Biological Potential of the Main Component, Thymoquinone, of Nigella sativa in Pulp Therapy—In Vitro Study

This work is designed to assess the antimicrobial efficacy, chelating efficacy, and dissolving capability of the bioactive agent of the Nigella sativa plant (thymoquinone). Four freeze-dried microorganisms were studied. Each species was treated with either 6% sodium Hypochlorite, thymoquinone, or sterile water. The zone of inhibition was measured. Thirty extracted human premolar teeth were utilized to evaluate the smear layer removal. Root canals were mechanically instrumented and then irrigated with either 6% sodium Hypochlorite, 17% ethylenediaminetetraacetic acid, or thymoquinone for 1 min and scanned under the scanning electron microscopic to evaluate the cleanliness of the root canal and the remainder of the smear layer. To evaluate the tissue dissolving effect, Bovine Pulp Tissue was utilized. Randomly treated samples included: 6% sodium Hypochlorite, thymoquinone, or isotonic saline for 30 min. The remaining pulp tissue was weighed. Thymoquinone reported the highest inhibition of microbial multiplication compared to other irrigants (p < 0.001). Thymoquinone solution had an excellent antibacterial effect on endodontic pathogen and did not affect the inorganic and organic tissue inside the root canal. Meanwhile, it reported weak chelating and dissolving effects. Tissue dissolution was statistically significant with sodium Hypochlorite solution compared to other groups (p < 0.001).