Effect of toothbrush-dentifrice abrasion on the surface roughness of acid-base restorative cements

Objectives: This study investigated the effect of toothbrush-dentifrice abrasion on the surface roughness of acid-base restorative cements: Fuji IX [FIX], Fuji II LC-improved [FII LC], Diamond Carve [DC], and an experimental glass ionomer [EX]. Methods: each material was mixed according to manufactures’ instructions and placed in polyvinylsiloxane wells [20 x 10 x 1mm]. Samples were clamped between acetate sheets and steel plates for 1 hour at 37oC. Specimens were then stored in deionised water at 37oC for 1, 7, 30, 90, 180 and 270 days. Four specimens of each material were prepared for each time interval. Abrasion testing was carried out in a toothbrush abrasion machine using loads of 200 g applied to the toothbrush head. Surface roughness values were obtained prior to abrasion using a laser profilometer and after 20,000 reciprocal strokes [at 100 strokes per minute]. Before testing, 50 ml of slurry [water/toothpaste] was dispersed on each specimen. Two specimens were randomly selected for SEM observation for each storage time and material. The data was analysed using Mann-Whitney non-parametric statistics. Results: all materials showed increased surface roughness after toothbrush-dentifrice abrasion. For materials EX, DC and FIX the surface of the specimens abraded after 270 days storage was significantly rougher than after 1 day storage (p<0.05). No difference in surface roughness was noted for FII LC between beginning and end of the study. Increased roughness was however observed during the experimental period for this material. While there were changes SEM analysis showed that the surface roughening was caused by preferential wear of the matrix that exposed irregular shaped glass particles. Conclusions: it was concluded that toothbrush-dentifrice abrasion results in surface deterioration of all the materials. For conventional glass ionomer cements, the abraded surface was rougher for the specimens stored for longer periods. The State of São Paulo Research Foundation (FAPESP) - Grant 1998/5517-0.