Influência do tratamento de superfície da dentina radicular na resistência ao deslocamento de pino de fibra de vidro / Influence of root dentin surface treatment on bond strength of glass fiber post

Este trabalho avaliou a influência do tratamento de superfície na dentina radicular na resistência de união com pinos de fibra de vidro e cimento resinoso autoadesivo. Coletou-se 120 dentes incisivos inferiores bovinos dos quais 30 foram selecionados e tiveram suas coroas cortadas, permanecendo o remanescente radicular de 16 mm. Foi realizado o tratamento endodôntico e preparo intracanal para o pino, com profundidade de 8 mm para cimentação com cimento resinoso autoadesivo. As amostras foram divididas, randomicamente, em três grupos, segundo o tipo de tratamento de superfície, para limpeza intracanal após o preparo para cimentação: Grupo I - água destilada; Grupo II - EDTA 17% e Grupo III - clorexidina 0,12%. Os corpos de prova formados pelo conjunto dente-pino foram cortados no terço cervical, médio e apical, obtendo espécimes com 2,0 mm de espessura. Os espécimes foram levados à máquina de ensaios universal com velocidade de 0,5 mm/min para teste de resistência ao cisalhamento æpush-outÆ. A análise dos resultados foi feita com o teste ANOVA e Teste de Tukey (p<0,05). Os efeitos da água destilada, clorexidina 0,12% e EDTA 17% foram diferentes no tratamento superficial da dentina radicular, havendo diferença na resistência de união entre pinos de fibra de vidro e cimento resinoso autoadesivo nos terços cervical (p<0,013) e médio (p<0,026), sendo que o grupo da clorexidina 0,12% teve os melhores resultados. Isto permite sugerir novo protocolo de cimentação, com ação desinfetante (clorexidina), sem comprometer a resistência de união...

This study has evaluated the influence of different root canal dentin pre-treatments on the bond strength of radicular glass fiber posts. One hundred twenty bovine lower incisors were collecte. Thirty of them were selected and had their roots sectioned 16 mm from their apices. , Endodontic treatment and post space preparation to 8 mm deep were performed for cementation with self-adhesive resin cement. Samples were randomly divided into three according to surface treatments: Group I - irrigation with distilled water; Group II - irrigation with 17% EDTA; and Group III - irrigation with 0.12% chlorhexidine. Roots were then cut into 3 discs of 2 mm thick each and separated according to the region into cervical, medial and apical discs. A push-out bond strength test was performed by a universal testing machine at a crosshead speed of 0.5 mm/min. Data were analyzed with one way analysis of variance (ANOVA) and Tuckey test (p<0.05). Mean bond strength values showed significant difference between the groups in the cervical region (p<0.013) and medial region (p<0.026), that suggest a new bond protocol with disinfectant effect using 0.12% chlorhexidine without negative impact on bond strength...

Recovery of silver residues from dental amalgam

Dental amalgam residues are probably the most important chemical residues generated from clinical dental practice because of the presence of heavy metals among its constituents, mainly mercury and silver. OBJECTIVE: The purpose of this study was to develop an alternative method for the recovery of silver residues from dental amalgam. MATERIAL AND METHODS: The residue generated after vacuum distillation of dental amalgam for the separation of mercury was initially diluted with 32.5 percent HNO3, followed by precipitation with 20 percent NaCl. Sequentially, under constant heating and agitation with NaOH and sucrose, the sample was reduced to metallic silver. However, the processing time was too long, which turned this procedure not viable. In another sequence of experiments, the dilution was accomplished with concentrated HNO3 at 90ºC, followed by precipitation with 20 percent NaCl. After washing, the pellet was diluted with concentrated NH4OH, water and more NaCl in order to facilitate the reaction with the reducer. RESULTS: Ascorbic acid was efficiently used as reducer, allowing a fast reduction, thus making the procedure viable. CONCLUSIONS: The proposed methodology is of easy application and does not require sophisticated equipment or expensive reagents.

