## 4 Discussion  
In this study, a significant decrease in pain with PBM was observed on day 0, day 1, and day 7 compared to the CG. These positive results may be due to the reported PBM anti-inflammatory, analgesic, and biomodulatory effects. Regarding the absence of statistical differences in pain reduction on day 3 between groups, it has been reported in the literature that the local inflammation around the surgical wound and pain gradually increases and reaches a peak on the second postoperative day, then starts to decrease gradually [29]. This may explain the finding of this study that the difference in pain level was not significant between both groups at day 3, as the level of pain and inflammation normally starts to decrease gradually in both groups. Figure 5: The average number of painkillers taken in the Test Group (TG) and Control Group (CG). Figure 6: The average score of each patient’s daily activities questionnaire in the Test Group (TG) and Control Group (CG). Although the mechanism of PBM effects is widely studied and many mechanisms have been reported, the exact mechanism has not been completely agreed upon yet [22]. One of the reported mechanisms is PBM's capability to regulate pain perception through inhibiting cyclooxygenase-2, influencing the redox reactions, and downregulating biochemical proteins, such as prostaglandandins, interleukins, and tumor necrosis factor [30; 31]. Another mechanism is PBM's ability to decrease vessel size and permeability and, consequently, control the influx of proinflammatory cytokines. Some authors have proposed this mechanism as an explanation of an observed less acute inflammatory condition after PBM application [32]. Other studies suggested that PBM can modify pain perception by changing the central uptake and release of serotonin and acetylcholine, stimulating the production of endorphins, and inhibiting bradykinin [20; 33]. The positive impact of PBM on the vital capacity, motility, and viability of irradiated cells is also one of the proposed PBM effect mechanisms [34]. The mitochondria of irradiated cells, the first cellular organelles that absorb the laser energy, increase the production of adenosine triphosphate after PBM application, which, consequently, leads to an increase in cellular turnover, including tissue proliferation and oxygenation. These effects, in turn, have a positive impact on tissues that suffer from poor cellular proliferation due to the privilege of an acidic medium after injury [22; 35]. PBM's role in the reduction in discomfort after mandibular third molar extraction has been widely studied using a wide range of parameters [22; 24; 36]. In a recent systematic review, limited evidence of the effect of PBM was observed for the control of pain, edema, and trismus following third molar extractions. This observation might be due to variation in the used wavelengths, parameters, application modality (intraoral, extraoral, or both), protocol timing (preoperative, postoperative, or both), and number of sessions [24]. Defining the effective dose of PBM is a challenging element, as inadequate doses or inappropriate protocols may influence the results. Regarding wavelengths, it is generally believed that pain and inflammation reduction can be achieved using lasers in the red spectrum. In contrast, the control of edema and trismus can be achieved using lasers in the infrared spectrum due to their greater tissue penetration ability [24; 37]. In the literature, the range of the studied wavelengths was from 632.8 nm to 940 nm [22]. The most studied wavelength was 810 nm. In a systematic review, it was found that the majority of the included studies (75.8%) used infrared lasers, and the minority (9.1%) used red lasers [24]. In addition, [PERSON] et al. observed, in their systematic review, that pain reduction was mostly associated with studies using wavelengths between 660 nm and 830 nm, while studies with wavelengths between 904 and 940 nm showed efficacy on the 2 nd postoperative day but not on the 5 th, 7 th, and 14 th postoperative days [23].