Abstract: Objective Prior to the use of nano-BGs desensitizers in teeth bleaching operation, to observe the content of H2O2 in dentine pulp with or without the application of desensitizers by smearing method or transparent tray. Methods: 48 dentin disks were collected from human first molars and divided into 6 groups. Group A: without desensitizing treatment, the crown ends of the disks were soaked into deionized water for 30minutes. Group B：without desensitizing treatment, the crown ends of the disks were soaked 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, the crown ends of the disks were put into 30% H2O2 for 30minutes; Group D: transparent tray application of BGs desensitizers 1 hour, after soaking disks into artificial saliva for 24 hours, the crown end of the disks were put into 30% H2O2 for 30minutes; Group E: smearing application of BGs desensitizers for 2min, twice/day, after soaking disks into artificial saliva for 24 hours, the crown ends of the disk were put 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, the crown ends of the disk were put into deionized water for 30minutes. Tthe fluid in dentin pulp of each group was extracted and the content of H2O2 was calculated by the measurement of absorbance with UV-visspectrophotometry. Results: The contents of H2O2 in each group were: 0μg (A group)，21.149μg± 0.489μg (B group)， 9.813μg ±0.426μg(C group)，4.065μg ±0.268 μg( D group), 0μg( E group)，0μg( 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 can reduce the penetration of H2O2 into dentin pulp so as to reduce the occurrence of BH during or post bleaching operation. The effects can be enhanced when applied in combination with transparent-tray.

Key words: Bioactive glasses, transparent ray, desensitizer, bleaching, pulp permeability