It has been generally considered that the susceptibility of enamel to caries is higher in a newly erupted tooth, and one of the reasons for this susceptibility is associated with the grade of enamel maturation. The present study was carried out to investigate the maturation of enamel associated with caries susceptibility and the affect of saliva on the maturation.
For this purpose, incisors of Wister rats,11,18,20,30 and 53 days after birth, were used in the experiment and the enamel was categorized as follows,
A. the enamel of the erupting region
B. the enamel adjacent to the epithelial attachment
C. the enamel adjacent to the bone and examined with the aid of a Scanning Electron Microscope, Microradiography, Electron Probe X-ray Microanalyzer and X-ray Diffraction for enamel maturation in each region, and the affect investigated when the ducts of major salivaly gland were ligated, and when the immature enamel was exposed to the oral enviornment.
The results obtained from the present study were as follows;
1) Finding with SEM disclosed that there were a number of pits on the enamel surface adjacent to the epithelial attachment of young rat.
2) It was noticed that the distinct hypomineralized areas still existed in the enamel adjacent to the epithelial attachment of 11 day old rats compared with 18-53day old rats.
3) Even after the ligation of the salivaly gland ducts, no remarkable changes of the enamel of erupted region was noticed.
4) The enamel apatite in the hypomineralized areas showed a low crystallinity in the a-axis direction.
5) When the hypomineralized enamel areas were exposed to the oral enviormnent after gingival excision, mineralization would occure and the crystallinity of it was improved in the a-axis. These changes were more reinforced by the topical application of APF gel. These results suggested that immature enamel should be protected immeidately after eruption, in a cases when the unerupted tooth is surgically exposed.

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The purposes of this study were to determine the suitableenergy dentisty of laser irradiation afforded the acid resistance on the enamel surface in situ and to investigate the change of temperature in the pulp chamber at the time of exposure to a laser on the enamel surface and the depth of acid resistant enamel obtained after lasing in vitro.
Extracted deciduous teeth and young premolars were used as materials.
The type of laser was acousto-optically Q switched Nd: YAG laser with an optical fiber. The irradiation was performed at an average output of 10 W with a pulse width of 120 nsec, repitition rate of 1kHz, spot size of 3.0-3.4 mm and various duration times. The results were as follows.
(1) The dissolution of the enamel surface which was put into a lactic acid solution was not noticed with a scanning electron microscope when irradiated at the energy density of more than 37.5 J/cm² on deciduous teeth and more than 62.5 J/cm² on young premolars.
(2) The rise in the temperature in pulp chamber after lasing was observed with increase in the energy density and it was 4-5°C when the reasonable energy density was used to obtain the acid resistant enamel.
(3) The depth of enamel which obtained the acid resistace after lasing at the energy density of 65J/cm² was deeper than 80μm from the enamel surface.

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The caries-inducing activity of palatinose syrup was assessed in vitro and in SPF rats. The syrup is a mixture of mono- and loigo-saccharides and composed of trehalurose and palatinose as the principle constituents. Streptococcus mutans MT8148R (serotype c) and 6715 (serotype g) were able to ferment the palatinose syrup and the pH of the culture decreased markedly. Growing cells of S. mutans MT8148R and 6715 producted a marked adherence to a glass surface in 1% sucrose. However, the percent of adherence decreased when the same amount of palatinose syrup was added to the reaction mixture.
Crude GTase prepared from each strain synthesized insoluble glucan from sucrose. However, the amount of insoluble glucan produced from sucrose by GTase decreased makedly when increasing amounts of palatinose syrup were added to the reaction mixture containing 1% sucrose.
The caries-inducing potential of palatinose syrup was examined using SPF SD rats which had been infected with S. mutans MT8148R or 6715 and fed a cariesinducing diet#2000 containing 56% sucrose, in which palatinose syrup replaced the sucrose fraction. Palatinose syrup did develop weak caries, whereas sucrose manifested significant dental caries in the rats.
However, the caries score of palatinose-syrup-fed rats was significantly higher than that of the wheat flour-fed rats. Furtheremore, partial replacement of the sucrose content with palatinose syrup did not result in a significant reduction of caries development.
These results suggest that the cariogenicity of palatinose syrup may be low, and the cariostatic effect may be extremely weak even if it is recognized.

