Study On Electrophoretic Deposition And Cementogenesis In Dentin Hypersensitivity

Dentin hypersensitivity is a common dental problem.It often occurs at the cervical region and root surface of teeth.Cementum loss at these areas exposes the underneath dentin and induces dentin hypersensitivity.For the study of dentin hypersensitivity,we applied electrophoretic deposition to occlude dentinal tubules in vitro,and explored the mechanism of cementogenesis.There are three parts in this study.Part 1 Application of electrophoretic deposition to occlude dentinal tubules in vitro.Objectives:This study aims to apply electrophoretic deposition(EPD)for occlusion of dentinal tubules in vitro and investigate its effect on tubule occlusion and shear bond strength(SBS).Methods:Charged mesoporous silica nanoparticles(MSN)were synthesized and characterized through field-emission scanning electron microscopy(FESEM),transmission electron microscopy(TEM),dynamic light scattering(DLS),and Fourier transform infrared(FTIR)spectroscopy analyses.Thirty-nine sensitive dentin specimens were modeled and assigned randomly to three groups with different treatments(n = 13 each):group 1,immersion in the MSN suspension;and groups 2 and 3,anodic EPD with the specimen on the negative and positive electrode respectively.The effect of dentinal tubule occlusion was evaluated by dentin permeability test(n =10 each)and FESEM examination(n=3 each).Moreover,18 specimens were grouped(n-6 each)and treated in the same method.These specimens were used for testing SBS after employing a self-etch adhesive(single bond universal)to build one resin stick on each of them.Results:Negatively-charged MSN were synthesized and characterized as small and well-dispersed particles.After the EPD treatment(group 3),the dentinal tubules were effectively occluded by MSN,which infiltrated into the tubules at a depth of approximately 7-8 ?m and tightly associated with the tubular inwalls.SBS was not significantly different among the three groups(P>0.05).Conclusions:Synthesized MSN were deposited into dentinal tubules by EPD treatment without compromising dentin bond strength.Application of EPD is a new approach for occlusion of dentinal tubules and exhibits potential in the study of dentin hypersensitivity.Part 2 YAP promotes cementogenesis during inflammatory stimulation viasuppressing NF-?B pathwayObjectives:To investigate the role and mechanism of YAP in cementogenesis during inflammatory stimulation.Methods:Expression of YAP in OCCM cells after TNF-a stimulation was tested with Western blot.Gain-and loss-of-function experiments were performed to determine the roll of YAP in OCCM cells during TNF-a stimulation.Its effect on NF-?B pathway was evaluated through the phosphorylation and nuclear translocation of p65,dual-luciferase reporter assay,and the transcriptional level of IL6.Its effect on cementogenesis was explored with alizarin red staining and the expression of mineralization-related genes.Results:Immunofluorescence staining showed that YAP protein exited in the tissue of inflammatory model.Western blot also showed upregulated YAP in OCCM cells after TNF-a treatment.During TNF-a stimulation,overexpression of YAP inhibited NF-?B pathway and knockdown by lentivirus-delivered shRNA activated NF-?B pathway.Overexpression of YAP promoted cementogenesis of OCCM.Knockdown of YAP inhibited cementogenesis of OCCM and the effect was subsequently rescued by NF-?B inhibitor Bayl 1-7082.Conclusions:The study revealed the positive role of YAP in cementoblast mineralization during inflammatory stimulation.YAP promotes cementogenesis by suppressing NF-?B pathway.Part 3 YAP promotes cementogenesis partly via suppressing SIRT6 Objectives:To further explore the mechanism that YAP promotes cementogenesis.Methods:The effect of YAP on cementogenesis was tested with alizarin red staining and qPCR analysis of the expression of mineralization-related genes.The influence of YAP on SIRT6 expression was tested with western blot.SIRT6 overexpression in YAP overexpressing cementoblast was used to rescue the phenotype and related gene expression.Results:Alizarin red staining and qPCR analysis revealed that YAP had a positive effect on cementogenesis as reported previously.Western blot showed that YAP inhibited SIRT6 expression.Overexpression SIRT6 rescued the inhibited cementogenetic phenotype and related gene expression in YAP overexpressing cementoblast.Conclusions:The positive effect of YAP on cementogenesis is partly via suppressing SIRT6.