Descriptive study of dental injury incurred by junior high school and high school students during participation in school sports clubs.

AIM: Students often injure their teeth during participation in school-based sports clubs. This study examined the frequencies and types of dental injuries sustained at school sports clubs and compared the risk of dental injury among different sports. METHODS: Based on injury statistics from the Japan Sport Council of the junior high schools and high schools in seven prefectures during fiscal year 2006, the risk of dental injury was estimated using a rate ratio (RR) by calculating the ratio of occurrence of dental injury under various circumstances. RESULTS: The RRs of exercise-related dental injury for boys and girls in junior high school were 0.7 (P < 0.001) and 1.3 (P < 0.05), respectively, and for those in high school were 2.6 (P < 0.001) and 2.7 (P < 0.001), respectively. In junior high school, softball (RR = 7.7) for boys and handball (RR = 3.9) for girls commonly led to dental injuries. In high school, Japanese-style wrestling (RR = 18.5) and rugby (RR = 7.3) for boys and handball (RR = 6.5) for girls had high risks for dental injury. Crown fracture was the predominant dental injury among boys and girls attending both junior high school and high school. The proportion of alveolar fracture was higher in school sports clubs than outside school sports clubs among high school boys. Contact or limited-contact sports had significantly higher risks for dental injuries than did noncontact sports. CONCLUSION: The results of this study suggest that teachers and administrators at schools should pay attention to the risk of dental injury among students participating in high-risk sports.

Tooth loss and risk of hip fracture: a prospective study of male Japanese dentists.

OBJECTIVES: To determine whether the number of teeth lost can predict the risk of subsequent hip fracture. METHODS: We followed up 9992 male Japanese dentists aged 50 years or more (mean age ± standard deviation [SD], 61.1 ± 9.6 years) for incidence of hip fracture. From 2001 through 2006, they completed a baseline questionnaire on lifestyle and health factors including the number of teeth lost (excluding third molars). Incidence rate ratios (IRRs) were estimated by fitting proportional hazard models. RESULTS: During the mean follow-up period of 6.0 years, 20 new cases of hip fracture occurred. Participants who had lost 15 or more teeth at baseline were at a significantly increased risk of hip fracture: the multivariate-adjusted IRRs were 4.1 (95% confidence interval [CI], 1.2-14.2) for loss of 15-27 teeth and 4.5 (1.1-18.0) for edentulousness relative to loss of 0-14 teeth (trend P, 0.028). Overall, the risk of hip fracture was weakly associated with the number of teeth lost: the IRR per tooth was 1.06 (95% CI, 1.01-1.12). CONCLUSIONS: Tooth loss was slightly associated with a higher risk of subsequent hip fracture. The number of teeth lost might be informative in predicting this risk.

Comparison of clinical practice education in dental hygiene schools in eight countries.

OBJECTIVES: The profession of dental hygienist is one of the few in which the primary function of the practitioner is to prevent oral disease and to promote the well-being of patients. The aim of this study was to investigate clinical training conditions in schools of dental hygiene in eight countries (the USA, Canada, the UK, Sweden, Denmark, Thailand, South Korea and Japan). METHODS: In 2006, we sent out a questionnaire in which we asked dental hygiene schools about how they educate dental hygiene students. RESULTS: The techniques taught to students in schools in Western industrialised nations, such as the USA, Canada, Denmark, the UK and Sweden, were mainly related to dental preventive measures and dental health guidance. By contrast, training schools in South Korea and Japan placed less emphasis on dental preventive measures and dental health guidance. Dental hygienists in Thailand are trained to perform local anaesthesia and to fill and extract deciduous teeth although the country does not have a specific qualification system. CONCLUSIONS: The contents of clinical training and education in schools of dental hygiene differ greatly among countries.

Impact of interocclusal contacts on infrared laser fluorescence in pits of sound first permanent molars in children.

