Human temporomandibular joint eminence shape and load minimization.
Analysis of previous data suggested the hypothesis that temporomandibular joint (TMJ) eminence shapes develop ideally to minimize joint loads. Hence, we tested this hypothesis in nine females and eight males in each of two groups, with and without TMJ disc displacement. Participants provided anatomical data used in a joint load minimization numerical model to predict, and jaw-tracking data used to measure, eminence shapes. Coordinate data (x,y) of shapes were fit to third-order polynomials for two sessions, sides, and methods (predicted, measured) for each participant. Inter-session data were reliable and averaged. Those with, compared with those without, disc displacement had higher measured shape range (5:1) and left-right asymmetry prevalence (4:1). In 29 symmetrical individuals, ANCOVA and Bonferroni tests compared vertical dimensions (y) at 11 postero-anterior points (x), 0.5 mm apart. Model-predicted and measured shapes were significantly different (P < or = 0.01) near the eminence crest, but joint load minimization was consistent with eminence shape for x < 3.0 mm.
Iwasaki
L R
LR
University of Missouri-Kansas City, School of Dentistry, Department of Orthodontics & Dentofacial Orthopedics, 650 E. 25th St., Kansas City, MO 64108-2784, USA. iwasakil@umkc.edu
Crosby
M J
MJ
Marx
D B
DB
Gonzalez
Y
Y
McCall
W D
WD
Ohrbach
R
R
Nickel
J C
JC
D000328:Adult; D001696:Biomechanical Phenomena; D003430:Cross-Sectional Studies; D003766:Dental Occlusion; D005146:Facial Asymmetry / Q000473:pathology / Q000503:physiopathology; D005260:Female; D006801:Humans; D004204:Joint Dislocations / Q000473:pathology* / Q000503:physiopathology; D008297:Male; D008335:Mandibular Condyle / Q000473:pathology* / Q000503:physiopathology; D008410:Masticatory Muscles / Q000473:pathology / Q000503:physiopathology; D008875:Middle Aged; D008954:Models, Biological; D016059:Range of Motion, Articular / Q000502:physiology; D013314:Stress, Mechanical; D013704:Temporomandibular Joint / Q000473:pathology / Q000503:physiopathology; D019224:Temporomandibular Joint Disc / Q000473:pathology* / Q000503:physiopathology; D013705:Temporomandibular Joint Disorders / Q000473:pathology* / Q000503:physiopathology; D014716:Vertical Dimension; D016474:Weight-Bearing / Q000502:physiology*; D055815:Young Adult