Role of Synucleins in Alzheimer’s Disease

Alzheimer’s disease (AD) and Parkinson’s disease (PD) are the most common causes of dementia and movement disorders in the elderly. While progressive accumulation of oligomeric amyloid-β protein (Aβ) has been identified as one of the central toxic events in AD leading to synaptic dysfunction, accumulation of α-synuclein (α-syn) resulting in the formation of oligomers has been linked to PD. Most of the studies in AD have been focused on investigating the role of Aβ and Tau; however, recent studies suggest that α-syn might also play a role in the pathogenesis of AD. For example, fragments of α-syn can associate with amyloid plaques and Aβ promotes the aggregation of α-syn in vivo and worsens the deficits in α-syn tg mice. Moreover, α-syn has also been shown to accumulate in limbic regions in AD, Down’s syndrome, and familial AD cases. Aβ and α-syn might directly interact under pathological conditions leading to the formation of toxic oligomers and nanopores that increase intracellular calcium. The interactions between Aβ and α-syn might also result in oxidative stress, lysosomal leakage, and mitochondrial dysfunction. Thus, better understanding the steps involved in the process of Aβ and α-syn aggregation is important in order to develop intervention strategies that might prevent or reverse the accumulation of toxic proteins in AD

A critical reevaluation of stresses generated during vertical and lateral condensation of gutta-percha in the root canal

The finite element method was used to calculate the stresses in a maxillary canine tooth produced during lateral and vertical condensation. Description of the biological domain to be analyzed, and conversion of the manual operations of the endodontist to realistic load representation are intricate problems which must be overcome before stresses are recovered and plotted. The stresses in dentin are in general of comparable magnitudes during lateral or vertical condensation, but these magnitudes generally remain much below those presented in a previous study. From these calculations it appears that root fractures reported by some investigators may be explained in terms of stress concentrations and local irregularities of the samples tested

The effect of spreader size on fracture resistance of maxillary incisor roots

WOS: 000252260800006PubMed ID: 17916069Aim To assess the effect of spreader size used during cold lateral compaction of gutta-percha on fracture resistance of roots in maxillary incisor teeth. Methodology The crowns of 50 human maxillary incisor teeth having no carious lesions, no fracture or crazing were resected 2 mm coronal to the cemento-enamel junction. The root canals of the teeth were prepared as follows: Group 1: No canal preparation. Group 2: Preparation using the stepback technique to a size 40 master apical file. Group 3: Canal preparation to size 40 and filling with laterally compacted gutta-percha; the first spreader used was equal to size 40. Group 4: Same as group 3 except the first spreader was equal to size 35. Group 5: Same as group 3 except the first spreader was equal to size 25. For each root, a simulated periodontal ligament was prepared. The roots were than mounted in polyester resin and fractured vertically on a universal testing machine (Shimadzu, Tokyo, Japan). The fracture values of teeth were analysed using Kruskal-Wallis and Mann-Whitney U-tests (P = 0.05). Results The uninstrumented group had the highest fracture resistance; instrumented, but unfilled roots, demonstrated the lowest resistance values (P = 0.009). There were no differences between the uninstrumented group and group 5 in which a size 25 spreader was used during filling. Use of spreaders larger than size 25 caused a significant reduction in fracture resistance of roots (P < 0.05). Conclusions Spreader size used during lateral compaction of gutta-percha can affect the fracture resistance of roots in extracted teeth

Additional studies on the distribution of stresses during vertical compaction of gutta-percha in the root canal

Objective This study was designed to investigate the effect of certain pathological alterations of the dental structures (diminishing bone support, internal resorption, root perforation, periapical lesion) on stress distribution during root canal filling procedures by the warm vertical compaction technique