LLLT series (Part 2): How Does Low-Level Laser Therapy Work?

Low-Level Laser Therapy (LLLT), also called photobiomodulation therapy (PBM), uses red and near-infrared light to influence cellular activity without cutting or heating tissue.

Its effects are thought to involve changes in mitochondrial function, cellular signaling, inflammation, circulation, tissue repair, and pain processing.

Light Reaches the Cells

PBM typically uses wavelengths in the red and near-infrared spectrum. These wavelengths can penetrate soft tissues and interact with light-sensitive molecules inside cells.

One of the most studied cellular targets is cytochrome c oxidase, an enzyme within mitochondria. Mitochondria produce ATP, the energy used by cells to carry out normal functions and repair processes.

The simplified sequence is:

Light → mitochondrial signaling → changes in cellular activity

Mitochondrial Activity and ATP

Photobiomodulation may alter the mitochondrial respiratory chain and increase ATP production under certain conditions.

This does not mean the laser simply “adds energy” to tissue. Rather, light acts as a biological signal that may influence how cells regulate metabolism and respond to stress or injury.

PBM may also affect nitric oxide, reactive oxygen species, and intracellular calcium, all of which participate in cellular signaling.

These early changes can influence gene expression, inflammatory pathways, tissue repair, and cellular survival.

Illustration of the Mechanism of Action for Low-Level Laser Therapy (LLLT), detailing its multi-step process from light delivery to clinical outcomes. The infographic highlights how LLLT uses red and near-infrared light to penetrate soft tissue, targeting mitochondria, enhancing cellular activity, modulating inflammation, and reducing pain, ultimately leading to improved healing and function. Key principles include the biphasic dose response for optimal benefits.

How Can LLLT Reduce Inflammation?

One of the most studied effects of photobiomodulation is modulation of inflammation.

Research suggests PBM may influence inflammatory mediators, immune-cell activity, oxidative stress, and signaling pathways involved in tissue injury.

This may help explain its use in conditions involving painful joints, muscles, and postoperative inflammation.

It is more accurate to say that PBM may modulate inflammation rather than simply “turn inflammation off.”

How Can LLLT Reduce Pain?

Pain relief may occur through several mechanisms.

First, reducing inflammatory signaling may decrease stimulation of local pain receptors.

Second, PBM may directly affect peripheral nerves. Studies suggest that certain light exposures can influence nerve excitability and nociceptive signaling.

This is one reason photobiomodulation is being investigated for both musculoskeletal and selected neuropathic pain conditions.

Effects on Muscle

For painful muscles such as the masseter, temporalis, or cervical musculature, PBM may influence:

• mitochondrial metabolism

• inflammatory signaling

• local circulation

• oxidative stress

• muscle recovery

  
  

This provides a biological rationale for its use in masticatory myalgia and other myofascial pain conditions.

Effects on Nerves

Photobiomodulation may also affect peripheral nerve function.

Research has reported changes in nerve excitability, axonal activity, neuroinflammation, and pain transmission. These effects are particularly relevant to ongoing research into burning mouth syndrome, trigeminal neuralgia, and other nerve-related facial pain disorders.

Why Might LLLT Help Tissue Healing?

The same signaling pathways that affect pain and inflammation can also influence tissue repair.

PBM has been associated with changes in:

• fibroblast activity

• collagen production

• cell migration

• microcirculation

• cellular repair processes

This is why photobiomodulation has also been studied in wound healing and postoperative recovery.

More Is Not Always Better

One of the most important concepts in PBM research is the biphasic dose response. Too little light may produce little effect, while increasing the dose beyond an optimal range does not necessarily improve the response and may reduce it.

So photobiomodulation is not simply a matter of using more power or more treatment time.

The biological response depends on wavelength, power, treatment area, tissue depth, duration, and the condition being treated.

What Does This Mean for Orofacial Pain?

The same biological principles can be relevant to several different conditions:

Condition	Potential PBM effect
TMJ pain	Modulation of inflammation and pain signaling
Jaw muscle pain	Effects on muscle metabolism and nociception
Burning Mouth Syndrome	Modulation of abnormal sensory signaling
Selected nerve-related facial pain	Effects on peripheral nerve activity and neuroinflammation
Post-procedure discomfort	Modulation of inflammation and tissue recovery
Neck-related facial pain	Reduction of musculoskeletal pain input

The important point is that LLLT is not treating all of these conditions in exactly the same way.

The target tissue and underlying pain mechanism matter.

The Bottom Line

Low-Level Laser Therapy works through photobiomodulation rather than heat or tissue destruction.

Current research suggests that red and near-infrared light can influence mitochondrial activity, ATP production, nitric oxide, reactive oxygen species, calcium signaling, inflammation, and peripheral nerve activity.

For orofacial pain, this is what makes PBM versatile: the same technology may be applied to a joint, muscle, nerve, or oral tissue, depending on the diagnosis.

The key is not simply where the pain is felt.

It is understanding what tissue and pain mechanism are actually responsible for it.

Call us at 206 880 0119 to see if you would benefit from LLLT.