ORAL PHYSIO UNIT III LESSON 1.pdf

Iloilo Doctors’ College College of Dentistry West Timawa, Molo, Iloilo City DENT 306: Oral Physiology and Occlusion Unit III - Physiology of Receptors Associated with the Oral Cavity Lesson 1 PAIN FROM DENTAL STRUCTURE...

Iloilo Doctors’ College College of Dentistry West Timawa, Molo, Iloilo City DENT 306: Oral Physiology and Occlusion Unit III - Physiology of Receptors Associated with the Oral Cavity Lesson 1 PAIN FROM DENTAL STRUCTURES Prepared by Ma. Lorelei D. Fuentes, DMD Clinical Instructor DENT 306: Oral Physiology and Occlusion Toothache Perhaps one of the most excruciating forms of pain Invariably causes the sufferer to seek out a dentist The tooth has within it a powerful nociceptive capacity which warns of damage to the dentition Several types of stimuli cause the onset of toothache, such as hot fluids, concentrated chemicals (e.g. candy dissolved in saliva), or cold air Unit III - Physiology of Receptors Lesson 1 - Pain from Dental Structures Associated with the Oral Cavity DENT 306: Oral Physiology and Occlusion Tooth Sensitivity The sensitivity of a tooth has clinical diagnostic significance Older diagnostic tests utilized the application of cold (ethyl chloride sprayed on a cotton pledget) or hot (hot composition impression material) to a tooth as a sign of vitality Electrical Stimulation Electrical stimulation of a tooth with a modern “pulp tester” is now used to diagnose the viability of the pulp A tooth does not have to be diseased to be sensitive to electrical stimulation It is possible to evoke dental pain from sound teeth by electrical stimuli Unit III - Physiology of Receptors Lesson 1 - Pain from Dental Structures Associated with the Oral Cavity DENT 306: Oral Physiology and Occlusion Neuroanatomical Considerations The sensation of toothache originates in receptors or neural structures in either dentin or pulp This is known because the removal of pulp causes a loss of tooth sensitivity, and toothache results only when dentin or pulp is stimulated Enamel and cementum contain no neural elements and are insensitive to stimulation Although enamel and cementum are devoid of nerve, pulp and dentin are both innervated Unit III - Physiology of Receptors Lesson 1 - Pain from Dental Structures Associated with the Oral Cavity DENT 306: Oral Physiology and Occlusion Branches of the autonomic and trigeminal nerves enter the apical foramen of the tooth and branch repeatedly as they pass toward the coronal part of the pulp cavity All stimuli used to excite dental nerve fibers may do so by activating pulpal nerves directly Raised intrapulpal pressure results in increased neural activity in pulpal nerves An increase in pulpal pressure results from applying heat to a tooth Changes in pulpal circulation (e.g. by sympathetic nerve stimulation), which presumably alter intrapulpal pressure, also change pulpal neural activity The clinical presentation of throbbing dental pain may be due to pressure changes in the pulp Unit III - Physiology of Receptors Lesson 1 - Pain from Dental Structures Associated with the Oral Cavity DENT 306: Oral Physiology and Occlusion Behavioral Studies of Dentin Sensitivity Chemical Stimulation of Dentin Application of a sweet substance to exposed dentin produces pain Often, this is the first symptom of cariously exposed dentin or a leaking restoration For example, chewing candy may suddenly promote an acute toothache It has been shown that the frequency with which chemical solution reduces pain when placed on exposed dentin is related to the osmotic pressure of the chemical stimulus The greater the osmotic pressure, the greater the number of times a human volunteer will report a painful sensation Unit III - Physiology of Receptors Lesson 1 - Pain from Dental Structures Associated with the Oral Cavity DENT 306: Oral Physiology and Occlusion Behavioral Studies of Dentin Sensitivity Thermal Stimulation of Dentin Toothache is often initiated when an individual takes in a draft of cold air Stimulation of intact teeth with heat can also produce pain Effects of Touch, Airstream, and Drying It has been shown that pain is produced when dentin is subjected to pressure changes, a stream of air, or touching with absorbent paper Unit III - Physiology of Receptors Lesson 1 - Pain from Dental Structures Associated with the Oral Cavity DENT 306: Oral Physiology and Occlusion Innervation of Dentin Dentin is sensitive because of the presence of nerve endings in the dentinal tubules in the inner dentin and predentin layers These nerve endings are closely associated to the odontoblastic processes Unit III - Physiology