• Tunnel and Underground Space
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• v.23 no.6
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• pp.480-492
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• 2013

After the introduction of geothermal power generation technology based on engineering reservoir creation that can be applied on non-volcanic region, industrial need for studies on the efficient and economic execution of costly deep-depth drilling work becomes manifest increasingly. However, since it is very difficult to predict duration and cost of boring work with acceptable reliability because of many uncertain events during the execution, efficient and organized work management for drilling is not easily achievable. Especially, the round trip that discretely occurs because of the abrasion of bit takes more time as the depth goes deeper and it has a great impact on the work performance. Therefore, a technology that can simulate the occurrence timing and depth of round trip in advance and therefore optimize them is essentially required. This study divided the abrasion state of bit into eight steps for simulation cases and developed a forecast algorithm, i.e., TOSA which can analyze the depth and timing of round trip occurrence. A methodology that can divide a unit section for simulation has been suggested; while the Bourgoyne and Young model has been used for the forecast of drilling rates and bit abrasion extent by section. Lastly, the designed algorithm has been systemized for the convenience of the user.

• Journal of Periodontal and Implant Science
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• v.36 no.3
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• pp.673-682
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• 2006

Recent study shows that implant design has a great impact on initial stability in bone. The ITI $TE^{(R)}$ implant, designed originally for immediate placement has a tapered/ cylindrical form which fits the anatomical shape of the natural alvelous or tooth root. The increased diameter at the collar region coupled with more threads lead to more bone contact and enhanced stability. The aim of this retrospective study is to evaluate the clinical use and the efficacy of recently introduced ITI TE implant with a new macro-design. The following results are compiled from 139 patients who received ITl TE implant surgery at the periodontal department. of Yonsei University Hospital between July 2002 and September 2005. 1. 139 patients received 173 ITl $TE^{(R)}$ implants in their maxilla and mandible (Mx 82, Mn 91). Posterior area accounted for 84% of the whole implant surgery, 2. In the distribution of bone quality, type III(41,0%) was the most, followed by type IV(41,0%) and type II (27.7%). As for the bone quantity, type B(43.9%) was the most, followed by type C(42.2%), type D(12.2%) and type A(1.7%). 3. 125 implants(83.9%) were treated by single crown, which accounted for the majority. 4, The total implant survival rate was 100% after a mean follow-up period of 21.2 months. This preliminary data with ITl $TE^{(R)}$ implant showed excellent survival rate although the majority of implants evaluated in this study were placed in the posterior region of the jaw and compromised sites.

• Journal of Periodontal and Implant Science
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• v.39 no.2
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• pp.111-118
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• 2009

Purpose: The integrity of interproximal hard/soft tissue has been widely accepted as the key determinant for success or degree of root coverage following the connective tissue graft. However, we reason that the gingival biotype of an individual, defined as the distance from the interproximal papilla to gingiva margin, may be the key determinant that influence the extent of root coverage regardless of traditional classification of gingival recession. Hence, the present study was performed with an aim to verify that individual gingival scalloping pattern inherent from biotype influence the level of gingival margin following the connective tissue graft for root coverage. Methods: Test group consisted of 43 single-rooted teeth from 21 patients (5 male and 16 female patients, mean age: 36.6 years) with varying degrees of gingival recession requiring connective tissue graft; 20 teeth of Miller class I and 23 teeth of Miller class III gingival recession, respectively. The control group consisted of contralateral teeth which did not demonstrate apparent gingival recession, and thus not requiring root coverage. For a biotype determination, an imaginary line connecting two adjacent papillae of a test tooth was drawn. The distance from this line to gingival margin at mid-buccal point and this distance (P-M distance) was designated as "gingival biotype" for a given individual. The distance was measured at baseline and 3 to 6 months examinations postoperatively both in test and control groups. The differences in the distance between Miller class I and III were subject to statistical analysis by using Student.s t-test while those between the test and control groups within a given patient were by using paired t-test. Results: The P-M distance at 3 to 6 months postoperatively was not significantly different between Miller class I and Miller class III. It was not significantly different between the test and control group in a given patient, either, both in Miller class I and III. Conclusions: The amount of root coverage following the connective tissue graft was not dependent on Miller's classification, but rather was dependent on P-M distance, strongly implying that the gingival biotype of a given patient may play a critical impact on the level of gingival margin following connective tissue graft.

