No abstract available.
Breast* ; Silicon* ; Silicones*

PURPOSE: To compare the accuracy and efficacy of EDR2 film, a 2D ionization chamber array (MatriXX) and an amorphous silicon electronic portal imaging device (EPID) in the pre-treatment QA of IMRT. MATERIALS AND METHODS: Fluence patterns, shaped as a wedge with 10 steps (segments) by a multi-leaf collimator (MLC), of reference and test IMRT fields were measured using EDR2 film, the MatriXX, and EPID. Test fields were designed to simulate leaf positioning errors. The absolute dose at a point in each step of the reference fields was measured in a water phantom with an ionization chamber and was compared to the dose obtained with the use of EDR2 film, the MatriXX and EPID. For qualitative analysis, all measured fluence patterns of both reference and test fields were compared with calculated dose maps from a radiation treatment planning system (Pinnacle, Philips, USA) using profiles and gamma evaluation with 3%/3 mm and 2%/2 mm criteria. By measurement of the time to perform QA, we compared the workload of EDR2 film, the MatriXX and EPID. RESULTS: The percent absolute dose difference between the measured and ionization chamber dose was within 1% for the EPID, 2% for the MatriXX and 3% for EDR2 film. The percentage of pixels with gamma%>1 for the 3%/3 mm and 2%/2 mm criteria was within 2% for use of both EDR2 film and the EPID. However, differences for the use of the MatriXX were seen with a maximum difference as great as 5.94% with the 2%/2 mm criteria. For the test fields, EDR2 film and EPID could detect leaf-positioning errors on the order of -3 mm and -2 mm, respectively. However it was difficult to differentiate leaf-positioning errors with the MatriXX due to its poor resolution. The approximate time to perform QA was 110 minutes for the use of EDR2 film, 80 minutes for the use of the MatriXX and approximately 55 minutes for the use of the EPID. CONCLUSION: This study has evaluated the accuracy and efficacy of EDR2 film, the MatriXX and EPID in the pre-treatment verification of IMRT. EDR2 film and the EPID showed better performance for accuracy, while the use of the MatriXX significantly reduced measurement and analysis times. We propose practical and useful methods to establish an effective QA system in a clinical environment.
Electronics ; Electrons ; Silicon ; Water

STATEMENT OF PROBLEM: Fracture of composite resin core will be occurred by progress of crack. Bonding interface of different materials has large possibility of starting point of crack line. Therefore, the bond strength of glass fiber post to composite resin core is important for prevention of fracture. Purpose: This in vitrostudy tried to find out how to get the higher strength of glass fiber post to composite resin core through surveying the maximum load that fractures the post and core complex. MATERIALS AND METHODS: 40 specimens made with glass fiber Posts(Style post(R), Metalor, Swiss) and composite resin core(Z-100(R), 3M, USA) were prepared and loaded to failure with push-out type shear-bond strength test in a universal test machine. The maximum fracture load and fracture mode were investigated in the specimens that were restored with four different surface treatments. With the data, ANOVA test was used to validate the significance between the test groups, and Bonferroni method was used to check if there is any significant statistical difference between each test group. Every analysis was approved with 95% reliance. RESULTS: On measuring the maximum fracture load of specimens, both the treatments of sandblasted and acid-etched one statistically showed the strength increase rather than the control group(p<0.005). The scanning electric microscope revealed that sand blasting made more micro-retention form not only on the resin matrix but on the glass fiber, and acid-etching contributed to increase in surface retention form, eliminated the inorganic particles in resin matrix. Specimen fracture modes investigation represented that sand blasted groups showed lower bonding failure than no-sand blasted groups. CONCLUSION: Referring to the values of maximum fracture load of specimens, the bonding strength was increased by sand blasting and acid-etching.
Glass* ; Silicon Dioxide

