• Journal of dental hygiene science
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• v.15 no.1
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• pp.54-59
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• 2015

The present study investigated the influences of various abutment teeth shapes (maxillary right canine, pre-molar, molar) on the marginal adaptation of computer aided design/computer aided manufacturing-fabricated zirconia core. In vitro adaptation of zirconia cores manufactured by three different abutments were evaluated. Thirty zirconia cores were made per each models and the adaptation was evaluated through a silicone replica technique. The measurement of the adaptation was carried out using digital microscope. The mean and standard deviation of each reference point were analyzed using the one-way (ANOVA) and Tukey's honestly significant difference tests (${\alpha}=0.05$). The overall marginal fits of the zirconia cores were as follows: canine: $47.59{\mu}m$, pre-molar: $43.74{\mu}m$, molar: $40.36{\mu}m$. They were no statistically significant differences between groups for adaptation (p>0.05). This confirmed that the type of abutment teeth used does not determine the precision of fit of zirconia core.

• Journal of the korean academy of Pediatric Dentistry
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• v.23 no.4
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• pp.788-799
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• 1996

The purpose of this study was to determine the accuracy of the prediction methods which are frequently used in the clinic, such as Moyers', Tanaka and Johnston's, Song's Hixon and Oldfather's, Kaplan's, Smith's. These prediction methods were compared to the data, which were obtained from 100 Kyung-Hee University students (50 males and 50 females) with normal occlusion of permanent dentition, using a retrospective statistical analysis. The standard periapical radiopgraphs for the lower premolars using 16-inch long cone technique and the yellow stone dental casts were taken from each samples. The mesiodistal widths of 4 incisors, canine, premolars were measured on the dental casts, and those of premolars were measured on the radiographs. The correlation coefficients, paired samples t-tests, regression coefficients between the actual measuredments of the samples and the predicted measurements of each methods were analyzed. The results obtained were as follows: 1. The prediction methods using periapical radiographs tended to show a stronger correlation than the methods using dental casts; the correlation coefficients between the actual widths of the lower canine and premolars and the predicted widths of the tested methods were higher in Smith, Kaplan, Hixon & Oldfater, and Tanaka & Johnston (p<0.001). 2. The Moyers' probability chart at 65 % showed a tendency toward the least difference between the actual measurements and the predicted widths of the lower canine and the premolars, and the methods of Smith, Kaplan, Tanaka & Johnston also showed a less difference. 3. By means of evaluation in correlation coefficients and paired smaples t-tests, the Smith and Tanaka & Johnston in male, and the Moyers' 65 % and Song in female showed a high tendency toward accurate methods. 4. The regression equations by models that are derived from the study were as follows: Male(Lt.) :Y=10.799+0.475X Femle(Lt.) :Y= 7.427+0.609X (Rt.) :Y=11.043+0.462X (Rt.) :Y= 8.475+0.556X 5. The regression equations by radiographs that are dericed from the study were as follows: Male(Lt.) :Y=6.5651+0.9720X Femle(Lt.) :Y=4.8656+1.0632X (Rt.) :Y=7.8610+0.9060X (Rt.) :Y=4.5483+1.0843X

• Journal of dental hygiene science
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• v.14 no.3
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• pp.405-410
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• 2014

The purpose of this study in vitro investigation was to compare the marginal and internal fit of Ni-Cr alloy metal ceramic crown before and after porcelain veneering. Furthermore, this study evaluated whether the influence of the porcelain firing on the precision of fit of dental prostheses. The maxillary right incisor was selected as an abutment for experiments. Ten working models were prepared. Ni-Cr alloy cores appropriate for each abutment were prepared by lost wax technique. The marginal area and four internal areas of the crowns were measured at two stages: before veneering process and after upper porcelain firing. Silicone replica techniques were used. The data were statistically analyzed with the paired t-test (${\alpha}=0.05$). $Mean{\pm}SD$ marginal and internal gap were $67.1{\pm}23.3{\mu}m$ for the nickle chrome alloy core group and $74.4{\pm}21.9{\mu}m$ for the metal ceramic crown group. There were statistically significant differences in all investigated areas (p<0.05). Within the limitations of this study, none of the Ni-Cr alloy metal crown values measured after porcelain firing process exceeded $120{\mu}m$, which is the clinically acceptable threshold.

