Morphometric analysis of mandibular growth in skeletal Class III malocclusion.
BACKGROUND
The craniofacial growth patterns of untreated individuals with skeletal Class III malocclusion have rarely been systemically investigated. This study used morphometric techniques to investigate the growth characteristics of the mandible in individuals with skeletal Class III malocclusion.


METHODS
Lateral cephalometric head films of 294 individuals with untreated skeletal Class III malocclusion (134 males, 160 females) were selected and divided into five triennial age groups (T1-T5) and by gender to identify the morphologic characteristics and sexual dimorphism in changes of mandibular growth. Procrustes, thin-plate spline, and finite element analyses were performed for localization of differences in shape and size changes. Maximum and minimum principal axes were drawn to express the directions of shape changes.


RESULTS
From T1 (age 6-8 years) to T4 (age 15-17 years), the distribution of localized size and shape changes of the mandible was very similar between the two genders. From T1 to T2 (age 9-11 years), significant lengthening of the condylar region was noted (23.4-39.7%). From T2 to T3 (age 12-14 years), the greatest size and shape change occurred at the condylar head (27.4-34.9%). From T3 to T4, the greatest size and shape changes occurred in the symphyseal region (23.6-42.1%). From T4 to T5 (age>or=18 years), significant sexual dimorphism was found in the distribution and amount of localized size and shape changes. Females displayed little growth increments during T4. Despite differences in the remodeling process, the whole mandibular configurations of both genders exhibited similarly significant upward and forward deformation from T4 to T5.


CONCLUSIONS
We conclude that thin-plate spline analysis and the finite element morphometric method are efficient for the localization and quantification of size and shape changes that occur during mandibular growth. Plots of maximum and minimum principal directions can provide useful information about the trends of growth changes.
Chang
Jenny Zwei-Chieng
JZ
School of Dentistry, College of Medicine, National Taiwan University, Taipei, Taiwan. jennyzc@ms3.hinet.net
Chen
Yi-Jane
YJ
Chang
Frank Hsin-Fu
FH
Yao
Jane Chung-Chen
JC
Liu
Pao-Hsin
PH
Chang
Chih-Han
CH
Lan
Wan-Hong
WH
D000293:Adolescent; D002508:Cephalometry; D002648:Child; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D008297:Male; D008313:Malocclusion, Angle Class III / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008334:Mandible / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008445:Maxillofacial Development; D011859:Radiography