METHODS: Literature search on PubMed, Medline, and science direct databases was carried out for in vitro studies published in English from 1990 to 2016, and the reported outcomes of minimum inhibitory concentration (MIC), minimum bactericidal concentrations (MBC), zone of inhibition (ZOI) and bacterial count method using colony forming unit (CFU) were used to assess the antibacterial effectiveness of zinc.
RESULTS: Seventeen studies were included in this review. Seven studies reported MIC and MBC. Four studies reported ZOI, and eight studies reported CFU. MIC values using zinc chloride and zinc oxide nanoparticles were ranged from 0.025 to 0.2 mM and 0.390 to 500 ± 306.18 µg/ml respectively. MBC values using zinc oxide nanoparticles have ranged from 3.125 to 500 µg/ml. ZOI ranged from no inhibition zone to 21 ± 1.4 mm using 23.1% zinc oxide. A considerable reduction in the bacterial count was reported after adding zinc. However, only two studies have reported no inhibitory effect of zinc.
CONCLUSION: This review indicated a significant growth inhibition effectiveness of zinc even at lower concentrations which indicate it's safely to be used in oral health products.
METHODS: Antibacterial susceptibility assay, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were undertaken to evaluate the inhibitory activities of different zinc salts against the tested bacteria. A scanning electron microscope (SEM) was used to evaluate the morphological changes of bacterial cells following exposure to zinc salts. Kruskal-Wallis and Mann-Whitney tests were used to compare the inhibitory effect of the different zinc salts.
RESULTS: All zinc salts tested against S. mutans and S. sobrinus had a statistically and significantly smaller inhibition zone when compared to chlorhexidine, (P mm ± 5.5) against S. sobrinus, which was comparable to chlorhexidine (22 mm ± 4) (P > 0.05). Zinc chloride, zinc sulfate and zinc acetate demonstrated higher MIC and MBC values against S. mutans compared to S. sobrinus. However, zinc citrate revealed the highest MIC and MBC values of 1 mg/mL and > 8 mg/mL for S. sobrinus and > 8 mg/mL for S. mutans, respectively.
CONCLUSION: Different zinc salts have displayed inhibitory growth effects against the common oral bacteria at very low concentrations except for zinc citrate which showed no inhibitory effect against these bacteria in vitro.