Tooth regeneration is one of the final goal of dental science. However, it is difficult to form proper tooth containing enamel, dentin and cementum. In this study, we focused on the function of extrecellular matrix, especially enamel matrix protein, which is essential for the enamel formation.
Ameloblastin is one of the enamel matrix protein secreted by ameloblasts. This involved in the determination of cell polarity, regulation of proliferation and secretion of amelogenin. In ameloblastin null-mutants, severe enamel hypoplasia was observed. This phenotype was similar to human amelogenesis imperfecta. Furteher, the mutant mice developed an odontogenic tumor of dental epithelium origin. Thus, ameloblastin is one of the affected gene of amelogenesis imperfecta, and may inhibit tumor growth of odontogenic tumor as a therapeutic agents.

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We previously reported the effect of the physical properties of different staple foods on masticatory behavior during the course of eating of restored school lunches. The purpose of the present experimental study was to examine whether the difference in the main dish affected masticatory parameters while eating entire school lunch and while eating the food separately.
We prepared three types of the school lunches on the ba sis of the menus of the 1950's in our previous study. As the food which differed among each lunch, we selected fried meat, potato croquette and deep-fried fish, and confirmed that their hardness were significantly different from each other for measuring using texture profile analysis. Fried meat was the hardest followed by deep-fried fish and potato croquette in that order. Nine healthy adult subjects (3 male and 6 female) ate three school lunches on separate days. The total masticatory strokes, the total masticatory time and the total number of ingestion while eating each lunch were calculated using recorded videotapes. The total masticatory strokes, the total masticatory time and the total number of ingestion were nearly the same among the three lunches in terms of mean value for all of the subjects, whereas the total number of ingestion in females was greater than that in males. The total masticatory strokes in females were, therefore, greater than that in males, while the total masticatory time in females was longer.
When the same subjects ate three types of main dish separately, the w eight of one mouthful, the masticatory strokes per mouthful and the masticatory time per mouthful were calculated. With respect to the weight of one mouthful, croquette was the largest among the three foods. The mean weight of one mouthful in males was greater than that in females for all of the food. The masticatory strokes per mouthful and the masticatory time per mouthful, however, did not differ among the three types of food and between males and females.
These results suggested tha t, on ingestion of different foods, the weight of one mouthful was regulated according to each food as the masticatory strokes and the masticatory time per mouthful became approximately constant. This regulation is likely to be performed by the brain on the basis of previous experiences and memories in the anticipatory stage before ingestion of the food.

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We encountered a case of intrusion of an immature permanent incisor caused by trauma. We examined the aspect of the root apex by performing dental treatment and structural mechanics analysis using the finite element method.
The results were as follows:
1. Because there is little effect on the root apex in the case of light tooth intrusion, we felt that we do not particularly need to perform dental treatments so that we let the root apex formation continue.
2. With the example of medium or severe tooth intrusion, we need to apply root apex obliteration so that the apecification of the root apex can be applied for pulp necrosis and the retention of root formation after restoration required due to severe tooth mobility.
We suggest protracted observation of the root ape x as root resorption and root fracture after root apex obliteration occasionally occur.

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Myoblast-lineage cells involved in the development of tongue muscles are known to derive from the occipital somites. The present study aimed at tracing the long-range migration pathway that the myoblast-lineage cells take prior to development of the tongue primordium. For this purpose, we used immunohistochemistry combining both anti-desmin and anti-MyoD antibodies as myoblast-lineage specific markers, as well as Ki 67 as a cell-proliferation marker. ICR mouse embryos at E 9.8 through E 12.3 were subjected to analyzation. A cell migration pathway that initiates in the occipital somites and terminates in the lateral lingual swellings of tongue primordium was monitored on desminimmunostained serial histologic sections prepared from embryos obtained at discrete embryonic days. The results showed that a troop of the myoblast-lineage cells migrating away from the occipital somites was characterized as desmin-positive/MyoD-negative cells with development of lamellipodialike pseudopodia, which we called herein muscle progenitor cells. These muscle progenitor cells were found to take the following route after their departure from the occipital somites: the mesenchyme of body column→the ventral areas of the fourth and the third branchial archs→the medial areas of the second branchial archs. On E 10.3, a leading group of the muscle progenitor cells first reached the medial portion of mandibular processes, where they remained MyoD-negative but lost the pseudopodia to develop mutual cellular contact. On E 11.4, the lateral lingual swellings of the tongue primordium first became discernible in the histologic views. At that developmental stage, MyoD-positive myoblasts started to differentiate within the muscle progenitor population in the mandibular processes. During the period of E 11.4 through E 12.3, the volume of the tissue of the tongue primordium increased rapidly accompanied by the locational shift of myogenic cell population comprising both muscle progenitor cells and myoblasts. These cells exhibited proliferation activities as evidenced by the Ki 67-positive immuno-reaction. On E 12.3 and there after, myoblasts within the tongue primordium started to exit the cell cycle and then to display elongated morphologies prior to myotube formation. On the basis of the present observations, we are now investigating the molecular networks operating to regulate of cell-motility and phenotypic modulation of tongue myoblast-lineage cells.

