BRUSHING-INDUCED EFFECTS WITH AND WITHOUT A NONFLUORIDE ABRASIVE DENTIFRICE ON REMINERALIZATION OF ENAMEL SURFACES ETCHED WITH PHOSPHORIC-ACID

The remineralization of acid-etched enamel after brushing with and wit hout a non-fluoride abrasive dentifrice was investigated using scannin g electron microscopy after sodium hypochlorite (NaOCl) or ethylenedia mine tetra-acetic acid treatment, of the specimens. Ground enamel piec es were etched with 30% phosphoric acid for 60 s and attached to resin plates. They were exposed to the oral environment of 4 subjects for 8 weeks and brushed for 1 min daily. Paste and brushing caused the acid -etched enamel to erode selectively, i.e., deep grooves were formed in the prism peripheral regions, while projections of the prism bodies s howing a relatively low density of crystallites were retained. Brushin g without dentifrice, on the other hand, caused about 0.5 mu m thick p ellicle with tag-like structures to cover the etched enamel. Fine mine ral granules, presumably derived from saliva and minute fragments of e tched crystallites, were precipitated on the enamel surface as a thin layer with the pellicle. These results indicate that daily brushing wi thout dentifrice induces the remineralization of acid-etched enamel by depositing salivary components, while paste brushing will lead to abr asion of the weakened enamel.