UV-visible and infrared spectroscopic studies of gamma irradiated commercial soda-lime silicate glasses

UV-visible and infrared absorption spectra of some selected commercial soda - lime - silicate glasses mixed with varied amounts of municipal glass cullet and doped with oxides of tin, manganese, and ceric before and after exposure to a high dose of gamma irradiation [5MR] were studied. XRF analysis showed that the municipal cullet contains high iron concentration and the results revealed that additions of [Mn + Ce + Sn] oxides produce colorless glasses even when containing high municipal cullet contents. It is generally observed that increasing the cullet content resulted in an optical spectrum consisting of three UV bands instead of two UV bands in case of low cullet content. The visible spectra reveal the resolution of two radiation induced bands at about 423 and 540 nm. Gamma irradiation also causes some of the absorption bands to be shifted in their positions. Experimental data are interpreted on the basis of current views on the spectroscopy of glasses

improved method for leaching of thorium in monazite using sodium hydroxide

The leaching of monazite with sodium hydroxide has been attempted. Factors such as time of leaching, concentration of sodium hydroxide sclution and temperature were tested with the hope to optimize the leaching efficiency. XRF technique was used in the determination of concentration. In this work Egyptian monastic leached by alkaline treatment in reflux instead of the pyrometallurgical process using mechanochemical treatment where grinding is carried out in the presence of sodium hydroxide and followed by pressure leaching in autoclave that gives an incongruent result. It has been found that the monazite was effectively decomposed in 2hr at - 130°C using 600g/1 sodium hydroxide in the reflux. The recovery of thorium by this method and under these conditions is about 98.1%. A mathematical formula is also deduced which enables the calculation of thorium concentration in ppm obtained from the leaching in reflux system under different conditions with a good agreement with the experimental values and that obtained from the XRF technique

Textile anionic dyes recovery using tri-n-butyl phosphate as carrier through supported liquid membrane.

The recovery of anionic dyes Acid Red10 B (CI Acid Violet 54) and Acid Pink BE (CI Acid Red 183) in flat type supported liquid membrane (SLM) using tri-n-butyl phosphate as carrier was studied. The parameters studied were the effect of feed phase pH, stripping reagent concentration, string speed and initial dye concentration on permeability of dyes. The influence of salt concentration such as sodium chloride and sodium sulphate on the dye recovery was examined. The reusability of membrane and kinetics of transport were also studied. The optimum conditions of transport are feed phase pH 1 +/- 0.1, 0.1 M sodium hydroxide as stripping phase, stirring speed at 500 rpm. The maximum recovery under optimum conditions was observed as 94.2 % for Acid Red10 B and 85.7 % for Acid Pink BE. The maximum permeability was 11.0 x 10(-6) m/s for Acid Red10 B and 7.7 x 10(-6) m/s for Acid Pink BE.

A study on sludge minimization during the treatment of pickling effluent.

In pickling industries, a lot of sludge is generated during the treatment of pickling effluent and there is severe problem of its disposal. Disposal of this sludge as per the Hazardous Waste (Management & Handling) Rules, 1989 is not easy. Its transportation and construction of lined disposal sites pose very severe problems. In the normal practice, the sludge is being disposed of at the sides of roads and railway tracks to fill low lying areas. This may cause serious health hazards. Considering these problems, a study has been undertaken to minimize the sludge generation during the treatment of pickling effluent by neutralizing it with lime, sodium hydroxide and combination of both. An attempt has been made to do an economic evaluation of the above process.

Studies on the acidity function H-of solutions of KOH and NaOH in ethanol water-mixtures using m-aminophenol dimer and o-aminophenol polymer as indicators

Attempts are made to calculate the value of H- from the spectrophotometrically determined molar extinction coefficients epsilon, epsilon A- and epsilon HA of m-aminophenol polymer and p- aminophenol dimer in solutions of KOH and NaOH in ethanol-water mixtures. The value of these coefficients are then used for the computation of the indicator ratios I of the different indicators in the various solutions. In addition, the pKa, values of the indicators in questions are obtained from [log I-log CoH] plots. The relating H- with medium composition disclose several maxima and minima, the locations of which depends on alkali concentration and identity. The basic strength in water and pure ethanol increases according to the order KOH > NaOH, whereas in ethanol-water mixtures it is a composite function of alkali concentration and medium composition