Immediate and late analysis of dental pulp stem cells viability after indirect exposition to alternative in-office bleaching strategies.

OBJECTIVES: To evaluate human dental pulp stem cell viability and capacity to recover from experimental dental bleaching techniques. MATERIAL AND METHODS: Enamel/dentin disks adapted to trans-wells were positioned on previously cultivated dental pulp stem cells. Bleaching gels containing 35, 17.5, 10, and 8 % hydrogen peroxide (H2O2) were applied one or three times (each application lasting 15 min) on enamel. Cell viability (MTT assay) and morphology (SEM) were evaluated immediately (T1) or 72 h (T2) post-bleaching. RESULTS: The 35 % H2O2 gel promoted intense reduction in viability (93-97 %) and morphological alterations of the cells at T1, irrespective of frequency of application, with absence or limited capacity for recovery being observed at T2. The other bleaching gels presented significant lower toxicity when compared with the 35 % H2O2 gel, in a time/concentration fashion. In T1, no significant difference was observed between the negative control (without bleaching) and the 8 and 10 % H2O2 gels applied on enamel for 15 min, in which the cells presented elevated viability and morphology similar to the negative control at T2. CONCLUSIONS: Bleaching gels with 8 and 10 % H2O2 in their composition cause limited immediate toxic effect on pulp stem cells, which recover their viability 3 days after treatment. CLINICAL RELEVANCE: This study presents proposals for in-office dental bleaching to be performed with limited aggressive effect on dental pulp stem cells. Therefore, we are able to offer interesting clinical alternatives for bleaching vital teeth, under professional supervision, maintaining the integrity and reparative capacity of pulp-dentin complex.