Otten Marieke, UMCG Groningen, The Netherlands

Studying the contribution of dental plaque towards the substantivity of oral antimicrobials

M.P.T. Otten, C.G. van Hoogmoed, H.C. van der Mei, H.J. Busscher
Department of Biomedical Engineering, University Medical Center Groningen, University of Groningen, A. Deusinglaan 1, 9713 AV Groningen, The Netherlands, e-mail m.p.t.otten@med.umcg.nl

Background

Antimicrobial agents are added to toothpastes and rinses to augment plaque control. For antimicrobial activity these agents should be substantive, which means that they should be retained in the mouth by interaction with oral surfaces and subsequently released in effective values.

Aim

The aim of this study was to determine the contribution of dental plaque towards the substantivity of antimicrobial toothpastes.

Material and methods

12-h old plaque and saliva samples were collected from volunteers who brushed their teeth for two weeks with antimicrobial test dentifrices. We used a triclosan containing dentifrice and a stannousfluoride/hexametaphosphate containing dentifrice after two weeks of brushing with a control sodium fluoride containing dentifrice. For detection of the live and dead bacteria all samples were stained with LIVE/DEAD stain and analyzed by fluorescence microscopy, to define the viability of the samples. The antimicrobial effect was determined by comparing the viability values of the samples from the test toothpaste and the control toothpaste.
In the second part of the study the plaque samples of the control group were mixed with plaque and saliva samples of the test group (ratios 1:1 and 1:3). By analyzing the viability of the mixed samples and comparison with theoretically calculated values, the contribution of plaque and saliva towards 12 h substantivity determined.

Preliminary results

The viability of plaque samples from groups using antimicrobial toothpastes declined compared to the use of the control paste. None of the antimicrobial toothpastes showed a decrease in viability of saliva samples. Mixed samples of plaque from the control group and antimicrobial paste groups showed lower viability than theoretically calculated, indicating that plaque contributes towards substantivity of the antimicrobials. No contribution towards substantivity could be demonstrated upon mixing plaque from the control group with saliva from the antimicrobial group.