This study mainly compared the response of the artificial carious enamel lesions to remineralisation in situ. The tested in vitro demineralising protocols were: MC gel, PA gel, MHDP and Buffer solutions.

The lesions were then remineralised in an in situ model, with crossover and double blind design. Fifteen volunteers wore intra-oral appliances containing 2 bovine enamel samples of each demineralising protocol during 3 experimental phases (3 days each). The experimental phases/treatments were: Control (Placebo dentifrice, saliva effect only), Home-care (fluoride dentifrice, 1,100 ppm F, NaF), and Professional/Home-care (varnish- 22,600 ppm F and dentifrice- 1,100 ppm F, NaF).

During the 3-day phase, the appliance was only removed during the main meals (four times a day, maximum 1 h duration each, interval between meals 2-3 h). Immediately after the meals, before replacing the appliance in the mouth, the subjects were advised to perform oral hygiene using a soft end-rounded toothbrush (Colgate® 360º Sensitive Pro-Relief TM) and dentifrice (non-fluoridated from IceFresh, Bauru, SP, Brazil or fluoridated dentifrice from Crest Procter & Gamble, Cincinnati, OH, USA) according to the phase and dental floss (Sanifill, São Paulo, Brazil).

The remineralising treatment with dentifrices was done ex vivo, 1 min twice a day (after the first and last oral hygiene of the day) using slurry of the dentifrice (1:3 water, 1 drop of solution/specimen). Thereafter, the appliance was replaced in the mouth and the subjects were advised to rinse with 10 ml of water for 5 s and to expectorate. In respect to Professional/Home-care phase, the varnish (Duraphat, Colgate, SP, Brazil) was applied before the in situ study for 6h and then removed.

The enamel remineralization was quantified using transverse microradiography (% mineral recovery and lesion depth, TMR), surface and cross-sectional hardness. The data were submitted to statistical analysis (p<0.05).

Inclusion Criteria:

• a stimulated physiological salivary flow rate of >1 ml.min-1
• a non-stimulated physiological salivary flow rate of >0.25 ml.min-1
• good oral health (i.e. no cavities or significant gingivitis/periodontitis)

Exclusion Criteria:

• systemic illness
• pregnancy or breastfeeding
• use of fixed or removable orthodontic appliances
• use of fluoride mouthrinse or professional fluoride application in the last 2 months.