Change of the Dentin Surface after the Intake of the Fluoridated Milks to Rat

Park, Jin-Young 대한임상예방치과학회 2011 International Journal of Clinical Preventive Denti Vol.7 No.1

Objective: The purpose of the study was to confirm anticavity effects of fluoridated milk. Methods: For this test, 3 type fluoridated milks, that is to say control group (0 ppmF), test group 1 (1.25 ppmF) and test group 2 (2.5 ppmF) were made respectively and consumed by 3 rats group (each was consisted of 11 rats) for 4 weeks. After intake of fluoridated milks, on extracting incisor of all specimens for each group and were embeded with the resin and grinded finely. The surface micro-hardness test and SEM checking difference among groups observed. Results: Dentin micro hardness of test group 1 compared with control group increased by 42.3% (p<0.05). Dentin micro hardness of test group 2 compared with control group increased by 60.4% (p<0.05). Dentin micro hardness increment of test group 2 compared with dentin micro hardness increment of test group 1 was high by 18.1% (p<0.05). The results of observation by SEM (×5,000, ×7,000) show that the higher the fluoride concentration in the sequence of control group, test group 1, test group 2, the smoother surface. Conclusion: Above results show that caries reducing effect tends to increase with fluoride concentration in milk consumption.

The Roughness & Micro-hardness on the Deciduous Teeth according to Formula Milk or Human Milk

이미라,이충재,박지현 대한예방치과학회 2011 International Journal of Clinical Preventive Denti Vol.7 No.4

Objective: The objective of this study is to compare the eroding phenomena on enamel, according to feeding types; human milk and formula milk were prepared to check pH in specific durations of time. Methods: 4 groups of solution with control in saline, saliva, formula milk and human milk were prepared and put into 84 specimens from 21 extracted deciduous teeth, and subsequently, incubated at 37℃ for several days. Micro-hardness and SEM observation were conducted on each sample and the results were compared. Results: pH was measured as 6.66±0.01 in formula milk and 7.41±0.07 in human milk, 7.65±0.06 in saliva, respectively. It was revealed through the decrease of the passage of time in experimental groups, otherwise remaining at a similar level in the saliva group. Micro-hardness was the least in the sample of the formula milk group and next in the human milk group. It was revealed to be lower in micro-hardness, both in the human and formula milk group than in the control as in the saliva or water (p<0.01). The surface roughness and the loss of the in-organic substance was revealed more in the formula milk group than in human milk by SEM observation. Conclusion: It was recommended to use human milk feeding because of the more influence in demineralization in formula milk feeding than in human milk, and that oral hygiene care is needed after formula milk feeding as well as in human milk feeding. Objective: The objective of this study is to compare the eroding phenomena on enamel, according to feeding types; human milk and formula milk were prepared to check pH in specific durations of time. Methods: 4 groups of solution with control in saline, saliva, formula milk and human milk were prepared and put into 84 specimens from 21 extracted deciduous teeth, and subsequently, incubated at 37℃ for several days. Micro-hardness and SEM observation were conducted on each sample and the results were compared. Results: pH was measured as 6.66±0.01 in formula milk and 7.41±0.07 in human milk, 7.65±0.06 in saliva, respectively. It was revealed through the decrease of the passage of time in experimental groups, otherwise remaining at a similar level in the saliva group. Micro-hardness was the least in the sample of the formula milk group and next in the human milk group. It was revealed to be lower in micro-hardness, both in the human and formula milk group than in the control as in the saliva or water (p<0.01). The surface roughness and the loss of the in-organic substance was revealed more in the formula milk group than in human milk by SEM observation. Conclusion: It was recommended to use human milk feeding because of the more influence in demineralization in formula milk feeding than in human milk, and that oral hygiene care is needed after formula milk feeding as well as in human milk feeding.