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The acid etching technique is a widely accepted produdure in the field of caries prevention, restorative dentistry and orthodontics to obtain a better bonding of resin to the surface of the enamel. However acid etching may damage chemically the surface structure of sound enamel. Consequently the etched enamel surface left or unprotected with resin may become the focus of caries initiation.
Some investigators have devoted to the remineralization of acid etched enamel. However, there are some controvesial view points concerning their results.
The purpose of this study was to evaluate chemically and morphologically the remineralization of the acid etched enamel. Enamel surfaces were observed using scanning electron microscopy (SEM), microradiography and analysed by an electron probe microanalyser (EPMA), X-ray photoelectron spectroscopy (ESCA)and infrared internal reflection spectroscopy (IRS).
The experiments were carried out as follows:
1) Immersion in the calcifying solutions. (in vitro)The human tooth enamel was etched with 35% phosphoric acid for 60secouds and immersed in the calcifying solutions for 1,3,5,7,10,20, and 28days at 37°C. The calcifying solutions used in the study contained 1.5 mMCaCl₂,0.9 mM-NaH₂.PO4⋅H₂O and 150 mM-NaCl and at pH₇ and the flow rate was 52 m//hr.
2) Placement in the oral environment. (in vivo)The human tooth enamel was etched under similar conditions as mentioned above and this was attached to the acrylic space maintainer and placed in the oral environment of two girls (A: 8years, B: 7years). The time of placement were as follows: A was 7,30,32, and 45days and B was 13,14,30, and 32days.
The results were as follows:
1) Immersion in the calcifying solutions. (in vitro)The acid etched enamel surface showed a smooth appearance by SEM observation after 10days immersion in the calcifying solutions and the microradiographic observation disclosed similar findings as compared with nonetched enamel. Line analysis of Cakα and Pkα by EPMA and the infrared analysis of the specimen obtained from the surface layer did not show any remarkable differences as compared with the non-etched enamel. After 28days, the binding energy of Ca and P evaluated with the aid of ESCA shifted to the high energy site when compared with non-etched enamel. However the depth of the enamel dissolution (about 20μm) was not restored even after 28 days.
2) Placement in the oral environment. (in vivo)he etched enamel specimens showed a smooth and uniform structure by SEM observation and were similar to these of the non-etched enamel. However the microradiographic findings indicated a lower radio density as compared with sound enamel and the depth of the enamel dissolution (about 20μm)was not restored even after 45days. From these findings it was discovered that full remineralization of the etched enamel placed in the oral environment would not occur.

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The purpose of this study was to investigate the frequencies of fusion and missing of deciduous teeth, the frequency of the abnormalities of their successors, and the changes in mesio-distal and labio-lingual diameters of the crown of deciduous teeth.
One thousand and twenty-four children (506 boys and 518 girls), in Hellman's dental stages II A and II C, who had visited the Clinic of Tohoku University School of Dentistry, were investigated. The study models and oral photographs were used for examination.
The results were as follows.
The frequencies of fused teeth and missing teeth were 5.6 percent and 1.8percent, respectively. These frequencies were found higher in the mandible than in the maxilla. The number of fused teeth was 45 between the lower central and lateral incisors,17 between the lower lateral incisor and the canine, and 4between the upper central and lateral incisors. On the other hand, the number of missing teeth was 18 among the lower lateral incisors,2 among the upper lateral incisors, and 1 among the lower central incisors. There were neither fused teeth nor missing teeth among the deciduous molars tested.
In the case of the fused and missing deciduous anterior teeth, their successors also were found fused or missing with high frequency. Especially in the fusion of the lower deciduous lateral incisor with the canine and in the missing of the lower lateral incisor, the absence of their successors was found more frequently than in the fusion of lower deciduous central incisor with the lateral incisor.
The mesio-distal diameter of the crown of the fused teeth was larger compared with the larger one of the 2 corresponding teeth on the normal control side. The labio-lingual diameter of the crown of the fused teeth showed an intermediate value of the total diameter between the mesial tooth and distal tooth on the normal control side. When the lower lateral incisor was missing, the deciduous canine on the missing side was larger than the lateral incisor, and smaller than the canine on the normal control side. Therefore, the lateral incisor looks as if it is missing if a complete fusion occurs between the canine and the lateral incisor.

