L27 Defining Orofacial Pain

Defining Orofacial Pain

Ramesh Balasubramaniam OAM

DENT5310
Orofacial Pain and Dental Sleep Medicine Module
16th April 2026

Affiliations and Organizations¹

• The University of Western Australia
• Perth Oral Medicine & Dental Sleep Centre
• Perth Children’s Hospital
• Periogold®
• Oral Medicine Academy of Australasia
• DSSWA
• Australian Dental Association
• Australasian Sleep Association

Course Overview and Learning Outcomes

Presenter Information²

Ramesh Balasubramaniam OAM
Associate Professor, Oral Medicine
UWA Dental School
The University of Western Australia

Conflict of Interest Disclosure

Neither I nor my immediate family have any financial interests that would create a conflict of interest or restrict my independent judgment with regard to the content of this presentation.

Specific Learning Outcomes

Unit Learning Outcome 26³

Explain the common causes and mechanisms of orofacial pain.

Scope of Learning

The learning outcomes are visible across the entire unit. The series of lectures over the next four weeks will focus on outcomes relevant to facial pain and TMD.

• Pain Mechanisms: Ability to define, classify, and differentiate between various mechanisms of pain including orofacial pain.
• Pain Presentations: Distinguish various pain presentations including acute vs chronic pain; physiological vs pathophysiological pain and understand how the biopsychosocial model contributes to the experience and perception of orofacial pain.
• Temporomandibular Disorders (TMD): Define, classify and discuss the aetiological factors of TMD and understand the anatomy and function of the temporomandibular joint (TMJ) and masticatory muscles.
• Clinical Assessment: Learn to perform a comprehensive history for orofacial pain patients including the effective use of examination tools for TMD assessment and apply diagnostic criteria for TMD.

Clinical Conditions and Management⁴

• Intracapsular Disorders: Understand common intracapsular disorders with regards to aetiology, pathophysiology, diagnosis, clinical features and management including subluxation and luxation of the TMJs.
• Extracapsular Disorders: Understand common extracapsular disorders with regards to aetiology, pathophysiology, diagnosis, clinical features and management.
• Splint Therapy: Outline the rationale for splint therapy including mechanisms of action, various types of splint designs, indications, and the evidence supporting their use in managing temporomandibular disorders and bruxism.
• Neuromodulators: Discuss the indications, mechanism of action, contraindications, side effects, and complications of neuromodulators.
• Neuropathic Pain: Outline the aetiology, pathogenesis, clinical features, diagnosis and management of neuropathic orofacial pain conditions.

Specialized Topics⁵

• Non-Odontogenic Toothache: Describe prevalence, aetiology, pathophysiology, clinical features, diagnosis and management of various conditions that may present as non-odontogenic toothache.
• Bruxism: Describe evolution, epidemiology, risk factors, aetiology and pathophysiology, clinical features, diagnosis and management of bruxism.
• Sleep Medicine: Understand the relationship between sleep and overall health, identify risk factors for sleep-disordered breathing, recognise tools for evaluating sleep disorders, and understand available treatment options, including effective management with oral appliance therapy.

The Definition of Pain⁶

Presentation Agenda⁷

• Pain Definition

• Is Pain Good or Bad?

• 3 Pains

• Biopsychosocial Model for Pain

• Definition & Classification of Orofacial Pain

• Take Home Message

• Pain Definition

• Is Pain Good or Bad?

• 3 Pains

• Biopsychosocial Model for Pain

• Definition & Classification of Orofacial Pain

• Take Home Message

Evolution of the IASP Definition⁸

NEW DEFINITION OF PAIN

Historical Context and Revision⁹

The currently accepted definition of pain was originally adopted in 1979 by the International Association for the Study of Pain (IASP). In 2018, IASP constituted a 14-member multi-national task force with expertise in clinical and basic science related to pain, which sought input from multiple stakeholders to determine if progress in the knowledge of pain warranted a re-evaluation.

Comparison of Definitions

• 1979 Definition of Pain: An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.
• 2020 Revised Definition of Pain: An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage.

2020 Revised Definition Notes

• Pain is always a personal experience that is influenced to varying degrees by biological, psychological, and social factors.

