## 1 Introduction  
Mini-implants are used routinely for enhancing anchorage in orthodontic treatments [1, 2, 3, 4]. Factors such as the cortical bone thickness, the diameter and length of the mini-implant, and the angle and point of insertion in the mucosa have been proved to be crucial to successful placement [5, 6]. Primary stability is also important to the implant's survival rate. It depends on the bone quality, implant design, and preparation of the implant site [7]. Primary stability is measured using resonance frequency analysis (RFA) through a transducer attached to an implant fixture. The result is displayed as an implant stability quotient (ISQ) value, on a scale that indicates the level of stability of dental implants [8, 9, 10, 11]. It is also measured using Peritost values (PTV) or insertion torque measurement [12, 13, 14]. The cortical bone thickness has been found to be directly proportional to the success rate of the mini-implant [15], while [PERSON] et al. [16] stated that two crucial factors for primary stability are bone quality and quantity, which also affect the long-term survival of the mini-implant. [PERSON] et al. [17], in agreement with [PERSON] et al. [18], stated that the primary stability of mini-implants depends on the cortical bone thickness in conjunction with the trabecular bone density, and concluded that the primary stability of a mini-implant can be estimated by computed tomography measurements of the cortical bone thickness and trabecular bone density, before treatment. Cone beam computed tomography (CBCT) was introduced in 1998 [19], and is now widely used in dentistry for diagnosis and treatment planning, especially for dental implants and surgical cases [20]. In orthodontics, it is used in cases of impacted teeth [21], but clinicians recommend its use even in the field of temporomandibular joint (TMJ) problems, cleft lip and palate (CL/P), supernumerary teeth, or mini-implant placement. However, according to the \"as low as reasonably achievable\" radiography principle, we should limit the use of CBCT to only absolutely necessary occasions and, when we do so, CBCT should be performed using the smallest possible field of view (FOV) [22]. Among the above-mentioned factors that affect the primary stability of temporary anchorage devices, cortical bone thickness is believed to be the most important one, as these devices are not osseointegrated, but are mechanically retained in the bone [15]. Computed tomography (CT) [23] and CBCT [24] are both suitable for the assessment of cortical bone thickness. Measurements are usually conducted at several interradicular areas, and at several height levels. The cementoenamel junction (CEJ) and alveolar crest are the two usual reference planes that are used. Cortical bone thickness was measured by [PERSON] and [PERSON] [25] in buccal segments and interdental areas from the second molar on the right side, to the second molar on the left, for the upper and lower jaw at 2, 4, and 6 mm from the alveolar crest, on dry skulls, utilizing CBCT imaging. The same reference plane was used by [PERSON] et al. [26], who measured the thickness at 1 mm to 15 mm distance from the plane, in 1 mm intervals, in a CT study, while the alveolar process bone thickness was assessed by [PERSON] et al. [27] at 1.5, 3, 6, and 9 mm from the CEJ plane, on axial slices, using the CBCT data of 50 adults. The cementoenamel junction was also used as a reference in the research of [PERSON] et al. [28], who measured the cortical bone thickness at 2 mm, 4 mm, and 6 mm from the CEJ, in a CBCT study of 100 patients divided into two age groups (adolescents and adults). Bone density has been measured in several studies utilizing computed tomography (CT) [29; 30] or CBCT [31; 32; 33; 34; 35] in Hounsfield units (HU). The assessment of bone density at sites where implants are scheduled to be placed is helpful in selecting the exact point for insertion or surgical methodology.