Difference In Number Of Teeth Research Articles

Association between sharing of toothbrushes, eating and drinking habits and the presence of Actinobacillus actinomycetemcomitans in Moroccan adolescents

Actinobacillus actinomycetemcomitans is frequently detected in dental plaque collected from Moroccan adolescents, and has been shown to be associated with clinical attachment loss in this population. The aim of this study was to assess whether behaviors such as the sharing of toothbrushes, and eating and drinking habits were associated with the presence of A. actinomycetemcomitans in Moroccan adolescents. A total of 121 adolescents were clinically examined. Interviews regarding sharing of toothbrushes, eating and drinking habits were performed, and plaque samples were collected and analyzed for A. actinomycetemcomitans with different leukotoxin promoter types by polymerase chain reaction. Based on eating and drinking habits, the study population was divided in a low risk behavior group (LRB) and a high risk behavior group (HRB). No association was found between the sharing of toothbrushes and the presence of A. actinomycetemcomitans. The odds ratios between the HRB and LRB group for being positive for the JP2 type, for non-JP2 types, and for any type of A. actinomycetemcomitans were 4.74 (95% CI 0.55; 40.71), 2.49 (95% CI 1.03; 5.97), and 2.97 (95% CI 1.28; 6.91), respectively. The difference in the mean number of teeth with a clinical attachment loss of > or = 3 mm between the HRB and the LRB group was 0.91(95% CI 0.09; 1.72). Sharing of toothbrushes does not seem to be associated with the presence of A. actinomycetemcomitans in young Moroccans. Eating and drinking habits conducive to exchange of saliva are positively associated with presence of A. actinomycetemcomitans, and with a higher level of clinical attachment loss.

Studies on Epitrochoid Gear for Cycloid Drives

ABSTRACTCycloid drives are widely used in the industries because of their excellent characteristics, namely, high gear ratio, smooth transmission, compact size, high efficiency, low noise and long service life. In this paper, a mathematical model of an epitrochoid gear for a cycloid drive with a small tooth number difference has been proposed. Computerized simulation of the generated epitrochoid gear has also been developed. In this paper, the pressure angle, which has an important role in the analysis of cycloid drives as it influences the direction and magnitude of force transmission in gears, is derived based on the theory of differential geometry. The rack cutter profile, which is the fundamental tooth profile of a hob cutter, which in turn is the main manufacturing process of epitrochoid gear, has been obtained based on the theory of gearing. It is anticipated that the results from this paper will be beneficial to the design, analysis and manufacture of cycloid drives.

Number of teeth, body mass index, and dental anxiety in middle-aged Swedish women

Risk factors for poor dental health include obesity, low socio-economic status, poor dietary habits, and dental anxiety. The aim of this study was to explore the complex relation between body mass index (BMI) and number of teeth in middle-aged women taking education, dietary intake patterns, dental care utilization, and dental anxiety into account. Three groups of women (37-60 years): reference women (group I, BMI 23.8 - 3.1 kg/m2), obese women (group II, BMI 35.0 - 2.6 kg/m2), and severely obese women (group III, BMI 41.0 - 3.4 kg/m2) were included. Questionnaires were used to assess education, smoking, number of teeth, dental care utilization, dental anxiety, dietary intake, and meal patterns. Age, education, and smoking habits did not differ significantly between groups. However, there were significant global differences in number of teeth (27.2 - 3.4, 23.0 - 9.2, 24.7 - 5.9) and reported daily energy intake (9756 - 3363 kJ, 10344 - 3850 kJ, 11970 - 3786 kJ in groups I, II, and III, respectively). In a multiple regression model, a lower number of teeth was independently associated with higher age, higher BMI, lower education, irregular dental care, high dental anxiety, higher energy intake, and lower iron intake. These variables explained 25% of the variation in number of teeth. In conclusion, BMI is an independent predictor of number of teeth in middle-aged women when socio-economic, dietary, and psychological factors are taken into account.

Longitudinal radiological study of the oral health parameters in an elderly Finnish population

In the oldest elderly, an increase in the number of remaining teeth may increase oral infection foci. The aim of this follow-up study was to examine the radiologically detected oral health condition of a group of home-living elderly in Helsinki at 5-year intervals. The population of this study comprised 103 home-living elderly people, all participants of the population-based Helsinki Aging Study. Panoramic radiographysupplemented by intraoral radiographs was performed on all these participants at the Institute of Dentistry, University of Helsinki, in 1990-1991. Follow-up radiographic examination was completed in 1995-1996. Mean number of teeth decreased during the follow-up period from 13.2±9.0 to 12.5±9.2 (P = 0.0001). Mean number of teeth with periapical lesions decreased in men from 1.3±1.4 to 0.6±0.9 (P = 0.007), but no differences in number of teeth with periapical findings were observed in women. There were relatively few changes in the subjects' radiographic periodontal findings. However, fewer teeth with vertical bone pockets >1-3 mm deep were found in the follow-up study than 5 years earlier (0.6±1.2 vs 1.1±1.8; P = 0.0008). In both the baseline and the follow-up studies the radiographic findings occurred in the subjects who had retained more natural teeth. In the follow-up study, 68% of the subjects had radiographically detected signs of chronic oral infection foci. It may be concluded that radiographically detected oral health parameters remain relatively unchanged, but treatment need is higher among those who have successfully retained their natural dentition into old age.Keywords: Endodontics; gerodontology; radiography; periodontitis