BACKGROUND: A device based on infrared laser fluorescence (IRLF) has become available as an adjunct for the diagnosis of dental caries. AIMS: The objective of this study was to clarify the differences of IRLF readings in the mesial, central and distal occlusal pits of first permanent molars. DESIGN: Sixty-four children (average age 8.0 years) were examined using IRLF. The mesial, central and distal pits of clinically healthy first permanent molars were measured. The instrument provides measurements in arbitrary units on an open-ended interval scale. RESULTS: Mean (± SE) IRLF values in the mesial pits were 4.9 ± 0.4 (upper) and 6.5 ± 0.4 (lower) and were significantly lower than those in the central (8.8 ± 0.6 and 11.5 ± 0.9) and distal (9.6 ± 0.7 and 10.4 ± 0.8) pits in the maxilla and mandible. There was no significant difference between the right (7.3 ± 0.5, 9.4 ± 0.6) and left (8.2 ± 0.5, 9.5 ± 0.6) dental arches. IRLF measurements in the mesial pits of human first permanent sound molars were lower than the central and distal pits in children whose second molars had not erupted. CONCLUSIONS: The inherently higher IRLF values of some sites should not be misinterpreted and trigger early invasive treatment.

Quantitative evaluation of the oral biofilm-removing capacity of a dental water jet using an electron-probe microanalyzer.

OBJECTIVE: This study was conducted to evaluate the oral biofilm-removing capacity of a dental water jet (DWJ) by measuring biofilm thickness using an electron-probe microanalyzer (EPMA). METHODS: Thirty consenting subjects wore in situ plaque-generating devices, which consisted of a pair of 4mm(2) enamel slabs attached to the upper molars for 2 days. Each device removed from the mouth was clamped, and one of the slab surfaces was treated with the DWJ, irrigating it for 5s. The devices were randomly assigned to three different pressure settings of 707, 350 or 102kPa. Another slab with no treatment served as a control. Each slab was freeze-dried, sputter-coated with platinum, and examined using secondary-electron imaging. The slabs were then embedded in methacrylate and cross-sectioned in the centre. Their surfaces were polished, coated with carbon, and examined using backscattered electron compositional (COMPO) imaging. The area between the enamel and the outer biofilm surface, indicated by a thin platinum layer, was measured by COMPO imaging to calculate the average thickness of the biofilm on the specimen. RESULTS: The removal capacity of biofilm by irrigation was estimated using a reduced rate of biofilm thickness, which was calculated from the differences between a pair of treated and control slabs. The reduced rates were 85.5% at 707kPa, 85.1% at 350kPa and 63.4% at 102kPa, indicating that biofilm thickness was significantly reduced at every pressure setting. CONCLUSIONS: The results suggest that irrigation using a DWJ would be an effective means of plaque control.

Recent trends in sugar content and pH in contemporary soft drinks.

PURPOSE: The purpose of this study was to determine the content of sucrose, glucose, total sugar, and pH in a range of popular contemporary Japanese soft drinks and compare their changes in different periods. METHODS: The pH value and content of sucrose and glucose of popular Japanese soft drinks were determined, and this study's results were compared with the previous data of beverages in 1978, 1981, 1985, and 1997. RESULTS: Coffee drinks showed the highest content of sucrose, while carbonated diet drinks showed the lowest. Energy drinks showed the highest content of glucose and total sugar, while carbonated diet drinks showed the lowest. Coffee and energy drinks showed the highest and lowest pH levels, respectively. The total sugar content of a soft drink has remained unchanged over the years, but the sucrose content of soft drinks has decreased over the years. CONCLUSIONS: All drinks showed pH values below 7, with a very wide variety of sugar content; sugar content of soft drinks has generally decreased since the 1980s in Japan.

Remineralization of primary tooth enamel from individuals with Down syndrome.