of Receptors Lesson 1 - Pain from Dental Structures Associated with the Oral Cavity DENT 306: Oral Physiology and Occlusion Theories of Pain Transmission through Dentin 1. Direct Neural Theory 2. Transduction Theory 3. Hydrodynamic Theory Unit III - Physiology of Receptors Lesson 1 - Pain from Dental Structures Associated with the Oral Cavity DENT 306: Oral Physiology and Occlusion Direct Neural Theory Nerve endings in the dentin when stimulated evoke painful responses No nerve fibers in the DEJ Dentin and pulp contain neural elements that produce sensitivity when stimulated Transduction Theory Presumes that the odontoblast process is the primary structure excited by the stimulus and the impulse is transmitted to the nerve endings in the inner dentin Not a popular theory since there are no neurotransmitter vesicles in the odontoblast process to facilitate the synapse Unit III - Physiology of Receptors Lesson 1 - Pain from Dental Structures Associated with the Oral Cavity DENT 306: Oral Physiology and Occlusion Hydrodynamic or Fluid Theory Most popular theory Various stimuli such as heat, cold, air blast, desiccation, and mechanical or osmotic pressure affect fluid movement and dentinal tubules in odontoblasts This fluid movement, either inward or outward, stimulates the pain mechanisms in the tubules by mechanical disturbance of the nerve closely associated with the odontoblast and its processes The said movement of fluid disturbs the pulpal environment and is sensed by the Plexus of Raschkow in the pulp These endings may not act as mechanoreceptors as they are affected by mechanical displacement of the tubular fluid Odontoblasts are mechanoreceptors Unit III - Physiology of Receptors Lesson 1 - Pain from Dental Structures Associated with the Oral Cavity DENT 306: Oral Physiology and Occlusion Age and Functional Changes in Dentin Vitality of Dentin Odontoblasts have the capacity to react to physiologic and pathologic stimuli In defense against these stimuli, there is the formation of dead tracts, sclerotic or transparent dentin, and reparative or tertiary dentin Unit III - Physiology of Receptors Lesson 1 - Pain from Dental Structures Associated with the Oral Cavity DENT 306: Oral Physiology and Occlusion Dead Tracts Due to the disintegration or death of odontoblasts, empty tubules are filled with air White in reflected light Black in transmitted light Initial step in the formation of sclerotic dentin Unit III - Physiology of Receptors Lesson 1 - Pain from Dental Structures Associated with the Oral Cavity DENT 306: Oral Physiology and Occlusion Sclerotic or Transparent Dentin Deposition of collagen fibrils and apatite crystals in dead tracts Dentin tubules become more mineralized like peritubular dentin thus it becomes transparent Unit III - Physiology of Receptors Lesson 1 - Pain from Dental Structures Associated with the Oral Cavity DENT 306: Oral Physiology and Occlusion Reparative or Tertiary Dentin 1. Noxious Stimuli 2. Death of Odontoblasts 3. Formation of Reparative Dentin 4. Seal Off the Site of Injury 5. Promote the Healing Process of the Pulp Has fewer and more twisted tubules than normal dentin Unit III - Physiology of Receptors Lesson 1 - Pain from Dental Structures Associated with the Oral Cavity DENT 306: Oral Physiology and Occlusion Phases of Dentinogenesis Dentin Matrix Formation 4 microns of pre-dentin is laid down per day Starts at cusp tips (Korff’s Fibers) Deposition of collagenous matrix Cell recedes leaving a single extension (odontoblastic processes) Mineralization As collagen fibers are deposited, hydroxyapatite crystals are laid down with it Gradual calcification follows 1. Differentiation of Ameloblasts 2. Differentiation of Odontoblasts 3. Dentin Matrix Formation 4. Enamel Matrix Formation Unit III - Physiology of Receptors Lesson 1 - Pain from Dental Structures Associated with the Oral Cavity DENT 306: Oral Physiology and Occlusion Clinical Considerations 1. When 1 mm of dentin is exposed, about 300,000 odontoblast cells are damaged. 2. The rapid spread of caries in the dentin is due to the tubule system. 3. Undue trauma from operative dental procedures may cause damage to the pulp. 4. Reparative dentin formation can be stimulated by cavity lining materials. Unit III - Physiology of Receptors Lesson 1 - Pain from Dental Structures Associated with the Oral Cavity  Iloilo Doctors’ College College of Dentistry West Timawa, Molo, Iloilo City DENT 306: Oral Physiology and Occlusion Unit III - Physiology of Receptors Associated with the Oral Cavity Lesson 1 PAIN FROM DENTAL STRUCTURES Prepared by Ma. Lorelei D. Fuentes, DMD Clinical Instructor