EDTA-S: A novel root conditioning agent

Background: To evaluate the efficacy of 15% ethylenediaminetetraacetic acid (EDTA)-S (EDTA with soft soap) preparation for the removal of smear layer at human root surfaces. Materials and Methods: Twenty teeth indicated for extraction due to periodontal disease were sectioned using high speed cylindrical bur under copious irrigation. The root surfaces were instrumented with Gracey 7-8 curette (Hu-Friedy), 12 times to induce an "experimental smear layer". Following root planning, the root surface was cut using diamond disc and separated from the crown. Samples were randomly distributed into five groups. One group was control, saline and test groups were EDTA 15% alone, by active and passive applications (groups 2 and 3), and EDTA 15%+soft soap, by active and passive applications (groups 4 and 5). Specimens were then subjected to scanning electron microscope study. Smear layer removal was evaluated according to Sampaio et al., index. Results: EDTA-S removed the smear layer better than plain EDTA and the control group, while active application of the root conditioning agent had significant difference than the passive application of the agent. Conclusion: EDTA-S has favorable benefits over EDTA alone, and active application is better in comparison with passive application of root conditioning agent. Clinical Relevance: Removal of smear layer has been considered as an important step in periodontal regenerative therapy. Scaling and root planning alone with saline irrigation does not remove the smear layer. EDTA is a commonly used root conditioning agent in periodontal therapy. The addition of a detergent to EDTA proved to remove smear layer more efficiently than EDTA alone

AN ASSESSMENT OF THE NEWMARK METHOD FOR SOLVING CHAOTIC VIBRATIONS OF IMPACTING OSCILLATORS

The fourth-order Runge-Kutta method has been the preferred numerical integration scheme for solving chaotic problems in non-linear systems. This method is very accurate, but requires very small time-steps and four equation solutions per time-step. These drawbacks hinder the solution of chaotic problems in multi-degree-of-freedom (MDOF) systems. This paper presents the solution of the chaotic problem of impacting single-degree-of-freedom (SDOF) oscillators, using the Newmark method which is computationally efficient and unconditionally stable. The scheme incorporates an equilibrium iteration and variable time-stepping algorithm based on a convergence criteria which ensures that solution errors are minimized at each step. The results are compared with those obtained from the fourth-order Runge-Kutta method. It is concluded that the Newmark method with an adequate check on the solution accuracy could give qualitatively the same results as the Runge-Kutta method. The method has the advantage of an extension to MDOF real-life problems of chaos which could be solved using numerical techniques like FEM with limited computing effort. Such an extension is being pursued separately

FINITE-ELEMENT SIMULATION OF CHAOTIC VIBRATIONS OF A BEAM WITH NONLINEAR BOUNDARY-CONDITIONS

The solution of the chaotic vibration of non-linear mechanical systems involves the numerical integration of the governing equations of motion over a large time duration. This time duration should be adequately large to ensure that the transients die down and the solution captures the steady-state chaos. This demands that the integration scheme be stable, and accurate. The scheme which has found wide acceptance for chaotic problems is the fourth-order Runge-Kutta method. However, the Runge-Kutta method is not a preferred integration scheme for engineering solutions because it calls for four equation solutions per time-step and a small time-step to get accurate results from 'stiff equations' produced by the engineering structures. These drawbacks have restricted the study of chaos to single-or-limited number of degrees of freedom. This paper is an attempt to solve the chaotic vibration problem of structures with non-linear boundary conditions by the finite element method. The solution is attempted for the cantilever beam with one side-stop for which experimental results are available in the literature. This particular class of non-linearity has been chosen because of its abundance in and significance to the real-life structures. The authors' study shows that the temporally discrete solution of the spatially discrete model could capture the phenomenon of chaos. The authors expect this study to be useful for identifying the chaotic regimes for these structures in the physical coordinates of forcing amplitude and frequency. This, in turn, could be used for a more accurate prediction of fretting wear-limited life of these components

Irradiation of mangoes. I. Radiation-induced delay in ripening of Alphonso mangoes

Extension of storage life of unripe and mature Alphonse mangoes could he achieved at an optimum dose of 25 krads when irradiated under air, nitrogen, or carbon dioxide. Nitrogen atmosphere during irradiation is of some advantage in minimizing changes in organoleptic quality, ascorbic acid, and carotenoids, and at the same time allowing the least spoilage of fruit. Judging from skin color and fruit firmness, a six-day delay in ripening could be expected in fruits irradiated with 25 krads under nitrogen or air. Radiation effect on fruit skin is more prominent in terms of inhibition in chlorophyll disappearance and earotenoid formation than in ripening changes in the meat of the fruit

Irradiation of mangoes. II. Radiation effects on skin-coated Alphonso mangoes

The respiratory patterns of skin-coated and uncoated Alphonso mangoes, either unirradiated or irradiated under gaseous atmospheres like air, nitrogen, or carbon dioxide, were studied. The skins were coated with an emulsion made of an acetylated monoglyceride preparation. Skin-coated fruits show physiological damage presumably due to too much inhibition of respiration. This defect is rectified by a spurt in respiratory activity when fruits are irradiated in air or nitrogen. Irradiation in carbon dioxide, which also retards respiration, shows physiological damage which is reversible, the recovery of organoleptic qualities being possible to some extent. Suppression of respiration beyond an optimum level seems to be responsible for irreversible damage to the fruit. Organoleptic evaluation, analysis for fruit constituents, skin color, and pressure tests showed that storage life of the fruit can be increased by combining skin-coating with irradiation under either air or nitrogen