• Journal of Dental Rehabilitation and Applied Science
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• v.36 no.3
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• pp.158-167
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• 2020

Purpose: The purpose of this study was to study the effects of the utilization of ethanol solution in infection control of dental implant hand drivers, a common practice in dental prosthodontic clinics. Materials and Methods: Infection control methods were divided into two groups. One swabbed with 83% ethanol gauze and the other immersed in 83% ethanol solution for 30, 60, 90, 120, 150, 180 and 300 second intervals after inoculation of the dental implant hand drivers with Staphylococcus aureus. After measuring the number of colony forming units and analyzing the optical density, the effects of infection control in the experimental group were compared with the positive control group without infection control after inoculation with bacteria and the negative control group without inoculation with bacteria after sterilization. Results: The number of colony forming units and optical density analysis showed a statistically significant difference compared to the positive control. On the other hand, there was no statistically significant difference between the negative control and the group immersed in the 83% ethanol solution for more than 150 seconds. Conclusion: It is recommended to use the ethanol solution as a pre-cleaning process before sterilization, since the intermediate-level disinfection method using ethanol solution alone for the infection control of the dental implant hand driver cannot clinically secure the sterility.

• Journal of Chest Surgery
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• v.31 no.5
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• pp.451-455
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• 1998

Bovine pericardial bioprosthesis treated with glutaraldehyde is one of the most popular prosthetic materials, but late calcific degeneration must be solved. According to the alleged hypothesis of this calcification mechanism the free aldehyde groups on the surface of the tissue treated with glutaraldehyde bind to the circulating free calcium and induce mineralization. For mitigating the calcific degeneration, I added MgCl2 into the 0.625% glutaraldehyde solution to compete with calcium for binding to free aldehyde from the glutaraldehyde. I prepared 60 pieces of square shaped bovine pericardia and fixed in the 0.625% glutaraldehyde solution as control group(group 1), and the other 60 pieces in the same glutaraldehyde solution with 4g/L MgCl2 6H2O as the other group(group 2). After fixation for 1 month these were implanted into the bellies of 60 Sprague-Dawley rats subdermally and extracted on 1 month, 2 months, 3 months and 6 months later. With atomic absorption spectophotometry I measured the deposited calcium amount with the following results; 1 month and 2 months after implantation I could not find any differences between two groups, but in the 3rd month calcium was 1.738 mg/g in group 1 and 0.786 mg/g in group 2 and in the 6th month calcium had risen to 3.102 mg/g in group 1 and 1.623 mg/g in group 2, which has statistical significance(p<0.05). This means magnesium shows meaningful calcium mitigation effects on subcutaneously implanted bovine pericardium in the rat models.

• Restorative Dentistry and Endodontics
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• v.35 no.6
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• pp.429-435
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• 2010

Objectives: The aim of this study was to investigate average working lengths of Korean posterior teeth and evaluate validity of endodontic file length. Materials and Methods: The endodontic working length of the posterior teeth of 670 Korean patients were measured than each mean value and standard deviation were investigated than the frequency deviation and standard deviation per each length were calculated. Results: Among the canals of premolar, 66.5% of canal length was marked under 20 mm by endodontic working length and 95.4% could be measured under 22 mm and Among the canals of molars, 95.5% of canal length was marked under 20 mm endodontic working length. Conclusions: With the result of measurement of endodontic working length of premolars of Korean, it suggested that 23 mm endodontic file is more proper than the 21 mm and 25 mm file on the market.

• Korean Journal of Dental Materials
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• v.44 no.4
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• pp.311-318
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• 2017

The purpose of this study was to examine the effects of the curing sequence and polymerization temperature on the flexural strength and microhardness of two provisional resins (Bis-acryl resin composite and polymethyl methacrylate (PMMA)). Polymerization was carried out under various conditions, in air at $25^{\circ}C$ (control) and in hot water (40, 50, 60, 70, and $80^{\circ}C$). The flexural strength test was conducted according to ISO-4049. The Knoop hardness was measured. For the Bis-acryl resin, the temperature up to $50^{\circ}C$ did not increase the flexural strength nor the hardness of the bis-acryl resin composite (p>0.05) but higher temperatures increased the strengths. For the PMMA resin, flexural strength increased with temperatures up to $70^{\circ}C$ and then decreased slightly. Bis-acryl resin composite had higher mechanical properties than the PMMA resin. The effect of heat was more pronounced in the bis-acryl resin composite than in the PMMA resin (p<0.05).

