Antioxidant, Antibacterial, and Dental Bond Strength Performance of Picea orientalis Resin

The objective of this study was to evaluate the antioxidant and antibacterial profiles of Picea orientalis (Oriental spruce) resin extracts collected from three distinct geographical sites (Artvin, Borçka, and Çaykara) within the Eastern Black Sea region of Türkiye. Additionally, it aimed to assess the viability of these extracts as natural antibacterial agents against cariogenic pathogens and to determine their subsequent effect on dental bond strength performance. Quantitative phytochemical analysis of the ethanolic extracts included the determination of total phenolic content, coupled with individual phenolic profiling by HPLC-PDA. The antioxidant potential was assessed through DPPH and FRAP assays. Additionally, the antibacterial activity against a panel of oral and systemic pathogens was evaluated using agar well diffusion. Furthermore, to evaluate mechanical performance, composite bond strengths were tested on 180 dentin specimens using both self-etch and etch-and-rinse adhesive strategies, following cavity pre-treatment with a control, chlorhexidine, or the resin extracts. The results revealed that the resin from the Artvin region exhibited the highest phenolic content, characterized by an abundance of trans-cinnamic, caffeic, and ferulic acids, which correlated with their superior antioxidant capacity. Furthermore, while the extracts demonstrated potent inhibitory effects against Staphylococcus aureus, their antibacterial activity against Streptococcus mutans was found to be comparatively moderate. In bond strength evaluations, the non-aged control group exhibited the highest values (p = 0.000); however, no statistically significant difference was observed between the chlorhexidine and resin extract groups (p > 0.05). Consequently, the phenolic-rich P. orientalis resin represents a promising natural antibacterial alternative for dental applications.