Quantification of dental erosion--a comparison of stylus profilometry and confocal laser scanning microscopy (CLSM).

Objectives: Since stylus profilometry applies a force on the sample surface, it is logical to hypothesize that the profilometer penetrates the surface of the enamel softened by acid solutions. The aims of the present study were, therefore, to test the hypothesis that surface profilometry measurements of eroded enamel alter the surface of the enamel, to quantify the potential effect of the surface alteration (scratches) on the measured values of enamel erosion by atomic force microscopy and to compare the values of enamel loss caused by erosion as measured by profilometry and non-contact confocal laser scanning microscopy (CLSM).

Methods: Enamel samples, cut from unerupted human third molars were treated with Volvic Mineral Water and citric acid solutions of different pH values. The enamel material loss was measured by two different contact profilometers and a reflection mode CLSM. The scratches depth was analyzed by atomic force microscopy.

Results: Our study demonstrated that the tip of the profilometer penetrated the surface of eroded enamel during the profilometry measurements, leading to clearly visible surface scratches on the enamel samples. The profilometers created surface scratches of a depth ranging from 57.6 (47.1)nm to 577.1 (157.6)nm on the surface of the eroded enamel and led, therefore, to a larger measured value of erosion. It was shown that the depth of the scratches depends on the pH value, the erosion time and the profilometer used.

Significance: With few exceptions profilometers deliver reliable values of erosive enamel material loss, although they create surface scratches on eroded enamel. Reflection mode CLSM is a non-tactile, fast and precise method for analyzing enamel erosion quantitatively in vitro.