Characterizing mandibular growth using three-dimensional imaging techniques and anatomic landmarks.
OBJECTIVE
To provide quantitative data on the multi-planar growth of the mandible, this study derived accurate linear and angular mandible measurements using landmarks on three dimensional (3D) mandible models. This novel method was used to quantify 3D mandibular growth and characterize the emergence of sexual dimorphism.


METHODS
Cross-sectional and longitudinal imaging data were obtained from a retrospective computed tomography (CT) database for 51 typically developing individuals between the ages of one and nineteen years. The software Analyze was used to generate 104 3DCT mandible models. Eleven landmarks placed on the models defined six linear measurements (lateral condyle, gonion, and endomolare width, ramus and mental depth, and mandible length) and three angular measurements (gonion, gnathion, and lingual). A fourth degree polynomial fit quantified growth trends, its derivative quantified growth rates, and a composite growth model determined growth types (neural/cranial and somatic/skeletal). Sex differences were assessed in four age cohorts, each spanning five years, to determine the ontogenetic pattern producing sexual dimorphism of the adult mandible.


RESULTS
Mandibular growth trends and growth rates were non-uniform. In general, structures in the horizontal plane displayed predominantly neural/cranial growth types, whereas structures in the vertical plane had somatic/skeletal growth types. Significant prepubertal sex differences in the inferior aspect of the mandible dissipated when growth in males began to outpace that of females at eight to ten years of age, but sexual dimorphism re-emerged during and after puberty.


CONCLUSIONS
This 3D analysis of mandibular growth provides preliminary normative developmental data for clinical assessment and craniofacial growth studies.
Vocal Tract Development Laboratory, Waisman Center, University of Wisconsin-Madison, 1500 Highland Ave., Rooms 429/427, Madison, WI 53705, USA. Electronic address: mkelly1@wisc.edu.
Michael P
MP
Kelly
Vocal Tract Development Laboratory, Waisman Center, University of Wisconsin-Madison, 1500 Highland Ave., Rooms 429/427, Madison, WI 53705, USA. Electronic address: vorperian@waisman.wisc.edu.
Houri K
HK
Vorperian
Vocal Tract Development Laboratory, Waisman Center, University of Wisconsin-Madison, 1500 Highland Ave., Rooms 429/427, Madison, WI 53705, USA; Department of Biostatistics and Medical Informatics, University of Wisconsin-Madison, 1300 University Avenue, Madison, WI 53706, USA. Electronic address: yuanw@stat.wisc.edu.
Yuan
Y
Wang
Vocal Tract Development Laboratory, Waisman Center, University of Wisconsin-Madison, 1500 Highland Ave., Rooms 429/427, Madison, WI 53705, USA. Electronic address: kkassulke@waisman.wisc.edu.
Katelyn K
KK
Tillman
Vocal Tract Development Laboratory, Waisman Center, University of Wisconsin-Madison, 1500 Highland Ave., Rooms 429/427, Madison, WI 53705, USA. Electronic address: holden@wisc.edu.
Helen M
HM
Werner
Vocal Tract Development Laboratory, Waisman Center, University of Wisconsin-Madison, 1500 Highland Ave., Rooms 429/427, Madison, WI 53705, USA; Department of Biostatistics and Medical Informatics, University of Wisconsin-Madison, 1300 University Avenue, Madison, WI 53706, USA. Electronic address: mkchung@wisc.edu.
Moo K
MK
Chung
Department of Radiology, University of Wisconsin Hospital and Clinics, University of Wisconsin-Madison, Box 3252 Clinical Science Center, E1 336, 600 Highland Ave., Madison, WI 53792, USA. Electronic address: lgentry@uwhealth.org.
Lindell R
LR
Gentry
D000293:Adolescent; D059925:Anatomic Landmarks; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D007223:Infant; D008137:Longitudinal Studies; D008297:Male; D008334:Mandible / Q000000981:diagnostic imaging* / Q000254:growth & development*; D011857:Radiographic Image Interpretation, Computer-Assisted; D014057:Tomography, X-Ray Computed; D055815:Young Adult
3DCT; Development; Mandible; Measurement