Biomimetic fabrication and application of fibrous-like nanotubes

Dual-functions of prime-and-rinse approach with MDP primer on the performance of modified self-etch adhesive

OBJECTIVES

This study introduced the prime-and-rinse approach with an methacryloyloxydecyl dihydrogen phosphate (MDP)-containing primer to augment the performance of modified self-etch adhesives loaded with amorphous fluorinated calcium phosphate (AFCP) nanoparticles.

METHODS

The modified self-etch adhesive was acquired by adding 20 wt% AFCP nanoparticles into Clearfil S3 Bond. An experimental primer containing 15 wt% MDP was prepared. The bond performance was assessed through micro-tensile bond strength (MTBS) tests. Additionally, a single-layer collagen model and demineralized dentin were used to investigate mineralization characteristics. Cytotoxicity was evaluated using a modified transwell insert model on human dental pulp stem cells.

RESULTS

The incorporation of AFCP nanoparticles into the Clearfil S3 Bond led to a significant reduction in MTBS. While the application of MDP primer could improve the bond performance of modified Clearfil S3 Bond. The MDP primer further augmented the mineralization of single-layer collagen model and demineralized dentin induced by modified self-etched adhesive. The relative cell viability was around 100 % in all groups in the study.

CLINICAL SIGNIFICANCE

These results indicated that the prime-and-rinse approach with MDP primer not only compensated for the reduced bond strength caused by the incorporation of AFCP nanoparticles but also enhanced mineralization capabilities and maintained biocompatibility, offering a promising strategy for improving the longevity of dental restorations.

Effects of Solvents and pH Values on the Chemical Affinity of 10-Methacryloyloxydecyl Dihydrogen Phosphate toward Hydroxyapatite

This study aimed to investigate the effects of solvents and pH values on the chemical interaction between 10-methacryloyloxydecyl dihydrogen phosphate (MDP) and hydroxyapatite (HAp). The chemical affinity of MDP toward HAp dissolved in different solvents (E-MDP: 10 wt % MDP and 90 wt % ethanol; E-W-MDP₁: 10 wt % MDP, 75 wt % ethanol, and 15 wt % water; A-W-MDP: 10 wt % MDP, 75 wt % acetone, and 15 wt % water; and E-W-MDP₂: 10 wt % MDP, 45 wt % ethanol, and 45 wt % water) was investigated. The pH of E-W-MDP₂ was increased from 2.04 to 5 (E-W-MDP_2/5) and to 7 (E-W-MDP_2/7). The reaction products were characterized by Fourier transform infrared spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and nuclear magnetic resonance (NMR). XRD and NMR results revealed that no MDP-calcium salt formed in E-MDP. XRD, TGA, and XPS results indicated that MDP interacted with HAp, producing the MDP-calcium salt in all groups except E-MDP. NMR results revealed that the dicalcium salt of the MDP dimer (DCS-MD) and the MDP tripolymer (DCS-MT) and the monocalcium salt of the MDP monomer and the MDP dimer were formed in E-W-MDP₁. DCS-MD and DCS-MT were also formed in E-W-MDP₂ and A-W-MDP. In E-W-MDP_2/5 and E-W-MDP_2/7, DCS-MD was obtained. Both the solvents and pH values affect the chemical interactions between MDP and HAp and the types of reaction products formed. MDP and HAp do not form any MDP-calcium salt in pure ethanol; the structural stability of MDP-calcium salts is dependent on the solvent water content and the pH value. The ethanol/water mixture is recommended as the main solvent in an MDP-containing primer, and the ideal pH value is 2-7; if these conditions are satisfied, sufficient amounts of MDP-calcium salts with stable structures are expected to be formed, thus improving the longevity of dentin/enamel bonding.