Effect of Food Size on the Movement of the Mandibular First Molars and Condyles during Deliberate Unilateral Mastication in Humans

Abstract

To date, the effect of food size on the movement of the mandibular first molars and condyles during chewing has not been fully examined due to methodological problems. The purpose of the present study was to examine the previously unknown effect of food size on masticatory jaw movement. Using a face bow, light-emitting diodes, and optical cameras, we recorded, in 16 young adults with good occlusion, mandibular movement for the first 10 strokes during the unilateral chewing of similarly shaped hard gummy jellies weighing 5 g and 10 g, respectively. The chewing cycle time for the 10-g jelly was significantly longer than that for the 5-g jelly. The jaw-closing and -opening maximum velocities, gapes at the maximum velocities, and maximum gape were significantly faster and larger when 10-g gummy jellies were chewed, compared with results with 5-g jellies, at the mandibular first molar on the chewing side and the condyle on the non-chewing side. With the exception of the velocity, similar tendencies were observed at the molar on the non-chewing side. However, such significant differences were not detected at the condyle on the chewing side. The mandibular first molar on the chewing side was that most affected by food size, and the mean value of the maximum gape coincided approximately with the height of each jelly. These results suggest that humans chew hard coherent food such that the mandibular teeth that come into contact with the food open to a height equivalent to that of the food bolus, and that the changes in movement of the other parts of the mandible are minimized, ensuring efficient mastication.

A novel standard food model to analyze the individual parameters of human mastication

“…The separation of the working side molars is closely related to the size of the food bolus. This supports the hypothesis, that the jaw opening muscles are subconsciously controlled in a way, the mouth opens to the minimum level required for chewing, to allow effective mastication patterns [9]. Occlusion, occlusal interferences, and the severity of TMD seem to correlate with mastication: the higher the number of occlusal interferences and TMD severity, the longer the chewing time and the more distinct is the shift to an atypical chewing pattern [1].…”

Effects of Cross-sectional Area on Human Bite Studied with Raw Carrot andSurimiGel

“…Our findings were consistent with previous reports that neighter food texture nor size influenced chewing rhythm, unlike another mastication parameters. 6,9) Active stress remained almost constant for different cross-sectional areas, but was definitely different between the two foodstuffs. Food hardness is perhaps sensed by the magnitude of sensation from periodontal ligaments corresponding to active stress as well as by muscle spindles.…”

“…As we encounter more difficulty chewing food when the size of the food increases, 7) the relationships between food size and masticatory variables has been studied by EMG and jaw-kinematics. [8][9][10] Miyawaki et al compared chewing behaviors for 10 g and 5 g gummy jelly samples and reported that the larger food sample evoked greater jaw movement and higher EMG activity, but did not change chewing rhythm. 9,10) In such experiments using samples with a definite weight, the size effects involve both the cross-sectional area and the thickness of a specimen.…”

“…[8][9][10] Miyawaki et al compared chewing behaviors for 10 g and 5 g gummy jelly samples and reported that the larger food sample evoked greater jaw movement and higher EMG activity, but did not change chewing rhythm. 9,10) In such experiments using samples with a definite weight, the size effects involve both the cross-sectional area and the thickness of a specimen. The objective of this study was to investigate the influence of the cross-sectional area of food samples separately from that of thickness.…”

Mouthful Size Effects on Mastication Effort of Various Hydrocolloid Gels Used as Food Models

“…A larger size of sample often results in a longer period of oral processing, larger number of chewing, and higher EMG amplitude (Dantas and Dodds, 1990;Palmer et al, 1999;Miyawaki et al, 2000;Kohyama et al, 2005bKohyama et al, , 2007aWoda et al, 2006;Miyaoka et al, 2010;Ashida et al, 2010). We compared EMG variables during free eating of rice gruel (5 g and 10 g), and found that 10 g gruel exhibited significantly higher EMG variables corresponding to mastication time such as number of chews, chewing time, and total muscle activity than 5 g. However there were no significant differences between 5 g and 10 g in EMG variables per chew such as EMG amplitude, duration, muscle activity or muscle work, and chewing cycle (Kohyama and Nakayama, 2004).…”