This study was done to obtain data relating to the growth and development of dental arches in Korean primary school children during the five years after six years of age, which were necessary to design the models for estimating the growth and developmental patterns of dental arches in Korean students. Since the eight lengths representing dental arch width and depth were measured on the stone dental arch models of 565 six year-old students residing in Yeoncheon-Gun county, Kyungki-Do province in 1995, they were longitudinally measured each year until the year 2000. The eight lengths representing dental arch width and depth were respectively measured on the stone dental arch models of 547 seven year-old students in 1996, 521 eight year-old students in 1997, 488 nine year-old students in 1998, 464 ten year-old students in 1999 and 442 eleven year-old students in 2000. Besides, 82 cephalometric distances and 54 cephalometric angles representing craniofacial depth and height were measured on the lateral cephalograms of 565 seven year-old students in 1996. According to the profile classification criteria reported by Lee and Mood´, the profiles of 565 six year-old students were classified into seven profile groups, which were the upper neutral positioned lower retrognathic long profile group, the upper prognathic lower prognathic very long profile group, the upper retrognathic lower retrognathic middle profile group, the upper prognathic lower neutral positioned short profile group, the upper neutral positioned lower neutral positioned very short profile group, the upper neutral positioned lower neutral positioned very long profile group and the upper
,neutral positioned lower neutral positioned middle profile group. During the five years after six years of
age since 1995, the changed eight lengths of dental arch width and depth representing the growth and development of dental arches were compared and discussed respectively in the seven profile groups.
The obtained results were as follows ;
1. Upper inter-deciduous canine widths were continued to increase each year for two years after six years of age in all the male and female seven profile groups. However, they were continued to increase each year after eight years of age in all the other male and female profile groups except the male upper neutral positioned lower retrognathic long profile group and the male upper prognathic lower neutral positioned short profile group.
2. Lower inter-deciduous canine widths were continued to increase each year after six years of age in all the male and female seven profile groups.
3. Upper intermolar widths were continued to increase each year for five years after six years of age in all the other male and female profile groups except the female. upper prognathic lower prognathic very long profile group.
4. Lower intermolar widths were continued to increase each year for five years after six years of age in all the other male and female profile groups except the male upper neutral positioned lower neutral positioned very short profile group, the female upper neutral positioned lower neutral positioned very short profile group, the female upper prognathic lower neutral positioned short profile group and the female upper neutral positioned lower neutral positioned middle profile group.
5. Upper deciduous canine depths were rapidly increased each year for two years after six years of age in all the male and female profile groups. However, they were continued to increase each year after eight years of age in all the other male and female profile groups except the male upper prognathic lower neutral positioned short profile group, the female upper neutral positioned lower retrognathic long profile group and the female upper neutral positioned lower neutral positioned middle profile group.
6. Lower deciduous canine depths were continued to increase each year after six years of age in all the other. male and female profile groups except the female upper retrognathic lower retrognathic middle profile group and the female upper neutral positioned lower neutral positioned very short profile group.
7. Upper molar depths were slowly increased each year for four years after six years of age in all the male .and female profile groups. However, they were decreased after ten years of age in all the male and female profile groups.
8. Lower molar depths were increased for one year after six years of age in all the male and female profile groups. However, they were increased for one year after seven years of age in all the other male and female profile groups except the male upper retrognathic lower retrognathic middle profile group, the male upper neutral positioned lower neutral positioned very short profile group and the male upper
neutral-positioned lower neutral positioned very short profile group.´ And, they were increased for one
year after eight years of age in all the other male and female profile groups except the female upper retrognathic lower retrognathic middle profile group. But they were continued to decrease each year after nine years of age in all the male and female profile groups.
|