Papers by Mohammad Moghaddas
Journal of Dental Materials and Techniques, Jan 16, 2013
Complexity, 2015
ABSTRACT This article presents a novel neural network (NN) based on NCP function for solving nonc... more ABSTRACT This article presents a novel neural network (NN) based on NCP function for solving nonconvex nonlinear optimization (NCNO) problem subject to nonlinear inequality constraints. We first apply the p-power convexification of the Lagrangian function in the NCNO problem. The proposed NN is a gradient model which is constructed by an NCP function and an unconstrained minimization problem. The main feature of this NN is that its equilibrium point coincides with the optimal solution of the original problem. Under a proper assumption and utilizing a suitable Lyapunov function, it is shown that the proposed NN is Lyapunov stable and convergent to an exact optimal solution of the original problem. Finally, simulation results on two numerical examples and two practical examples are given to show the effectiveness and applicability of the proposed NN. © 2015 Wiley Periodicals, Inc. Complexity, 2015
Journal of dental research, dental clinics, dental prospects, 2014
Background and aims. This in vitro study evaluated the effect of delaying composite resin restora... more Background and aims. This in vitro study evaluated the effect of delaying composite resin restorative procedures bonded with total-etch and self-etch adhesive systems on microleakage following root canal irrigation with sodium hy-pochlorite (NaOCl) solution. Materials and methods. The roofs of pulp chambers and roots (1–2 mm below furcation) of 40 human first molar teeth were cut and pulp tissues completely removed. The teeth were randomly divided into two main groups (n = 20). Group E (experimental) was irrigated with 5% NaOCl and group C (control) was left untreated. For the experimental group, after obturation of root canals with gutta-percha and sealing the cavity with Cavit, the specimens were stored in artificialsaliva for two weeks. Then each group was divided into two subgroups according to the total-etch or self-etch adhesive application protocol: Scotchbond Multi-Purpose and Clearfil SE Bond. The specimens were restored with composite resin using each bonding agent: ...
The journal of contemporary dental practice, 2009
The aim of this study was to investigate the fracture resistance and failure mode of premolars re... more The aim of this study was to investigate the fracture resistance and failure mode of premolars restored with composite resin using various prefabricated posts. Sixty sound maxillary premolars were divided into four equal sized groups. All but the control group received endodontic treatment followed by placement of mesiodistocclusal (MOD) composite restorations (Tetric Ceram) as follows: Group T = no post, Group DT = fiber reinforced composite (FRC) post (DT Light), Group FL = prefabricated metal post (Filpost). The control group (C) had no cavities prepared. After thermal and load cycling, static load was applied at a 30 degrees angle until fracture. Failure modes were categorized as restorable and non-restorable. Data were analyzed using the analysis of variance (ANOVA) and Duncan tests (a = 0.05). The mean values of fracture loads (N) for all groups were: C (880+/-258); T (691+/-239); DT (865+/-269); and FL (388+/-167). Statistically significant differences (P<0.05) were observ...
Materials Science and Engineering: A, 2013
Mechanical properties a b s t r a c t A novel surface modifying technique has been used for fabri... more Mechanical properties a b s t r a c t A novel surface modifying technique has been used for fabrication of surface nanocomposite layer of Al5754/Si 3 N 4 . The effect of traverse and rotational speed on peak temperature was investigated. With the decrease of traverse speed the peak temperature was increased. Furthermore with increase of rotational speed the peak temperature was increased but in high rotational speed the variation of peak temperature was slight. Also the effect of traverse and rotational speed on stirred zone area was surveyed. The results showed that rotational speed is more effective on stirred zone area than traverse speed. The effect of rotational and traverse speed on grain size was also investigated. It was observed that with increasing the traverse speed to rotational speed ratio the grain size was increased with the exception of some rotational speed such as 1800 rpm. The Si 3 N 4 particles were uniformly distributed in the aluminum matrix. Also the effect of shoulder penetration on fabrication of surface nanocomposite layer was examined. It was observed that under special penetration shoulder, surface nanocomposite layer can be produced. The microhardness of surface nanocomposites produced under different rotational and traverse speed was also evaluated.
Journal of Conservative Dentistry, 2011
The aim of this retrospective study was to assess the survival rate and causes of failure of quar... more The aim of this retrospective study was to assess the survival rate and causes of failure of quartz fiber posts used to restore endodontically treated teeth. Thirty-eight patients with endodontically treated premolar and anterior teeth that were then restored with a coronoradicular quartz fiber post and extensive composite resin restorations were selected for participation in the study. The age of the restorations ranged from 1 to 6 years. Survival probabilities of the restorations as well as causes of failures were analyzed using the Kaplan-Meier analysis and the Logistic regression (α = 0.05). The overall cumulative survival rate (48.8%) was determined, while the survival probabilities after 1, 2, 4, 5, and 6 years of service were 88.37%, 60.95%, 45.71%, 32.65%, and 0%, respectively. The survival probability of endodontically treated teeth restored with a quartz fiber post and composite restorations is associated with the dental arch.
The Journal of Contemporary Dental Practice, 2010
AIM: The aim of this study was to compare the neutralizing effect of antioxidant agents on the mi... more AIM: The aim of this study was to compare the neutralizing effect of antioxidant agents on the microleakage of dental restorations in nonvital teeth after bleaching with carbamide peroxide. Also assessed was the correlation of the microleakage data between an electrochemical and a staining technique.METHODS AND MATERIALS: Following root canal therapy, 40 sound and similar human maxillary central incisors were randomly divided into four groups of 10 specimens each (n=10). The groups were subjected to one of four treatments: Group 1, bleaching with 10 percent carbamide peroxide for periods of eight hours per day for one week without an antioxidant agent; Group 2, bleaching with 10 percent carbamide peroxide plus 10 percent sodium ascorbate gel; Group 3, bleaching with 10 percent carbamide peroxide plus 10 percent sodium ascorbate gel combined with a surfactant; and Group 4, no bleaching treatment (control group). In all groups, the access cavities were restored using the Single Bond Plus Adhesive system and Z100 resin-based composite. After 1,000 thermal cycles, the teeth were dried and three layers of nail varnish were applied over the entire surface area to within 1.0 mm of the restoration. A PVC-covered copper wire, with 3.0 mm of exposed bare wire, was inserted apically 5.0 mm into the canal, which was obturated with gutta-percha and sealed with sticky wax and varnish at the apex. Leakage was continuously monitored for 40 days using a conductimetric method. The teeth were immersed in 0.5 percent basic fuchsine for 24 hours, followed by sectioning for microscopic examination at 16x magnification. The data were analyzed using ANOVA and the Newman-Keuls multiple comparison, Kruskal-Wallis, Mann-Whitney, and Spearman's rho tests (p<0.05).RESULTS: Based on the electrochemical results, cavities subjected to 10 percent sodium ascorbate gel combined with a surfactant displayed the least amount of microleakage while teeth that were bleached but not treated with an antioxidant exhibited significantly greater microleakage (p=0.007). These findings also were corroborated by the results of the staining experiments that showed a strong correlation between the electrochemical and staining findings (p=0.006) for the groups.CONCLUSION: After nonvital bleaching and the application of the antioxidant 10 percent sodium ascorbate, the addition of the surfactant 0.2 percent Tween 80 to the conventional antioxidant formulation significantly reduced microleakage.CLINICAL SIGNIFICANCE: The addition of a surfactant to the antioxidant formulation significantly reduced microleakage when it was applied after bleaching.
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Papers by Mohammad Moghaddas