Abstract

Background/Objectives. The use of antibiotic pastes in the Lesion Sterilization Tissue Repair (LSTR) technique has increased due to their ability to disinfect necrotic primary teeth without mechanical instrumentation. Tri-antibiotic mixtures (TAP) and Chloramphenicol-Tetracycline-Zinc Oxide (CTZ) paste remain the most common options, although their composition and dosing lack standardization. Evidence indicates that silver and zinc oxide nanoparticles enhance antimicrobial performance by disrupting biofilms and modulating inflammatory pathways, suggesting potential benefits when incorporated into intracanal medications. This study aimed to evaluate the antimicrobial activity of a chloramphenicol–tetracycline paste modified with silver nanoparticles (SNPs) and zinc oxide nanoparticles (ZnONPs) against wild Enterococcus faecalis, comparing its MIC, MBC, and inhibition zones with those of a commercial CTZ paste. Methods. SNPs and ZnONPs (1 × 10−2 M) were synthesized and characterized using UV–Vis spectroscopy and dynamic light scattering (DLS). Two antibiotic pastes (1%) were formulated, including a nanoparticle-modified version with a 4% reduction in antibiotic content. Commercial CTZ paste was prepared according to the manufacturer’s instructions. Wild E. faecalis strains were isolated from necrotic primary teeth (N = 30). MIC, MBC, and inhibition zones were determined using microdilution and Kirby–Bauer assays. Results. AB Paste and Nanopaste showed larger inhibition zones (ZOI) than the other formulations (p < 0.001). MIC and MBC analyses showed no significant differences among antibiotic formulations and SNPs (p > 0.05). Conclusions. Both the nanoparticle-free antibiotic paste and the nanoparticle-modified paste demonstrated greater inhibitory activity than commercial pastes and Nanoparticles. Despite containing 4% less antibiotics, the Nanopaste showed equivalent efficacy, indicating that reducing the drug content does not compromise antimicrobial performance and that SNPs contribute to this effect.

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