Tailoring Silicon Nitride Surface Chemistry for Facilitating Odontogenic Differentiation of Rat Dental Pulp Cells

Silicon nitride (Si(3)N(4)) can facilitate bone formation; hence, it is used as a biomaterial in orthopedics. Nevertheless, its usability for dentistry is unexplored. The aim of the present study was to investigate the effect of Si(3)N(4) granules for the proliferation and odontogenic differentiation of rat dental pulp cells (rDPCs). Four different types of Si(3)N(4) granules were prepared, which underwent different treatments to form pristine as-synthesized Si(3)N(4), chemically treated Si(3)N(4), thermally treated Si(3)N(4), and Si(3)N(4) sintered with 3 wt.% yttrium oxide (Y(2)O(3)). rDPCs were cultured on or around the Si(3)N(4) granular beds. Compared with the other three types of Si(3)N(4) granules, the sintered Si(3)N(4) granules significantly promoted cellular attachment, upregulated the expression of odontogenic marker genes (Dentin Matrix Acidic Phosphoprotein 1 and Dentin Sialophosphoprotein) in the early phase, and enhanced the formation of mineralization nodules. Furthermore, the water contact angle of sintered Si(3)N(4) was also greatly increased to 40°. These results suggest that the sintering process for Si(3)N(4) with Y(2)O(3) positively altered the surface properties of pristine as-synthesized Si(3)N(4) granules, thereby facilitating the odontogenic differentiation of rDPCs. Thus, the introduction of a sintering treatment for Si(3)N(4) granules is likely to facilitate their use in the clinical application of dentistry.