Comparative Evaluation of Mechanical Properties and Wear Ability of Five CAD/CAM Dental Blocks.

This study compares the mechanical properties and wear ability of five CAD/CAM (computer-aided design/computer-aided manufacturing) millable dental blocks. All the discs, including Amber Mill Hybrid, Vita Enamic, Katana Avencia, Lava Ultimate, and Amber Mill, were cut in dimensions of 1.2 mm in thickness and 12 mm in diameter, polished to a machined surface, and immersed in distilled water for seven days. Vickers hardness was measured and the indentations were observed using microscope. The discs were brushed under a 150 g load. Mean surface roughness (Ra) and topography were determined after 100,000 cycles. Finally the biaxial flexure strength of the discs was measured and the broken surfaces were observed using scanning electron microscopy (SEM). The data was subjected to Weibull analysis. All data were analyzed by one-way analysis (ANOVA). The results of Vickers hardness are shown as: Amber Mill > Vita Enamic > Amber Mill Hybrid > Lava Ultimate > Katana Avencia. Katana Avencia showed the highest volume percentage reduction and the roughest surface after toothbrushing. The biaxial flexural strength is shown as: Amber Mill > Katana Avencia > Lava Ultimate > Amber Mill Hybrid > Vita Enamic. All the tested materials exhibited varying degrees of mass loss and surface roughness. The properties of the composite materials are related to the filler content, filler volume, and polymerization methods.

Comparative evaluation of the mechanical properties of CAD/CAM dental blocks.

This study compares the mechanical properties of commercially available CAD/CAM (Computer-Aided Design/Computer-Aided Manufacturing) millable dental blocks including Vita Enamic, Lava Ultimate, and MAZIC Duro. All the discs were cut in dimension of 1.2 mm in thickness and 12 mm in diameter, ground up to #1200 Sic papers and polished. The biaxial flexure strength of the ceramic discs was measured after thermocycling treatment and the broken surfaces were observed using scanning electron microscopy (SEM). The discs were brushed using a toothbrush testing machine under a 150 g load. Surface roughness and morphology were determined after toothbrushing cycles. Finally, the friction and wear behavior of the materials against an opposing tooth were studied using a reciprocating pin-on-plate test configuration. The vertical loss of dental cusp was measured, and the surface image was examined using field emission scanning electron microscopy (FE-SEM). The biaxial flexural strength data were subjected to Weibull analysis. To compare the significance between the groups, all data were analyzed by one-way analysis (ANOVA). The biaxial flexural strength of the Lava Ultimate and MAZIC Duro materials is significantly higher than that of Vita Enamic. In addition, Lava Ultimate and MAZIC Duro exhibited significantly smoother surfaces than that of Vita Enamic after toothbrushing. Lava Ultimate and MAZIC Duro also showed less wear to the opposing tooth than that of Vita Enamic. In addition, Lava Ultimate possesses more suitable mechanical properties than the Vita Enamic and Mazic Duro for use in oral clinical prosthesis.

Effect of finishing condition on fracture strength of monolithic zirconia crowns.

This study was to evaluate the load bearing capacity of monolithic dental zirconia crowns, and the effect of surface finishing on fracture strength. (1) The zirconia plates were divided into 5 groups and polished by various types of polishing bur, every specimen was analyzed by surface roughness testing, and X-ray diffraction (XRD). (2) The zirconia crowns were classified into 4 groups corresponding to different surface treatments and thickness. All the crowns were cemented and subjected to a load of 7 kg for 5 min. Stored in distilled water at 37°C for 24 h. Observe the typical surface using field emission scanning electron microscopy (FE-SEM). The cycling and fracture tests were carried out. The data was statistically analyzed. The groups had better fracture strength after polishing. This suggests the monoclinic phase can be eliminated by optimizing the polishing process. Moreover, the fracture strength increased with occlusal thickness (p<0.05).