Effect of Reduced Material Thickness on Fatigue Behavior and Failure Load of Monolithic CAD/CAM PICN Molar Crowns.

PURPOSE: To analyze the effect of material thickness on the fatigue behavior and failure load of monolithic polymer-infiltrated-ceramic-network (PICN) computer-aided design/computer-assisted manufacture (CAD/CAM) crowns. MATERIALS AND METHODS: PICN (VITA Enamic) molar crowns with standard (PICN-ST, 1.5 mm) and reduced (PICN-RED, 1.0 mm) thicknesses were investigated (n = 28). Monolithic zirconia (Z-ST, InCoris TZI) served as control. Failure loads before and after fatigue (1.2 million cycles, 198 N) were evaluated. Data were analyzed pairwise using Wilcoxon rank sum test, and resulting P values were adjusted using the Bonferroni-Holm method, with P < .05 considered significant and a prior power analysis. RESULTS: All crowns survived fatigue. Mean failure loads before and after fatigue (respectively) were as follows: PICN-ST: 1,889 ± 341 N and 2,547 ± 876 N; PICN-RED: 2,119 ± 338 N and 2,367 ± 719 N; and Z-ST 5,141 ± 1,194 N and 2,531 ± 682 N. CONCLUSION: PICN with a reduced thickness of 1 mm appeared to be a reliable CAD/CAM material for posterior crowns.

Non-Mendelian determinant [ISP+] in yeast is a nuclear-residing prion form of the global transcriptional regulator Sfp1.

Four protein-based genetic determinants or prions-[SWI(+)], [MCA], [OCT(+)], and [MOT3(+)]-are recent additions to the list of well-known Saccharomyces cerevisiae prions, [PSI(+)], [URE3], and [PIN(+)]. A rapid expansion of this list may indicate that many yeast proteins can convert into heritable prion forms and underscores a problem of prion input into cellular physiology. Here, we prove that the global transcriptional regulator Sfp1 can become a prion corresponding to the prion-like determinant [ISP(+)] described earlier. We show that SFP1 deletion causes an irreversible [ISP(+)] loss, whereas increased SFP1 expression induces [ISP(+)] appearance. Cells that display the [ISP(+)] phenotype contain the aggregated form of Sfp1. Indeed, these aggregates demonstrate a nuclear location. We also show that the phenotypic manifestation of Sfp1 prionization differs from the manifestation of SFP1 deletion. These properties and others distinguish [ISP(+)] from yeast prions described to date.