<i>Nigella Sativa</i> Oil-Loaded Treated Dentin Matrix Hydrogel as an Alternative Biomaterial for Direct Pulp Capping: A Systematic Review

Objective: To assess evidence on Treated Dentin Matrix Hydrogel (TDMH) and Nigella sativa oil (NSO), individually or combined, as biomaterials for direct pulp capping (DPC) and their reparative dentin promotion ability. Methods: A systematic search of PubMed, EBSCO, ScienceDirect, and Wiley (January 1, 2018–December 31, 2023) was conducted using MeSH-based terms associated with ``treated dentin matrix hydrogel,'' ``Nigella sativa oil,'' and ``direct pulp capping.'' Eligible studies included in vitro, in vivo, and clinical research evaluating TDMH or NSO for DPC; studies with no outcome data were excluded. Risk-of-bias assessment was performed using ROB2 (clinical) and SYRCLE (animal). Because of heterogeneity, the results were synthesized narratively. Results: Eighteen studies were included (7 clinical studies, 3 in. vivo animal studies, 5 in. vitro studies, and 3 systematic reviews/meta-analyses). TDMH/TDM-based materials demonstrated significant potential for dentinogenesis and regeneration, as multiple studies reported superior reparative dentin outcomes compared to conventional materials. NSO demonstrated antibacterial, anti-inflammatory, and osteogenic effects, establishing it as an adjunctive agent, although its dentinogenic capacity was less established. Evidence quality ranged from moderate to low due to TDMH preparation variability, study design differences, and limited clinical trials. As limitations, heterogeneity in methodologies and outcome measures prevented meta-analysis, and clinical evidence remains limited. Conclusion: TDMH is a promising biomaterial for DPC, and NSO may enhance its antibacterial and biological performance. Well-designed clinical trials and standardized evaluation of combined TDMH–NSO formulations should confirm clinical applicability.