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The Nippon Dental University School of Dentistry at Niigata has adopted a dual system of teaching since April,2003 as a result of a structural reform. Under the new system, the teaching staff was divided into those who serve as educators and researchers and those who act as educators and clinicians. At the same time, pediatric dentistry and orthodontics were integrated into one, and a new course of study concerning restorative maxillofacial-oral function was added to the curriculum in a move to correspond to the need of reform in dental and medical education. In clinical dentistry, the pediatric dentistry clinic and the orthodontic clinic were merged into a single clinical unit, where staffers are expected to share their knowledge, technical skills and attitudes toward patients. The hospital attached to our university also needs to set up a system that meets the changing requirements of dental health care. It was against this backdrop that we distributed a questionnaire to a total of 280 orthodontic patients visiting the pediatric dentistry / orthodontic clinic asking them about the convenient hours and days of the week of consultations. The following is a summary of our findings:
1. Many patients who visited on weekdays and Saturdays had days off in mind.
2. A majority of patients who visited on weekdays visited on Tuesdays. Asked what day of the week they like to visit the clinic most, those who said they prefer Wednesday accounted for the largest number of the respondents.
3. The most crowded consultation hours were between 4 p. m. and 5 p. m. weekdays and between 2 p. m. and 3 p. m. on Saturdays. The time frames were consistent with what the patients polled wanted. Asked what time they would like to visit the clinic in the future, most of the respondents said they would like to visit on in the late afternoon of weekdays and on Saturday morning.
4. A majority of the patients surveyed could wait 15 minutes to 30 minutes at the longest.
5. The majority said they would not mind if treatment would last 30 minutes to one hour.

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The rapid apatite conversion type calcium phosphate cement (RAC-CPC) becomes high alkalinity when stiffening, and it becomes neutral and shows no stimulation when it changes into hydroxyapatite. The purpose of this study was to evaluate the effects of RAC-CPC on the biological tissue and to evaluate the pH changes of RAC-CPC.
All of the agents (calcium hydroxide, a -TCP,1.7 RAC-CPC (Ca/P: 1.7) and 2.0 RAC-CPC (Ca/P: 2.0)) were applied to the dorsal subcutaneous tissue of rats and the pH values of tissue were measured. The pH changes of all of the agents themselves were also measured. The pH values were statistically analyzed using the Welch's t-test.
The results were as follows:
1) a -TCP kept the surface of dorsal subcutaneous tissue neutral.
2) Calcium hydroxide changed the surface of dorsal subcutaneous tissue to a status of high alkalinity for 2 days.
3) 1.7 RAC-CPC and 2.0 RAC-CPC kept their pH high alkalinity for 60 minutes.
4) 1.7 RAC-CPC and 2.0 RAC-CPC kept the surface of dorsal subcutaneous tissue at high alkalinity for 30 minutes and changed the tissue to neutral.
The biological tissue reacted maintain constancy in pH homeostasis by the action of blood and exudation liquid. Calcium hydroxide however, induced strong reaction to the biological tissue.
It was suggested that RAC-CPC has the ability to the dental pulp stimulates enough to induce the hard tissue formation.