The Mind-Body Connection

Pain is a marriage between the physical body and the mind. Psychological inputs, context, emotion, and expectations significantly influence the pain experience.

• Pain and nociception are different phenomena. Pain cannot be inferred solely from activity in sensory neurons.
  • Nociception is the sensory input, while pain is the emotional response and experience.
• Through their life experiences, individuals learn the concept of pain.
• A person’s report of an experience as pain should be respected.
• Although pain usually serves an adaptive role, it may have adverse effects on function and social and psychological well-being.
• Verbal description is only one of several behaviors to express pain; inability to communicate does not negate the possibility that a human or a nonhuman animal experiences pain.

The 2020 IASP Definition¹⁰

“An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage.”

Source: Raja SN et al. The revised International Association for the Study of Pain definition of pain: concepts, challenges, and compromises. Pain. 2020.

Key Concepts and Clinical Notes

Biological and Psychological Factors¹¹

• Pain is always a personal experience that is influenced to varying degrees by biological, psychological, and social factors.
• Pain and nociception are different phenomena. Pain cannot be inferred solely from activity in sensory neurons.

Source: Raja SN et al. (2020).

Learning and Respecting the Pain Experience¹²

• Through their life experiences, individuals learn the concept of pain.
• A person’s report of an experience as pain should be respected.
  • Because pain is a personal reality, clinicians should focus on the individual rather than just the number on a pain scale. A patient's "10 out of 10" is their reality regardless of the physical stimulus.

Source: Raja SN et al. (2020).

Adaptation and Communication¹³

• Although pain usually serves an adaptive role, it may have adverse effects on function and social and psychological well-being.
• Verbal description is only one of several behaviours to express pain; inability to communicate does not negate the possibility that a human or a non-human animal experiences pain.

Source: Raja SN et al. (2020).

Pain Characteristics and Mechanisms

Presentation Overview¹⁴

• Pain Definition
• Is Pain Good or Bad?
• 3 Pains
• Biopsychosocial Model for Pain
• Definition & Classification of Orofacial Pain
• Take Home Message

The Dual Nature of Pain¹⁵

• No one wants to be in pain
• Important for health & survival

Physiological vs Pathophysiological Pain

Physiological Pain Characteristics¹⁶

• Consequence of tissue injury or noxious stimuli
• Site of injury = source of pain
• “Normal Pain” / protective
• When noxious stimuli is removed, inflammation resolves and pain ceases
• Helps the body heal by encouraging protection of the area.

Pathophysiological Pain Characteristics¹⁷

• Pain persists after noxious stimuli has ceased and tissue healed
• Lesion / dysfunction of the PNS or CNS
• Chronic pain
• Serves no protective or reparative role.

Biomedical vs Biopsychosocial Perspectives

Comparative Perspectives¹⁸

Biomedical Pain

• Pain is primarily a sensory experience signaling tissue damage.
• Somatosensory cortex of brain perceives the pain.
• Pain = tissue damage / stimuli
• The traditional model suggests a direct correlation between the size of the injury and the amount of pain. If no tissue damage is visible, the pain is often dismissed.

Biopsychosocial Pain

• Biological, psychological, social and cultural.
• Mind – body connection.
• Interaction of the higher centres accounts for psychological aspects.
• Influenced by genetics, conditioning, context, emotion, mood, expectation of pain.

Individual Experience of Pain¹⁹

Pain is an individual experience shaped by several factors:

• In spite of same noxious stimuli, the experience varies.
• Subjective intensity: “My 10 is not the same as your 10.”
• Particularly influenced by childhood experiences.

Clinical Insight

Sir William Osler: “It is more important to know what type of individual has the pain rather the type of pain the patient has.”

Sensory and Affective Components of Suffering

Components of the Pain Experience²⁰

Sensory-Discriminative

• Localization, intensity discrimination, and quality of noxious stimulus.
• Deals with the location, intensity (e.g., 8/10), quality (e.g., aching), and duration of the pain.

Motivational-Affective

• Emotion, arousal, and pain behavior.
• How the individual reacts.
• Influenced by prior experience, expectations, and possible misconceptions.
• Deals with the emotional response, including anxiety, depression, guilt, and catastrophizing.

