IN-VITRO TOOTHBRUSH-DENTIFRICE ABRASION OF RESIN-MODIFIED GLASS IONOMERS

Objectives. This study was conducted to compare the rate of abrasive w ear and change in surface roughness of resin-modified and conventional acid-base glass ionomers when subjected to toothbrush-dentifrice abra sion. Methods. Two resin-modified and two conventional glass ionomers were used. Samples of a high-copper amalgam and a hybrid resin composi te were used as reference materials. Specimens of each material were p repared and subjected to toothbrush-dentifrice abrasion using 20,000 s trokes of brushing. The amount of vertical loss of material was determ ined by profilometry (Surfcom-4A, Tokyo-Seimitsu, Tokyo, Japan). The s urface characteristics after abrasion were evaluated on secondary elec tron images by SEM, and the surface hardness (KHN) was also measured f or all materials. Data were analyzed by one-way ANOVA (p < 0.05), foll owed by a multiple comparisons test using LSD (Least-significant diffe rence) at a level of p < 0.05. Results. The abrasion resistance of res in-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 o bservations 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 prod ucts from the same manufacturers, it was found that in vitro resistanc e to toothbrush-dentifrice abrasion of the resin-modified glass ionome rs is inferior to that of the conventional acid-base glass ionomers. T he lower abrasion resistance found in the resin-modified products appe ars to be related to their lower surface hardness.