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Responses of Human Dental Pulp Cells after Application of a Low-concentration Bleaching Gel to Enamel
Archives of Oral Biology
Published Online: June 20, 2015
to evaluate the effect of a 17.5% H2O2 gel on the odontoblastic differentiation capability of human dental pulp cells (HDPCs).
bleaching gel was applied for 45, 15, or 5 minutes to enamel/dentin
discs adapted to transwells, positioned over previously cultured HDPCs.
In the control group, no treatment was performed on the discs.
Immediately after samples were bleached, the cell viability (MTT assay)
and death (Live/Dead assay) as well as the mRNA gene expression of
inflammatory mediators (TNFα, IL-1β, IL-6, and COX-2; real-time PCR)
were evaluated. The mRNA gene expression of odontoblastic markers
(DMP-1, DSPP, and ALP) and mineralized nodule deposition (alizarin red)
were assessed at 7, 14, and 21 days post-bleaching. The amount of H2O2
in contact with cells was quantified. Data were evaluated by
Kruskal-Wallis and Mann-Whitney tests (α = 5%).
cell viability reduction and cell death were observed for bleached
groups relative to control in a time-dependent fashion. Also,
significant overexpression of all inflammatory mediators tested occurred
in the 45- and 15-minute groups. In the bleached groups, the expression
of ALP, DMP-1, and DSPP and the deposition of mineralized nodules were
reduced in comparison with those in the control group, at the initial
periods (7 and 14 days). However, the 15- and 5-minute groups reached
values similar to those in the control group at the 21-day period.
17.5%-H2O2 gel was cytotoxic to pulp cells; however, cells subjected to
short-term bleaching are capable of expressing the odontoblastic
phenotype over time.