Efficacy Of Mesoporous Silica Nanoparticles Carrying Calcium And Phosphorus On Dentinal Tubule Occlusion And Indirect Pulp Capping

Objective:Maintaining long-term effect of sealing dental tubules to reduce dentin hypersensitivity remains an unsolved problem in dental clinics.In addition to physical therapy,chemical treatment involving the formation of insoluble precipitations to seal dentinal tubules has also been used.At present,the commonly used tubule-occluding material in clinic can not penetrate into the dentinal tubules in depth,so they can not meet the challenges of daily acid corrosion and friction.Phosphate precipitation has shown some potential for the sealing of dentinal tubules,as dentin is mostly composed of calcium and phosphate complex.Calcium phosphate precipitation material can play a dual role in the initial mechanical sealing of dentinal tubules and long-term remineralization.Sealing dentinal tubules,isolating external stimuli is also one of the clinical requirements for indirect pulp capping agents.Therefore,how to make phosphate precipitation penetrate into dentinal tubules to play a sealing role has become the focus of attention of many scholars.Mesoporous silica nanoparticles have gained a significant interest as potential therapeutic and diagnostic medical agents due to their tunable particle size,stable framework,uniform pore size,high surface area,biocompatibility and unique porous structure.It has also become a new material in the field of dentin hypersensitivity treatment.In this study,we conjugated either Ca²⁺or PO₄^3-with mesoporous silica nanoparticles（MSNs）,which resulted in the formation of a new tubule-occluding material(Ca²⁺/PO₄^3-@MSNs).NovaMin,a commonly used desensitizer in clinic,was used as a control to evaluate the ability of new materials with appropriate water-powder ratio to resist simulated oral daily corrosion and friction.In addition,we speculate that because both calcium and phosphorus are beneficial to mineralization,Ca²⁺/PO₄^3-@MSNs can also be used as indirect pulp capping agents to protect dental pulp tissue and induce human dental pulp stem cells to differentiate into odontoblasts.Whether Ca²⁺/PO₄^3-@MSNs can resist acid corrosion and friction in simulated daily oral environment and whether Ca²⁺/PO₄^3-@MSNs can induce the proliferation,migration and odontogenic differentiation of hDPSCs.Methods:1.MSNs were fabricated and observed by transmission electron microscopy.The suitable diameter of MSNs was selected.After carrying calcium and phosphorus ions on MSNs,the size and morphology of the particles were observed by scanning electron microscopy,and the elemental composition of the particles was determined by X-ray energy dispersive spectrometry.2.Ca²⁺/PO₄^3-@MSNs were mixed with deionized water at five different concentrations and coated on dentin discs.The occlusion rate of dentin tubules in dentin discs treated with different water-powder ratios were calculated by SEM and image-Pro Plus 6.0 image analysis software.The best water-powder ratio was screened out.Dentin discs were treated with the best proportion of water-powder ratio of Ca²⁺/PO₄^3-@MSNs,and compared with those treated with NovaMin in simulated oral acid corrosion and friction.3.The cytotoxicity was tested according to GB/T16886.12-2017,and the highest concentration of Ca²⁺/PO₄^3-@MSNs in vivo was screened.CCK-8 method was used to detect the effects of Ca²⁺/PO₄^3-@MSNs at different concentrations on the proliferation of hDPSCs.The optimal concentration was used to culture cells.Real-time PCR was used to detect the expression of differentiated genes.Cell scratch test was used to detect the migration ability of hDPSCs stimulated by appropriate concentration of Ca²⁺/PO₄^3-@MSNs.Results:1.Under TEM,MSN has uniform shape and size,uniform pore size and moderate particle aggregation.2.Experiments show that the closure effect of dentinal tubules at Ca²⁺@MSNs:PO₄^3-@MSNs:H₂O=0.015 g:0.015 g:150 uL is the best,which can reach 97.6%.Compared with Novartis,Ca²⁺/PO₄^3-@MSNs can better resist the daily corrosion and friction.CCK-8 showed that Ca²⁺/PO₄^3-@MSNs with a concentration of 0.7mg/ml had the ability to promote the proliferation of the cells,but higher concentration of Ca²⁺/PO₄^3-@MSNs had toxic effects on the cells.Scratch experiments showed that Ca²⁺/PO₄^3-@MSNs had the ability to promote the migration of hDPSCs.The results of PCR showed that Ca²⁺/PO₄^3-@MSNs had the ability to promote dental differentiation of hDPSCs,and the related molecular mechanisms need to be clarified.Conclusions:To sum up,the experiments confirmed that Ca²⁺/PO₄^3-@MSNs with appropriate water-powder ratio could resist the daily oral erosion and wear better than NovaMin,and a certain concentration of Ca²⁺/PO₄^3-@MSNs could promote the proliferation,migration and odontogenic differentiation of hDPSCs to a certain extent.This laid a theoretical foundation for the application of Ca²⁺/PO₄^3-@MSNs as a new material in clinical practice.