Stability changes of implants placed with high insertion torque: a prospective clinical trial

Abstract

Purpose: To evaluate the changes in implant stability during a 12-week healing period, as assessed by the resonance frequency analysis (RFA), when implants are placed with high insertion torque.
Materials and Methods: From October 2019 to April 2020, 56 implants were included in the study. All implants were placed in healed ridges. Care was taken to properly undersize the osteotomy to obtain a high insertion torque. Using the RFA method, measurements of implant stability quotient (ISQ) were made at implant placement and after 3, 6, 9 and 12 weeks during the non-submerged healing period. Four measurements for each implant at each time interval were recorded, 2 in the bucco-lingual direction and 2 in the mesio-distal direction.
Results: Average insertion torque for the 56 implants was 72.41±8.89 Ncm. The average ISQ values were 74.72±4.08, 73.19±4.91, 73.51±4.86, 74.55±4.97, and 75.43±5.14 at 0, 3, 6, 9 and 12 weeks respectively. The slight average decrease of 1.53 ISQ units at 3 weeks was statistically significant (-p-value=0.036). A significant gradual increase occurred between the 3rd and the 12th week (-p-value =0.017). No difference was found between baseline and 12 weeks (-p-value= 0.361). Not all implants lost ISQ units at 3 weeks. While 36 implants lost an average of 4.64 ISQ units (-p-value <0.0001) at 3 weeks, 20 implants gained an average of 4.07 units at the same time interval (-p-value <0.0001). Conclusions: Implant stability was relatively maintained at high ISQ levels throughout the 12 weeks period. This study suggests that high peri-implant bone strain achieved during a high insertion torque implant placement is not deleterious to implant stability, but on the contrary it keeps the implant continuously stable throughout the healing period.