Fractographic analysis of separated endodontic file designs.

Endodontic rotary files are cutting instruments used to perform root canal procedures within a tooth interior. Focusing on quantitative fractographic analysis increases necessary, clinical performance understanding of file separation failure. This research employed controlled, dynamic testing to failure of commercial rotary files, analyzing the fractographic, forensic characteristics in relation to Weibull reliability determination, considering: (1) design analysis; (2) stress concentrations; (3) times to failure; (4) number of cycles to failure (NCF). Ex vivo testing included three file designs, each having constant tip size (0.035 mm), taper (0.06 mm/mm), and length (25 mm). Files were individually tested using an electric, torque-controlled handpiece, rotating within a standardized, simulated canal until fracture separation occurred. Fractographic analysis, including critical measurements, was conducted using the scanning electron microscope (SEM) (PhenomProX, PhenomWorld, NL). Weibull statistical analysis established reliability factors per design group. Fractographic analysis identified separation fractures, processing inclusions, flexural-fatigue striations, and stress concentrations at flute pitches. Calculated NCF median values (1277-EE; 899-VB; 713-PI) demonstrated significant statistical differences among groups (p < 0.001). Separated apical fragments yielded statistically significant differences (p ≤ 0.05) for varying file design groups. Weibull moduli among groups were statistically equivalent. Fractographic analysis exposed a presence of multiple failure factors in addition to defect distribution, governing cyclic fatigue failure originating at stress concentration points irrespective of file design. Fractographic analysis indicated that a change in file design, specifically at the working edges, in addition to improved surface finish, has the potential of reducing failures by lowering points of stress concentration and reducing fracture initiating surface cracks.

Effects of N-Nitrosodiethylamine, a Potent Carcinogen, on Sexual Development, Gametogenesis, and Oocyte Maturation.

N-Nitrosodiethylamine (DEN), a well-known hepatocarcinogen, is found in certain food products as such or as a metabolic byproduct. This study investigated the effects of DEN on sexual development, gametogenesis, and oocyte maturation in Japanese medaka (Oryzias latipes). DEN reduced the germ cell number dose-dependently during early stages of sexual differentiation in XX larvae, resulting in underdeveloped ovaries in adulthood at low doses. This effect was sex-specific as no such changes were seen in XY larvae. Furthermore, XX and XY larvae that were exposed at a low dose during early life showed a significant reduction in body weight in adulthood. Gonads in sexually immature adult medaka males and females exposed to DEN were in advanced stages in comparison to that of the controls. Gonado-somatic indices were significantly high in treated males and females. DEN induced oocyte maturation in vitro, which was inhibited by cordycepin, demonstrating that it stimulated oocyte maturation through polyadenylation of cyclin B mRNA as in the case of the endogenous maturation-inducing hormone. Altogether, our results have proven that DEN could disrupt or mimic the signaling pathways involved in germ cell development, proliferation, and maturation.

[Effects of menthol as an additive in tobacco products and the need for regulation]. / Wirkungen von Menthol als Zusatzstoff in Tabakprodukten und die Notwendigkeit einer Regulierung.

Menthol is the most widely used and the most prominent tobacco additive in tobacco products advertised and marketed by the tobacco industry. Besides its characteristic flavor, it possesses a variety of pharmacological properties facilitating tobacco smoke inhalation and potentiating dependence. These properties of menthol not only favor tobacco initiation and consumption but can also prevent smoking cessation. This article summarizes the effect of menthol as an additive in tobacco products and its effect on tobacco consumption that causes a number of chronic diseases and premature death and, therefore, counteracts tobacco control measures. Currently, there is no legislative regulation in Germany that considers the health hazard, addiction-enhancing and attractiveness-increasing properties of additives permitted in tobacco products. Effective regulation or even a ban could contribute to a reduction of tobacco consumption and, hence, save many people from a long-lasting tobacco dependence.

Prevention and treatment of DNA vaccine encoding cockroach allergen Bla g 1 in a mouse model of allergic airway inflammation.