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From the clinical point of view, it is important to protect the pulp of primary teeth.
The purpose of this study was to investigate the relationship between the electrical resistance measured with the caries meter after pulpotomy (through the application of calcium hydroxide) and the X-ray findings.
17 primary anterior teeth and 25 primary molars were examined in children from the age of 2 to 6.
The results were as follows;
1) According to radiographic diagnosis of the dentine bridge after pulpotomy, there were some cases (28.6%) where the dentine bridge was formed one monthe after the pulpotomy, though in most cases (51.1 %) it was formed 3 months afterwards.
2) Electric resistance was apt to increase by degrees until 7 months after the pulpotomy, however the increase became more gentle there after. It was found that it took 5 months or more after the pulpotomy to obtain a comparatively high electric resistance(over 12.0 kΩ).
3) In most of the cases where by radiographic diagnosis it was determined that the dentine bridge formed in less than 3 months after the pulpotomy, the low electrical resistance(less than 10.5kΩ)indicated that the dentine bridge was still in a formative state. Assessement of the dentine bridge formation on the basis of radiographic diagnosis alone therefore appears to be of limited accuracy.

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This study was attempted to investigate the effect of acid etchants on diammine silver fluoride applied primary dentin, and to investigate tooth-adhesive resin penetration into it.
57 extracted or exfoliated primary teeth with caries extended into the dentin, to which 38% diammine silver fluoride had been applied clinically for preventing tooth caries (33 cases) or applied after the extraction (24 cases), were used. Softened dentin was removed dry with the steel bars and a hand instrument. The dentin was etched for 1 minute, then rinsed with water for 30 seconds and desiccated with compressed air for 30 seconds.
The commercially available acid etchant (40% phospholic acid), the bonding agent and the resin used in this study was Clearfil-F. The time after application of diammine silver fluoride until the application of the acid etchant and the resin was 14 to 1278 days in clinically applied cases and 0 to 28 days in cases applied after the extraction.
The following observations were obtained under SEM.
1. The effect of the acid etchants was less than in the cases of noncarious dentin and caries decayed but not applied with diammine silver fluoride.
2. The dentin surfaces were covered with cuboidal crystal-like, hexahedral crystallike concrescence, fibriform and amorphouse materials which were not seen in the cases without application of diammine silver fluoride, and the openings of the dentinal tubles were unclear even after etching.
3. The resin penetration into the diammine silver fluoride applied primary dentin was lower than that into the noncarious primary dentin and caries decayed but not applied with diammine silver fluoride.
4. There was not seen any statistical significant difference between the length of the resin tags and the period after application of diammine silver fluoride.