• The Journal of Advanced Prosthodontics
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• v.11 no.1
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• pp.7-15
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• 2019

PURPOSE. The aim of this study was to identify the effects of three aesthetic restorative materials on the wear between tooth and restoration by a pin-on-disk manner. MATERIALS AND METHODS. Six aesthetic restorative materials were used to prepare disk specimens for wear test, which were Lava Zirconia as zirconia group, Vintage MP and Cerabien ZR as veneering porcelain group, Gradia Direct microhybrid composite containing prepolymerized fillers, Filtek Z250 microhybrid composite containing zirconia glass and colloidal silica particles, and Filtek Z350 nanocomposite as composite resin group. Vertical loss of the worn cusp, change of the surface roughness of the restoration materials, and the surface topography were investigated after wear test under 9.8-N contact load. RESULTS. The porcelain groups (Vintage MP and Cerabien ZR) caused the largest vertical loss of teeth when compared with those of the composite resin and zirconia groups, and Filtek Z250 microhybrid composite results in the second-largest vertical loss of teeth. The surface of Filtek Z350 nanocomposite was deeply worn out, but visible wear on the surface of the zirconia and Gradia Direct microhybrid composite was not observed. When the zirconia surface was roughened by sand-blasting, vertical loss of teeth considerably increased when compared with that in the case of fine polished zirconia. CONCLUSION. It was identified that microhybrid composite resin containing a prepolymerized filler and zirconia with reduced surface roughness by polishing were the most desirable restorative materials among the tested materials to prevent the two-body wear between aesthetic restorative material and tooth.

• Journal of Technologic Dentistry
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• v.41 no.1
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• pp.21-27
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• 2019

Purpose: To evaluate 2D and 3D of occulsal, mesial-occlusal and mesial-occlusal-distal cavity of composite resin inlay. Methods: Abutment tooth 16, 36 of FDI system was selected for the study. Inlay prostheses classified as occlusal cavity (OC group), mesial-occlusal (MOC) and mesial-occlusal-distal cavity (MODC) were prepared using composite resin. Composite resin was injected with composite resin in prepared tooth cavity and then photopolymerized with UV light. Additional thermal polymerization was performed. Marginal gap of composite resin inlays were measured by digital microscope(x160) with silicone replica technique. The data was analyzed from statistical software for Kruskal-Wallis test (${\alpha}=0.05$). 3-dimensional analysis was analyzed through superimposition method. Results: The smallest 2D marginal fit measure of the three groups was $47.0{\pm}21.6{\mu}m$ in the MOC group. The largest 2D marginal was $69.1{\pm}33.8{\mu}m$ in the MODC group. In the trueness of the three groups, the most accurate figure was $14.4{\pm}2.3{\mu}m$ for the MODC group. In Precision, the most accurate figure was $14.5{\pm}4.3{\mu}m$ for the MODC group. Conclusion : In this study, 2D marginal fit of OC, MOC, and MODC cavities fabricated with composite resin was applicable to all clinical applications. In the 3D inner surface accuracy evaluation, the MODC group showed the accuracy results.

• The Journal of Advanced Prosthodontics
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• v.11 no.5
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• pp.239-246
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• 2019

PURPOSE. The purpose of this study was to propose and assess a shade guide for pink gingival aesthetics using a Spanish population sample. MATERIALS AND METHODS. The $L^*$, $C^*$, h, $a^*$ and $b^*$ coordinates of 259 participants were measured using a spectrophotometer in 3 standardized points along the attached gingiva of the maxillary central incisors. A hierarchical clustering analysis was applied to obtain separate solutions regarding the number of shade tabs. For each of the solutions obtained, color differences (${\Delta}E^*$) were calculated using the CIELab and CIEDE2000 formulas, and the proposed shade guide was selected considering (1) the color differences between tabs and (2) the coverage error of each of the solutions. RESULTS. The proposed shade guide consisted of 8 gingival shade tabs and achieved CIELab and CIEDE2000 coverage errors of less than the respective 50:50% acceptability thresholds (${\Delta}E^*=4.6$ units and ${\Delta}E_{00}=4.1$). The coordinates for the various gingival shade tabs were as follows: Tab 1: $L^*43.3$, $a^*21.9$, $b^*12.3$ (1.6); Tab 2: $L^*42.9$, $a^*34.1$, $b^*19.1$; Tab 3: $L^*46.5$, $a^*25.8$, $b^*10.9$; Tab 4: $L^*46.5$, $a^*27.3$, $b^*15.1$; Tab 5: $L^*49.6$, $a^*23.5$, $b^*16.8$; Tab 6: $L^*51.5$, $a^*19.7$, $b^*13.6$; Tab 7: $L^*55.9$, $a^*22.0$, $b^*15.0$; and Tab 8: $L^*56.0$, $a^*19.9$, $b^*18.8$. CONCLUSION. The CIELab and CIEDE2000 coverage errors for the 8 shade tabs of the proposed gingival shade guide were significantly lower than those of other guides. Therefore, despite the limitations of this study, the proposed guide is more appropriate for matching gingival shade in the Spanish general population.