• Journal of dental hygiene science
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• v.15 no.6
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• pp.775-785
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• 2015

The purpose of this study is to verify factors affecting the use of dental hygiene care products in adults. The study used a nationally representative sample of Koreans (2013 Korea National Health and Nutrition Examination Survey) aged 19 years over (n=4,839). Dependent variable was frequency of tooth brushing per day, use of dental floss, use of interdental brush and use of mouth rinse. Independent variable was sociodemographic factors, health behaviors, perceived health and oral health conditions. The chi-square test and logistic regression analysis were performed to identify the factors affecting the use of dental hygiene care products. All analyses were performed using PASW Statistics version 18.0. Resulting of chi-square test, the use of oral hygiene care products was statistically significant with gender, age, education level, household income, marital status, dental utilization, dental examination. Resulting of logistic regression, in female, the higher the education level was identified as common factors for variables in use of dental hygiene care products. Dental hygienist among dental professionals should play an important role as contributor to the national oral health promotion that recognizes the impact of each factor by refining dental hygiene care products and reflect personal characteristics and preferences through the oral health educational media and program development.

• The Journal of the Korea Contents Association
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• v.12 no.11
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• pp.258-266
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• 2012

This study was conducted to investigate the differences between smokers and non-smokers' oral hygiene and college students' smoking awareness. The survey was carried out based on the 260 college students enrolled in four-year universities located in Kyungbuk, Daegu, Gangwon-do. Collected date used the SPSS 17.0 to perform the frequency and cross-analysis. 1. The daily smoking amounts of less than half pack and the smoking duration of more than 1 year and less than 3 years were to be the highest. The initiation of smoking was triggered by the curiosity and the proximal social environment. The reason of smoking was to relieve stress and habitual smoking respectively. 2. There was a significant difference between smokers and non-smokers' tooth brushing time, regular dentist visit, recent dental admission, the purpose of dental visits, scaling and oral health education. 3. There was a significant difference between smokers and non-smokers' awareness of oral hygiene in the subjective oral hygiene status. 4. There was a significant difference between smokers and non-smokers' awareness towards the impact of second-hand, after meal and one or two cigarette smoking. Based on the above results, smokers lack the awareness of smoking and oral hygiene compared to non-smokers. Therefore, the activation and the development of programs for the smoking and oral hygiene education targeting college students are considered to be necessary.

• Korean Journal of Social Welfare
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• v.69 no.3
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• pp.121-140
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• 2017

The purpose of this study was to use the Korea Health Panel to determine how the mother's characteristic and household characteristic variables were associated with dental clinic use of children in childhood and adolescence. The logistic regression analysis found that mother's education level was statistically significantly positively correlated with underage child's dental clinic use and children in single-parent family were less likely to use a dental clinic than those in two-parent family. As for dental clinic use by diseases, the higher level of mother's education, the more likely to use a dental clinic due to dental caries and children in single-parent family were less likely to use a dental clinic due to dental caries than those in two-parent family. No difference in dental clinic use due to tooth extraction was found by any of mother's characteristics or household characteristics, probably because age has an absolute impact during the period between milk teeth and permanent teeth. Lastly, mother's education level and household income were significantly positively correlated with dental clinic use due to orthodontics. On the basis of these results, it is necessary to develop a customized strategy reflecting children's growth stages and household characteristics in making a plan for promoting oral health of children and adolescents.

• Journal of Korean society of Dental Hygiene
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• v.6 no.4
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• pp.283-294
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• 2006

The purpose of this study was to examine the state of smoking among some college students, the smoking motivation of smoker students, what made them quit smoking and how they got ready for giving up smoking, as smoking had a huge impact on national health and there was a desperate necessity for preventive antismoking education programs to let students keep away from smoking. After a survey was conducted with self-administered questionnaires from October 1 through November 1, 2006, the responses from 400 students were gathered, and 384 answer sheets were analyzed except 16 incomplete ones. The findings of the study were as follows: 1. By gender, 62.4% of the male students and 28.6% of the female students were smokers, and the state of smoking was statistically significantly different according to their gender(p<0.05). 2. The largest number of the male students, which accounted 44.1%, started smoking in their high school days, and 39.5% of the females did that in middle school. As for a daily mean amount of smoking, 41.8% of the male students, the greatest percentage, smoked 10 to 19 cigarettes a day, and one to nine cigarettes were most common among the females, which represented 57.9 %. But the gap between the two was insignificant(p>0.05). As many as 83.6% of the males and 86.8% of the females had ever attempted to quit it. 3. Concerning awareness of antismoking policies, they felt that a raise in cigarette price would lead to less smoking, and that antismoking advertisement or posters through television or newspaper would deliver the same results as well. There was a statistically significant difference among their awareness(p<0.05). 4. Regarding preparation stage for quitting smoking, 31.3% of the male smokers had no intention to give it up, and 23.2% considered it. 36.7%, the largest percentage, got ready to refrain from it. Among the female smokers, 34.2% had no plans to abstain from smoking, and 36.8% took it into consideration. 23.7% got ready to do that. The females who got ready for that were outnumbered the males who did. 5. As to connections between the state of smoking and relevant knowledge, the students didn't have a good knowledge on that, and a statistically significant difference existed between the smokers and nonsmokers in smoking knowledge. 6. As for knowledge about oral diseases, they were highly cognizant of the relationship of smoking to tooth discoloration, nicotine stomatitis and bad breath, but they didn't know well about its relationship to delayed recovery from dental treatment, implant failure and ozena. Their smoking condition made a statistically significant difference to their knowledge(p<0.05). In the future, sustained research efforts should be channeled into determining how much smoking affects health and concerns oral diseases, and antismoking counseling programs should be prepared to bolster people's awareness of oral health.

