Hydrolytic degradation of composite resins: effects on the microhardness

Abstract

The purpose of this investigation was to evaluate the microhardness of two laboratory-processed composites (Artglass; belleGlass) and two direct placement composites (Filtek Z250; Alert), after aging in distilled water. Twenty cylinders (8 mm diameter; 2 mm height) per tested material were prepared and stored in 10 ml of distilled water. Five Knoop hardness measurements were made on the surface of the specimens with a Miniload Hardness Tester under a load of 50 g for 30 s at 10 min, 24 h, 30 and 90 days. Statistical analysis was perfomed using two-way ANOVA, followed by a SNK multiple comparison test (p < 0.05). The analysis showed statistically significant difference among hardness means recorded at the different aging time and the tested materials. It may be concluded that all materials presented hydrolytic degradation due to aging in aqueous environment

Effects of 6 Months of Aging in Water on Hardness and Surface Roughness of Two Microhybrid Dental Composites

“…The present results reveal that both composites presented significant surface softening after the 6‐month storage period, corroborating previous investigations 7,19,20 . This can be explained by water serving as a plasticizing molecule within the composite matrix 7 .…”

“…Lloyd 18 observed no significant changes in fracture toughness of composites after extended storage. Conversely, Ferracane et al 7 described reduction of up to 30% in surface hardness and in fracture toughness of composites aged in water, which is in line with other investigations 19,20 . Furthermore, little is known about the influence of aging on the surface smoothness of resin‐based restoratives.…”

“…The present results reveal that both composites presented significant surface softening after the 6-month storage period, corroborating previous investigations. 7,19,20 This can be explained by water serving as a plasticizing molecule within the composite matrix. 7 It is well-recognized that the water uptake process is the main factor responsible for the appearance and propagation of interfacial debonding, matrix cracking, superficial flaws, and filler particle dislodgment in the course of time.…”

“…Conversely, Ferracane et al 7 described reduction of up to 30% in surface hardness and in fracture toughness of composites aged in water, which is in line with other investigations. 19,20 Furthermore, little is known about the influence of aging on the surface smoothness of resin-based restoratives. Munack et al 20 reported that polyacid-modified composites displayed low surface roughness values, varying between 0.03 and 0.08 μm, throughout a 12-month storage period, even though a decrease in surface hardness of up to 32% was detected.…”

Changes in Degree of Conversion and Microhardness of Dental Resin Cements

“…[11][12][13] In addition, the specimen storage condition employed in the current study (dark, dry conditions at 37°C) was not the same as simulating an intraoral condition (water storage), although influence on the DC and microhardness data did not seem to be significant during the test period for this study. [27][28] Finally, only six commercially available resin cement products were tested in this study, and more need to be examined.…”