were affected significantly more than the maxillary teeth.
3) Bilateral instance was found in 1 out of 5 cases.
4) In 5 cases,4 children had some malocclusion, only 1 child had normal occlusion.
2. Of the 5 affected teeth, increased submergence occurred with 2 teeth, and with 3 teeth re-emergence of the submerged teeth was noticed.
3. Of the 10 affected teeth,5 teeth were normally exfoliated,4 teeth were extracted easily (their root resorption was normal), and 1 tooth was extracted for the purpose of orthodontic treatment. In all 10 cases, the successors erupted normally.
4. For the treatment of the submerged teeth, they were graded on clinical observation, according to the degree of submersion: slight, moderate, and severe.
5. In all cases, submerged deciduous teeth should not be removed immediately, a watchful waiting approach being best. At times, a space-maintainer(grade: moderate) or a space-regainer (grade: severe) may be used.

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[in Japanese]

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[in Japanese]

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