• Journal of the korean academy of Pediatric Dentistry
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• v.23 no.3
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• pp.640-658
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• 1996

The purpose of this study was to examine the mechanism of improving acid resistance of Nd-YAG laser irradiated tooth enamel and determine the most effective energy density for improving acid resistance. The bovine tooth enamel were lased with a pulsed Nd-YAG laser. The energy densities of exposed laser beam were varied from 10 to $70\;J/cm^2$. To investigate the degree of improving acid resistance by irradiation, all the samples were submerged to demineralize in 0.5 N $HClO_4$ solution for 1 minute. After 1 minute, 0.05 % $LaCl_3$ was added to the solution for interrupting the demineralization reaction. The amounts of dissolved calcium and phosphate in the solution were measured by using an atomic absorption spectrophotometer and the UV/VIS spectrophotometer, respectively. To examine the mechanism of improving acid resistance, X-ray diffraction analysis, infrared spectroscopy, and scanning electron microscopy were taken. The X-ray diffraction pattern of the samples were obtained in the $10^{\circ}{\sim}80^{\circ}2{\theta}$ range with $Cu-K{\alpha}$ radiation using M18HF(Mac Science Co.) with X-ray diffractometer operating at 40 KV and 300 mA. The infra-red spectra of the ground samples in 300 mg KBr pellets 10 mm diameter were obtained in the $4000cm^{-1}\;to\;400cm^{-1}$ range using JASCO 300E spectrophotometer. The scanning electron microscopy was carried out using JSM6400(JEOL Co.) with $500{\sim}2000$ times magnification. The results were as follow 1. The concentration of calcium dissolved from laser irradiated enamel with $50J/cm^2$ was significantly lesser than that of unlased control group (p<0.05) 2. From the result of the X-ray diffraction analysis, $\beta$-TCP, which increases acid solubility, was identified in lased enamel but the diffraction peaks of (002) and (004) became sharp with increasing energy density of laser irradiation. This means that the crystals in lased samples were grown through the c-axis and subsequently, the acid solubility of enamel decreased. 3. The a-axis parameter was slightly increased by laser irradiation, whereas the c-axis parameter was almost constant except for a little decrease at $50J/cm^2$. 4. In the infra-red spectra of lased enamels, phosphate bands ($600{\sim}500cm^{-1}$), B-carbonate bands (870, $1415{\sim}1455cm^{-1}$), and A-carbonate band ($1545cm^{-1}$) were observed. The amounts of phosphate bands and the B-carbonate bands were reduced, on the other hand, the amount of the A-carbonate band was increased by increase the energy density. 5. The SEM experiments reveal that the surface melting and recrystallization were appeared at $30J/cm^2$ and the cracks were observed at $70J/cm^2$. From above results, It may be suggested that the most effective energy density for improving acid resistance of tooth enamel with the irradiation of Nd-YAG laser was $50J/cm^2$. The mechanism of improving acid resistance were reduction of permeability due to surface melting and recrystallization of lased enamel and reduction of acid solubility of enamel due to decrease of carbonate content and growth of crystal.

• Journal of the korean academy of Pediatric Dentistry
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• v.33 no.3
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• pp.510-521
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• 2006

This investigation was undertaken to examine the extent to which tooth size and arch dimension each contribute to dental crowding. The sample included 50 subjects with well aligned dentition (25 males, 25 females) and those of 40 subjects with gross dental crowding(20 males, 20 females). Plaster model and digital model made from alginate impression taken at the one visit. Tooth size, arch length, arch perimeter, intercanine width and intermolar width was measured on the plaster and digital models. The findings in this study lead to the following conclusions. 1. In maxilla, the mesiodistal diameters of lateral incisor and premolars of the crowded group were significantly larger than those of the normal occlusion group (P<0.05). 2. In mandible, the mesiodistal diameters of central incisor, canine and premolars of crowded group were significantly larger than those of the normal occlusion group (P<0.05). 3. In maxilla, arch perimeter and intermolar width of crowded group were significantly smaller than normal occlusion group but intercanine width of crowded group were larger than normal occlusion group (P<0.05). There was no significantly difference in arch length (P>0.05). 4. In mandible, arch perimeter of crowded group was smaller than normal occlusion group(P<0.05). There were no difference in arch length intermolar width and intercanine width (P>0.05) 5. In the analysis of correlation coefficients of arch length discrepancy with variables, arch perimeter, intermolar width and mesiodistal width of 2nd premolar showed positive correlations in maxilla. 6. There was a significant difference between tooth width measurements made by the 2 methods, with all the digital model measurement larger than plaster model measurements (P<0.05) : the magnitude of the differences does not appear to be clinically relevant. 7. In the analysis for reproducibility, the plaster model measurement was showed lower degree of correlation between 1st and 2nd measurement than digital model.

