Evaluation of cutting ability and plastic deformation of reciprocating files

Abstract This in vitro study evaluated the cutting ability of reciprocating files and the deformations caused by their multiple use. Five Reciproc® R25 files were divided into five groups for 10 simulated root canal preparations each. The resin blocks were weighed and photographed (12.5X and 20X) before and after preparation. The canals were prepared according to the manufacturer’s instructions. Enlargement of the root canals was evaluated by comparison of pre- and post-preparation images using a computer software. The preoperative and postoperative weight differences determined the cutting ability of repeatedly used instruments. The data were analyzed using Lilliefors and Friedman statistical tests. The cutting ability and enlargement of the canals gradually decreased after each use, with significant differences observed at the 8th and 9th repetitions, respectively. There was no evidence of file deformation. The cutting ability and enlargement of the simulated canals gradually decreased when a reciprocating file was used up to 10 times.

Analytical study on the RoHS of plastic from waste electrical and electronic appliances

This study was conducted to identify emission characteristics of certain hazardous substances contained in the plastic of used home electrical and electronic appliances keeping in view compliance with the Restriction of Hazardous Substances [RoHS] Directive and to estimate the possibility of safe recycling practices. According to the results, the concentration of cadmium, lead, mercury and chromium were found below than Maximum Concentration Value [MCV] of RoHS, while the concentration of total bromine [T-Br] was exceeded the standard limitations in the samples of plastic from e-waste. Over 90% of the plastics used in housing cover of display electronic products were composed of Polystyrene [PS] 53.9% and PS-flame retardants 36.4%.Peak of each hazardous substance in total samples also showed higher values of bromine, cadmium and lead. In order to enhance cleaner recycling of waste electronic appliances in accordance with the allowance of RoHS Directive, the use of brominated flame retardants in plastic and chrominated synthetic resins should be restricted and applications of metal surface finishing such as coating and painting of high molecules synthetic resins should be minimized

In situ evaluation of orthodontic elastomeric chains

The hypothesis tested in this study was that intraoral exposure of elastomeric chains alters their tensile strength. For such purpose, it was evaluated the in situ behavior of different elastomeric chains stretched for 3 weeks. Three kinds of elastomeric chains, Plastic chain (PC), Memory chain (MC) and Super slick chain (SSC), were randomly placed in 3 quadrants of 13 patient in a fixed distance of 16 mm and mean initial force of 180 g. Tensile testing was performed in an universal testing machine at different intervals: initial, 1 h, 24 h, 1 week, 2 weeks and 3 weeks. A two-way ANOVA test was performed to identify the influence of both material and time on the force decrease. A subsequent one-way ANOVAtest with the Tukey's post hoc test was used to identify statistically significant intragroup and intergroup remaining force (g and %) differences at 5% significance level. The effect of both the material and the time factors were significant. All groups showed significant force decrease after the 1-h period (23% for PC and 14% for MC and SSC). At the end of the 3-week period, the remaining force was 57% (96 g), 67% (129 g) and 71% (125 g) for PC, MC and SSC, respectively. In conclusion, intraoral exposure of elastomeric chains altered their tensile strength. In general, the greater force decrease occurred within the first hour. The remaining force of the enhanced chains measured at each time interval was greater than the conventional one (PC). After 3 weeks, only the enhanced chains maintained the force applied over 100 g.

A hipótese testada foi que a exposição dos elásticos em cadeia ao meio bucal altera sua força de tensão. Portanto, o objetivo deste estudo foi avaliar o comportamento, in situ, de diferentes cadeias elastoméricas quando tensionadas durante 3 semanas. Três tipos de elásticos em cadeia Plastic Chain (PC), Memory Chain (MC) e Super Slick Chain (SSC) foram inseridos aleatoriamente em 3 dos quadrantes de 13 pacientes com distância fixa de 16 mm e força inicial de 180 g. Foi realizado ensaio de tração em uma máquina de ensaio universal EMIC nos seguintes intervalos: inicial, 1 h, 24 h, 1 semana, 2 semanas e 3 semanas. O teste ANOVA a dois critérios foi aplicado para verificar a influência do material e do tempo na degradação da força. Subsequentemente, foi utilizado o teste ANOVA a um critério e pós-teste de Tukey para identificar diferenças estatísticas (p<0,05), intra-grupo e inter-grupo, na força remanescente (g e %). Tanto o material quanto o tempo tiveram efeito significativo na degradação da força. Todos os grupos mostraram diminuição significativa da força depois de 1 h sob tensão (23% para o PC e 14% para o MC e SSC). Ao final do período de 3 semanas, a força remanescente foi de 57% (96 g), 67% (129 g) e 71% (125 g) para o PC, MC e SSC, respectivamente. A exposição dos elásticos em cadeia ao meio bucal alterou a força de tensão. No geral, a maior diminuição da força ocorreu na primeira hora. A força remanescente testada em cada intervalo foi maior para os elásticos reforçados (MC e SSC) do que para o elástico convencional (PC). Após 3 semanas, apenas os elásticos reforçados mantiveram a força acima de 100 g.