Determination of load sharing factor for planetary gearing with small tooth number difference

Difference from other gear transmissions, the phenomenon of multi-tooth contact is present in planetary in planetary gearing with small tooth number difference and the load sharing factor k p is much smaller. On the basis of analyses of geometry, tooth deformation and manufacturing errors, the mathematical model which describes the state of multi-tooth contacts has been developed. The number of teeth in simultaneous contact with the load carried by the most heavily loaded tooth can be calculated by means of this model. The calculations show that the number of contacting tooth pairs should not exceed 5 in general and the values of load sharing factor k p will decrease as the tooth number and specific load increase. The values of mean K p and standard deviation δk p of load sharing factor k p , with various specific loads and parameters, have been given in this paper. They can be applied to the determination of the distribution characteristics of tooth force in the reliability design of gear. The conclusions of this paper have been verified by photoelastic experiments.

簡易最適化設計システムによる歯数差零の転位内歯車の設計

This serial study aims to develope the designing system of profile shifted involute gears and also a simple, effective optimization technique (influence index number method) that can be applied to particularly complex programming required for such a design of gears. This paper deals with the internal gear having the same number of teeth as a pinion, constituting a special internal gear-set which is engaged at an appropriate center distance to be used as a substitute for an Oldham's coupling. Because of involvement of coefficient of tangential profile shift in addition to a number of specific interference, designing variables exert complicated influences on the designing of this gear. Therefore, an effective, computerized system is required for designing of such special internal gears. The system and technique developed are fully tested by extensive actual design computation and trial manufacture of an example of gears designed by the present method. The test confirms that this designing system and simple technique are also very effective for designing of internal gears having no difference in number of teeth.

Differential Reducers Using Internal Gears with Small Tooth Number Difference : The First Report, Fundamentals of Design

A planetary differential reducer using internal gears with small tooth number difference is described : Essential points of the design are considered and an example of the reducer is manufactured. The idea is used that an internal gear with small tooth number difference has theoretically a contact ratio less than unity owing to trochoidal interference, but it is practically available under suitable condition. In case that the tooth number difference of the input-side gears is not the same as that of the output-side, such an especially high reduction ratio as 1/10, 000 is obtained. The calculation methods for strength and efficiency are given and the experimental value of efficiency is shown to agree with the theoretical one. The cost down of reducers with high reduction ratio is expected from using the above reducers which can be easily manufactured with standard pinion cutters of pressure angle 20°.

Differential Reducers Using Internal Gears with Small Tooth Number Difference : 1st Report, Fundamentals of Design

Differential Reducers Using Internal Gears with Small Tooth Number Difference : 1st Report, Fundamentals of Design

ON THE RELATION BETWEEN THE CARIES OF THE TEETH OF INFANTS LIVING IN TOKYO CITY AND THEIR DIET

A total of 487 pupils ranging from 4 to 6 years of age, selected from 5 kindergarten in Tokyo City were investigated. Dental examination was conducted together with the nutrition investigation based on the Nutrition Survey in Japan. The investigation was conducted for three days from October 2, 1963.As for the nutrition, the amount taken was investigated for each item of investigation. As for the teeth, the number of caries was compared and observed for each kindergarten and each age group. The results were as follows.1. In case of the total number of boys and girls, the carious teeth prevalence rate was 88% for 4 year old children, and 96% for 5 and 6 year old children. When these figures were compared with the national average shown in the Report of the Survey of Dental Diseases (1957) conducted by the Medical Affairs Bureau, Ministry of Health and Welfare, the number was low for 4 year old children, high for 5 year old children, and the same for 6 year old children. As for the average number of carious teeth per person, it was 5.4 for 4 year old pupils, 8.1 for 5 year old pupils, and 8.1 for 6 year old pupils. They were all less than the national average.2. As for 5 and 6 year old children, when the average number of carious teeth and the amount of the nutrition investigation items taken by each pupil were compared for each kindergarten and age group, the number of caries increased when the amount of candy taken was increased, and those taking sufficient amount of nutrition for all items of the investigation showed less caries.In case the average number of carious teeth is obtained for the 3, 5, and 6 year old pupils according to the month of birth, those born in August and September had the greatest number of carious teeth. Contrary to this, those born in January and June had less number of carious teeth.3. The difference in this average number of carious teeth per person was assumed to be caused by the changes in the mother body owing to climatic changes and especially the nutrition, since infants born in August and September have the period of mineralization in the bad season of summer when it is high temperature and high humidity whereas, infants born in January and June have the period of mineralization in spring or autumn when the climate is very good.

COMPARISON OF SKELETAL MATURATION WITH DENTAL STATUS IN JAPANESE CHILDREN

1. Data obtained from simultaneous skeletal maturation assessments and dental status evaluations on each of 1,360 Japanese children (678 boys and 682 girls) ranging in age from six to 14 years have been presented. 2. Statistically significant differences in number of permanent teeth were demonstrated between the skeletally above average and skeletally below average children, skeletally advanced children having the greater number of teeth. At individual age levels, consistent significant differences were not found. 3. Comparisons of the terminal (extreme) segments indicated statistically demonstrable differences in a greater number of individual age groups, especially among girls. 4. At each age level, the girls had a greater mean number of erupted permanent teeth than the boys.