E-Mail karger@karger.com Original Paper Caries Res 2015;49:583–590 DOI: 10.1159/000439315 Effect of the Probiotic Lactobacillus rhamnosus LB21 on the Cariogenicity of Streptococcus mutans UA159 in a Dual-Species Biofilm Model Constanza E. Fernández a Rodrigo A. Giacaman b Livia M. Tenuta a Jaime A. Cury a a Piracicaba Dental School, University of Campinas, Piracicaba, Brazil; b Cariology Unit, Department of Oral Rehabilitation and Interdisciplinary Excellence Research Program on Healthy Aging (PIEI-ES), University of Talca, Talca, Chile as percentage of SH loss (%SHL). Additionally, the model was tested with different concentrations of the initial inoculum (10 3 , 10 6 , 10 8 cells/ml) and different adhesion times (2 or 8 h). The dual-species biofilm revealed no LB effects on SM cario- genicity, without changes in acidogenicity or %SHL among groups (p > 0.05, n = 12). Lack of activity of LB on SM cario- genicity persisted even when 10 5 times higher concentra- tion of the probiotic was tested. Coaggregation was not ob- served. In conclusion, findings suggest that LB does not re- duce cariogenicity of SM in a validated experimental caries model. © 2015 S. Karger AG, Basel Although there is a growing body of evidence on the use of probiotics in dental caries, the real efficacy of pro- biotics in caries lesion prevention is still limited and con- troversial [Cagetti et al., 2013]. Most of the studies have focused on the mechanism of action of the probiotics, essentially on the reduction of Streptococcus mutans counts [Laleman et al., 2014]. Even in clinical studies, end points are usually indirect measurements such as a reduction of S. mutans in saliva [Nase et al., 2001; Ahola et al., 2002; Nikawa et al., 2004; Juneja and Kakade, 2012; Holz et al., 2013; Campus et al., 2014; Teanpaisan and Key Words Aging · Bacteria · Biofilm model · Caries · Demineralization · Enamel · Older adults · Plaque · Probiotics · Root caries Abstract Despite promising results using probiotics, evidence of the preventive effect on enamel demineralization is insufficient and the cariogenic potential of probiotics is still controver- sial. Probiotics could affect biofilm formation and interfere with adherence, growth or coaggregation with Streptococ- cus mutans in biofilms. However, most of the studies have been conducted using planktonic bacteria. Hence, the aim of the study was to assess the effect of probiotic bacteria on the cariogenicity of S. mutans using an in vitro biofilm caries model on enamel. Single-species biofilms ( S. mutans UA159, SM or Lactobacillus rhamnosus LB21, LB) or dual-species bio- films simultaneously inoculated (SM + LB) or LB inoculated 8 h after SM (SM → LB) were grown for 96 h. Biofilms were formed on bovine enamel saliva-coated slabs of known sur- face hardness (SH) and immersed in culture media. Biofilms were exposed 8 times per day to 10% sucrose. Medium pH was monitored twice daily as a biofilm acidogenicity indica- tor. After 96 h, biofilms were collected to determine biomass and bacteria viability. Slab demineralization was calculated Received: January 18, 2015 Accepted after revision: August 10, 2015 Published online: October 10, 2015 Rodrigo A. Giacaman, DDS, PhD Escuela de Odontología Universidad de Talca 2 Norte 685, Talca (Chile) E-Mail giacaman  @  utalca.cl © 2015 S. Karger AG, Basel 0008–6568/15/0496–0583$39.50/0 www.karger.com/cre Downloaded by: Verlag S. KARGER AG, BASEL 172.16.6.1 - 10/12/2015 5:28:06 PM