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To understand the development of the masticatory function of the infants at the weaning period, we investigated the methods of feeding baby foods and the eruption of deciduous teeth every two weeks.
The subjects were 20 healthy nursery school children (12 boys and 8 girls), who were from 4 to 15 months old. They were fed on the same food.
In this study, we examined feeding and masticatory methods used for eating baby-food at various ages (in months), types of food and the eruption types of deciduous teeth.
The results were as follows.
1) The types of baby food were something like paste in the early period, something crushed with the tongue in the middle period and something crushed with gums in the later period. The baby-food of the later period was about ten times as hard as that of the eraly period.
2) We were able to devide the feeding and masticatory methods for eating babyfood into 9 ways.
3) The first way was to let their mouths move frequently. The older the babys were, the more common was this way of the feeding, and it became 100 percent at the age of 15 months. According to the eruption type of the decidteeth, this way was increased remarkably among the A|A/A|A type.
4) The second way was to swallow the food by moving their mouth twice or three times. That was increased among 6,7 and 8-month-old children, in the middle period, and it decreased later.
5) The third way was to thrust their tongue frequently. That was shown about 90% of 4 and 5-month-old children, in the early period, and it decreased suddenly later.
6) The sixth way was to make the children suck the food, that was mostly seen in 11-month-old children, and it decreased at the age of 15 months.
7) Other ways were shown between the early and the middle period. As for the eruption it was still the AA type, and it disappeared at the age of 15month.

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Palatinose(a-D-glucopyranosyl-1,6-fructofranose)occur naturally in honey and sugar cane extract and is approximately half as sweet as sucrose. Palatinose is degraded by intestinal isomaltase to produce free glucose and fructose for metabolic utilization. Recently, an enzymatic method to convert sucrose into palatinose on an industrial scale was developed and it becomes possible to gain the palatinose in a large quantity and at a reasonable price. The palatinose preparation is more than 99 % pure and contains no other sugars. The effect of palatinose was examined in in vitro and animal experiments.
1. Strains of S. mutans representing the eight serotypes could not ferment palatinose significantly when the organisms were cultured at 37°C for 48 hr in phenol red broth containing 1 % palatinose.
2. Palatinose was not utilized by S. mutans strains when heavy cell suspensions were prepared and mixed with palatinose, whereas glucose and sucrose was rapidly utilized by the strain and the pH of the mixture lowered markedly within several minutes.
3. Crude GTase prepared from culture supernatant of S. mutans 6715 or MT8148R by ammonium sulfate precipitation could not synthesize insoluble glucan from palatinose, whereas the GTase did synthesize a large amount of insoluble glucan from sucrose. The amount of insoluble glucan produced from sucrose by GTase decreased markedly when increasing amounts of palatinose were added to the reaction mixture containing 1% sucrose.
4. Growing cells of S. mutans produced marked adherence to a glass surface in 1 % sucrose, while minimum adherence were recognized in 1% palatinose broth. Also the percentage of adherence gradually decreased as the amount of palatinose in the reaction mixture increased.
5. Palatinose did not induce dental caries in SPF rats infected with serotype c and g S. mutans, whereas sucrose or glucose manifested notable induction of dental caries. Partial replacement of sucrose by palatinose resulted in a significant reduction of caries development. However, it was also noted that the partial replacement of sucrose with wheat flour showed similar results and there were no statistically differences between the groups that replaced palatinose with wheat flour.
These results indicate the possibility that sucrose could be replaced by palatinose for the purpose of caries prevention in humans.

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The diamond burs were specially designed and tested experimentally for preparation of round and straight bevels of composite resin restorations in posterior teeth.
The shape and size of the bur was so designed that both the width and depth of the bevel should be prepared to be 0.5 mm when it is used when guiding is acquired with tooth surface and cavity wall.
Extracted human anterior and posterior primary teeth were used for experimentation. The cavities were prepared on the labial surface of anterior primary teeth and the occlusal surface of posterior primary teeth and the bevels were placed on the margin of the cavity with the above mentioned bevel-preparing burs. The cavity of each tooth was observed labially or occlusally, and its duplicated plaster model was also examined sectionally with the stereo-microscope.
As a result, the bevels with the use of the bevel-preparing burs were found to be relatively uniform and well prepared.
Next, the thermal cycling test was carried out after composite resin restorations in those prepared cavities. The relationship between marginal form of the cavity and the marginal sealing effect was examined using the dye penetration test.
It was concluded that the cavity with a round bevel showed the most excellent results for marginal sealing.

