M Beerens

DISCUSSION 6 105 GENERAL DISCUSSION Orthodontics is very popular for restoring not only function, but also facial aesthetics. Especially in high income countries, orthodontic treatment with fixed appliances is frequently applied (Ren et al. , 2014). A downside of these fixed appliances is that they impede effective plaque removal. Poor dental hygiene procedures combined with a high-frequency carbohydrate diet, lead to colonisation of aciduric bacteria. This may contribute to the occurrence of dental caries (Øgaard et al. , 1988). Although the caries prevalence and severity has declined over the last four decades, especially in high income countries (Frencken et al. , 2017), the growing demand for orthodontic treatment and a high occurrence of oral biofilm-related complications, orthodontic treatment might become a public health threat (Ren et al. , 2014). Early dental caries lesions, so called white spot lesions (WSL) occur especially at the gingival margins and at the bracket-adhesive enamel junction (van der Veen et al. , 2007). The management of these WSL is of clinical importance, also for aesthetic reasons (Murphy et al. , 2007). Risk factors and risk assessment Risk factors for caries that have been reported are: Young age at the start of the treatment, inadequate oral hygiene before the beginning of the treatment and during the treatment, inappropriate diet (high frequency of fermentable carbohydrates in food and beverages), history of recent carious lesions or a high number of decayed missing and filled surfaces (DMFS) and duration of treatment (Chapman et al. , 2010; Khalaf, 2014). Poor oral hygiene seems to pose the highest risk in developing WSL (Khalaf, 2014). Poor oral hygiene not only increases the amount of biofilm but also the prevalence of cariogenic bacteria, such as Streptococcus mutans and Lactobacillus spp. (Al Mulla et al. , 2009). By comparing patients with and without WSL by determining characteristics of the dental biofilm, a caries risk profile may be assessed. This thesis concludes, however, that microbiological composition shows a high inter-individual variation between patients with and without orthodontic WSL. This was assessed by two methods: Conventional microbiological plating and DGGE. Therefore, differences in microbiological ecology do not have a predictive value for caries risk assessment.