Low - Level LASER Therapy in Dentistry

ABSTARCT

Low level laser therapy has been in use since long for its applications in medical sciences. Recently, it has started finding its use in dentistry as well. Lasers, because of its obvious advantages, has a huge potential in pediatric dentistry as well. This article explains scope of this modality in pediatric dentistry.

MANUSCRIPT

Low – Level Laser Therapy (LLLT) is a newly developed technique in dentistry, although it has been used among medical, dental, physiotherapy and veterinary professions in some parts of the world for decades. LLLT can offer tremendous therapeutic benefits to patients, such as accelerated wound healing and pain relief.

Therapeutic laser treatment, also referred to as low-level laser therapy (LLLT), offers numerous benefits. Along with the primary benefit of being nonsurgical, it promotes tissue healing and reduces edema, inflammation, and pain. For more than 30 years, LLLT has been an interesting but not well-defined field among the medical, dental, physiotherapy, and veterinary professions.

The roots of light therapy can be traced back to when our ancestors practiced heliotherapy, which gradually developed into actinotherapy and photomedicine (ie, the use of UV radiation for sterilization). In 1903, Finsen was awarded the Nobel Prize for developing the carbon arc lamp incorporating lenses and filters for the treatment of lupus vulgaris.

Early experiments confirmed that the dosage follows the so-called Arndt-Schultz law: Too small a dose gives no effect, there is a therapeutic window within a certain dose range, and doses over that range are inhibitory. Optimal doses for open wound were suggested to be 1 to 2 J/cm2. In 1973, Plog began to investigate the HeNe laser as a viable alternative to needles for acupuncture treatment1.

CLASSIFICATION

The names to identify and differentiate therapeutic lasers from surgical lasers include soft, cold, low-intensity laser therapy or LLLT. Therapeutic lasers are classified as class III medical devices, and surgical lasers are classified as class IV.

DOSAGE CALCULATION

To calculate the dose (energy density), the given energy is calculated as mW x seconds (eg, 100 mW x 10 seconds = 1000 mJ = 1 J). The dose is calculated by dividing the energy with the irradiated area. If this area is 1 cm2, the calculation is 1/1 = 1 J/ cm2. If the irradiated area is 0.25 cm2, the calculation is 1/0.25 = 4 J/cm2.

A reasonable power density (mW per cm2) is necessary to trigger biologic effects, so low output cannot be fully compensated by longer exposure, and the depth of the treatment target site must be considered. Dose recommendations in seconds or minutes can be made only if the characteristics of specific laser are known.

The amount of tissue between the laser probe and the target tissue and the type of tissue must be considered. For example, laser energy is more easily transmitted through mucosa and fat than through muscle. Hemoglobin and other pigments are strong absorbers of laser light, therefore require increased dosage. Penetration can be improved by using pressure, moving the laser closer to the target, or inducing a partial ischemia in the area. The skin coloration must also be considered because is a strong absorber of light.

Contact mode is needed for all applications with one exception. Treating an open wound requires a 2- to 4-mm separation distance between the laser and the target tissue. When contacting dental structures, some fluid might be needed to ensure full contact between the probe and the surface to minimize loss of energy.

PRINCIPLE

The principle of using LLLT is to supply direct biostimulative light energy to the body’s cells. Cellular photoreceptors (eg, cytochromophores and antenna pigments) can absorb low-level laser light and pass it on to mitochondria, which promptly produce the cell’s fuel, ATP2.

The most recognized theory to explain the effects and mechanisms of therapeutic lasers is the photochemical theory. According to this theory, the light is absorbed by certain molecules, followed by a cascade of biologic events. Suggested photoreceptors are the endogenous porphyrins and molecules in the respiratory chain, such as cytochrome c-oxidase, leading to increased ATP production2.

SAFETY MEASURE

Therapeutic lasers have been used for more than 30 years. There are no reports of patients being harmed by therapeutic lasers, and class III lasers are termed nonsignificant risk medical devices. The risk of eye injury is minimal but must be considered, especially for high-output lasers in the invisible range. Diode laser light is generally divergent; however, if the light is collimated, the risk of eye injury increases significantly. Protective goggles, specific for the wavelength, must be used for the patient and the therapist.

Following conditions should be treated only by specialist

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• Suspected malignancies
• coagulation disorders
• chronic pain

CLINICAL APPLICATIONS

By understanding the basic cellular effects of the lasers and the intended treatment goal of reducing inflammation, accelerating the healing process, and providing pain relief, the general principles of application for various clinical, conditions become clear.

The application of LLLT in dentistry is included with various clinical conditions. The general rule for intra-oral treatments is to use 2 to 4 J with the intra-oral probe and 4 to 10 J for extra-oral treatments.