• Journal of Technologic Dentistry
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• v.41 no.2
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• pp.63-69
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• 2019

Purpose: The purpose of this study is to evaluate the effect of CAD/CAM system milling tool wear on the marginal and internal fit of PMMA implant interim prosthesis three-dimensional manner. Methods: A total of 20 crowns were fabricated with CAD/CAM method. Their designs were unified to first molar of the left maxilla. The Customized abutments were prepared and scanned with on optical model scanner. Five crowns were milled by the newly replaced tool (1st milling), and 15 crowns were milled by 2nd, 3rd, 4th milling tool. The marginal and internal fit of 20 interim crowns were measured using the triple-scan protocol. Results: Statistically significant difference was found between the $1^{st}$ milling group ($51.8{\pm}14.6{\mu}m$) and the $3^{rd}$, $4^{th}$ milling group ($128.6{\pm}43.8{\mu}m$, $146.2{\pm}38.1{\mu}m$, respectively) at the distal margins. In the mesial margins, There was a statistically significant difference between the $1^{st}$ milling group ($63.6{\pm}25.9{\mu}m$) and the $3^{rd}$, $4^{th}$ milling group ($137.2{\pm}25.9{\mu}m$, $186.8{\pm}70.6{\mu}m$, respectively). In the distal line angle, significant difference was found between the $1^{st}$, $2^{nd}$, $3^{rd}$ milling groups and the $4^{th}$ milling group. In the mesial axial wall, significant difference was found between the $1^{st}$ milling group ($52.2{\pm}20.3{\mu}m$) and the $3^{rd}$, $4^{th}$ milling groups ($22.8{\pm}8.8{\mu}m$, $7.8{\pm}5.7{\mu}m$). Conclusion: As a result of the experiment, decrease of the marginal and internal fit was statistically significant as the number of machining cycles increased. In order to produce clinically excellent restorations, it is recommandable to consider the condition of the milling tool wear, when designing the restoration with CAD program.

• The Journal of the Korea Contents Association
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• v.19 no.5
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• pp.511-519
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• 2019

The purpose of this study was to investigate the status of infection control in dental office and the degree of infection control practice of dental hygienists. A self-reported questionnaire was answered by 193 dental hygienists working in dental hospitals or dental clinics in Gyeonggi and Incheon areas. The number of bacteria was measured sample of surface dental unit chair shoulder backrests and light handles from 19 dental hospitals and 28 dental clinics. It was responded that impression or occlusion bodies were routinely disinfected in 52.6% of the dental hospitals and dental prosthesis were routinely disinfected in 46.4% in dental clinics. The dental hospital and clinics disinfect the surface each 26.3%, 25% after the patient treatment. The dental hospital and clinic were detected bacteria $5.02^*10\^3CFU/mL$, $1^*10\^4CFU/mL$, from dental unit chair backrest, respectively and $8.32^*10\^3CFU/mL$, $4.26^*10\^4CFU/mL$ from light handles, respectively. At the conclusion of this investigation, it can be kept from infection source in dental office is to make the right selection and use of the personal protective equipments and to improve the practice level by regular and active education. The same infection control practice should be done by institutionalizing and mandating infection control practice.

• The Journal of the Convergence on Culture Technology
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• v.5 no.2
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• pp.123-138
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• 2019

The clinical institution of some dental hygiene students and the degree of practice and performance according to the practice contents are identified, so as to develop clinical practice guidelines and to improve the education of universities and practical institutions. From November 2016 to March 2017, the questionnaire was prepared by self-inclusion after explaining the purpose of research and how to prepare questionnaire to some dental hygiene students. This material has been analyzed using PASW Statistics 18.0. As for the clinical practice content items of basic care and infection control, the frequency of "execution" among practice methods was high, and the distribution rate was high in oral evil face radiation, preventive dentistry, prosthesis, periodontology, orthodontics, and oral internal medicine. The conservation department has conducted various practical methods such as "executing," "observing" and "preparing." Oral surgery showed similar distribution rates, such as "observation," "preparation," and "execution" in the "preparation and cooperation of the feet." In pediatric dentistry, "observation" was the most common practice, and among them, "observation," "preparation," and "execution" were performed in "preparation and cooperation for infantile development." In addition, students with more experience in clinical practice showed statistically significant differences in basic care, oral hygiene, preventative dentistry, conservation, dental dentistry, oral surgery, orthodontics, and oral internal medicine(p<0.05). Most clinical practice shows that it is more observable than performed.It is expected that the goal of clear clinical practice content should be set by grade or number of clinical practice experiences, as well as the practice method that can be performed by the trainees.