## 4 Discussion  
GMSCs have been proven to be effective in the treatment of various diseases and in the regenerative processes of damaged tissues [16; 55]. However, the potential of GMSCs for oral regenerative procedures is yet to be thoroughly studied, and a limited number of studies have investigated these cells' osteo/odontogenic differentiation ability. Moreover, studies utilizing LLLT and identifying the best laser protocol for stimulating GMSCs toward osteo/odontogenic differentiation still need to be made available. Accordingly, the present study aimed to evaluate the cytocompatibility and osteo/odontogenic differentiation potential of GMSCs after stimulation using two different PBM parameters. GMSCs were isolated from gingival tissues, and the positive expression of MSC cell surface markers CD73, CD90, and CD105 was confirmed following a phenotypic analysis using flow cytometry. Numerous studies previously described this phenotypic profile to be characteristic of MSCs, ensuring the successful isolation of GMSCs [56; 57]. In the present study, the bio-stimulation of GMSCs was examined after LLLT using different energy densities. The laser type used for LLLT in this study was a 980 nm diode laser, which can be available in dental offices because of its relatively low cost and ease of handling. Moreover, a diode laser with a wavelength ranging from 600 to 1200 nm and energy densities ranging from 0.4 to 4 J/cm\({}^{2}\) has been proven to have bio-stimulatory effects on different stem cells, while energies greater than 10 J/cm\({}^{2}\) might have cytotoxic effects [44]. Therefore, a single application of a diode laser with a 980 nm wavelength for 60 s using two energy densities, 1.5 J and 3 J, was examined in the present study. The current study used an MTT assay to examine the cell viability and proliferation rates of GMSCs following LLLT. The results showed a significant increase (\(p<0.05\)) in cell viability following the application of both energies, indicating that LLLT with the tested parameters was non-toxic to GMSCs and stimulated their proliferation. This effect may be attributed to the enhancement of cellular metabolism by LLLT and the increased production of adenosine triphosphate (ATP) [58], which promoted the function and proliferation of GMSCs. The MTT results on day 7 showed that lower energy doses (1.5 J/cm\({}^{2}\)) resulted in better viability of GMSCs compared to higher doses (3 J/cm\({}^{2}\)). High-energy doses of laser irradiation may cause cellular stress and damage and inhibit metabolism, thereby negatively affecting cell viability and function. On the other hand, GMSC viability was improved by exposure to lower energy doses because they were less cytotoxic and promoted GMSC growth. These findings corroborate previous studies that found low-energy-density lasers  
Figure 5: Expression of (**a**) OC, (**b**) RUNX2, (**c**) DSPP, and (**d**) DMP1 genes. * \(p<0.05\), ** \(p<0.01\), *** \(p<0.001\), and *** \(p<0.0001\) for each group compared to the control group and differences between groups. to be more effective than higher dosages at encouraging stem cell development. Large energy doses have been shown to have deleterious effects on cell photoreceptors, resulting in metabolic suppression and cell death. Higher doses of laser irradiation can cause more stress and damage to cells, which may reduce their ability to survive and function [59; 60]. In order to maintain better viability, GMSCs may be able to withstand lower energy dosages that are less cytotoxic. The current study also looked at how varying LLLT energy densities affected the ability of GMSCs to differentiate into osteeo/odorogenic tissues. It is critical to remember that precise laser irradiation parameters, such as the wavelength, energy density, and exposure period, can significantly impact how odontogenic differentiation turns out [57; 61].