ORION laser target diagnostics

The ORION laser facility is one of the UK's premier laser facilities which became operational at AWE in 2010. Its primary mission is one of stockpile stewardship, ORION will extend the UK's experimental plasma physics capability to the high temperature, high density regime relevant to Atomic Weapons Establishment's (AWE) program. The ORION laser combines ten laser beams operating in the ns regime with two sub ps short pulse chirped pulse amplification beams. This gives the UK a unique combined long pulse/short pulse laser capability which is not only available to AWE personnel but also gives access to our international partners and visiting UK academia. The ORION laser facility is equipped with a comprehensive suite of some 45 diagnostics covering optical, particle, and x-ray diagnostics all able to image the laser target interaction point. This paper focuses on a small selection of these diagnostics.

Evaluation of the sensitivity and fading characteristics of an image plate system for x-ray diagnostics

Image plates (IPs) are a reusable recording media capable of detecting ionizing radiation, used to diagnose x-ray emission from laser-plasma experiments. Due to their superior performance characteristics in x-ray applications [C. C. Bradford, W. W. Peppler, and J. T. Dobbins III, Med. Phys. 26, 27 (1999) and J. Digit. Imaging. 12, 54 (1999)], the Fuji Biological Analysis System (BAS) IPs are fielded on x-ray diagnostics for the HELEN laser by the Plasma Physics Department at AWE. The sensitivities of the Fuji BAS IPs have been absolutely calibrated for absolute measurements of x-ray intensity in the energy range of 0-100 keV. In addition, the Fuji BAS IP fading as a function of time was investigated. We report on the characterization of three Fuji BAS IP responses to x-rays using a radioactive source, and discrete x-ray line energies generated by the Excalibur soft x-ray facility and the Defense Radiological Standards Centre filter-fluorescer hard x-ray system at AWE.

Soft x-ray measurements using photoconductive type-IIa and single-crystal chemical vapor deposited diamond detectors

Photoconductive detectors (PCDs) are routinely used alongside vacuum x-ray diodes (XRDs) to provide an alternative x-ray flux measurement at laser facilities such as HELEN at AWE Aldermaston, UK, and Omega at the Laboratory for Laser Energetics. To evaluate diamond PCDs as an alternative to XRD arrays, calibration measurements made at the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory are used to accurately calculate the x-ray flux from a laser-heated target. This is compared to a flux measurement using the Dante XRD diagnostic. Estimates indicate that the photoinduced conductivity from measurements made at Omega are too large, and calculations using the radiometric calibrations made at the NSLS agree with this hypothesis. High-purity, single-crystal, chemical vapor deposited (CVD) diamond samples are compared to natural type-IIa PCDs and show promising high resistivity effects, the corollary of which preliminary results show is a slower response time.

Effect of whitening agents containing carbamide peroxide on cariogenic bacteria

PURPOSE

The purpose of this study was to investigate the in vitro antibacterial effects of three different carbamide peroxide products (Nitewhite, Opalescence, and Proxigel) on cariogenic microorganisms (mutans streptococci [MS] and lactobacilli), and to evaluate the effects of a 10% carbamide peroxide solution (Proxigel) on salivary levels of MS and lactobacilli clinically.

MATERIALS AND METHODS

Growth inhibition studies were performed to determine the concentration and exposure time of carbamide peroxide to give total inhibition of recoverable growth of MS and lactobacilli. Paraffin-stimulated saliva samples were collected from subjects before and after 6 weeks of treatment with 10% carbamide peroxide in bleaching trays, and levels of MS and lactobacilli were determined.

RESULTS

The growth inhibition studies showed no visible growth of MS or lactobacilli at 24-, 48-, or 72-hour incubation, after a 2-hour exposure to 1% carbamide peroxide. Identical results were obtained with all three carbamide peroxide products. In the clinical study, the mean salivary MS levels, expressed as logarithm colony-forming units per milliliter (CFU/mL), were 5.38 for the pretreatment samples and 5.23 for the post-treatment samples. The differences were not statistically significant (p > .05). However, there was a reduction in logarithm lactobacilli counts from a mean of 4.12 pretreatment to a mean of 2.74 post-treatment. This was statistically significant (p < .05).

Cementless acetabular reconstruction after acetabular fracture

BACKGROUND

Total hip arthroplasty in patients with posttraumatic arthritis has produced results inferior to those in patients with nontraumatic arthritis. The use of cementless acetabular reconstruction, however, has not been extensively studied in this clinical context. Our purpose was to compare the intermediate-term results of total hip arthroplasty with a cementless acetabular component in patients with posttraumatic arthritis with those of the same procedure in patients with nontraumatic arthritis. We also compared the results of arthroplasty in patients who had had prior operative treatment of their acetabular fracture with those in patients who had had prior closed treatment of their acetabular fracture.

METHODS

Thirty total hip arthroplasties were performed with use of a cementless hemispheric, fiber-metal-mesh-coated acetabular component for the treatment of posttraumatic osteoarthritis after acetabular fracture. The median interval between the fracture and the arthroplasty was thirty-seven months (range, eight to 444 months). The average age at the time of the arthroplasty was fifty-one years (range, twenty-six to eighty-six years), and the average duration of follow-up was sixty-three months (range, twenty-four to 140 months). Fifteen patients had had prior open reduction and internal fixation of their acetabular fracture (open-reduction group), and fifteen patients had had closed treatment of the acetabular fracture (closed-treatment group). The results of these thirty hip reconstructions were compared with the intermediate-term results of 204 consecutive primary total hip arthroplasties with cementless acetabular reconstruction in patients with nontraumatic arthritis.