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A girl 2 years and 5 months old with the chief complaint of premature loosening and loss of the primary incisors, visited the Pedodontic Clinic of Iwate Medical University Dental Hospital. By laboratory examination, she was then diagnosed as having childhood hypophosphatasia.
At the time of the first visit, A|A/BA|ABC had already exfoliated and other teeth were loosening.
Particularly, C|C showed remarkable mobility and exposure of their roots. There was moderate gingivitis around the loosening teeth.
Radiographs showed the resorption of alveolar bone and abnormally large pulp chambers in remaining tooth.
The enamel was almost found to be normal.
In the dentine of crowns, near their surface, there were anumber of lacunae along the outward form of dentine.
Osteodentine and disorderly arrangement of dentinal tubuls were observed at the root surface. On the other hand, they were almost normal at near the pulp cavities.
Cementum was found about the central area of the roots of |B and D|, which was very thin, and no cementum was found at the other area.
The periodontal fiber was sparce and fragile.
Therefore, we believe that the exfoliation or loosening of the primary teeth caused by their structure.
For the present the parmanent tooth germ has been developing normally.

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Although the presence of an embedded foreign body in the oral and maxilloracial region is not unusual, it is difficult to diagnose a complicated roentography. A glass chip embedded in floor of the mouth in a 7-year-old male is discussed.

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Papillon-Lefevre syndrome is a rare disease, the principal symptom being hyperkeratosis palmo-plantaris accompanied by severe destruction of the alveolar bone in deciduous or permanent teeth.
We encountered a case of Papillon-Lefevre syndrome showing extremely severe periodontal disease of the entire row of deciduous teeth accompanied by hyperkeratosis palmo-plantaris. This patient was a 2 year,8 months old female with unstability of the deciduous teeth and halitosis as the chief complaints. At the age of about 4 years some deciduous teeth dropped out and because of difficulty in mastication, the remaining teeth were all extracted and dentures were set. Thereafter permanent teeth began eruption and now at the age of 10 years and 7 months 61|6 have already dropped out.
Additionally we discussed 34 cases of this syndrome reported in our country. They involved 17 males and 17 females. It was very interesting that 17 cases out of 34 cases were concerned with consanguineous.

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A female baby,18 months old, developed a Mucocele in her right lower lip and has been under observation after total extirpation of the Mucocele.
The extirpated Mucocele was examined neurohistologically
The results were as follows:
1. The cyst walls showed indistinct borders because of duct rupture and consisted of granulation tissue with slight proliferation of fibrous connective tissue.
2. The cyst contained mucous materials, many plasma cells, and macrophages.
3. The causative salivary duct showed indication of partially becoming a small cyst.
4. Almost no nerve fibers were observed around the causative salivary gland. Away from the gland, the so called sensory nerve bundles showed a tortuous course, swelling, and interruption. Although most nerve fibers had disappeared, some nerve fibers which still remained slightly argyrophil were observed sporadically.
On the basis of the foregoing results and review of the literature, the cause of the present case was postulated to be chronic stimulations accompanying eruption of the anterior deciduous teeth.

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Clinical and statistical studies were performed on 123 cases of ankyloglossia patients who had visited the department of Oral and Maxillofacial Surgery at the Okayama University Hospital during the 10 years from January 1971 to December 1980.
The results obtained and conclusions were as follows:
1) The percentage of children with ankyloglossia under 14 years old was 1%of the total number of patients visiting the department of Oral and Maxillofacial Surgery at the Okayama University Hospital. As the rate of male to female was 6 to 4, there was a more predominant difference among males than among females.
2) As for the difference in age, a high incidence was observed among 1 to 3 year old children, and it decreased with age.
3) The most common chief-complaint was difficulty of speech, amounting to 73 cases (60%).
4) Pediatric patients were the most common, amounting to 35 cases (28%).
5) As for the kind of anesthesia applied, G. O. F. general anesthesia was the most frequently applied, and used in 22% of the cases, and the percentage of children under 3 years of age with general anesthesia was 70%, while under 2years of age it was 90%.
6) As for complications with other main oral diseases, the abnomality of the other frenum was most common, while there was one case each of Riga-Fede disease, labial cleft and palatal cleft.

