Influence of implant neck surface and placement depth on crestal bone changes and soft tissue dimensions around platform-switched implants: A histologic study in dogs

Abstract

Objectives: To analyse bone remodelling and peri-implant soft tissues around platform-switching implants with and without a machined collar placed at different levels in relation to bone crest. Material and Methods: All mandibular premolars and the first molars were extracted in five dogs. At 6 months, six implants with and without a machined neck (MACH and GBAE implants, respectively) were randomly inserted in each hemimandible positioning the implant–abutment interface in either a supracrestal (+1.5 mm), equicrestal, or subcrestal (−1.5 mm) position. After 6 months, animals were killed for histomorphometric analysis. Results: When net bone loss (primary outcome variable) was compared between MACH and GBAE groups, the multivariable regression analysis revealed no significant differences between implants inserted at the same vertical position. The dimensions of the peri-implant mucosa were greater in MACH implants compared with GBAE implants; however, these differences failed to reach statistical significance. Regarding the number of inflammatory cells and collagen fibre orientation, no statistically significant differences were found between MACH and GBAE groups. Conclusions: The surface treatment of the implant neck does not seem to have an influence on net bone loss, and there were no statistically significant differences in the peri-implant soft tissues between platform-switching implants with and without a machined neck.