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The aim of this study was to determine the variation in buffer capacity in dental plaque from different areas of the dentition that may be related to the caries status of associated tooth surfaces. Twoday or four-day plaque samples were collected from 8 different sites from each of 15 adult subjects living in Hokkaido; the upper-anterior-buccal(UAB) and lingual(UAL), upper-posterior-buccal(UPB)and lingual(UPL), lower-anterior-buccal(LAB) and lingual(LAL), lower-posterior-buccal (LPB) and lingual (LPL). Wet plaque samples were weighed and 25 mM KCl was added to give a final concentration of 10 mg/ml. The samples were dispersed with a sonication and vortex mixing. A small stir bar was added to the suspension. A micro pH electrode was then placed and the pH was determined. The suspension was then titrated with 10 mM-HCl to pH 3.0. Titration curves were expressed by the 3rd order polynomial (y: pH, x: volume of acid). Statistical analyses among 8 different sites were carried out using the ANOVA and Scheffe test. Statistical analyses among 2-day plaque and 4-day plaque were carried out using the Mann-Whitney U test. The highest pH without acid (initial pH) in 2-day plaque was LAL (7.28±0.36 SD) and the lowest was LPB (653±0.29 SD) with statistical significances (p<0.0001), and the highest pH in 4-day plaque was LAL (7.14±0.30SD) and the lowest was UAB (6.33±0.53 SD) and LPB (6.33±0.41 SD) with statistical significances (p<0.0001). Significant differences were seen in the volume of acid added from pH 6.0 to 5.5, as well as from pH 5.5to 3.0 in both 2-day and 4-day plaque. Plaque associated with the LAL, which is very prone to saliva and less prone to caries, had significantly the highest volume of acid added in the 2-day plaque (pH 6.0-55: 36.16±9.47 SE nmolH+/mg plaque, p<0.05, pH 5.5-3.0: 439.69±55.61 SE nmolH+/mg plaque, p<0.0001), as well as in the 4-day plaque (pH 6.0-5.5: 29.44±4.05 SE nmolH+/mg plaque, p<0.01, pH 55-3.0: 318.33±50.36 SE nmolH+/mg plaque, p<0.001). Compared to the 2-day and 4-day plaque samples, significant differences were seen in the volume of acid added in each. The 2day plaque showed higher than the 4-day plaque in UPB, UPL and LPB(from pH 5.5 to 3.0: p < 0.05).
These facts indicated that mature plaque would show more cariogenecity than immature plaque. These results suggested that site-specific plaque buffer capacity may reflect the differences in exposure to saliva, resulting in differences in local cariostatic challenge.

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The purpose of this study was to develop a computer program for the ability to evaluate the periodontal health status of school children (Development of Ability to Assess Gingival Status of Children, DAAGS-C) for the benefit of the medical staff, and to examine the intra-examiner reproducibility of the assessment by the computer program.
The examination was conducted wi th 34 dentists as the subjects. First of all, standardized color photos for the demonstration of golden standards (G. S. ) were shown to understand the Oral Rating Index for Children (ORI-C). The G. S. for each slide was determined by the agreement with the preventive dentist with 24 years of experience and the pediatric dentist with 17 years of experience. When each intra-oral color slide was shown by a computer, the dentists judged ORI-C level (+2 to - 2) of the 24 color slides one by one. The number of answers showing agreement (coincident with G. S. ), reproducibility (judgment in the same 5 pairs of slides) and extreme answers (apart from two or more margins to G. S. ) were calculated. According to the DAAGS-C criteria, the ability to evaluate the periodontal health status was assessed. The first evaluation was compared with the second evaluation, which was judged at two-weeks intervals without any practice. After the second test completed, questionnaires were filled out.
There were no sign ificant differences in the mean number of answers showing agreement, reproducibility and extreme answers between the first and second test. The results of the present study showed the intra-examiner reproducibility of the assessment by the computer program. Furthermore, approximately 90% of the dentists answered, “The computer program motivates them to understand the periodontal health level”. Further, they answered, “It is necessary to repeat the practice to evaluate periodontal health level by ORI-C”.
In conclusion, the results of this study indicate the intra-examiner reproducibility of the assessment by the computer program and it was suggested that the computer program could be an useful tool to enable not only dentists but also auxiliary dental workers and health educators to evaluate the periodontal health level of children.

