Gebissentwicklung - Durchbruch der permanenten Zähne in der 2. Wechselphase

From the archives of the orthodontic departments of the university hospitals Gießen and Marburg, Germany, there were taken 1485 plaster casts from 686 boys and 799 girls. They were in the second transition period of the mixed dentition. The number of new teeth was counted and it was registered which tooth came first. Chronological age as well as gender was known. The following criteria had to be fulfilled: The distance between the canine and the first molar had to be at least 19 mm, a full complement of teeth, no bigger caries lesions and a normal development of the dentition. First it was established which tooth from the upper and the lower jaw emerged first. This could only be seen if there was either just one tooth per jaw, or the eruption sequence in case of more teeth per jaw could be determined. This was done by comparing the distance from the top of the tooth to the occlusal plane. The results are presented in separate charts for boys and girls and where compared to other studies. For each group of boys and girls who had the same number of new teeth in the second transition period, the average chronological age was calculated. A new tooth was counted if any part of the tooth had perforated the gums. The results were graphically compared to other studies. The skeletal age of a subset (n=293) of our sample was known from earlier studies. The correlation between chronological and skeletal age was calculated. Finally we compared our results with an earlier study from Marburg. We wanted to find out if our stricter selection criteria had an influence on the results.