Sensory-Motor Modulation in the Masticatory Apparatus and in Temporomandibular Disorders: from Basic Science to Clinical Practice

The jaw sensory-motor system is involved in a wide range of functions: respiration, deglutition, mastication/sucking, verbal/non-verbal expression and protective mechanisms (coughing, prevention from aspiration, …). Some of these tasks may be altered/impaired in temporomandibular disorders that may even impair feeding behaviour. It is suggested that motor maladaptation is due to poor sensory-motor control. Indeed, the excitability of trigeminal reflexes may be modified both in experimental and in clinical painful conditions. However, this research field is a conflicting area. Thus, the aim of this narrative review is first to address the trigeminal sensory-motor control in a healthy state in mastication with a special focus on the type of control either feedback or feedforward that are not mutually exclusive but cooperate. Secondly, it is considered whether there is chronic pain-related modulation of trigeminal sensory-motor control in temporomandibular disorders. Some additional data concerning the spinal system in other musculoskeletal disorders are considered. Mostly, proprioceptive feedback control, i.e. stretch reflex and feedforward control are depressed in musculoskeletal disorders. Protective or withdrawal reflex threshold may be decreased. It would favour protective behaviour. This knowledge could be of clinical interest in functional rehabilitation of musculoskeletal disorders such as temporomandibular disorders. It is suggested that a highly regular rhythm of movement repetitions would improve efficiency of feedback and feedforward control and finally muscle co-ordination. A better knowledge of sensory-motor regulation could also help to understand what is referred clinically to “(mal)adaptation” in oral rehabilitation procedures involving some changes in dental occlusion.