PURPOSE: The purpose of this study was to clarify the characteristics of primary tooth enamel of Down syndrome patients (DSPs). We examined 9 primary teeth of Down syndrome children and 11 primary teeth of normally developed children to investigate the remineralization processes of enamel by transverse microradiography and X ray micro analyzer (XMA). METHODS: Mineral loss, lesion depth, maximum mineral value, minimum mineral value, depth of maximum mineral value, and depth of minimum mineral value were used to analyze transverse microradiography (TMR). In addition, we calculated the percentage of enamel remineralization. RESULTS: All the parameters in the 2 groups showed marked recovery. The results indicated that the Down syndrome group was significantly remineralized the same way as the control group. According to the comparison of mineral content distribution by XMA, the content distribution of magnesium was different between the 2 groups. CONCLUSION: While recovery through remineralization of primary teeth was similar between Down syndrome children and normally developed children, the mechanism of remineralization process may be different between the 2 groups; consequently, magnesium may be considered as one of the factors affecting recovery.

Is there a relationship between periodontal disease and smoking after adjusting for job classification in Japanese employed males?

OBJECTIVES: The objective of this study is to examine whether the well-known association between periodontal disease and smoking persists after adjusting for job classification. METHODS: A sample of 16,110 employed Japanese males aged 20-69 years was included in the study. Periodontal examinations were conducted using the Community Periodontal Index. The association between periodontal disease and smoking status was examined using logistic regression adjusting for age, diabetes and job classification. Job classification was based on criteria of the Japanese Ministry of Health, Labour and Welfare. There are nine major job groups: (1) Professional (professionals, specialists), (2) Managers, (3) Office workers (computer operators, clerks, secretaries), (4) Skilled worker (factory workers, construction workers), (5) Salesperson (shop assistants), (6) Service occupations (superintendents, cleaners or car park attendants), (7) Security (guards), (8) Farmers and fishermen, (9) Transport and telecommunication workers (truck drivers). RESULTS: Current and former smokers were more likely to have periodontal disease than non-smokers. Adjusting for job classification attenuated the association between smoking and periodontal disease but did not eliminate the association. The odds ratios for the association between smoking and Community Periodontal Index score 3 or 4 attenuated from 2.25 to 2.04 and from 2.62 to 2.52 for individuals aged 20 to 39 and 40 to 69 years, respectively. The effect of job classification on the association between periodontal disease and smoking was higher among younger participants aged 20 to 39 years. CONCLUSIONS: Smoking persisted as an important determinant of periodontal disease after adjusting for job classification in Japanese employed males.

Tooth loss and intakes of nutrients and foods: a nationwide survey of Japanese dentists.

OBJECTIVES: To clarify the association of tooth loss with dietary intakes among dentists, for whom sufficient dental care is available. METHODS: We analyzed the data from 20 366 Japanese dentists (mean age +/- SD, 52.2 +/- 12.1 years; women 8.0%) who participated in a nationwide cohort study from 2001 to 2006. The baseline questionnaire included a validated food-frequency questionnaire to estimate intakes of foods and nutrients. We computed the geometric means of daily intakes by the number of teeth, adjusting for age, sex, smoking, physical activity, and history of diabetes. RESULTS: The mean intakes of some key nutrients and food groups, such as carotene, vitamins A and C, milk and dairy products, and vegetables including green-yellow vegetables, decreased with the increasing number of teeth lost (P for trend <0.05). On the contrary, mean intakes of carbohydrate, rice, and confectioneries were increased among those with fewer teeth (P for trend <0.05). The difference in the geometric mean (%) between totally edentulous subjects and those with > or =25 teeth, that is [(Geometric mean for > or =25 teeth) - (Geometric mean for 0 teeth)]/(Geometric mean for > or =25 teeth) x 100, was 14.3%, 8.6%, 6.1%, and -6.1% for carotene, vitamin C, vitamin A, and carbohydrate, respectively. For food groups, it was 26.3%, 11.9%, 5.6%, -9.5%, and -29.6% for milk and dairy products, green-yellow vegetables, total vegetables, rice, and confectioneries, respectively. CONCLUSIONS: Tooth loss was linked with poorer nutrition even among dentists.

