## 4 Discussion  
This study examined the effects of inserting implants in vitro at high torques into undersized osteotomies on the cervical surface roughness and the implant surface temperature change during this process. It was demonstrated that the surface roughness values were significantly lower in the group of implants inserted in the smallest diameter preparation (2.8 mm) than in the other groups. The measured insertion torque values of this group were the highest. The high insertion torque associated with the implant placed in under-sized preparation stems in vivo from bone compression, which, in turn, leads to a higher friction coefficient between the bone walls and the implant [20]. Our findings on the changes in implant surface roughness following high-torque insertion are supported by those reported by [PERSON] et al. [21], who observed smoothing of the surface in the region of the thread crests of the  
Figure 8: Implant surface temperature amplitude (Temp-Amp) for the different study groups. The amplitude was calculated by subtracting the room temperature from the measured implant surface temperature. The values are represented as averages and standard errors. * denotes \(p<0.001\). Figure 7: Insertion torque values in Ncm measured in the different study groups and expressed as averages and standard errors. * denotes \(p<0.001\). implants inserted at high torques. The flattening of the surface roughness might result clinically in a lower success rate. It has been reported that rough surfaced implants have significantly higher success rates compared to implants with more smooth surfaces [22]. Moreover, a finite element study reported that a coarse microthread profile is more favorable than a fine profile, since it reduces shear stress in the surrounding bone [23]. The high pressure associated with the high insertion torque can also affect crestal bone remodeling in the cervical area [24; 25]. [PERSON] reported significantly higher bone loss in implants placed with insertion torques higher than 55 Ncm than in implants placed with torques lower than 55 Ncm [24]. Additionally, [PERSON] et al. [25] reported that implants placed with insertion torques of 70.8-176 Ncm demonstrated greater bone loss than did implants placed with lower torques. A positive correlation was reported between bone density and insertion torque. Type 4 bone showed lowest insertion torque values, whereas type 1 bone showed the highest values. The peak insertion torque of implants inserted according to the manufacturer's instruction in D1 bone reached 150 Ncm [26]. In the present study, the torque values observed in all study groups were higher than 55 Ncm. This result may be explained by a greater rigidity due to the elastic modulus of the synthetic bone being higher than that of natural bone [27]. Most likely, the rigidity of the synthetic bone contributed to the high insertion torque measured in the D3.65 group, even though the implants were inserted in sites prepared according to the manufacturer's instructions. Finally, the high friction associated with the insertion of implants at high torques results in excessive heat generation, which may lead to thermal injury. It has been reported that thermal injury occurs in osteoblast cell cultures that have been exposed to heat shock at 42 \({}^{\circ}\)C [28]. Heat-induced necrosis of the cortical bone of a rabbit occurs after 1 min of exposure to a temperature higher than 47 \({}^{\circ}\)C, demonstrating that damage can occur due to high insertion torques [29]. Since the average body temperature is 37 \({}^{\circ}\)C, 10 and 20 \({}^{\circ}\)C increases in temperature during the insertion of the implants in groups D3.2 and D2.8, respectively, exceed this threshold and may lead to bone necrosis [30]. Similar results were reported by [PERSON] et al. [31], who demonstrated that implant insertion in undersized preparations leads to an increase in insertion torque concomitant with an increase in the surface temperature, which might surpass the threshold level above which bone necrosis occurs.