**2. Action of LED Therapy in human tissues**

The photobiostimulation caused by irradiation with LEDs has a number of outcomes such as increasing cell proliferation rate, the production rate of fibroblasts and collagen synthesis. LED Therapy is known for its anti-inflammatory and healing properties and it can be used as an independent procedure of the conventional treatments of clinical medicine, but it should always be accompanied by a health professional with knowledge of the tissue pathology, cell rejuvenation and photobiostimulation cell. Different applications of LED Therapy may be performed as a function of wavelength (nm) of light penetration in tissue (mm). The relation‐ ship between these parameters demonstrates that the penetration depth of light into tissue, as shown in Figure 5.

#### **2.1. Light penetration in human tissues generated by the action of high brightness LEDs arrangements**

The processes of refraction and reflection of light emitted by LEDs in human tissues are responsible for the dispersion of light, as shown in Figure 5. However, the action of light is peculiar because the response to these processes can vary from person to person undergoing therapy.

Despite the high dispersion, the degree of penetration is significant, approximately 50% of the incident radiation to reach the substrate directly below the skin of the patient [4]. The fabric layers to be submitted to receive a red light portion scattered radiation given where a small tissue area can absorb light in the dermis and epidermis. This is due to the presence of photoreceptor layers that can be constituted of amino acids, melanin, and other acids. Typically each type of photoreceptor is sensitive to a particular wavelength.

Thus, light can be absorbed by the tissue which depends on the color and wavelength. For example, red light, near infrared, easily penetrates the fabric because this light radiation is not blocked by blood and water as other wavelengths.

Wavelengths less than 630nm, such as yellow, blue and green are significantly blocked by hemoglobin in the blood, so that they do not penetrate deeply [5].

Wavelengths greater than 900nm are blocked by the liquid portion of the skin and connective tissues. Many wavelengths can emit a large amount of energy above the infrared range and cannot be seen by the human eye; this type of radiation may produce a certain amount of heat to interact with human tissue [5].

#### **2.2. Action of light emitted by high-brightness LEDs in human tissue**

The blue is in the range of 430 to 485nm. The green is in the range of 510 to 565nm. The yellow is between 570 to 590nm. The red is in the range of 620nm to 700nm, to the point that it does not become visible anymore in the range of 740nm. Some companies that manufacture LEDs say that the yellow light helps remove wrinkles. There is also some interesting research, which emphasizes that the application of blue light helps in the elimination of a bacteria that causes some forms of acne [20].

The phototherapy with the narrow band blue light seems to be a safe treatment and one additional effective therapy for treatment of mild and moderate acnes. Some researchers suggest that the green LED light can help against cancer, but this color cannot penetrate more than the skin. Figures 1, 2, 3 and 4 show prototypes that emit light in the red, blue, green and amber colors.

#### *2.2.1. Action of red light emitted by high brightness LEDs*

in the treatment of rejuvenation and acne, hair loss, skin lesions, wound healing in postoperative incisions in the patient's psychological recovery, where the lights are applied to the environment and on other fronts of medicine. In dentistry the development of modern photopolymerizable materials represents a great advance for restorative dentistry because they allow excellent aesthetics, ease in handling and control of the clinical time [3, 23].

Advances in the medicine are encouraging and research in the area grows every day, the intent

The photobiostimulation caused by irradiation with LEDs has a number of outcomes such as increasing cell proliferation rate, the production rate of fibroblasts and collagen synthesis. LED Therapy is known for its anti-inflammatory and healing properties and it can be used as an independent procedure of the conventional treatments of clinical medicine, but it should always be accompanied by a health professional with knowledge of the tissue pathology, cell rejuvenation and photobiostimulation cell. Different applications of LED Therapy may be performed as a function of wavelength (nm) of light penetration in tissue (mm). The relation‐ ship between these parameters demonstrates that the penetration depth of light into tissue, as

**2.1. Light penetration in human tissues generated by the action of high brightness LEDs**

The processes of refraction and reflection of light emitted by LEDs in human tissues are responsible for the dispersion of light, as shown in Figure 5. However, the action of light is peculiar because the response to these processes can vary from person to person undergoing

Despite the high dispersion, the degree of penetration is significant, approximately 50% of the incident radiation to reach the substrate directly below the skin of the patient [4]. The fabric layers to be submitted to receive a red light portion scattered radiation given where a small tissue area can absorb light in the dermis and epidermis. This is due to the presence of photoreceptor layers that can be constituted of amino acids, melanin, and other acids. Typically

Thus, light can be absorbed by the tissue which depends on the color and wavelength. For example, red light, near infrared, easily penetrates the fabric because this light radiation is not

Wavelengths less than 630nm, such as yellow, blue and green are significantly blocked by

Wavelengths greater than 900nm are blocked by the liquid portion of the skin and connective tissues. Many wavelengths can emit a large amount of energy above the infrared range and

each type of photoreceptor is sensitive to a particular wavelength.

hemoglobin in the blood, so that they do not penetrate deeply [5].

blocked by blood and water as other wavelengths.

of this chapter is to present a study and results in healing and cell rejuvenation.

**2. Action of LED Therapy in human tissues**

shown in Figure 5.

232 Advances in Bioengineering

**arrangements**

therapy.

Red light emitted by high brightness LEDs (in the range of 630nm wavelength) promotes increased cellular energy synthesis (ATP) restructuring fibroblast collagen and elastin fibers stimulating the production of new fibers. It also assists in enhancing the flow of blood and oxygen to the skin and capillaries, increasing cellular metabolism and strengthening the walls of the capillaries. The red light is also an excellent treatment for scarring, inflammation and hard-to-heal ulcers. The red light emitted by high brightness LEDs when in contact with tissue injury has regenerative and major impact on healing characteristics. Patients with physiolog‐ ical difficulties of tissue healing can get great results with this therapy.

**Figure 1.** Arrangement of high brightness LEDs that emit red light.