The Three Types of Pain

Presentation Agenda²¹

• Pain Definition
• Is Pain Good or Bad?
• 3 Pains
• Biopsychosocial Model for Pain
• Definition & Classification of Orofacial Pain
• Take Home Message

Nociceptive Pain

Clinical Manifestations in Dentistry²²

Nociceptive pain in the context of toothache presents through various stages of health and disease:

• Pulpitis is classified as a form of visceral pain.

• Ligament-related pains are also common clinical manifestations.

• Healthy tooth: In health, allodynia is felt to cold, electrical, and mechanical stimuli.

• Insult to tooth/Trauma:

  • Cracked tooth syndrome: Intermittent neuralgic pain on biting with no other symptoms.

• Caries:

  • Pulpal Inflammation: Causes sensitivity of A delta fibers; allodynic pain with cold and sugary stimuli.
  • Hyperaemia of the pulp.

• Pulpal ischaemia: Causes sensitivity of C fibers and allodynia to heat; spontaneous episodic throbbing pain.

• Pulpal necrosis: Pulpal death causes periapical tissue inflammation. Results in episodic spontaneous throbbing pain and allodynia on biting.

Definition

Nociceptive Pain is pain that arises from actual or threatened damage to non-neural tissue and is due to the activation of nociceptors. It involves a normally functioning somatosensory nervous system.

Mechanism and Function²³

• Stimuli: Noxious stimuli may be mechanical, thermal, or chemical, resulting in damage or potential damage.
• Processing: Nociception is modified on the way to the CNS; it can be amplified, reduced, or inhibited.
• Perception: It is only classified as pain when it reaches the Central Nervous System (CNS).
• Purpose: The primary function is to prevent further injury.

Neuropathic Pain

Definition²⁴

Neuropathic Pain is pain caused by a lesion or disease of the somatosensory nervous system.

Characteristics of Neuropathic Pain²⁵

• Systemic Origin: Arises from an abnormality of the nervous system.
• Stimulus Independence: There is no need for noxious stimuli.
• Presentation: Pain may be spontaneous.
• Function: It serves no protective role.
• Classification: Can be categorized as Episodic vs. Continuous Neuropathic Pain.
  • Pain is often described as electric shock-like in nature.
  • Specific examples include post-traumatic trigeminal neuropathic pain.

Nociplastic Pain

Definition²⁶

Nociplastic Pain is pain that arises from altered nociception despite no clear evidence of actual or threatened tissue damage causing the activation of peripheral nociceptors or evidence for disease or lesion of the somatosensory system causing the pain.

Pathophysiology

• Characterized by maladaptive plasticity.
  • Involves altered connectivity within the central nervous system.

Clinical Nature of Nociplastic Pain²⁷

• Evidence: Pain occurs without evidence of tissue damage or a clear physiological cause.
• Validity: The pain is “real” and has a neurophysiological basis.
• Contributing Factors: May be influenced by psychological stress.
  • The pain is often triggered or maintained by emotional distress rather than physical injury.

Comparative Analysis of Pain Types

Comparison Table of Pain Types²⁸

Feature	Nociceptive / Inflammatory	Neuropathic	Nociplastic / Central Sensitisation
Stimulus	Injury or Inflammation (tissue injury)	Neural damage, pinching, irritation (nerve injury)	Central nervous system dysfunction (sensitised nervous system)
Neuron	Nociceptor and non-nociceptor	Nociceptor and non-nociceptor	Non-nociceptor
Site	Peripheral and central nervous system	Peripheral and central nervous system	Central nervous system
Clinical / Dentistry	Pulpitis, jaw fracture, acute periodontitis	Trigeminal neuralgia, anaesthesia dolorosa, post-herpetic neuralgia	Burning mouth syndrome, persistent facial pain, persistent dentoalveolar pain
Function	Protective, healing / repair, pathological	Pathological	Pathological
Pain Sensitivity	High or low threshold	Low threshold	Low threshold

The Biopsychosocial Model of Pain

Presentation Overview²⁹

• Pain Definition
• Is Pain Good or Bad?
• 3 Pains
• Biopsychosocial Model for Pain
• Definition & Classification of Orofacial Pain
• Take Home Message

Acute vs Chronic Pain Paradigms

Characteristics of Chronic Pain³⁰

• Chronic pain is defined as pain persisting beyond normal healing time.
• In chronic pain, the physical input is often small, while the psychosocial input is massive.
• Neuroplasticity may prolong and maintain the pain state.