In this study, we have conducted characterization of imaging performance for a flat panel digital X-ray detector using amorphous Selenium and a-Si TFT which was developed by the authors. The procedures for characterization were in concordance with internationally recommended standards such as IEC (international electrotechnical commission). The measures used for imaging performance characterization include response characteristic, modulation transfer function (MTF), detective quantum efficiency (DQE), noise power spectrum (NPS), and quantum limited performance. The measured DQEs at lowest and highest spatial frequencies were 40% and 25% respectively, which was superior to that of commercial products by overseas vendor. The MTF values were significantly superior to that of CR and indirect type DRs. The quantum limited performance showed the detector was limited by quantum noise at the entrance exposure level below 0.023 mR, which is sufficiently low for general X-ray examination.
Commerce ; Noise ; Selenium ; Silicon

To obtain the useful information for the status of working environment and health management of workers in manufacturing industries, comparision of results on the status of working environmental and health management of workers for 32 manufacturing industries in Chunam area from 1988 to 1989 was carried out. The results were as follows: 1. The rate of over-PEL(Permissible Exposure Limit) to for hazardous factors decreased significantly 23.5% in 1988, 18.3% in 1989 (p<0.05) and, the highest rate of over-PEL was the stone and sand handling industry, the highest rate of over-PEL was the dusty worplace as 38.5% in 1988, 35.2% in 1989. 2. The rate of workers exposed to hazardous factors in 1988 and in 1989 was 22.4% respectively, the rate of workers checked up special health examination was 40.1% in 1988, 75.3% in 1989. In stone and sand handling an dmedicochemical industries, none of workers exposed to hazardous factors was subjected to special health examination in 1988, but 75% of workers exposed to hazardous factors had checked up in 1989. 3. The 6 industries appointed as part-time factory physician among 17 industries which were supposed to have factory physician according to the Safety and Healthy Act of Korea, 6 out of 24 industries only appointed industrial hygienist, furthermore 4 out of 6 hygienists had another duty in addition to occupational hygiene itself.
Hygiene ; Korea ; Silicon Dioxide

OBJECTIVES: This study evaluated microtensile bond strength (microTBS) and short-rod fracture toughness to explain fractural behavior of repaired composite restorations according to different surface treatments. MATERIALS AND METHODS: Thirty composite blocks for microTBS test and sixty short-rod specimens for fracture toughness test were fabricated and were allocated to 3 groups according to the combination of surface treatment (none-treated, sand blasting, bur roughening). Each group was repaired immediately and 2 weeks later. Twenty-four hours later from repair, microTBS and fracture toughness test were conducted. Mean values analyzed with two-way ANOVA / Tukey's B test (alpha = 0.05) and correlation analysis was done between microTBS and fracture toughness. FE-SEM was employed on fractured surface to examine the crack propagation. RESULTS: The fresh composite resin showed higher microTBS than the aged composite resin (p < 0.001). Mechanically treated groups showed higher bond strength than non-mechanically treated groups except none-treated fresh group in microTBS (p < 0.05). The fracture toughness value of mechanically treated surface was higher than that of non-mechanically treated surface (p < 0.05). There was no correlation between fracture toughness and microtensile bond strength values. Specimens having high KIC showed toughening mechanism including crack deviation, microcracks and crack bridging in FE-SEM. CONCLUSIONS: Surface treatment by mechanical interlock is more important for effective composite repair, and the fracture toughness test could be used as an appropriate tool to examine the fractural behavior of the repaired composite with microtensile bond strength.
Aged ; Humans ; Silicon Dioxide

