Degradation of polymeric restorative materials subjected to a high caries challenge

Objectives. The aim of this study was to evaluate the degradation of different resin filling materials after a caries challenge, by high performance liquid chromatography (HPLC) and contact angle (theta) measurement. Methods. Four different polymeric restorative materials (a resin composite, a polyacid-modified resin composite, an ormocer and a resin-modified glass ionomer cement) were tested. Five samples (30 mm x 6 mm x 2 mm) of each material were formed in a Teflon mold, following the manufacturer's instructions. After pH cycles, the solutions were injected in an HPLC. The theta was obtained, before and after pH cycle, by a goniometer at 60% air humidity and 25 degrees C. A distilled water drop (0.006 ml) was put on the material surface, and after 6 min, 10 measures were obtained at 20 s intervals. Each sample received 4 drops, one at a time, on different areas. Results. HPLC results showed elution of byproducts in all materials. This was greater in the acid medium. Bis-GMA and TEGDMA were detected in TPH Spectrum and Definite residues. Analyses of the contact angle by ANOVA and Student-Neuman-Keuls's test showed that the surfaces of TPH Spectrum, Dyract AP and Definite were altered, except Vitremer (p < 0.05). Significance. All materials tested degraded on a caries simulated medium, suggesting that a great effort should be made to disseminate oral health information, since a high caries challenge environment (low pH) can lead to dental composite degradation, with potential toxic risks to patients. (C) 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.