RESULTS

Operative time (p < 0.001), blood loss (p < 0.001), and perioperative transfusion requirements (p < 0.001) were greater in the patients with posttraumatic arthritis than they were in the patients with nontraumatic arthritis. Of the patients with posttraumatic arthritis, those who had had open reduction and internal fixation of their acetabular fracture had a significantly longer index procedure (p = 0.01), greater blood loss (p = 0.008), and a higher transfusion requirement (p = 0.049) than those in whom the fracture had been treated by closed methods. Eight of the fifteen patients with a previous open reduction and internal fixation required an elevated acetabular liner compared with one of the fifteen patients who had been treated by closed means (p = 0.005). Two of the fifteen patients with a previous open reduction and internal fixation required bone-grafting of acetabular defects compared with seven of the fifteen patients treated by closed means (p = 0.04). The thirty patients treated for posttraumatic arthritis had an average preoperative Harris hip score of 41 points, which increased to 88 points at the time of follow-up; there was no significant difference between the open-reduction and closed-treatment groups (p = 0.39). Twenty-seven patients (90%) had a good or excellent result. There were no dislocations or deep infections. The Kaplan-Meier ten-year survival rate, with revision or radiographic loosening as the end point, was 97%. These results were similar to those of the patients who underwent primary total hip arthroplasty for nontraumatic arthritis.

CONCLUSIONS

The intermediate-term clinical results of total hip arthroplasty with cementless acetabular reconstruction for posttraumatic osteoarthritis after acetabular fracture were similar to those after the same procedure for nontraumatic arthritis, regardless of whether the acetabular fracture had been internally fixed initially. However, total hip arthroplasty after acetabular fracture was a longer procedure with greater blood loss, especially in patients with previous open reduction and internal fixation. Previous open reduction and internal fixation predisposed the hip to more intraoperative instability but less bone deficiency.

A comparison of partial and full mouth scoring of plaque and gingivitis in oral hygiene studies

The clinical testing necessary to demonstrate the safety and efficacy of new toothbrushes is complex and expensive. Any modification of methodology that could reduce complexity and cost without compromising quality would benefit both investigators and the public. Results from an 8-week toothbrush study were assessed for the use of partial as compared to full-mouth evaluations. The potential utility of an objective, minimally-invasive bleeding index for the evaluation of gingivitis was also tested. 2 partial evaluations, half-mouth and molar/anteriors, revealed decrements in modified gingival index (MGI), bleeding index and plaque index that were statistically significant and similar in magnitude to those derived from full-mouth examinations. % decrements in MGI and bleeding index based on the Ramfjord teeth were not significant statistically. Results for the new sulcular bleeding index were essentially similar to those for the MGI. However, the bleeding index offered the advantage of improved objectivity for use in both white and non-white subjects. These results suggest that partial evaluations and the new bleeding index may be useful elements in the design of toothbrush efficacy studies.

Change in pH of plaque and 10% carbamide peroxide solution during nightguard vital bleaching treatment

The purpose of this study was to evaluate in vivo changes in the pH of plaque and of a 10% carbamide peroxide solution occurring within the bleaching guard during a 2-hour nightguard vital bleaching procedure. Baseline pH values for plaque and the carbamide peroxide solution were established. A small hole was placed in the anterior interproximal region of the guard to allow placement of the pH electrode. The pH of the carbamide peroxide solution was measured at 5-minute intervals. After 2 hours, the guard was removed and pH of the plaque was remeasured. The procedure was repeated three times on each of four subjects. The mean baseline pH reading for plaque was 6.31 and mean final pH reading was 6.86. The difference was statistically significant. At initial placement of the carbamide peroxide-filled guard, the mean intraguard pH was 4.50 (range of 2.80 to 7.80). The mean peak intraguard pH of 8.06 (range of 7.30 to 8.43), which was significantly different from baseline, was obtained within 31 minutes. The pH of plaque, saliva, and a 10% carbamide peroxide bleaching solution within the guard increased significantly during bleaching and remained significantly elevated for the duration of the study (2 hours).

Salivary pH changes during 10% carbamide peroxide bleaching

The purpose of this study was to evaluate the effect on salivary pH of a 10% carbamide peroxide solution when used with a custom-fitted guard for bleaching teeth. Baseline pH values were established for unstimulated saliva and on saliva produced while wearing an empty guard. After insertion of a guard half filled with Proxigel, salivary pH measurements were made at 5-minute intervals until the values returned to baseline levels. Mean salivary pH values were 6.81 +/- 0.11 for unstimulated samples and 6.91 +/- 0.18 after insertion of the empty guard. After insertion of the filled guard, there was a statistically insignificant decrease in salivary pH during the first 5 minutes, followed by an increase above baseline at 10 minutes, to a mean peak value of 7.32 +/- 0.27 at 15 minutes. The difference between the baseline values and the mean peak value at 15 minutes was statistically significant. The results of the study indicated that the pH of saliva increased significantly during the first 15 minutes of nightguard vital bleaching and did not significantly drop below baseline in the first 2 hours after insertion with a moderately low-pH solution.

Evaluating spatter and aerosol contamination during dental procedures

A pilot study evaluated the distribution of spatter and aerosols generated by high-speed instrumentation. In the first phase, fluorescent dye was added to the handpiece water supply. In the second, blood agar culture plates were placed in the operatory. Results show that contamination from spatter and aerosol dissemination remains a significant hazard for dental personnel.