PURPOSE: To evaluate the wear of computer-aided design/computer-aided manufacturing (CAD-CAM) dental ceramic materials opposed by enamel as a function of increased chewing forces. MATERIALS AND METHODS: The enamel cusps of healthy human third molar teeth (n = 40) opposed by materials from CAD-CAM dental ceramic groups (n = 10), including Vita Enamic® (ENA), a polymer-infiltrated ceramic network (PICN); GC Cerasmart® (CERA), a resin nanoceramic; Celtra® Duo (DUO), a zirconia-reinforced lithium silicate (ZLS) ceramic; and IPS e.max ZirCAD (ZIR), a polycrystalline zirconia, were exposed to chewing simulation (1,200,000 cycles; 120 N load; 1 Hz frequency; 0.7 mm lateral and 2 mm vertical motion). The wear of both enamel cusps and materials was quantified using a 3D laser scanner, and the wear mechanisms were evaluated by scanning electron microscopy (SEM). The results were analysed using Welch ANOVA and Kruskal Wallis test (α = .05). RESULTS: ZIR showed lower volume loss (0.02 ± 0.01 mm3) than ENA, CERA and DUO (P = .001, P = .018 and P = .005, respectively). The wear of cusp/DUO [0.59 mm3 (0.50-1.63 mm3)] was higher than cusp/CERA[0.17 mm3 (0.04-0.41 mm3)] (P = .007). ZIR showed completely different wear mechanism in SEM. CONCLUSION Composite structured materials such as PICN and ZLS ceramic exhibit more abrasive effect on opposing enamel due to their loss against wear, compared to uniform structured zirconia. The resin nanoceramic causes the lowest enamel wear thanks to its flexible nano-ceramic microstructure. While zirconia appears to be an enamel-friendly material in wear volume loss, it can cause microstructural defects of enamel.

PURPOSE: To evaluate the effects of hydrofluoric acid etching and Er,Cr:YSGG laser irradiation on the shear bond strength of resin cement to lithium disilicate ceramic. MATERIALS AND METHODS: Fifty-five ceramic blocks (5 mm x 5 mm x 2 mm) were fabricated and embedded in acrylic resin. Their surfaces were finished with 1000-grit silicon carbide paper. The blocks were assigned to five groups: 1) 9.5% hydrofluoric-acid etching for 60 s; 2-4), 1.5-, 2.5-, and 6-W Er,Cr:YSGG laser applications for 60 seconds, respectively; and 5) no treatment (control). One specimen from each group was examined using scanning electron microscopy. Ceramic primer (Rely X ceramic primer) and adhesive (Adper Single Bond) were applied to the ceramic surfaces, followed by resin cement to bond the composite cylinders, and light curing. Bonded specimens were stored in distilled water at 37degrees C for 24 hours. Shear bond strengths were determined by a universal testing machine at 1 mm/min crosshead speed. Data were analyzed using Kruskal-Wallis and Mann-Whitney U-tests (alpha=0.05). RESULTS: Adhesion was significantly stronger in Group 2 (3.88 +/- 1.94 MPa) and Group 3 (3.65 +/- 1.87 MPa) than in Control group (1.95 +/- 1.06 MPa), in which bonding values were lowest (P<.01). No significant difference was observed between Group 4 (3.59 +/- 1.19 MPa) and Control group. Shear bond strength was highest in Group 1 (8.42 +/- 1.86 MPa; P<.01). CONCLUSION: Er,Cr:YSGG laser irradiation at 1.5 and 2.5 W increased shear bond strengths between ceramic and resin cement compared with untreated ceramic surfaces. Irradiation at 6 W may not be an efficient ceramic surface treatment technique.
Adhesives ; Carbon Compounds, Inorganic ; Ceramics ; Collodion ; Dental Porcelain ; Hydrofluoric Acid ; Light ; Lithium ; Microscopy, Electron, Scanning ; Resin Cements ; Silicon Compounds ; Water