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.

The effect of food bolus location on jaw movement smoothness and masticatory efficiency

“…Each recording was performed over only one session to avoid changes in the subject’s skilfulness of chewing through repetition of the task too many times. The reliability of this procedure was confirmed in a previous study (23).…”

“…Exclusion criteria were as follows: history of temporomandibular muscle and joint disorders (TMJD) and severe periodontal disease, dental caries. Some of the procedures have been previously described (4, 23).…”

“…Triaxial piezoelectric accelerometers (TPAs) (23, 24) with an output of 500 mV ms −2 were chosen for their size (4·6 × 4·6 × 1·3 mm), low inertial mass (0·8 g) and broadband linearity (direct current to 5 kHz). The accelerometer was attached by means of a double‐sided tape, pasted on the surface of medicine tape (Fixmull stretch § ) attached to the skin of the jaw mentum of each subject.…”

Jaw‐movement smoothness during empty chewing and gum chewing

“…It has been reported that the jaw‐opening phase in gum chewing is associated with minimum smoothness because of the adhesive nature or viscosity of gum and the cycle‐by‐cycle modifications of the jaw, tongue, and lip movements during jaw opening . The observation that jerk‐cost was higher during the opening B phase and the closing A phase of gum chewing than during empty chewing suggests that the influence of the mechanical effects of tooth contact on jerk‐cost is not restricted just to the occlusal phase of chewing, but rather the effect influences the entire opening and closing phases of chewing.…”

Recording and Measuring of Jaw Movements using a Computer Vision System

“…These forces may be static, like the constant force of gravity, or they could be dynamic caused by moving or vibrating the accelerometer. They are undesirable for detecting mandibular movement as they do not produce stable recordings of the static position of the mandible [6,7,8].…”