## 1 Introduction  
Biomechanics is an important variable in the orthodontic equation. It includes both a biological element involving the tooth and its periodontium, and a mechanical element defining the force system. In fact, [PERSON]'s third law of motion, which defines the orthodontic movement, states that for every action (force) in nature there is an equal and opposite reaction. How does one counteract these reactive forces? It took until 1923 for the term \"anchorage\" to be defined by [PERSON] as \"the base against which orthodontic force or reaction of orthodontic force is applied\" [1]. Many anchorage systems have been developed since, but it was not until the introduction of skeletal anchorage as a source of fixed anchorage to orthodontic treatment that many problems, including patient cooperation, were solved [2]. Mini-screws offer many advantages due to their small dimensions, such as: immediate loading, multiple placement sites including interdental areas, relatively simple placement and removal, and low cost. Mini-screws are used to assist and improve the efficacy of orthodontic treatments generally performed with conventional buccal or lingual appliances or aligners [3]. These clinical situations include intrusion of teeth, extrusion of teeth, correction of bite issues, space closure, and correction of asymmetries [4; 5]. After loading, however, mini-screws can lose stability [6] or be displaced [7] over time. The literature shows different mini-screw success rates depending on the insertion site with the area of the palate showing the best results [8]. On the contrary, insertion between the roots has shown the lowest values [9]. Nevertheless, [PERSON] et al. showed that minimally mobile mini-screws remained clinically successful up to eight months after insertion [10]. In addition, upon loading, [PERSON] et al. demonstrated that the alveolar bone density around mini-screws increased after three months [11]. For this reason, the considerations pertaining to the volume and density of bone are recognized as some of many critical aspects for achieving adequate stability, and consequently, long-term clinical success [12]. Therefore, measuring implant stability is necessary [13]. The two most commonly used tests to assess implant stability are the Periotest and the Resonance Frequency Analysis (RFA) performed by the Osstell ISQ (Implant Stability Quotient) because they have the least invasiveness and acceptable clinical accuracies [13; 14]. Photobiomodulation therapy (PBMt) is a non-invasive remedy that implies the use of a non-ionizing electromagnetic energy that triggers photochemical reactions within cellular structures that are receptive to photons [15]. Mitochondria and light-sensitive ion channels are particularly receptive to this process [16]. The biostimulatory effects of PBM therapy have resulted in beneficial therapeutic outcomes including, but not limited to, the alleviation of pain, decrease of inflammation, immunomodulation, and the promotion of wound healing and tissue regeneration [17]. In the field of dentistry, several studies have investigated an increase in the stability of implants and bone-implant contact (BIC) factor following laser light application [18]. PBMt enhances the process of bone healing and increases primary stability [19]. In addition, it displays a biostimulatory effect on bone tissue by increasing proliferation and differentiation rates of osteoblasts accelerating bone formation and repair [20]. Primary stability is important for achieving successful immediate or early loading of dental implants [21]. Since orthodontic mini-screws are usually lost during the first weeks after loading [22], enhancing the overall stability of the mini-screw is an important step towards achieving successful therapy. A few animal and human studies have investigated the effect of PBMt on the stability of orthodontic mini-screws [11; 19].