• Journal of Periodontal and Implant Science
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• v.52 no.4
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• pp.338-350
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• 2022

Purpose: Various studies have investigated 3-dimensional (3D)-printed implants using Ti6Al-4V powder; however, multi-root 3D-printed implants have not been fully investigated. The purpose of this study was to explore the stability of multirooted 3D-printed implants with lattice and solid structures. The secondary outcomes were comparisons between the 2 types of 3D-printed implants in micro-computed tomographic and histological analyses. Methods: Lattice- and solid-type 3D-printed implants for the left and right mandibular third premolars in beagle dogs were fabricated. Four implants in each group were placed immediately following tooth extraction. Implant stability measurement and periapical X-rays were performed every 2 weeks for 12 weeks. Peri-implant bone volume/tissue volume (BV/TV) and bone mineral density (BMD) were measured by micro-computed tomography. Bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO) were measured in histomorphometric analyses. Results: All 4 lattice-type 3D-printed implants survived. Three solid-type 3D-printed implants were removed before the planned sacrifice date due to implant mobility. A slight, gradual increase in implant stability values from implant surgery to 4 weeks after surgery was observed in the lattice-type 3D-printed implants. The marginal bone change of the surviving solid-type 3D-printed implant was approximately 5 mm, whereas the value was approximately 2 mm in the lattice-type 3D-printed implants. BV/TV and BMD in the lattice type 3D-printed implants were similar to those in the surviving solid-type implant. However, BIC and BAFO were lower in the surviving solid-type 3D-printed implant than in the lattice-type 3D-printed implants. Conclusions: Within the limits of this preclinical study, 3D-printed implants of double-rooted teeth showed high primary stability. However, 3D-printed implants with interlocking structures such as lattices might provide high secondary stability and successful osseointegration.

• Journal of Korean society of Dental Hygiene
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• v.22 no.6
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• pp.485-494
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• 2022

Objectives: The COVID-19 outbreak has resulted in changes in the instructional methods used in kindergartens and daycare centers to prevent viral infections. This study aimed to investigate the changes in oral health care for children before and during COVID-19 and the perceptions of kindergarten and daycare center teachers about oral health care. Methods: The study subjects were 189 teachers of kindergartens and daycare centers in charge of children aged 3 to 5. The data for the analysis were collected through an online survey. Frequency analysis and the chi-squared test were used for statistical analysis. Results: Compared to before COVID-19, the frequency of tooth brushing after lunch, the number of oral health education and regular oral examinations, and the rate of childcare teachers' experiences with oral health education had decreased during COVID-19. In addition, educators in kindergarten and daycare centers responded that an oral health officer at a public health center was the most desirable oral health educator. Conclusions: During the COVID-19 pandemic, the oral health care of children in kindergartens and daycare centers has declined. Efforts are needed to restore it by educating people about oral hygiene care and oral health education, both at home and in kindergartens and daycare centers.

• Journal of Dental Rehabilitation and Applied Science
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• v.38 no.1
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• pp.9-17
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• 2022

Purpose: The purpose of this study is to investigate how open contacts impact the natural teeth and dental implant prostheses. Materials and Methods: Following criteria were used to select 20 implant crowns with open proximal contacts as the experimental group (Group A): the restorations were delivered in Chosun University Dental Hospital between 2008 and 2018, the restorations are in the posterior region, opposing teeth are fixed dental prostheses, neighboring teeth are sound natural teeth, the patient had been on the maintenance program for at least 3 years. Another 20 implant crowns with closed proximal contacts were selected as the control group (Group B) using the same criteria. Between the two groups, dental caries and food impaction of the neighboring natural teeth and marginal bone-loss of the implants were compared and evaluated. Results: There was no statistically significant difference between Group A and Group B in the occurrence rates of dental caries, food impaction, and marginal bone-loss. The amount of marginal bone-loss, however, revealed statistically significant differences between the two groups, with Group A showing 0.80 ± 0.39 mm loss and Group B showing 1.1 ± 0.43 mm loss. Conclusion: Implant prostheses with open contacts could be clinically considered in select cases as such restorations revealed no harmful effects on neighboring teeth and implant restorations within the perimeters of this study.