## 1 Introduction  
Periodontal problems are one of the most critical dental diseases in developing countries. This condition is harmful to the health of tissues that support teeth. Some microorganisms cause this disease by harming the alveolar bone and the periodontal ligament, appearing as a periodontal pocket, bone loss, or both [1]. Mesenchymal Stem Cells are multipotent and undifferentiated cells that can transform into different tissues according to the signals they receive. These cells are obtained from other sources such as bone marrow, orofacial tissue, skin, and adipose tissue [2, 3]. Adipose tissue has been introduced as a promising source of MSCs, which can be obtained with minimal discomfort for patients, as subcutaneous adipose tissue is usually discarded after cosmetic surgery procedures. In addition, several studies have shown that Mesenchymal Cells derived from fat tissue possess a yield that is 100-500 times higher than cells derived and aspirated from bone marrow [4, 5, 6]. Recently, [PERSON] et al. isolated Adipose-Derived Stem Cells (ADSCs) from a mass of fatty tissue in the oral cavity called the Buccal Fat Pad. Under appropriate conditions, it has been shown that ADSCs derived from the Buccal Fat Pad (BFP) are differentiated into chondrocytes, osteoblasts, or fat cells in laboratory conditions [7]. Khojaste and Sadeghi have recently used (BFPSCs) in connection with iliac bone block grafting and increased the rate of new bone formation and decreased secondary bone resorption. This was performed in extensively atrophic jaws [8].  
Lasers are one of the most widely used tools in dental activities, creating many developments in various fields in the last 35 years of the 20 th century [9]. For the first time in phototherapy treatments, [PERSON] et al. reported the wound healing rate by using a low-level laser [10]. In 1993, the first research on the use of low-level lasers in dentistry was performed by [PERSON]. He wanted to investigate the impact of the low-level laser in decreasing pain and swelling after the bilateral extraction of the mandibular-impacted third molar. This research observed no difference between the laser and the placebo [11]. In other studies, the low-level laser was used for increasing cell proliferation [12], osteoblastic differentiation of Mesenchymal Stem Cells [13], increasing functional attachment of titanium implants to bones, and improving bone healing and mineralization [14]. In periodontal treatments, the low-level laser has been shown as an additional treatment after non-surgical therapies [15; 16; 17], gingivectomy [18; 19; 20; 21], and regenerative treatments [22]. In addition, low-level laser therapy is now considered as photobiomodulation (PBM) therapy [23]. Photobiomodulation therapy means that tissues are exposed to lasers or LEDs (Light Emitting Diodes). According to the light parameters, this treatment stimulates and inhibits the responses [24]. An increase in the speed of healing is probably related to the fact that the laser increases cell proliferation. The laser energy is absorbed by intercellular chromophores and converts them into metabolic energy, which is used in the mitochondrial respiratory chain to produce ATP, increase DNA activity, and synthesize RNA and proteins [25]. The impact of PBM is related to photons taken by the chromophore cells and tissues and is changed by different factors such as wavelength, energy density, and power density. Wavelength is the most crucial factor between them [26]. Thus, parameter standardization helps improve the impact of this technology [27]. We performed this study because of heterogeneities in studies that compare different energy densities with various wavelengths of lasers in PBM [27; 28; 29]. As a result, this research compared the impacts of different wavelengths and energy densities of diode lasers on the proliferation of human Buccal Fat Pad Mesenchymal Stem Cells.