In vitro analysis of the fracture resistance of CAD-CAM monolithic zirconia molar crowns with different occlusal thickness

Objectives: To compare the fracture resistance and mode of failure of CAD-CAM monolithic zirconia crowns with different occlusal thickness. Material and methods: Forty CAD-CAM monolithic zirconia crowns with different occlusal thickness were randomly distributed into 4 experimental groups: 2.0 mm (group 1), 1.5 mm (group 2), 1.0 mm (group 3) and 0.5 mm (group 4). The restorations were cemented onto human molars with a self-adhesive resin cement. The specimens were loaded until fracture; the fracture resistance and mode of failure were recorded. The data were statistically analyzed with the one-way ANOVA followed by the Fisher's Exact test with Bonferroni's correction (p=0.05). Results: The fracture resistance values of all the specimens exceeded the maximum physiological occlusal loads in molar regions. All the crowns showed cohesive microcracks of the zirconia core; only 1 crown with a thickness of 0.5 mm was interested by a complete fracture. Conclusions: The occlusal thickness of CAD-CAM monolithic zirconia crowns did not influence either the fracture resistance and the mode of failure of the restorations; the occlusal thickness of CAD-CAM monolithic zirconia crowns can be reduced up to a lower bound of 0.5 mm keeping a sufficient strength to withstand occlusal loads; CAD-CAM monolithic zirconia crowns showed sufficient fracture resistance to be used in molar regions, even in a thin configuration (0.5 mm)

Evidence for widespread hydrated minerals on asteroid (101955) Bennu

Early spectral data from the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission reveal evidence for abundant hydrated minerals on the surface of near-Earth asteroid (101955) Bennu in the form of a near-infrared absorption near 2.7 µm and thermal infrared spectral features that are most similar to those of aqueously altered CM-type carbonaceous chondrites. We observe these spectral features across the surface of Bennu, and there is no evidence of substantial rotational variability at the spatial scales of tens to hundreds of metres observed to date. In the visible and near-infrared (0.4 to 2.4 µm) Bennu’s spectrum appears featureless and with a blue (negative) slope, confirming previous ground-based observations. Bennu may represent a class of objects that could have brought volatiles and organic chemistry to Earth

The dynamic geophysical environment of (101955) Bennu based on OSIRIS-REx measurements

The top-shaped morphology characteristic of asteroid (101955) Bennu, often found among fast-spinning asteroids and binary asteroid primaries, may have contributed substantially to binary asteroid formation. Yet a detailed geophysical analysis of this morphology for a fast-spinning asteroid has not been possible prior to the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission. Combining the measured Bennu mass and shape obtained during the Preliminary Survey phase of the OSIRIS-REx mission, we find a notable transition in Bennu’s surface slopes within its rotational Roche lobe, defined as the region where material is energetically trapped to the surface. As the intersection of the rotational Roche lobe with Bennu’s surface has been most recently migrating towards its equator (given Bennu’s increasing spin rate), we infer that Bennu’s surface slopes have been changing across its surface within the last million years. We also find evidence for substantial density heterogeneity within this body, suggesting that its interior is a mixture of voids and boulders. The presence of such heterogeneity and Bennu’s top shape are consistent with spin-induced failure at some point in its past, although the manner of its failure cannot yet be determined. Future measurements by the OSIRIS-REx spacecraft will provide insight into and may resolve questions regarding the formation and evolution of Bennu’s top-shape morphology and its link to the formation of binary asteroids

Adattamento interno e nanoinfiltrazione di corone singole in disilicato di litio con preparazione a finire e differenti cementi da fissaggio.

Scopo Lo studio si è proposto di analizzare in vitro la nanoinfiltrazione e l’adattamento interno di corone singole in zirconia. Materiali e Metodi Incisivi mandibolari sani sono stati preparati protesicamente per corone singole in zirconia e suddivisi in maniera randomizzata in 4 gruppi sperimentali in base al cemento utilizzato. I campioni sono stati processati per analisi della nanoinfiltrazione marginale e, successivamente, osservati per l’adattamento interno con stereomicroscopio e microscopio elettronico a scansione. Risultati Il valore medio di adattamento interno delle corone in zirconia è stato di 54,06 μ; nessuna corona ha presentato fratture marginali. Conclusioni L’utilizzo delle preparazioni a finire con corone singole in zirconia può essere consigliato nella pratica clinica

In vivo longitudinal study of rodent skeletal muscle atrophy using ultrasonography

Muscle atrophy is a widespread ill condition occurring in many diseases, which can reduce quality of life and increase morbidity and mortality. We developed a new method using non-invasive ultrasonography to measure soleus and gastrocnemius lateralis muscle atrophy in the hindlimb-unloaded rat, a well-Accepted model of muscle disuse. Soleus and gastrocnemius volumes were calculated using the conventional truncated-cone method and a newly-designed sinusoidal method. For Soleus muscle, the ultrasonographic volume determined in vivo with either method was linearly correlated to the volume determined ex-vivo from excised muscles as muscle weight-To-density ratio. For both soleus and gastrocnemius muscles, a strong linear correlation was obtained between the ultrasonographic volume and the muscle fiber cross-sectional area determined ex-vivo on muscle cryosections. Thus ultrasonography allowed the longitudinal in vivo evaluation of muscle atrophy progression during hindlimb unloading. This study validates ultrasonography as a powerful method for the evaluation of rodent muscle atrophy in vivo, which would prove useful in disease models and therapeutic trials

Laparoscopic treatment of blunt splenic injuries: initial experience with 11 patients.

Abstract Background: Nonoperative treatment of splenic injuries is the current standard of care for hemodynamically stable patients. However, uncertainty exists about its efficacy for patients with major polytrauma, a high Injury Severity Score (ISS), a high grade of splenic injury, a low Glasgow Coma Score (GCS), and important hemoperitoneum. In these cases, the videolaparoscopic approach could allow full abdominal cavity investigation, hemoperitoneum evacuation with autotransfusion, and spleen removal or repair. Methods: This study investigated 11 hemodynamically stable patients with severe politrauma who underwent emergency laparoscopy. The mean ISS was 29.0 ± 3.9, and the mean GCS was 12.1 ± 1.6. A laparoscopic splenectomy was performed for six patients, whereas splenic hemostasis was achieved for five patients, involving one electrocoagulation, one polar resection, and three polyglycolic mesh wrappings. Results: The average length of the operation was 121.4 ± 41.6 min. There were two complications (18.2%), with one conversion to open surgery (9.1%), and no mortality. Conclusions: Laparoscopy is a safe, feasible, and effective procedure for evaluation and treatment of hemodynamically stable patients with splenic injuries for whom nonoperative treatment is controversial