A Comparative Study of Stainless Steel and PEEK TiO2 Composite: Effects on Cell Behavior and Bacterial Adhesion in Pediatric Crowns

Dental materials are well-established, with stainless steel 316L (SS) still being a common choice for components such as pediatric crowns and abutments. However, SS has some drawbacks, particularly in terms of mechanical properties and, more importantly, aesthetics, due to its metallic gray color. In this sense, PEEK (polyetheretherketone) has emerged as a promising material for dental applications, combining good mechanical properties with improved aesthetic features. This study compared the cytocompatibility of PEEK TiO2 composite and SS using human fetal osteoblasts (hFOB) and human gingival fibroblasts (HGF). Cytocompatibility was evaluated over 1–7 days through metabolic activity and alkaline phosphatase (ALP) assays. Additionally, bacterial adhesion was assessed using Staphylococcus aureus and Pseudomonas aeruginosa in both monoculture and co-culture. The results showed that both materials were non-cytotoxic and supported cell growth. Notably, after 7 days of culture, PEEK TiO2 surfaces promoted approximately 7% higher ALP activity than stainless steel, demonstrating a significantly enhanced osteogenic response (p < 0.01). Moreover, at day 7, PEEK TiO2 promoted ~25% higher metabolic activity in HGF cells compared to SS. Regarding the bacterial adhesion, it was consistently low in PEEK TiO2 for both S. aureus and P. aeruginosa, with a marked reduction (~50%) observed for P. aeruginosa under co-culture conditions. PEEK TiO2 demonstrated enhanced biological performance and lower bacterial adhesion compared with SS, highlighting its potential as a biocompatible and aesthetically promising option for dental applications, including pediatric crowns.