Comparison of push-out bond strength and Si Qⁿ species distribution in blood-contaminated calcium silicate cement

Calcium silicate-based cements (CSCs) play a pivotal role in endodontic applications due to their favorable properties. This study investigates how blood contamination, a common clinical challenge during endodontic procedures, affects the bonding performance and hydration of CSCs. Tooth specimens were filled with four CSC-containing products (ProRoot MTA: PM, Endocem MTA: EC, iRoot BP Plus: IB, and TheraCal LC: TC) and placed in either distilled water or blood for 7 days at 37 ℃. The push-out test and evaluations using an inverted microscope and scanning electron microscope (SEM) were performed to measure the bond strength and fracture mode. Energy-dispersive X-ray spectroscopy (EDS) was used to measure the elemental composition and the Ca/Si ratio. ²⁹Si magic angle spinning nuclear magnetic resonance spectroscopy (²⁹Si MAS NMR) analysis was conducted to investigate the structures of the calcium silicate, and the mean silicate length (MCL) was calculated. Blood contamination significantly reduced bond strength for PM and increased bond strength for IB; no significant changes were observed with EC or TC. Blood contamination increased the Ca/Si ratio of each specimen, which was associated with decreased hydration and MCL values. It also influenced cohesive, mixed, and adhesive fractures among different groups. Blood contamination impaired the mechanical reliability of most hydration-dependent CSCs due to disrupted silicate polymerization, with the exception of IB, which exhibited an anomalous increase in push-out bond strength. From a clinical standpoint, these findings highlight the importance of hemostasis before CSC placement and suggest that future CSC formulations should improve resistance to blood contamination to enhance patient care.