BACKGROUND: One-fourth of the US population is sensitized to the German cockroach. Primary German cockroach allergen Bla g 1 is detected in 63% of homes and 52% of childcare facilities in the United States. No effective treatment or vaccination strategies are yet available. OBJECTIVES: We evaluated the prophylactic and therapeutic efficacy of a plasmid DNA-mediated vaccination using the Bla g 1 gene in a mouse model of allergic inflammatory airway disease. METHODS: A plasmid DNA vector coding for the Bla g 1 allergen controlled by cytomegalovirus promoter was constructed. To estimate the protective efficacy, BALB/c mice were given three injections of plasmid DNA-Bla g 1 prior to sensitization with two priming doses of recombinant Bla g 1 (rBla g 1) antigens, followed by nebulized rBla g 1 challenge. In the therapeutic approach, sensitization was followed by administering Bla g 1 DNA vaccine. RESULTS: Bla g 1 vaccination significantly reduced allergen-induced airway inflammation, even after mice were presensitized and a Th2-dominant response was established. The Bla g 1 vaccination significantly reduced total inflammatory cell infiltrate, eosinophilia, secretion of Th2 cytokines IL-4 and IL-5 in bronchoalveolar lavage fluid, allergen-induced inflammatory infiltrates in the lungs, and Bla g 1-specific IgE in serum upon challenge with rBla g 1. Importantly, Bla g 1 DNA vaccination was able to induce IL-10-secreting regulatory T cells that could suppress the allergen-specific Th2 cells. CONCLUSION: DNA vaccination showed protective and therapeutic efficacy against a clinically relevant allergen Bla g 1.

Experimental autoimmune hearing loss is exacerbated in IL-10-deficient mice and reversed by IL-10 gene transfer.

Interleukin-10 (IL-10) has an important role in the homeostatic regulation of autoreactive T-cell repertoire. We hypothesized that endogenous IL-10 would regulate the severity of ß-tubulin-induced experimental autoimmune hearing loss (EAHL) and that exogenous IL-10 would abrogate it. BALB/c wild-type (WT) and homozygous IL-10-deficient mice (IL-10(-/-)) underwent ß-tubulin immunization to develop EAHL; some IL-10 mice with EAHL were administered IL-10 DNA at the peak of EAHL. Auditory brainstem responses were examined over time. EAHL developed progressively in both WT and IL-10(-/-) mice. However, the severity of hearing loss in the IL-10(-/-) mice was significantly greater than that in WT animals. Moreover, disease severity was associated with a significantly enhanced interferon-γ level and loss of hair cells in IL-10(-/-) mice. IL-10 administered to EAHL IL-10(-/-) mice promoted IL-10 expression. Consequently, hearing significantly improved by protecting hair cells in established EAHL. Importantly, IL-10 treatment suppressed proliferation of antigen-specific T-helper type 1 (Th1) cells, and the suppression can be attributed to inducing IL-10-secreting regulatory T cells that suppressed autoreactive T cells. We demonstrated that the lack of IL-10 exacerbated hearing loss, and the exogenous administration of IL-10 improved hearing. Mechanistically, our results indicate that IL-10 is capable of controlling autoimmune reaction severity by suppressing Th1-type proinflammatory responses and inducing IL-10-secreting regulatory T cells.

Factors associated with maternal depressive symptoms among low-income, African American smokers enrolled in a secondhand smoke reduction programme.

Introduction Maternal depressive symptoms increase the risk of poor maternal and child health outcomes, and are a primary barrier to health behaviour change. Social cognitive theory can guide our understanding of risk factors that may have an impact on maternal depressive symptoms. The aim of this paper was to understand the correlates of maternal depressive symptoms among low-income African American smokers completing a 16-week intervention trial to reduce young children's second-hand smoke exposure (SHSe). Methods This study presents a secondary analysis of depression symptoms among 227 maternal smokers completing the SHSe-reduction trial. The end-of-treatment Center of Epidemiologic Studies Depression Scale (CES-D) score was used to assess depressive symptoms (dichotomised as 0 = score of < 16 and 1 = score of ≥ 16). Multivariate logistic regression analysis was used to test the one-way hypothesis that odds of significant depressive symptoms would be associated with greater total number of household smokers, greater number of paediatric sick visits, greater daily exposure of child to cigarette smoke by their mother, greater life-event stress, and lower social support, marital status, employment status and level of educational attainment. Results Number of household smokers (OR = 1.57, P = 0.049), social support (OR = 0.88, P < 0.001) and life-event stress (OR = 1.04, P = 0.001) predicted significant maternal depressive symptoms; all other variables were not significant predictors in the model. Conclusion Number of household smokers is a novel risk factor for understanding significant maternal depressive symptoms in the context of a childhood SHSe-reduction trial. Improving our understanding of the household-level social milieu in the context of SHSe-reduction interventions will assist in reducing the risk of maternal depressive symptoms.