몬테카를로 시물레이션에 의한 미소 비커스 경도의 Weibull 통계 해석에 관하여

김선진(S. J. Kim),공유식(Y. S. Kong),이상열(S. Y. Lee) 한국동력기계공학회 2008 한국동력기계공학회 학술대회 논문집 Vol.2008 No.11

In the present study, the Weibull statistical analysis using the Monte-Carlo simulation has been performed to investigate the micro-Virkers hardness measurement reliability considering the variability. Experimental indentation test were performed with a micro-Virkers hardness tester for as-received and quenching and tempering specimens in SCM440 steels. The distribution of micro-Virkers hardness is found to be 2-parameter Weibull distribution function. The mean values and coefficients of variation (COV) for both data set are compared with results based on Weibull statistical analysis. Finally, Monte-Carlo simulation was performed in order to evaluate the effect of sample size on the micro-Virkers hardness measurement reliability. For the parent distribution with shape parameter 30.0 and scale parameter 200.0 (COV=0.040), the number of sample data required to obtain the true Weibull parameters was founded by 20. For the parent distribution with shape parameter 10.0 and scale parameter 200.0 (COV=0.1240), the number of sample data required to obtain the true Weibull parameters was founded by 30.

The Micro-hardness Changes by Use of Fluoride Dental Floss Silk

윤성혁,조자원,이규환 대한예방치과학회 2013 International Journal of Clinical Preventive Denti Vol.9 No.2

Objective: In recent years, dental floss silk coated with Sodium Fluoride was developed and produced. The purpose of this study was to compare the micro-hardness on the enamel, dentin and cementum at proximal site through the measure of Vickers micro hardness tester. Methods: Eight extracted teeth were used after sectioned longitudinally 7 teeth as 84 samples separating from enamel, dentin and cementum at each tooth in 42 experimental and the same numbers of the control group were used for micro-hardness test, and 1 teeth were used for Stereo microscope observations. Results: The dental floss silk was applied as fluoride contained in experimental group, and non fluoride in control group, for 5,000 times, by use of automatic flossing machine with 150 g weight for all samples as enamel, dentin and cementum, both in experimental and the control, with water spray. Every 100 times movements and 5 % of Acetic acid were applied for 2 hours for all samples. Micro-hardness was measured with 500 g weight for 15 seconds press and VHN was calculated and Stereo microscope was used for observation of the surface roughness and compared. Conclusion: The micro-hardness was higher in experimental group than in control, (p<0.05, by paired t-test) and the surface roughness were more in control groups at enamel, dentin and cementum, than in experimental group, in stereo-microscopic observations. So, it was estimated that, to use the fluoride contained floss silk might be effective for proximal caries prevention in clinical.

Dentinal Micro-hardness and Enamel Surface Change in Deciduous Teeth by Intake Some Candies Containing Vitamins

Seung-hui Choi,Cheon-hee Lee,Sun-ha Ahn 대한예방치과학회 2012 International Journal of Clinical Preventive Denti Vol.8 No.1

Objective: The purpose of the study was to compare the effect on the decalcification of deciduous teeth for several candies containing vitamins as an ingredient. Methods: Twenty-two extracted deciduous teeth were collected and divided, with 8 enamel specimens and 80 dentine specimens. Three kinds of vitamin candies -V food, Vitamin 1000 and PungPung- were prepared for affected solutions, after measuring pH for each solution, Micro-hardness was measured for 80 of the dentinal specimens, and divided by the kinds of solutions and the applied frequency: ten, thirty, and sixty applications. SEM observation was done for 8 enamel specimens divided for the same method. Results: 1. PH was measured as 6.36 in water as control, 5.63 in V food, 2.62 in Vitamin C 1000 and 3.40 in PungPung-i. 2. Micro-hardness value was revealed as the highest in control group, followed by V food group, PungPung-I, and Vitamin C 1000 in sequence (p<0.05). 3. The results of observation by SEM (×3,000) show that smooth and fine surfaces were seen in control enamel surfaces and in the V food specimens. 4. Micro-hardness value was revealed that for more frequent application into the candy solution, less micro-hardness was observed (p<0.05). 5. The results of observation by SEM (×3,000) show that rough and decalcified phenomena were seen in the Vitamin C 1000 and PungPung-i specimens, and the roughness was more severe with increasing frequency of applying the candy solution. Conclusion: The above results show that V food is recommended for intake for children because of the safe level of pH at 5.6 and Vitamin C component, and intake of low pH Vitamin candy for long or frequent uses should be limited because of the risk for decalcification of deciduous teeth.

