[Longitudinal changes of posterior available spaces of lower dental arch in adolescents with normal occlusion from 13 to 18 years of age].
OBJECTIVE
To investigate the changes of available spaces of posterior arch segments in mandibular dentition from 13 to 18 years of age, which would provide information for space analysis of whole dental arch in adolescents.


METHODS
Twenty-six adolescents (12 males, 14 females) with normal occlusion were selected. All of the subjects had lateral cephalograms taken at the same time each year for 6 years. Longitudinal cephalometry and statistic analysis were conducted for all subjects.


RESULTS
Significant differences of available space were found between males and females. The growth of available space from 13 to 18 years of age was 5.12 mm in females and 5.79 mm in males. The completion of mandibular remodeling in males lagged behind females for about 1 year. No significant increase was found in girls beyond 16 years and in boys beyond 17 years. There was a 1.22 mm increase on each side per year in females until 16 years and a 1.45 mm increase in males until 17 years. The increase of available space was made partly by resorption of bone from the anterior border of the ramus and partly by mesial movement of the first molar. The mesial movement of dental arch was probably stimulated by the eruption of the third molars.


CONCLUSIONS
The prediction of available space should be based on age and sex.
Chen
Li-Li
LL
Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing 100081, China.
Lin
Jiu-Xiang
JX
Xu
Tian-Min
TM
Zhang
Xing-Zhong
XZ
D000293:Adolescent; D000367:Age Factors; D002508:Cephalometry; D003724:Dental Arch / Q000254:growth & development*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008334:Mandible / Q000254:growth & development; D008964:Molar, Third / Q000254:growth & development; D009971:Orthodontics, Corrective; D012737:Sex Factors; D014078:Tooth Eruption; D014085:Tooth Migration