Remineralization of Enamel by a Hydroxyapatite Protein Composite containing Toothpaste

Objectives: To evaluate the remineralizing potential of a prototype toothpaste containing the hydroxyapatite protein composite Nanit®active (HPC) in two re- and demineralization models. Methods: Both studies used flattened and polished bovine enamel slabs. Remineralization was assessed by measurement of Knoops hardness. Model1, strong demineralization: 6 hour demineralization (pH 4.6 lactic acid, average hardness drop 11% from sound baseline) followed by 5 x 7 hours remineralization (artificial saliva) with treatment every 30 minutes. Model2, mild demineralization and cycling: 3 d demineralization (pH 4,6 HMC lactic acid Gel, average hardness drop 35% from sound baseline) followed by 10X10 hours pH cycling including 120 min remineralization alternated by 30 min of demineralization (pH 5, lactic acid). Treatments were performed every 30 minutes. Groups: Model1 (9 specimens each): 1) HPC toothpaste, 2) toothpaste without HPC (negative control), 3) commercial toothpaste (positive control). Model2 (10 specimens each): 4) HPC in toothpaste, 5) toothpaste without HPC (negative control), 6) placebo (glycerol and thickener). All toothpastes contained 1450 ppm Fluoride and were used as 3:1 slurries in water. Results: Hardness recovery (Knoops hardness) and recovery from demineralization (%): Model1: 1) 160±30 (52%), 2) 51±8 (28%), 3) 10±7 (13%) Model2: 4) 94±11 (74%), 5) 99±9 (78%), 6) 70±11 (54%) For heavily demineralised enamel (model1) the HPC toothpaste leads to a significantly stronger recovery of hardness than the controls. The base formula (2 and 5) shows activity itself. In model2 effects of fluoride become dominating. Conclusions: HPC is known to initiate the formation of apatite from saliva. This mechanism apparently is leading to an increased remineralization particularly on heavily demineralized enamel and is clearly adding to the effect of fluoride. The poor performance of fluoride within model1 is surprising.