Transdentinal Effects of Ceramic Self-Etching Primer on Pulp Cells

Objectives: To investigate the transdentinal response of pulp cells to the application of a self-etching ceramic primer that contains tetrabutylammonium dihydrogen trifluoride.
Methods: Freshly human extracted third molars had their occlusal surfaces removed and were cut to obtain dentin discs measuring 0.4 mm thickness. The dentin discs were initially subjected to dentin permeability test and randomly assigned to the study groups. Odontoblastic cells (MDPC-23) were seeded on the pulp dentin surface and five experimental conditions were tested to address cell viability (alamarBlue) and morphology (SEM). Positive Control (PC) was treated with hydrogen peroxide, negative control (NC) received ultrapure water, phosphoric acid (PA) was applied for 20s, 9% hydrofluoric acid (FA) was applied for 60s, and ceramic self-etching primer (MB) was applied following the manufacturer’s instruction when it is subjected to ceramic materials (n=10). After 24 h, extracts obtained from transdentinal diffusion were exposed to other MDPC-23 and human dental pulp cells (HDPCs). Cell viability was assessed with 1, 3, and 7 days and mineralized nodule formation after 7 and 14 days (Alizarin red). To the data statistical analysis, one-way ANOVA and post-hoc Tukey’s test were employed (α=5%).
Results: PC significantly reduced the viability of cells seeded on the discs (more than 80%). However, PA, FA, and MB did not reduce cell viability and presented the same viability as NC for cells seeded on discs or cultured with extracts. No statistical significance was found among NC, PA, FA, and MB. In addition, the cells did not show altered morphology or mineralization ability.
Conclusions: The application of different etchants on dentin with a minimum of 0.4 mm thickness did not affect the pulp cells response. Even though the results did not present harm to the pulp cells, FA and MB should not in any instance be applied on dentin surface.