Dynamic stereometry of the temporomandibular joint

Abstract

Studies on jaw kinematics have provided a good understanding of the motion of the mandible in space, but are of little biomechanical relevance because they could not relate the movements to anatomic structures. This is possible by the combination of three-dimensional reconstructions of the temporomandibular joint (TMJ) anatomy with jaw motion recordings. This technique allows us to analyze the variation of the relationship between the articular surfaces, providing indirect insight into disk deformation during function and parafunction as well as TMJ loading. As far as the variation of the condyle-fossa distance is concerned, data indicated that during chewing the distance was smaller 1) on closing than on opening; 2) on the balancing than on the working side; and 3) during chewing of hard than soft food. Moreover, during a forceful static biting, the condyle-fossa distance decreased more on the contralateral, i.e. on the balancing side than on the working side. The decrease was related to the degree of clenching force. These results support the content that both condyles are loaded during chewing and the balancing side joint more than the working one. Biomechanically, the development of osteoarthrosis is more likely related to the magnitude and frequency of stresses applied on the cartilage. Joint movements produce tractional forces that may cause shear stresses contributing to cartilage wear and fatigue. Tractional forces are the result of frictional forces caused by the cartilage surface rubbing and of plowing forces caused by the translation of a stress-field through the cartilage matrix, as the intra-articular space changes during motion. Translation of the stress-field in mediolateral direction seems to be particularly important for the integrity of the TMJ disk because of its anisotropic properties. Dynamic stereometry showed that stress-fields translate in mediolateral direction during opening/closing, protrusion and laterotrusion, and that their translatory velocity varies intraindividually and with the rate of the condylar movement. Furthermore, the results seem to indicate that the lateral area of the TMJ disk is more often exposed to shear stresses caused by stress-field translation than the medial one. In conclusion, dynamic stereometry provides a good visualization of the movement of the condyles in the respective fossae. This helps improving our understanding for the complexity of condylar movements. The technique may also contribute to ameliorate our knowledge of TMJ biomechanics and therefore of the etiology of degenerative joint diseases and possibly also of internal derangement.

Coupling plowing of cartilage explants with gene expression in models for synovial joints

“…In our previous work, the complex TMJ disc deformation, and thus indirectly its loading, has been studied quantitatively from in vivo data by coupling magnetic resonance imaging (MRI) and jaw-tracking of human subjects (Gallo et al, 2000;Gallo, 2005;Gallo et al, 2006;Palla et al, 2003).…”

Neuromuscular control of balancing side contacts in unilateral biting and chewing

“…Based on biomechanical reasoning, this could be viewed as a protective effect: With unilateral loading, BS lever arms of muscles are several times longer than WS lever arms [41]. Hence, if masseters on both sides act equally, as usually observed with bigger jaw gapes [36], the jaw tilts about the bitten object and lifts on the BS [27][28][29][30][31]. If the height of the WS fulcrum drops below an individual limit, the BS teeth apparently can come into contact.…”

“…In this approximately isometric contraction [18,23,24], the jaw can tilt [15,18,25] about the compressed bolus which separates the teeth by some tenth of millimeters [26]. The tilting implies a slight elevation of the BS mandibular arch [27][28][29][30][31] which could result in direct BS tooth contacts [15,25]. To prevent occlusal damage, the BS force had to be limited while high chewing force [32] is applied on the working side (WS).…”

A Model System of the Dynamic Loading Occurring in Synovial Joints: The Biological Effect of Plowing on Pristine Cartilage

“…In a previous study, we studied the temporomandibular joint (TMJ) disk deformations that occur during mandibular function by means of novel, 3-dimensional modelling software that processes data acquired by magnetic resonance imaging and jaw tracking (a system that allows observation of mandibular movement dynamically) [Palla et al, 2003;Gallo, 2005;Gallo et al, 2006]. These TMJ disk measurements were used to develop a rolling/plowing explant test system that is able to mimic the in vivo plowing effect that results from the combination of compression and sliding of the mandibular condyle on the TMJ cartilage disk [Colombo et al, 2011].…”