Study on ultrasound assisted precipitation of CL-20 and its effect on morphology and sensitivity.

Applying ultrasound to crystallizing systems offers significant advantages for modifying and improving the processes as well as quality of products. This paper reports on ultrasound assisted reprecipitation of CL-20 to obtain fine particles as well as to achieve desired morphology, which will improve insensitivity characteristics. In this study, CL-20 has been reprecipitated by sonication process and has been characterized by DSC, SEM and particle size analysis. The results are compared with control CL-20 sample (unsonicated). SEM photographs revealed that sonication process offer uniform crystalline morphology without any agglomeration. The particle size of sonicated CL-20 sample obtained is around 5+/-1 microm with a narrow particle size distribution. The DSC thermogram of sonicated and unsonicated sample is identical. CL-20 samples were subjected to impact and friction sensitivity experiments, the results indicate the sensitivity characteristics reduced considerably. Ultrasonic assisted crystallization technique reduces the time of reprecipitation considerably with an enhanced recovery of CL-20 with a very narrow particle size distribution.

Preparation and thermal studies on tetranitrodibenzo tetraazapentalene (TACOT): a thermally stable high explosive.

Thermally stable high explosive, tetranitro-2,3,5,6-dibenzo-1,3a,4,6a-tetraazapentalene (TACOT) was synthesized and characterized during this work. Thermo analytical techniques (TG and DSC) were applied to study the thermal decomposition behaviour of TACOT in comparison with benchmark thermally stable high explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). Kinetic parameters such as reaction order, activation energy and pre-exponential factors were computed from the thermal data. The activation energy for TACOT (292 kJ/mol) was found 1.5 times to that of TATB (200 kJ/mol), which can account for its higher thermal stability and can be attributed to pentalene moiety in the former.

The coronary baroreflex in humans.

Previous studies have identified the presence of coronary baroreceptors in animal models. We set up a study to explore the presence of coronary baroreceptors in humans, which was performed with isolated, graded aortic root perfusion in patients during cardiopulmonary bypass. With ethical approval 12 patients with normal coronary arteries, aged 58-75 (mean 69) years undergoing mitral valve surgery were recruited to the study with informed consent. Those with aortic valve incompetence, coronary, or peripheral artery disease and diabetes mellitus were excluded. They were randomized to have their coronary perfusion pressure set low at 50 mmHg for 90 seconds and then adjusted high to 80 mmHg for 90 seconds (group L-H) or the reverse sequence (group H-L). Average arterial pressure and approximately constant systemic flow over 30-second periods were used to calculate vascular resistance (SVR). The first six experiments followed initiation of cardiopulmonary bypass and aortic clamping but before the delivery of cold blood cardioplegia; the blood temperature for these experiments was kept at 32 degrees C. The remaining six were conducted prior to removal of the aortic cross clamp at 37 degrees C. Coronary sinus blood samples were analyzed to exclude myocardial ischemia. Coronary sinus blood samples showed insignificant variation in oxygen saturation, lactate, and troponin T. Three patients were excluded because of unstable blood pressure. In the (L-H) group SVR reduced in 4 of 4 remaining patients (mean -9.4%, range -3.9 to -19.6%). In the (H-L) group SVR increased in three patients (mean +2.0%, range 1.1 to 3.7%) but decreased in two (-8.9% and -15.8%). These preliminary results, although not statistically different, suggest the presence of coronary baroreceptors in humans. The reflex vascular responses are similar to those previously reported in animal models.

Establishment of process technology for the manufacture of dinitrogen pentoxide and its utility for the synthesis of most powerful explosive of today--CL-20.