POSTEXTRACTION

It is useful to irradiate the area before and after an extraction. Irradiating before the extraction with 1 J at the injection site and 2 J right below the apices induces a transient but useful effect (ie, a faster onset of local analgesia and reduced bleeding during and post extraction). After extraction, an additional 2 J/cm2 on the alveolar and gingival tissues is needed to control the swelling and inflammation. Less postoperative pain and better healing can be expected3.

HERPES LABIALIS

Herpes simplex virus infection of the lips is most common among adolescents and adults. Soft lasers have been shown to have an effect similar to Acyclovir4 and have been shown to be effective if given in the silent periods between attacks. If applied in the prodromal stage, the blister is likely to disappear in 2 to 3 days with little discomfort, rather than 8 to 14 days. LLLT also reduces the frequency of recurrence and relapse rate. Zosters and postherpetic neuralgia may also be treated5.

The irradiation from the ER:YAG laser can be used to facilitate an explosive process to cause the disruption of the virus such that it is no longer detectable. The herpetic vesicles are ruptured with minimal residual thermal damage and minimal pain, making anesthesia unnecessary.Additionally, it has been documented that low-level laser therapy (LLLT) can be used in the latent period between attacks to lower the incidence of recurrence6.

Ferreira et al 2011 7 described two clinical cases with recurrent labial herpes for which LLLT was used. Following the treatment, both patients remained symptom free during the 17-month clinical follow-up period. LLLT presented both anti-inflammatory and analgesic effects, contributing to tissue repair and fibroblast proliferation and an increase in the interval between infections; moreover, it did not contribute in viral resistance.

ORTHODONTICS

In addition to reducing the initial tension pain, laser therapy can increase the speed of tooth movements by increased osteoclastic activity on the pressure side and increased osteoblastic activity on the tension side8.

Youssef et al 20089 evaluated the effect of the low-level (GaAlAs) diode laser (809 nm, 100 mW) on the canine retraction during an orthodontic movement and to assess pain level during this treatment. The pain level was prompted by a patient questionnaire. The velocity of canine movement was significantly greater in the lased group than in the control group. The pain intensity was also at lower level in the lased group than in the control group throughout the retraction period. Our findings suggest that low-level laser therapy can highly accelerate tooth movement during orthodontic treatment and can also effectively reduce pain level.

APHTHOUS ULCERS

LLLT for the treatment of aphthae can be recommended for its pain relieving effect and the shortened healing time10, 11. The treatment dosage is the same for herpes and aphthae: 2 J/cm2 applied near contact.

MUCOSITIS

Red laser light has been shown to reduce the severity of mucositis and can be used prophylactically before radiation. The laser can also treat dermatitis induced by radiation therapy12.

Abramoff et al conducted a study to evaluate the efficacy and feasibility of low-level laser therapy (LLLT) in the prevention and treatment of chemotherapy (CT)-induced oral mucositis (OM) in young patients. They found that the ease of use of LLLT, high patient acceptance, and the positive results achieved, make this therapy feasible for the prevention and treatment of OM in young patients13.

An Indian study by Maiya et al at Kasturba Medical College, on the effect of low level helium-neon (He-Ne) laser therapy in the prevention & treatment of radiation induced mucositis in head & neck cancer patients. The study group patients were treated with He-Ne laser (wavelength 632.8 nm and output of 10mW) and control group patients were given oral analgesics, local application of anaesthetics, 0.9 per cent saline and povidine wash during the course of radiotherapy. They found that all patients tolerated the laser treatment without any adverse effect or reactions. The result showed a significant difference in pain and mucositis (P<0.001) between the two groups. At the end of radiotherapy (after 6 wk) mean pain score and mucositis grade were significantly lower (P<0.001) in the study group compared to control. They concluded that low-level He-Ne laser therapy during the radiotherapy treatment was found to be effective in preventing and treating the mucositis in head and neck cancer patients. Further studies need to be done on a larger sample to find the mechanism.

PULPOTOMY

Like other fields in dentistry LLT has been used successfully in pulpotomy as well. Vahid et al 2009 in their study concluded that LLLT can be used successfully as a complementary step to pulpotomy procedure in order to help the healing of amputated pulp. Longer follow-up periods are recommended to investigate long-term effect of LLLT pulpotomy on pulp.14

They also said that it is equal to formocresol pulpotomy and can be used in absence of formocresol.

There are also some positive data which indicate that LLLT promotes healing and dentinogenesis following pulpotomy. Ferreira et al 2006 Also found that that a GaAlAs laser with energy density of 4 J/cm2 and wavelength of 670 nm caused biomodulation in pulp cells and expression of collagen, but not collagen of the extracellular matrix, after preparation of a cavity.15

REFERENCES