Histological and Immunohistochemical Analysis of Peri-implant Tissue Regeneration at the Interface of Prosthetic Abutments Treated with Anodizing: A Prospective, Randomized Controlled Clinical Trial on the Early Postoperative Period

Objectives: This clinical trial aimed to assess the effects of anodized prosthetic abutments versus machined abutments on peri-implant connective tissue. Materials and Methods: Following dental implant placement and osseointegration, custom healing abutments with machined surfaces (G1) and anodized surface treatment (G2) were attached to 28 dental implants. After a soft tissue healing period of approximately 30 days (±7 days), 5 mm circular biopsies were taken from the peri-implant tissue and the area adjacent to the prosthetic abutment. Histological analysis was conducted on the stained specimens using hematoxylin- eosin, focusing on parameters such as vascular proliferation, the presence of polymorphonuclear and mononuclear cells, collagen fibrils, and re-epithelialization. A grading scale from 0 to 3 evaluated the extent of the inflammatory response. Masson’s trichrome staining was used to analyze collagen fiber presence and organization, while immunohistochemical staining assessed the expression of beta-catenin and CD34. The prosthetic abutments were evaluated through electron microscopy and three-dimensional roughness analysis. Results: Histological findings revealed that peri-implant tissue adjacent to anodized surfaces exhibited epithelial stratification and a parakeratin layer in the lamina propria. Both groups displayed a typical mononuclear lymphocytic inflammatory infiltrate, but the intensity was significantly higher adjacent to the machined abutment (p<0.05). Quantification of blood vessels indicated increased immunopositivity for CD34 in G2 compared to G1 (p<0.05). Immunolabeling of beta-catenin was detected in the epithelial tissue, showing weak intensity in G1 and strong intensity in G2. The average surface roughness (Ra) measurements were determined to be 0.097 (0.006) µm for G1 and 0.182 (0.008) µm for G2. Conclusion: Anodized surfaces are promising and exhibit beneficial effects on peri-implant tissue healing. They play an important role in preserving the epithelial mucosal integrity and functionality near the prosthetic abutment, thereby potentially minimizing the risks of mucositis, peri-implantitis, and implant failure.