## 4 Discussion  
Many factors can affect the success of implant therapy, but patient-related factors and implant-related factors are perhaps the two most important variables to consider [26; 27]. Achieving primary stability in implant surgery is one of the many desired outcomes for clinicians [28; 29], and it is reported to depend mainly on bone density and implant macro geometry [30]. Research relating to insertion torque and implant success is becoming increasingly frequent. In a randomized clinical trial lasting 12 months, [PERSON] et al. [31] evaluated the influence of insertion torque and peri-implant bone stability. Their results showed that implants placed with a high insertion torque (\(\geq\)50 Ncm) showed greater peri-implant bone remodeling and greater recession of the buccal soft tissues. Following this trend, [PERSON] et al. [32] observed similar results in terms of bone resorption (less marginal bone loss and less facial soft tissue recession) and implant success. They obtained a success rate of 98.2% in implants placed at a regular insertion torque (\(<\)50 Ncm) and 91.3% in implants placed at a high insertion torque (\(\geq\)50 Ncm). The present study's first overall correlation analysis, i.e., before the data were divided into implant macro-geometry groups, showed a significant association between the tactile evaluation of bone density during the preparation of the osteotomy and the insertion torque, ISQ on the day of the surgery, and bone-density values attained using the CBCT. However, when the correlation analysis was conducted for each group of implants, the conical-shaped implants had an inverse significant correlation with the insertion torque and the bone density, and the cylindrical-shaped implants only produced significant results for the insertion torque, as mentioned earlier (Table 2). Several studies have analyzed the correlation between the surgeon's tactile sensation and variables such as insertion torque, ISQ, and bone density values derived from CBCT [7; 33; 34; 35]. [PERSON] et al. [35] identified a moderate, negative association between the insertion torque and the bone type selected based on a tactile evaluation. The present study found a negative association between the insertion torque and tactile sensation for conical (rho = \(-\)0.403; \(p<0.001\)) and parallel implants (rho = \(-\)0.366; \(p\) = 0.026). These differences may be influenced by the macro-geometry of the implants, since no prior studies have been found comparing all these variables and implant macro-designs. The present study significantly demonstrated that the cylindrical implants provided higher primary stability values (insertion torque and ISQ values) than the conical implants. In contrast, [PERSON] et al. [36] showed that conical and cylindrical implants of the same length but different diameters placed in the posterior region of the mandible produced similar results for primary stability. Likewise, authors such as [PERSON] et al. [37] and [PERSON] et al. [38] found no significant differences between the primary stability of conical and cylindrical implants. However, the literature suggests that implant macro geometries with hybrid and tapered designs provide greater primary stability [39; 30; 40]. Furthermore, several of the studies mentioned above were in vitro [38], animal-models [36; 39], or retrospective clinical studies [7], and each study used different macro-designs (conical, cylindrical, and hybrid implants with different thread designs and pitches,with or without micro-spirals in the coronal portion), which makes it challenging to draw any conclusions on this issue. Thus, further clinical studies would be advisable to investigate the effects of macro geometry on primary stability, including patient-related clinical variables. Another possible reason for the higher primary stability values for the cylindrical implants was the type of surgical procedure performed during the osteotomy.