Stress distributions in maxillary central incisors restored with various types of post materials and designs.

Different dental post designs and materials affect the stability of restoration of a tooth. This study aimed to analyse and compare the stability of two shapes of dental posts (parallel-sided and tapered) made of five different materials (titanium, zirconia, carbon fibre and glass fibre) by investigating their stress transfer through the finite element (FE) method. Ten three-dimensional (3D) FE models of a maxillary central incisor restored with two different designs and five different materials were constructed. An oblique loading of 100 N was applied to each 3D model. Analyses along the centre of the post, the crown-cement/core and the post-cement/dentine interfaces were computed, and the means were calculated. One-way ANOVAs followed by post hoc tests were used to evaluate the effectiveness of the post materials and designs (p=0.05). For post designs, the tapered posts introduced significantly higher stress compared with the parallel-sided post (p<0.05), especially along the centre of the post. Of the materials, the highest level of stress was found for stainless steel, followed by zirconia, titanium, glass fibre and carbon fibre posts (p<0.05). The carbon and glass fibre posts reduced the stress distribution at the middle and apical part of the posts compared with the stainless steel, zirconia and titanium posts. The opposite results were observed at the crown-cement/core interface.

Thiazolidinedione toxicity to isolated hepatocytes revealed by coherent multiprobe fluorescence microscopy and correlated with multiparameter flow cytometry of peripheral leukocytes.

Thiazolidinediones (TZDs) are effective for the treatment of adult-onset insulin-resistant diabetes. Unfortunately, TZDs are associated with sporadic hepatic dysfunction that is not predictable from experimental animal studies. We investigated the response of isolated rat and human hepatocytes to various TZDs using biochemical assays, coherent multiprobe fluorescence microscopy and flow cytometric analyses. The results identified direct effects of TZD on mitochondria from live human and rodent hepatocytes. The multiprobe fluorescence assays showed disruption of mitochondrial activity as an initiating event followed by increased membrane permeability, calcium influx and nuclear condensation. Other TZD-related cellular effects were increased hepatic enzyme leakage, decreased reductive metabolism and cytoplasmic adenosine triphosphate depletion. Mitochondrial effects were similar in cryopreserved hepatocytes from diabetic or non-diabetic donors. Peripheral blood mononuclear cells (PBMCs) had baseline mitochondrial energetics and metabolism comparable with isolated hepatocytes. Mitochondrial effects in isolated hepatocytes were found in human PBMCs exposed to the TZDs. The relative potency of TZDs for causing hepatocyte and PBMC effects was troglitazone > pioglitazone > rosiglitazone. These studies clearly demonstrated that hepatic alterations in vitro are characteristic of TZDs, with only quantitative differences in subcellular organelle dysfunction. Monitoring mitochondrial function in isolated PBMCs may be beneficial in diabetics undergoing TZD therapy.