According to the previous literature, the obtaining osseointegration is integral to the intraosseous stability of the implant body during the healing period [24]; moreover, the importance of postoperative assessment of the intraosseous stability of the implant has also been reported [10]. Intraosseous stability of the implant body is evaluated immediately after the implant insertion and during the healing period after surgery.

The primary stability is necessary for implant treatment, and the absence of primary stability may result in treatment failure [25, 26]. Primary stability was evaluated with insertion torque immediately after the implant insertion.

This study had a short implementation period, and it was difficult to recruit a large number of participants. Therefore, participants had a bias in age and gender, and the treated area was also biased. We referred previous publication to review the effect of participant’s age and gender at insertion torque value. According to the above literature reviewing, the participant’s age and gender did not affect insertion torque value [27,28,29]. However, it was thought that there was a possibility that the number of participants influenced the result.

In this study, primary stability was evaluated with insertion torque value measured by manual torque wrench immediately after implant insertion. Manual torque wrench is the medical instrument used for implant treatment frequently. A recent study about insertion torque that compared electronically controlled torque wrench with manual torque wrench states that the measurement results of both instruments were similar [30]. Manual torque wrench is classified into three styles (coil, toggle, and beam style). In this study, beam style manual torque wrench was used. It was reported that beam style torque wrench present most precise result compared with other two kinds of torque wrenches [31]. As described above, the measurement procedure of insertion torque value in this study is thought to be acceptable.