HARDNESS AND ELASTIC MODULUS ASSESSMENT FOR TWO ALIGNER MATERIALS BEFORE AND AFTER THERMOCYCLING: A COMPARATIVE STUDY

Orthodontic clear aligners as an alternative to traditional braces have become increasingly ubiquitous in the last few years. Therefore, understanding the properties of the aligner materials can help to produce more accurate results of the treatment and provide more data for orthodontists who are currently using or intend to use this technology. This study aimed to investigate the effect of thermocycling on some mechanical properties (Hardness and Elastic Modulus) of two thermoplastic products used in the fabrication of orthodontic aligners. Two thermoplastic products of Duran® 0.75 mm and Erkodur® 1 mm were used in this study. A specially prepared disk fabricated from risen material with dimensions of (15mm) in diameter and (6mm) in thickness which was fabricated with a 3D printer was used for hardness assessment. Twenty sheets were thermoformed over the round disk for each product. Whereas, for elastic modulus, a Dog bone specimen with dimensions 8 mm in width and 150 mm in length was made from resin by using a 3D printer. The shore D hardness test was used to measure the hardness of the two products before and after thermocycling. For elastic modulus, thermoplastic sheets that were less than 1mm in thickness were measured according to the ASTMD 882-02 and those with 1mm were measured according to the ASTMD 638-02a. The elastic modulus was measured using a tensile test by a universal testing machine before and after thermocycling. Erkodur model® was higher than Duran® in the hardness test before and after thermocycling. But, Erkodur model® showed significant, however, Duran® showed no significant change in hardness before and after thermocycling. The elastic modulus test for the two materials showed a significant difference between Duran® and Erkodur® models. The elastic modulus of Duran® was higher than Erkodur® before and after thermocycling. The hardness of the Erkodur® product was higher than that of Duran®, whereas the elastic modulus of the Duran® product was higher than Erkodur® before and after thermocycling. On the other hand, thermocycling reduces the hardness of the Erkodur® product more than that of Duran® and did not affect the elastic modulus of each product.

Split-bolus single-pass CT for vascular complications in acute pancreatitis: assessment of radiation dose and multi-phasic contrast enhancement compared to single-bolus multi-pass CT

AIM

To assess vascular contrast enhancement and radiation dose of split-bolus single-pass computed tomography (CT) compared to single-bolus multi-pass CT for acquiring a multi-phasic study.

MATERIALS AND METHODS

Patients who underwent CT for acute pancreatitis were included retrospectively. Thirty consecutive patients scanned with a split-bolus protocol were compared to 30 consecutive patients scanned with a single-bolus protocol. Data were collected on attenuation measurements (aorta, portal vein and spleen) and images were assessed for subjective vascular enhancement quality and splenic homogeneity. Radiation dose was measured by dose-length product (DLP).

RESULTS

There was no significant difference in the aortic (p = 0.88) or portal vein (p = 0.35) attenuation values between the two groups. The percentage of examinations reaching the target aortic and portal attenuation in the split-bolus group were 96.7% and 93.3%, and in the single-bolus group were 96.7% and 85.7%, respectively. The mean DLP was 492 mGy.cm for the single-bolus group and 940 mGy.cm for the split-bolus group (p < 0.0001). Subjective assessment revealed higher rates of splenic heterogeneity in the split-bolus group.

DISCUSSION

In acute pancreatitis, split-bolus imaging can produce arterial and venous enhancement comparable to a multi-pass technique with a significant reduction in radiation dose. Loss of temporal resolution and increased splenic heterogeneity are the main disadvantages. The low prevalence of pseudoaneurysms favours the lower-dose imaging technique.

