• Restorative Dentistry and Endodontics
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• v.37 no.2
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• pp.84-89
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• 2012

Objectives: This study analyzed the difference in color caused by different thickness in enamel layer of composite resins when applied with single and layering placement technique, and evaluated if the results agreed with the shade guide from the manufacturers to verify reliability of the color matching process of the manufacturers. Materials and Methods: For single composite resin samples, 6 mm diameter and 4 mm thickness cylindrical samples were fabricated using Ceram-X mono (DENTSPLY DeTrey) and CIE $L^*a^*b^*$ values were measured with spectrophotometer. Same process was done for layering composite resin samples, making 3 dentinal shade samples, 4 mm thickness, for each shade using Ceram-X duo (DENTSPLY DeTrey) and enamel shade resins were layered in 2 mm thickness and CIE $L^*a^*b^*$ values were measured. These samples were ground to 0.2 mm thickness each time, and CIE $L^*a^*b^*$ values were measured to 1 mm thickness of enamel shade resin. Results: Color difference (${\Delta}E^*$) between single and layering composite resin was 1.37 minimum and 10.53 maximum when layering thicknesses were between 1 mm and 2 mm and 6 out of 10 same shade groups suggested by manufacturer showed remarkable color difference at any thickness (${\Delta}E^*$ > 3.3). Conclusion: When using Ceram-X mono and duo for composite resin restoration, following the manufacturer's instructions for choosing the shade is not appropriate, and more accurate information for Ceram-X duo is needed on the variation and expression of the shades depending on the thickness of the enamel.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.263-272
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• 2021

This study investigated the oral health knowledge and educational needs of adults by life cycle. We aimed to provide basic data for developing oral health education plans for well -aging. The survey was conducted online and through mobiles by Gallup Korea during February 2021. A total of 319 adults over the age of 19 were surveyed. The study aimed at investigating the general characteristics, the quality of life-related to oral health, knowledge of oral health, and the need for well-aging education. The PASW Statistics ver 18.0 statistical program was used for data analysis. The analysis of the data suggests that prevention was the highest priority among all age groups. Furthermore, there was a difference in the perceived educational need among different age groups. The cause of the youth, the treatment of the middle-aged and the elderly were significantly related to oral and systemic disease. The need for education related to oral diseases was ranked in the order of aches, bad breath, periodontal diseases, and tooth discoloration. For information, the subjects reached out to the internet, dental and medical institutions, and public health centers. The teaching methods experienced by those surveyed included lectures combined with experience, videos, and expert lectures. We believe that this study can be used to develop an education plan that reflects the needs of the subjects when conducting life cycle education for well-aging.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.4
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• pp.343-350
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• 2008

Purpose: The purpose of this study was to spectrophotometrically evaluate the shade difference between of maxillary and mandibular anterior teeth in the Korean by the standard of vita classical shade guide using $SpectroShade^{TM}$. Material and methods: In this study, the shades of healthy anterior teeth were examined and analyzed using the digital shade analysis of $SpectroShade^{TM}$. This study examined 80 individuals in their twenties, thirties, fourties, fifities ages and 40 males and 40 females, presenting 12 healthy, unrestored maxillary and mandibular anterior teeth. Tooth brushing and oral prophylaxis were performed prior to evaluation. The $SpectroShade^{TM}$ was used to acquire images of the 12 maxillary and mandibular anterior teeth. These images were analyzed using $SpectroShade^{TM}$ Software, and shade maps of each tooth were acquired. The shade difference of upper and lower, and gender differences and ages difference were investigated and analyzed with CIE $L^{*}a^{*}b^{*}$ color order system. One-Way ANOVA test was used to find out if there were significant differences between groups tested and Sheffe multiple comparison was used to identify where the differences were. Results: 1. Shade differences were significant (P < .05) between maxillary and mandibular central incisor, lateral incisor, canine. 2. No significant differences in shade distribution were seen between lateral incisors and central incisors. 3. Canine's shade difference were more significant than central incisor's and lateral incisors's. 4. No significant differences in shade distribution were seen between genders in maxillary and mandibulr central incisor, lateral incisor, canine. 5. No significant differences in shade distribution were seen in order of years in maxillary and mandibulr central incisor, lateral incisor, canine. Conclusions: The results of this study show that 1. Shade difference was founded in maxillary and mandibular anterior teeth and ${\Delta}E^{*}$ value was more than 2.0. 2. Canine's shade difference were more significant than central incisor's and lateral incisors's and between central incisors and lateral incisors shade differences were no significant. 3. No significant differences in shade distribution were seen between genders in maxillary and mandibular anterior teeth. 4. No significant differences in shade distribution were seen in order of years grade in maxillary and mandibular anterior teeth.