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We treated a case of a compound odontoma in the vicinity of the lower incisor which changed the positions of the permanent teeth germs. The patient was 8 year 5 month old boy at the time of his first visit. We have also clinically followed-up this case for 4 years and 10 months after extraction of a compound odontoma.
1) Based on X-ray examination, we found that the compound odontoma was close to the apexes of the lower primary lateral incisor and cuspid on the left. In addition 3 or 4 tooth-like pieces were seen.
2) Apparently a granulation with many tooth-like materials were extracted and of which the size was as large as the top of the 5th finger. Also 3 toothlike materials were taken out. Softex X-ray projected more than 20 various sizes of tooth-like solid peices and it was discovered that each peice contained enamel, dentin and pulp cavity.
3) The bone loss after the extraction was almost recovered as well as the other side in 8 months after the extraction and the trabecula was also recognized.
4) The left lower permanent lateral incisor, which was extremely displaced by the compound odontoma recovered its correct horizontal position in 4months after the extraction and the correct vertical one in 1 year 2-6 months compared to the other side.
5) The permanent teeth, which were displaced by the odontoma, erupted in the nomal position without the eruption-inducing therapy.

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The purpose of this study was to evaluate clinically a new type of temporary filling procedure for class II inlay restoration on primary molars. Dislodgement of temporary filling in restoration of class II inlay causes mesial shift of the primary molars, and consequently results in an inability to set the inlay. The required characteristics for temporary filling materials is that they are not dislodged while they are used, however easily removable when necessary, and not harmful to dental pulp.
We developed a new method of temporary filling suitable for class II inlay restoration for primary molars. The method is as follows: Hydroxide base (Procal, Life) is applied to the prepared cavities for the purpose of protection of the pulp and also for making it easy to remove the temporary filling materials, and then composite resin is filled over it. A new method of temporary filling was applied in 60 cases of Class II inlay prepared cavities on human primary molars and observed clinically.
The following conclusions were obtained from this investigation.
1. Dislodgement of the temporary filling was seen in only one case (1.7%) of a 142 day specimen which was an unusually long term for an inlay temporary filling.
2. In most of the cases (52 cases,88.1 %) removal of the temporary filling was easy.
3. The inlay could be set easily in all cases except in one case of dislodgement of the temporary filling.
4. All specimens were found to be clinically asymptomatic both in the teeth and the gingival tissue.
5. The new method of temporary filling for class II inlay restorations for primary molars was considered effective.

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The transfution effects of factor VIII concentrates (Conco-eight) were performed in two cases of hemophilia A whose levels of the antihemophilic plasma factor VIII were less than 2.5 per cent. The factor VIII concentrates must usually be monitored in cases of dental treatment such as tooth extraction for these patients. However, the method of monitoring is very expensive and troublesome work, so we investigated the use of APTT and TEG as the monitoring methods. The folloing conclusions were obtained.:
(1) Among the effects of transfution factor VIII, the values of APTT and TEG were lowest when the factor VIII values were highest.
(2) There were significant positive correlations in both cases between factor VIII and the level of APTT(activity) (p<0.001), while in relation to TEG (r+k) were observed negative correlations (p<0.001). However, there were a few variations in each case respectively.
(3) As a result of the calculation of the level of factor VIII concentrates from the lower normal limits of APTT(70%) and of TEG(r+k=18 minute), the former corresponded to about 30 per cent of factor VIII concentrates and the later was about 20 per cent.

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[in Japanese]

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