Technical quality of root canal treatment performed by undergraduate students using rotary instruments versus hand instruments: A Retrospective Study

Background: The technical quality of root canal treatment (RCT) may impact on the outcome. The quality of education received during undergraduate school may be linked to the quality of treatment provided in general dental practice. Objective: To compare the technical quality of RCT where rotary or manual step-back canal preparatory technique was employed in an undergraduate dental clinic in Turkey. Additionally, the present study aimed to compare radiographically commonly seen complications in both instrumentation systems. Materials and Methods: Dental records of 270 patients who received RCT undertaken by dental students were investigated by retrospective chart review. 565 root canals belonging to 270 patients were randomized into two groups [(rotary, n=280, and manual hand instruments, n=285)]. Root canal obturation was evaluated on the basis of the length of obturation being >2mm from the radiographic apex, with uniform radiodensity and good adaptation to root canal walls. Inadequate root canal obturation included cases containing procedural errors such as perforation, ledge, transportation, instrument separation. Descriptive statistics were used to define categorical variables (n, %) and the level of significance was set at 0.05. Results: The technical quality of RCT performed by undergraduate dental students was classified as 'adequate' in 75% and 53.7% of the cases, respectively for rotary and manual groups, respectively (p < 0.05). The highest procedural errors were seen in molars. Occurrence of procedural errors differed significantly between the groups, being 6.4% in rotary group and 12.3% in manual group (p = 0.017). However, occurrence of ledge formation was higher in manual group than that of rotary group (p = 0.007). Conclusion: In view of our findings, RCT performed by undergraduate dental students using rotary instrumentation systems is of higher technical quality and also has fewer procedural errors than manual instrumentation

Upgrading of the reactor waste obtained during borax production from tincal

Boron ores are used in the production of various boron compounds. One of the most important of them is borax obtained from tincal During borax production a large quantity of the boron oxide (B2O3) is lost with the reactor waste, Also, this waste causes different environmental problems when it discharged directly to the environment, In this study, the evaluation of the reactor waste in borax production was investigated to recover B2O3 and therefore to reduce the toxic effect of the waste. For this purpose, the reactor waste was leached by SO2-saturated water. It was found that about 90 % of B2O3 in the waste was recovered. In addition, about 80 % of CaO in the waste was dissolved in the leaching solution. A part of the dissolved CaO precipitated as CaSO3.1/2H(2)O and CaSO4.2H(2)O, and the other part remained as Ca(HSO3)(2) in the solution, It is possible that CaSO3. 1/2H(2)O and Ca(HSO3)(2) can be used in the paper industry and in other some industries. (C) 1999 Elsevier Science Ltd. All rights reserved

ELEMENTAL SULFUR FORMATION IN THE MEYERS COAL DESULFURIZATION PROCESS

The rate of formation of elemental sulfur on the surface of lignite particles during leaching by acidic ferric chloride was found to depend on the concentration and acidity of the ferric chloride, the particle size of the sample, the temperature and the rate of stirring. Generally, S formation increased during the first 40-45 min of leaching and subsequently decreases. It was more significant with small particles and high acidities

Desulphurization of two Turkish lignites in an entrained flow reactor

Desulphurization of Balkaya and Bolu-Mengen lignites by flash pyrolysis in an entrained flow reactor under nitrogen atmosphere was investigated. Experiments were conducted in a 450-750 degrees C temperature range. The change of sulphur types, the removal of total sulphur and volatile matter with pyrolysis temperature were found. The removal of the total sulphur and the volatile matter for Balkaya lignite at 750 degrees C were obtained as 42.2 and 72.7%, respectively, while these values are 57.0 and 66.8% for Bolu-Mengen lignite at the same temperature. (C) 1997 Elsevier Science B.V

KINETICS OF DESULFURIZATION OF NEVSEHIR-DADAGI COAL WITH FERRIC-CHLORIDE SOLUTIONS

The desulphurization of Nevsehir-Dadagi lignite with acidic ferric chloride solution and its kinetics and mechanism were investigated. It was found that the effects of the leaching temperature and particle size on the removal of pyritic sulphur are very significant. For larger particles (+ 250 and + 355 mum), the amount of pyritic sulphur removed was 20 wt%. For particles smaller than 250 mum a pyritic sulphur removal of 40-65 wt% was obtained. The removal of pyritic sulphur increased with increase in temperature. The increase of the FeCl3 concentration and the decrease of the acidity also increased the removal of pyritic sulphur. The desulphurization process was found to be well described by the unreacted core model of unchanging size. The overall controlling step was found to be diffusion from the ash layer. A rate equation including the reaction parameters for the decomposition of pyritic sulphur was also established. The activation energy and Arrhenius constant of the reaction were found to be 30.6 kJ mol-1 and 117.5 s-1, respectively