Evaluation of regional bond strength of resin cement to endodontic surfaces

The purpose of this study was to test the feasibility of adapting a new microtensile testing technique to measure resin cement bond strengths to the cervical, middle, and apical thirds of root canals. Post spaces were created in extracted human teeth, and the roots were ground flat on one side to expose the canal and permit ideal placement of one of two resin cements (Panavia 21 or C&B Metabond). After 48 h of storage, serial 1-mm-thick cross-sections were cut to create 6-10 specimens per root. The first three specimens were from the cervical third, the next three were from the middle third, and the last three were from the apical third of the root. Each 1 x 1 x 8 mm specimen was pulled to failure in a miniature testing machine. The results indicated that both resin cements produced high bond strengths (12-23 MPa), and that bond strengths to the apical third were significantly higher (p < 0.05) than to the cervical or middle third with either cement. This new method shows promise for evaluating resin bond strengths within root canals.     

Erosion of deciduous and permanent dental hard tissue in the oral environment

OBJECTIVES: The objectives of this study were two-fold: (1) to determine (by surfometry) loss of deciduous and permanent enamel and dentine following consumption of a single low pH orange drink for 15days; and (2) to determine (by surfometry) loss of deciduous and permanent enamel and dentine following consumption of the product 2 versus 4 times per day for 15days. METHODS: Sixteen healthy volunteers participated in a single centre, single blind, 2-phase crossover study, conducted according to Good Clinical Practice, and employing the validated model described by West and co-workers (Journal of Dentistry 1998; 26:329-335). RESULTS: In all tissues, erosion was progressive over time, the pattern being more linear in enamel than in dentine. In general, erosion of deciduous enamel was greater than that of permanent enamel, though this difference was significant only for those specimens exposed to 4 drinks per day. Conversely, erosion of dentine was generally greater in the permanent tissue, though differences rarely reached conventional levels of statistical significance. Increasing frequency of consumption resulted in increased loss of tissue, but this difference was neither proportional nor consistently statistically significant. CONCLUSIONS: It is concluded that statistically significant differences in susceptibility of deciduous and permanent enamel to erosion appear to emerge over time and with increasing frequency of consumption. This is of importance clinically given the reduced dimensions of the deciduous dentition and the element of 'abuse' of soft drinks by the child population. Further development of soft drinks with low erosive potential is recommended.     

Spontaneous pneumomediastinum associated with orthognathic surgery. A case report.

Numerous articles identifying pneumomediastinum as an immediate complication of dental and oral surgical procedures have been published. A patient who developed a spontaneous pneumomediastinum as a delayed complication, apparently not directly related to the surgical procedure, is presented in this report.     

Evidence that the LRRK2 ROC domain Parkinson's disease‐associated mutants A1442P and R1441C exhibit increased intracellular degradation

Mutations in the leucine‐rich repeat kinase 2 (lrrk2) gene are the leading genetic cause of Parkinson's disease (PD). In characterizing the novel ROC domain mutant A1442P, we compared its steady‐state protein levels, propensity to aggregate, and toxicity with the pathogenic R1441C mutant and wild‐type (WT) LRRK2. Mutant (R1441C and A1442P) and WT LRRK2 fused to green fluorescent protein (GFP) and FLAG were transiently expressed in HEK293 cells using plasmid constructs. Western analysis and fluorescence microscopy consistently demonstrated lower mutant LRRK2 protein levels compared with WT. A time‐course expression study using flow cytometry showed that WT LRRK2 expression increased initially but then plateaued by 72 hr. Conversely, R1441C and A1442P mutant expression attained 85% and 74% of WT levels at 24 hr but fell to 68% and 55% of WT levels by 72 hr, respectively. We found that proteasome inhibition markedly increased mutant LRRK2 to levels approaching those of WT. Taken together, our findings reveal increased intracellular degradation for both mutants. Furthermore, the impact of mutant and WT LRRK2 expression on HEK293 cell viability was assessed under normative and oxidative (hydrogen peroxide) conditions and found not to differ. Expression of WT and mutant LRRK2 protein gave rise to intracellular aggregates of similar appearance and cellular localization. In summary, we provide evidence that the novel A1442P mutant and the previously investigated R1441C pathogenic mutant exhibit increased intracellular degradation, a property reportedly demonstrated for the pathogenic LRRK2 kinase domain mutant I2020T. © 2013 Wiley Periodicals, Inc.     

鼻咽癌患者淋巴细胞近端着丝粒染色体随体联合频率的分析

本文对60例鼻咽癌患者用银染及非银染方法比较分析了近端着丝粒染色体随体联合的频率(SAs及Ag-AA),发现每细胞平均出现的SAs及Ag-AA分别为0.55和1.29(P<0.01)。D、G组染色体在随体联合中的比例分别为DSAf0.620及0.597,GSAf为0.380及0.403,具有随机性。G显带证实13、14、21号染色体更多地参与随体联合。