• Restorative Dentistry and Endodontics
• /
• v.33 no.5
• /
• pp.457-462
• /
• 2008

"Residual stress" can be developed during polymerization of the dental composite and it can be remained after this process was completed. The total amount of the force which applied to the composite restoration can be calculated by the sum of external and internal force. For the complete understanding of the restoration failure behavior. these two factors should be considered. In this experiment. I compared the residual stress of the recently developed nanofilled dental composite by ring slitting methods. The composites used in this study can be categorized in two groups. one is microhybrid type-Z250, as control group, and nanofilled type-Grandio, Filtek Supreme. Ceram-X, as experimental ones. Composite ring was made and marked two reference points on the surface. Then measure the change of the distance between these two points before and after ring slitting. From the distance change, average circumferential residual stress $({\sigma}{\theta})$ was calculated. In 10 minutes and 1 hour measurement groups, Filtek Supreme showed higher residual stress than Z250 and Ceram-X. In 24 hour group, Filtek showed higher stress than the other groups. Following the result of this experiment, nanofilled composite showed similar or higher residual stress than Z250, and when comparing the Z250 and Filtek Supreme, which have quite similar matrix components. Filtek Supreme groups showed higher residual stress.

• Restorative Dentistry and Endodontics
• /
• v.38 no.2
• /
• pp.65-72
• /
• 2013

Objectives: To evaluate the inhibitory effect of ursolic acid (UA)-containing composites on Streptococcus mutans (S. mutans) biofilm. Materials and Methods: Composite resins with five different concentrations (0.04, 0.1, 0.2, 0.5, and 1.0 wt%) of UA (U6753, Sigma Aldrich) were prepared, and their flexural strengths were measured according to ISO 4049. To evaluate the effect of carbohydrate source on biofilm formation, either glucose or sucrose was used as a nutrient source, and to investigate the effect of saliva treatment, the specimen were treated with either unstimulated whole saliva or phosphate-buffered saline (PBS). For biofilm assay, composite disks were transferred to S. mutans suspension and incubated for 24 hr. Afterwards, the specimens were rinsed with PBS and sonicated. The colony forming units (CFU) of the disrupted biofilm cultures were enumerated. For growth inhibition test, the composites were placed on a polystyrene well cluster, and S. mutans suspension was inoculated. The optical density at 600 nm ($OD_{600}$) was recorded by Infinite F200 pro apparatus (TECAN). One-way ANOVA and two-way ANOVA followed by Bonferroni correction were used for the data analyses. Results: The flexural strength values did not show significant difference at any concentration (p > 0.01). In biofilm assay, the CFU score decreased as the concentration of UA increased. The influence of saliva pretreatment was conflicting. The sucrose groups exhibited higher CFU score than glucose group (p < 0.05). In bacterial growth inhibition test, all experimental groups containing UA resulted in complete inhibition. Conclusions: Within the limitations of the experiments, UA included in the composite showed inhibitory effect on S. mutans biofilm formation and growth.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.20 no.2
• /
• pp.139-147
• /
• 1998

This study has been performed to evaluate the relationship between the remained mineral components in a decalcified bone matrix and an ectopic bone formation efficiency. The freezed rat diaphyseal cortical bones measuring 0.5cm in length were demineralized in heated 0.6N HCl at $60^{\circ}C$ for 5, 10, 15, 20, 25, 30, 35, 40 minutes, respectively, using a controlled heat ultrasonic cleaner. Each 1cc of decalcifying solution taken during decalcification procedure was used to calculate calcium content using calcium dignostics kit under 600nm of spectrophotomer. After decalcification, each specimen was also weighed. Then each prepared specimen was implanted into the dorsal pouch of 24 Sprague-Dawley rats divided into 8 groups by time course. The implants were harvested at 1, 2, and 3 weeks and prepared for routine H-E stain specimens to evaluate osteogenic activity. The results are as follows: 1. There was statistical significant difference in change of calcium concentration up to demineralization of 30 minutes and each allogenic bones decalcifed up to 20 minutes revealed 99.65% of decalcification in average. 2. There was statistical significant difference in change of weight in demineralized allogenic bone up to 20 minutes treatment but, no significant change was noted after that time. 3. The histologic analysis revealed active ectopic bone formation in the implanted allografts demineralized for 20, 25, 30 minutes, respectively. However, the other groups of allografts showed relatively poor osteoinductive activity. These findings suggest that complete decalcification with a minimized degeneration of collagen matrix is necessary to induce maximal osteogenesis by decalcified bone allograft.

• Journal of the Korean Chemical Society
• /
• v.33 no.3
• /
• pp.287-294
• /
• 1989

The optimum condition for the separation of priority pollutant phenols using isocratic elution has been determined. The elution behavior of eleven phenols has been also studied to interpret the retention. The reversed phase liquid chromatographic methods were performed on a ${\mu}$-Bondapak $C_{18}$ column with methanol-water, acetonitrile-water, and THF water mixtures as mobile phases. The COF method, where Snyder's solvent triangle concept was combined with a mixture-design statistical technique, was used to optimize the strength and selectivity of solvents for the separation of phenols. The optimum solvent composition, which gives a complete separation of eleven phenols, was found to be $MeOH:ACN:H_2O$ = 7:40:53. The plots of ln k' vs. -${\Delta}H^{\circ}$ and ${\Sigma}{\pi}$ of phenols showed relatively good linearities. Effect of van der Waals volume, pi-energy and hydrogen bonding on the retention of phenols were investigated. The following equation with the correlation coefficient of 0.9927 for ACN-water solvent system was obtained; $log^{k'}=2.515{\times}10^{-2}VWV-1.301{\times}10^{-1}E-3.674{\times}10^{-1}$