Comparative Study of Peri‐Implant Tissues Following Flapless Placement of a One‐Piece Tissue‐Level Implant Versus Open‐Flap Placement of a Two‐Piece Bone‐Level Implant in a Canine Model

Purpose The purpose of this study is to test the hypothesis that the placement of a minimally invasive implant (MII, one‐piece tissue‐level implant) using a flapless/subcrestal protocol provides a better quality of peri‐implant tissues compared to a reference implant (RI, two‐piece bone‐level implant) placed with an open‐flap/crestal protocol in a canine model. Methods In this in vivo preclinical study, two types of implants were placed in the mandibula. Clinical, radiological, and histomorphometry measurements were performed at implant placement (T0), at healing abutment placement (T + 8W), and at the end of the study (T + 16W). Results Three osseointegration failures occurred, all in the MII group, reducing sample sizes for that group. A significant increase in keratinized tissue height was observed around the MII (3.00 mm ± 1.04 vs 3.68 mm ± 0.63; p < 0.001), and a significant decrease was observed for the RI (3.47 mm ± 0.74 vs 2.07 mm ± 0.40; p < 0.05) between T0 and T + 16W. The biological width, in mesiodistal sections, was significantly greater around the MII (mean ± standard deviation [SD] peri‐implant mucosa [PM]‐fBIC distances: 3680.5 µm ± 629.2) than for the RI (2065.5 µm ± 395.1, p < 0.001). No significant difference was observed in buccolingual sections. Bone remodeling, in mesiodistal sections, around the MII (mean ± SD implant shoulder [IS]‐bone crest [BC] 890.4 µm ± 759.2) was higher around the IS and was significantly greater around the RI (mean ± SD IS‐BC −283.4 µm ± 285.3, p < 0.001), for which significant bone resorption was observed. Conclusion In this canine model and under the specific study conditions, the MII was associated with distinct patterns of bone remodeling and greater epithelial–connective tissue dimensions in mesiodistal sections. These results suggest a favorable soft tissue environment around the MII. It would be interesting to confirm these results in humans, particularly the elderly and medically compromised patients for whom the atraumatic flapless surgical protocol seems particularly suitable.