Influence of highly concentrated fluoride dentifrices on remineralization characteristics of enamel in vitro
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The aim of this in vitro study was to evaluate the role of highly fluoridated dentifrice on remineralization characteristics of lowly and highly pre-demineralized enamel artificial caries lesions.
Bovine enamel specimens were prepared (pH 4.95; 21 days) and discriminated in either lowly [L] or highly [H] pre-demineralized artificial caries lesions. Specimens with a mean ΔZbaseline,L (95% CI) of 5120 (4995; 5245) vol.% × μm and a mean ΔZbaseline,H of 8187 (8036; 8339) vol.% × μm were selected and randomly allocated to 12 groups (n = 20). Treatments during pH-cycling (28 days; 6 × 60 min demineralization/day) were brushing 2×/day with fluoride-free (0 ppm F− [L0/H0]), 1100 ppm F− [L1100/H1100], 2800 ppm F− [L2800/H2800], 5000 ppm F− [L5000/H5000], 5000 ppm F− + glycerin [L5000 + glycerin/H5000 + glycerin], and 5000 ppm F− + TCP [L5000 + TCP/H5000 + TCP] containing dentifrices. Dentifrice slurries were prepared with deionized water (1:3wt/wt). After cycling specimens presenting lesion surface loss were discarded and for the remaining 202 specimens, transversal microradiographic (TMR) analyses (ΔZpH-cycle/LDpH-cycle) were performed again. Changes in mineral loss (ΔΔZ = ΔZbaseline − ΔZpH-cycle) and lesion depth (ΔLD = LDbaseline − LDpH-cycle) were calculated.
Significant differences for ΔΔZ could be found between L0, L1100, and L5000 as well as H0, H1100, and H2800/H5000 (p ≤ 0.01; ANCOVA). Except for 0 ppm F−, higher ΔΔZ could be found in highly compared with lowly demineralized specimens (p ≤ 0.004; ANCOVA). After pH-cycling, a second lesion front could only be observed in H5000 and H5000 + TCP. The correlation between ΔΔZ and F− was moderate for lowly and highly demineralized lesions (rL = 0.591; pL < 0.001; rH = 0.746; pH < 0.001), indicating a fluoride dose response for both.
For both baseline substrate conditions, a dose response for fluoride could be revealed.
Remineralization characteristics of enamel directly depended on baseline mineral loss.
KeywordsEnamel caries Fluoride Non-cavitated caries lesions pH-cycling Remineralization Toothpastes
This study was conducted as part of the doctoral thesis of S.W.. We would like to thank Rainer Dautzenberg, Axel Honné, and the whole team of the scientific construction laboratory of the RWTH Aachen University for developing, constructing, and assembling the computer-controlled pH-cycling and brushing machine. Furthermore, we would like to thank Klaus Mussler for their excellent collaboration and technical assistance.
R.J.W., J.L., S.W., and M.E.-O. designed and planned the study; S.W. prepared the samples and performed the measurements; R.J.W. and S.W. performed the statistical analysis; R.J.W. and M.E.-O. wrote the manuscript; S.W. and H.M.-L. commented on, and all authors revised the manuscript.
This study was funded by the authors and their institution.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interests.
This article does not contain any studies with human participants or animals performed by any of the authors.
For this type of study, formal consent is not required.
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