Chronic vs. Recurrent Pain Disorders

• Behavioral and psychological changes begin to manifest in chronic and recurrent states.

Axis I and Axis II Inputs³¹

Model Components³²

• Axis I: Somatosensory Input (Green)
• Axis II: Psychosocial Input (Brown)

Outcomes of Combined Influences

• Combined inputs lead to Suffering and Pain Behavior.

Temporal Progression

• The model tracks the transition over time from Acute pain to **Chronic pain
• In acute pain, the somatosensory input is high. As pain becomes chronic, the psychosocial factors become the dominant drivers of suffering and behavior.**.

Economic Impact³³

• 1 in 15 Australians live with chronic pain.
• Estimated cost: $22,588-$44,979 per year.

Acute Pain Characteristics

• An unpleasant, dynamic psychophysiological process.
• Occurs in response to tissue trauma and related inflammatory processes.
• Provides survival value and plays a role in healing.

Chronic Pain Characteristics

• Maladaptive with little evolutionary benefit.
• Requires a shift in mindset from eradicating the problem to management.
• Focuses on functional and emotional resilience.

Longitudinal vs. Cross-Sectional Perspectives³⁴

Pain assessment involves viewing the condition as a “motion picture” (longitudinal) rather than just a “snapshot” (cross-sectional), considering socioeconomic and healthcare contexts.

• A longitudinal view reveals that factors like generational trauma, childhood experiences, and lifestyle influence the pain experience long before the patient seeks treatment.

Influencing Factors Across the Lifespan

• Premorbid Characteristics and Demographics:
  • Genes
  • Lifestyle
  • Learning history
  • Culture
• Clinical Factors:
  • Age at symptom onset and consult age
  • Pathology and changes in pathology
  • Treatments
• Psychological and Behavioral Factors:
  • Beliefs and expectancies
  • Behavior and consequences
• Resources:
  • Interpersonal support
  • Economic resources

Neurobiological Basis for Facial Pain

Amygdala Activation³⁵

fMRI studies show higher amygdala activation for facial pain compared to hand pain, even when the pain intensity is rated the same.

Neural Circuitry

• The Lateral parabrachial nucleus (PBL) is activated more strongly by noxious facial stimulation.
• A specific craniofacial monosynaptic connection exists between cranial sensory neurons and PBL-nociceptive neurons, enabling heightened affective pain.
• Unlike other body parts, the face does not habituate well to repeated painful stimuli (e.g., repeated slaps feel equally intense).

Clinical Case Application

Case Presentation³⁶

• Patient: 33-year-old female.
• Chief Complaint: Temporomandibular joint (TMJ) clicking and pain.

Psychological and Social Factors³⁷

• Empathy and Social Bonding
• Isolation Induced Suffering
• Depression and Anxiety
• Somatisation

Clinical and Physical Factors

• Mechanisms and Mediators
• Clinical Pain, Clicking, and Locking
• Occlusion and Asymmetries

Case Study: 33-year-old Female

• Physical Symptoms: TMD clicking and pain diagnosed as disk displacement with reduction.
• Psychosocial Context: The patient is extremely embarrassed by the clicking. She recently broke up with a partner and believes a second date failed because of her "clicky jaw" during dinner.
• Clinical Insight: The primary issue is her anxiety and catastrophizing regarding her social life and relationships rather than the physical displacement.

Classification of Orofacial Pain

Presentation Agenda³⁸

• Pain Definition
• Is Pain Good or Bad?
• 3 Pains
• Biopsychosocial Model for Pain
• Definition & Classification of Orofacial Pain
• Take Home Message

Definitions and Prevalence

Orofacial Pain³⁹

• Definition: Orofacial pain is pain perceived in the face and/or oral cavity.
• Prevalence: 17-26%
• Source: Porporatti AL et al. J Oral Facial Pain Headache. 2024 Sep;38(3):1-14.

