To determine whether cortical negative potential (hereafter referred to as CNP), which was recorded from the scalp (sites: T3, CZ and T4), preceding the right-side chewing is affected by input from the periodontal membrane, the CNP and pattern of the appearance of masseter electric discharge before the anesthetization of the apex of the tooth root and those after the anesthetization were compared.
1) CNP preceding the right-side chewing appeared at T4 early both before and after the anesthetization and showed a maximum amplitude immediately before masseter electric discharge. CNP duration and amplitude increased after the anesthetization as compared with those before the anesthetization.
2) The initial increase in electromyogram associated with chewing became sharper after the anesthetization than before the anesthetization.
From these findings, that the cerebral cortex is in a preparatory state at an early stage when the sensation in the periodontal membrane on the chewing side is blocked, and that, as a consequence, strong chewing is produced.

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To determine whether cortical negative potential (hereafter referred to as CNP), which was recorded from the scalp (sites: T3, CZ and T4), preceding the right-side chewing, is affected by the pattern of the appearance of masseter electric discharge, difference of strong and weak chewing with CNP appearance were compared. In the case of strong chewing, CNP appeared early, and its amplitude increased as compared with the results in the case of weak chewing. From this result, we related that CNP amplitude is related to the chewing output.

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For effective mastication and swallowing, to take optimum mouthful food regularly is necessary. The purpose of this study is to compare the weights and the variance of a mouthful food between children and adults. We studied mouthful weight and the coefficient variation in 5-year-old children (n = 10), 8-year-old children (n = 10) and adults (n = 10) while they were eating rice, bread, sausage and apple on two different days. The test foods were served in random order 2-4 hours after lunch. Each portion was weighed before and after each bite to measure the mouthful weight, and the weight of the last bite of each portion was eliminated from the data. The mean weight and coefficient variation in each subject were calculated. The results showed the mean weight was largest in the adults, intermediate in the 8-year-old children, and smallest in the 5-year-old children for all test foods (ANOVA). Moreover, the mean coefficient variation among the weights of the groups revealed that mouthful weight within an individual varied most widely in the 5-year-old children and most narrowly in the adults, and that 8-year-old children could show the same coefficient variation of mouthful weight as adults in rice and apple (Steel-Dwass test). Our results suggest that mouthful weight becomes larger and more regularly with age.

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This study establishes a new measurement method for quantification of mouse gutter shaped root (GSR). To evaluate GSR, we made clear the completion period of root formation by continuous observation from 9 days after birth to 82 days using a micro-CT. We observed that the mouse root formation is complete at 35 days after birth. We established a schema to evaluate the Dental Root Fusion Rate (DRFR) on a CT image and we could evaluate DRFR as a quantitative trait using this image. Consequently we could establish a new method for measurement of mouse gutter shaped roots as a quantitative trait.

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We first conducted a questionnaire study about the development of mastication of EVLBW (extremely low and very low birthweight) infants aged 2 to 4 years in 1998, and results showed that they tended to “dislike of firm foods”, to be “picky eaters” and to have “trouble swallowing foods with a mouth full of food/drink”, when compared with the normal birthweight (NBW) infants. The purpose of the present study is so designed to investigate moreover the development of masticatory function, the oral and facial shape, dental problems, and the relationship between systemic growth and these issues in EVLBW infants. We carried out a follow-up questionnaire study 5 years later in 2003 and compared current masticatory function among EVLBW infants, the low birthweight (LBW) and NBW infants. A significantly higher number of EVLBW infants were considered to be “small eaters”, but no differences were found in the items: “picky eating”, “dislike of firm foods” and “trouble swallowing foods with a mouth full of food/drink”. This differed from a study conducted 5 years earlier. The guardians of the EVLBW infants were worried about language delay significantly and still worried about the shape of the child’s head and face significantly more often. No significant differences were found in the results of dental screening in school. In conclusion, the guardians of the EVLBW infants felt that masticatory problems decreased as their children grew. The EVLBW infants were suggested to catch up with normal infants in masticatory function by early school age.

