Preparation and characterization of biomineralizing dentin bonding primer based on bioactive amphiphilic raspberry-like nanoparticles.

Background: Incomplete resin coverage of demineralized collagen can compromise dentin bond durability. This study developed a biomineralizing dentin bonding primer incorporating bioactive amphiphilic raspberry-like nanoparticles (BRPs) to enhance biomineralization and dentin bond strength.

Methods: BRPs were characterized using scanning electron microscopy (SEM) and nitrogen (N) adsorption experiments. The ions release from BRPs was measured using inductively coupled plasma mass spectrometry (ICP-MS), while the mineralization was evaluated using SEM and X-ray diffraction (XRD). Subsequently, an etch-and-rinse bonding system was prepared, with primer containing 1%, 5%, or 10% BRPs (w/w). XRD and SEM assessed the biomineralization of each primer group after one-month immersion in simulated body fluid (SBF). Then, 48 dentin plane samples were prepared from extracted non-carious human third molars and bonded with each primer. Stick-shaped samples (n = 30 for each group) were fabricated to evaluate the micro-tensile bond strength (µTBS) after 24 h and 6 months of aging. Degree of conversion (DC) was analyzed via attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR).

Results: BRPs (~ 100 nm) released Ca and SiO in SBF, with surface areas of 83.19 ± 0.52 m/g. After SBF immersion, SEM detected the formation of mineral clusters on BRPs, and XRD analysis confirmed the presence of distinct characteristic peaks corresponding to hydroxyapatite (HAP). Regarding the mineralization of primers, only 5% BRPs-Primer and 10% BRPs-Primer formed needle-like mineral clusters, with distinct HAP characteristic peaks. For the 24-h µTBS, the 1% and 5% BRPs-Primers were comparable to Control-Primer (P > 0.05), but 10% BRPs-Primer showed a significant reduction (P < 0.05). After 6-month aging, 5% BRPs-Primer maintained µTBS compared to its respective 24-h measurements (P > 0.05), whereas µTBS significantly declined in both Control-Primer and 1% BRPs-Primer (P < 0.05). The 5% BRPs-Primer also exhibited a comparable DC to the Control-Primer (P > 0.05), and showed good nanoparticle dispersion and effective penetration into dentinal tubules.

Conclusion: BRPs demonstrated superior mineralization ability. Incorporating 5% BRPs into dentin primer achieved effective biomineralization, excellent initial bond strength, and long-term bond stability after 6-month aging.