Melbourne Dental School - Theses
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ItemEnhancing remineralisation using casein phosphopeptide complexes( 2017)Casein phosphopeptide (CPP) complexes have been shown to promote remineralisation of dental tissues affected by dental caries. However, remineralisation takes time and can be limited by the delivery and composition of the remineralisation agent. The aim of this thesis was to enhance remineralisation by CPP complexes through clinical and laboratory studies assessing various chemical changes to the remineralisation process. Using an in vitro enamel remineralisation model, it was determined that intra-lesion serum albumin did not interfere with remineralisation by casein phosphopeptide stabilised amorphous calcium fluoride phosphate (CPP-ACFP). A high pH pre-treatment significantly increased remineralisation by CPP-ACFP. To expand on this finding, a cyclic in vitro remineralisation model tested intra-lesion pH modulation whereby enamel subsurface lesions were periodically exposed to CPP-ACFP (pH 5.5) and either sodium hypochlorite (pH 12.9), sodium hydroxide (pH 12.9) or distilled deionised water. Enamel subsurface lesions that had cyclic treatment with CPP-ACFP and sodium hydroxide were observed to have significantly higher remineralisation, displaying intra-lesion pH modulation enhanced remineralisation. Cyclic treatment with CPP-ACFP and sodium hypochlorite was observed to further demineralise and cause a surface precipitation due to a disadvantageous interaction of the treatment solutions. A second short-term cyclic in vitro remineralisation experiment revealed intra-lesion pH modulation with CPP-ACFP and sodium hydroxide was more effective than an equivalent exposure to CPP-ACFP alone. The use of x-ray microtomography (XMT) to measure remineralisation by CPP-ACFP in vitro was assessed using conventional polychromatic and monochromatic synchrotron x-ray sources. These methods of analysis were compared with transverse microradiography (TMR) analysis to investigate the accuracy and practicality of each method. XMT analysis from both x-ray sources detected remineralisation in enamel lesions however the amount of remineralisation detected was significantly less than that detected by TMR. Due to a range of artefacts unique to the x-ray source and the devices used, it was determined that XMT analysis of remineralisation under the conditions used was less sensitive compared with TMR. The remineralisation potential of a combined casein phosphopeptide stabilised amorphous calcium phosphate (CPP-ACP) and stannous fluoride (SnF2) solution was tested in vitro and in situ. The combined CPP-ACP and SnF2 solution showed significantly higher enamel remineralisation than all other treatments due to an increase in CPP complex stability and ion delivery. The interaction of a combined CPP-ACP and SnF2 solution with surface dentine in vitro displayed an organic ‘nanocoating’ suggesting stannous ions mediated CPP cross-linking and ion release at the dentine surface. A crossover clinical study was conducted on low caries-risk individuals to assess changes in the abundance of Streptococcus sanguinis in supragingival plaque following a two week intervention period chewing either CPP-ACP sugar-free gum, sugar-free gum or no gum. It was determined that chewing the CPP-ACP gum significantly increased the abundance of S. sanguinis, as well as other commensal, alkaline-producing microorganisms. This demonstrated chewing CPP-ACP gum exerted a prebiotic effect in supragingival plaque. The promising results expounded in this thesis indicate modifications to the composition and delivery of CPP complexes have the potential to improve the rate and amount of remineralisation.