Shear bond strengths between alumina-toughened zirconia cores and veneering ceramics and their susceptibility to aging.

OBJECTIVE: To evaluate the shear bond strength (SBS) between alumina-toughened zirconia (ATZ) cores and veneering ceramics, investigate the effect of aging in artificial saliva on SBS and compare it with that of yttria-stabilized tetragonal zirconia polycrystals(Y-TZP). METHODS: Bars of ATZ and Y-TZP were layered with veneering ceramics in accordance to the recommendation of the manufacturer. Half of each group (n = 10) was aged at 134 °C (under 2 bar pressure) in an autoclave for 48 h. Subsequently, all specimens were subjected to shear force in a universal testing machine. The interface and fractured surface of the specimens were evaluated using scanning electron microscopy and X-ray energy dispersive spectroscopy. RESULTS: The initial mean SBS values in MPa±SD were 28.9±8.0 for ATZ and 26.2±7.6 for Y-TZP. After aging, the mean SBS values for ATZ and Y-TZP were 22.9±4.9 MPa and 22.8±6.9 MPa, respectively. Neither the differences between the SBS values of the ATZ and Y-TZP groups nor the influence of aging on all groups were statistically significant. CONCLUSIONS: The SBS between the ATZ core and the veneering ceramics was not affected by aging. The SBS of ATZ to veneering ceramics was not significantly different compared with that of Y-TZP.

Effect of layering feldspathic porcelain on resulting veneer color with aluminum oxide core.

OBJECTIVE: To evaluate the resulting color of veneers affected by adding a layer of veneering porcelain on Procera aluminium oxide core. METHODS: Fifteen aluminium oxide disks were randomized into three groups. Each of five disks was veneered with porcelain of the Vita shade Al, A2 and B4 respectively. The color of the substrate covered with non-veneered disks and the veneered disks was measured separately and the color differences were calculated. RESULTS: Statistically significant differences (P < 0.01) in color coordinates of dark substrate were recorded between the substrate covered by an aluminium oxide disks and the addition of veneering porcelain to aluminium oxide disks. Mean coordinates color difference (DeltaE, DeltaL *, Deltaa *, Deltab *) after adding the three shades of veneering porcelain showed increase from Al (2.311) to A2 (4.313) to B4 (8.778) in DeltaE, decrease from Al (-1.530) to A2 (-3.369) and B4 (-3.358) in DeltaL *, and increase from Al (-1.440) to A2 (2.198) to B4 (7.955) in Deltab *. The direction of the color modification correlated with values obtained from the liberation. The resulting color was also affected by the color of the underlying structure. CONCLUSION: This study illustrates that color of aluminium oxide shell could be modified with feldspathic veneering porcelain, which may be used by practitioners to alter the esthetic outcome of porcelain veneers.

A comparison of the marginal fit of In-Ceram, IPS Empress, and Procera crowns.

The in vitro marginal fit of three all-ceramic crown systems (In-Ceram, Procera, and IPS Empress) was compared. All crown systems were significantly different from each other at P = 0.05. In-Ceram exhibited the greatest marginal discrepancy (161 microns), followed by Procera (83 microns), and IPS Empress (63 microns). There were no significant differences among the various stages of the crown fabrication: core fabrication, porcelain veneering, and glazing. The facial and lingual margins exhibited significantly larger marginal discrepancies than the mesial and distal margins.