Histological, morphological, profilometric and optical changes of human tooth enamel after microabrasion

Purpose: To determine the loss of enamel after a single 20-secondsapplication of a microabrasion slurry and to evaluate structural changes by means of laser fluorescence, and microscopic and optical measurements. Methods: Defined buccal areas with a diameter of 2 mm from 16 extracted human molars were demineralized for 12 weeks using a demineralization gel (pH 4.8). The created artificial white-spot lesions were divided corono-apically in control and test sites, using a rubber cement that prospectively covered the untreated control site. Teeth were divided into two groups of eight teeth each. One group was treated with an abrasive cleaning paste (Pell-ex) and the other group with a commercially available microabrasion slurry (Opalustre) for 20 seconds, applying a load of 200 g. Before and after treatment, standardized photographs were taken for the determination of luminescence and profilometric tracings of the surface, and these were recorded for the determination of enamel loss. The grade of demineralization was quantified using a laser fluorescence method (Diagnodent). Statistical differences were checked using a Mann Whitney and student t-test. Replicas of the treated areas were made for scanning electron microscopy (SEM) analysis, and teeth were histologically investigated by polarized light microscopy. Results: Loss of tooth substance was significantly higher (P less than or equal to 0.001) for the microabrasion group (134.8 +/- 35.5 mum) compared with the abrasive cleaning paste group (4.5 +/- 1.2 mum). After treatment, statistically significant differences in fluorescence and luminescence measurements could only be detected for microabraded teeth. No significant changes were noted for teeth treated with an abrasive cleaning paste. Histological findings confirmed removal of the demineralized surface zone when microabrading the enamel, whereas no changes were observed in the test group treated with an abrasive cleaning paste. Polarized light microscopy did not indicate any changes in the mineralization pattern, for example compaction, in the treated subsurface zone.