Torsional and bending resistance of WaveOne Gold, Reciproc and Twisted File Adaptive instruments.

AIM: To compare the torsional and bending resistance of WaveOne Gold (Dentsply Tulsa Dental Specialties, Tulsa, OK, USA), Reciproc (VDW, Munich, Germany) and Twisted File Adaptive (Axis/SybronEndo, Orange, CA, USA) instruments. METHODOLOGY: Torsional strength of WaveOne Gold primary size 25, .07 taper, Reciproc size 25, .08 taper and Twisted File Adaptive M-L1 size 25, .08 taper was measured by fastening the apical 3 mm of the instrument firmly and applying a constant rotation at 2 rpm to the instrument using a torsiometer. The fractured instruments were examined using a scanning electron microscope (SEM). The bending resistance of the instruments was measured using the cantilever bending test. The data were statistically analysed using one-way analysis of variance (anova) and Tukey post hoc tests. The statistical significance level was set at P < 0.05. RESULTS: WaveOne Gold had a significantly higher torsional resistance than Reciproc and Twisted File Adaptive (P < 0.001). Reciproc had a significantly higher torsional resistance than Twisted File Adaptive (P < 0.001). WaveOne Gold had a significantly lower resistance to bend than Reciproc and Twisted File Adaptive (P < 0.001). There was a significant difference in bending resistance between Reciproc and Twisted File Adaptive instruments (P < 0.001). SEM of the fracture cross-sectional surface displayed the classical features of torsional failure, including fibrous dimple marks near the centre of rotation and circular abrasion marks. CONCLUSIONS: WaveOne Gold exhibited higher resistance to torsional stress and flexibility compared with Reciproc and Twisted File Adaptive instruments. Torsional resistance and flexibility properties of the instruments could be affected by the alloy from which the instrument is manufactured and different cross-sectional design.

A laboratory evaluation of the antibacterial and cytotoxic effect of Liquorice when used as root canal medicament.

AIM: To evaluate the antibacterial and cytotoxic effects of Liquorice as a root canal medicament and to compare its action to the commonly used root canal medicament calcium hydroxide Ca(OH)(2). METHODOLOGY: The antibacterial effect of Liquorice and Ca(OH)(2) either separately or in combination was investigated against Enterococcus faecalis. Agar-well diffusion methods, broth microdilution tests and biofilm susceptibility assays were used to determine the antibacterial activity. Human periodontal ligament fibroblast tissue culture was used to assess the cytotoxicity of the preparations under investigation. RESULTS: Liquorice extract either by itself or in combination with Ca(OH)(2) had a significant inhibitory effect against Enterococcus faecalis compared with that of Ca(OH)(2) alone. The use of Liquorice extract followed by Liquorice/Ca(OH)(2) mixture retained significantly more viable periodontal ligament cells than Ca(OH)(2) , which had a strong lethal effect on the cells. CONCLUSION: Liquorice extract either separately or as Liquorice/Ca(OH)(2) mixture had a potent bactericidal effect against Enterococcus faecalis and retained compatibility with fibroblasts in tissue culture compared to the commonly used root canal medicament Ca(OH)(2).

Effect of hyperbaric oxygen on striatal metabolites: a microdialysis study in awake freely moving rats after MCA occlusion.

We have shown that hyperbaric oxygen (HBO) reduced cerebral infarction in rat middle cerebral artery occlusion model (MCAO). The present study was undertaken to evaluate the effect of HBO on ischemic striatal metabolites at different times after MCAO and reperfusion. A rat MCAO model was produced via the intraluminal filament method. After 2 h of occlusion the suture was removed and reperfusion was allowed. The rats were sacrificed at 24 h after reperfusion. HBO treatment was administered by putting rats in the HBO chamber at 3 atmospheres absolute (ATA) HBO for 1 h. Glucose, lactate, pyruvate, and glutamate in striatal extracellular fluid were collected and measured by a microdialysis system at 7, 10, and 24 h after reperfusion. Glucose, pyruvate and glutamate concentrations were increased after reperfusion. HBO treatment decreased glucose, pyruvate, and glutamate almost to the control level (preocclusion level). The lactate concentration remained unchanged after ischemic/reperfusion and after HBO treatment. This study suggested that altered brain energy metabolites and excitatory amino acids occurred during cerebral ischemia and and HBO regulated these striatal metabolites, which might contribute to the protective effect of HBO in cerebral ischemia.