Average daily intake of phosphorus in 3- to 5-year-old Japanese children as assessed by the duplicate-diet technique.

The present study aimed to determine whether there is excessive mean daily intake of phosphorus in 3- to 5-year-old Japanese children and to ascertain relationships between phosphorus intake and various food and beverage groups. Subjects comprised of 90 children, with 15 boys and 15 girls in each age group from 3 to 5 years. The duplicate-diet technique was used to ascertain total dietary intake, including snacks and beverages over a 24-h period on 3 separate days from summer 1999 to winter 2000. After wet ashing food samples, phosphorus was quantified by colourimetry using a spectrophotometer. Median and 25th-75th percentile daily phosphorus intake for 3- to 5-year-old Japanese children was 674 mg (534-890 mg), and phosphorus intake correlated with the intake of many food groups and was closely correlated with total daily intake of food and beverage (rs=0.64). In addition, phosphorus intake correlated with the intake of magnesium and calcium (rs>=0.6, p<0.001). When assessed based on dietary reference intakes for the US, maximum intake did not exceed the tolerable upper intake level in any of the young children, but phosphorus intake was not more than the estimated average requirement (EAR) in 4.4% of subjects, which exceeded the target of 2.5% for the US EAR. We concluded that there is a risk of insufficient phosphorous intake, rather than excessive intake, for 4.4% of 3- to 5-year-old Japanese children.

Relationships between mandibular cortical bone measures and biochemical markers of bone turnover in elderly Japanese men and women.

OBJECTIVE: The aim was to clarify the association between dental panoramic radiography measures of mandibular inferior cortical shape and biochemical markers of bone turnover in elderly men and women. STUDY DESIGN: Subjects were 80-year-old men (n = 85) and women (n = 153). Mandibular cortical shape and width were evaluated on dental panoramic radiographs. Bone formation and resorption, respectively, were estimated by serum levels of carboxy-terminal propeptide of type I collagen (PICP) and serum type I collagen carboxy-terminal telopeptide (ICTP). RESULTS: Eroded cortices of the mandible were significantly associated with increased serum PICP levels (P = .005) in women. Lower mandibular cortical width quartiles were also significantly associated with increased serum PICP levels in men (P = .020) and women (P = .006). CONCLUSIONS: Mandibular inferior cortical measures detected on dental panoramic radiographs may be associated with bone formation rates and be useful in predicting osteoporosis in elderly Japanese men and women.

Analysis of risk factors for dental caries in infants: a comparison between urban and rural areas.

OBJECTIVES: This study investigated the incidence of caries in infants and explored the risk factors related to noteworthy variations between urban and rural areas. METHODS: Subjects were 232 infants (111 males and 121 females) aged 1.6 and 3 years born in "N" town between the fiscal years of 1997 and 2001. Infants aged 1.6 and 3 years had 99.6 and 100% participation in health checkups, respectively. Of the total, 148 and 84 infants were living in the urban and rural areas, respectively, of "N" town. RESULTS: Caries incidence and the average number of carious teeth (decayed/missing/filled teeth, dmft) for infants aged 1.6 years were significantly higher in the rural area than in the urban area, indicating that environmental factors that predispose infants to develop dental caries exist in the rural area. In addition, logistic regression analysis for infants in each of the two areas revealed that risk factors of the child-care environment, for example living with grandparents and brushing by parents, stood in marked contrast with each other. Moreover, the odds ratio of the risk factor dozing off while drinking showed a marked difference between the areas, although this risk factor was common in both areas. CONCLUSIONS: The results of this study indicated that several factors of the child-care environment, for example the daytime caring person, are related with caries development. Scientific elucidation of the risk factors that give rise to high prevalence of caries in specific regions and access to the whole picture of the disease mechanism may have great potential to lead to the development of effective countermeasures and to contribute to the reduction of dental caries in preschool children.

