Radiographic Evaluation of Marginal Bone Level Around Implants with Different Neck Designs After 1 Year

Purpose: To evaluate the influence of macro- and microstructure of the implant surface at the marginal bone level after functional loading. Materials and Methods: Sixty-eight patients were randomly assigned to 1 of 3 groups. The first group received 35 implants with a machined neck (Ankylos); the second group, 34 implants with a rough-surfaced neck (Stage 1); and the third, 38 implants with a rough-surfaced neck with microthreads (Oneplant). Clinical and radiographic examinations were conducted at baseline (implant loading) and 3, 6, and 12 months postloading. Two-way repeated analysis of variance (ANOVA) was used to test the significance of marginal bone change of each tested group at baseline, 3, 6, and 12 month follow-ups and 1-way ANOVA was also used to compare the bone loss of each time interval within the same implant group (P .05). Results: At 12 months, significant differences were noted in the amount of alveolar bone loss recorded for the 3 groups (P .05). The group with the rough-surfaced microthreaded neck had a mean crestal bone loss of 0.18 ± 0.16 mm; the group with the rough-surfaced neck, 0.76 ± 0.21 mm; and the group with the machined neck, 1.32 ± 0.27 mm. In the rough-surfaced group and the rough-surfaced microthreaded group, no statistically significant changes were observed after 3 months, whereas the machined-surface group showed significant bone loss for every interval (P .05). Discussion: To minimize marginal bone loss, in addition to the use of a rough surface at the marginal bone level, a macroscopic modification such as the addition of microthreads could be recommended. A rough surface and microthreads at the implant neck not only reduce crestal bone loss but also help with early biomechanical adaptation against loading in comparison to the machined neck design. Conclusion: A rough surface with microthreads at the implant neck was the most effective design to maintain the marginal bone level against functional loading. (Comparative Cohort) Keywords: machined neck, marginal bone level, microthreads, rough surface