Efficacy of Ca 2+ - or PO4 3− -conjugated mesoporous silica nanoparticles on dentinal tubule occlusion: an in-vitro assessment

Background: Maintaining a long-term biological effect of dental materials on dentinal tubule occlusion is one of the great technical challenges in dental clinics. In addition to physical treatment, chemical treatment to produce insoluble precipitates to seal dentinal tubules has been used. As dentin is mostly composed of calcium and phosphate complexes, in this study, we have developed a novel tubule-occluding material [Ca2+/PO43-@mesoporous silica nanoparticles (MSNs)] by separately conjugating either Ca2+ or PO43- with MSNs. Methods: The shape and structure of the MSNs were examined using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The surface morphology and chemical compositions of Ca2+@MSNs/PO43-@MSNs and Ca2+/PO43-@MSNs were examined using SEM and X-ray fluorescence (XRF). The element distribution of Ca2+/PO43-@MSNs was detected using energy dispersive spectrometer (EDS). The sustained release ability of Ca2+@MSNs/PO43-@MSNs was detected using inductively coupled plasma atomic emission spectrometry (ICP-AES). The efficacy of Ca2+/PO43-@MSNs on dentinal tubule sealing was evaluated using SEM, and the results were analyzed by Image-Pro software to determine the best water-powder ratio. We also compared the sealing efficacy between Ca2+/PO43-@MSNs and NovaMin, which is currently used in clinics, under the simulated conditions of oral acidic corrosion and mechanical friction. Results: Ca2+/PO43-@MSNs are a new type of tubule-occluding material with sustained release properties. The ratio of Ca2+@MSNs: PO43-@MSNs: H2O =0.015 g: 0.015 g: 150 µL exhibited an excellent sealing effect on dentinal tubules as well as resistance to oral acid corrosion and daily oral friction. Conclusions: The novel dental material Ca2+/PO43-@MSNs demonstrates potential long-term effectiveness in sealing dentinal tubules and reducing dentin sensitivity, which is one of the most important problems in dental clinics.