Temporal association of elevated C-reactive protein and periodontal disease in men.

BACKGROUND: Most studies on the relationship between serum C-reactive protein (CRP) and periodontal disease have been cross-sectional. In this study, we investigated the temporal association between CRP and periodontal disease by following a large number of subjects for 1 year. METHODS: We studied 11,162 men in Nagoya, Japan, who had an initial dental examination as part of a complete physical examination and then underwent the same examination 1 year later. For the 4,997 men without periodontal disease at baseline, logistic regression analysis was performed to examine the relationship between baseline CRP and periodontal disease 1 year later, adjusting for age, body mass index, glycosylated hemoglobin A1c level, and smoking status. Similarly, logistic regression analysis was performed to examine the relationship between periodontal disease at baseline and CRP 1 year later for the 10,376 men with normal baseline CRP, adjusting for the same confounding factors. RESULTS: Among men without high CRP at baseline, periodontal disease at baseline correlated to CRP 1 year later. The odds ratio was 1.336 (95% confidence interval [CI]: 1.115 to 1.674). However, in the men without periodontal disease, no significant correlations were seen with baseline CRP or periodontal disease 1 year later. The odds ratio was 1.163 (95% CI: 0.894 to 1.513). CONCLUSION: Periodontal disease increased the risk for high serum CRP levels in men after 1 year of follow-up.

[A pilot study to develop a screening system and maltreatment index for elementary schoolchildren focusing on daily habits and dental caries].

OBJECTIVE: In recent years, the number of consultations for maltreatment cases has been increasing in Japan. The characteristics of maltreated children are important factors for their identification. In an earlier paper, we analysed the daily habits related to maltreated children. In the present study, the objectives were to assess the relative weights of each factor and score the daily habits and treatment percentages for dental caries, and also to develop a screening system to find maltreated children. METHODS: The subjects of this study were 57 elementary schoolchildren who were given temporary protection by the child social welfare authorities. The control group comprised 575 elementary schoolchildren. Multiple logistics regression analysis was used to calculate scores for each item derived from partial correlation coefficients. RESULTS: Two versions of a maltreatment index for elementary schoolchildren (MIES) were developed, a daily habits version (H) and daily habits and treatment percentage of dental caries version (HD) for the 1st to 3rd grades (G1-3) and the 4th to 6th grades (G4-6). The MIES for G1-3H was: Do you brush your teeth before bedtime (3 points); Do you know that the first molars are important for chewing (2); Have you used a fluoride gel or mouth rinse (2); Do you have any hobbies except video games (2); Do you know the differences between permanent teeth and milk teeth (1). The MIES for G1-3HD were: Have you used a fluoride gel or mouth rinse (4); Do you brush your teeth before bedtime (3); Do you wash your hands after you play outside (2); Is the number of untreated deciduous teeth larger than the number of treated deciduous teeth (1). The MIES for G4-6H were: Do you wash your hands after you play outside (4); Do you brush your teeth after breakfast (3); Do you brush your teeth before bedtime (3). The G4-6HD were: Do you brush your teeth before bedtime (3); Do you wash your hands after you play outside (2); Is the number of untreated permanent teeth greater than the number of treated permanent teeth (1). The availability (sensitivity + specificity) of MIES HD was higher than MIES H when the original values were substituted into MIES. CONCLUSIONS: A screening system for finding maltreated children for MIES was designed. The precision of MIES could be improved by adding the treatment percentage of dental caries to daily habits.

Longitudinal Evaluation of Multi-phasic, Odontological and Nutritional Associations in Dentists (LEMONADE Study): study design and profile of nationwide cohort participants at baseline.

