Applicability of common methods for short time erosion analysis in vitro

Dental erosion can be measured by different methods. The aim of the present study was to check the applicability of common methods to determine initial erosive effects.

Enamel surfaces (4.5 mm2) were eroded in vitro by treatment with hydrochloric acid (pH 2, 2.3 and 2.6) for 5 to 60 s or 240 s, respectively. Erosive effects were assayed with three different methods: Knoop's diamond indentation, profilometry and the determination of the dissolved calcium ions (Ca2+) in a colorimetric assay based on the arsenazo-III-reaction.

Erosive mineral loss of > 1 microm are measurable with profilometry. This corresponds to the erosive effects that occur after 60 s or more. Profilometric data yielded variance of up to 50%. Knoop's diamond indentation also showed some limitations: the depth of indentation reached a plateau after 30 to 120 s and the measurements showed variance of up to 85%. With the colorimetric assay, short time erosive effects occurring within 5 s could be assessed precisely and kinetically. The method allowed small amounts of 400 pmol Ca2+ per well to be quantified in small volumes with little variability.

For evaluation and quantification of short time erosive effects, the colorimetric method is superior to diamond indentation and profilometry.