## 4 Discussion
Most clinicians perform some drilling strategy depending on the perceived bone quality to achieve adequate primary stability. Thread-forming drills might be used whenever implants are placed in hard bone (Lekholm and Zarb type I and II) and to underdrill the implant bed whenever soft bone is felt (Lekholm and Zarb type III and IV) [41; 42]. This high primary stability may be explained by the pressure setting generated by the underdrilling, which induces additional friction [25; 34; 35]. However, new bone preparation techniques, such as Osseodensification, are emerging, with significant results compared to the conventional technique [42; 43]. Another notable finding was that the significantly lower ISQ obtained at the moment of the surgery for the conical implants was maintained at the ISQ after three months, which may imply that the implant's macro-geometry (thread design) may play a role in both primary and secondary stability. Despite the subjective tactile evaluation of bone quality being used to assess softer bone when placing the conical implants, such differences did not correspond with the objective bone density assessment, which may indicate that implant macro-geometry may play a role in the tactile perception during implant placement. This study also explored other factors, such as implant location in the arch (incisors-canines, bicuspids-molars) and whether the implants were placed in the maxilla or mandible. Our results showed that the more posterior the implant location, the lower the bone density. The values for the mean bone density according to implant location within the arch observed in the present study (Table 4) were similar to those reported by [PERSON] et al. [7]. These authors obtained a mean value of 684 \(\pm\) 131 HU in the anterior region and 568.5 \(\pm\) 170 HU in the posterior region. Therefore, in line with the results reported by [PERSON] et al. [44] in 2007, the highest values for bone density (HU) are found in the anterior region, and the lowest values (HU) occur in the posterior region. This study found no statistically significant differences between the implants placed in the maxilla or mandible regarding primary stability, secondary stability, or bone density (Table 5), in contrast to the findings of other researchers [7; 43; 44]. This study also found that implant length (Table 7) did not significantly affect primary stability, secondary stability, or bone density. However, implant diameter was found to have significant effects (Table 6) on insertion torque and bone density variables. Wide-diameter implants achieved significantly lower insertion torque values than implants with a standard diameter. There are likely to be two main reasons for these results. Firstly, most implants (63.6%) were placed in the maxilla, where bone density is expected to be lower (reduced HU). Secondly, all the wide implants were placed in the molar region, where the mean bone density was the lowest. In contrast, [PERSON] et al. [45] reported that a wider implant diameter was associated with a greater insertion torque. However, this was an in vitro study in which bone density would be difficult to control, given the challenge of reproducing human bone's macroscopic and microscopic characteristics in models. In a clinical study using a similar methodology, [PERSON] et al. [46] compared cylindrical (Nobel Parallel) and conical (Nobel Active) implants and found no significant differences relating to implant diameter and insertion torque (\(p\) = 0.57). However, they did find that implant diameter had a significant effect (\(p\) = 0.04) on the ISQ on the day of the surgery. While the present research did not identify significant differences (\(p\) = 0.162) related to implant diameter and ISQ on the day of the surgery, lower ISQ scores were achieved for the wide implants compared to the standard-diameter implants. These results support those presented by [PERSON] et al. [46].