Effect of implant neck design on primary and secondary implant stability in the posterior maxilla: A prospective randomized controlled study

Objective: To compare the early changes in implant stability of implants with different neck design during the first 3 months of healing in the posterior maxilla. Materials and methods: Patients were randomized to receive triangular neck implant (test), or round neck implant (control). Resonance frequency analysis (ISQ) measurements were obtained at surgery and at 2, 4, 7, 14, 21, 28, 45, 60, and 90 days following implant placement. Non-parametric statistic was used for data analysis. Results: Thirty-two patients were included (17 test and 15 controls). Initial ISQ values of the test implants were high (mean: 68.4, SD = 8.4) and increased over time (mean: 74.4, SD = 6.0). Control implants presented a statistically significant higher initial ISQ value at implant placement (mean: 76.9, SD = 8.7), which was maintained over the healing period (mean: 77.6, SD = 3.6) with no significant changes between time intervals. After 6 weeks of healing, both implants displayed comparable ISQ values with no differences between the groups. All implants exhibited a decrease in stability on days 2 and 21 post-placement. All roundneck implants used, and 82% of the triangularneck implants showed initial ISQ values above the suggested threshold for immediate loading (>60). Conclusions: Implant neck design plays a role in implant primary stability in the posterior maxilla. Both implants show high primary stability, with significantly higher values for the round neck. However, these differences disappeared after 6 weeks of healing. While primary implant stability is partially governed by implant neck design, the role of this result is negligible for the achievement of secondary stability.