Assessment of mandibular growth and response to orthopedic treatment with 3-dimensional magnetic resonance images.
BACKGROUND
Three-dimensional (3D) craniofacial images are commonly used in clinical studies in orthodontics to study developmental and morphologic relationships.


METHODS
We used 3D magnetic resonance imaging to study relationships among craniofacial components during the pubertal growth spurt and in response to Fränkel appliance therapy. The sample for this prospective study was 156 high-resolution magnetic resonance images with 1 mm isotropic voxel resolution of 78 subjects taken initially (T1) and 18 +/- 1 months (T2) after treatment or an observation period. The subjects were Brazilian children; 28 were treated and 25 were untreated for Class II malocclusion, and 25 were untreated with normal occlusions. A Procrustes geometric transformation of 3D skeletal landmarks was used to assess growth or treatment alterations from T1 to T2. The landmarks were located on the mandibular rami and the other craniofacial parts specifically related to the mandibular growth (the middle cranial fossae and the posterior part of the bilateral nasomaxilla). This allowed visualization of the entire volumetric dataset with an interactive 3D display.


RESULTS
Statistically significant differences were found in the relative 3D skeletal growth directions from T1 to T2 for treated vs untreated Class II children (Bonferroni-adjusted P < .001) and for treated Class II vs normal-occlusion subjects ( P < .001). The major differences in the treated group were increased mandibular rami vertical dimensions and more forward rami relative to the posterior nasomaxilla and the middle cranial fossae. Principal component analysis made it possible to show individual variability and group differences in the principal dimensions of skeletal change.


CONCLUSIONS
These methods are generalizable to other imaging techniques and 3D samples, and significantly enhance the potential of systematically controlled data collection and analysis of bony structures in 3 dimensions for quantitative assessment of patient parameters in craniofacial biology.
Cevidanes
Lucia H S
LH
Department of Orthopedics, School of Dentistry, University of North Carolina, Chapel Hill, NC 27599-7450, USA. cevidanl@dentistry.unc.edu
Franco
Alexandre A
AA
Gerig
Guido
G
Proffit
William R
WR
Slice
Dennis E
DE
Enlow
Donald H
DH
Yamashita
Helio K
HK
Kim
Yong-Jik
YJ
Scanavini
Marco A
MA
Vigorito
Julio W
JW
D002508:Cephalometry / Q000379:methods; D002648:Child; D035301:Cranial Fossa, Middle / Q000033:anatomy & histology / Q000254:growth & development; D003766:Dental Occlusion; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008312:Malocclusion, Angle Class II / Q000628:therapy*; D008334:Mandible / Q000033:anatomy & histology / Q000254:growth & development*; D019186:Mandibular Advancement / Q000295:instrumentation; D008335:Mandibular Condyle / Q000033:anatomy & histology / Q000254:growth & development; D008437:Maxilla / Q000033:anatomy & histology / Q000254:growth & development; D017289:Orthodontic Appliances, Functional; D011446:Prospective Studies; D011627:Puberty / Q000502:physiology; D013100:Sphenoid Bone / Q000033:anatomy & histology / Q000254:growth & development; D014716:Vertical Dimension