Dynamics of the Human Masticatory System

Abstract

ABSTRACT:In this review, the movement characteristics of the human masticatory system are discussed from a biomechanical perspective. The discussion is based upon the three fundamental laws of mechanics applied to the various anatomical structures that are part of the masticatory system. An analysis of the forces and torques applied to the mandible by muscles, joints, articular capsules, and teeth is used to assess the determinants of jaw movement. The principle of relating the interplay of forces to the center of gravity of the lower jaw, in contrast to a hinge axis near its joints, is introduced. It is evident that the muscles are the dominant determinants of jaw movement. The contributions of the individual muscles to jaw movements can be derived from the orientation of their lines of action with respect to the center of gravity of the lower jaw. They cause the jaw to accelerate with six degrees of freedom. The ratio between linear and angular accelerations is subtly dependent on the mass and moments of inertia of the jaw, and the structures that are more or less rigidly attached to it. The effects of articular forces must be taken into account, especially if the joints are loaded asymmetrically. The muscles not only move the jaw but also maintain articular stability during midline movements. Passive structures, such as the ligaments, become dominant only when the jaw reaches its movement boundaries. These ligaments are assumed to prevent joint dislocation during non-midline movements.

Mechanical Stretch Increases the Proliferation While Inhibiting the Osteogenic Differentiation in Dental Pulp Stem Cells

“…13 Mechanical stress is an essential biological stimulation, and mechanical loading plays an important role in regulating the function of mesenchymal stem cells. 14 The type of mechanical stress are varied, such as fluidshear stress, compression, hydrostatic pressure, and uniaxially vertical and horizontal stretch.…”

A Conceptual Study on Kaphaja Shiroroga with Special Reference to Sinusitis

“…Both the LP and the PM are involved in the horizontal movement of the mandible; the LP moves the mandible on the opposite side of its contraction while the PM pulls the mandible forward [20]. The PM belongs to the group of the elevator muscles of the mandible, while the LP is part of the group of muscles that depress the mandible [21].…”

Articular Eminence Inclination in Medieval and Contemporary Croatian Population

“…Masticatory system includes organs and structures which are primarily functioning in mastication 1,2 . Mastication, the action of breaking down of food, preparatory to deglutition, is one of the most important functions of the masticatory system 2 , thereby multiple muscle groups interact and produce forces 3 .…”