## 4 Discussion  
According to previous studies [26; 27; 28], the distal tibia and radius had a value of 169 \(\pm\) 34 mg/cm\({}^{3}\) and 160 \(\pm\) 33 mg/cm\({}^{3}\). The measurements of the thoracic spine (Th10) and lumbar spine (L4) showed a value of 90.4 \(\pm\) 28.9 mg/cm\({}^{3}\) and 80.8 \(\pm\) 32.4 mg/cm\({}^{3}\). A value of 295.2 \(\pm\) 93.6 mg/cm\({}^{3}\) and 293.4 \(\pm\) 112.1 mg/cm\({}^{3}\) were observed in the right and left maxillary posterior regions. The sternums (131.57 \(\pm\) 10.14 mg/cm\({}^{3}\)) used in this study corresponded to the low-density bone. [PERSON] et al. [13] and [PERSON] et al. [14] analyzed CT to evaluate the mandibular and maxillary bones and measured the density (HU) of only trabecular bone without cortical bone. They explained that the values of bone type IV were less than +200 HU, those of types II and III were between +200 HU and +400 HU, and those of type I were larger than +400 HU. The increase in the HU gap indicated an increase in bone condensation in the peripheral and apical areas, which led to an improvement in BMD. The density of air was equal to \(-\)1000 HU, water to 0 (zero) HU in our study. Although it is difficult to make an absolute comparison with the values of those studies, it  
Figure 6: Comparison of bone density around the drilling holes on micro-positron emission tomography/computed tomography images according to diameters and techniques: (**A**) conventional technique (CD) with 3.8 mm drilling; (**B**) CD with 4.8 mm drilling; (**C**) CD with 5.8 mm drilling; (**D**) osseodesification technique in the clockwise direction (OD-C) with 3.5 mm drilling; (**E**) OD-C with 4.5 mm drilling; (**F**) OD-C with 5.5 mm drilling; (**G**) osseodesification technique in the counterclockwise direction (OD-CC) with 3.5 mm drilling; (**H**) OD-CC with 4.5 mm drilling; (**I**) OD-CC with 5.5 mm drilling. can be explained that the bone density was increased because the gap values were increased. Due to the effect of the osseedonsification technique, the gap of HU was increased by a minimum of 43 HU and a maximum of 180 HU. These results show that the poor density bone such as type IV can be changed to densified bone such as type II or III. Clinically, there are three methods to measure implant stability: insertion torque measurement, RFA, and Periotest. The IPS is directly correlated with the implant insertion torque. According to [PERSON] (1958), an implant insertion torque of 25 Ncm is sufficient for clinically successful primary stability. However, in the case of immediately loaded implants, at least 32 Ncm insertion torque is required and 45 Ncm is needed in sites of low-density bone ([PERSON] et al., 2018; [PERSON] et al., 2018). Moreover, a high insertion torque (>50 Ncm) causes microfracture or bone necrosis of the peri-implant bone area in the early healing stages, which may weaken the primary stability and result in implant failure ([PERSON] et al., 2018). Implant torque can be measured using a digital torque wrench or implant motor, but it can only be measured at the time of implant insertion ([PERSON] et al., 2018). RFA and Periotest have been proposed to clinically evaluate implant stability because of their reproducibility ([PERSON] et al., 2018). Periotest is measured as the contact time of the device during repetitive percussion between the tapping rod and implant. RFA is measured electromagnetically as an ISQ unit, which means the resonance frequency is caused by the excitation of a small implant peg attached to the implant ([PERSON] et al., 2018). RFA and Periotest, which are widely used in clinical practice and have a positive correlation with insertion torque ([PERSON] et al., 2018), were used in this study. [PERSON] et al. (2018) invented a denser bur, which can be rotated counter-clockwise (non-cutting direction) to smoothly compact bone, or clockwise (cutting direction) to drill bone.