• Journal of Dental Rehabilitation and Applied Science
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• v.34 no.1
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• pp.17-31
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• 2018

Purpose: The purpose of this study was to investigate the accuracy of the interocclusal relationship between upper and lower teeth according to the buccal interocclusal record scan using various intraoral scanner systems. Materials and Methods: The upper and lower full arch Models with normal occlusion were scanned with 5 intraoral scanners (Cerec Omnicam, CS3500, iTero, Trios, True Definition). Buccal interocclusal record scan was taken only at the left side while occlusion was intentionally raised by 1 mm, 2 mm, 3 mm, and 4 mm with metal cylinder core embedded within polyvinylsiloxane bite registration material at the right molar region. The superimposition analysis was done to evaluate overall three-dimensional deviation and cross-section analysis was done to evaluate the degree and the direction of deviation of interocclusal relationship. Results: From the superimposition study, Cerec Omnicam showed the least deviation ($165.5{\mu}m$) and CS3500 ($369.0{\mu}m$) showed the largest (P < 0.01). And the deviation was greater in 3, 4, 2 mm group than 1 mm (P < 0.01). From the cross-section study, Cerec Omnicam showed the farthest deviation ($-242.8{\mu}m$) and CS3500 showed the closest deviation ($312.5{\mu}m$) and a significantly high value was shown in 3 mm group. Conclusion: Every intraoral scanner has different accuracy in reproducing interocclusal relationship.

• Journal of Industrial Convergence
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• v.21 no.3
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• pp.139-148
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• 2023

This study was conducted through Google online survey from November 24 to November 26, 2021 targeting 276 students from the department of dental hygiene at a university in Gangwon-do. The purpose of this study was to investigate the infection awareness of uniforms, recognition of washing rules, and the intention to prevent infectious diseases through individualism and collectivist self-esteem. Statistical methods were analyzed using SPSS Statistics 24.0 and AMOS 21.0 as follows. For analysis, frequency analysis, exploratory factor analysis, confirmatory factor analysis, reliability analysis, structural equation, and ANOVA analysis were performed. As a result, it was confirmed that the models of uniform infection awareness, uniform washing rule recognition(p<.001), self-esteem, individualism, and collectivist intention to prevent infectious diseases were suitable(p<.001). Collectivism was found to affect the perception of uniform infection, the recognition of uniform washing rules, and the intention to prevent infectious diseases, confirming that self-esteem and collectivism had an effect on the change of perception for infection prevention. In the future, it will be possible to use the uniform washing method considering collectivism in infection control education of the dental hygiene.

• The korean journal of orthodontics
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• v.54 no.1
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• pp.48-58
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• 2024

Objective: To quantify the effects of midline-related landmark identification on midline deviation measurements in posteroanterior (PA) cephalograms using a cascaded convolutional neural network (CNN). Methods: A total of 2,903 PA cephalogram images obtained from 9 university hospitals were divided into training, internal validation, and test sets (n = 2,150, 376, and 377). As the gold standard, 2 orthodontic professors marked the bilateral landmarks, including the frontozygomatic suture point and latero-orbitale (LO), and the midline landmarks, including the crista galli, anterior nasal spine (ANS), upper dental midpoint (UDM), lower dental midpoint (LDM), and menton (Me). For the test, Examiner-1 and Examiner-2 (3-year and 1-year orthodontic residents) and the Cascaded-CNN models marked the landmarks. After point-to-point errors of landmark identification, the successful detection rate (SDR) and distance and direction of the midline landmark deviation from the midsagittal line (ANS-mid, UDM-mid, LDM-mid, and Me-mid) were measured, and statistical analysis was performed. Results: The cascaded-CNN algorithm showed a clinically acceptable level of point-to-point error (1.26 mm vs. 1.57 mm in Examiner-1 and 1.75 mm in Examiner-2). The average SDR within the 2 mm range was 83.2%, with high accuracy at the LO (right, 96.9%; left, 97.1%), and UDM (96.9%). The absolute measurement errors were less than 1 mm for ANS-mid, UDM-mid, and LDM-mid compared with the gold standard. Conclusions: The cascaded-CNN model may be considered an effective tool for the auto-identification of midline landmarks and quantification of midline deviation in PA cephalograms of adult patients, regardless of variations in the image acquisition method.

