M Beerens

80 CHAPTER 5 INTRODUCTION Enamel subsurface lesions, so-called white spot lesions (WSL), can form rapidly around orthodontic brackets. These WSL are vulnerable to ongoing demineralisation (Gorelick et al. , 1982; Mizrahi, 1983; Øgaard et al. , 1988; Lovrov et al. , 2007). Individuals with elevated levels of acidogenic bacteria in saliva and plaque are at high risk for the development of WSL (Scheie et al. , 1984; Rosenbloom and Tinanoff, 1991; Ahn et al. , 2007; Kim et al. , 2010). A product, MI Paste Plus ® (Tooth Mousse Plus ® ), was developed to improve remineralisation. This product contains 900 p.p.m. fluoride with added calcium and phosphate, in a composition ideal for depositing fluorapatite into enamel (Reynolds, 1997; Cross et al. , 2004; Reynolds, 2008). A crucial component of the product is the milk-derived protein casein phosphopeptide (CPP), which stabilizes amorphous calcium phosphate (ACP). This is converted to fluorapatite deposited in enamel by the available fluoride (Cross et al. , 2004; Cochrane and Reynolds, 2012). The efficacy of CPP-ACPF was demonstrated in vitro both for the prevention and for the regression of incipient lesions (Cochrane et al. , 2008; Reynolds et al. , 2008). However, there is a lack of reliable evidence of the efficacy of CPPACPF for the treatment of post-orthodontic WSL in vivo (Chen et al. , 2013; Raphael and Blinkhorn, 2015). Also the long-term effect of this remineralising agent is unclear (Li et al. , 2014). In this prospective double-blinded randomized placebo-controlled superiority trial, we assessed the long-term (12months) remineralisation effect of MI Paste Plus ® on existing WSL immediately after fixed orthodontic appliance treatment in vivo , to be used in addition to normal oral hygiene. The primary outcome assessed by quantitative light-induced fluorescence (QLF) is fluorescence loss and lesion area. Secondary outcome was based on microbial composition by conventional plating and acidogenicity of plaque by capillary ion analysis (CIA). Additionally, lesion changes were assessed visually on clinical oral photographs.