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The purpose of the present study was to investigate changes with age in the occlusal force and the masticatory muscle activity in extremely low birthweight (ELBW) and very low birthweight (VLBW) infants, longitudinally. The subjects were eight EVLBW (ELBW and VLBW combined) infants in Hellman’s Dental Stage IIA (mean age: 5 years and 0 months) and IIIA (mean age: 8 years and 3 months), and as controls eleven full-term infants who visited the Pediatric Dental Clinic of Asahi University for dental checkups (IIA: mean age 5 years and 4 months, IIIA: mean age 8 years and 3 months). The occlusal force of EVLBW infants at dental stage IIA was 266.4 N and different from the standard value of 391.8 N, however, no difference was observed between EVLBW infants (565.2 N) and the standard value (520.0 N) at dental stage IIIA. Total muscle activity reduced with age and showed a tendency to be closer to the values of full-term infants. When changes with age in occlusal force and total muscle activity of EVLBW infants were investigated, occlusal force increased with age but total muscle activity decreased with age, suggesting a negative correlation. In conclusion, the results of the present study show that they gradually gain on the full-term children in masticatory function by the time of the deciduous dentition period, therefore, it is considered that problems in relation to eating behavior are temporary and that delayed masticatory function is normalized before catching up with the full-term children in systemic physical growth, i.e., 8 to 15 years of age.

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This study was performed to observe the dental hard tissue of newborn rats after their mothers were administered demethylchlortetracycline (DTC) during pregnancy. Undecalcified ground sections were observed by microradiography, and tetracycline-stained tooth was determined by ultraviolet light. The mineralization pattern and the element distribution in the enamel and dentin of the colored tooth were analyzed using an electron probe X-ray microanalyzer (XMA). Decalcified serial sections were stained with hematoxylin and eosin (HE). The results obtained showed that tetracycline caused abnormalities in the enamel and dentin formation. The longer period of tetracycline administration was tended to be associated with more pronounced coloration, and this was associated with the moderate alteration of calcification in some areas of the enamel and dentin, as observed on contact microradiograms (CMR). The Mg levels were higher, while those of P were lower for the DTC experimental groups than the control group. However, the Ca levels were comparable between the experimental and the control groups.

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The aims of this report were to determine the nature of eruption disturbances and to establish the pattern of management for these teeth in a group of Japanese children and adolescents. Data were collected from the clinical records of patients in the Pediatric Dental Clinic of Niigata University Medical and Dental Hospital. There were 700 patients (364 males and 336 females) and 748 teeth (26 primary teeth and 722 permanent teeth) who were treated for eruption disturbances between 1979 and 2002. During this period, 17,365 new patients visited the clinic, of whom approximately 4% had eruption disturbances. The most frequently affected permanent teeth were the maxillary central incisors (38.6%), followed by the maxillary canines (15.4%). Of the permanent teeth, 52.5% were in males and 47.5 % in females. Although there were more cases of maxillary central incisors in males than in females, the number of cases involving maxillary canines was higher in females. Whereas delayed eruption was noted in 76.7% of maxillary central incisors, 18.6% were impacted and 4.7% demonstrated abnormal direction/position which required treatment. In contrast, a higher percentage (64.8%) of maxillary canines that showed abnormal direction/position was treated. Eruption disturbances were found in 40% of the patients during routine examinations. This suggests that regular routine examinations are important for pediatric dentists to detect and treat eruption disturbances early.

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Using an air-abrasive cutting apparatus, cavity preparation of dentin and artificially softened dentin was performed using alumina or chitin-chitosan grains as cutting media. As a result of scanning electron microscopic observation, the following findings were obtained:
1. In cutting specimens that showed high values for Knoop hardness, alumina grains exhibited excellent cutting effects.
2. Regarding specimens after decalcification for each duration, the amount of cutting was significantly larger with alumina grains than with chitin-chitosan grains.
3. Regarding specimens cut using chitin-chitosan grains, the deepest cavity preparation was obtained in the specimens decalcified for 12 hours.
4. Healthy dentin was effectively cut by the ejection of alumina grains, whereas artificially softened dentin was effectively cut by the selective use of chitin-chitosan grains.
5. Adhesion of a large amount of chitin-chitosan grains in the wet dentin specimens was observed.
6. The amount of chitin-chitosan grain adhesion was the largest in the wet dentin specimens decalcified 12 or 24 hours.