The Micro-hardness Changes by Use of Fluoride Dental Floss Silk

Sung-Hyuk Yoon,Kyu-Hwan Lee,Ja-Won Cho 대한예방치과학회 2013 International Journal of Clinical Preventive Denti Vol.9 No.2

Objective: In recent years, dental floss silk coated with Sodium Fluoride was developed and produced. The purpose of this study was to compare the micro-hardness on the enamel, dentin and cementum at proximal site through the measure of Vickers micro hardness tester. Methods: Eight extracted teeth were used after sectioned longitudinally 7 teeth as 84 samples separating from enamel, dentin and cementum at each tooth in 42 experimental and the same numbers of the control group were used for micro-hardness test, and 1 teeth were used for Stereo microscope observations. Results: The dental floss silk was applied as fluoride contained in experimental group, and non fluoride in control group, for 5,000 times, by use of automatic flossing machine with 150 g weight for all samples as enamel, dentin and cementum, both in experimental and the control, with water spray. Every 100 times movements and 5 % of Acetic acid were applied for 2 hours for all samples. Micro-hardness was measured with 500 g weight for 15 seconds press and VHN was calculated and Stereo microscope was used for observation of the surface roughness and compared. Conclusion: The micro-hardness was higher in experimental group than in control, (p<0.05, by paired t-test) and the surface roughness were more in control groups at enamel, dentin and cementum, than in experimental group, in stereo-microscopic observations. So, it was estimated that, to use the fluoride contained floss silk might be effective for proximal caries prevention in clinical.

동적 초미소 경도법에 의한 심도별 대전화강암 내 광물들의 역학적 특성

최정해(Junghae Choi),신주호(Juho Shin),장형두(Hyongdoo Jang),강성승(Seong-Seung Kang) 한국암반공학회 2017 터널과지하공간 Vol.27 No.3

동적 초미소 경도법의 압입시험, 하중-비하중 시험, 그리고 반복시험을 이용하여 심도별 대전화강암 내 광물들의 경도와 역학적 특성을 살펴보았다. 시험 결과 세 개 구간(Group-1, -2, -3)으로 광물 집단의 분류가 가능하였다. Martens 경도값은 세 가지 시험법 모두에서 41 m와 223 m 심도에 따른 차이가 크지 않았다. 그럼에도 불구하고, 그 크기는 반복시험<하중-비하중 시험<압입시험 순으로 나타났다. 광물 집단별 평균 Martens 경도, 탄성계수, indentation work 등을 고려해 볼때, 그들의 경계는 비교적 뚜렷하게 나타났다. 결론적으로 동적 초미소경도법의 세 가지 형태 시험법을 이용함으로써 광물들에 대한 비교적 정확한 경도값을 얻을 수 있었다. 또한 하중-비하중 시험과 반복시험으로부터는 광물들의 탄성계수와 광물들의 탄성적-소성적 성질 특성 파악도 가능하였다. The hardness and mechanical properties of the minerals in the Daejeon granite according to depths were investigated by indentation test, load-unload test, and cycle test of dynamic ultra-micro hardness. As a result of the tests, it was possible to classify into three mineral groups (Group-1, -2, -3). The Martens hardness was not significantly different between 41 m and 223 m depths in three mode tests. Nevertheless, they showed in the order of a cycle test<load-unload test <indentation test. Considering the average Martens hardness, elastic modulus, and indentation work for each mineral group, their boundaries were relatively clear. In conclusion, A relatively accurate hardness of minerals can be obtained by three mode tests of dynamic ultra-micro hardness. In addtion, it was possible to characterize the elastic modulus and the elastic-plastic properties of the minerals from the load-unload and cycle tests.

Machining characteristics of micro lens mold in laser-assisted micro-turning

김종수,강봉철 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.4

Laser-assisted machining (LAM) is a type of hybrid material removal process, which is used for locally and instantaneously decreasing the hardness of materials, such as ceramics and hard composites, by irradiating the material with a focused laser during mechanical cutting. LAM, which has been studied primarily for the macro-machining of the hard materials, was applied to the micro-turning process of high hardness steel for a micro-lens mold in this research. The laser-assisted micro-turning (LAμT) process was analyzed using finite element modeling to predict the thermal effects and temperature distributions induced by irradiation of a focused laser and to determine critical cutting parameters, such as spot size, heading distance, and feeds. The effects of the LAμT were verified by an in-situ comparison with conventional micro-turning method, and the cutting conditions were optimized to maximize the cutting performances in terms of cutting force, surface finish, and chip exhaust. Consequently, a lower cutting force and better surface finish was demonstrated compared to the conventional method for the optimized LAμT condition. Therefore, this study showed that the LAμT can be successfully applied to the micro-machining of hard molds.