Temporomandibular Disorders (TMD)

• Definition: A diverse group of musculoskeletal and neuromuscular conditions involving the TMJs, masticatory muscles, and associated structures.
• Prevalence: 4.6% (Isong et al. 2008)
• Source: Klasser & Romero Reyes (2023) Orofacial Pain: Guidelines for Assessment, Diagnosis, and Management 6th Ed. Quintessence Publishing

Diagnostic Framework and TMD Criteria⁴⁰

Diagnostic Axis Framework⁴¹

Axis I (Physical Conditions) + Axis II (Psychological Conditions) → Diagnosis

Axis I: Physical Conditions

• Somatic Pain
  • Superficial Pain
    • Cutaneous Pain
    • Mucogingival Pain
  • Deep Pain
    • Musculoskeletal Pain
      • Muscle Pain (Myospasm, Myofascial Pain, Central Mediated Myalgia, Myofascial Pain Syndrome)
• Neuropathic Pain
  • Peripheral Mediated Pain
    • Metabolic Polyneuropathies
    • Entrapment Neuropathy
    • Deafferentation Pain
    • Neuritic Pain (e.g., Burning Mouth Disorder, Atypical Odontalgia)
    • Trigeminal Neuralgia
  • Other Primary Headache
    • Cluster and other Trigeminal Autonomic Cephalalgias (TCA)
• Visceral Pain
  • Musculoskeletal Pain
  • Visceral Mucosal Pain
  • Glandular, ENT Pain
  • Pulpal Pain
  • Vascular Pain
  • Neurovascular Pain
  • Capsular Pain
  • Arthritic Pain
  • Retrodiscal Pain
  • Ligamentous Pain
• Central Mediated Pain
  • Peripheral Neuritis
  • Herpes Zoster
  • Post Herpetic Neuralgia
  • Complex Regional Pain Syndrome
  • Sympathetically Maintained Pain

Axis II: Psychological Conditions

• Mood Disorders
  • Mood Disorder due to a Medical Condition
  • Bipolar Disorder
  • Depressive Disorder
• Anxiety Disorders
  • Anxiety Disorder due to a Medical Condition
  • Posttraumatic Stress Disorder
  • Generalized Anxiety Disorder
• Somatoform Disorders
  • Conversion Disorder
  • Pain Disorder, Undifferentiated
• Stress-Related Physiological Response
• Personality Traits or Coping Style
• Other Conditions
  • Psychological Factors Affecting Medical Condition
  • Malingering
  • Hypochondriasis

Diagnostic Criteria for TMD (DC/TMD)⁴²

TMD Diagnosis	Sensitivity	Specificity
Pain-Related TMD
A. Myalgia	0.90	0.99
1. Local myalgia	Not established	Not established
2. Myofascial pain	Not established	Not established
3. Myofascial pain with referral	0.86	0.98
B. Arthralgia	0.89	0.98
C. Headache attributed to TMD	0.89	0.87
Intra-articular TMD
A. Disc displacement with reduction	0.34	0.92
B. Disc displacement with reduction with intermittent locking	0.38	0.98
C. Disc displacement without reduction with limited opening	0.80	0.97
D. Disc displacement without reduction without limited opening	0.54	0.97
E. Degenerative joint disease	0.55	0.61
F. Subluxation	0.98	1.00

*Source: Schiffman et al. J Oral Facial Pain Headache 2014;28:6–27.

International Classification Standards

• The International Classification of Orofacial Pain (ICOP) serves as the primary international classification system for these conditions.
• There is no established relationship between occlusion (the bite) and orofacial pain.*

Conclusion and Summary⁴³⁴⁴

Presentation Overview⁴⁵

• Pain Definition
• Is Pain Good or Bad?
• 3 Pains
• Biopsychosocial Model for Pain
• Definition & Classification of Orofacial Pain
• Take Home Message

Key Takeaways⁴⁶

• There is a new definition of pain.
  • Understand the 2020 IASP definition of pain.
• Three types of pain are enveloped around the biopsychosocial model.
  • Recognize the three types of pain: Nociceptive, Neuropathic, and Nociplastic.
• Always conduct a psychosocial history with empathy.
• If you don’t believe the pain, believe the suffering.
  • If you cannot find a physical cause for the pain, believe the patient's suffering.
• Orofacial pain… never a boring day.

THANK YOU!!!

Ramesh Balasubramaniam OAM

DENT5310 Orofacial Pain and Dental Sleep Medicine Module 16th April 2026

Footnotes

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