Influence of tooth-to-denture-base discrepancy on space closure following premature loss of deciduous teeth

Dental age assessment by tooth emergence counts its chronological age predictive value in normal occlusion Bogotanians (mestizos)

Objective: (1) To test Hägg-Taranger's method of dental age assessment (DAA) in Bogotanian children comparing findings by sex with Swedishes' standards and (2) to investigate its chronological age predictive value for identification purposes.Material and methods: Dental age was assessed in 5-14-year-old Bogotanians, 2075 girls and 2032 boys and compared with the method's standards. For statistical analysis, matched-pair signed-rank tests were used, and a regression model was used for investigating value as chronological age predictor from dental age.Results: No significant difference was found between means of dental ages of Bogotanians and Swedishes, except for the lower central incisors' and second molars' emergences. Differences by sex between dental age means were seen at all stages especially, in mixed dentition (p<.01), being Bogotanian girls earlier maturers than boys. The established regression model as chronological age predictor, was tested by the coefficient of determination, which was found r²=0.979 for girls, and 0.957 for boys.Conclusions: Sexual dimorphism in dental age suggests Hägg-Taranger's method for identification by sex at mixed dentition. Additionally, high coefficients of determination show its reliability as chronological age predictor for ages from 5 to 12 years in girls, and to 13 years in boys.

Dental caries prevalence as evidence for agriculture and subsistence variation during the Yayoi period in prehistoric Japan: biocultural interpretations of an economy in transition

The Yayoi period represents the earliest point of agricultural dependence in Japan, dating from approximately 2500 BP to AD 300. Yayoi period people consumed wet-rice as a primary subsistence base. This article uses dental caries prevalence to interpret the biocultural implications of agriculture among these people by testing the following hypotheses: 1) Yayoi period agriculturalists had greater frequencies of carious teeth than Jomon period foragers, 2) regional variation in carious tooth frequencies will be observed among Yayoi period agriculturalists, while 3) variation in carious tooth frequencies will be observed between male and female agriculturalists. Statistically significant differences in carious teeth were observed between the agriculturalists from Southern Honshu and all other samples. These differences suggest greater reliance on cariogenic plants among farmers from Southern Honshu and are consistent with an agricultural economy. The people of the Yayoi period from Tanegashima Island and Northern Kyushu did not have significantly different carious tooth frequencies compared to Jomon period foragers. This suggests that rice alone was not a more cariogenic dietary substance than those consumed by Jomon period foragers but a cariogenic food nonetheless. Dietary heterogeneity between the prehistoric people of the Yayoi period from Southern Honshu and those from Northern Kyushu and Tanegashima Island is also inferred from these differences. Significantly greater frequencies of carious teeth among older aged Yayoi period females compared with males suggest dietary differences between the sexes.

Selection of reference foods for a scale of standards for use in assessing the transitional process from milk to solid food in infants and pre-school children

OBJECTIVE

This paper describes the development of a reliable scale of standards for use in evaluating the progress of the transition from milk to solid food in infants and preschool children. The maturation of chewing and swallowing behavior in infants and young children, which enables processing of solid food, varies, and a scale would assist not only in the instruction of mothers and nurses but also in preventing delay in the introduction of solid food.

DESIGN

A range of 159 reference foods were selected on the basis of intake during the period of transition from liquid to solid food. These foods were listed in our previous study, Validity and reliability were tested to create a scale.

METHODOLOGY

Foods were selected on the basis of 50% of the subjects studied being able to eat them, and on the food groups classified by cluster analyses using the Varclus procedure of SAS. Validity, of the scale was tested by using Pearson's correlation coefficient between the scale score of selected food items and the total score of all 159 food items. The total score of 159 food items was calculated using the general linear models (GLM) procedure of SAS. Reliability was tested using Cronbach's coefficient alpha.

SETTING

Public health centers in Aomori, Tokyo, Saitama, Nagano, and Okinawa (Japan).

SUBJECT

Five hundred and eighty healthy mothers and children from 2 to 46 months were randomly selected and 470 (81.0%) completed the study. To avoid regional bias, subjects were drawn from northern to southern prefectures in Japan, namely Aomori, Tokyo, Saitama, Nagano, and Okinawa.

RESULTS

Twenty food items were selected. By analyzing the score correlation using Pearson's correlation coefficient (R =0.97, P <0.001) and GLM (R2 =0.95, P <0.001), it was confirmed that these 20 food items adequately represented the original 159. The reliability was also found to be sufficient (Cronbach's coefficient alpha=0.96).