Change of the Dentin Surface after the Intake of the Fluoridated Milks to Rat

Jinyoung Park,Yeon Soo Jang 대한임상예방치과학회 2011 International Journal of Clinical Preventive Denti Vol.7 No.2

Objective: The purpose of the study was to confirm anticavity effects of fluoridated milk. Methods: For this test, 3 type fluoridated milks, that is to say control group (0 ppmF), test group 1 (1.25 ppmF) and test group 2 (2.5 ppmF) were made respectively and consumed by 3 rats group (each was consisted of 11 rats) for 4 weeks. After intake of fluoridated milks, on extracting incisor of all specimens for each group and were embeded with the resin and grinded finely. The surface micro-hardness test and SEM checking difference among groups observed. Results: Dentin micro hardness of test group 1 compared with control group increased by 42.3% (p<0.05). Dentin micro hardness of test group 2 compared with control group increased by 60.4% (p<0.05). Dentin micro hardness increment of test group 2 compared with dentin micro hardness increment of test group 1 was high by 18.1% (p<0.05). The results of observation by SEM (×5,000, ×7,000) show that the higher the fluoride concentration in the sequence of control group, test group 1, test group 2, the smoother surface. Conclusion: Above results show that caries reducing effect tends to increase with fluoride concentration in milk consumption.

중합방법이 이중중합 레진시멘트의 미세경도에 미치는 영향

이기덕,박세희,김진우,조경모 大韓齒科保存學會 2011 Restorative Dentistry & Endodontics Vol.36 No.2

Objectives: The purpose of this study was to evaluate curing degree of three dual-cure resin cements with the elapsed time in self-cure and dual-cure mode by means of the repeated measure of micro-hardness. Materials and Methods: Two dual-cure self-adhesive resin cements studied were Maxcem Elite (Kerr), Rely-X Unicem (3M ESPE) and one conventional dual-cure resin cement was Rely-X ARC resin cement (3M ESPE). Twenty specimens for each cements were made in Teflon mould and divided equally by self-cure and dual-cure mode and left in dark, , 100% relative humidity conditional-micro-hardness was measured at 10 min, 30 min, 1 hr, 3 hr, 6 hr, 12 hr and 24 hr after baseline. The results of micro-hardness value were statistically analyzed using independent samples t-test and one-way ANOVA with multiple comparisons using Scheffe's test. Results: The micro-hardness values were increased with time in every test groups. Dual-cure mode obtained higher micro-hardness value than self-cure mode except after one hour of Maxcem. Self-cured Rely-X Unicem showed lowest value and dual-cured Rely-X Unicem showed highest value in every measuring time. Conclusions: Sufficient light curing to dual-cure resin cements should provided for achieve maximum curing. 연구목적: 본 연구는 3종의 이중중합 레진시멘트에서 자가중합법과 이중중합법이 중합도에 미치는 영향을 간접적으로 알아보고자 시간경과에 따라 미세경도를 측정하였다. 연구 재료 및 방법: 실험을 위해 자가접착 레진시멘트인 Maxcem Elite (Kerr)와 Rely-X Unicem (3M ESPE) 및 전통형 레진시멘트인 Rely-X ARC (3M ESPE)를 사용하였으며 각 레진시멘트를 동일한 크기의 테플론 몰드에 채우고 자가중합법과 이중중합법으로 중합을 하여 각각 10개씩 시편을 제작하였으며 중합 시작 후 10분, 30분, 1시간, 3시간, 6시간, 12시간, 24시간이 지난 시점에 미세경도를 측정하였다. 결과: 각 시점에서 레진시멘트별로 중합법 사이의 비교를 위한 independent samples t-test 및 모든 실험군 사이의 비교를 위한 one-way ANOVA와 Scheffe 사후검정을 95% 유의수준에서 실시하여 다음과 같은 결과를 얻었다. 1. 모든 실험군에서 시간이 경과함에 따라 미세경도가 증가하는 경향을 보였다. 2. Maxcem에서 중합 1시간 후 부터를 제외하고 이중중합이 자가중합에 비해 높은 미세경도 값을 보였다(p<0.05). 3. 매 시점에서 자가중합법의 Rely-X Unicem이 가장 낮은 미세경도를 보였으며 이중중합법의 Rely-X Unicem이 가장 높은 미세경도 값을 보였다. 결론: 이상의 실험 결과로 볼 때 이중중합 레진시멘트의 충분한 중합을 위해서는 광조사를 반드시 하여야 할 것으로 생각한다.