Molecular Mechanisms of Pulp Capping With Calcium Hydroxide
Parker, Benjamin John
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The ultimate goal of this research is to elucidate the molecular mechanisms of dental pulp capping agents to improve the effectiveness and reliability for improved clinical success. This procedure usually prevents the need for root canal treatment by inducing a mineralized barrier capable of protecting the dental pulp. There have been many speculations on how calcium hydroxide, a commonly used material for pulp-cap treatment, is able to induce reparative dentin but the molecular mechanisms remain unclear. This work examines the current favored hypothesis that the high initial pH of calcium hydroxide induces a “necrotic layer” on the exposed pulp while the viable pulp cells further away induce mineral deposition and drive reparative dentin formation. In this study, we attempt to dissect the roles of pH change and reactive oxygen species (ROS) on mouse dental pulp cells (MDPC-23) and mesenchymal stem cells (D1) on reparative dentin induction. A cellular model of mineralized tissue repair was assessed using biochemical and molecular assays including Alkaline Phosphatase (mineralization-promoting enzyme), Bradford’s assay (normalization of total protein), and luminol (ROS generation). In specific aim 1, pH solutions were made using HEPES as a base solution with sodium hydroxide or hydrochloric acid added to make solutions more basic or acidic, respectively, before exposure of cells to these conditions. In specific aim 2, Hydrogen peroxide in different concentrations was used to test if ROS alone could induce ALP production. Results indicate that different pH conditions as well as different hydrogen peroxide concentrations induced different levels of ALP expression in MDPC-23. In specific aim 3, ROS were shown to be produced by MDPC-23s during direct treatment with calcium hydroxide as well as elevated levels of ALP were expressed to cells exposed directly to calcium hydroxide. The results suggest that dentin repair may be only partly stimulated by the high pH of calcium hydroxide and that ROS may play an important role in dentin mineralization.