The aim of this in vitro pilot study, therefore, was to evaluate the effect of NSCH on the hardness and modulus of elasticity of human dentine from extracted human permanent teeth.
One of the pair of samples was used as a control, with no medicament, and the other was covered with a layer of NSCH (UltraCal XS, Ultradent, USA).
After one month of NSCH application it was noted that the material was present only in the outer layers of dentinal tubules, and no penetration of NSCH was observed into the dentinal tubules (Figure 2b).
It would have been interesting to also investigate the depth of the effect of NSCH, but that was not the aim of this study.
It is clear from the results of nanoindentation that the hardness of dentine was significantly lower in the group where NSCH was applied as compared with the controls after 3 months.
Although this was a pilot study with a relatively small sample size the statistically significant differences between the time points seem to be quite indicative of the detrimental effect of NSCH on the fracture resistance of dentine as a function of contact time.
, where a statistically significant decrease in hardness of dentine was shown as soon as 7 days after the application of NSCH. From the present study design it can only be concluded that the significant changes started to manifest sometime between 1 and 3 months.