title: Measurement of jerk-cost using a triaxial piezoelectric accelerometer for the evaluation of jaw movement smoothness.
abstract: Jerk-cost as a measure of jaw movement smoothness has been used to evaluate the masticatory function of patients with tooth loss and malocclusion. Jerk-cost measuring systems have thus far been unable to determine the jerk-cost of each chewing phase over time. The purposes of this study were (i) to develop a new method for measuring momentary jerk-cost of the jaw movement using a small triaxial piezoelectric accelerometer and (ii) to test the hypothesis that the lowest smoothness is seen during jaw-opening phase. The accelerometer was attached to the skin of the mentum of each subject. Vertical jaw displacement, acceleration, the jerk, and the time differential of jerk-cost during gum chewing were analysed as a function of time in five normal dentate subjects (n = 5). The system revealed intra-class correlation coefficients of intra-examiner, inter-examiner, and test-retest consistency of substantially high values (0.80-0.88). In all subjects, the highest jerk-cost was observed in the opening phase of each chewing cycle when the gum was parting from the teeth; the lowest jerk-cost was observed in the intercuspal phase throughout the chewing cycle, thus confirming the hypothesis. Significant differences were observed between the opening, closing, and intercuspal chewing phases (N = 5, P = 0.007). The smoothness measurement system used in this study evaluated the momentary smoothness of each chewing phase in the masticatory cycle. The system may serve as a diagnostic tool to evaluate the smoothness of the jaw movement in general dental practice.
authors.affiliation: Removable Partial Prosthodontics, Division of Oral Health Sciences, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan. minami.rpro@tmd.ac.jp
authors.forename: I
authors.initials: I
authors.lastname: Minami
authors.forename: K
authors.initials: K
authors.lastname: Oogai
authors.forename: T
authors.initials: T
authors.lastname: Nemoto
authors.forename: T
authors.initials: T
authors.lastname: Nakamura
authors.forename: Y
authors.initials: Y
authors.lastname: Igarashi
authors.forename: N
authors.initials: N
authors.lastname: Wakabayashi
mesh_terms: D000054:Acceleration; D000328:Adult; D000465:Algorithms; D001696:Biomechanical Phenomena; D002638:Chewing Gum; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008334:Mandible / Q000502:physiology*; D008409:Mastication / Q000502:physiology*; D009068:Movement; D012984:Software; D014465:Ultrasonics
chemical_list: D002638:Chewing Gum