The morphological effect of the acquired pellicle on acid-etched enamel: a scanning electron microscopy analysis

The aim of this study was to determine the effect of the acquired pellicle on enamel etching.

One-hundred teeth were sectioned in the buccal-lingual direction at the half crown. One-hundred half-crowns were polished with pumice powder and rotating brushes (group B) and one-hundred half-crowns were not polished on the buccal surface (group A). The samples were etched by 37% orthophosphoric acid gel for 30 seconds in a 2 mm diameter circular area at the middle upper section of the crown, rinsed with distilled water for 20 s, air dried for 20 s and observed by Scanning Electron Microscopy. Three independent operators determined the quality of enamel etching on a four-point scale using 200 images, which were computed by digital Image Analysis software. It analyses the grey values and converts them to three-dimensional graphics to value the surface extension. Analysis Of Variance test was used for comparisons between and within groups.

The mean of the operator values for the A samples is 2 ("Poorly defined etch") and for the B samples is 3 ("Defined etch"). The Image Analysis showed a significant difference (Analysis of Variance test) in the extension of the etched areas between groups A and B. The samples from group B had 11.7% more effectively etched enamel surfaces than the samples from group A.

Acquired pellicle removal by dental prophylaxis is necessary before enamel etching because it improves the effectiveness of the etching procedure.