Comparative study of the shear bond strength of various veneering materials on grade II commercially pure titanium

PURPOSE

To compare the shear bond strength of various veneering materials to grade II commercially pure titanium (CP-Ti).

MATERIALS AND METHODS

Thirty specimens of CP-Ti disc with 9 mm diameter and 10 mm height were divided into three experimental groups. Each group was bonded to heat-polymerized acrylic resin (Lucitone 199), porcelain (Triceram), and indirect composite (Sinfony) with 7 mm diameter and 2 mm height. For the control group (n=10), Lucitone 199 were applied on type IV gold alloy castings. All samples were thermocycled for 5000 cycles in 5-55℃ water. The maximum shear bond strength (MPa) was measured with a Universal Testing Machine. After the shear bond strength test, the failure mode was assessed with an optic microscope and a scanning electron microscope. Statistical analysis was carried out with a Kruskal-Wallis Test and Mann-Whitney Test.

RESULTS

The mean shear bond strength and standard deviations for experimental groups were as follows: Ti-Lucitone 199 (12.11 ± 4.44 MPa); Ti-Triceram (11.09 ± 1.66 MPa); Ti-Sinfony (4.32 ± 0.64 MPa). All of these experimental groups showed lower shear bond strength than the control group (16.14 ± 1.89 MPa). However, there was no statistically significant difference between the Ti-Lucitone 199 group and the control group, and the Ti-Lucitone 199 group and the Ti-Triceram group. Most of the failure patterns in all experimental groups were adhesive failures.

CONCLUSION

The shear bond strength of veneering materials such as heat-polymerized acrylic resin, porcelain, and indirect composite to CP-Ti was compatible to that of heatpolymerized acrylic resin to cast gold alloy.     

Lifespan extension and increased resistance to environmental stressors by N-Acetyl-L-Cysteine in Caenorhabditis elegans

OBJECTIVE:

This study was performed to determine the effect of N-acetyl-L-cysteine, a modified sulfur-containing amino acid that acts as a strong cellular antioxidant, on the response to environmental stressors and on aging in C. elegans.

METHOD:

The survival of worms under oxidative stress conditions induced by paraquat was evaluated with and without in vivo N-acetyl-L-cysteine treatment. The effect of N-acetyl-L-cysteine on the response to other environmental stressors, including heat stress and ultraviolet irradiation (UV), was also monitored. To investigate the effect on aging, we examined changes in lifespan, fertility, and expression of age-related biomarkers in C. elegans after N-acetyl-L-cysteine treatment.

RESULTS:

Dietary N-acetyl-L-cysteine supplementation significantly increased resistance to oxidative stress, heat stress, and UV irradiation in C. elegans. In addition, N-acetyl-L-cysteine supplementation significantly extended both the mean and maximum lifespan of C. elegans. The mean lifespan was extended by up to 30.5% with 5 mM N-acetyl-L-cysteine treatment, and the maximum lifespan was increased by 8 days. N-acetyl-L-cysteine supplementation also increased the total number of progeny produced and extended the gravid period of C. elegans. The green fluorescent protein reporter assay revealed that expression of the stress-responsive genes, sod-3 and hsp-16.2, increased significantly following N-acetyl-L-cysteine treatment.

CONCLUSION:

N-acetyl-L-cysteine supplementation confers a longevity phenotype in C. elegans, possibly through increased resistance to environmental stressors.     

Color temperature’s impact on task performance and brainwaves of school-age children

[Purpose] This study investigated color temperature’s impact on task performance. It presents a scientific analysis of brainwave and task performance time changes, and the results of a self-report type survey. [Subjects] Twenty-four elementary school fifth-grade boys and girls with no visual problems participated in the experiment. [Methods] Physiological reaction times of task performance were measured in a laboratory that could fix and maintain color temperature. Brainwave changes and the task performance times were measured, and a self-report questionnaire was conducted in order to measure of emotional reactions. [Results] Regarding the brainwave changes associated with color temperature, alpha waves were emitted in the O2 area when puzzle tasks were illuminated by orange light and low and high beta waves were emitted in the F3 area under white light. Five items (Brilliant, Soft, Lively, Relaxed, Open) were reported predominantly in responses to orange light in the self-report questionnaire. [Conclusion] The results of this study show that relaxation and stability are not assured when the color temperature is low, and that concentration and cognitive activity are not necessarily easier when the color temperature is high. The color temperature change when performing tasks promoted emotional factors more than brainwave, a biological change.Key words: Physical environment, Brainwave, Color temperature     

A comparison of driving errors in patients with left or right hemispheric lesions after stroke

[Purpose] The aim of this study was to compare the incidence of driving errors among patients with left or right hemispheric lesions due to stroke. [Subjects and Methods] Thirty stroke patients participated in the study. Driving errors were assessed using a virtual reality driving simulator. [Results] Significant differences were shown in center line crossing frequency, accident rate, brake reaction time, total driving error scores, and overall driving safety between participants with left or right hemispheric lesions. [Conclusion] Driving rehabilitation specialists should consider hemispheric function when teaching driving skills to stroke survivors, because patients with lesions in the left or right hemispheres after stroke show differences in driving skills.Key words: Stroke, Driving error, Hemispheric lesion     

Differences in the risk factors of reflux esophagitis according to age in Korea

The prevalence of gastroesophageal reflux disease in Korea has been believed to be low, but the incidence of gastroesophageal reflux disease in Korea is expected to increase because of the longer life expectancy and more ingestion of westernized food. The aim of this study was to report differences in the risk factors of reflux esophagitis (RE) according to age in Korea. We prospectively recruited the subjects who had RE among those who visited a health promotion center for upper gastrointestinal cancer surveillance at Hallym Medical Center (five institutions) between January 2008 and February 2009. The enrolled study participants comprised 742 subjects with RE and 1484 healthy controls. The independent risk factors of RE in young and adult group were male sex, smoking, coffee, body mass index ≥ 25, hiatal hernia, and Helicobacter pylori negativity. The risk factors of RE in elderly group were smoking, coffee, and hiatal hernia. The risk factors for RE according to age group were found to differ. In elderly group, Helicobacter pylori infection was not a significant protective factor contrary to young and adult groups.