Cytotoxicity of a new toothpaste based on an ion exchange resin mixture

To evaluate the effects for cytotoxicity of two dentifrices: a toothpaste commercially available (Crest Extra-Whitening toothpaste) and a new experimental toothpaste based on a mixture of ion-exchange resins (named NMTD) that supplies calcium, fluoride, phosphate and zinc ions.

Cultures of mouse fibroblasts cells L929 were used in a MTT assay for in vitro cytotoxicity of the dentifrices. Cells were cultured in Eagle's minimal essential medium supplemented with 10% fetal bovine serum. Cultures were incubated at 37 degrees C in a humidified atmosphere of 5% CO2 and collected by tripsinization (0.05% trypsin/0.5mM EDTA). A 96-well microplate method was employed for the MTT colorimetric assay. Positive control consisted of 10 microl of phenol in 5 ml of 6% media, a dose that produces zero percent cell survival. Negative control was prepared by adding 0.5 ml of HBSS to 4.5 ml of 6% media. The plates were incubated for 24 and 48 hours at 37 degrees C in a 5% CO2 atmosphere.

Means and standard deviations of absorbance values for each group and percentage inhibitory dosage (%ID) for each test material were calculated. None of the dentifrices resulted in a percentage of inhibition higher than 50% and did not observe marked increases in cytotoxicity with time of incubation. The positive control gave almost zero percent cell survival, whereas the negative control gave a hundred percent cell survival. Analysis of the results indicated that test dentifrice dose had no significant effect towards the cell viability (P<0.05).