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The purpose of this study was to investigate longitudinal changes in the interdental space-arch length relationships for the maxillary arch from the deciduous to the permanent dentition.
Serial dental casts from 10 boy and 10 girl subjects were evaluated. Impress ion and study models were obtained at 2 month intervals from age 3 years to age 15 years.
The interdental spaces, as well as the arch length parameters were measured in the all of the series of the dental casts.
As a result, the amount of interdental spaces in the primary dentition varied according to position; it was largest between the lateral incisor and canine, followed by the central incisor - lateral incisor, canine - first primary molar and between the central incisors. The amount of interdental spaces, in general, decreased with the transition of the dentition; interdental spaces between lateral incisor central incisor and between central incisors temporarily increased with the progress of the eruption of the permanent incisors. Among all of the interdental spaces between the deciduous teeth, deciduous permanent teeth and between permanent teeth, only the space between the first premolar and second deciduous molar showed negative values (overlapping) temporarily. Such crowding was resolved by the exfoliation of the second deciduous molar. The total amount of interdental spaces decreased continuously until 2 months before the emergence of the permanent central incisors, Rapid increase was observed thereafter up to the emergence of central incisors. After that, increasing and decreasing change varied and occurred repeatedly due to exfoliation of the deciduous teeth and eruption of the succedaneous permanent teeth. The amount of interdental spaces gradually decreased from the 6th year after the emergence of the permanent central incisors and diminished on the whole. The total arch lengths increased rapidly from 1 year before the emergence of the permanent central incisors and reached a plateau thereafter.

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Apical periodontitis in a primary tooth can cause various dis orders in the successive permanent teeth. We report a case in which premature eruption and serious imperfect amelogenesis of a permanent tooth were observed cause by apical periodontitis of the corresponding primary tooth and apical periodontitis developing after eruption in the permanent tooth. Root canal treatment was conducted, restorative treatment was undertaken, and the clinical course was followed up.
The patient was a boy aged 5 years and 9 months who visited our hospit al with the chief complaint of toothache, and was found to have gingival swelling over the mandibular left first primary molar tooth. According priority to the preservation of the affected tooth, root canal treatment was conducted and the clinical course was followed up. Nevertheless, the tooth had to be extracted 1 year and 8months later. Extraction of this tooth was followed soon after by premature eruption of the mandibular left first premolar tooth. Looseness and extensive imperfect amelogenesis of the dental crown of this tooth were observed. Two months later, the patient came back with the chief complaint of toothache, and examination revealed swelling of the mandibular left first premolar tooth. A diagnosis of acute apical periodontitis was made. A calcium hydroxide preparation was applied after administration of anti-inflammatory drugs, hoping for closure of the apex. As a result, growth of the dental root of the mandibular left first premolar tooth and closure of the apex with hard tissues were observed. Abutment was subsequently constructed within the root canal using composite resin and fiber post, followed by fixation of a hard resin jacket crown. The child continues to be observed.
In this patient, apical periodontitis in a preceding primary tooth affected the formation of the successional permanent tooth and also the permanent dental arrangement. This experience suggests that it is important to investigate the status of infected premature permanent tooth and to choose the best approach for treatment, while taking the prognosis into consideration.

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Sturge-Weber syndrome is a rare neurological disorder of unknown incidence and origin. This syndrome is usually indicated by a birthmark somewhere on the face, usually involving the eye and forehead, also similar blood vessels on the brain, called angioma. A mouth guard is an appliance worn in the mouth, which helps to prevent injuries to the teeth, lips, cheeks, tongue, and jaw.
This report concerns the good prognosis obtained from treatment using a mouth guard. Good results were obtained with application other than for sports. A mouth guard was made at the request of a child 8 years and 3 months of age for use for the Judo. The mouth guard was used well as during Judo practice as well as during treatment for Sturge-Weber syndrome.
The patient, a male, suffered from severe maxillary protrusion which originated in the hemangioma on the bilateral incisors and bilateral canine area of the maxilla. A custom made mouth guard of modified lamination type was used. This patient was regularly underwent laser treatment to the hemangioma under general anesthesia.
The anesthesiologist considered the mouth guard to be effective in preventing tooth injuries through misharp during endotracheal intubations under general anesthesia. The mouth guard was found to be useful not only for prevention of injury during sports practice but also to prevent injury during endotracheal intubations under general anesthesia.

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