Third molar as an age indicator in young individuals.

The authors developed a method of chronological age estimation in young individuals on the basis of third molar developmental stage. The new method is based on the finding that time course of third molar development depends on the number of assessed third molars. That means, in individuals with 1 to 3 third molars agenesis the development of founded third molars is delayed in comparison with individuals having all third molars present. This difference is statistically significant. Retardation of development is directly proportional to the number of congenitally missing third molars. Chronological age corresponding to individual stages of third molar development was calculated separately for individuals with all four third molars present and separately for individuals with 1 to 3 third molars agenesis. With this division it was possible to decrease the error of age estimation to 1.63 years in the group of individuals with all four third molars present and to correct the age underestimation in individuals with agenesis. The elaborated method of chronological age estimation in young individuals shows incomparably much more accuracy in contrary to methods used in adults. In addition this new method is distinguishing by maximum simplicity.

Agenesis of third molars in young Czech population.

The aim of this study is to evaluate the incidence of third molars agenesis in the Czech population. One thousand patient's panoramic radiographs of the pedostomatological department of Second Stomatological Clinic of The First Faculty of Medicine, Charles University, has been analyzed. The age of probands was ranging between 12 to 21 years inclusive. Patients were divided into 10 groups according to age. In each age group were 100 individuals - 50 boys and 50 girls. Agenesis of 1-4 third molars was present in 22.5% (25.6% in boys and 19.4% in girls). Intersexual difference is significant. Further, the incidence of third molars agenesis in individual dentition quadrants, upper and lower jaw and right and left side of dentition was examined. Neither in boys nor in girls were detected significant differences in these values. Agenesis of just one, any third molar occurs in 10.9% (12.0% in boys and 9.9% in girls). For one individual it is mean 1.9 congenitally missing third molars in boys and 2.0 congenitally missing third molars in girls. These intersexual differences are not significant. In boys, the most frequent agenesis was of one, next of two, then of three and at last of four third molars. In girls, agenesis of two was on the first place, then that of one and lastly and equally of three and of four third molars. The results were compared with literature data.

Development of third molar in the Czech population.

The third molar development was studied on the basis of 1700 panoramic radiographs analysis of randomly selected individuals in the age ranging between 5-21 years inclusive. Each age group consisted of 100 probands--50 boys and 50 girls. The characteristics of the third molar development were following: time of dental follicle formation--dynamics of development--the most frequent stages of third molar development in individual age groups-- intraindividual differences and symmetry of development--incidence of 1-4 third molars agenesis--relation between the third molar development and the dental age--differences in the third molar development between individuals with all four third molars present and individuals with 1-3 third molars agenesis--ntersexual differences. On the basis of our analysis of seven stages of development, differences of this process between males and females and the changes in dynamics of development characterizing upper and lower jaw were described. The incidence of the third molar agenesis was statistically significant, being more frequent in boys (24.2%) than in girls (17.6%). The study showed, that when the third molar is not present at the age of thirteen, it could be taken in the Czech population as agenesis. Correlation between developmental stage of third molars and dental age was ascertained. With the exception of the agenesis, no other statistically significant intersexual differences were found.

Anomalous maxillary lateral incisor--the only product of dental lamina, difficult classifiable in the time. Symptom of hypodontia syndrome non-described until present time.

The authors described anomalous development of maxillary lateral incisor non-yet published in stomatologic literature. Diagnostics and clinical findings of the anomaly and the prognosis of the affected tooth they based on the description of six longitudinal observed patients. The principal symptom of the anomaly is the disturbance of time-plan of the tooth development. Terms of the tooth mineralization, the time of eruption and root completion cannot be included either in deciduous or in permanent dentition. The tooth is the only product of the dental lamina; it has no predecessor or successor. Frequent disturbances of the eruption pathway result often in anomalous position of the tooth. Taking into consideration the fact that the anomaly appeared always in connection with hypodontia syndrome, it is possible to consider it to be the symptom of hypodontia syndrome. This fact is more significant as it enables to establish the diagnosis of hypodontia syndrome already in early deciduous dentition.

[Exchange of dentition and its control. Overview of current knowledge and personal experience]. / Výmena denticí a moznosti jejího rízení. Prehled soucasných poznatku a vlastních zkuseností.

Physiological dentition exchange is often interfered with exogenous and endogenous factors. For this reason it must be steadily regulated. The authors present complex view on this topic based on literature studies and own experiences. The authors define fundamental principles "guided exchange", "tooth eruption" and "eruption path". Correct explication of these ideas is necessary for text understanding. Dentition exchange is considered as complex of eruption interactions of individual permanent teeth including molars. The project is based on idea that dentition exchange time is optimal for preventive interventions. At the end the authors underline the importance of global application of the above-mentioned principles on the whole child population.

