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.