This study compared the outcomes of implant therapy with and without IVS. No implant loss was observed in either group, and the 3-year implant survival rate was 100% in both groups. Derks et al. used patient data from the Swedish Social Insurance Agency to examine implant survival in 539 patients and found that the early implant loss rate was higher with the Astra Tech implant system than with the Straumann or Nobel systems [20]. Although their results differ from ours, unlike that study, we excluded patients with a history of smoking, diabetes, and risk factors for periodontal disease, which we believe resulted in a high implant survival rate of 100%.
The PCR of the remaining teeth immediately before implant placement in the IVS group was significantly higher than that in the control group; however, BOP was not significantly different between the groups in 3 years after superstructure attachment. The reason for the higher PCR of the remaining teeth immediately before implant placement in the IVS group may be that the patients who opted for IVS were more likely to be anxious or fearful of dental treatment and were less willing to receive dental prophylaxis. In contrast, both BOP and bone loss values 3 years after superstructure attachment were lower in the IVS group, and the number of patients with maintenance visits was significantly higher in the IVS group than in the control group. These findings suggest that the reduced stress with IVS results in psychological changes in patients undergoing dental procedures, resulting in an increased willingness to receive dental prophylaxis.
Regular maintenance is an important determinant of implant outcomes. Gary et al. reported peri-implant mucositis and peri-implantitis in 46–63% and in 19–23% of patients with properly placed implants. Based on these findings, they recommended that professional maintenance should be performed every 3–6 months [21]. Rajendra et al. and Bjarni et al. demonstrated that regular maintenance improves the implant survival rate, highlighting its importance [22, 23]. These findings suggest that application of IVS for implant therapy can improve survival of implants and remaining teeth, thereby improving patients’ quality of life.
Furthermore, the number of patients with two or more missing teeth who underwent additional implant placement was significantly higher in the IVS group than in the control group. This suggests that IVS reduces patients’ psychological burden and improves satisfaction, resulting in an increased number of patients undergoing additional implant placement. Based on a questionnaire survey of 111 patients, Walton et al. found that the most common reason for refusal of implant therapy was concern about the surgical risk (43%) [24]. This problem can be resolved by applying IVS during implant therapy. Morino et al. compared pre- and postoperative changes in autonomic nervous system activity and salivary stress biomarkers between patients who received only local anesthesia and those who received local anesthesia plus IVS for implant placement surgery. The results showed that among patients who received local anesthesia plus IVS, the low frequency/high frequency ratio and coefficient of component variance at 1 h before surgery were significantly low, indicating a reduction in tension and anxiety [25]. The findings in the present study suggest that use of IVS during implant placement induces psychological changes in patients; therefore, it is suggested that studies similar to that of Morino et al. in patients returning for maintenance would yield good results. Eihab et al. evaluated short-term implant survival according to the implant placement site and implant diameter; the sites with the highest and lowest survival rates were the mandibular anterior region (100%) and maxillary anterior region (95.9%), respectively, and diameters of 5.0 mm and 3.5 mm were associated with the highest and lowest implant survival rates (98.72% and 94.57%, respectively) [26]. In this study, implant diameter, length, and placement site had no effect on implant survival. However, patients in the IVS group received implants with significantly larger diameters compared with those in the control group. Therefore, favorable mechanical factors might have resulted in lesser bone loss in the IVS group.
In this study, application of IVS for implant therapy improved adherence to maintenance and increased the number of additional implant placements over a 3-year period after superstructure attachment, indicating the superiority of IVS in implant therapy.
However, we will continue our investigation because studies in a larger number of patients for a longer follow-up period are essential. Moreover, this study included only healthy individuals. In the future, we will investigate the effect of IVS on implant-therapy outcomes in patients with systemic diseases.