In vitro comparative study on the mechanical behavior of Zirconia and Polyetheretherketone in applied dental sciences

OBJECTIVE: Recently, Zirconia and polyaryletherketone (PEEK) have attracted increasing interest as reliable and safe materials in dental applications, mainly because of their good biomechanical characteristics. The aim of this study was to investigate the response to different loads by prosthetic frameworks for supported fixed partial dentures (FPDs), thus simulating osseointegrated implants. MATERIALS AND METHODS: The specimens were divided into two groups (n= 5 each). Group A: FDPs in zirconia-ceramic; Group B: FDPs in PEEK-composite. These 2 groups were subjected to vertical loads so to evaluate structural deformation; then, they have been analyzed by scanning electron microscopy (SEM) at different magnifications. RESULTS: In tested samples, different types of mechanical failures have been observed. In Zirconia-specimens, chipping is the main failure noticed in this study, mostly in distal margins of the structure. Also, peek-specimens show failure and fracture. CONCLUSIONS: Zirconia and PEEK could be considered both good materials, but several investigations are needed to use these materials as an alternative to metals for fixed partial dentures

In vitro comparative study on the mechanical behavior of Zirconia and Polyetheretherketone in applied dental sciences

OBJECTIVE: Recently, Zirconia and polyaryletherketone (PEEK) have attracted increasing interest as reliable and safe materials in dental applications, mainly because of their good biomechanical characteristics. The aim of this study was to investigate the response to different loads by prosthetic frameworks for supported fixed partial dentures (FPDs), thus simulating osseointegrated implants. MATERIALS AND METHODS: The specimens were divided into two groups (n= 5 each). Group A: FDPs in zirconia-ceramic; Group B: FDPs in PEEK-composite. These 2 groups were subjected to vertical loads so to evaluate structural deformation; then, they have been analyzed by scanning electron microscopy (SEM) at different magnifications. RESULTS: In tested samples, different types of mechanical failures have been observed. In Zirconia-specimens, chipping is the main failure noticed in this study, mostly in distal margins of the structure. Also, peek-specimens show failure and fracture. CONCLUSIONS: Zirconia and PEEK could be considered both good materials, but several investigations are needed to use these materials as an alternative to metals for fixed partial dentures

The two sides of cytokine signaling and glaucomatous optic neuropathy

The mechanistic study of glaucoma pathogenesis has shifted to seeking to understand the effects of immune responses on retinal ganglion cell damage and protection. Cytokines are the hormonal factors that mediate most of the biological effects in both the immune and nonimmune systems. CD4-expressing T helper cells are a major source of cytokine production and regulation. Type 1 helper T (Th1) cells are characterized by the production of proinflammatory cytokines such as interferon-gamma, interleukin (IL)-2, IL-12, IL-23, and tumor necrosis factor-alpha while type 2 helper T (Th2) cells are characterized by the production of IL-4, IL-5, IL-6, and IL-10. The balance of Th1/Th2 cytokine production influences many pathological processes and plays both causative and protective roles in neuron damages. Growing evidence indicates that imbalances of Th1/Th2 cytokine production are involved in neural damage or protection in many neurological diseases. In this review, we discuss the possible roles of Th1/Th2 cytokine production and imbalance of Th1/Th2 cytokines in retina, especially glaucomatous optic neuropathy

The Potential Role of Metalloproteinases in Neurogenesis in the Gerbil Hippocampus Following Global Forebrain Ischemia

BACKGROUND: Matrix metalloproteinases (MMPs) have recently been considered to be involved in the neurogenic response of adult neural stem/progenitor cells. However, there is a lack of information showing direct association between the activation of MMPs and the development of neuronal progenitor cells involving proliferation and/or further differentiation in vulnerable (Cornus Ammoni-CA1) and resistant (dentate gyrus-DG) to ischemic injury areas of the brain hippocampus. PRINCIPAL FINDINGS: We showed that dynamics of MMPs activation in the dentate gyrus correlated closely with the rate of proliferation and differentiation of progenitor cells into mature neurons. In contrast, in the damaged CA1 pyramidal cells layer, despite the fact that some proliferating cells exhibited antigen specific characteristic of newborn neuronal cells, these did not attain maturity. This coincides with the low, near control-level, activity of MMPs. The above results are supported by our in vitro study showing that MMP inhibitors interfered with both the proliferation and differentiation of the human neural stem cell line derived from umbilical cord blood (HUCB-NSCs) toward the neuronal lineage. CONCLUSION: Taken together, the spatial and temporal profiles of MMPs activity suggest that these proteinases could be an important component in neurogenesis-associated processes in post-ischemic brain hippocampus