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Received Nov 15, 2017; Accepted Jan 10, 2018
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1. Introduction
Oral mucositis (OM) is an acute and ulcerative inflammation of the oropharyngeal mucosa caused by cytotoxic cancer therapy [1]. It is one of the most common adverse effects of head and neck irradiation and is even more frequent when associated with chemotherapy [2]. The course of OM frequently leads to severe pain that is sufficiently severe to impair speech, eating, and swallowing, thus reducing the quality of life of the patients [3]. These events can lead to hospital admission involving substantial additional costs and even interruption of oncologic treatment [4].
The injury to healthy tissue caused by irradiation and OM-related effects begins with cellular death triggered by direct damage to DNA, followed by intense oxidative stress [5]. Most of the injury has been associated with the latter effect, which activates and amplifies signaling pathways that leads to inflammation and apoptosis, thus resulting in ulceration and further damage inflicted by bacterial colonization on the surface of lesions [6, 7]. Improved irradiation techniques, control of comorbidities, and adequate oral hygiene mitigate the burden of OM [8]. Furthermore, specific prophylactic substances have been proposed, such as mucosal protectors, steroidal and non-steroidal anti-inflammatory and antibiotic agents, or growth-factors, but none of these approaches is considered sufficient to prevent the lesions [1].
Low-power laser irradiation, at present known as photobiomodulation, has been used since the 1980s to control OM [9]. This procedure can reduce pain, severity, and duration of the lesions [10]. Visible or infrared light energy originates intracellular photochemical reactions capable of controlling pain stimuli and in the last instance to stimulate tissue repair [11]. The use of photobiomodulation has steadily increased among dental care providers to oncologic patients due to being readily accessible and easy to use, of a noninvasive nature, and having no serious adverse effects [12, 13]. However, photobiomodulation protocols for the treatment of OM vary widely, leading to difficulties in standardizing its use in clinical settings [14–16]. Moreover, the risk of stimulating the growth of neoplastic or residual neoplastic cells has limited its use to...