This paper reviews the recent work done on the synthesis as well as characterization of dinitrogen pentoxide (DNPO). The physico-chemical characteristics of DNPO are also discussed. The review brings out the key aspects of N2O5 technology with relevance to realize modern and novel HEMs. The paper also includes the aspects related with establishing the synthesis facility of dinitrogen pentoxide at HEMRL by gas phase interaction of N2O4 with O3. The process parameters for the synthesis of N2O5 at 50 g/batch have been optimized. The synthesized dinitrogen pentoxide has been characterized by UV [204, 213, 258 nm (pi-->pi*) 378 and 384 nm (n-->pi*)] and IR (1428, 1266, 1249, 1206, 1044, 822, 750, 546 and 454 cm(-1)) spectroscopy. The DSC clearly showed the sublimation of N2O5 at 32 degrees C. The nitration studies on 2,6,8,12-tetraacetylhexaaza tetracyclo[5,5,0,0(3,11)0(5,9)]dodecane (TAIW) proved its viability in 2,4,6,8,10,12-hexanitro-2,4,6,8(10,12))-hexaazatetracyclo [5,5,0,0(3,11)0(5,9)]dodecane (CL-20) synthesis. The synthesized CL-20 and its precursors have also been subjected to hyphenated TG-FTIR studies to understand decomposition pattern.

Effect of extended perioperative antibiotic prophylaxis on intravascular catheter colonization and infection in cardiothoracic surgery patients.

Intravascular catheter-related infections (CRI) account for one third of nosocomial bloodstream infections in England. UK Department of Health guidelines state that antibiotic prophylaxis is not required during placement, or use of, central venous catheters, to prevent CRI. However, some clinicians continue to use antibiotics in an attempt to prevent CRI. We investigated the effect of extended routine perioperative antibiotic prophylaxis in cardiothoracic patients on rates of intravascular catheter (IVC) colonization and infection. Investigations were undertaken in patients undergoing uncomplicated cardiothoracic surgery during July 2001-February 2002. Patients who received three doses of cefuroxime as perioperative prophylaxis were compared with those who received extended cefuroxime prophylaxis until the IVC was removed. Patients were not randomized into groups, but received the different prophylaxis regimens according to the usual practice of the consultant cardiothoracic surgeon. A roll tip method was used to determine IVC colonization. Of 191 patients who fulfilled the inclusion criteria, 12 were excluded because data were incomplete. One hundred and forty-six patients received routine prophylaxis, and 33 prophylaxis until the IVC was removed. Twenty-three out of 146 (16%) IVCs in the 'routine' group and four out of 33 (12%) in the 'extended' group became colonized; no IVC-related bloodstream infections occurred during the survey. The duration of IVC placement and the types of operation performed in the two groups were not significantly different (P > 0.05). In routine cardiothoracic surgery patients, extending routine perioperative antibiotic prophylaxis until all IVCs have been removed does not influence rates of IVC colonization.

A common beta1-adrenergic receptor polymorphism (Arg389Gly) affects blood pressure response to beta-blockade.

BACKGROUND: A common polymorphism of the beta(1)-adrenergic receptor Arg389Gly markedly affects function in vitro, but little is known about its in vivo significance. METHODS AND RESULTS: Resting and exercise hemodynamic responses were measured in subjects homozygous for Arg389 (n = 21) or Gly389 (n = 13) alleles before and 3 hours after administration of a beta-blocker, atenolol. Demographic characteristics and atenolol concentrations were similar in the two genotypic groups. Genotype had a marked effect on resting hemodynamic responses to atenolol, with Arg389-homozygous subjects having a larger decrease in resting systolic blood pressure (8.7 +/- 1.3 mm Hg versus 0.2 +/- 1.7 mm Hg, P < .001) and mean arterial blood pressure (7.2 +/- 1.0 mm Hg versus 2.0 +/- 1.7 mm Hg, P = .009). Attenuation of exercise-induced hemodynamic responses by atenolol was not affected by genotype. CONCLUSIONS: There is reduced sensitivity of Gly389 homozygotes to a beta-adrenergic receptor antagonist, and this polymorphism may be an important determinant of variability in response to beta-blockade.

Accuracy of tuned aperture computed tomography in the diagnosis of radicular fractures in non-restored maxillary anterior teeth--an in vitro study.