CONCLUSIONS

The findings demonstrate that a scale of standards for measuring progress in chewing ability can be created using 20 food items. Such a standard will provide a useful basis against which to assess delay of solid food introduction in childhood.

SPONSORSHIP

Grant-in-Aid for Scientific Research, provided by the Japanese Ministry of Education, Science and Culture, Project No. 07838030.

Presence of third molar germs in orthodontic patients in Japan

The purpose of this investigation was to evaluate the existence of third molar germs in orthodontic patients in Japan and to examine the relationship between the existence of third molars and sagittal maxillomandibular jaw relationships. The subjects comprised 306 patients from the orthodontic clinic of Hokkaido University Dental Hospital who were younger than 15 years. The subjects were divided into 2 groups: 1 group included 144 patients who were born between 1966 and 1969 (60s group), and the other group included 162 patients who were born between 1980 and 1987 (80s group). Assessments were made from panoramic radiographs and lateral cephalograms. The following results were obtained: (1) all 4 third molar germs were present in 77% of subjects, (2) mandibular third molars were present significantly more often than maxillary third molars, and (3) the percentage of skeletal Class III subjects who had all 4 third molars was lower than that of skeletal Class II subjects. The chi(2) test was used to determine statistical significance in differences.

Diet and discrepancy between tooth and jaw size in the Yin-Shang period of China

Tooth to denture base discrepancy (the discrepancy) is the difference between the dental arch length and the sum of crown diameters of teeth in the jaw, a concept which was originally developed in orthodontics. Since the cause-effect relationship between a soft diet and the discrepancy has been demonstrated, the size of the discrepancy should indicate the amount of load on the masticatory system from chewing foods in jaws from archaeological periods. The dietary condition of 71 citizens compared to that of 186 slaves from the Yin-Shang period of China was reconstructed through a study of the discrepancy. The prevalence of the discrepancy in the Yin-Shang period was around 15%, almost the same as it was during the later Jomon to Yayoi (3000-2000 BP) periods, when rice agriculture was introduced into Japan, and also the same as for present-day pastoralists around Lake Turkana, Kenya. Although the frequency of the discrepancy was slightly higher in male citizens, there were no significant differences in the frequencies between male citizens and female citizens or slaves. The differences in diet may not have been fundamental since the Yin-Shang period would be at the very beginning of the age in which differences of diet according social class began to appear, with implications for the load on the masticatory system. At that time agriculture may not been sufficiently intensified in variety or quantity to have produced a differentiation of the diet between social classes.

Masseter muscle activity in bottle feeding with the chewing type bottle teat: evidence from electromyographs

It was reported that the activity of the masticatory muscles is reduced in bottle fed babies. The effects of chewing type bottle teats distributed in Japan on masticatory muscle activity were evaluated. Myoelectric activities of the masseter muscles of 12 babies bottle fed with chewing type bottle teats were recorded and analyzed by the same method as in the previous study. The electromyographic records of 12 breast fed babies and 12 babies bottle fed with regular sucking type bottle teats, which were reported in a previous study, were used as controls. The results show that the masseter muscle activity of babies bottle fed with chewing type bottle teats was similar to that of breast fed babies qualitatively as well as quantitatively. However, activity was visibly different from that of babies bottle fed with sucking type bottle teats, showing significant difference by ANOVA. These data suggest that babies who are ingesting milk from chewing type bottle teats do so with a chewing action similar to that of breast feeding, but very different from that of bottle feeding with sucking type bottle teats. The conclusion was that the chewing type bottle teat is useful for establishing masseter muscle activity.

Reduction of masseter muscle activity in bottle-fed babies

Our previous studies suggested that there are significant differences in the growth of the jaw and in muscle activity between breast- and bottle-fed infants. To confirm these differences quantitatively, myoelectric activities of the masseter muscles of bottle-fed babies were studied. Twelve bottle-fed babies, as well as 12 breast-fed babies as a control group, were examined electromyographically during bottle or breast feeds. The duration time of sucking bursts, interval time, cycle time, 0-to-peak amplitude, integrated amplitude of bursts, and integrated amplitude/duration time were measured and the number of bursts over 30 microV was counted. All differences of means were significant by t-test. The masseter muscle activity in bottle-fed babies is significantly reduced. Our results are contrary to previous papers in which almost the same sucking actions in both breast and bottle feeding were reported. The reason why previous researchers thought that the sucking patterns in breast- and bottle-fed babies are essentially the same is considered, and the implications of the differences for dental health are discussed.