Antimicrobial Potential of Nickel Ions Against Oral Microorganisms Using MIC/MBC

Objectives:  Nickel alloy is widely used in dentistry but its efficacy against oral microorganisms has not been fully documented.  The purpose of this study was to evaluate the antimicrobial potential of Nickel ions against four aerobes and four anaerobes using Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) assays.  Methods:  Four aerobes, Streptococcus mutans (ATCC 25175), Staphylococcus aureus (ATCC 27660), Candida albicans (ATCC 18804), Streptococcus sanguinis (ATCC 10556) and four anaerobes, Fusobacterium nucleatum (ATCC 49256), Prevotella intermedia (ATCC 49046), Porphyromonas gingivalis (ATCC 33277) Actinomyces viscosus (ATCC 43146) were cultured and optical density was standardized equivalent to 10⁶ cfu/mL using spectrophotometer.  Nickel (II) Chloride (0.32M) was serially diluted up to 1:512 dilution (0.00125M).  Equal volume of standardized organism was added to the diluted nickel ions including negative (sterile water) and positive (5.25% NaOCl) controls (2 mL total volume). MIC is the lowest concentration of the test solution that inhibits the growth of the organism as evidenced by the lack of turbidity. MIC was determined after overnight incubation at 37^oC. MBC is the lowest concentration of the test solution that showed no bacterial growth on the agar plate. MBC was determined by plating 100 microliter of the clear tubes onto agar plates.  Results:  MIC and MBC results are shown in the table below.

Conclusions:  Under the conditions of the present study, Nickel ions showed significant bacteriostatic and bactericidal effects on the eight oral microorganisms, especially on S. mutans, S. sanguinis (aerobes) and P. intermedia, P. gingivalis (anaerobes) as determined using MIC and MBC assays.

Key words: Bacteriostatic, Bactericidal, Nickel Ions, Microorganism, Optical Density