• Restorative Dentistry and Endodontics
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• 제18권1호
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• pp.145-155
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• 1993

The purposes of this study were to compare the bleaching efficacy of sodium perborate when mixed either with Superoxol or distilled water and to evaluate the efficacy of different location of intracoronal base on the presence of apical leakage of tested bleaching agents. Forty eight extracted human permanent incisors were stained via whole blood and canal fillings with conventional gutta percha were performed after routine biomechanical perparations. The experimental intracoronal base was placed either at the cementoenamel junction(group 3, 4) or 2mm below cementoenamel junction(group 1, 2). Walking bleaching was performed by two different combinations of bleaching agents : sodium perborate with distilled water in group 1, 3 and sodium perbrate with Superoxol in group 2, 4. The roots of the teeth were evaluated for the presence of color change to assess the leakage of bleaching agnets and the cervical one-thirds of the crown were evaluated for bleaching effect from the whiteness Indea calculated by spectrophotometer. The results were as follows : 1. At the end of 12 days, all the sample teeth demonstrated the increase of Whiteness Index at cervical 1/3 of crown although there were some minor differences among groups. 2. Regardless of location of the base, sodium perborate with superoxol)group 2, 4) showed better results in bleaching than the sodium perborate with distilled water(group 1, 3). 3. Bleaching agent leaked into the root area when the base was placed 2mm below cementoenamel junction but no leakage was found when the base was placed at the cementoenamel junction.

• Structural Engineering and Mechanics
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• 제85권3호
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• pp.337-351
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• 2023

In this paper, the shear behavior of soft filling in rectangular-hollow concrete specimens was simulated using the 2D particle flow code (PFC2D). The laboratory-measured properties were used to calibrate some PFC2D micro-properties for modeling the behavior of geo-materials. The dimensions of prepared and modeled samples were 100 mm×100 mm. Some disc type narrow bands were removed from the central part of the model and different lengths of bridge areas (i.e., the distance between internal tips of two joints) with lengths of 30 mm, 50 mm, and 70 mm were produced. Then, the middle of the rectangular hollow was filled with cement material. Three filling sizes with dimensions of 5 mm×5 mm, 10 mm×5 mm, and 15 mm×5 mm were provided for different modeled samples. The parallel bond model was used to calibrate and re-produce these modeled specimens. Therefore, totally, 9 different types of samples were designed for the shear tests in PFC2D. The shear load was gradually applied to the model under a constant loading condition of 3 MPa (σc/3). The loading was continued till shear failure occur in the modeled concrete specimens. It has been shown that both tensile and shear cracks may occur in the fillings. The shear cracks mainly initiated from the crack (joint) tips and coalesced with another one. The shear displacements and shear strengths were both increased as the filling dimensions increased (for the case of a bridge area with a particular fixed length).

• Restorative Dentistry and Endodontics
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• 제48권2호
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• pp.15.1-15.7
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• 2023

Objectives: This study evaluated the efficiency of WaveOne Primary files (Dentsply Sirona) for removing root canal fillings with 2 types of movement: reciprocating (RCP) and continuous counterclockwise rotation (CCR). Materials and Methods: Twenty mandibular incisors were prepared with a RCP instrument (25.08) and filled using the Tagger hybrid obturation technique. The teeth were retreated with a WaveOne Primary file and randomly allocated to 2 experimental retreatment groups (n = 10) according to movement type: RCP and CCR. The root canals were emptied of filling material in the first 3 steps of insertion, until reaching the working length. The timing of retreatment and procedure errors were recorded for all samples. The specimens were scanned before and after the retreatment procedure with micro-computed tomography to calculate the percentage and volume (mm³) of the residual filling material. The results were statistically evaluated using paired and independent t-tests, with a significance level set at 5%. Results: No significant difference was found in the timing of filling removal between the groups, with a mean of 322 seconds (RCP) and 327 seconds (CCR) (p < 0.05). There were 6 instrument fractures: 1 in a RCP motion file and 5 in continuous rotation files. The volumes of residual filling material were similar (9.94% for RCP and 15.94% for CCR; p > 0.05). Conclusions: The WaveOne Primary files used in retreatment performed similarly in both RCP and CCR movements. Neither movement type completely removed the obturation material, but the RCP movement provided greater safety.

