TMD—temporomandibular disorders—affects an estimated 10-15% of adults, making it one of the most common chronic pain conditions. Yet it remains widely misunderstood, often dismissed, and frequently mistreated.

First, a clarification that causes endless confusion: TMJ is the joint; TMD is the disorder. Everyone has two TMJs (temporomandibular joints). TMD refers to problems affecting these joints and the associated muscles. Using "TMJ" as shorthand for the disorder is technically incorrect, though so common that even some clinicians do it.

What causes TMD?

The honest answer: we don't fully understand it. TMD is now recognised as a multifactorial condition—meaning physical, psychological, and lifestyle factors all play a role (List & Jensen, 2017).

Contributing factors include:

• Muscle overuse and tension: Repeated clenching or grinding can fatigue and strain the masticatory muscles
• Disc displacement: The cartilage disc between the ball and socket can shift out of position
• Arthritis: Degenerative or inflammatory joint conditions
• Trauma: Direct injury to the jaw or whiplash
• Stress and psychological factors: Anxiety, depression, and catastrophising are associated with TMD pain
• Central sensitisation: The nervous system can become hypersensitive, amplifying pain signals

The bruxism-TMD relationship

This is where it gets complicated. Many assume bruxism causes TMD, but the research is more nuanced—and has significant gaps.

The overlap is substantial: Studies suggest that up to 87% of TMD patients also have bruxism. Yet the current scientific consensus is that bruxism may contribute to TMD symptoms rather than directly causing them. Not everyone with bruxism develops TMD, and not everyone with TMD is a bruxer.

A counterintuitive finding: Two systematic reviews by Manfredini & Lobbezoo (2010, 2021) found that when sleep bruxism is measured objectively using EMG or polysomnography, there is lower or even negative association with TMD pain. At first glance this seems to disprove a causal link—but there's a simpler explanation: when your jaw hurts intensely, grinding becomes self-limiting. It hurts too much to clench. This suggests a potential feedback loop that cross-sectional studies (which only capture a snapshot in time) cannot detect.

The research gap: Most bruxism-TMD studies are cross-sectional, not longitudinal. They measure both conditions at one point in time and ask "are they correlated?" But they can't capture whether bruxism preceded TMD, or whether severe TMD pain reduced grinding behaviour over time. We need long-term studies tracking people before and after they develop symptoms to truly understand causation.

The appropriate language for now: bruxism "may contribute to" or "can aggravate" TMD symptoms—not "causes TMD." But the absence of proof is not proof of absence, and the research methodology has significant limitations.

Common symptoms

TMD can present in many ways, which is part of why it's often misdiagnosed:

Primary symptoms:

• Jaw pain or tenderness (especially when chewing)
• Pain in or around the ear
• Facial pain or aching
• Clicking, popping, or grating sounds in the joint
• Difficulty or discomfort when opening the mouth wide
• Jaw locking (open or closed)

Associated symptoms:

• Headaches (particularly tension-type, in the temple region)
• Neck and shoulder pain
• Ear symptoms (fullness, tinnitus) without infection
• Tooth pain that doesn't have a dental cause

The Diagnostic Criteria for TMD (DC/TMD) provides standardised assessment tools used in research and increasingly in clinical practice (Schiffman et al., 2014).

Current treatment landscape

Here's where the frustrating reality of TMD care becomes apparent. Despite its prevalence, treatment remains fragmented and often based more on tradition than evidence.

Conservative approaches (first-line)

Evidence supports starting with reversible, non-invasive treatments:

• Self-management education: Understanding the condition often reduces catastrophising and improves outcomes
• Jaw exercises: Research-backed exercises—including progressive jaw mobility techniques and isometric resistance exercises validated in clinical trials—can improve range of motion and reduce pain. Apps like JawSense include these exercises with video guidance.
• Physical therapy: Manual therapy, posture training, and targeted exercises
• Heat/cold application: Simple but often effective for acute flares
• Soft diet during flares: Reduces mechanical loading on the joint

Splints and night guards

Occlusal splints remain standard of care, though with important caveats:

• They protect teeth from grinding damage
• They may redistribute forces on the joint
• They do not cure TMD or stop bruxism
• Some patients don't tolerate them or find no benefit

Medications

Various medications are used, typically for short-term symptom management:

• NSAIDs for inflammation and pain
• Muscle relaxants for acute muscle spasm
• Tricyclic antidepressants at low doses for chronic pain
• Botulinum toxin injections in severe cases (reduces muscle force but not grinding frequency)

What about surgery?

Surgery is rarely indicated and should be considered only after conservative approaches have failed for an extended period. Less invasive procedures (arthrocentesis, arthroscopy) may be appropriate for specific joint pathology. Open joint surgery is uncommon.

The OPPERA studies—the largest longitudinal research on TMD—emphasise that TMD is primarily a pain condition rather than a structural problem requiring surgical correction (Slade et al., 2016).

The gap in current care

Here's what's frustrating about TMD treatment:

Fragmented care. Patients bounce between dentists, doctors, physiotherapists, and specialists with no coordinated approach.

Overemphasis on occlusion. Despite weak evidence, some practitioners still focus heavily on bite adjustments that may be unnecessary or even harmful.

Underemphasis on the whole picture. Stress, sleep, psychological wellbeing, and how your nervous system processes pain are often overlooked.

Limited monitoring. There's no standard way to track symptoms, identify patterns, or measure progress over time.

No accessible biofeedback. While research shows biofeedback can help both bruxism and TMD-related muscle tension, devices are essentially unavailable on the consumer market.

The bottom line

TMD is a complex, multifactorial condition that requires a comprehensive approach:

1. Conservative first: Start with self-management, exercises, and education
2. Address contributing factors: Including stress, sleep, and any bruxism
3. Track patterns: Symptoms fluctuate; understanding triggers helps management
4. Avoid irreversible treatments early: Surgery and occlusal adjustments should not be first-line
5. Seek coordinated care: Ideally from practitioners who understand that TMD involves physical, psychological, and lifestyle factors

The science of TMD has advanced significantly. The challenge is translating that knowledge into accessible, integrated care.