M Beerens

DGGE FOR CARIES RISK ASSESSMENT IN ORTHODONTICS 3 41 INTRODUCTION Oral microorganisms play a key role in dental diseases such as dental caries and periodontal disease. Specific bacterial species in plaque have been associated with these oral diseases (Becker et al. , 2002; Munson et al. , 2004; Marsh, 2010). In caries, the main causative microorganisms are Streptococcus mutans and Lactobacilli spp (Socransky, 1979; van Houte et al. , 1982; Boyar and Bowden, 1985; Tanzer et al. , 2001). However, according to the current paradigms caries is not caused by a limited number of specific bacteria, but by a shift in the microbial population to a more unhealthy microbiome (Marsh, 2003; Chapman et al. , 2010; Marsh, 2010; Thomas et al. , 2012). Therefore, monitoring changes in the microbial composition might help guide prevention and treatment of caries (Lucchese and Gherlone, 2013). Among the methods to assess polymicrobial ecosystems, Denaturing Gel Gradient Electrophoresis (DGGE) was developed for qualitative compositional analyses (Rasiah et al. , 2005; Li et al. , 2007). In DGGE, band patterns and especially the number of bands detected is a measure of the bacterial diversity, while banding patterns can be used to compare similarity between specimens (figure 1). Li et al. (2007) and (Ling et al. , 2010) have suggested that DGGE could predict the risk of developing early childhood caries. For patients undergoing orthodontic treatment this technique might be useful to assess the bacterial composition of plaque, and consequently the risk for dental caries. This is important as the formation of white spot lesions (WSL) occurs in 2 to 96% of these patients (Boersma et al. , 2005; Chapman et al. , 2010; Hadler-Olsen et al. , 2012). A method to assess caries risk must be robust and unambiguous. Therefore, to assess plaque diversity by DGGE, the software used to identify and quantitate bands must be discriminative, with a high specificity and sensitivity. An automated analysis, with objective detection of bands, is, essential to make the method a robust screening test. The aim of this methodological study was: 1. to test the reliability of the software program Gelcompar II analysis using different automated band detection settings in comparison to manual detection, and 2. to assess the optimum setting to see if there is a difference between orthodontic patients with or without WSL and asses if DGGE has predictive value for the development of WSL during orthodontic treatment.