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.2
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• pp.278-286
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• 2008

Many studies regarding Casein phosphopeptides-amorphous calcium phosphate(CPP-ACP) have demonstrated the remineralization ability on the demineralized enamel surface. A question is still remained that how deep can the calcium (Ca) and phosphorus (P) ions supplied by the CPP-ACP paste penetrate into the enamel subsurface. The aims of this study were to measure the penetrating depth of Ca and P ions in the demineralized human enamel in vitro, and were to determine the amount and depth of Ca and P ions according to the duration. The amount and depth of Ca and P ions were measured by microscopic observation with Field Emission Scanning Electron Microscopy (FE-SEM; LEO SUPRA 55, Carl Zeiss, Germany) and Energy Dispersive X-ray Spectrometer (EDS; GENESIS 2000, EDAX, USA: Linescan of Calcium and Phosphorus). Freshly extracted four human 1st premolars were obtained from the Dept. of Pediatric Dent., Kyung Hee Univ. Buccal surfaces of the 1st premolars were covered with nail varnish to form a window on the middle third of buccal surface. All of the teeth with enamel windows were immersed in a solution of 0.1 M lactic acid, Carbopol C907 (carboxypolymethylene BF Goodrich, Cleveland, OH, USA) at pH 4.8, and then incubated for 7 days. Each tooth crown was sawn in half through the midline of buccal window along the long axis of premolar. The four blocks of premolars were immersed in a 10-times diluted solution of CPP-ACP paste (Tooth Mousse, GC Corp., Tokyo, Japan) for 1, 2, 3 and 5 weeks while the rests were immersed in a placebo solution (distilled water) for the same duration. Each specimen was embedded in epoxy resin, and was sectioned perpendicular to the window, using a water-cooled diamond blade saw. The spectrum density indices of Ca and P were measured in the sound, de- and remineralized enamels by FE-SEM and EDS. The Student's t test was performed to compare the Spectrum Density Indices (SDI) of sound, re-and demineralized enamels, and to compare the differences among the durations. Followings are the conclusion : 1. The penetration depth of the remineralizing ions (Ca & P) of CPP-ACP paste is related to the depth of demineralized enamel (approximately $1050{\sim}1350{\mu}m$). It is revealed that the penetration depth of both ions reaches full thickness of decalcification and even slightly into the sound enamel. 2. The Ca & P levels of remineralized enamels in 1, 2 weeks were significantly higher than those of the sound enamels (p<0.05). 3. No statistically significant difference of Ca & P levels was found in relation with the increasing duration of remineralization (p>0.05).

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.2
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• pp.268-277
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• 2008

Authors evaluated 1171 patients at the department of Pediatric Dentistry in Kyoungpook National University Hospital through clinical records and radiographs. And the following features were studied ; age, sex distribution, number of mesiodens per patients, cause of discovery of mesiodens, location, status of eruption, shape and orientation of crown, complication, dental age of adjacent upper incisor tooth at the time of surgical extraction of mesiodens and the relationship between the resolution rate of complication after extraction of mesiodens and the dental age of adjacent upper incisor tooth, length of diastema, the eruption status of lateral incisor and the crowding status of premaxilla. The followings are the results : 1. The cause of discovery of mesiodens were as follows ; delayed eruption of the permanent incisors in 13.8%, midline diastema in 11.6%, radiographs taken for other reasons in 23.4% and for caries treatment in 15.1%. 2. Complication due to the presence of mesiodens did not occur in 36.8%, delayed eruption of adjacent teeth was observed in 16.1%, midline diastema in 34.4%, rotation in 8.8%, displacement in 2.4%, and crowding in 1.0% of all evaluated patients. 3. As for the dental age of adjacent upper incisor tooth at the time of surgical extraction of mesiodens, below 1/3 of total root length were observed in 3.5%, $1/3{\sim}1/2$ of total root length in 19.9%, $1/2{\sim}2/3$ of total root length in 54.7% and over 2/3 in 21.9% of all evaluated patients. 4. Resolution rate of delayed eruption after the extraction of mesiodens was significant higher in the group with the root length below 1/2. Resolution rate of midline diastema was significant higher in the group with diastema width below 3mm and with non-crowding of adjacent upper incisor teeth.

