Air Blast Test Research Articles

Evaluation of potassium binoxalate gel and Nd:YAG laser in the management of dentinal hypersensitivity: a split-mouth clinical and ESEM study

Dentinal hypersensitivity is one of the oldest recorded complaints of discomfort to mankind and yet there appears to be no permanent treatment for this clinical condition. This study was designed to evaluate the clinical efficacy of potassium binoxalate gel and neodymium:yttrium-aluminum-garnet (Nd:YAG) laser on dentin hypersensitivity for a period of 9 months. Eighty teeth (20 subjects, 25-55 years old, M = F) were evaluated in a split-mouth design to receive potassium binoxalate (group A, 40 teeth) and Nd:YAG (group B, 40 teeth: 1 W, 10 Hz, and 60 s, irradiated twice). The diameter of output beam was about 300 μm with a distance of 2 mm between laser fiber or tip and tooth surface. The clinical efficacy was evaluated by air-blast test and cold-water test using visual analog scale. Electron microscopy photomicrographs were taken to confirm the results. Analysis was done at baseline; immediately post-treatment; and at 3, 6, 9 months post-treatment. Student's paired and unpaired T tests were used to evaluate the statistical analysis. Both treatment modalities were effective in reducing dentine hypersensitivity. However, Nd:YAG laser was better when intragroup comparison was made at 9 months post-treatment. Nd:YAG lasers is better in long-term treatment (up to 9 months) owing to the melting of dentinal tubules. However, due to depth of penetration of microcrystals, gel was better when ease of the procedure is considered. Nevertheless, both treatment modalities resulted in recurrence. Hence, further studies are needed to discover an agent, which can be considered as a "gold standard".

Comparative Evaluation of the Effects of 5% Sodium Fluoride Varnish and Neodymium-Doped Yttrium Aluminium Garnet (Nd:YAG) laser and their Combined Application on Dentin Hypersensitivity Treatment

Introduction: Dentin hypersensitivity is one of the most common complications that patients suffer from after periodontal therapies. So far many investigators have used different types of fluoride and laser for treatment of this complication. The aim of this study was to evaluate the effects of 5% sodium fluoride varnish and (Neodymium-Doped Yttrium Aluminium Garnet) Nd:YAG laser and their combined application on dentin hypersensitivity treatment. Methods: The study is a prospective interventional clinical trial. We selected a group of 9 patients with a total of 60 hypersensitive teeth. Each patient had at least 4 hypersensitive teeth. These 4 teeth were randomly placed in 4 different groups. Group1 didn’t receive any treatment. Group2 was treated with 5% sodium fluoride varnish (A Durashield Company product). Group3 was irradiated with Nd: YAG laser (1w, 20Hz, 120s). Group4 was treated by 5% sodium fluoride varnish and Nd: YAG laser combined (same parameters as group3). The assessment of the patients’ pain was done with cold air blast test (CAB) and visual analyzing scale (VAS) after stimulation using a probe and cold air. Patients’ pain was assessed before and just after treatment, and also 2 hours, 1 week and 2 weeks after treatment. For the assessment of pulp vitality we used the electric pulp test (EPT) at each session. SPSS 11.5 was used to process the results obtained. For the CAB and VAS changes in different groups, two-way repeated-measures ANOVA as well as Post-Hoc-Tukey tests were used. For the comparison of the different treatment groups at each session, one-way ANOVA, Post-Hoc-Tukey and or Mann-Whitney and Kruskal-Wallis tests were used. Results: VAS and CAB scores didn’t show any significant difference between different groups before treatment. Analysis of results obtained with two-way ANOVA test for repeated measures showed significant statistical differences for CAB and VAS scores in all groups between before and after treatment except for CAB score in control group. In the comparison of the fluoride varnish group and laser group alone with fluoride varnish-laser combined group using VAS and CAB scores, we found a significant difference. But we didn’t find any significant difference for the comparison between the varnish fluoride group and the laser group using the same score. Conclusion: The use of 5% sodium fluoride varnish and laser for treatment of dentin hypersensitivity is accompanied by a placebo effect. Although it appears that, if we omit the placebo effect, we had an improvement in all 3 treatment groups. But this improvement was more obvious for the treatment group4 (fluoride –laser) compared to other groups.

