Antimicrobial properties of dentine bonding agents determined using in vitro and ex vivo methods

Abstract 

Aims

To determine the antimicrobial properties of a selection of dentine bonding agents [DBAs] using the disc diffusion and direct contact methods and an ex vivo method using extracted carious permanent molar teeth.

Methods

DBAs (n=15) were tested using Streptococcus mutans UA159 in disc diffusion and direct contact methods. In the ex vivo study 6 DBAs were selected and pre- and post-treatment samples of carious dentine (n≤12) were taken. Samples were also taken post-acid-etching. The number of microorganisms in dentine sample was determined and compared.

Results

The inhibition zones and percent growth inhibition were related to the pH of the culture medium containing the DBA (p<0.01). Clearfill Protect Bond exhibited the greatest bacterial killing followed by ibond (99.8%±0.08 and 98.2±1.4, respectively). The phosphoric acid etchant alone resulted in an 83% killing. The in vitro tests results did not correlate. The ex vivo killing reflected the percent growth inhibition observed in the direct contact method.

Conclusion

A guide to the potential antimicrobial activity of a DBA may be gained from an assessment of its pH when added to bacteriological culture medium. The direct contact method gives a better reflection of the killing of bacteria in infected dentine than the disk diffusion method. Killing in the ex vivo model gives a more realistic and more reliable method for determining the antibacterial activity of a given DBA and that comparisons of the relative inhibitory activity of DBAs should be tested using this ex vivo model.

Keywords: Dentine bonding agent, Direct contact method, Disc diffusion method, Antimicrobial, Biocide, Phosphoric acid, Dentinal caries