DEFINITION OF PAIN

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 1994]

Or

Pain can also be defined as unpleasant emotional experience usually initiated by noxious stimulus and transmitted over a specialized neural network to the central nervous system where it is interpreted as such.

PAIN RELATED TERMS

ALGOGENIC: Causing pain

ALLODYNIA: Pain resulting from stimulus that does not normally provoke pain.

ANESTHESIA: Absence of all sensation

ANALGESIA: Absence of pain in response to stimulation that would normally be painful.

HYPERALGESIA: Is an increased response to a stimulus that is normally painful.

HYPOAESTHESIA: Is a decreased sensitivity to stimulation.

HYPERAESTHESIA: Is an increased sensitivity to simulation, excluding the special senses. (Hyperalgesia is special case of hyperaesthesia.)

NEURALGIA: Is pain in the distribution of a nerve.

NEUROPATHIC PAIN: Pain initiated or caused by primary lesion or dysfunction in the nervous system.

NEUROPATHY: Is a disturbance of function or pathologic change in a nerve

NOCICEPTOR: A receptor that is preferentially sensitive to noxious stimulus or to a stimulus that would become noxious if prolonged.

NEURAL PATHWAYS OF PAIN Field has described that the subjective experience of pain arises by four distinct process

• Transduction
• Transmission
• Modulation
• Perception

TRANSDUCTION is the process by which noxious stimuli lead to electrical activity in the appropriate sensory nerve endings. Due to several types of sensory organs that initiate the process of nociception.

TRANSMISSION Transmission refers to neural events that carry the nociceptive input into the central nervous system for proper processing. There are three basic components to the transmission system: 1. Primary afferent neuron 2. Second order neuron (carries the input to the higher centers) 3. Interactions of neurons between the thalamus, cortex and the limbic system as the nociceptive input reaches these higher centers.

MODULATION Modulation refers to the ability of the central nervous system to control pain transmitting neuron.

PERCEPTION The final process involved in the subjective experience of pain is perception. If nociceptive input reaches the cortex, perception occurs, which immediately initiates a complex interaction of neurons between the higher center of the brain. It is at this point that suffering and pain behavior begins.

 CENTRAL PROCESSING OF PAIN

PRIMARY PAIN: when site and the source of pain are in the same location it is called primary pain e.g. Finger cut

HETEROTROPHIC PAIN: when site of pain is not in the same location as the source of pain is called heterotrophic pain e.g.: Cardiac pain

GATE CONTROL THEORY In 1965 Melzack and wall introduced gate control theory as follows: The posterior horn of the spinal cord may be viewed as a gate, through which different kinds of sensations are entering, it can enter very well ,that is pain is felt by the subject Along with pain when touch sensation is also entering, the touch sensation may block the entry of the pain sensation resulting in reduction of pain perception

EVALUATION OF PATIENTS WITH FACIAL PAIN HISTORY chief complaint, history of present illness, past medical history, medications, reviews of systems, social and occupational history. It is important to obtain the patients description of pain, because – Primary Neuralgias are described as sharp shooting, lancinating pain. Vascular headaches are throbbing, Muscle Pain are dull aching and continuous one.

 INTRAORAL EXAMINATION is very vital.

CLASSIFICATION OF OROFACIAL PAIN

Classification of Pain by way of Pathology is often very helpful.

• D – DEGENERATIVE
• I – IMMUNOLOGICAL
• M – METABOLIC
• T – TRAUMATIC
• I – INFECTIVE
• N – NEOPLASTIC

While Orofacial Pain can be classified on basis of anatomical site of pain

I DISEASES OF THE MOUTH AND JAWS.

II EXTRAORAL DISEASES DISEASES OF THE MOUTH AND JAWS

Diseases of the teeth and supporting structures

• Pulpitis
• Periapical
• Periodontitis
• Periodontal Abscess
• Periapical Abscess
• Acute Ulcerative Gingivitis
• Pericoronitis
• Dento Alveolar Fractures.

Diseases of the Oral Mucosa

• Apthous Ulcerations
• Erosive Lichen Planus
• Herpetic Infections
• Atrophic Glossitis
• Neoplasm
• Pain In the Edentulous Patient
• Mucosal ulcerations from Denture
• Trauma
• Incorrect Vertical Dimension
• Pressure on the Mental nerve Pressure on the Genial tubercles
• Infected Residual Cysts
• Retained Root Stumps
• Diseases of the Jaws
• Fractures
• Osteomyelitis
• Osteoradionecrosis
• Infected Cysts
• Malignant Neoplasms – Sarcomas, SCC etc.
• Post Operative Pain
• Alveolar Osteitis (Dry Socket)
• Fractures
• Nerve Injury
• Tissue Space Infection
•  Hematoma
• Muscle Spasm
• Masticatory Pain
• MPDS
• TMJ Pathology
• Temporal arteritis

EXTRA ORAL DISEASES

Diseases of the Maxillary Antrum Sinusitis – acute and Chronic

Malignant Neoplasms

Diseases of the Salivary Glands

Acute Parotitis Sailadenitis and Sailolithiasis

Malignant Neoplasm

Infected Mucoceles and Ranulas

Vascular Pain

 Migraine Migranous Neuralgia (Cluster Headache)

 ASSESSMENT OF PAIN

Measurement of pain is important, but unfortunately, pain cannot be measured objectively because it is subjective experience. Though pain cannot be measured directly, several methods have been developed that allow patients to communicate more meaningfully about their pain such as: Unidimensional tools: Visual analog & Category and numeric rating scales Multidimensional tools: McGill pain Questionnaire

DIAGNOSTIC NERVE BLOCKS

Whether a painful structure is site or source of pain Various diagnostic nerve blocks are:

• Dental blocks
• Auricotemporal nerve block
• Infraorbital nerve block
• Stellate ganglion nerve block