IN VITRO STUDY OF POLYMETHYL METHACRYLATE COMBINED WITH SEED OIL OF NIGELLA SATIVA L. AS AN ANTIMICROBIAL BIO-BASED POLYMER FOR DENTAL APPLICATIONS

Abstract

There is a constant need for a biocompatible ingredient that can give restorative materials antimicrobial action without compromising their physical and mechanical characteristics. Although polymethyl methacrylate (PMMA) is the most well-known and contemporary material to make orthodontic retainers and dentures, and for repair, its exceptional properties, including its antimicrobial activity are lacking. The concentration-dependent cytotoxic effects of oil on normal dental oral cells were assessed using the SRB assay. Nigella sativa L. has demonstrated antimicrobial, anti-inflammatory, and antioxidant activities. The current study highlighted the preparation of PMMA, which combined with natural seed oil extract of N. sativa L. as bio-based filler to improve its antimicrobial, mechanical and physical properties. The extract of N. sativa L. seed oil (NSO) was prepared using cold press and Soxhlet extraction methods. Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC‒MS) studies were used to implement precise qualitative analysis of the contents of the obtained essential oil and compounds. FTIR confirmed the presence of the O-H functional group that is related to phenols and alcohols, C-H stretching of an aliphatic group and denotes the presence of methyl and isopropyl components, C=O stretching of oxygen-containing groups of ester and carbonyl group, as well as C-O, and =C-H stretching bands. The GC‒MS results indicated the presence of 23 different compounds. Amongst these, octadecadienoic acid (27.27%), monolinolein (18.64%), thymoquinone (11.71%), and (9.18%) of D-glucopyranose and D-(-)-fructopyranose were the most abundant compounds. Heat-curing acrylic resin polymer and monomer in the ratio 3:1 was prepared and mixed manually with different volumes (0.5 ml, 1 ml, and 1.5 ml) from NSO. Biosafe dose analysis showed the need for careful evaluation of oil biocompatibility in dental applications, as excessive concentrations may compromise cell membrane integrity, induce oxidative stress, and trigger inflammatory responses. The impact strength and flexural strength of the prepared modifier were tested and indicated to show a non-significant decrease in the impact strength values of each denture base and denture lining for the tested samples compared to the control groups after the addition of NSO with higher volumes than 1 ml. Similarly, a significant increase in flexural strength occurred after the addition of NSO to PMMA with NSO volume lower than 1 ml. The antimicrobial activity of the prepared modifier was also tested against Candida albicans, methicillin-resistant S. aureus (MRSA), and Enterobacter aerogenes. Agar well and minimum inhibition concentration (MIC) were investigated and confirmed the potent antimicrobial action of the prepared modifier with MIC values of 55 µg/ml, 90 µg/ml, and 50 µg/ml against C. albicans, MRSA, and E. aerogenes, respectively. As indicated by the obtained data, NSO appears to be a very promising supplementary additive to PMMA, capable of improving specific mechanical properties and producing significant antimicrobial activity.