Medical fibers:A New Approach to Relieve Pain in Some Painful Oral Diseases

Keywords:medical, fibers, treatment, surgical,  Time:24-11-2015
1. Introduction

CO2 laser has been used as a very useful device in surgery for ablation, coagulation and cutting the tissues for the last four decades. It is interesting to know that this high power laser can also be used as a therapeutic medical laser fibers for immediate pain reduction in some oral lesions without any visible side effects such as ulceration, erosion formation and even erythema.
Recently few case reports and clinical trials have been published about using CO2 laser in non-ablative manner to reduce pain in oral lesions. In these studies, the oral painful lesions were irradiated through a layer of transparent, non-anesthetic gel with high water content to reduce the beam absorption by the soft tissue. The patients reported immediate and significant pain relief after laser irradiation. The procedure was painless and anesthesia was not required. This technique was called non-thermal, Non-Ablative CO2 Laser Therapy (NACLT). The results of powermetry and thermometry demonstrated the low power nature of NACLT. However there are some differences between analgesic effects of NACLT and the other classical low power lasers which will be discussed in the next sections.   
To provide a comprehensive understanding of NACLT, this chapter is organized in several sections. First, due to low level therapeutic nature of NACLT, conventional low power therapeutic lasers, their biological effects and their pain relieving properties are reviewed. Then, a discussion about the interesting analgesic effects of CO2 lasers is presented. In the next section, NACLT as a new low level surgical laser fibers therapy procedure and its pain relieving applications in painful oral lesions is discussed. Finally, the presumed mechanisms of analgesic effects of NACLT are covered.

2. Low level laser therapy (laser phototherapy)

Low-level laser (or light) therapy (LLLT) has been investigated and used clinically for over 40 years. However, it is only in relatively recent times that LLLT has become scientifically and clinically accepted by even a fraction of the medical community (Hamblin 2010).  

The history of the use of laser phototherapy in medicine goes back to the late 1960s, only eight years after the invention of the first laser (Ruby laser) by Theodore Maiman. In 1967, Endre Mester in Semmelweis University, Budapest, Hungary decided to test if laser radiation might cause cancer in mice. He shaved the dorsal hair of the mice, divided them into two groups and irradiated the shaved areas with a low powered ruby laser (694-nm) in one group. They did not get cancer and to his surprise the hair on the treated group grew back more quickly than the untreated group. This was the first demonstration of "laser biostimulation" .

In early 1960’s, the first low level laser, Helium-Neon was developed by Professor Ali Javan. It emits visible, red light with a wavelength of 632.8nm. This low power laser has been used extensively in experimental and therapeutic studies. Today, the semiconductor lasers, including InGaAlP lasers (633-700nm), GaAlAs lasers (780-890nm, invisible, near infrared area), GaAs laser (904nm, invisible, near infrared area) are widely used by researchers and clinicians.

LLLT originally thought to be a peculiar property of laser light (soft or cold lasers); the subject has now broadened, using non-coherent light (light-emitting diodes, LEDs). Today, medical treatment with coherent-light sources (lasers) or noncoherent light (LEDs) has passed through its childhood and adolescence (Hamblin, Waynant et al. 2006). Currently, low-level laser (or light) therapy (LLLT) is practiced as part of physical therapy in many parts of the world. Although LLLT was used mainly for wound healing and pain relief, the medical applications of LLLT have broadened to include diseases such as stroke, myocardial infarction, and degenerative or traumatic brain disorders (Hashmi, Huang et al. 2010).

Although many experimental and clinical studies have reported the positive effects of phototherapy to promote wound healing , pain relief and anti-inflammatory effects, some negative reports also have been published, further confounding the issue (Demidova-Rice, Salomatina et al. 2007), for instance regarding the application of laser phototherapy on wound healing (Posten, Wrone et al. 2005). This controversy seems to be due to two main reasons; first of all, the basic biochemical mechanisms underlying these biological effects are not completely understood. Secondly, the complexity of rationally choosing amongst a large number of laser irradiation parameters (such as wavelength, fluence, power density, pulse structure and treatment timing), inappropriate anatomical treatment location and concurrent patient medication (such as steroidal and non-steroidal anti-inflammatories which can inhibit healing) has led to conflicting results and publication of a number of unfavourable, as well as many favourable, studies.

2.2 A brief review on biological effects of low level therapeutic lasers

Low level laser (or light) therapy (LLLT) is the application of light (usually a low power laser or LED in the range of 1mW – 500mW) to a pathology to promote wound healing and tissue repair, reduce inflammation and relieve pain. The light is typically of narrow spectral width in the red or near infrared spectrum (600nm – 1000nm); at power densities (between 1mw-5W/cm2) (Huang, Chen et al. 2009), not associated with macroscopic thermal effects, in contrast to thermally mediated surgical applications.

In using high power surgical lasers, the collimation of laser light leads to the emission of a narrow, intense beam of light and is used for precise tissue destruction (photothermal effect). However, in LLLT, light radiation intensities are so low that the resulting biological effects are ascribable to physical or chemical changes associated with the interaction of cells and tissues with the laser radiation, and not simply to a result of heating (Snyder, Byrnes et al. 2002; Gigo-Benato, Geuna et al. 2005).  
The main areas of medicine where laser phototherapy has a known and major role are as follows: promoting wound healing, tissue repair and prevention of tissue death, relief of inflammation in chronic diseases and injuries with its associated pain and edema, relief of neurogenic pain and some neurological problems.
The first law of photobiology states that for low power visible light to have any effect on a living biological system, the photons must be absorbed by electronic absorption bands belonging to some molecular photoacceptors, or chromophores (Sutherland 2002; Huang, Chen et al. 2009). Red and near infrared light is absorbed by photoreceptors contained in the protein components of the respiratory chain located in  mitochondria, in particular cytochrome c oxidase and flavoproteins like NADH-dehydrogenase. This can lead to a short time activation of respiratory chain and oxidation of NADH pool leading to changes in the redox state of both mitochondria and cytoplasm, leading to increased ATP production, and biological responses at the cellular level through cascades of biochemical reactions (Karu 1989; Karu, Pyatibrat et al. 2004; Karu and Kolyakov 2005). These effects in turn lead to increased cell proliferation and migration, modulation in levels of cytokines, growth factors, inflammatory mediators, and increased tissue oxygenation. The results of these biochemical and cellular changes in animals and patients lead to  valuable biological effects such as promoting wound healing and tissue repair, relief of inflammation, pain reduction, and amelioration of damage after heart attacks, stroke, nerve injury and even retinal toxicity.  

2.3 Pain relieving effects of low level therapeutic lasers

Low-level laser therapy (LLLT) is increasingly recognized as an appropriate option for pain relief. In fact, it is for this indication that biostimulative lasers have been approved for marketing by the U.S. Food and Drug Administration through the premarket notification/510(k) (Gigo-Benato, Geuna et al. 2005). Many studies have demonstrated the efficacy of phototherapy in various pain syndromes (Tuner and Hode 2010). Responding to the increasing levels of evidence, the World Health Organization’s Committee of the Decay of the Bone and Joint has also recently incorporated LLLT into guidelines for treatment of neck pain.