Comparative evaluation of two commercially available desensitizing agents for the treatment of dentinal hypersensitivity

A randomized clinical trail was designed to compare the efficacy of two commercially available desensitizing agents (fluoride varnish containing 6% sodium fluoride and 6% calcium fluoride and a gel containing 6% potassium nitrate and 0.11% fluoride ions) in the treatment of dentinal hypersensitivity. Randomized clinical trial. Twenty-one patients were selected. Subjects were evaluated using three different stimuli, i.e., tactile test, air blast test and cold water test. They were then randomly divided into two groups. Patients in group I were treated with fluoride varnish and group II patients were treated with gel containing 6% potassium nitrate and 0.11% fluoride ions. The patients were examined at baseline, immediately after application of the agent, at 1 week, 1 month and 3 months interval. Statistical analysis was done using unpaired "t" test, paired "t" test and Chi-square test with Yate's correction. The results were analyzed; it was seen that patients treated in group I showed significantly better results compared to group II patients at 1 month and 3 months interval. Teeth which required repeat dose and those which did not require repeat dose were comparable in number. Both the agents showed significant reduction in sensitivity at all time intervals compared to baseline. A comparatively significant reduction in sensitivity score was seen in patients treated with fluoride varnish and it appeared to be more effective in providing long-term relief against all the three test stimuli. Teeth with initial high sensitivity score required repeat doses, which was comparable for both the groups.

Close-range blast loading on empty recyclable metal beverage cans for use in sacrificial cladding structure

This article deals with the experimental and numerical blast study on a single empty recyclable metal beverage can. The idea is to make a macro-foam (sacrificial cladding structure) out of these cans to protect the main load bearing members of civil engineering structures from the air blast load. Close-range free air blast tests have been conducted to understand the crushing behaviour and the energy absorption of a single empty beverage can in detail. To conduct such an air blast test a special small-scale test set-up was designed and manufactured. The effect of skin plate surface area and its nature on the blast parameters is studied. Furthermore, the effect of inertia of the skin plate on the crushing performance of the beverage can is evaluated. Tests have been conducted with different plates (made of aluminium and sandwich composite materials) with different masses which represent the skin plate of the proposed sacrificial structure. The measured blast parameters from the experimental tests were compared with ConWep predicted data. Furthermore, the influence of the finite surface area of the skin plate on the clearing of the reflected pressure waves was also studied. The deformation behaviour and the corresponding energy absorption of empty beverage cans were captured. During the experimental blast tests it was observed that a part of the total reflected impulse (∼30%) was lost before it transfers to the non-sacrificial structure. Hence, in order to investigate this phenomenon Eulerian–Lagrangian coupled analyses were conducted using Hydrocodes. The results from these analyses showed that the diffraction and ground reflected pressure wave caused the loss in impulse. The results from the numerical studies have been compared and validated with the experimental results.

On the Use of Composite Charges to Determine Insensitive Explosive Material Properties at the Laboratory Scale

Laboratory-scale air-blast experiments an gram-range composite explosive charges are presented. The composite charges consist of a spherical booster charge surrounded by a concentric, spherical “candidate material” shell charge. By way of composite charge explosive characterization, the candidate explosive material is able to be characterized through the “removal” of the known booster effects. Using peak shock wave pressures, a method is developed to remove the booster effects from the composite charge’s signature to yield the sole effects of the candidate explosive material, permitting its characterization. Air-blast explosive tests are conducted using digital high-speed shadowgraph visualization to measure the resulting shock wave radial position as a function of time. Booster and composite charge data are converted to Mach number versus shock wave radius profiles and subsequently to peak shock wave pressure versus shock wave radius profiles for characterization of the shell material. Explosives tested include: PETN, RDX, HMX, and Alliant Bullseye® SP.

A double‐blind randomized‐controlled trial comparing the desensitizing efficacy of a new dentifrice containing carbonate/hydroxyapatite nanocrystals and a sodium fluoride/potassium nitrate dentifrice

Several dentifrices have shown to be effective in reducing dentine hypersensitivity (DH), but more effective products are needed. The aim of the study was to evaluate the desensitizing efficacy of a new dentifrice based on zinc-carbonate hydroxyapatite (CHA) nanocrystals. Using a double-blind, randomized design, the new dentifrice was compared with potassium nitrate/fluoride dentifrice (active control). The participant's DH was evaluated at baseline and after 4 and 8 weeks using airblast (primary outcome), tactile, cold water and subjective tests (secondary outcomes). The final sample consisted of 70 subjects with baseline DH; 36 received the new dentifrice and 34 the control one. Both dentifrices were largely effective; the percentage of score reduction from baseline to 8 weeks was greater than 28% for all tests (and greater than 55% for the cold water test) in both groups. As compared with controls, experimental subjects had a significantly greater improvement in the airblast test score (mean percentage of reduction of 46.0%versus 29.4% in controls) and the subjective test score (47.5%versus 28.1%, respectively), with both differences already being significant after 4 weeks. In contrast, there was no significant difference between groups for either the tactile or cold water tests at any time point and with any outcome. This study documented that the new dentifrice containing zinc-CHA nanocrystals significantly reduced dentinal hypersensitivity after 4 and 8 weeks, supporting its utility in clinical practice.