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Since 1972, we have been conducting an annual clinical dental examination for young children at 13 nursery schools in the north district in Sendai, Japan. In the present study, we have included the results of examinations conducted in 1997 and 2002, and analyzed the time trends in caries experience of the primary dentition over a 30-year period from 1972 to 2002. The caries experience in the primary dentition markedly decreased in 1977 and remained stable for about 15 years, but in 1997, it markedly decreased again and continued to decrease in a linear fashion until 2002. The time trends in caries experience in the primary dentition in each age group were further analyzed by ascertaining caries experience in each tooth type. The results showed that, in 2 to 4-year-old, the decrease of caries experience for the primary maxillary incisors, canines and first molars seemed to stop decreasing in 2002, but for the 5-year-old, the caries experience for the maxillary incisors and canines and the maxillary and mandibular first and second molars markedly decreased from 1997 to 2002.

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The purposes of this study were to determine the applicability of Moyers and Tanaka-Johnston prediction methods for Indonesian Javanese children, and to develop new regression equations for predicting the size of the canine-premolar segment based on the normative standard of mesio-distal crown diameters of the permanent teeth in Indonesian children. Two hundred and eighty five sets of dental casts of the permanent dentition were obtained from Indonesian Javanese children in Yogyakarta, Indonesia during 2000-2001. There were 143 males and 142 females aged 11.1 to 14.9 years. The mesio-distal crown diameters were measured with calipers to an accuracy of 0.05 mm. The statistical analyses were performed using computer software (SPSS 9.0 for Windows). This study confirmed that the use of Moyers and Tanaka-Johnston prediction methods for mixed dentition analysis among Indonesian Javanese children were unsuitable. Both methods underestimated the size of canine-premolar segments, with exception of the Tanaka-Johnston method in females. The combination of maxillary first molars and mandibular lateral incisors (Σ 6 2 2 6 ) showed relatively higher correlation with the actual size of Σ 3 4 5. The development of new linear regression equations with predictor Σ 6 2 2 6 for predicting the size of the canine-premolar segment was based on the normative standard of mesio-distal crown diameters of permanent teeth in Indonesian Javanese children. The newly developed regression equations are more accurate than the regression equation that uses predictor Σ 2 1 1 2 for mixed dentition analysis among Indonesian Javanese.

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OBJECTIVE: To investigate the maternal environment influence on cortisone-induced cleft palate in mice. METHODS: The A/WySn and the C3H/He strains of mice were used. Pregnant mice were injected on days 11 through 14 of gestation with 2.5 mg/mouse/day of cortisone. The A/WySn, C3H/He, F₁ hybrids and N₂ backcross fetuses that attained at least day 18 of development were checked for the presence of cleft palate. RESULTS: The frequency of fetuses with cleft palate and the ratio of dams bearing fetuses with cleft palate in the A/WySn strain (40.6% and 67.7%) were both significantly higher than those in the C3H/He (16.7% and 44.4%), F₁ (12.4% and 47.1%) and N₂ (24.0% and 55.3%) mice. The highest frequency of cleft palate was observed when the litter size was 8 in A/WySn, 7 in C3H/He, 8 and 9 in F₁, and 9 in N₂, respectively. CONCLUSION: The results suggested that the reaction to cortisone-induced cleft palate is different from the A/WySn and C3H/He strains of mice. The A/WySn strain of mice was more susceptible than the C3H/He strain of mice. The data suggest that litter size might play a role in defining cleft palate frequency.

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The aim of this study was to assess risk behaviors and its association with caries activity and dental caries in Japanese children. The subjects were 392 young Japanese children who underwent dental health check-up at 18, 30 and 42 months of age. Oral examinations, Cariostat tests and dental health questionnaires were carried out at each time. The caries prevalence of children was 1.5% at 18 months, 9.9% at 30 months and 28.1% at 42 months. Caries activity based on the Cariostat scores of children was correlated with caries status (caries-free/carious) at 42 months. In children with caries during each examination period at 42 months, eating snacks while playing was ranked as the most important behavioral risk (P < 0.001), followed by breast-feeding (P < 0.01), non setting of time for snacks (P < 0.05) and frequency of snacks (P < 0.05) at 18 months old; non brushing by mother (P < 0.05) and eating snacks while playing (P < 0.05) were ranked highest at 30 months old. In addition, eating snacks while playing (P < 0.001) at 42 months old was the only a significant factor for children with caries. Caries activity and risk behaviors were associated with caries experience at different age periods of childhood.

