Pain and pain pathways final

DENTAL PAIN

1. Pain and Pain Pathways Anjali Savita MDS I Dept of Conservative Dentistry and Endodontics

2. “I don’t accept the maxim ‘there is no gain without pain’, physical or emotional. I believe it is possible to develop and grow with joy rather than grief; however when pain comes my way, I try to get the most growth out of it” - Alexa Mclaughlin

3. Contents Introduction Definition History Incidence Related Terms Characteristics of pain Classification of pain Pain receptors Pathway of pain sensation Theories of pain Pain pathway of Maxillofacial Region Dental pain References

4. Introduction Pain is the commonest symptom which physician are called upon to treat. Pain is an intensely subjective experience, and is therefore difficult to describe. Physiology of pain has taught us a lot about neural function in general. It has two universal features. First, its an unpleasant experience. Second, it is evoked by a stimulus which is actually or potentially damaging to living tissue.

5. That is why, although it is unpleasant, pain serves a protective function by making us aware of actual or impeding damage to the body. Like all sensory experiences, pain has two components, the first component is awareness of painful stimulus and second one is emotional impact(or effect) evoked by experience. While the awareness is localized to the area stimulated, experience involve the whole being. That is why when a finger is hurt, the whole person suffers.

6. Definition of Pain Pain is “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage”. - International association for the study of Pain. “An unpleasant emotional experience usually initiated by noxious stimulus and transmitted over a specialized neural network to the CNS where it is interpreted such as.” - Monheim’s textbook of local anaesthesia

7. History Derived from Latin word “poena” meaning punishment from God. Homer thought pain is due to arrows shot by God. Aristotle who was first to distinguish five physical senses considered pain to “ the passion of the soul” that somehow resulted from intensification of other sensory experience. Plato contented, pain and pleasure arose from within the body. Bible makes reference to pain not only in relationship to injury and illness but also an anguish of the soul.

8. Incidence of Pain According to Cohen- it was found that 21.8% of adult in the united states experiences orofacial pain symptoms within 6 months of study. The most common pain was toothache, which was estimated to have occurred in 12.3% of the population. Dental pain is highly prevalent among children, the association being most apparent in lower socioeconomic groups with reduced access to care. The prevalence of dental pain was 35% among all pain. Dental pain has been associated with many factors, such as low socioeconomic status, high levels of dental caries and restricted access to dental services.

9. Related Terms Allodynia Hyperalgesia and hypoalgesia Hyperpathia Causalgia Neuralgia

10. Characteristic of Pain Threshold and Intensity If the intensity of the stimulus is below the threshold(sub threshold) pain is not felt. As the intensity increases more and more, pain is felt more and more according to Weber- Fechner’s Law. As per this law magnitude of sensation felt is directly proportional to log of intensity of stimulus

11. Adaptation Pain receptors show no adaptation, so the pain continues as long as receptors are stimulated. Localization of pain Pain sensation is somewhat poorly localized, however superficial pain is comparatively better localized than deep pain. Influence of the rate of damage on intensity of pain If rate of damage(tissue injury) is high, intensity of pain is also high.

12. Classification of Pain Based on source/ location/ referral & duration Pain Visceral Acute / Traumatic pain Chronic pain Malignant pain /cancer pain Somatic Non- malignant benign pain Superficial Deep Musculo-skeletal Neuropath- ic

13. ACUTE PAIN Acute has a sudden onset, usually subsides quickly and is characterized by sharp, localized sensations with an identifiable cause. Lasts > 30 days and occurs after muscle strains and tissue injury such as trauma or surgery. A poorly treated pain can cause psychological stress and compromise the immune system due to the release of endogenous corticosteroids Acute pain is usually characterized by increased autonomic nervous system activity resulting in psychological symptoms such as anxiety Tachypnoea Tachycardia with hypertension Pallor Diaphoresis Pupil dilation

14. VISCERAL PAIN Visceral pain is a type of nociceptive pain that comes from the internal organs. Unlike somatic pain it is harder to pinpoint, described as general aching or squeezing pain It is caused by the activation of pain receptors in the chest, abdomen, or pelvic areas. In cancer patients pain is caused by tumor infiltration, constipation, radiation & chemotherapy.

15. SUPERFICIAL PAIN It is also known as cutaneous pain. It arises from superficial structures such as skin & subcutaneous tissues. It is a sharp, bright pain with a burning quality and may be abrupt or slow in onset. DEEP SOMATIC PAIN It originates in deep body structures such as periosteum, muscles, tendons, joints & blood vessels Strong pressure, ischemia, tissue damage act as stimuli for brain damage Radiation of pain from original site of injury occur.

16. CHRONIC PAIN Chronic pain is defined as pain lasting longer than 3 to 6 months. It begins when pain persists after the initial injury has healed. It is persistent or episodic pain of duration or intensity that adversely affects the function and well being of the patient. It may be nociceptive, inflammatory, neuropathic or functional in origin.

