Inverse modeling approach for evaluation of kinetic parameters of a biofilm reactor using tabu search.

The complex nature of biological reactions in biofilm reactors often poses difficulties in analyzing such reactors experimentally. Mathematical models could be very useful for their design and analysis. However, application of biofilm reactor models to practical problems proves somewhat ineffective due to the lack of knowledge of accurate kinetic models and uncertainty in model parameters. In this work, we propose an inverse modeling approach based on tabu search (TS) to estimate the parameters of kinetic and film thickness models. TS is used to estimate these parameters as a consequence of the validation of the mathematical models of the process with the aid of measured data obtained from an experimental fixed-bed anaerobic biofilm reactor involving the treatment of pharmaceutical industry wastewater. The results evaluated for different modeling configurations of varying degrees of complexity illustrate the effectiveness of TS for accurate estimation of kinetic and film thickness model parameters of the biofilm process. The results show that the two-dimensional mathematical model with Edward kinetics (with its optimum parameters as mu(max)rho(s)/Y = 24.57, Ks = 1.352 and Ki = 102.36) and three-parameter film thickness expression (with its estimated parameters as a = 0.289 x 10(-5), b = 1.55 x 10(-4) and c = 15.2 x 10(-6)) better describes the biofilm reactor treating the industry wastewater.

An in vitro study to compare the effectiveness of F-fle with ultrasonically activated K-fle to remove smear layer by using a scanning electron microscope.

AIM: The aim of this study was to compare the effectiveness of the F-fle with an ultrasonically activated #15 K-fle in removing the smear layer after biomechanical instrumentation along with irrigation of Saline, NaOCl and with or without a fush of EDTA. MATERIALS AND METHODS: Sixty decoronated human premolar teeth with a single canal were instrumented with ProTaper using S1, S2 and F1 series to produce the smear layer and randomly divided into two groups. Group A used Ultrasonics and group B used F-fle for activation of irrigants respectively. Each group was further divided in to three subgroups consisting of 10 teeth in each as I, II, III consisting of saline, NaOCl, NaOCl and EDTA as irrigants respectively. SEM micrographs were taken and amount of smear layer removal was analyzed by using Chi-square statistics tests. RESULTS: Most effective smear layer removal was seen only when EDTA was used. There was no statistically signifcant difference between the groups A and B in removal of smear layer. CONCLUSION: There was no increase in smear layer between use of F-fle when compared with the Ultrasonically activated K-fle. CLINICAL SIGNIFCANCE: The F-fle although does not have a superior effcacy than the ultrasonics in removal of smear layer from root canals but when used along with EDTA, can be an effective alternative for the dentists who are unable to bear the initial setup cost of ultrasonics.

Evaluation of fracture resistance of reattached vertical fragments bonded with fiber-reinforced composites: an in vitro study.

AIM: Aim of this in vitro study was to evaluate the resistance to fracture of vertically fractured and reattached fragments bonded with fiber-reinforced composites. MATERIALS AND METHODS: Root canals of 45 teeth were prepared, and the teeth were intentionally fractured into two separate fragments. Control groups (n = 15 each) consisted unfractured teeth with instrumented and obturated. Fractured teeth were divided into three groups (n = 15) and were attached using (1) dual-cure resin cement (RelyX U100), (2) dual-cure resin cement and polyethylene fiber (Ribbond), (3) dual-cure resin cement and glass fibers (stick-net). Force was applied at a speed of 0.5 mm/min to the root until fracture. RESULTS AND STATISTICAL ANALYSIS: Group 1 (RelyX U100 group) demonstrated lowest fracture resistance. Group 4 (control group) showed highest fracture resistance followed by group 2 (Ribbond group) and group 3 (Stick-Net groups). Statistically no significant difference was there between groups 2, 3 and 4. CONCLUSION: Vertically fractured teeth can be treated by filling the root canal space with dual-cure adhesive resin cement or by adding polyethylene fiber or glass fiber to increase the fracture resistance of the reattached tooth fragments, an alternative to extraction.

An in-vitro Evaluation of canal transportation and centering ability of two rotary Nickel Titanium systems (Twisted Files and Hyflex files) with conventional stainless Steel hand K-flexofiles by using Spiral Computed Tomography.

BACKGROUND: The purpose of this in-vitro study was to compare canal transportation and centering ability of Twisted and Hyflex Rotary Files with stainless steel hand k-flexofiles by using Spiral Computed Tomography. MATERIALS & METHODS: A total of 90 freshly extracted human mandibular single rooted Premolar teeth were selected. The crowns were flattened with steel disks and a final dimension of 18-mm WL was achieved for each tooth. Canals were divided randomly into 3 groups of 30 teeth each. Group I:Hyflex files, Group II:Twisted files, Group III:stainless steel hand k-flexofiles. Three sections from apical, mid-root, and coronal levels of the canal were recorded. All the teeth were scanned before and after instrumentation by using Spiral Computed Tomography. RESULTS: K-files showed highest transportation and less centered when compared to the Twisted and Hyflex rotary files. No significant difference was found between TF and Hyflex CM instruments. CONCLUSION: TF and Hyflex files shaped curved root canals without significant shaping errors when compared to the Hand stainless steel k-flexofiles. How to cite this article: Kumar BS, Pattanshetty S, Prasad M, Soni S, Pattanshetty KS, Prasad S. An in-vitro Evaluation of canal transportation and centering ability of two rotary Nickel Titanium systems (Twisted Files and Hyflex files) with conventional stainless Steel hand K-flexofiles by using Spiral Computed Tomography. J Int Oral Health 2013;5(5):108-15.

Estimating biofilm reaction kinetics using hybrid mechanistic-neural network rate function model.

This work describes an alternative method for estimation of reaction rate of a biofilm process without using a model equation. A first principles model of the biofilm process is integrated with artificial neural networks to derive a hybrid mechanistic-neural network rate function model (HMNNRFM), and this combined model structure is used to estimate the complex kinetics of the biofilm process as a consequence of the validation of its steady state solution. The performance of the proposed methodology is studied with the aid of the experimental data of an anaerobic fixed bed biofilm reactor. The statistical significance of the method is also analyzed by means of the coefficient of determination (R2) and model efficiency (ME). The results demonstrate the effectiveness of HMNNRFM for estimating the complex kinetics of the biofilm process involved in the treatment of industry wastewater.