## 4 Discussion  
Several studies have demonstrated the efficacy of PBM in decreasing the severity and duration of OM. This positive response is probably due to the action of PBM on the different phases of OM, through the decrease in the inflammatory response, the reduction of amplification, and the acceleration of the healing process through promoting growth factors release, the proliferation of fibroblasts, and deposition of collagen. The exact mechanism of PBM to explain this response is still not completely understood [32]. Several local tissue reactions have been associated with the pathogenesis of OM, including the damage caused by reactive oxygen species, inflammatory cytokines (Interleukin-6 (IL-6), tumor necrosis factor-\(\alpha\) (TNF-\(\alpha\)), interleukin-1 beta (IL-18)), and submucosal connective tissue damage. Some authors \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Variables**} & **Preventive Group** & **Control Group** & \multirow{2}{*}{\(\chi^{2}\)} & \multirow{2}{*}{\(p\)**-Value**} \\  & **(PG)** & **(CG)** & & \\ \hline
**Severity of Oral Mucositis (OM)** & & & & \\ \hline Non-ulcerative OM (\(\leq\) Grade I) & 12 & 3 & 8424 & 0.003 \({}^{*}\) \\ Ulcerative OM (\(\geq\) Grade II) & 8 & 17 & & \\ \hline
**Incidence of OM** & & & & \\ \hline No OM (Grade 0) & 8 & 0 & 10,000 & 0.002 \({}^{*}\) \\ With OM (\(\geq\) Grade I) & 12 & 20 & & \\ \hline \hline \end{tabular} \({}^{*}p<\) 0.05.  
\end{table} 
Table 4: Comparison between groups for the incidence and severity of oral mucositis. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Variables**} & **Preventive Group** & **Control Group** & \multirow{2}{*}{\(p\)**-Value**} \\  & **(PG)Median \(\pm\) SD** & **(CG)Median \(\pm\) SD** & & \\ \hline Age & \(46.5\pm 14.43\) & \(45.55\pm 16.01\) & 0.914 \\ \hline Max grade of oral mucositis & \(1.00\pm 0.92\) & \(2.25\pm 0.85\) & \(<\)0.001 \({}^{*}\) \\ \hline Duration of oral mucositis of: & & & \\ \hline Grade 0 & \(17.30\pm 3.03\) & \(11.00\pm 5.20\) & \(<\)0.001 \({}^{*}\) \\ Grade I & \(2.15\pm 2.81\) & \(6.30\pm 3.42\) & \(<\)0.001 \({}^{*}\) \\ Grade II & \(2.20\pm 2.97\) & \(5.70\pm 6.16\) & 0.025 \({}^{*}\) \\ Grade III & \(0.00\pm 0.00\) & \(2.0\pm 4.36\) & 0.009 \({}^{*}\) \\ Grade IV & \(0.00\pm 0.00\) & \(0.55\pm 1.76\) & 0.152 \\ \hline Total duration of oral mucositis & \(4.70\pm 5.05\) & \(15.00\pm 8.83\) & \(<\)0.001 \({}^{*}\) \\ \hline Mean oral mucositis score at & & & \\ \hline Evaluation time points (E): & & & \\ \hline E0 & \(0.05\pm 0.22\) & \(0.15\pm 0.37\) & 0.298 \\ E1 & \(0.05\pm 0.22\) & \(0.55\pm 0.83\) & 0.008 \({}^{*}\) \\ E2 & \(0.56\pm 0.68\) & \(1.25\pm 1.12\) & 0.005 \({}^{*}\) \\ E3 & \(0.95\pm 0.94\) & \(1.35\pm 1  
have hypothesized that the reduction in the severity of OM with PBM may be due to the decrease in reactive oxygen species or the reduction of proinflammatory cytokines. This speculation was based on the premise that low-power lasers may be absorbed by specific molecules and other intracellular organelles in addition to the mitochondria [33]. Therefore, some studies have investigated the effect of PBM on the level and behavior of the inflammatory mediators in the blood and/or saliva in patients with OM. However, these studies could not find a complete link between the positive response of PBM and the modulation of the inflammatory mediators [32; 34]. [PERSON] et al. observed an elevation in the IL-6 concentration in both groups (laser and control) at the time of OM development. It was noticed that this elevation was accompanied by the increase in TNF-\(\alpha\) and IL-1\(\beta\) concentration in the saliva of the laser group. The authors suggested that these findings may explain the decrease in the severity of OM, where IL-6 plays a role in the systemic response to injury by acting as a pro-inflammatory and anti-inflammatory cytokine [32]. Although too much increase in TNF-\(\alpha\) and IL-1\(\beta\) may lead to mucosal damage, moderate levels are crucial for inducing the cell regeneration process [22].