• The Journal of Korean Academy of Prosthodontics
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• v.54 no.3
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• pp.226-233
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• 2016

Purpose: The purpose of this study was to evaluate the adaptation of lithium disilicate crowns fabricated by CAD-CAM (computer aided design-computer aided manufacturing) and heat-press technique to compare two different measurement methods in assessing fit of the ceramic crowns: micro CT and cross-section technique. Materials and methods: A prepared typodont mandibular molar for ceramic crown was duplicated and ten dies were produced by milling the PMMA (polymethylmethacrylate) resin. Ten vinyl polysiloxane impressions were made and stone casts were produced. Five dies were used for IPS e.max Press crowns with heat-press technique. The other five dies were used for IPS e.max CAD crowns with CAD-CAM technique. Ten lithium disilicate crowns were cemented on the resin dies using zinc phosphate cement with finger pressure. The marginal and internal fits in central buccolingual plane were evaluated using a micro CT. Then the specimens were embedded and cross-sectioned and the marginal and internal fits were measured using scanning electronic microscope. The two measurement methods and two manufacturing methods were compared using Mann-Whitney U test (SPSS 22.0). Results: The marginal and internal fit values using micro CT and cross-section technique were similar, showing no significant differences. There were no significant differences in adaptation between lithium disilicate crowns fabricated with CAD-CAM and heat-press technique. Conclusion: Both micro CT and cross-section technique were acceptable methods in the evaluation of marginal and internal fit of lithium disilicate crown. There was no difference in adaptation between lithium disilicate crowns fabricated with CAD-CAM and heat-press technique except occlusal fit.

• Journal of Periodontal and Implant Science
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• v.32 no.2
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• pp.379-388
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• 2002

For the success of dental implant, accurate radiographic evaluation is prerequisite for planning the location of the osseointegrated implants and avoiding injury to vital structures. CT/MPR(computed tomography/multiplanar reformation) shows improved visualization of inferior alveolar canal. In order to obtain cross-sectional images parallel to the teeth, the occlusal plane is used to orientate for the axial plane. If the direction of axial plane is not parallel to the occlusal plane, the reformatted cross-sectional scans will be oblique to the planned fixture direction and will not show the actual dimension of the planned fixture's location. If the available bone height which measured in the cross-sectional view is much greater than the actual available bone height, penetration of canal may occur. The aim of this study is to assess the effect of the axial plane to measurement of available bone height for dental implant in computed tomography of the mandible. 40 patients who had made radiographic stents and had taken CT were selected. The sites that were included in the study were 45 molar regions. In the central panoramic scan, the length from alveolar crest to superior border of inferior alveolar canal(available bone height, ABH) was measured in direction of reformatted cross-sectional plane(uncorrected ABH). Then, length from alveolar crest to superior border of canal was measured in direction of stent(corrected ABH). The angle between uncorrected ABH and corrected ABH was measured. From each ABH, available fixture length was decided by $Br{{\aa}}nemark$ system. The results were following ; the difference between two ABHs was statistically significant in both first and second molar(p< 0.01). The percentage of difference more than 1 mm was 8.7% in first molar and 15.5% in second molar. The percentage of difference more than 2 mm was 2.0% in first molar and 6.6% in second molar. The maximum value of difference was 2.5 mm in first molar and 2.2 mm in second molar. The correlations between difference of 2 ABHs and angle was positive correlations in both first and second molar. The correlation coefficient was 0.534 in first molar and 0.728 in second molar. The second molar has a stronger positive correlation. The percentage of disagreement between 2 fixture lengths from two ABHs was 24.4% in first molar and 28.9% in second molar.

• The Journal of Korean Academy of Prosthodontics
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• v.49 no.3
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• pp.214-221
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• 2011

Purpose: To date most of finite element analysis assumed the presence of 100% contact between bone and implant, which is inconsistent with clinical reality. In human retrieval study bone-implant contact (BIC) ratio ranged from 20 to 80%. The objective of this study was to explore the influence of bone-implant contact pattern on bone of the interface using nonlinear 3-dimensional finite element analysis. Materials and methods: A computer tomography-based finite element models with two types of implant (Mark III Br${\aa}$nemark$^{(R)}$, Inplant$^{(R)}$) which placed in the maxillary 2nd premolar area were constructed. Two different degrees of bone-implant contact ratio (40, 70%) each implant design were simulated. 5 finite element models were constructed each bone-implant contact ratio and implant design, and sum of models was 40. The position of bone-implant contact was determined according to random shuffle method. Elements of bone-implant contact in group W (wholly randomized osseointegration) was randomly selected in terms of total implant length including cortical and cancellous bone, while ones in group S (segmentally randomized osseointegration) was randomly selected each 0.75 mm vertically and horizontally. Results: Maximum von Mises strain between group W and group S was not significantly different regardless of bone-implant contact ratio and implant design (P=.939). Peak von Mises strain of 40% BIC was significantly lower than one of 70% BIC (P=.007). There was no significant difference between Mark III Br${\aa}$nemark$^{(R)}$ and Inplant$^{(R)}$ in 40% BIC, while average of peak von Mises strain for Inplant$^{(R)}$ was significantly lower ($4886{\pm}1034\;{\mu}m/m$) compared with MK III Br${\aa}$nemark$^{(R)}$ ($7134{\pm}1232\;{\mu}m/m$) in BIC 70% (P<.0001). Conclusion: Assuming bone-implant contact in finite element method, whether the contact elements in bone were wholly randomly or segmentally randomly selected using random shuffle method, both methods could be effective to be no significant difference regardless of sample size.