• Restorative Dentistry and Endodontics
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• 제47권1호
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• pp.2.1-2.11
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• 2022

Objectives: This study investigated the impact of micro-computed tomography (micro-CT)-based voxel size on the analysis of material/dentin interface voids and thickness of different endodontic cements. Materials and Methods: Following root-end resection and apical preparation, maxillary premolars were filled with mineral trioxide aggregate (MTA), Biodentine, and intermediate restorative material (IRM) (n = 24). The samples were scanned using micro-CT (SkyScan 1272; Bruker) and the cement/dentin interface and thickness of materials were evaluated at voxel sizes of 5, 10, and 20 ㎛. Analysis of variance and the Tukey test were conducted, and the degree of agreement between different voxel sizes was evaluated using the Bland and Altman method (p < 0.05). Results: All materials showed an increase in thickness from 5 to 10 and 20 ㎛ (p < 0.05). When evaluating the interface voids, materials were similar at 5 ㎛ (p > 0.05), while at 10 and 20 ㎛ Biodentine showed the lowest percentage of voids (p < 0.05). A decrease in the interface voids was observed for MTA and IRM at 20 ㎛, while Biodentine showed differences among all voxel sizes (p < 0.05). The Bland-Altman plots for comparisons among voxel sizes showed the largest deviations when comparing images between 5 and 20 ㎛. Conclusions: Voxel size had an impact on the micro-CT evaluation of thickness and interface voids of endodontic materials. All cements exhibited an increase in thickness and a decrease in the void percentage as the voxel size increased, especially when evaluating images at 20 ㎛.

• Restorative Dentistry and Endodontics
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• 제48권4호
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• pp.36.1-36.15
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• 2023

Objectives: This study aimed to compare the effectiveness of a single-file reciprocating system (WaveOne Gold, WOG) and a multi-file rotary system (ProTaper Universal Retreatment, PTUR) in removing canal filling from severely curved canals and to evaluate the possible adjunctive effects of XP-Endo Finisher (XPF), the Self-Adjusting File (SAF), and an erbium, chromium: yttrium, scandium, gallium garnet (Er,Cr:YSGG) laser using microcomputed tomography (µCT). Materials and Methods: Sixty-six curved mandibular molars were divided into 2 groups based on the retreatment technique and then into 3 based on the supplementary method. The residual filling volumes and root canals were evaluated with µCT before and after retreatment, and after the supplementary steps. The data were statistically analyzed with the t-test, Mann-Whitney U test, analysis of covariance, and factorial analysis of variance (p < 0.05). Results: PTUR and WOG showed no significant difference in removing filling materials (p > 0.05). The supplementary techniques were significantly more effective than reciprocating or rotary systems only (p < 0.01). The supplementary steps showed no significant differences in canal filling removal effectiveness (p > 0.05), but XPF showed less dentin reduction than the SAF and Er,Cr:YSGG laser (p < 0.01). Conclusions: The supplementary methods significantly decreased the volume of residual filling materials. XPF caused minimal changes in root canal volume and might be preferred for retreatment in curved root canals. Supplementary approaches after retreatment procedures may improve root canal cleanliness.

• Journal of Applied Biological Chemistry
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• 제57권4호
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• pp.307-312
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• 2014

초콜릿에는 항산화 물질인 플라보노이드를 다량 함유하고 있어 심혈관질환을 예방하는 효과를 가지고 있으나 열량이 높고 설탕함량이 높은 초콜릿이 많아 비만이나 당뇨병 환자들에게 초콜릿을 제한할 수밖에 없다. 따라서 본 연구에서는 설탕을 타가토스나 자일로스로 대체하고 커피박을 첨가한 쉘 초콜릿 filling을 제조하여 쉘 초콜릿 filling의 물리적 특성과 대체 감미료가 혈당에 미치는 영향을 조사하여 쉘 초콜릿 filling 내의 설탕 과다 섭취로 인한 문제점을 해결하고자 하였다. 실험 결과로는 초콜릿 filling의 수분 함량은 대조군인 설탕군에 비해 타카토스+커피박 군에서 유의적으로 높은 값을 나타내었다. 퍼짐성도 수분 함량과 유사한 결과를 나타내었다. 초콜릿 filling의 색도는 타카토스를 함유한 군이 다른 군들에 비해 유의적인 차이를 보였는데 명도는 설탕군과 자일로스군보다 유의적으로 낮은 값을 나타내었고, 적색도인 a값과 황색도인 b값은 설탕군에 비해 유의적으로 높은 값을 보였다. 당도는 모든 군에서 약 34-35%를 나타내었나, 당도는 커피박첨가에 관계없이 설탕군이 자일로스나 타가토스군에 비해 유의적으로 낮았다. 관능검사에서 타가토스군이 향, 단맛, 이물질감, 전체적인 기호도 4가지 검사 항목에서 높은 점수를 받았다. 전체적인 기호도는 자일로즈군, 타가토스군의 순으로 높은 점수를 받았다. 마지막으로 젊은 여성을 대상으로 60 g의 쉘초콜렛을 섭취한 후 0, 1, 2시간에 혈당변화를 조사하였을 때 타가토스군과 타가토스+커피박군에서 혈당 증가 폭이 가장 낮게 나왔다. 본 연구 결과 타가토스를 감미료로 사용한 쉘 초콜릿 filling이 수분함량, 퍼짐성, 전체적 기호도 및 혈당변화에서 가장 좋은 값을 나타내었음을 알 수 있었다. 타가토스는 섭취하였을 때 열량과 당지수가 낮으므로, 대체 감미료로 타가토스를 사용해 쉘 초콜릿 filling을 제조하여 쉘 초콜릿으로 제품화 한다면, 비만이나 당뇨병 환자들에게 혈당의 큰 상승 없이 쉘 초콜릿을 섭취할 수 있는 기회를 제공할 수 있을 것으로 기대된다.

