The growth of the palate and the growth of the face during the period of the changing dentition

Abstract 1. 1. A sample of 600 Philadelphia public school children, aged 7 to 12 years, from the average middle class was selected for this study. It was as representative as possible from health, socio-economic, and ethnic points of view. These children are being studied serially, on an annual basis, at the Philadelphia Center for Research in Child Growth. 2. 2. The endo-oral measurements were secured directly on the palate of each subject and at the same time as the ecto-oral or facial measurements, to eliminate any possible age discrepancies. 3. 3. The endo-oral measurements comprise seven breadth measurements and two length measurements of the palate. The ecto-oral measurements comprise two breadth measurements and three depth measurements. All data have been reduced both according to dental stages (Hellman) and chronological age. 4. 4. The analysis of the endo-oral data led to the following conclusions: 4.1. A. The bicanine width shows an increase between Dental Stages III A and III B. According to chronological age this occurs between 7 and 8 years in girls, and between 8 and 9 years in boys. 4.2. B. Between the Dental Stages III C and IV A there is a decrease in this dimension caused, in our opinion, by the instability of changing dentition and the greater number of malocclusions in our sample. Chronologically this decrease, though negligible, is noticeable between 11 and 12 years. 4.3. C. The m1-m1 breadth similarly shows an increase from Stage III A to III B and a decrease from III C to IV A. Chronologically, this dimension shows a steady increase from 7 to 11 years as long as m1 is present. When Pm1 erupts, however, there is a decrease in this dimension, corresponding to chronological ages 10 to 12. 4.4. D. The bimolar breadths show an increase from Stage III A to III C. At Stage IV A the decrease is probably attributable to the smallness of our sample and the relatively greater number of cases of malocclusion, rather than to a reverse trend. 4.5. E. The palate length increases by posterior deposition of bone as soon as M2 shows signs of beginning eruption. 4.6. F. There is no change in the arch length anterior to M1. More specifically, there is no change in length anterior to M1, once this tooth has erupted. 5. 5. The analysis of the ecto-oral data led to the following conclusions: 5.1. A. On the basis of Hellman's dental stages, the bizygomatic breadth shows an accelerated rate of growth at two different times in boys, with a uniform rate in girls. On the basis of chronological age, in the age range of our sample, we notice two periods (7 to 8 and 10 to 11 years) of accelerated growth in boys and three (7 to 8, 8 to 9, and 11 to 12 years) in girls. 5.2. B. In the bicondylar (closed) breadths both boys and girls show a similar trend of growth according to dental stages. The chronological age analysis shows that there are accelerated periods of growth in boys which are similar in time to those of dental stages. In girls the growth is uniform from 8 to 11 years. 5.3. C. The facial depths follow the growth trend and pattern of the bicondylar breadth in both boys and girls. 6. 6. When the endo-oral and the ecto-oral dimensions are considered functionally, it is concluded that mesiodistal relationships in the face are more prognostic of dento-palatofacial relationships than are transverse relationships. This conclusion, in our opinion, goes far to validate the lateral cephalometric roentgenographic approach in the interpretation of dentofacial analysis.