BACKGROUND: To examine the association between oral health and general well-being, we are currently conducting a nationwide cohort study comprising members of the Japan Dental Association (JDA). Herein, we describe the study design and the profile of the participants at baseline. METHODS: From 2001 through 2006, the participants completed a baseline questionnaire that surveyed factors related to lifestyle, general health, and oral health. Morbidity and mortality have been monitored by using information from fraternal insurance programs operated by prefectural dental associations. All respondents provided written, informed consent for participation and the use of their insurance data. RESULTS: A total of 21,272 JDA members participated in the baseline survey (response rate, 36.2%). Their mean age +/- SD was 52.3 +/- 12.3 years; 8.0% were women. Among the respondents, 30.2% of men and 10.7% of women were current smokers; 73.5% of men and 44.8% of women were current drinkers. The cohort scored higher on oral health indices than did the general Japanese population: dentists were more likely to brush their teeth > or =3 times/day, to have > or =20 teeth, to have fewer lost teeth, to be free from periodontal diseases, and to have higher General Oral Health Assessment Index scores. There was, however, considerable inter-individual variation in scores on the indices. CONCLUSIONS: More than one-third of JDA members participated in the study. Their oral average health status was better than that of the general population. Nevertheless, it will be possible to compare morbidity and mortality between those with better and worse scores on oral health indices.

[An intervention comparison of dental hygienist visits and leaflet mailing for improvement of oral health scores in village residents].

PURPOSE: This study was undertaken to clarify to what extentintervention by dental hygienist visits and leaflet mailing, once or three times a year, increased the dental health scores of Tobishima Village residents in a 3 year period. METHODS: The oral health status and oral health score (the Oral Salutogenic Score) of 786 residents were examined in May, 2004. Of the total, 446 people had oral health scores equal to or less than 15. They were divided into three groups at random, receiving: dental hygienist visits (visit group); leaflet mailing three times a year (three times mail group); and leaflet mailing only once a year (single mail group). Oral health status and scores were examined a second time by dentists in May, 2007 and average increases of scores over 3 years were calculated for each of the three groups. The Mann-Whitney test and cost-effectiveness analysis were employed for comparisons. RESULTS: The average increase in oral health score was 46.2 +/- 8.1% for the visit group, 31.2 +/- 4.4% for the three times mail group and 25.0+/-5.2% single mail group over 3 years. The visit group value was significantly higher than the single mail group (P<0.05). Of the resi-dents who had an oral health score equal to or less than 15 points, increase of their oral health score those who received a dental hygienist visit had a higher than the groups who were sent leaflets. With the latter, the greater frequency of leaflet distribution was more effective for increasing the oral health score. CONCLUSION: It was concluded that visits by dental hygienists are more effective than mailing of leaflets. In addition, mailing 2 or 3 times a year is more effective than once a year.

Calcium, magnesium, potassium and sodium intakes in Japanese children aged 3 to 5 years.

The present study aimed to evaluate in preschool children the intakes of Ca, Mg that possibly affect health and tooth formation and the intakes of K and Na that may affect lifestyle-related diseases. Information on dietary intake was collected from 90 preschool children (15 boys and 15 girls each in the 3-, 4- and 5-year old groups) on 3 separate days in the school fiscal year 1999 (April 1999 to March 2000) by the duplicate-diet technique. The Ca, Mg, K, and Na concentrations were determined by atomic absorption spectrometry using wet-ashed samples. The medians of mean daily intakes of Ca, Mg, K and Na in 3- to 5-year-old children were 432 mg, 110 mg, 1.18 g and 1.60 g, respectively, and no significant differences with regard to gender were observed. Seasonal varia-tion of intake was seen for each mineral. Calcium intake in most preschool children did not meet adequate intake (AI), probably due to low intakes of milk and dairy products in Japan. Magnesium intake was below the estimated average requirement (EAR) in 13.3% of the subjects, while the K intake met the AI. Sodium intake in a quarter of preschool children exceeded the tentative dietary goal. We concluded that in Japanese children aged 3-5 years; Ca intake is low, Na intake is high, and K intake is adequate, but some children could be at risk for Mg deficiency.