Large inelastic response of unbonded metallic foam and honeycomb core sandwich panels to blast loading

Sandwich panels constructed from metallic face sheets with the core composed of an energy absorbing material, have shown potential as an effective blast resistant structure. In the present study, air-blast tests are conducted on sandwich panels composed steel face sheets with unbonded aluminium foam (Alporas, Cymat) or hexagonal honeycomb cores. Honeycomb cores with small and large aspect ratios are investigated. For all core materials, tests are conducted using two different face sheet thicknesses. The results show that face sheet thickness has a significant effect on the performance of the panels relative to an equivalent monolithic plate. The Alporas and honeycomb cores are found to give higher relative performance with a thicker face sheet. Under the majority of the loading conditions investigated, the thick core honeycomb panels show the greatest increase in blast resistance of the core materials. The Cymat core panels do not show any significant increase in performance over monolithic plates.

Short‐Term Assessment of the Nd:YAG Laser With and Without Sodium Fluoride Varnish in the Treatment of Dentin Hypersensitivity – A Clinical and Scanning Electron Microscopy Study

The aim of the present study was to evaluate clinically and under scanning electron microscopy (SEM) the efficacy of Nd:YAG laser irradiation alone and in combination with 5% sodium fluoride varnish in the management of dentin hypersensitivity. The study was conducted on 40 patients divided into four groups who had at least one tooth of Grade III mobility with clinically elicitable dentin hypersensitivity. Following the pretreatment assessment of hypersensitivity using the visual analog scale (VAS) and cold air blast test, the selected tooth in all the groups received 1% citric acid treatment for 1 minute. Group 1 patients received no further treatment; group 2, 3, and 4 patients received additional treatment with 5% sodium fluoride varnish, Nd:YAG laser for 2 minutes, and a combination of 5% sodium fluoride varnish and Nd:YAG laser, respectively. Two hours following treatment, hypersensitivity was again assessed, and the teeth were extracted, sectioned, and scanned using scanning electron microscopy (SEM). The mean VAS score in group 1 showed a 27% increase from baseline, but groups 2, 3, and 4 showed a decrease of 33%, 44%, and 62%, respectively. The mean cold air blast score showed a 22% increase in group 1, but values decreased by 43%, 50%, and 83% in groups 2, 3, and 4, respectively. The number of patent tubules also progressively decreased from group 1 through group 4. The combination of Nd:YAG laser and 5% sodium fluoride varnish seems to show an impressive efficacy, when compared to either treatment alone, in treating dentin hypersensitivity. The SEM findings seem to relate to the clinical findings in that reduction in number/patency of tubules was associated with improvement in treatment efficacy.

Sound propagation over layered poro-elastic ground using a finite-difference model

This article presents an axisymmetric pressure-velocity finite-difference formulation (PV-FD) based on Biot's poro-elastic theory for modeling sound propagation in a homogeneous atmosphere over layered poro-elastic ground. The formulation is coded in a computer program and a simulation of actual measurements from airblast tests is carried out. The article presents typical results of simulation comprising synthetic time histories of overpressure in the atmosphere and ground vibration as well as snapshots of the response of the atmosphere-ground system at selected times. Comparisons with the measurements during airblast tests performed in Haslemoen, Norway, as well as the simulations by a frequency-wave number FFP formulation are presented to confirm the soundness of the proposed model. In particular, the generation of Mach surfaces in the ground motion, which is the result of the sound speed being greater than the Rayleigh wave velocity in the ground, is demonstrated with the help of snapshot plots.

STEEL-FIBRE-REINFORCED CONCRETE PANELS EXPOSED TO AIR BLAST LOADING.

Scaled explosive tests have been conducted to investigate the response of steel-fibre-reinforced concrete (SFRC) model structural elements. The structural elements were (a) rectangular panels, simply supported on two opposing shorter edges, (b) square panels, simply supported on all edges, and (c) fully fixed panels, in the form of an open box. Seven air blast tests were conducted. For each test, six panels were exposed simultaneously to air blast overpressure generated from the detonation of bare high explosives; charge weights ranged from 8kg to 40 kg. The panels were fabricated with different types of steel fibre, fibre concentration and conventional weldmesh reinforcement. Test results indicate that, as a construction material, SFRC can make an important contribution to the integrity and resistance of blast-resistant structures. Details of the experimental investigation and response of the panels are presented. A single-degree-of-freedom model, which incorporates an elastic-plastic structural resistance function for the dynamic analysis, is used to predict the response. The deformed configuration of the panels was computed at constant load steps, and the results were employed to evaluate the parameters of an equivalent dynamic model. Comparisons of computed and measured residual displacements are presented.