• Journal of Radiation Protection and Research
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• v.32 no.3
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• pp.123-133
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• 2007

Z-axis automatic tube current modulation technique automatically adjusts tube current based on size of body region scanned. The purpose of the current study was to compare noise, and radiation dose of multi-detector row CT (MDCT) of lower extremity performed with Z-axis modulation technique of automatic tube current modulation with manual selection fixed tube current. Fifty consecutive underwent MDCT venography of lower extremity with use of a MDCT scanner fixed tube current and Z-axis automatic tube current modulation technique (10, 11 and 12 HU noise index, $70{\sim}450\;mA$). Scanning parameters included 120 kVp, 0.5 second gantry rotation time, 1.35:1 beam pitch, and 1 mm reconstructed section thickness. For each subject, images obtained with Z-axis modulation were compared with previous images obtained with fixed tube current (200, 250, 300 mA) and with other parameters identical. Images were compared for noise at five levels: iliac, femoral, popliteal, tibial, and peroneal vein of lower extremity. Tube current and gantry rotation time used for acquisitions at these levels were recorded. All CT examinations of study and control groups were diagnostically acceptable, though objective noise was significantly more with Z-axis automatic tube current modulation. Compared with fixed tube current, 2-axis modulation resulted in reduction of CTDIvol (range, $-6.5%{\sim}-35.6%$) and DLP (range, $-0.2%{\sim}-20.2%$). Compared with manually selected fixed tube current, 2-axis automatic tube current modulation resulted in reduced radiation dose at MDCT of lower extremity venography.

• Journal of Aquaculture
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• v.4 no.2
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• pp.73-84
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• 1991

Underground sea water is widely utilized for land based aquaculture in Cheju province, Korea nowadays. Salinity of this water($20{\~}30$ ppt) is slightly lower than natural sea water but because of its good water quality and temperature which is maintained at $16{\~}18^{\circ}C$ all year-round, many fish farmers are using this water for finfish culture. To evaluate the possibility of utilizing underground sea water for the seed production of the flounder, Paralichthys olivaeceus, hatching rate of fertilized eggs, survival rate of hatched larvae, and growth rate of the juveniles were tested with various salinity levels ranged from 14.1 ppt to 40.2 ppt. The salinity ranges which showed over $70{\%}$ survival rate for fertilized eggs to hatchout were 33.7 ppt${\~}$40.2 ppt, for hatched larvae to 2-day-old were 20.6 ppt${\~}$40.2 ppt, from 10-day-old to 12-day-old were 27.2 ppt${\~}$40.2 ppt, and from 45-day-old to 47-day-old were 20.6 ppt${\~}$40.2 ppt. Two hundred day old fingerlings showed no mortality when exposured to 7.6 ppt${\~}$40.2 ppt for 2 days. All fish died within 3 days when 45-day-old juveniles were transferred directly from normal sea water to 14.1 ppt sea water. However, they were all survived when transferred first to 20.6 ppt for 3 days then to 14.1 ppt sea water. The highest growth rates of fingerlings reared at 4 different salinities (33.7, 27.0, 31.0, or 15 ppt) were obtained at the 27 ppt group followed by 33.7, 21.0, 15 ppt respectively. The relationship between the days of rearing (X) and the total length of the fingerlings were as follows. $33.7\%$ group : Y=8.8109 + 0.1104X(r=0.999) $27.0{\%}$ group : Y=8.6797 + 0.1208X(r=0.997) $21.0{\%}$ group : Y=8.4081 + 0.1052X(r=0.990) $15.0{\%}$ group : Y=8.4309+ 0.0995X(r=0.990)

• Journal of Aquaculture
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• v.4 no.2
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• pp.111-128
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• 1991

In puan area the environmental surveys were carried out at two farms of hard clam, Meretrix lusoria from April 1987 to November 1978 in order to know heather the farm environments could be rehabilitated for the cultivation of hard clam or not. The range of temperature of surface seawater was $10.7{\~}27.4^{\circ}C$, pH $7.6{\~}8.2$, salinity $22.3{\~}30.3$ ppt, COD $0.20{\~}4.71\;mg/{\ell}$, sulfide $0.04{\~}0.22\;{\mu}g-at./{\ell}$, suspended solid $34.8{\~}199.3\;mg/{\ell}$ chlorophyll a $3.71{\~}49.02\;mg/m^3$, TIN $2.01{\~}24.47\;{\mu}g-a5./{\ell}$, phosphate $0.60{\~}11.03\;{\mu}g-at./{\ell}$ and silicate $4.04{\~}476.36\;{\mu}g-at./{\ell}$. The range of temperature of substratum (bottom soil) was $14.2{\~}29.7^{\circ}C$, pH $8.3{\~}9.5$, water content of substratum was $0.28{\~}0.49\;mg/g$ dried mud, COD $2.80{\~}50.94\;mg/g$ dried mud, total organic matter $1.05{\~}1.97\%$ concentration of total Kjedhal nitrogen $31.9{\~}194.9\;{\mu}g./{\ell}$ dried mud, and sulfide $0.032{\~}0.133\;mg/g$ dried mud. Fine sand was dominant ranging over $92{\~}95\%$ and silt and clay was $2.8{\~}8.1\%$ of the composition of substratum. Some residual agricultural chemicals, ${\alpha},\;{\beta},\;{\gamma}$-BHC, heptachlor, heptachlor-epoxide, aldrin, DDE, DDT and dieldrin were detected in hard clams collected from Puan areas. Especialy, more chemical were detected during the period of rainfalls. From above results, it is considered that the hard clam frams were not yet recovered from deteriorated conditions for aquaculture.

