In-Office Photobiomodulation Therapy to Enhance Clinical Treatment

Photobiomodulation (PBM) therapy using light energy has been reported to provide positive effects in various areas of the body without any side effects when applied to the tissues in a noninvasive manner. It can be accomplished with a number of standalone PBM therapy devices and dental lasers that offer PBM attachments (eg, ATP38^® Miracle, Integrated Dental Systems; Gemini^™, Ultradent; Epic X^™, Biolase). Although red light and near-infrared (NIR) light are the most commonly used and understood, various wavelengths exist that can be utilized alone or in combination to reduce pain and inflammation and improve healing following extraction and periodontal procedures, accelerate aligner therapy, and facilitate a number of other esthetic applications, including reducing dermal scarring, improving skin tone, and even reversing the effects of hair loss.

Understanding the differences and capabilities of the different wavelengths available is important when treating patients with PBM therapy. The classifications of blue, green, yellow, red, and NIR light span a wide spectrum of wavelengths that achieve varying levels of tissue penetration and, subsequently, produce different effects on tissues.

PBM therapy is defined as the utilization of non-ionizing electromagnetic radiation to trigger photochemical changes within cellular structures that are receptive to those photons. Mitochondria, which produce energy called adenosine triphosphate (ATP) for cellular use, are particularly receptive to this process. At the cellular level, energy from NIR and visible red light is absorbed by the mitochondria, increasing the production of ATP along with mild reactive oxygen species, nitric oxide, and cyclic adenosine monophosphate (cAMP), which can initiate cell proliferation and induce the signal cascade effect.¹ The production of reactive oxygen species also leads to cellular repair and healing. This process unclogs the chain that has been clogged by nitric oxide, which is then released back into the system.² Nitric oxide is a molecule that our bodies produce to help cells communicate with each other by transmitting signals.³ In addition, nitric oxide helps to dilate the blood vessels and improve blood circulation. All of these factors can lead to increased expression of genes related to protein synthesis, cell migration and proliferation, anti-inflammatory signaling, and production of anti-apoptotic proteins and antioxidant enzymes. Stem cells and progenitor cells appear to be particularly susceptible to PBM therapy.⁴ The key to the entire process is a mitochondrial enzyme called cytochrome c oxidase, which is a chromophore that accepts photonic energy of specific wavelengths when functioning below par. As the mitochondria absorb those wavelengths of light energy and produce more ATP energy, transportation in the cells is boosted, and the resulting cell proliferation improves the body's natural healing process.

Light energy is measured in nanometers (nm) and expressed in ranges called wavelengths. Natural or white light is a combination of various wavelengths in the visible spectrum. The different wavelengths of light are able to penetrate the body's tissues to varying degrees, producing various effects upon exposure, and fall into color-specific ranges. As the wavelength increases, deeper penetration and different effects are observed, with the ultraviolet wavelength demonstrating the least penetration and the NIR wavelength demonstrating the deepest. Light in the ultraviolet wavelength, which is typically between 100 nm and 380 nm, causes the skin to tan and can result in sunburn. Exposure to ultraviolet light has little to no effect on the deeper tissues, but its effects on the superficial skin may result in the development of skin cancer for some individuals.⁵

Blue Light

The wavelength of blue light falls between 450 nm and 470 nm. Clinical results of the use of blue light include reported benefits for patients with inflammatory acne lesions; however, this wavelength of light is capable of inducing both beneficial and adverse effects, depending on the dose and the spectrum width of the exposure.⁶ Controversy exists surrounding the use of blue light because the margin between "safe" blue light and potentially damaging ultraviolet light has not been well defined.

Research has demonstrated that blue light can aid in the prevention of skin flap necrosis and, when combined with red light, can enhance the survival of skin flaps by improving angiogenesis.⁷ Therefore, the inclusion of blue light in PBM therapy can augment the effects of red light to aid in the healing of incisions, cuts, and other alterations to the surface tissues (eg, skin and gingiva). Blue light has also been reported to stimulate keratinocyte differentiation, which aids in restoring the skin's barrier function.⁸

Green Light

Green light has a wavelength of 510 nm to 540 nm, and when it is absorbed into the skin, it can help to lighten areas of hyperpigmentation, revealing a brighter complexion. Although pigmented areas of the skin, such as freckles or birthmarks, are caused by a number of factors and can occur in all skin types, hyperpigmentation is characterized by darker areas of the skin or gingiva related to the overproduction of melanin. Light in the green wavelength targets melanocytes, the melanin-producing cells located in the deeper layer of the skin's epidermis, inhibiting the production of excess melanin and thereby preventing it from traveling to the skin's surface as well as breaking up melanin clusters to lessen existing discoloration. As a result, dark spots slightly fade and better blend with the surrounding tissue tone.⁹ In addition, green light aids in increasing the growth of cells, which contributes to healing of the skin and gingiva, and it has anti-inflammatory properties that soothe the surface of the skin. Green light has also been shown to have a therapeutic effect on basal cell carcinoma¹⁰ as well as to accelerate wound healing and have positive effects for the treatment of acne and other skin irritation issues.¹¹

When compared with clinically well-established red light therapy, green light has been reported to be more potent in stimulating the proliferation and migration of endothelial cells.¹² Furthermore, both the green and blue wavelengths have been reported to produce a stimulating effect regarding increased osteoblast differentiation. The shallower depth of penetration of these two wavelengths works well intraorally, where the osseous structure is below gingival tissue with no interspersed muscle that may prevent the light from reaching the boney area.

