Relevance of mandibular helical axis analysis in functional and dysfunctional TMJs

A dynamic model of jaw and hyoid biomechanics during chewing

“…Its incisor-point, condylar-point and hyoid movements closely matched targets based on experimental studies by Ahlgren, (1976), Gallo, (2005, Gibbs and Lundeen, (1982), Hiiemae and Palmer (2003), Gallo et al, (2000Gallo et al, ( , 2006, Hiiemae et al, (2002) and Palla et al, (2003). Also, its condylar-point movements were consistent with observed condylar motions during chewing (Gallo et al, 2000).…”

“…Viewed laterally, the opening and closing trajectories had to approximate a perpendicular to the occlusal plane. During early closing, the incisor's deviation to the right had to reach 5 mm, with an earlier return of the ipsilateral than of the contralateral condylar-point (Gallo, 2006). The hyoid's target trajectory included a midline, upward and forward excursion 3-5 mm, completed by the end of jaw-opening (Hiiemae et al, 2002).…”

“…The mandibular condyles' lateral translation is minimal (0.4-0.6 mm) during chewing and other tasks (Gibbs and Lundeen, 1982;Payne, 1997;Okano et al, 2002;Otake et al, 2002;Miyawaki et al, 2004;Huang et al, 2006). During bolus compression therefore, the jaw rotates around its ipsilateral condyle as the contralateral condyle returns to its articular fossa (Gibbs and Lundeen, 1982;Gallo et al, 2000Gallo et al, , 2006Palla et al, 2003;Gallo, 2005;Miyawaki et al, 2001).…”

Tractional Forces on Porcine Temporomandibular Joint Discs

“…From a clinical perspective, these findings may be applied to future work which focuses on the identification of susceptible individuals, tasks, and behaviors that predispose to failure of the TMJ disc. The localization of internal strain energy in TMJ discs may be highly variable, given the variability in velocity and aspect ratios of the trans lating stress-field (Gallo et al, 2000) and the mechanical work done to the TMJ disc (Gallo et al, 2006) shown by living humans performing the same ordinary tasks. More in vivo physical data and knowledge of the cellular and molecular consequences are needed to establish thresholds for fatigue failure of the TMJ disc.…”

“…Therefore, plowing forces are the predominant causal element leading to fatigue. Plowing forces likely occur in vivo, because stress-field translation has been demonstrated along the mediolateral axis of TMJ discs in living humans (Gallo et al, 2000(Gallo et al, , 2006. Calculations of mechanical work done during similar tasks in different individuals (symmetrical/asymmetrical jaw-opening/-closing) indicated that energy input to the disc by mediolateral-stress-field translation varied by three orders of magnitude in different TMJs (Gallo et al, 2006).…”