• Journal of Korean Society of Forest Science
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• v.96 no.3
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• pp.307-316
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• 2007

Yellow poplar (Liriodendron tulipifera L.) has low germination rate relatively other species, so the seedling production of Yellow poplar is a hard task. Accordingly this study was conducted to determine the optimal germination conditions for healthy seedling production and to promote survival rate after afforestation. Gemination percentage was examined at different media and seed covering materials using planting flats in the greenhouse. The best germination percentage was observed in sand for media and compound soil for covering materials. But it was time to transplant, seedlings became a poor character (i.e. height, root length, number of root, dry weight) in sand for media. In order to produce healthy seedlings, each different medium was compounded with TKS-2 (this is a gardening bed soil.) in the ratio 1:1 (v/v.), and compared two conditions. Quality of seedling was better than not mixed TKS-2 into each medium. Transplanting seedlings from greenhouse to nursery grew up rapidly 2 months later (early in August~early in October). Growth amount during two months corresponded to 85.6% and 71.3% in total growth amount of height and diameter at root collar, respectively. In the case of the competition-density effect on yellow-poplar seedlings, direct seedling produced the maximum 35 standard seedlings above 8 mm of root collar diameter per $m^2$, while transplanting seedling produced the maximum 64 standard seedlings per $m^2$. And produced seedlings of two way were significantly different rootlet while axial root and lateral root was not significantly different.

• Journal of Mushroom
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• v.6 no.2
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• pp.47-51
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• 2008

The Oyster mushroom is saprophytic fungus. The pileus is stemmed at the side and later depressed. It grows to 5-15 cm, and is of grey, grey-lilac, blackish-grey, steel grey, grey-brown, and blue-blackish. Various kinds of Oyster mushrooms such as golden, pink, brown, grey, white, and blue make marketing an interesting challenge depending upon the market niche. A new commercial strain "Chung" of oyster mushroom was developed by hyphal anastomosis. It was improved with hybridization between monokaryotic strain derived from Pleurotus ostreatus ASI 2194 and ASI 2487. The pileus of parental strain ASI 2194 and ASI 2487 was grey and light blue-grey, respectively. Most of intra-specific hybrids between strain ASI 2194 and ASI 2487 were showed similar pileus color of parents. By the way, the pileus color of variety 'Chung' was blue to bluish grey. The optimum temperatures of mycelial growth and fruiting body development was $25{\sim}30^{\circ}C$ and $12{\sim}16^{\circ}C$, respectively.

• Journal of Nutrition and Health
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• v.35 no.4
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• pp.480-488
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• 2002

This study was performed to document the association between obesity, a major risk factor for chronic diseases, and dietary pattern in Korean elderly. The subjects were 595 men and women aged 60-89 years. The subjects were classified into 4 groups based on BMI: under weight, BMI < 18.5, normal weight, 18.5 $\leq$ BMI 22.9; overweight, 23.0 BMI 24.9; and obese BMI $\geq$ 25.0. Dietary intakes by 24-hr recall, blood pressure, anthropometric parameters and health eating index (HEI) were measured. Underweight group was excluded for data analysis doe to small number of subjects, and age-adjusted measurements were compared among normal, overweight and obese groups. The mean anthropometric values for males and females were 23.7 and 24.8 kg/$m^2$ for BMI, 0.90 and 0.86 for WHR and 140.7 and 138.8 mmHg for SBP, respectively. The mean intakes of energy, Ca, vitamin A, vitamin B$_2$, and vitamin E did not meet Korean RDA for elderly. Intakes of fat and cholesterol were low: the percent energy from fat for male and female subjects were 19.1% and 18.1% and mean cholesterol intakes were 208 mg and 152 mg, respectively. Judging by HEI score, dietary quality was better in females than in male subjects. The mean BMI of normal, over and obese groups were 21.4, 23.9, 26.7 kg/$m^2$ in male subjects and 21.6, 23.9, 27.1 kg/$m^2$ in female subjects. WHR, SBP and TSF were increased with increasing BMI No association was found between BMI and nutrient intakes and/or food consumption pattern. However, a tendency was shown that the overweight group reported higher intakes in most nutrients compared to normal and obese groups. This study implies that with increasing BMI, anthropometric risk factors, such as WHR, TSF, and blood pressure were Increased, however, no significant differences were found in nutrient intakes and food patterns. Energy and fat intakes do not seem to be a cause for obesity in Korean elderly.