PURPOSE: To compare the dimensional accuracy of three impression techniques- a separating foil impression, a custom tray impression, and a stock tray impression. MATERIALS AND METHODS: A machined mandibular complete-arch metal model with special modifications served as a master cast. Three different impression techniques (n = 6 in each group) were performed with addition-cured silicon materials: i) putty-wash technique with a prefabricated metal tray (MET) using putty and regular body, ii) single-phase impression with custom tray (CUS) using regular body material, and iii) two-stage technique with stock metal tray (SEP) using putty with a separating foil and regular body material. All impressions were poured with epoxy resin. Six different distances (four intra-abutment and two inter-abutment distances) were gauged on the metal master model and on the casts with a microscope in combination with calibrated measuring software. The differences of the evaluated distances between the reference and the three test groups were calculated and expressed as mean (± SD). Additionally, the 95% confidence intervals were calculated and significant differences between the experimental groups were assumed when confidence intervals did not overlap. RESULTS: Dimensional changes compared to reference values varied between -74.01 and 32.57 µm (MET), -78.86 and 30.84 (CUS), and between -92.20 and 30.98 (SEP). For the intra-abutment distances, no significant differences among the experimental groups were detected. CUS showed a significantly higher dimensional accuracy for the inter-abutment distances with -0.02 and -0.08 percentage deviation compared to MET and SEP. CONCLUSION: The separation foil technique is a simple alternative to the custom tray technique for single tooth restorations, while limitations may exist for extended restorations with multiple abutment teeth.
Reference Values ; Silicon ; Tooth

PURPOSE: To evaluate the reproducibility of scan-based abutments using a blue light model scanner. MATERIALS AND METHODS: A wax cast abutment die was fabricated, and a silicone impression was prepared using a silicone material. Nine study dies were constructed using the prepared duplicable silicone, and the first was used as a reference. These dies were classified into three groups and scanned using a blue light model scanner. The first three-dimensional (3D) data set was obtained by scanning eight dies separately in the first group. The second 3D data set was acquired when four dies were placed together in the scanner and scanned twice in the second group. Finally, the third 3D data set was obtained when eight dies were placed together in the scanner and scanned once. These data were then used to define the data value using third-dimension software. All the data were then analyzed using the non-parametric Kruskal–Wallis H test (α=.05) and the post-hoc Mann-Whitney U-test with Bonferroni's correction (α=.017). RESULTS: The means and standard deviations of the eight dies together were larger than those of the four dies together and of the individual die. Moreover, significant differences were observed among the three groups (P < .05). CONCLUSION: With larger numbers of abutments scanned together, the scan becomes more inaccurate and loses reproducibility. Therefore, scans of smaller numbers of abutments are recommended to ensure better results.
Dataset ; Silicon ; Silicones

No abstract available.
Humans ; Outpatients* ; Silicon Dioxide*

Objective: In order to understand the dust concentration in the workplace of dust exposure enterprises in Shenxian. To evaluate the degree of occupational hazard factors of dust exposure enterprises. And provide basis for the formulation of occupational protection standards and management system of dust exposure enterprises. Methods: In February 2022, the dust concentration monitoring data of 89 dust exposure enterprises from 2017 to 2020 by the Shenxian Center for Disease Control and Prevention were collected, and the qualified rates of dust concentration detection of dust exposure enterprises in different years, dust types and enterprise sizes were analyzed. Results: A total of 89 dust enterprises were monitored from 2017 to 2020, 2132 dust samples were collected, and 1818 qualified samples were taken, with a total qualified rate of 85.3%. From 2017 to 2020, the dust detection qualified rates showed a year-by-year increase trend, 78.7% (447/568), 84.1% (471/560), 88.6% (418/472) and 90.6% (482/532), respectively, with statistically significant differences (χ(2)=36.27, P=0.003). The differences in the qualified rates of dust detection samples of silicon dust (66.1%, 41/62), grain dust (86.7%, 1549/1786), cotton dust (84.1%, 106/126) and wood dust (77.2%, 122/158) were statistically significant (χ(2)=29.66, P=0.002). The qualified rate of dust samples in large and medium-sized enterprises (95.1%, 1194/1256) was higher than that of small-sized enterprises (71.2%, 624/876), and the difference was statistically significant (χ(2)=1584.40, P=0.001) . Conclusion: The qualified rate of dust concentration monitoring results of dust exposure enterprises in Shenxian showed an increase trend year by year, while the pualified rate of dust concentration monitoring in small-sized enterprises was low, and the occupational hazard of silica dust was still severe.
Dust ; Silicon ; Wood ; Workplace