Enamel remineralization of a hydroxyapatite containing toothpaste: in vitro evaluation

OBJECTIVES: To evaluate the remineralization ability of a hydroxyapatite-containing toothpaste after cariogenic and erosion-induced challenges on human enamel specimens.

METHODS: Human caries-free molars were used. Eight fragments from 4 teeth of approximately 0.3gr weight were obtained. Each tooth contributed with two specimens, to have a control and a test fragment from the same tooth. Specimens were stored at 4˚C in a Basic Double Distilled H2O at pH 7.4. A cariogenic solution of lactic acid at pH 4.4 and an erosive solution of monohydrate citric acid (0.02M) at pH 2.5 were used. Enamel fragments were brushed initially for 10-min., then brushed for 3 minutes with a hydroxyapatite containing toothpaste (Test-Group); control group specimens were brushed for 3 minutes with Basic Double Distilled Water at pH 7.4. For the cariogenic test, specimens were subjected to three cycles, 2 for 3.5hrs and 1 for 17hrs, for three consecutive days. For the erosive test, specimens were subjected to 3 cycles of 5min exposure to the solution. Spectrophotometric analysis was performed to assess the concentration of Ca++ and PO4--- for both cariogenic and erosive test. Three measurements per specimen were recorded after each cycle,

RESULTS: After the 3rd cycle for both erosion and cariogenic tests, results showed: erosion test with Ca++ concentrations, 0.89 (±0.67SD) and 0.86 (±0.45SD) for test and control respectively, whereas for PO4--- 0.41 (±0.29SD) and 0.48 (±0.32 SD) test and control. Cariogenic test with Ca++ concentrations, 14.70 (±5.14SD) and 16.01 (±4.40SD) for test and control respectively, whereas for PO4--- 6.93 (±2.37SD) and 7.66 (±2.12SD) test and control. Statistical analysis showed no statistically significant difference for the erosion and cariogenic assays for both Ca++ and PO4--- concentration.

CONCLUSION: The hydroxyapatite-containing toothpaste treatment of human enamel did not result in a statistically significant higher resistance to erosive and cariogenic tests.