Studies on agenesis of third molars amongst populations of different origin.

This study contains information on the occurrence of agenesis of one to four third molars among the population and ethnic groups of Europe, North America, Africa and Asia (Japan), based on the results of investigations carried out by dozens of authors. Recent discoveries have been supplemented with corresponding data concerning the skeletal remains of the jaws of individuals living from the ice age to the middle ages. The results show unbelievably large diversities as regards the frequency of agenesis of third molars in different populations from practically zero (Tasmania) to nearly 100% (Mexican Indians). This remarkable fact is not, however, the only reason why the problem of third molars remains a major concern for anthropologists, anatomists and stomatologists. Indeed, agenesis of third molars present only one of the most important anomalies which characterizes this tooth. It is necessary to look for the roots of the said variability in the remarkably complicated phylogenetic development undergone by the third molar from the time of our predecessors to the present day. Most of today's authors are of the opinion that although significant involution changes have occurred in third molars, that with the advent of hominization the number of teeth in individuals has stabilized at eight for every quadrant of dentition. For this reason it is not possible to regard agenesis of third molars as the manifestation of the phylogenetic reduction in the number of teeth, but as the developmental anomaly which is the result of a mutation and selection process based on heredity. The results are completed with an analysis of the value of agenesis of one to four third molars according to the individual quadrants and gender. A knowledge of these indicators is necessary in order to study the relationship between agenesis of third molars and hypodontia of the other teeth.

[Prevalence of mineralization disorders in dental tissues in children in fluoridated regions of Kladno]. / Prevalence poruch mineralizace zubních tkání detí ve fluoridovanych oblastech Kladenska.

The authors subjected to dental examinations a group of children aged 12-13 years from the Kladno area and surrounding rural communities. The children from Kladno drank from birth fluoridated water from the water mains, while the rural children, where well water had a minimum fluoride content, had to rely on sodium fluoride tablets. In all children the prevalence of non-carious changes of dental tissues was assessed, the cariosity (DMF), oral hygiene (OHI) and the state of the gingiva (PI). The objective was to assess to what extent and in which indicators the urban and rural children differ. The results were compared with the status in Prague children who were not exposed to fluoride during the first years of life. The results revealed that the Kladno children differ only as regards cariosity which is significantly higher in the rural children. This finding can be explained by irregular intake of sodium fluoride tablets. As compared with Prague children, there was a marked difference in the prevalence of non-carious changes of dental tissues in favour of the children from the Kladno area. Their cariosity was also significantly lower. The results provide evidence that fluoridation of drinking water is not only the most effective way how to prevent caries but that it prevents also inadequate mineralization of dental tissues.

[Analysis of environmental indicators in relation to structural disorders of dental tissues]. / Rozbor nekterých ukazatelu zivotního prostredí ve vztahu k poruchám strukturyzubních tkání.

An epidemiological investigation revealed a high incidence of structural disorders of dental tissues in the child population of Prague. While hypoplastic disorders are steadily diminishing, there is an ever rising trend of hypomineralization. The observed disorders of hypomineralization are becoming a serious clinical problem. The aim of the present investigation was to assess to what extent exogenous harmful substances participate in the development of hypomineralization: infectious diseases, tetracycline antibiotics, excess fluorine intake and type of drinking water--from the water-mains or wells. The data were assembled by means of questionnaires. Two clinical investigations comprising 300 children, mean age 13 years, suggest that among the investigated indicators only the type of drinking water can be associated with the development of the observed changes. Children drinking from birth water from wells had significantly fewer disorders of mineralization than children who drank water from the water-mains. The submitted paper presents partial results of the state research plan of technical development.

[Comparative study of the prevalence of disorders of impaired structure of dental tissues in school children and university students]. / Srovnávací studie prevalence poruch struktury zubních tkánki u skolnich detí a vysokoskolských studentu.

The authors examined a group of 573 Prague children aged 12-15 years. In addition to the incidence of disorders of the structure of dental tissues they investigated the coriosity (DPE), oral hygiene (OHI) and condition of the gingiva (PI). Their main interest was focused on impaired mineralization of dental tissues the incidence of which is indemic in Prague children. The group was compared with 62 university students. It is of interest that in all indicator except impaired mineralization, the children had significantly better results. The rising curve of impaired mineralization signalises the ever deteriorating living environment in the capital.