Yellow Light

Yellow light, which has a wavelength between 580 nm and 600 nm, achieves slightly deeper penetration than blue and green light, reaching the dermal area and producing healing, anti-inflammatory, analgesic, and regenerative effects. This wavelength can benefit patients with skin conditions involving redness and swelling as well as other issues related to pigmentation.¹³ In both in vitro and in vivo studies, yellow light therapy has been shown to trigger skin collagen synthesis and to reduce MMP expression.¹⁴ Skin rejuvenation effects have been reported as well.¹⁵ PBM therapy utilizing light in the yellow wavelength has been demonstrated to be effective in the treatment of acne¹⁶ and the reduction of dermal scars,¹⁷ including keloids.¹⁸ In addition, the yellow wavelength has been reported to be an effective treatment for thinning hair and baldness related to androgenetic alopecia and alopecia areata.¹⁹

Red Light

The wavelength of red light falls between 610 nm and 775 nm. Red light has been documented to improve healing by deeply penetrating into the skin and underlying structures where the irradiated cells can absorb and use it. According to the results of one study, PBM therapy using the red light wavelength resulted in a much lower amount of reactive oxygen species when the irradiated cells were compared with nonirradiated ones.²⁰ Research indicates that the more stressed the fibroblast cells are, the better they respond to PBM therapy using the red wavelength.²¹ Light in the red wavelength has been shown to increase cell proliferation and viability while aiding in wound healing by accelerating the rate of cell migration.²² It modulates dermal fibroblasts to increase the expression of genes responsible for enhancing the adaptive response to redox and inflammatory balance as well as genes that play a major part in DNA repair processes. In addition, red light irradiation can enhance the synthesis of procollagen, the expression of collagen, and the release of basic fibroblast growth factor.

NIR Light

The NIR light used in PBM therapy has a wavelength of 800 nm to 835 nm, and it affects two main chromophores: intracellular water and cytochrome c oxidase. In addition to photochemical effects, the use of NIR light also results in an increase in intracellular temperature. The biologic response of tissue to irradiation with NIR light is in part caused by this generated thermal effect. At the cellular level, NIR activates cytochrome c oxidase, the primary mitochondrial photoacceptor. This activation results in various cellular responses, including increased mitochondrial ATP production.²³ According to research, PBM therapy with NIR light has been demonstrated to increase mitochondrial metabolism,²⁴ stimulate angiogenesis of the skin and gingiva,²⁵ improve bone quality by stimulating osteoblastic cell activity,²⁶ and promote the regeneration of muscle tissues.²⁷ This elevation of metabolic activity and accompanying angiogenesis also increases the blood supply necessary for bone remodeling, which is accelerated by the increased levels of ATP.²⁸ In addition, wound healing is improved, so incisions created during periodontal and oral surgery or traumatic injuries heal at a faster rate.²⁹

Pain is a common occurrence following oral surgery as well as during orthodontic treatment when aligners are changed or a fixed appliance is adjusted. Because PBM therapy with NIR light has been shown to reduce pain, it should be a consideration for patients undergoing extractions, implant placement, periodontal procedures, orthodontic treatment, and other procedures.^30,31 A reduction in postoperative swelling has also been associated with PBM using NIR light, which further helps to reduce pain.³²

PBM therapy that combines different wavelengths of light energy can be beneficial as an adjunct in various dental procedures. Both red and NIR light have demonstrated an ability to accelerate orthodontic tooth movement by promoting alveolar bone remodeling on the compression side of the teeth. Although PBM therapy using energy in the red wavelength accelerated bone remodeling to a greater extent than NIR at an early stage, over time, use of the two wavelengths together provided better results than the use of either wavelength alone.³³ A simultaneous combination of blue, green, yellow, red, and NIR light can be used to treat a socket filled with platelet-rich fibrin following extraction (Figure 1 through Figure 4) or to help heal tissue after periodontal surgery (Figure 5 and Figure 6). For dentists who offer facial esthetic treatments, wrinkle reduction, skin tone improvement, acne and skin blemish treatment, scar reduction, hair regrowth, and more can all also be accomplished using combinations of different wavelengths.

Extensive research has demonstrated that PBM therapy boosts the body's responses, improving healing and regeneration of the soft and hard tissues. With applications including extraction socket preservation, periodontal surgeries, the acceleration of orthodontic treatment and implant osseointegration, and other esthetic procedures, dentists may want to consider offering PBM therapy as an adjunct to other treatments to improve clinical outcomes.

Ana Paz, DDS, MS
Head of Scientific Research and Development
White Clinic
Lisbon, Portugal

Miguel Stanley, DDS
Founder and Clinical Director
White Clinic
Lisbon, Portugal
Founder
Slow Dentistry Global Network

Gregori M. Kurtzman, DDS
Master
Academy of General Dentistry
Diplomate
International Congress of Oral Implantologists
Private Practice
Silver Spring, Maryland