Fixed dental braces are associated with the risk of developing White Spot Lesions (WSLs), which appear as white chalky marks on the teeth. They develop as a result of the acid produced by bacteria in dental plaque dissolving the outer surface of the tooth, known as demineralisation. Recently, amorphous calcium phosphate (ACP) stabilised by casein phosphopeptide (CPP) has become available, and it is reported to help rebuild the surface of teeth which have WSLs. CPP-ACP is available incorporated into a crème known as Tooth Mousse (TM). While there appears to be sufficient evidence regarding the use of CPP-ACP in promoting general remineralisation, for the first time this study aims to examine the use of CPP-ACP to treat WSLs in post-orthodontic participants.