Immunohistochemical Evaluation of Peri-Implant Soft Tissues around Machined and Direct Metal Laser Sintered (DMLS) Healing Abutments in Humans

Background: Direct metal laser Sintering (DMLS) is an additive manufacturing technique that allows fabrication of dental implants and related components with a highly porous surface. To date, no human studies have investigated the soft tissue adhesion and presence of inflammatory infiltrate with porous DMLS healing abutments (HAs), nor have they compared these with the classic machined ones. Purpose: To evaluate the degree of cell adhesion (integrin expression) and the quantity/quality of inflammatory infiltrate, on HAs with different surfaces; full DMLS, full machined, and hybrid (half DMLS and half machined). Methods: Fifty implant patients were randomly assigned to receive one of these different Has: T1, full DMLS (11 subjects); T2, machined in the upper portion and DMLS in the lower one (10 subjects); T3, DMLS in the upper portion and machined in the lower one (19 subjects); T4, full machined (10 patients). Thirty days after placement, circular sections of soft tissues around HAs were retrieved for immunohistochemical evaluation. Results: With regard to the adhesion molecules, the samples showed different intensity of integrin expression, with a statistically significant difference (p < 0.001) between T1 and the other groups. All the samples were positive for the different clusters related to the inflammatory infiltrate (T lymphocytes, CD3; B lymphocytes, CD20; and macrophages, CD68), but a lower infiltrate was found in T1, with statistically significant differences (p < 0.001) among the groups. Conclusions: The HA surface seems to influence the degree of cell adhesion and the inflammatory infiltrate of the surrounding soft tissues

The Potential Role of a Surface-Modified Additive-Manufactured Healing Abutment on the Expression of Integrins α2, β1, αv, and β6 in the Peri-Implant Mucosa: A Preliminary Human Study

The stability of peri-implant soft tissues is essential for long-term success. Integrins play a vital role in biological processes through developing and maintaining cell interactions; however, few studies have evaluated the effects of modifications to abutment surfaces on cell adhesion across integrin expression. Therefore, this pilot study assessed the influence of different surface topographies of titanium healing abutments prepared by additive manufacturing (AM) on the gene expression levels of the integrin subunits α2, β1, αv, and β6 in the human peri-implant mucosa. Thirteen healthy adults were included. Depending on the number of required implants, the subjects were distributed in different groups as a function of healing abutment topography: group 1 (fully rough surface); group 2 (upper machined + lower rough); group 3 (rough upper surface + lower machined); group 4 (fully machined). A total of 40 samples (n = 10/group) of the peri-implant mucosa around the abutments were collected 30 days after implant placement, and subsequently, the gene expression levels were evaluated using real-time PCR. The levels of gene expression of β1-subunit integrin were upregulated for individuals receiving fully rough surface abutments compared with the other surface topographies (p < 0.05). However, the healing abutment topography did not affect the gene expression levels of the α2, αv, and β6 integrin subunits in the human peri-implant mucosa (p > 0.05). This preliminary study suggested that controlled modifications of the surface topography of titanium healing abutments produced by AM may influence the quality of the peri-implant mucosa in the early stages of the soft tissue healing process