Effects of fluoride concentration and temperature of milk on caries lesion rehardening.

OBJECTIVES: The aim of the present in vitro study was to investigate the effects of fluoride concentration and temperature of milk on caries lesion rehardening under pH cycling conditions.

METHODS: Incipient caries-like lesions were formed in human enamel specimens, characterized using Vickers surface microhardness (VHN) and assigned to seven treatment groups (n=18 per group): fluoride was tested at five levels (0, 2.5, 5, 10, 20mg/l, all 22°C) and milk temperature at three levels (4, 22, 60°C), but only for 10mg/l F. Lesions were pH cycled for 15d (4 ×/daily 10 min milk treatments, 1 ×/daily 4h acid challenge, remineralization in human/artificial saliva mixture). VHN of specimens were measured again and changes from lesion baseline were calculated. Subsequently, enamel fluoride uptake (EFU) was determined using the micro drill technique.

RESULTS: Lesions responded to fluoride in a dose-response manner with higher fluoride concentrations resulting in more lesion rehardening (20>10 ≥ 5 ≥ 2.5>0mg/lF). Furthermore, fluoridated milk at 60°C was found to be more efficacious than at 4°C (60 ≥ 22>4°C). EFU results were similar (20>10>5>2.5 ≥ 0 mg/lF; 60>22≥4°C).

CONCLUSIONS: Both fluoride concentration and milk temperature are likely to contribute to the anti-caries potential of fluoridated milk.