17. It occurs in 60-90 % of patients with cancer. Pain can be related to the tumor or cancer therapy or may be idiosyncratic. Pain may also be found at the metastasized regions and treatment interventions may activate peripheral nociceptors. Pain can be somatic/visceral CHRONIC NONCANCER PAIN Pain may last for many years and is considered progressive in nature. May be nociceptive, neuropathic or mixed in nature. CHRONIC MALIGNANT PAIN

18. NEUROPTHIC PAIN Neuropathic pain is a result of an injury or malfunction of the nervous system. It is described as Aching Throbbing Burning Shooting Tenderness/ sensitivity of skin

19. MUSCULOSKELETAL PAIN This a type of chronic non cancer pain occurring due to musculoskeletal disorders such as Rheumatoid arthritis Osteoarthritis Fibromyalgia Peripheral neuropathies

20. BASED ON TRANSMISSION FAST PAIN Felt about 0.1 sec after a painful stimulus is applied. It is described as sharp pain, pricking pain, acute & electric pain Fast sharp pain is not felt in most deeper tissues of the body. Due to activation of A δ fibres SLOW PAIN Usually begins after 1 sec or more and may range from seconds to minutes. Described as slow, burning, aching, throbbing, nauseous pain and chronic pain Associated with tissue destruction. Due to activation of C fibres

21. OTHER TYPES OF PAIN REFERRED PAIN Pain that originate due to irritation of a visceral organ and felt not in organ but in some other somatic structure as well which has innervated by the same neural segment. Usually applies to pain that originates from the viscera E.g. The pain associated with MI commonly is referred to the left shoulder arm, neck & chest. BREAKTHROUGH PAIN Pain is intermittent, transitory. Usually lasts from minutes to hours and can interfere with functioning. E.g. Neuropathic pain, Lower back pain

22. Practical clinical classification of cranio facial pain General Classification Origin of Pain Quality of Pain Extra cranial Structure Craniofacial region varies Referred pain from remote pathologic sites Distant organs and structures Aching and pressing Intracranial pathosis Brain and related structures Varies varies Neurovascular Blood vessels Throbbing, Pulsing, Pounding

23. General Classification Origin of Pain Quality of Pain Neuropathic Sensory nervous system Shooting, sharp, burning pain Causalgic Sympathatic nervous system Burning Muscular Muscles Deep aching, tight

24. OROFACIAL PAIN CLASSIFICATION (OKESON) AXIS I (physical conditions) Somatic pain Superficial Somatic pain Cutaneous pain Mucogingival Deep Somatic Pain Muscle pain TMJ pain Osseous pain Periodontal pain Visceral pain Pulpal pain Vascular pain Neurovascular pain Visceral mucosal pain Glandular, ocular, auricular pain

25. AXIS II (psychologic conditions) Mood disorders Anxiety disorders Somatoform disorders Other conditions Psychologic factors affecting a medical condition

26. Pain Receptors NOCICEPTORS or PAIN RECEPTORS are sensory receptors that are activated by noxious insults to peripheral tissues. The receptive endings of the peripheral pain fibres are free nerve endings. These receptive endings are widely distributed in the Skin Dental pulp Periosteum Meninges

27. SILENT NOCICEPTORS These receptors activated at the time of inflammation only. Upto 40% of C fibers and 30% of A δ fibers are silent nociceptors. UNIMODAL NOCICEPTORS These receptors respond exclusively to one modality i.e. either noxious chemical or heat stimuli. POLYMODAL NOCICEPTORS These receptors are sensitive to several varieties of noxious stimuli These do not have a specialized and simple nerve endings in the periphery.

28. NERVE FIBRES INVOLVED IN PAIN TRANSMISSION A FIBRES A – BETA FIBRES Large Myelinated Fast conducting Low stimulation threshold Respond to light touch C FIBRES Small & unmyelinated Very slow conducting Respond to all types of noxious stimuli Transmit prolonged dull pain Require high intensity stimuli to trigger a response A – DELTA FIBRES Small Lightly Myelinated Slow conducting Respond to heat, pressure, cooling & chemicals Sharp sensation of pain

29. PATHWAYS OF PAIN SENSATION The pathways of pain sensation are as follows Pathway from skin & deeper tissues Pathway from face – pain sensation is carried by trigeminal nerve Pathway from viscera – pain sensation from thoracic & abdominal viscera are transmitted by sympathetic nerves & from oesophagus, trachea & pharynx by glossopharyngeal nerves Pathway from pelvic region – conveyed by sacral parasympathetic nerves

