Evaluation Of The Risk Of A Stripping Perforation With Gates-glidden Drills: Serial Versus Crown-down Sequences

The aim of this study was to evaluatte the remaining dentine/cementum thickness using Gates-Glidden burs in serial and crown-down sequences and to observe which of the two sequences is the safest for preparing mesial roots of molars. Thirty-six left and. right human mandibular first molars were selected. Standard access cavities were made and initially explored with Flexofiles sizes 10 and 15 until the tip was visible at the apex. The teeth were embedded in a muffle speqially developed for this study using a PVC tube with two parallel metal rods An its lid. Each tooth-block was sectioned 3 mm apically to the furcation using a low-speed saw with a diamond disc. The tooth-block was examined under a microscope and an initial image was captured by a digital video system with 8 X and 12 X magnifications. Finally, the tooth-blocks were reassembled in the muffle so that the canals could be instrumented. After instrumentation the area of each mesial canal as well as the smallest distance to the root furcation were measured again. The mesio-buccal canals (crown-down order) and the mesio-lingual canals (serial sequence) presented an average area of 0.46 ± 0.16 mm2 and 0.88 ± 0.27 mm2 (P < 0.01), respectively. The mean values of the smallest distance to the furcation for the mesio-buccal and mesio-lingual canals were 0.66 ± 0.19 mm and 0.39 ± 0.13 mm (P < 0.01), respectively. The remaining dentine/cementum thickness using Gates-Glidden burs was greater in the crown-down sequence than in the serial sequence.2211824Grossman, L., A brief history of endodontics (1982) J Endod, 8 (1), p. 538Mullaney TP. Instrumentation of finely curved canals. Dent Clin North Am. l979;23(4):575-92Taintor, J.F., Use of the gates glidden bur in endodontics (1978) J Nebr Dent Assoc, 54 (3), pp. 10-12Weine, F.S., Kelly, R.E., Lio, P.J., The effect of preparation procedures on original canal shape and on apical foramen shape (1975) J Endod, 1 (8), pp. 255-262Abou-Rass, M., Frank, A.L., Glick, D.H., The anticurvature filing method to prepare the curved root canal (1980) J Am Dent Assoc, 101 (5), pp. 792-794Cunningham, C.J., Senia, S.E., A three-dimensional study of canal curvatures in the mesial roots of mandibular molars (1992) J Endod, 18 (6), pp. 294-300Coutinho-Filho.T, De-Deus G, Guimarães T, Gurgel-Filho ED, Maniglia-Ferreira C. A computer evaluation of the dentin remaining after cervical preparation in curved canals: Gatesglidden drills vs. orifice shaper. Braz J Oral Sci. 2002;1(3):116-20Lim, S.S., Stock, C.J., The risk of perforation in the curved canal: Anticurvature filing compared with the step-back technique (1987) Int Endod J, 20 (1), pp. 33-39Isom, T.L., Marshall, J.G., Baumgartner, J.C., Evaluation of root thickness in curved canals after flaring (1995) J Endod, 21 (7), pp. 368-371Gluskin, A.H., Brown, D.C., Buchanan, L.S., A reconstructed computerized tomographic comparison of Ni-Ti rotary GT files versus traditional instruments in canals shaped by novice operators (2001) Int Endod J, 34 (6), pp. 476-484Schilder, H., Cleaning and shaping the root canal (1974) Dent Clin North Am, 18 (2), pp. 269-296Bramante, C.M., Berbet, A., Borges, R.P., A methodology for evaluation of root canal instrumentation (1987) J Endod, 13 (5), pp. 243-245Bower, R.C., Furcation morphology relative to periodontal treatment. Furcation entrance architecture (1979) J Periodontol, 50 (1), pp. 23-27Kessler, J.R., Peters, D.D., Lorton, L., Comparison of the relative risk of molar root perforations using various endodontic instrumentation techniques (1983) J Endod, 9 (10), pp. 439-447McCann, J.T., Keller, D.L., LaBounty, G.L., A modification of the muffle model system to study root canal morphology (1990) J Endod, 16 (3), pp. 114-115Pilo, R., Corcino, G., Tamse, A., Residual dentin thickness in mandibular premolars prepared with hand and rotatory instruments (1998) J Endod, 24 (6), pp. 401-404Torabinejad, M., Rotstein, L., Stabholz, A., Effect of preflaring on tactile detection of the apical constriction (1995) J Endod, 21 (2), pp. 92-94West JD, Roane JB. Limpeza e modelagem do sistema de canais radiculares. In: Cohen S, Burns RC. Caminhos da polpa. 7th ed. Rio de Janeiro: Guanabara Koogan2000. p. 206-36Abou-Rass, M., Jastrab, R.J., The use of rotary instruments as auxiliary aids to root canal preparation of molars (1982) J Endod, 8 (2), pp. 78-7

Hadronization properties of b quarks compared to light quarks in e+e- -> q qbar from 183 to 200 GeV

The DELPHI detector at LEP has collected 54 pb^{-1} of data at a centre-of-mass energy around 183 GeV during 1997, 158 pb^{-1} around 189 GeV during 1998, and 187 pb^{-1} between 192 and 200 GeV during 1999. These data were used to measure the average charged particle multiplicity in e+e- -> b bbar events, _{bb}, and the difference delta_{bl} between _{bb} and the multiplicity, _{ll}, in generic light quark (u,d,s) events: delta_{bl}(183 GeV) = 4.55 +/- 1.31 (stat) +/- 0.73 (syst) delta_{bl}(189 GeV) = 4.43 +/- 0.85 (stat) +/- 0.61 (syst) delta_{bl}(200 GeV) = 3.39 +/- 0.89 (stat) +/- 1.01 (syst). This result is consistent with QCD predictions, while it is inconsistent with calculations assuming that the multiplicity accompanying the decay of a heavy quark is independent of the mass of the quark itself.Comment: 13 pages, 2 figure

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time, and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space. While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes, vast areas of the tropics remain understudied. In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity, but it remains among the least known forests in America and is often underrepresented in biodiversity databases. To worsen this situation, human-induced modifications may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge, it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Importance of SERCA2a on early isolated diastolic dysfunction induced by supravalvular aortic stenosis in rats

Cardiac remodeling is defined as changes in shape and function of the heart in response to aggression (pressure overload). The sarcoplasmic reticulum calcium ATPase cardiac isoform 2a (SERCA2a) is a known factor that influences function. A wide spectrum of studies report a decrease in SERCA2a in heart failure, but none evaluate it's the role in early isolated diastolic dysfunction in supravalvular aortic stenosis (AoS). Our hypothesis was that SERCA2a participates in such dysfunction. Thirty-day-old male Wistar rats (60-80 g) were divided into AoS and Sham groups, which were submitted to surgery with or without aorta clipping, respectively. After 6 weeks, the animals were submitted to echocardiogram and functional analysis by isolated papillary muscle (IPM) in basal condition, hypoxia, and SERCA2a blockage with cyclopiazonic acid at calcium concentrations of 0.5, 1.5, and 2.5 mM. Western-blot analyses were used for SERCA2a and phospholamban detection. Data analysis was carried out with Student's t-test and ANOVA. AoS enhanced left atrium and E and A wave ratio, with preserved ejection fraction. Basal condition in IPM showed similar increases in developed tension (DT) and resting tension (RT) in AoS, and hypoxia was similar between groups. After cyclopiazonic acid blockage, final DT was equally decreased and RT was similar between groups, but the speed of relaxation was decreased in the AoS group. Western-blot was uniform in all evaluations. The hypothesis was confirmed, since functional parameters regarding SERCA2a were changed in the AoS group