OBJECTIVES: This study compared the accuracy of three radiographic imaging modalities for the detection of artificially induced radicular fractures on maxillary anterior teeth. METHODS: Fractures were induced in 28 of 54 maxillary incisors in 15 cadaver specimens using a distally directed force. Radiographs evaluated included conventional two-dimensional direct digital radiographs (DDI), unprocessed Tuned Aperture Computed Tomography (TACT-U) and iteratively restored TACT (TACT-IR). Eight observers recorded their findings using a five-point confidence-rating scale. Receiver Operating Characteristic (ROC) analyses were done, followed by ANOVA to test for significant effects of observers, imaging modality and fracture location. Post hoc tests were carried out in instances where ANOVA indicated significance. RESULTS: The areas under the ROC-curves (A(z)) were, respectively: DDI: 0.53; TACT-U: 0.83 and TACT-IR: 0.97. TACT-IR and TACT-U performed significantly better than DDI (P < 0.001) with TACT-IR providing a higher detection accuracy than TACT-U (P < 0.033). A difference in detection accuracy was also noted based on fracture location (P < 0.001). Tukey's post hoc analyses revealed that fractures extending beyond the middle third of the root were more accurately detected. Inter-observer agreement was 0.68, and intra-examiner agreement, 0.87 (kappa analysis). CONCLUSIONS: TACT performed significantly better than direct digital images in detecting trauma-induced radicular fractures in unrestored, maxillary anterior teeth.

The left atrial roof incision: an asset for minimally invasive mitral valve surgery.

BACKGROUND: The focus in minimally invasive mitral valve surgery has been on reducing thoracic incisions. Several cardiac incisions described in these procedures do not conform with the philosophy of "minimal invasiveness". We describe the left atrial roof incision which has the potential of facilitating an excellent mitral valve exposure through a limited cardiac incision, without major cardiac trauma. The safety, efficacy and technical ease of this technique for minimally invasive mitral valve surgery is evaluated. METHODS: From July 1998 to December 2000, 95 consecutive patients underwent mitral valve surgery by the same surgeon. The patients were divided into 2 groups on the basis of the cardiac incision used for correction of mitral valve disease. Group I patients had left atrial roof incision and group II patients had the traditional paraseptal incision. Each group was further classified into the minimally invasive sternotomy and standard sternotomy subgroups. The clinical variables and complications in the 2 groups were compared. RESULTS: There were 40 male and 55 female patients with a mean age of 63 +/-12yrs (range 29 to 88yrs). LARI was used for mitral valve exposure in 81 patients (85%). In 18 patients (19%), surgery was by minimally invasive technique. The mitral valve was replaced in 82% of patients and repaired in 18%. LARI provided a better exposure of the mitral valve in its anatomical and physiological disposition, without distortion. There was no significant difference in the cross clamp times and postoperative complications between the 2 groups. More patients in the LARI group regained sinus rhythm at discharge. CONCLUSION: LARI is safe and technically easy to perform. It provides an excellent exposure of the mitral valve and left heart cavities in its anatomical disposition with minimal cardiac trauma, making it ideal for minimally invasive mitral surgery.

Climatic impact of tropical lowland deforestation on nearby montane cloud forests.

Tropical montane cloud forests (TMCFs) depend on predictable, frequent, and prolonged immersion in cloud. Clearing upwind lowland forest alters surface energy budgets in ways that influence dry season cloud fields and thus the TMCF environment. Landsat and Geostationary Operational Environmental Satellite imagery show that deforested areas of Costa Rica's Caribbean lowlands remain relatively cloud-free when forested regions have well-developed dry season cumulus cloud fields. Further, regional atmospheric simulations show that cloud base heights are higher over pasture than over tropical forest areas under reasonable dry season conditions. These results suggest that land use in tropical lowlands has serious impacts on ecosystems in adjacent mountains.

An in-vitro evaluation of Kodak Insight and Ektaspeed Plus film with a CMOS detector for natural proximal caries: ROC analysis.

This study compared the diagnostic efficacy of Kodak Ektaspeed Plus film, Kodak Insight film, a newly introduced E/F-speed film, and Schick CMOS-APS digital sensor, with respect to caries detection in 92 proximal surfaces of extracted unrestored teeth, 51 of which were carious. Ground truth was evaluated histologically and the lesions classified as enamel or dentinal. Eight observers read the radiographs using a five-point confidence rating scale to record their diagnoses. Analyses using receiver operating characteristic curves revealed the areas under each curve that indicated the diagnostic accuracy (Ektaspeed Plus - 0.760, Insight - 0.778 and CMOS-APS sensor - 0.732). ANOVA revealed significant differences with respect to caries depth (p<0.031) and observers (p<0.0001). Weighted kappa analyses indicated moderate to substantial inter- and intra-observer agreement (0.42 and 0.66, respectively). The results suggest that none of the imaging modalities evaluated in this study differed in their diagnostic capabilities with respect to proximal decay detection and that the Insight film which was used with 20% less radiation exposure than Ektaspeed Plus film was as good as the other two sensors for this purpose.

