In vitro toothbrush-dentifrice abrasion of resin-modified glass ionomers.

OBJECTIVES: This study was conducted to compare the rate of abrasive wear and change in surface roughness of resin-modified and conventional acid-base glass ionomers when subjected to toothbrush-dentifrice abrasion.
METHODS: Two resin-modified and two conventional glass ionomers were used. Samples of a high-copper amalgam and a hybrid resin composite were used as reference materials. Specimens of each material were prepared and subjected to toothbrush-dentifrice abrasion using 20,000 strokes of brushing. The amount of vertical loss of material was determined by profilometry (Surfcom-4A, Tokyo-Seimitsu, Tokyo, Japan). The surface characteristics after abrasion were evaluated on secondary electron images by SEM, and the surface hardness (KHN) was also measured for all materials. Data were analyzed by one-way ANOVA (p < 0.05), followed by a multiple comparisons test using LSD (Least-significant difference) at a level of p < 0.05.
RESULTS: The abrasion resistance of resin-modified glass-ionomers was statistically lower for the amalgam and the resin composite reference materials. Statistically lower abrasion resistance and surface hardness were observed for the resin-modified glass ionomers than for their conventional acid-base counterparts when two forms of products from the same manufacturer were compared. SEM observations made after abrasion testing showed a significantly rougher surface for all glass ionomer materials than for the amalgam and the resin composite. SIGNIFICANCE: When comparisons were made between products from the same manufacturers, it was found that in vitro resistance to toothbrush-dentifrice abrasion of the resin-modified glass ionomers is inferior to that of the conventional acid-base glass ionomers. The lower abrasion resistance found in the resin-modified products appears to be related to their lower surface hardness.