Biomechanical degradation of the nano-filled resin-modified glass-ionomer surface.

PURPOSE: To evaluate in the laboratory the roughness (Ra) and micromorphology surface of the nanofilled resin-modified glass-ionomer (Ketac N100) subjected to biomechanical degradation, compared to Vitremer, Ketac Molar Easymix and Fuji IX. METHODS: Specimens obtained from the ionomers were divided into two storage groups (n = 10): relative humidity and S. mutans biofilm (biodegradation). After 7 days, Ra values and micrographs were obtained. Then, the brushing abrasion test (mechanical degradation) was conducted with dentifrice slurry (three-body) and the specimens were reassessed. Data were submitted to repeated measures three-way ANOVA and Tukey tests (P < 0.05). RESULTS: There was significant interaction among the factors: material, storage and abrasion (before/after). Vitremer showed similar Ra values between storage groups, while the other materials presented higher Ra values after biodegradation test. Concerning biomechanical challenge, Ketac N100 presented the lowest Ra values. Ketac Molar Easymix and Fuji IX presented undesirable roughening of their surfaces under the detrimental conditions tested. The eroded aspect after biodegradation with filler exposure after mechanical degradation was evident.

Chemical or microbiological models of secondary caries development around different dental restorative materials.

This study evaluated artificial secondary caries around restorative materials, induced by means of chemical or microbiological models. The following materials were used randomly to restore 130 dental blocks: (1) zinc-oxide eugenol-free temporary filling: Coltosol (Coltène/Whaledent Inc.; n = 30), (2) silver amalgam: Permite C (SDI Limited, n = 20), (3) composite resin: Filtek Z250 (3M ESPE; n = 20), (4) glass-ionomer cement: Fuji II (GC America Inc.; n = 20), (5) resin-modified glass ionomer: Vitremer (3M ESPE; n = 20), and (6) polyacid modified resin: Dyract AP (Dentsply; n = 20). Ten specimens of Group 1 were kept in humidity, and had no carious formation (NC). Ten specimens of each group were submitted to pH cycling (CG, n = 60), and the others were immersed in a medium containing Streptococcus mutans and sucrose (BG, n = 60). Mineral content was determined by microhardness assessment, and lesion depth was measured in polarized light photomicrographs. In the chemical model (CG), mineral content values in the vicinities of restoration were high for Groups 5 (75.7 +/- 11.9), 4 (70.8 +/- 14.2), and NC (95.4 +/- 3.8); intermediate for Groups 1 (55.8 +/- 18.5), 6 (45.6 +/- 11.0), and 2 (44.3 +/- 11.2); and reduced for Group 3 (34.7 +/- 9.7). In the microbiological model (BG), results were similar to CG, although there was less demineralization. The highest lesion depths were found for Groups 3 (182.3 +/- 33.2) in CG and 6 (126.5 +/- 42.8) in BG, when compared to Group 5 (114.6 +/- 26.0 and 56.2 +/- 33.2, respectively). In both models of caries induction, ionomeric materials showed a superior cariostatic effect when compared to the other restorative materials.