Characteristics of mandibular movements in patients with square mandible.
OBJECTIVE
The aim was to report the kinetics of masticatory muscles using a 4-dimensional muscle model and kinetically investigate the etiology of square mandible (SQM) in vivo.


METHODS
To ascertain the mandibular movements in patients with SQM, we compared a group of 11 SQM patients with painless limited mouth opening to a matched group of 11 healthy volunteers who acted as control subjects. Mandibular movements were recorded using a 6-degrees-of-freedom jaw-tracking device, with the incisal and kinematic condylar as analytic points.


RESULTS
For the control group, mean tracking distance for the incisal point was 50.1 +/- 6.8 mm, whereas for the SQM group mean tracking distance was 27.1 +/- 2.8 mm. With lateral excursions, the control group's mean tracking distance of the incisal point was 9.9 +/- 2.01 mm, and the SQM group's was 8.1 +/- 1.64 mm.


CONCLUSIONS
Despite a sufficient lateral excursion, motion of the mandible was limited by some factors at opening and suggests that the mode of lateral movements in SQM patients may differ slightly from those in healthy individuals.
Hirai
Shinya
S
Department of Fixed Prosthodontics, Tsurumi University School of Dental Medicine, Tsurumi university, Yokohama, Japan. hirai-s@tsurumi-u.ac.jp<hirai-s@tsurumi-u.ac.jp>
Ogawa
Takumi
T
Shigeta
Yuko
Y
Ando
Eriko
E
Hirabayashi
Rio
R
Ikawa
Tomoko
T
Kasama
Shintaro
S
Fukushima
Shunji
S
Matsuka
Yosizo
Y
D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D005260:Female; D056973:Four-Dimensional Computed Tomography / Q000379:methods*; D006801:Humans; D006984:Hypertrophy / Q000000981:diagnostic imaging / Q000503:physiopathology; D007569:Jaw Abnormalities / Q000000981:diagnostic imaging* / Q000503:physiopathology; D007700:Kinetics; D008297:Male; D008334:Mandible / Q000002:abnormalities / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D008410:Masticatory Muscles / Q000473:pathology / Q000503:physiopathology*; D008875:Middle Aged; D008954:Models, Biological; D009068:Movement; D016059:Range of Motion, Articular; D013704:Temporomandibular Joint / Q000000981:diagnostic imaging / Q000502:physiology