Objective: To determine the efficacy of fluoride dentifrices to promote enamel fluoride uptake (EFU), promote lesion remineralisation (REM) and diminish subsequent demineralisation (DEM) using an in-vitro caries cycling model, and to compare the results with an in situ study. Methods: Artificial lesions were formed in human enamel specimens by immersion in lactic acid buffer (ACID). Test products: marketed dentifrice containing 1350ppmF from sodium fluoride/silica base (NaF); marketed dentifrice containing 1450ppmF (1000ppm from sodium monofluorophosphate, 450ppm from sodium fluoride) from a dicalcium phosphate base (MFP); USP reference standard containing 1450ppmF from sodium fluoride/silica base (USP); fluoride-free placebo (FFP, silica). The daily cycling regimen comprised: 4x1min dentifrice slurry treatments; 1x4h ACID challenge and remineralisation in a 50:50-mixture of pooled human and artificial saliva. After 20days, EFU was determined using the microdrill technique, and specimens were again challenged with ACID. VHN was measured after 20d (REM) and the subsequent ACID challenges (DEM). Results: EFU decreased as follows (ppmF):NaF(6504)>USP(5790)>MFP(1131)>FFP(308). NaF and USP delivered statistically significantly higher EFU than MFP and FFP, with NaF also being superior to USP.
REM and DEM results:
|
|
VHN |
|||
|
Dentifrice |
initial |
REM |
DEM-2h |
DEM-16h |
|
NaF |
35 |
144 |
134 |
119 |
|
MFP |
35 |
45 |
37 |
33 |
|
USP |
35 |
130 |
112 |
98 |
|
FFP |
35 |
30 |
25 |
22 |
Statistically significantly superior REM was observed for NaF and USP compared with MFP and FFP. NaF was directionally superior to USP in REM and in DEM. Both NaF and USP showed better protection against subsequent demineralisation (DEM) than MFP and FFP. There was a good correlation between EFU and REM. Conclusion: The sodium fluoride/silica-dentifrices (NaF/USP) delivered more fluoride into enamel and showed superior remineralisation than the MFP dentifrice which is in agreement with a comparable in situ study (Zero et al., IADR2007). The NaF dentifrices also offered greater protection against subsequent demineralisation than the MFP dentifrice.