Tuned aperture computed tomography to evaluate osseous healing.

Quantification of osseous healing is a challenging task, requiring expensive advanced imaging modalities. To improve diagnostic osseous imaging, we undertook this prospective study to explore the potential of Tuned Aperture Computed Tomography. Eighty defects in 20 rabbit mandibles, randomly carrying an osteoblast suspension or a polymer matrix or a combination thereof or no treatment, were imaged at 3, 6, 9, and 12 weeks post-surgery. TACT slices, iteratively restored TACT, and conventional digital radiographs were evaluated. Mean-gray-value distribution within regions of interest was correlated with histomorphometric data. Lesions treated with osteoblast/polymer-matrix delivery systems demonstrated the highest mean gray-value, while the diagnostic efficacy of TACT-IR was significantly better than that of other imaging modalities (p < 0.001). Thus, TACT is an accurate imaging modality for non-destructive quantification of osseous dynamics.

Fractal analyses of osseous healing using tuned aperture computed tomography images.

The aim of this study was to evaluate osseous healing in mandibular defects using fractal analyses on conventional radiographs and tuned aperture computed tomography (TACT; OrthoTACT, Instrumentarium Imaging, Helsinki, Finland) images. Eighty test sites on the inferior margins of rabbit mandibles were subject to lesion induction and treated with one of the following: no treatment (controls); osteoblasts only; polymer matrix only; or osteoblast-polymer matrix (OPM) combination. Images were acquired using conventional radiography and TACT, including unprocessed TACT (TACT-U) and iteratively restored TACT (TACT-IR). Healing was followed up over time and images acquired at 3, 6, 9, and 12 weeks post-surgery. Fractal dimension (FD) was computed within regions of interest in the defects using the TACT workbench. Results were analyzed for effects produced by imaging modality, treatment modality, time after surgery and lesion location. Histomorphometric data were available to assess ground truth. Significant differences (p < 0.0001) were noted based on imaging modality with TACT-IR recording the highest mean fractal dimension (MFD), followed by TACT-U and conventional images, in that order. Sites treated with OPM recorded the highest MFDs among all treatment modalities (p < 0.0001). The highest MFD based on time was recorded at 3 weeks and differed significantly with 12 weeks (p < 0.035). Correlation of FD with results of histomorphometric data was high (r = 0.79; p < 0.001). The FD computed on TACT-IR showed the highest correlation with histomorphometric data, thus establishing the fact TACT is a more efficient and accurate imaging modality for quantification of osseous changes within healing bony defects.

Imaging of mandibular trauma: ROC analysis.

OBJECTIVES: To compare the diagnostic efficacies of panoramic radiographs, mandibular trauma series, and digitized radiographs for detection of fractures of the mandible. METHODS: Fractures were induced using blunt trauma in 25 cadaver mandibles. Panoramic radiographs, digitized radiographs, and mandibular series comprising an anteroposterior view, two lateral oblique, and a reverse Towne's were used. Six observers recorded their diagnoses using a five-point confidence rating scale. The data were analyzed using receiver operating characteristic (ROC) curve analysis. RESULTS: Significant differences based on imaging modalities were found (p < 0.0015) in the area under the curves (A(z)): panoramic radiograph, 0.8762; mandibular series, 0.7521; panoramic plus anteroposterior radiographs combination, 0.8886; and digitized mandibular series, 0.7723. No observer-based differences were noted. Condylar and coronoid fractures were difficult to detect than those in other areas of the mandible (p < 0.033). Intra- and inter-observer agreements were high (kappa(w) = 0.81 and 0.76, respectively). CONCLUSIONS: Panoramic radiographs are adequate for detection of mandibular fractures. Addition of an anteroposterior view augments diagnostic accuracy.