| Dentin hypersensitivity (DH) is a relatively common dental clinicalcondition in permanent teeth. Dentin hypersensitivity is characterized by shortsharp pain arising from exposed dentin in response to stimuli typically thermal,evaporative, tactile, osmotic or chemical and which cannot be ascribed to anyother form of dental defect or pathology.With the constantly development in modern oral medicine research and theprogress of oral health care in the general population, there has been a positivetrend of reduction in tooth loss among adults in recent years. At the same time,there is an increasing incidence of dentin hypersensitivity caused by dentinabrasion, erosion or corrosion. Meanwhile, esthetics restorations are widely usedin the modern dentistry. Therefore, dentin exposed by enamel loss after toothpreparation of full crown also becomes an important reason for dentinhypersensitivity.Nowadays, the most widely accepted mechanism of dentin hypersensitivityis the hydrodynamic theory proposed by Br nnstr m. Thus, two main methods are used in the treatment of dentin hypersensitivity: tubular occlusion andblockage of nerve activity by means of direct ionic diffusion, increasing theconcentration of potassium ions acting on the pulpal nerve sensorial activity.Desensitizing agents have been classified according to their mode ofaction：nerve desensitization, protein precipitation, plugging dentinal tubules,biomimetic dentin desensitizer, dentin adhesive sealers.The ideal dentin desensitizing agent should not only have good biologicalsafety, simple clinical operation mode, the superior treatment effect, but alsoshould have a durable effect to resist the oral environmental temperature changeand oral mechanical abrasion, so as to achieve a persistent desensitization effect.Also, when using desensitizing agent to prevent the post-operativehypersensitivity, we should not only prevent it from affecting crowns’ retention,but must understand its effects on bond strength of dentin adhesives. There arevarious of desensitizers and dentin adhesives in clinical treatment. They havedifferent chemical or physical properties. Whether the use of desensitizing agentwould affect the bond strength of dentin adhesives still need further research.In this in vitro study, we built the hypersensitive dentin model andpost-operative dentin model, to evaluate the sealing effects and durability onexposed tubule by three different dentin desensitizers and to evaluate the sealingeffects and the bond strength of dentin adhesives after using three differentdentin desensitizers on post-operative dentin. The result of this study couldprovide some important references for clinical use of dentin desensitizing agent.The whole studies were divided into three parts:Part one: The sealing effects and durability of three desensitizers onhypersensitive dentin1. As to the three desensitizers, the hypersensitive dentin model was built to evaluate their sealing effects on exposed tubule by SEM observation and dentinpermeability analysis. All of them could significantly reduce the dentinpermeability. The sealing effects on exposed tubule of three groups were in theorder of Hybrid Coat> Gluma> Green or (P <0.05). The dentin permeabilityreduced by99.42%,61.61%and42.03%after treated by Hybrid Coat, Glumaand Green or respectively.2. Test specimens of three groups treated by desensitizers were subjected toaging treatment with5000times thermal cycling and toothbrush abrasion, andthen dentin permeability was measured to evaluate the sealing durability of thesethree desensitizers on exposed tubule. The sealing durability of three groupswere different. The dentin permeability for Hybrid Coat and Gluma group didnot show significant change after aging treatment（P>0.05）, while the dentinpermeability of Green or group（7.79±0.89μL/min） was significantly higherafter aging treatment than that before the aging treatment（5.23±0.95μL/min）（P <0.05）.Part two: Effect of three desensitizers on post-operative dentin occlusion andbond strength of total-etch and self-etch adhesives.3. The post-operative dentin model was built to evaluate the sealing effectsof the three desensitizers on post-operative dentin by SEM and methylene blue.All of three desensitizers could reduce the dentin permeability significantly.Their sealing effects on post-operative dentin were different. Hybrid Coatexhibited the best sealing ability, then turned to Gluma and Green or. Thedeepest dye penetration of Hybrid Coat group and Gluma group were1.4mmand that of Green or group was2.3mm.4. The influences of three desensitizers on the bonding efficiency oftotal-etch and self-etch adhesives were evaluated with the micro-tensile bond strength for Green or group was significantly lower than the other two groups（P <0.05）. Hybrid Coat and Gluma had no effect on bond strength oftotal-etch and self-etch adhesives（P>0.05）．While the bond strength oftotal-etch and self-etch adhesives（13.39±4.67MPa;13.44±5.89MPa）wassignificantly higher than that after treated by Green or（10.48±4.32MPa;8.39±4.51MPa）（P <0.05）．... |
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