30. PATHWAY FROM SKIN & DEEPER TISSUES FIRST

31. PAIN PATHWAYS ASCENDING PAIN PATHWAY

32. DESCENDING INHIBITORY PAIN PATHWAY

33. Pain pathway of Maxillofacial region 5 TH cranial nerve or trigeminal nerve is the principle sensory nerve of head region. Any stimulation in the area of trigeminal nerve is first received by both myelinated and unmyelinated fibers, and conducted as an impulse along afferent fibers of ophthalmic, maxillary and mandibular branches into semilunar and gasserian ganglion. Pain impulse descend from the pons by spinal tract fibers of trigeminal nerve through the medulla

34. MECHANISMS OF PAIN Pain sensation involves a series of complex interactions between peripheral nerves & CNS. Pain sensation is modulated by excitatory and inhibitory NTs released in response to stimuli. Sensation of pain is composed of 4 basic processes Transduction Transmission Modulation Perception

35. TRANSDUCTION Activation of nociceptor Intense thermal and mechanical stimuli, noxious chemicals, noxious cold Stimulation of inflammatory mediators Damaged tissue release bradykinin, potassium, histamine, serotonin and arachidonic acid. Arachidonic acid produce prostaglandins and leukotrienes.

36. TRANSMISSON Process by which peripheral nociceptive information is relayed to CNS. First order neuron synapses with the secondary order neuron from where impulse is carried to higher structures of brain. Repeated or intense C fibre activation brings specific changes on N-methyl-D-aspartate receptors resulting in central sensitization, thus, response of second order neurons increases as well as size of the receptive field also increases.

37. MODULATION It is the mechanism by which transmission of impulse to the brain is either inhibited or excitated. Endogenous opioid peptides are naturally occurring paindampening neurotransmitters and neuromodulators employed in suppression and modulation of pain because they are present in large quantities in areas of brain associated with these activities. PERCEPTION It is the subjective experience of pain. It is the sum of complex activities in CNS that may shape the character and intensity of pain perceived and ascribe meaning to pain.

38. PAIN THEORIES Pain theories are proposed to offer the possible physiologic mechanisms involved in pain. They are as follows Specificity theory Pattern theory Neuro-matrix theory Gate control theory

39. SPECIFICITY THEORY Proposed by Johannes Muller in 1842. According to this theory pain is a specific modality equivalent to vision and hearing. This theory states pain as separate modality evoked by specific receptors(free nerve endings) that transmit information to pain centers or regions in the forebrain where pain is experienced.

40. PATTERN THEORY Proposed by Goldscheider in 1894. According to this theory pain sensation depends on Spatio-temporal pattern of nerve impulse reaching the brain. According to Woddell (1962) warmth, cold and pain are words used to describe reproducible spatio temporal pattern or codes of neural activity evoked from skin by changes in environment. The precise pattern of nerve impulse entering the CNS will be different for different regions, and will vary for person to person because of normal anatomical variations.

41. NEUROMATRIX THEORY This theory was put forward by MELZACK This theory explains the role of brain in pain as well as the multiple dimensions and determinants of pain. According to this theory the brain contains a widely distributed neural network called the body self Neuromatrix that contains somatosensory, limbic, & Thalamocortical components The body self Neuromatrix involves multiple input sources such as Somatosensory inputs Other impulses/ inputs affecting the interpretation of the situation Various components of stress regulation systems Intrinsic neural inhibitory modulatory circuits

42. GATE CONTROL MECHANISM Proposed by MELZACK & WALL IN 1965. According to this theory, the pain stimuli transmitted by afferent pain fibres are blocked by GATE MECHANISM located at the posterior gray horn of the spinal cord If the gate is open pain is felt, and if the gate is closed pain is suppressed Impulses in A – δ & C – fibres can be blocked by modulated by A – β activity that can selectively block impulses from being transmitted to the transmission cells in the spinal cord and then to CNS resulting in no pain

43. ROLE OF BRAIN IN GATE CONTROL MECHANISM Minimizing the severity & extent of pain

44. Tooth pulp pain Exposure of dentinal tubules causes toothache & other non noxious sensation. Both Aδ & C fibers respond to stimuli in dentine Transmission of stimuli across dentin, mediated by movement of fluid in dentinal tubules. Fibers terminate at medullary dorsal horn & synapse and also at trigeminal sensory nucleus

45. From trigeminal nucleus send to thalamus & sensory cortex. Pulpal innervation are capable of regenerating & reinnervating

46. Conclusion Anxiety is determinant for pain during dental care & pain is related to local anesthetic procedures. There are evidences that dentists attitude are determinants for pain.

47. References Essential of oral physiology- Robert M Bradley Textbook of medical physiology- Guyton & Hall Essential of medical physiology- K.Sembulingam & Prema Sembulingam . Textbook of human physiology- S Chand Determinants of painful experience during dental treatment- Ruth Suzanne et al Rev.Dor 2012;13(4) Case report study on Brown sequard syndrome- Ponachi et al Neurology Asia 2007;12;65-67 Anatomy, physiology & pharmacology of pain- Ryan Moffat , Colin P.Rae anesthesia & intensive care medicine; 2010;12(1)