• 한국학교보건학회지
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• 제12권1호
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• pp.131-141
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• 1999

The purpose of this study was to serve as a basis for the planning of oral health education and the development of an oral health-promotion program for patients who visited dental clinics by examining how much dental hygienists offered oral health education to adult patients at dental clinics. A parent group was selected, being made up of 1,600 dental hygienists who registered with the Dental Hygienist Association and worked in Seoul. The questionnaire survey was carried out and an ${\chi}^2-test$ was made using the data collected from 218 subjects to determine how their practice of oral health education was different according to certain general characteristics(the sort of organization for which they worked, age, the term of their service, and the mean number of patients per day). As a result, the following findings were obtained: 1. Thees general characteristics made the following differences to the content of oral health, education: The sort of organization for which the subjects worked made a significant difference in the following tooth brushing instruction (p<0.05), the effect of oral prophylaxis or education about aftereffects (p<0.05), the regular examination of prosthesis (p<0.05), smoking-prohibition education (p<0.05), and the prevention poor-quality fillings (p<0.01). The mean number of patients per day made significant differences to the regular examination of prosthesis (p<0.05) and the prevention poor-quality fillings (p<0.01). But no significant disparity was generated by age or the term of service. 2. The general characteristics made the following differences to education about nutrition and diet counseling: The sort of organization for which the subjects worked had a significant effect just on the importance of a balanced menu (p<0.05). Age made significant differences in advice for vitamin, mineral, protein or other nutrients (p<0.01), and the importance of balanced menu (p<0.001). The term of service made significant differences in the importance of balanced menu (p<0.01), and advice for nutrients including vitamin, mineral or protein (p<0.01). 3. The general characteristics made the following differences to the recommendation and use of oral hygiene aids: The sort of oragnization for which they worked made significant differences only to a gingival massager and water pick (p<0.05). No significant difference was produced by age, the term of service or the mean number of patients per day. 4. The use of educational media for oral health was different according to the general characteristics: The use of pamphlets or booklets significantly varied depending on the organization for which they worked and with the mean number of patients per day (p<0.05). The use of slides or slide projectors was significantly affected by age (p<0.05). But no significant disparity was yielded by the term of service. 5. The general characteristics made the following difference as to whether a continued oral management system was carried out or not: The sort of organization for which they worked had very a significant effect on this result (p<0.001), and no significant disparity was made by age, the term of service or the mean number of patients per day. 6. The place where oral health education was giver differed according to the following general characteristics: The sort of organization for which they worked made very a significant difference as to the use of an examination room's dental unit chair or waiting room (p<0.01), and to the use of an oral health education room or reception counter (p<0.001). The term of service had a significant effect on the use of a counseling room (p<0.01). And the mean number of patients per day made significant differences in the use of a dental unit chair or reception counter (p<0.05), and to the use of an oral health education room or waiting room (p<0.01).