Dual effect of HBO on cerebral infarction in MCAO rats.

Various reports in the literature have shown that hyperbaric oxygen (HBO) reduces cerebral infarction both in animals and humans. After the initial ischemic insult, however, initiating HBO treatment at different intervals has yielded conflicting results. The present study was undertaken to determine the optimal therapeutic window in which to start HBO treatment for cerebral infarction after transient focal ischemia. In this study, the operator occluded the middle cerebral artery (MCA) of anesthetized rats by introducing a blunted nylon filament into the proximal MCA from the dissected external carotid artery. When the operator removed the filament after 2 h, focal ischemia and reperfusion occurred. The operator then placed the rat in the HBO chamber and administered 3 atm absolute HBO for 1 h according to the protocol. The rat was killed 24 h after reperfusion, and the percentage of infarction (infarct ratio) was calculated by dividing the infarction area by the total area of the ipsilateral hemisphere. The results showed that the percentage of infarcted area decreased significantly (P < 0.05) both in the 3- (7.59%) and 6-h (5.35%) HBO-treatment groups compared with the control (no treatment) group (11.34%). However, the percentage of infarcted area increased significantly (P < 0.01 and P < 0.05, respectively) both in the 12- (23%) and 23-h (20%) treatment groups. The results of this study suggest that applying HBO within 6 h of ischemia-reperfusion injury could benefit the patient but that applying HBO 12 h or more after injury could harm the patient.

Preoperative exposure to calcium channel blockers suggests increased blood product use following cardiac surgery.

PURPOSE: In this study the authors reviewed the medical records of a random sample of patients undergoing coronary artery bypass grafting (CABG) during the preceding ten years at University Medical Center. The purpose of this study was to evaluate the impact of exposure to calcium channel blockers (CCB's) on blood product use following cardiopulmonary bypass (CPB). DESIGN: Retrospective medical record review. SETTING: University hospital. PARTICIPANTS: 527 patients undergoing CABG or re-do CABG. INTERVENTIONS: The medical records of approximately 50% of patients undergoing CABG or re-do CABG at University Medical Center between 1988 and 1998 were randomly selected by the medical records librarian for review. Preoperative medications, bypass time and temperature, and blood product use were recorded. RESULTS: Of the 527 patients studied, 309 (59%) had no exposure to CCB's. 218 (41%) were on CCB's at the time of admission. Patients who were on CCB's had an average 12.5 (+/- 1.0) blood product units transfused following bypass whereas those not on CCB's had an average 8.7 (+/- 0.6) units transfused (p < 0.001). Use of packed red blood cells (p < 0.001), fresh frozen plasma (p = 0.018) and platelets (p = 0.023) were each individually significantly increased. CONCLUSIONS: In this study, it appeared that patients exposed to CCB's before cardiac revascularization received significantly more blood products than those who were not exposed to CCB's. Because of the limitations imposed by retrospective studies, further prospective studies are warranted to define the clinical significance of CCB use in the perioperative period.

Optison (FS069) disrupts the blood-brain barrier in rats.

Optison is a new echocardiographic contrast agent, designed for IV injection, that is very useful in delineating cardiac structures during ultrasound examination. Because Optison could be a valuable adjunct in the diagnosis and evaluation of congenital heart disease, this study was undertaken to assess its effects on the blood-brain barrier when introduced directly in the cerebral circulation, as might occur with some congenital lesions. In this study, Sprague-Dawley rats were anesthetized, and Optison, at various dosages, was injected into the carotid artery. After this, Evans blue dye, a marker for blood-brain barrier disruption, was injected at different time intervals. Gross and histologic examination of the animals' brains revealed disruption of the blood-brain barrier that appeared to be Optison-dosage-dependent. Although the mechanism for this disruption is unclear, it may be related to the use of octofluoropropane gas used in the Optison as a contrast medium. Further studies are necessary to determine the pathologic consequences of Optison's effects on the blood-brain barrier.