Cement Choice and the Fatigue Performance of Monolithic Zirconia Restorations.

This study investigated the fatigue failure load of simplified monolithic yttria partially stabilized zirconia polycrystal restorations cemented to a dentin-like substrate using different luting systems. Disc-shaped ceramic (Zenostar T, 10 mm Ø × 0.7 mm thick) and dentin-like substrate (10 mm Ø × 2.8 mm thick) were produced and randomly allocated into eight groups, without or with thermocycling (TC=5-55°C/12,000×): "cement" (RelyX Luting 2 - glass ionomer cement [Ion], [Ion/TC]; RelyX U200 - self-adhesive resin cement [Self], [Self/TC]; Single Bond Universal+RelyX Ultimate - MDP-containing adhesive + resin cement [MDPAD + RC], [MDP-AD + RC/TC]; ED Primer II+Panavia F 2.0 - Primer + MDP-containing resin cement [PR + MDP-RC], [PR + MDP-RC/TC])). Each luting system was used as recommended by the manufacturer. Staircase methodology (20 Hz; 250,000 cycles) was applied for obtaining the fatigue failure loads. Fractographic characteristics were also assessed. At baseline, the Ion group presented the lowest fatigue load, although it was statistically similar to the Self group. The resin-based cement systems presented the highest fatigue performance, with the Ion group being only statistically equal to the Self group. Thermocycling influenced the groups differently. After aging, the MDP-AD + RC presented the highest mean, followed by the PR + MDP-RC and Self groups, while the Ion group had the lowest mean. Fractographic analysis depicted all failures as radial cracks starting at the zirconia intaglio surface. The luting system with MDP-containing adhesive applied prior to the resin cement presented the highest fatigue failure load after aging, presenting the best predictability of stable performance. Despite this, monolithic zirconia presents high load-bearing capability regardless of the luting agent.

Phenotyping OSAH patients during wakefulness.

PURPOSE: Although currently there are simplified methods to measure the pathophysiological traits that stimulate the occurrence and maintenance of obstructive sleep apnea-hypopnea (OSAH), they remain difficult to implement in routine practice. This pilot study aimed to find a simpler daytime approach to obtain a meaningful, similar pathophysiological phenotypic profile in patients with OSAH. METHODS: After obtaining diagnostic polygraphy from a group of consecutive patients with OSAH, we performed the dial-down CPAP technique during nocturnal polysomnography and used it as reference method. This allowed assessment of upper airway collapsibility, loop gain (LG), arousal threshold (AT), and upper airway muscle gain (UAG). We compared these results with a daytime protocol based on negative expiratory pressure (NEP) technique for evaluating upper airway collapsibility and UAG, on maximal voluntary apnea for LG, and on clinical predictors for AT. RESULTS: Of 15 patients studied, 13 patients with OSAH accurately completed the two procedures. There were strong (all r2 > 0.75) and significant (all p < 0.001) correlations for each phenotypic trait between the measurements obtained through the reference method and those achieved during wakefulness. CONCLUSION: It is possible to phenotype patients with OSAH from a pathophysiological point of view while they are awake. Using this approach, cutoff values corresponding to those usually adopted using the reference method can be identified to detect abnormal traits, achieving profiles similar to those obtained through the dial-down CPAP technique.

Fatigue Failure Load of a Bonded Simplified Monolithic Feldspathic Ceramic: Influence of Hydrofluoric Acid Etching and Thermocycling.

OBJECTIVE: To evaluate the effect of hydrofluoric acid (HF) etching and thermocycling (Tc) on fatigue failure load of feldspathic ceramic restorations cemented with two resin cements. METHODS: Disc-shaped feldspathic ceramic (Vitablocs Mark II; Ø=10 mm, 1.0-mm thick) and G10 epoxy resin (Ø=10 mm, 2.5-mm thick) specimens were made and randomly allocated considering three factors: ceramic etching (ie, with vs without 10% HF plus silane application), resin cement (ie, self-adhesive [RelyX U200; U200] or conventional [Multilink Automix; MA]), and Tc (ie, with vs without 5-55°C/12,000 cycles). Adhesive cementation followed each manufacturer's instructions. The fatigue test (n=20) was based on the staircase approach (250,000 cycles; 20 Hz). Contact angle, surface topography, and fractography analysis were also executed. Specific statistical tests were employed for each outcome (α=0.05). RESULTS: The interaction of HF and Tc factors decreased the fatigue resistance for both cements (U200 542.63>U200/HF-Tc 495.00; MA 544.47>MA/HF-Tc 506.84). Comparing the cements associated with HF or Tc, there was statistical superiority for MA (U200-Tc 537.37