Machined and plastic copings in three-element prostheses with different types of implantabutment joints: a strain gauge comparative analysis

OBJECTIVE: Using strain gauge (SG) analysis, the aim of this in vitro study was quantify the strain development during the fixation of three-unit screw implant-supported fixed partial dentures, varying the types of implant-abutment joints and the type of prosthetic coping. The hypotheses were that the type of hexagonal connection would generate different microstrains and the type of copings would produce similar microstrains after prosthetic screws had been tightened onto microunit abutments. MATERIALS AND METHODS: Three dental implants with external (EH) and internal (IH) hexagonal configurations were inserted into two polyurethane blocks. Microunit abutments were screwed onto their respective implant groups, applying a torque of 20 Ncm. Machined Co-Cr copings (M) and plastic prosthetic copings (P) were screwed onto the abutments, which received standard wax patterns. The wax patterns were cast in Co-Cr alloy (n=5), forming four groups: G1) EH/M; G2) EH/P; G3) IH/M and G4) IH/P. Four SGs were bonded onto the surface of the block tangentially to the implants, SG 1 mesially to implant 1, SG 2 and SG 3 mesially and distally to implant 2, respectively, and SG 4 distally to implant 3. The superstructure's occlusal screws were tightened onto microunit abutments with 10 Ncm torque using a manual torque driver. The magnitude of microstrain on each SG was recorded in units of microstrain (µε). The data were analyzed statistically by ANOVA and Tukey's test (p<0.05). RESULTS: Microstrain values of each group were: G1= 338.1±223.0 µε; G2= 363.9±190.9 µε; G3= 415.1±53.5 IE; G4= 363.9±190.9 µε. No statistically signifcant difference was found between EH and IH, regardless of the type of copings (p>0.05). The hypotheses were partially accepted. CONCLUSIONS: It was concluded that the type of hexagonal connection and coping presented similar mechanical behavior under tightening conditions.

Field evaluation of ZeroFly® - an insecticide incorporated plastic sheeting against malaria vectors & its impact on malaria transmission in tribal area of northern Orissa.

Background & objectives: Insecticide incorporated plastic sheeting is a new technology to control mosquitoes in emergency shelter places and also temporary habitations in different locations. Therefore, field studies were conducted to assess the efficacy of ZeroFly® plastic sheeting treated with deltamethrin on prevailing disease vectors Anopheles culicifacies and An. fluviatilis and its impact on malaria transmission in one of the highly endemic areas of Orissa. Methods: The study was conducted in Birkera block of Sundargarh district, Orissa state. The study area comprised 3 villages, which were randomized as ZeroFly plastic sheet, untreated plastic sheet and no sheet area. ZeroFly plastic sheets and untreated plastic sheets were fixed in study and control villages respectively covering all the rooms in each household. Longitudinal studies were conducted on the bioefficacy with the help of cone bioassays, monitoring of the mosquito density through hand catch, floor sheet and exit trap collections and fortnightly domiciliary active surveillance in all the study villages. Results: In ZeroFly plastic sheeting area, there was a significant reduction of 84.7 per cent in the entry rate of total mosquitoes in comparison to pre-intervention phase. There was 56.2 per cent immediate mortality in total mosquitoes in houses with ZeroFly sheeting. The overall feeding success rate of mosquitoes in the trial village was only 12.5 per cent in comparison to 49.7 and 51.1 per cent in villages with untreated plastic sheet and no sheet respectively. There was a significant reduction of 65.0 and 70.5 per cent in malaria incidence in ZeroFly plastic sheeting area as compared to untreated plastic sheet and no sheet area respectively. Interpretation & conclusions: Our study showed that introduction of ZeroFly plastic sheets in a community-based intervention programme is operationally feasible to contain malaria especially in the high transmission difficult areas.

Medicamentos esenciales del Perú: Propuesta para Acido Ascorbico en gotas. Estudio de su estabilidad en envases plásticos / Esential medication of Perú: Ascorbic acids in drips. Stability study in plastic packaging

La conservabilidad de la solución de ácido ascórbico a temperaturas elevadas y a temperatura ambiental, brindada por los diferentes tipos de envases evaluados, ha sido del orden siguiente: II>PVC>I>PE, en tanto que frente a la radiación luminoso artificial fue: PVC>II>I>PE. El efecto producido por la radiación luminosa artificial, sobre las muestras, fue cercano al ocasionado a temperaturas de 30 `C y 50 `C en los envases de polietileno. La solución envasada. en los cuatro tipos de envases, no evidenció alteración significativo en PH, ni peso específico. El envase de polietileno, fue el menos apropiado por ser el menos resistente a la radiación luminosa artificial y permitir una rápida degradación de la solución de la solución de ácido ascórbico, en tanto que el envase de cloruro de polivinilo demostró ser el más apropiado para conservar la fórmula evaluada.