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We conducted research as part of a series of studies on the influence on various oral tissues of the offspring of mothers that were given methamphetamine (MA) during pregnancy. The mandibular strength during the growth process of newborn rats from mothers that had received MA was compared with normal newborns. Methamphetamine hydrochloride was continually administered to mother rats (MA group) every day from conception to the day before delivery. Observations of the newborn were made at birth, two, three, four and five weeks. Newborn rats from mothers who had been administered the same amount of physiological saline solution were used as controls. Peripheral quantitative computed tomography (pQCT) was used to measure bone strength to determine bone mineral density and bone structures. A complete determination was made after soft X-ray photography of the mandible. No significant difference was observed in mandibular growth from the menton to the gonion between the MA and the control groups throughout the experimental period. Although no difference was noted in trabecular bone, a significant difference was seen in cortical bone, which tended to become thinner in the MA group. In addition, the cortical bones in the MA group showed lower values for bone mineral density and bone mineral content compared with those in the control group. We concluded that the mandibular strength of neonatal rats of mothers that had received MA was weak, and could break easily compared with normal infants. These results indicate that the problems of female methamphetamine drug users extend to influence on the oral hard tissue formations of their offspring.

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A 10-year-old boy was referred to our pediatric dentistry clinic with complaints of anterior crossbite and crowding in the maxillary dentition. Most of his molars were severely decayed and the level of his oral hygiene was very poor. A removable orthodontic appliance was used to correct his anterior crossbite. The use of this appliance enabled us to treat the patient’s severely decayed molars and improve the poor level of his oral hygiene simultaneously.

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We examined 2 patients with filling material extruded from root canals of their primary teeth that remained for a long time. In Case 1, 3 separate small radiopaque masses were initially identified below the mandibular right second primary molar at the age of 7 years 6 months old and the patient was followed for approximately 7 years. The permanent successor was congenitally absent and the radiodensity of the masses decreased as the patient matured, though they were still apparent 7 years later. In Case 2, a large radiopaque mass was detected in the crown region of the permanent central incisor of a patient aged 5 years 2 months old, which had come from the root canal of the corresponding primary tooth that had been filled with iodoform calcium hydroxide paste. The radiopaque filling material in the root canal and the large mass seen superimposed on the crown of the permanent successor had apparently become separated. The mass became smaller and nearly disappeared 1 year 6 months later. In both cases, the root canal filling materials were speculated to have been extruded from the root apex. Differences in features of the radiopaque masses are discussed in this report.

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Supernumerary teeth are often seen in daily clinical practice in pediatric dentistry. To investigate the role of genetics, we carried out a case control study. The study population consisted of 103 males and 184 females and their mean ages were 8.31±3.03 (age range: 3 to 18). The patients with supernumerary teeth were diagnosed by radiography. For the control groups, the absence of supernumerary teeth was confirmed by panorama radiographs and interviews with the patients’ parents about past treatment of the supernumerary teeth in other dental clinics. The presence or absence of supernumerary teeth in other family members was also investigated by the questioners. A total of 287 patients were analyzed. If supernumerary teeth existed in either of the parents, the odds ratio was 5.989. This result indicated that genetics may play some role in the occurrence of supernumerary teeth.

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The caries-preventive effect of fluoride is well known. The widespread use of fluoride-containing toothpastes and mouthrinses has been recommended to reduce dental caries. Many kinds of fluoride containing toothpastes are available in Japan. However, only two kinds of mouthrinses which contain fluoride are comically available. The aim of this study was to investigate the current status of fluoride-containing mouthrinses on the market in three European countries. Fluoride-containing mouthrinses were purchased from retail outlets in Athens, Amsterdam and Geneva. The labels of ingredients were studied to determine the type and concentration of fluoride. Most of the mouthrinses contained sodium fluoride (90%); some contained stannous fluoride (5%) or potassium fluoride (7%). The concentrations of fluoride ranged from 100 ppm to 500 ppm.

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