[Work injuries in building construction, metal shaping, and food production sectors in Jericho District in the Palestinian territory]

Work injuries and accidents have a considerable impact on public and community health. This study targeted three work sectors: metal shaping, food production and building construction. Work injuries that occurred in these sectors were compared for the years 1999 and 2000 in Jericho District in the West Bank of Palestine. One hundred three injuries were examined and information recorded about the nature of the injury, site of injury in the body, direct cause of injury and some personal information about the injured worker. The most vulnerable group were young people in their twenties, and mostly those working in the metal shaping and building construction sectors. The kinds and sites of injuries varied. The data were compared with data from 1997, 1998 and 2001-2003, although only loosley as the available data about work injuries for these years were limited and inaccurate.

Prevalence of neuropsychiatric and mucous membrane irritation complaints among Palestinian shoe factory workers exposed to organic solvents and plastic compounds

BACKGROUND

Long-term exposure to organic solvents is associated with neuropsychiatric and mucus membrane irritation. In developing countries, efforts to secure a good working environment are inadequate and protection against chemical exposures is often neglected.

METHODS

In a cross-sectional survey, the prevalence of self-reported health complaints and the association with long-term exposure to solvents and plastic materials in the work environment was studied among 167 shoe-factory workers. Prevalences and adjusted prevalence ratios (PR)were calculated in Cox regression. 95% confidence intervals were estimated for PRs of adverse health effects.

RESULTS

Overall, the workers reported high prevalences of neuropsychiatric and mucus membrane complaints: headache (65%), mental irritability (53%), tingling of limbs (46%), and sore eyes (43%). Cleaning work was associated with tingling of limbs (PR = 1.8, 1.0-3.2), sore eyes (PR = 1.9, 1.1-3.3), and breathing difficulty (PR = 2.0, 1.0-3.9); plastic work was associated with tingling of limbs (PR = 1.8, 1.2-2.9)and sore eyes (PR = 1.7, 1.1-2.7); and varnishing was associated with breathing difficulty (PR = 1.9, 1.1-3.5).

CONCLUSIONS

The high prevalence of self-reported health complaints and the exposure-outcome association could be due to volatile organic solvents (dichloromethane, n-hexane)and plastic compounds (isocyanates and polyvinyl chloride). Absence of a satisfactory work environment is likely to contribute to high exposure levels.

Solvent exposures at shoe factories and workshops in Hebron City, West Bank

Exposure to organic solvents has been reported to increase the risks for acute and chronic health effects among shoe industry workers. In developing countries, protection against chemical exposures is often not provided. The study was conducted to identify working conditions and estimate the concentrations of organic solvents used in shoe factories and workshops in Hebron City. Personal interviews containing questions related to personal protective equipment (PPE) were used to identify working conditions, and samples collected from factories and workshops were analyzed using gas chromatography. Geometric means (GMs) were calculated for the solvents. Six major organic solvents were detected in the factories. Acetone (GM = 51.5 mg/m3, GSD = 3.82) was common in gluing tasks. Dichloromethane (GM = 47 mg/m3, GSD = 2.62) was common in cleaning tasks. Heptane, methylethyl ketone, n-hexane, and toluene were common in gluing tasks. Four major organic solvents were detected in the workshops: acetone (GM = 32.3 mg/m:3, GSD = 6.33), toluene (GM = 70.3 mg/m3, GSD = 3.06), n-hexane (GM = 19.4 mg/m3:, GSD = 2.65), and methylethyl ketone (GM = 130 mg/mM3, GSD = 1.5). 81% of the factory workers had never used respiratory protective equipment, and 92% had never used work clothes. 97% of the workers in the workshops had never used respiratory protective equipment, 94% had never worn gloves, and 90% had never used work clothes. Exposures to solvents in the absence of personal Protective equipment, tasks barriers, and mechanical ventilation can adversely affect health.

[The delayed split-skin coverage--use and advantages]

In 119 patients a "delayed skin flap transplantation" was carried out after excision of malignant melanomas. The skin graft can be stored in a refrigerator at 4 degrees C up to two weeks without damage to the transplant. The transplantation may be accomplished at any time, but is usually due 3 to 4 days postoperatively. Advantages of this method are decreased risk of local infection, early mobilisation of the patient and generally good cosmetic results.