Introduction

Tactile and Thermal Sensations

Means of study of sensation, and general anatomical pathways involved. Theories of cutaneous sensation. Morphological and functional characteristics of facial and intraoral receptors - e.g. periodontal. Trigeminal tactile and thermal paths and properties of trigeminal CNS neurones. Marked tactile and thermal sensitivity of orofacial area compared to other parts of body. Psychophysics, orofacial stereognosis, tactile thresholds, two-point discrimination. Significance of orofacial sensation in clinical dentistry.

Pain

Tooth

Neural innervation of pulp - fibre size, nerve terminals, relationship to odontoblasts. Mechanical and thermal sensitivity of dentine and responses of pulpal afferents. Evidence for innervation of dentine. Theories of dentinal sensitivity - Neural theory - histological, clinical, pharmacological and neurophysiological studies. Other theories of dentinal sensitivity, e.g. Hydrodynamic theory, Transmembrane Potential theory - possible role of odontoblasts as transducers. Pharmacological and clinical correlates. Pulp representation in CNS. Pulp testers and localization of pulpal sensation. Is pain the only sensation evoked from pulp? Blood supply and haemodynamics of the pulp.

Taste

Taste buds - peripheral innervation and mechanisms of taste. CNS pathways and mechanisms involved. Four submodalities of taste. Effects on taste sensation of age, dentures, temperature, saliva, oral hygiene, local anaesthetics, etc.

Periodontal Membrane

Innervation - histological and functional aspects. Periodontal receptor characteristics - adequate stimulus and directional sensitivity, response properties, receptive filed, and CNS pathways.

Role of periodontal receptors in oral sensation and jaw reflexes, and relation to dental treatment procedures - tactile thresholds, hardness and texture, interdental size discrimination, articulation, pain, protection, etc. Other receptors possibly involved in some of these functions, e.g. TMJ, periosteal. Blood supply and haemodynamics.

Temporomandibular Joint

Anatomy - blood supply, innervation. Receptor types - adequate stimulus, discharge characteristics, CNS pathways. Their role in sensory functions (interdental size, mandibular position, pain) and other TMJ functions - kinesthetic, protective reflex, etc., and clinical implications.

Muscle and Orofacial Movements

Properties of muscle - contractile and visco-elastic elements. Active and passive tension, tone. Muscle receptors (e.g. muscle spindle, Golgi tendon organ) - histological and neurophysiological studies. Role in conscious sensation (pain, ? proprioception). Concepts of motor unit and neuromuscular transmission. Pathophysiology of muscle activity. The clinical EMG - method, uses, limitations. Orofacial motor pathways and reflex activity (compared with spinal) and relationships to jaw and oral movements.

Examples of jaw, facial and tongue muscle reflexes. Concepts of supportive and protective reflexes. Significance in simple reflex activity, e.g. occlusal protection, airway maintenance. Provision of reflex circuitry for more complicated reflexes, e.g. coughing, gagging, etc., and complex muscle synergies, e.g. mastication, swallowing, suckling, speech, etc.

Sensory and CNS control of muscle activity - role of muscle spindles, TMJ, periodontium, and higher centres (e.g. cerebral cortex, reticular formation) in motor control, i.e. in regulating orofacial motor patterns. Clinical significance of these peripheral and central neural influences in normal and abnormal orofacial motor functions, e.g. monobloc therapy, occlusal adjustment, bruxism, cerebral palsy, tongue thrusting and tooth stability - implications of jaw, tongue and facial muscle equilibrium, relation to occlusal and skeletal balance.