The Impact Of Tray-based Bioactive Glasses Application On Dentine Remineralization And Pulp Permeability

Dentine hypersensitivity(DH)is a common clinical dental symptom,characterized by distinctive short,sharp pain arising from exposed dentine reacting to external stimuli,which typically are thermal,evaporative,tactile,osmotic,or chemical.Dentine hypersensitivity(DH)is a common clinical dental problem,which affect approximately 8%-30%adults and 84%patients post periodontal surgery.Bleaching hypersensitivity(BH)is frequently occurred during or after teeth bleaching process.Teeth bleaching is a common procedure in cosmetic dentistry,bleaching methods generally use peroxide compounds applied directly to the teeth.Whitening effects are exerted by penetrating dental enamel into dentine and oxidizing the stains.As many as 66%patients complain pain and hypersensitivity after Teeth bleaching procedure.There are different theories on pathological mechanism of DH and BH.The generally accepted concept for the physiological cause of DH and BH is Hydrodynamic theory.This concept states that exposed,open dentinal tubules at the tooth surface permit dentinal fluid movement along the tubules which in turn,excites the nerve endings in the sub-odontoblastic nerve in the dental pulp,so causing acute discomfort.By hydrodynamic theory,the occlusion of dentine tubules clinically reduce or stop the flow of fluid in dentine to prevent pain.Occlusion is an effective method in hypersensitive treatment.Bioactive glasses(BGs)are highly biocompatible materials containing calcium sodium phosphosilicate as their active ingredient.In Physiological environment,BGs could release calcium and phosphorus ions and form phosphosilicate remineralization deposits on the surface of teeth which occlude dentine tubules and reduce dentine hypersensitivity.So far,BGs are mostly used by smearing application locally.In our study,we put individualized transparent tray and BGs desensitizers together,both applied to make the best of its compatibility with teeth and support to BGs desensitizers.So that BGs desensitizers could have sufficient contacting time and higherconcentration,which might be more effective in treatment of DH and BH.In the study,in vitro model was used simulate clinical condition,by smearing and transparent tray BGs desensitizers application separately to the surface of DH teeth samples and stained ex vivo teeth.Comparisons have been made on the occlusion effects and composition of deposits in the two samples by measurement of FESEM(Field Emission Scanning Electron Microscopy)and EDX(Energy Dispersive X-ray Spectrum).We also compared the impact of hydrogen peroxide penetration into the pulp chamber with two ways of treatment.Our study results might provide the new methods for the clinical application of BGs desensitizers in future.Part I In Vitro Evaluation of Dentin Desensitizing by Two Different Application Methods of Bioactive GlassesObjective:The aim of this study was to evaluate the influence of in vitro smearing and transparent-tray application of BGs desensitizers on dentine tubules during short period.To provide evidence and reference for the enhancement of BGs desensitizers treatment.Methods:56 Dentin slices were randomly divided into 7 groups with different treating method and duration:smearing 1?3?7day group(A1?A2?A3),transparent-tray method 1?3?7day group(B1?B2?B3)and negative control group.Occlusion effect and remineralization depth were observed on dentinal tubule orifice in each group via FESEM and surface mineral content disparity were analyzed of each dentin slices after the two different treatments by EDX.Result:FESEM observation showed the presence of sound occlusion of dentin tubules in both smearing and transparent-tray groups.Evident mineral deposition was observed inside the dentine tubules.Dentine tubules exposure rates are as follows:A1(6.29±1.18)%,A2(3.40±0.84)%,A3(1.23±0.43)%,Bl(5.31±0.97)%,B2(1.4±0.30)%and B3(0.36±0.15)%respectively.No significantly different was found in exposure rates between A1 and B1,while significantly different exists between A2 and B2,A3 and B3.In control group,dentine tubule orifice was opened with clear boundary,dentine tubules exposure rate was(19.11±1.27)%.The EDX data demonstrated that there were no differences in resulting Ca/P ratio(P=0.77).Conclusion:Transparent-tray application of BGs desensitizer method could significantly improve occlusion of dentin tubules in a short period compared with smearing application.Part ? The Impact of Tray-based Bioactive Glasses Application on Pulp PermeabilityObjectives:Prior to the use of nano BGs desensitizers in teeth bleaching operation,observe the content of H2O2 in dentine pulp with or without the application of desensitizers by smearing method or transparent tray.Methods:60 dentin disks were collected from human first molars and divided into 6 groups.Group A:without desensitizing treatment,soak the crown end of the disks into deionized water for 30minutes.Group B:without desensitizing treatment,soak the crown end of the disks into 30%H2O2 for 30minutes;Group C:smearing application of BGs desensitizers for 2min,twice/day,after soaking disks into artificial saliva(AS)for 24 hours,put the crown end of the disks into 30%H2O2 for 30minutes;Group D:transparent tray application of BGs desensitizers 1 hour,after soaking disks into artificial saliva for 24 hours,put the crown end of the disks into 30%H2O2 for 30minutes;Group E:smearing application of BGs d.esensitizers for 2min,twice/day,after soaking disks into artificial saliva for 24 hours,put the crown end of the disk into deionized water for 30minutes;Group F:transparent tray application of BGs desensitizers for 1 hour,after soaking disks into artificial saliva for 24 hours,put the crown end of the disk into deionized water for 30minutes.Extract the fluid in dentin pulp of each group,add horseradish peroxidase(HRP),crystal violet and react,calculate the content of H2O2 by the measurement of absorbance with UV-visspectrophotometry.Results:The content of H2O2 in each group were:0?g(A group),21.149?g±0.489?g(B group),9.813?g±0.426?g(C group),4.065?g±0.268?g(D group),0?g(E group),0?g(F group).ANOVA results indicated that statistically significant difference existed between B,C and D(F=459.748,P<0.05).Multiple comparison results indicated that significant difference also existed between B,C and D.Conclusion:The application of BGs desensitizers could reduce the penetration of H2O2 into dentin pulp so as to reduce the occurrence of BH during or post bleaching operation.The effects could be enhanced when applied in combination with transparent-tray.