• Molecular & Cellular Toxicology
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• 제4권3호
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• pp.235-245
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• 2008

Exposure to mercury was assessed in 125 Korean (Gwangju and Busan) and 373 Chinese primary school students (Xinguang village, Goumen town) using hair mercury analysis from November 2006 to September 2007. The geometric mean concentration of mercury was higher among Korean children with recording 0.73 ${\mu}g$/g, compared to Chinese children of 0.12 ${\mu}g$/g, which indicated statistically difference (P<0.01). The mean concentration of Korean children living near incineration facilities was higher by recording 0.76 ${\mu}g$/g while the average concentration of their counterpart in Korea reached 0.69 ${\mu}g$/g. In case of Chinese children, those who are living near power plants showed higher level with posting 0.16 ${\mu}g$/g while the others recorded 0.10 ${\mu}g$/g (P<0.01). Intake of fish was found to be related to hair mercury level. In case of Korean children, those with high fish intake recorded 0.79 ${\mu}g$/g in terms of the geometric mean concentration while the others with low fish intake posted 0.61 ${\mu}g$/g. Among Chinese children, those who often eat fish recorded 0.13 ${\mu}g$/g compared to the others with low fish intake of 0.11 ${\mu}g$/g. On the other hand, amalgam dental fillings have limited influence on mean hair mercury level. As for vaccination, within a month of vaccination, the geometric mean concentration of Korean children reached 0.76 ${\mu}g$/g, and in case of 15 days after injection, the level was 1.20 ${\mu}g$/g. In China, the level of children at one month after receiving injection stood at 0.15 ${\mu}g$/g while the level within 15 days was 0.13 ${\mu}g$/g. Multiple regression analysis showed that BMI, passive smoking, and fish consumption are closely related to hair mercury level among the Korean subjects. In China, hair mercury level was affected by age, location, passive smoking, fish consumption, and vaccination. Explanatory power was 21.6% with $R^2$=0.216.

• 한국산학기술학회논문지
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• 제11권4호
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• pp.1483-1491
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• 2010

이 연구의 목적은 현재 한국 혼합치열기 어린이의 치아우식 충전 및 예방재료의 사용 실태를 파악하고자 하는 것이다. 한국의 4개 대도시 지역 7개 초등학교를 무작위로 선정하여 부모의 동의를 얻은 9세와 10세 어린이 711명을 대상으로 한 명의 검진자가 구강검진을 시행하였다. 연구 결과 우식경험유치면수는 $7.9{\pm}8.0$ ($ds=1.3{\pm}2.5,\;fs=6.6{\pm}7.6$)이고 우식경험영구치면수는 $1.4{\pm}2.2\;(DS=0.2{\pm}0.8,\;FS=1.1{\pm}2.1$)로 나타났다. 아말감, 레진, 실란트, 및 기타재료의 평균 충전 치면수는 각각 $2.8{\pm}3.9,\,1.6{\pm}2.8,\;2.9{\pm}3.2$, 및 $4.5{\pm}7.0$이었다. 지역별 충전 재료의 사용에 있어 아말감의 사용은 대구에서 가장 높았으며 레진은 부산에서 제일 높게 나타났다. 영구치의 치아우식 충전 및 예방 재료의 사용은 치아우식예방을 위한 치면열구전색재의 총 치면수가 전체의 약 70%를 차지하여 가장 많음을 알 수 있었고 충전재료로는 레진이 약 20%, 아말감은 약 10%의 비율을 보였다.

• 한국광물학회지
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• 제18권2호
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• pp.135-144
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• 2005

하부 조선누층군의 풍촌층 고품위 석회석 광체에서는 그 상위의 지층인 화절층으로부터 유래된 극미립의 적갈색 변질물이 열극을 따라 충진 및 피복하는 양상을 보이며 산출된다. 표성기원을 시사하는 산출상태와 광물조성을 이루는 이 침전물은 석회석 광체를 오염시킴으로써, 품위와 품질을 저하시키는 결과를 초래한다. 이 풍화산물은 옥수질 석영, 고령석, 일라이트, 침철석 및 적철석이 주요 자생광물을 이루며 곳에 따라 스멕타이트가 소량 수반된다. 그밖에 원지성 광물편들인 운모와 정장석들이 드물게 상대적으로 큰 입도를 이루며 함유된다. 고령석, 일라이트 및 스멕타이트로 구성되는 이 풍화산물의 다소 복잡한 점토광물상은 석회암 풍화잔류토의 전형에 해당되는 것으로 여겨진다. 이 극미립 풍화물은 곳에 따라 열수에 의해서 재차 변질되어 스틸바이트 같은 열수 기원의 제올라이트 광물을 수반하기도 한다. 이 표성변질물의 생성 및 침투 시기는 풍촌층의 고품위 석회석을 형성시킨 천열수 변질작용의 시기 직후, 즉 쥬라기 초기에 해당되는 것으로 해석된다. 조선 누층군의 응기 및 풍화${\cdot}$ 침식의 시점을 시사하는 이 같은 표성변질 양상은 산소가 풍부한 표층수가 하강하는 환경 하에서 석회질 모암 내에서 화학적 용탈과 확산 방식으로 작용한 것으로 여겨진다.