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

PURPOSE: 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 biopsy samples were taken from the peri-implant tissue and the area adjacent to the prosthetic abutment. Histologic analysis was conducted on the stained specimens using hematoxylin-eosin (H&E), focusing on parameters such as vascular proliferation as well as the presence of polymorphonuclear and mononuclear cells, collagen fibrils, and reepithelialization. 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 (β-catenin) and Cluster of Differentiation 34 (CD34). The prosthetic abutments were evaluated through scanning electron microscopy and 3D roughness analysis. RESULTS: Histologic 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 < .05). Quantification of blood vessels indicated increased immunopositivity for CD34 in G2 compared to G1 (P < .05). Immunolabeling of β-catenin was detected in the epithelial tissue, showing weak intensity in G1 and strong intensity in G2. The average surface roughness measurements were determined to be 0.097 ± 0.006 μm for G1 and 0.182 ± 0.008 μm for G2. CONCLUSIONS: Anodized surfaces are a promising treatment option 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.