M Beerens

13 GENERAL INTRODUCTION 1 bleaching (Knösel et al. , 2007) and preparation and restoration (Shungin et al. , 2010) applied only on inactive lesions. From a minimally invasive perspective, fluoride has been shown to arrest the development and progression of caries lesions during orthodontic treatment (Marinho, 2009). Concentrated fluoride is not recommended for treatment of WSL on the labial surfaces of the teeth in the esthetic zone. Concentrated fluoride results in a hyper-mineralized subsurface of the lesion (Øgaard et al. , 1988; Willmot, 2004), which inhibits the ion movement through the subsurface (ten Cate and Arends, 1980). This prevents further demineralisation but also remineralisation, of the deeper layer of the lesion is inhibited. The lesion remains as a white scar. Therefore, minimally invasive approaches with other applications than fluoride are preferred, to effectively remineralize WSL associated with orthodontic treatment, (Cochrane et al. , 2010). Minimal intervention Paste Plus ® Within the minimal invasive approach the CPP-ACP technology has been developed by Professor E. Reynolds and his team at the University of Melbourne Dental School. Casein phosphopeptide (CPP) is a milk derived protein able to bind calcium and phosphate ions and stabilise these ions as amorphous calcium phosphate (ACP). CPP-ACP adheres intra-orally to plaque pellicle, mineral as well as soft tissues. When dissolving it supplies bioavailable calcium and phosphate to saliva and plaque pellicle enabling it to stimulate remineralisation. Also this CPP-ACP complex binds with about twice the affinity of the bacterial cells for calcium (Rose, 2000). The newer form of CPP-ACPF products contains fluoride. The fluoride ions in amorphous calcium phosphate fluoride are stabilised in this ion complex and able to diffuse through the subsurface layer (Ahmadi Zenouz et al. , 2015). This formulation is the main active ingredient of a commercially available remineralisation agents called MI Paste Plus ® . This product contains 900 parts per million fluoride in a mole ratio with the calcium and phosphate of 5 calcium, 3 phosphate and 1 fluoride, considered the ideal ratio for building fluorapatite into the enamel structure (Cross et al. , 2004; Reynolds, 2008).