• Journal of Industrial Technology
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• v.36
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• pp.39-43
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• 2016

The purpose of this study is to determine and compare the mechanical and flow properties of polyvinylsiloxane impression pastes. Twelve polyvinylsiloxane impression materials were used. As mechanical properties, tensile strength and tear resistance were measured. Impression materials are subjected to tensile stresses when they are removed from the oral cavity and from stone models and tear resistance is the ability of the material to resist tearing under a tensile stress. Flow is dependent on the ability of the material to resist shear forces. Flow tests were performed to determine the handling characteristics and was measured using a shark fin testing device. An impression material must be able to penetrate the narrow subgingival sulcus and tight interproximal areas. Therefore, it must be able to resist the shear forces as it is pushed between tooth and gingival walls. It is necessary to understand the properties of interocclusal recording materials and is considered that the results obtained in this study will provide guideline information for the manufacturing of impression materials and for selecting appropriate impression materials.

• The korean journal of orthodontics
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• v.48 no.4
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• pp.262-267
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• 2018

The aim of this study was to test the clinical application of an intraoral scanner for serial evaluation of orthodontic tooth movement. The maxillary dentitions of eight patients with fixed orthodontic appliances were scanned using an intraoral scanner at the beginning of treatment (T0), and at 1 month (T1), 2 months (T2), 3 months (T3), and 4 months (T4) after T0. The serial digital models were superimposed on the palatal surface as a reference area, and the linear and angular changes of the central incisors, canines, and first molars were evaluated. The intraclass correlation coefficient and method errors showed that this method was clinically acceptable. Various types of orthodontic tooth movements, including minute movements, could be observed every month. The intraoral scanner and digital superimposition technique enabled the serial evaluation of orthodontic tooth movement without taking serial impressions and/or acquiring radiographs.

• Journal of Oral Medicine and Pain
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• v.8 no.1
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• pp.121-126
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• 1983

This study is conducted with a view to make correct sexual differentiation by the utilization of discriminant functions. For that purpose were randomly sampled out 148 young adults testes, comprising 67 males and 81 females, ranging from 15 through 18 years fo age. Based on the values made available from the measurement of 6 items corresponding to the maxillary cast models, a statistical analysis was made to abstract feasible discriminant functions. The results findings are as follows: 1. The mean value by sex indicates, in all items, higher one in male group than in female group. 2. Through the measurement were defined as singnificant items in sexual differentiation the bucco-lingual dimensions of canine, 1st-molar, 2nd molar, and 1st bimolat width. 3. Derived from the value from measurement items were discriminant functions with the intention of applying them to sexual differentiation, as follows: 1) Y=-25.4112+0.7513BL3+0.3298BL4-0.2854BL5+0.7350BL6-0.3482BL7+0.2893AW (as tested by Method I) 2)Y=-25.0628+0.7737BL3+0.7468BL6-0.3885BL5+0.2951AW(as tested by Method II) BL3 : Bucco-lingual dimension of upper canine BL4 : Bucco-lingual dimension of upper first prmolar BL5 : Bucco-lingual dimension of upper second premolar BL5 : Bucco-lingual dimension of upper first molar BL6 : Bucco-lingual dimension of upper second molar AW : Upper first bimolar width 4. Sexual defferentiation in terms of descriminant functions represented a probility of 74.6%.

• Journal of Preventive Medicine and Public Health
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• v.46 no.5
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• pp.237-248
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• 2013

Objectives: The purpose of this study is to examine and explain the extent of income-related inequity in health care utilization and expenditures to compare the extent in 2005 and 2010 in Korea. Methods: We employed the concentration indices and the horizontal inequity index proposed by Wagstaff and van Doorslaer based on one- and two-part models. This study was conducted using data from the 2005 and 2010 Korean National Health and Nutrition Examination Survey. We examined health care utilization and expenditures for different types of health care providers, including health centers, physician clinics, hospitals, general hospitals, dental care, and licensed traditional medical practitioners. Results: The results show the equitable distribution of overall health care utilization with pro-poor tendencies and modest pro-rich inequity in the amount of medical expenditures in 2010. For the decomposition analysis, non-need variables such as income, education, private insurance, and occupational status have contributed considerably to pro-rich inequality in health care over the period between 2005 and 2010. Conclusions: We found that health care utilization in Korea in 2010 was fairly equitable, but the poor still have some barriers to accessing primary care and continuing to receive medical care.