Effect of strontium in combination with fluoride on enamel remineralization in vitro.

Previous studies showed that strontium (Sr) as well as fluoride (F) can enhance enamel remineralization. The aim of this study was to evaluate the effects of Sr in combination with F on enamel remineralization in vitro. Sixty enamel specimens obtained from caries free human premolars were demineralised to produce caries-like lesions. Half of each lesion was covered with nail varnish as an untreated control. The specimens were then randomly divided into F and Sr+F treatment groups. The F group was exposed to remineralizing solutions (1.5mM CaCl(2), 0.9 mM KH(2)PO(4)) containing 1 ppm, 0.1 ppm or 0.05 ppm F. The Sr+F treatment group was exposed to the same solutions including 10 ppm Sr. After 2 weeks, lesion depth, mineral loss and percentage enamel remineralization were determined using transversal microradiography. There was a significant decrease in mineral loss in all groups (p<0.001). Lesion depth was significantly reduced for all groups (p<0.05) with the exception of group F. Remineralization was significantly affected by F concentration (p=0.000). The participation of Sr resulted in a significant enhancement of remineralization (p<0.001) with a synergistic effect of the Sr+F combination (p<0.01). It was concluded that while the remineralizing process was affected by the concentration of F, there was also an interaction between F and Sr when they were used in conjunction.

Comparison of the health condition between the 8020 achievers and the 8020 non-achievers.

AIM: To review of the difference in the health condition between 8020 achievers and 8020 non-achievers covering 25 papers which were published mainly in Japan. BACKGROUND: A campaign targeting the elderly to retain at least 20 teeth by the time they reach the age of 80 years (8020) has been in place since 1991 in Japan. RESULTS: The percentage of 8020 achievers increased from 10.9% in 1993, 15.3% in 1999 and 24.1% in 2005. The 8020 achievers had a tendency towards a strict upbringing and were not fond of sweets in their childhood. Physical indices such as height, weight, BMI score, bone mineral density, balance ability, grip strength, and exercise function in the 8020 achievers were better than the 8020 non-achievers. A close inverse relationship between the number of teeth and heart rate was recognised. The food intake survey showed that 8020 achievers ate many kinds of food. However, these foods were those with less kilocalories and lower levels of carbohydrate. The 8020 achievers had good activity in daily life (ADL) level, were satisfied with life, and had a higher cumulative survival rate. Oral health conditions including periodontal condition, masticatory ability, occlusal force, occlusal and maxillofacial forms in the 8020 achievers were better than the 8020 non-achievers.

Tooth size variability and relevance of numerical variation in the Japanese serow.

We analysed the variability of the lower cheek teeth of the Japanese serow, Capricornis crispus, from Aichi Prefecture, Japan, based on the coefficient of variation (CV), and examined tooth size variability. The mesiodistal (MD) and buccolingual (BL) crown diameters of permanent cheek teeth were measured, and an index of the crown surface (MDxBL) was calculated. As a result, the CV for MD measurements ranged from 3.6 to 6.3, and that for BL measurements ranged from 3.6 to 6.5. In males and females, the first molar (M(1)) was the least variable (3.6-4.1) and the second premolar (P(2)) was the most variable (5.0-6.5), except for the case of BL in females. The crown surface index showed a morphological gradient that increased from mesial to distal, and the values of P(2) in both sexes were extremely small. Overall, cheek tooth variability was not influenced by developmental factors, but appeared to be inversely related to functional factors. The highest coefficient of variation was observed for P(2), which was characterised by a simple shape with a single cusp, and an extremely small size compared to other teeth. Only P(2) showed congenital absence or impaction in the lower dentition. We also confirmed the relationship between tooth size variability and numerical variation.