The importance of bioavailable calcium in fluoride dentifrices for tooth enamel remineralization (repair)

INTERVENTION: Dentifrices The dentifrices purchased for the study will include (1) Maximum Cavity Protection containing CaCO3/Arg/CaHPO4 and 1450 ppm F as Na2MFP (Colgate); (2) Sensodyne Protect and Repair containing calcium sodium phosphosilicate (CSP, NovaMin) and 1450 ppm F as Na2MFP (GSK); (3) Enamelon containing ACP and 1150 ppm F as SnF2 (Premier Dental); (4) ClinPro 5000 containing TCP and 5000 ppm F as NaF (3M ESPE); (5) MI One containing (CPP‐ACP) and 1100 ppm F as NaF (GC America); (6) 5000 ppm F as NaF control (Colgate) and (7) 1450 ppm F as NaF control (generic). The required sample size was calculated using the G*Power Version 3.1 sample size package and was based on a repeated measures analysis of variance with 7 levels, an effect size of 0.97, a correlation, ?, between any pair of treatment means of 0.5 and a non‐sphericity correction e of 0.5. The effect size of 0.97 was based on detecting differences between ?Zd‐?Zr means of 70 (fluoride control and fluoride plus calcium phosphate technology) and a common standard deviation of 100 within groups. The non‐sphericity correction adjusts for heterogeneity in the variances of the repeated measures. With a 5% significance level and a power of 90% at least 6 subjects will be required. To allow for subject attrition eight subjects will be recruited for the study. Intra‐oral Appliances and Enamel Subsurface Lesions Extracted human third molars will be sterilized, enamel slabs cut and subsurface lesions created as described by Shen et al. (2011). After lesion formation, one half of each enamel slab will be retained as the control half‐slab and stored in a humidified container. The other half slab (test) will be inset into an intra‐oral appliance to form a plaque retention site over the enamel lesions as described by Cochrane et al. (2012). Removable palatal appliances covering the first premolars to the last tooth in the arch will be fabricated for each participant as described by Cochrane et al. (2012). Two enamel half‐ CONDITION: Dental caries (tooth decay) ; Oral Health ; Dental caries SECONDARY OUTCOME: Secondary outcome variables will be the percentage change in mineral (%R) and the change in lesion depth (LDd‐LDr). At the end of each treatment period each test half‐slab will be paired with its control half‐slab and embedded, sectioned and analysed by transverse microradiography to determine mineral content as described previously (Cochrane et al. 2012). Lesion parameters, lesion depth (LD) and integrated mineral loss (?Z) will be determined and the ?Z value for the control demineralized lesion will be designated ?Zd and that for the treated lesion will be designated ?Zr. These values will then be used to calculate total mineral loss or gain ?Zd‐?Zr and percentage mineral change (%R) as (?Zd‐?Zr/?Zd) x 100. The change in lesion depth will be calculated as LDd‐LDr. INCLUSION CRITERIA: 1. Eight healthy adults living in Melbourne, Australia with a fluoridated (0.9 ppm F), reticulated water supply 2. Staff and students of the University of Melbourne 3. Age 18‐60 years 4. At least 22 natural teeth 5. Unstimulated whole salivary flow rate of = 0.2 ml/min 6. Gum‐stimulated whole salivary flow rate = 1.0 ml/min PRIMARY OUTCOME: The effects of the dentifrices on enamel remineralization will be compared using integrated mineral gain/loss, ?Zd‐?Zr, as the primary outcome measure. At the end of each treatment period each test half‐slab will be paired with its control half‐slab and embedded, sectioned and analysed by transverse microradiography to determine mineral content as described previously (Cochrane et al. 2012). Lesion parameters, lesion depth (LD) and integrated mineral loss (?Z) will be determined and the ?Z value for the control demineralized lesion will be designated ?Zd and that for the treated lesion will be designated ?Zr. These values will then be used to calculate total mineral loss or gain ?Zd‐?Zr and percentage mineral change (%R) as (?Zd‐?Zr/?Zd) x 100. The change in lesion depth will be calculated as LDd‐LDr.