Assessment of enamel erosion and protective effect of salivary pellicle by surface roughness analysis and scanning electron microscopy.

Purpose: To assess dental erosion caused by 0.1% and 1.0% citric acid in vitro and to estimate the protective influence of experimentally formed salivary pellicle.

Materials And Methods: Bovine enamel slabs (n = 80) were polished and embedded in epoxy resin. For the formation of pellicle layer 40 specimens were immersed for 24 h in pooled human saliva. Erosion was caused by immersion in citric acid solution for 1, 5, 10 and 30 min. Erosive alterations on the pellicle-covered and non-covered enamel specimens were scored as a change (delta) of surface roughness parameters Ra, Rt and RzDIN using contact profilometer and observed in scanning electron microscope.

Results: Profilometric analysis of eroded enamel specimens emphasized the aggressiveness of even low concentrated citric acid with a short period of challenge. The change of roughness parameters after 1-min immersion in 0.1% citric acid were 16.4, 182.6 and 132.2 nm for deltaRa, deltaRt and deltaRzDIN, respectively, and 54.8, 516.6 and 258.2 nm after 1-min immersion in 1.0% citric acid. Changes of the surface roughness were dependent on the exposure time and concentration of acidic solution. Pellicle layer significantly reduced the extent of erosive destruction, which was additionally documented on SEM-micrographs. Residual pellicle-like structures were detected after 5 min of immersion in 0.1% citric acid. However, there were no significant differences in pellicle-covered and non-covered enamel slabs measured profilometrically for 1.0% citric acid with 10 min and 30 min exposure time.

Conclusion: The findings confirm the property of pellicle layer to resist against erosive influence of organic acids, which is, however, limited by duration of acidic treatment and concentration of erosive agent.