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

AimsTo 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.MethodsDBAs (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.ResultsThe 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.ConclusionA 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.