## 1 Introduction  
Anchorage in the orthodontic field can be defined as a resistance to unwanted tooth movement [1]. To achieve such resistance, anchorage units are utilized. A stable anchorage unit is a crucial element of successful orthodontic treatment. To achieve the required anchorage, dental implants, palatal implants, mini-plates, or mini-implants have been used [2, 3, 4]. These devices are attached to the basal bone or the alveolar process of the maxilla or the mandible; therefore, they provide skeletal anchorage. Given that they are in place only for the duration of the orthodontic treatment, they are usually referred to as temporary anchorage devices (TADs). In 1997, Kanomi introduced mini-implants that were specifically developed to provide stable anchorage during orthodontic treatment [5]. Because of their many advantages (versatility, independence of patient adherence, minimal surgical invasiveness, low morbidity, relative affordability, and good patient acceptance), mini-implants have become especially popular among orthodontists [6, 7, 8]. Despite their short length and small diameter, mini-implants offer stable anchorage for different types of tooth movement, including retraction, distalization, mesialization, and intrusion [9, 10]. In terms of insertion, two main kinds of mini-implants may be distinguished: self-drilling, which does not require a pilot hole, and non-self-drilling (i.e., self-tapping), which requires the drilling of a pilot hole before the implant placement. Complications of this approach to anchorage include injury of the roots of the neighboring teeth, implant loosening, and even implant fracture [11]. [PERSON] and his colleagues concluded that mini-implantstability could be influenced by implant diameter, inflammation of the peri-implant tissues, cortical bone thickness, and high mandibular plane angle [12]. It was also found that temperature elevation at the level of the cortical bone and higher torque during insertion may result in an early implant loss [9; 13; 14]. Some studies reported lower success rates with mandibular mini-implants [11; 13; 15; 16; 17] due to microcracks caused by over-torquing in thick and hard bone [9] and the consequent excessive heat production. [PERSON] and co-workers achieved optimal insertion torque by pre-drilling, and this way they managed to avoid osteonecrosis [9]. In contrast, [PERSON] et al. reported that pre-drilling for 1.6 mm self-drilling mini-implants with a 1 mm diameter pilot drill did not decrease intraosseous temperatures when the mini-implant was placed into a model mandible [18]. [PERSON] et al. measured the heat production during the placement of self-drilling mini-implants without the preparation of the pilot hole, and they found that self-drilling at speeds higher than 150 rpm causes thermal damage [14]. [PERSON] and co-workers concluded that the ratio of the diameter of the pilot hole and the mini-implant is an important factor in implant stability [12]. Despite the beneficial advantages of adequate predrilling on implant stability, the drilling procedure itself can have effects on intraosseous temperature during mini-implant placement. During the rotary cutting of the drills, the generated heat may accumulate locally, especially at the level of the denser cortical bone, which can eventually lead to necrosis [19]. The characteristics of the bone (whether the cortex of the mandible or the cortical bone of the anterior palate) can also lead to an increased risk of overheating during drilling. It is amply documented in the literature that osteonecrosis occurs when the intraosseous temperature rises to 47 \({}^{\circ}\)C [16; 20]. To our knowledge, intraosseous heat generation during pre-drilling of a pilot hole at different drilling speeds in combination with irrigation fluids of different temperature has not been previously investigated in the literature.