• The Journal of Korean Academy of Prosthodontics
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• v.48 no.4
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• pp.287-293
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• 2010

Purpose: This study evaluated the effect of polishing techniques on surface roughness of polymethyl methacrylate (PMMA), as well as the influence of light-cured surface glaze and subsequent brushing on surface roughness. Materials and methods: A total of 60 PMMA specimens ($10{\times}10{\times}5\;mm$) were made and then divided into 6 groups of 10 each according to the polymerization methods (under pressure or atmosphere) and the surface polishing methods (mechanical or chemical polishing) including 2 control groups. The mechanical polishing was performed with the carbide denture bur, rubber points and then pumice and lathe wheel. The chemical polishing was performed by applying a light-cured surface glaze ($Plaquit^{(R)}$; Dreve-Dentamid GmbH). Accura $2000^{(R)}$, a non-contact, non-destructive, optical 3-dimensional surface analysis system, was used to measure the surface roughness (Ra) and 3-dimensional images were acquired. The surface roughness was again measured after ultrasonic tooth brushing in order to evaluate the influence of brushing on the surface roughness. The statistical analysis was performed with Mann-Whitney test and t-test using a 95% level of confidence. Results: The chemically polished group showed a statistically lower mean surface roughness in comparison to the mechanically polished group (P = .0045) and the specimens polymerized under the atmospheric pressure presented a more significant difference (P = .0138). After brushing, all of the groups, except the mechanically polished group, presented rougher surfaces and showed no statistically significant differences between groups. Conclusion: Although the surface roughness increased after brushing, the chemical polishing technique presented an improved surface condition in comparison to the mechanical polishing technique.

• The korean journal of orthodontics
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• v.32 no.2 s.91
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• pp.129-142
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• 2002

The purpose of this study was to evaluate the effects of caffeine and calcium on the activities of the osteoblastic cell from mouse calvaria. The author cultured osteoblastic cells obtained from the mouse calvaria and were divided into three groups : the caffeine-treated, the calcium-treated and the combine-treated group. In caffeine-treated group, the cell toxicity was measured by MTT assay at 1, 2 and 4 days after treatment of caffeine. In all groups, the densities of the mineralized bone nodules were measured by imaging analyzer after Von Kossa staining. The alkaline phosphotase (ALP) activities were measured at 2, 7, 14, 21 and 28 days and the interleukin-1 ${\beta}$ activities at 48 hours after treatment of caffeine and calcium. The measurements were statistically executed with ANOVA test and the results were as follows. 1. The cellular toxicity of the caffeine increased with the concentration of caffeine during the incubation period. 2. The maximum densities of mineralization were observed at 0.2 mM caffeine-treated group, 1.2 mM calcium-treated group, 0.1 mM caffeine and 1.8 mM calcium-treated group. 3. The activities of ALP were peaked at 14 days at calcium-treated group as no-treated. But, the activities of ALP increased with concentrations of caffeine at caffeine-treated group. At combine-treated group, the act of ALP were peaked at 24 days at 1.2 mM, 1.8 mM calcium-treated group, But decreased at 2.5 mM calcium-treated group. 4. The activites of the IL-1 ${\beta}$ were increased significantly at 0.2 mM caffeine-treated group, 1.8 mM calcium-treated group and 0.1 mM caffeine and 1.8 mM calcium-treated group. But, they were decreased at all groups of high concentration.

• The korean journal of orthodontics
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• v.37 no.2 s.121
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• pp.98-113
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• 2007

Objective: The purpose of this study was to evaluate the displacement pattern and the stress distribution shown on a finite element model 3-D visualization of a dry human skull using CT during the retraction of upper anterior teeth. Methods: Experimental groups were differentiated into 8 groups according to corticotomy, anchorage (buccal: mini implant between the maxillary second premolar and first molar and second premolar reinforced with a mini Implant, palatal: mini implant between the maxillary first molar and second molar and mini implant on the midpalatal suture) and force application point (use of a power arm or not). Results: In cases where anterior teeth were retracted by a conventional T-loop arch wire, the anterior teeth tipped more postero-inferiorly and the posterior teeth moved slightly in a mesial direction. In cases where anterior teeth were retracted with corticotomy, the stress at the anterior bone segment was distributed widely and showed a smaller degree of tipping movement of the anterior teeth, but with a greater amount of displacement. In cases where anterior teeth were retracted from the buccal side with force applied to the mini implant placed between the maxillary second premolar and the first molar to the canine power arm, it showed that a smaller degree of tipping movement was generated than when force was applied to the second premolar reinforced with a mini implant from the canine bracket. In cases where anterior teeth were retracted from the palatal side with force applied to the mini implant on the midpalatal suture, it resulted in a greater degree of tipping movement than when force was applied to the mini implant between the maxillary first and second molars. Conclusion: The results of this study verifies the effects of corticotomies and the effects of controlling orthodontic force vectors during tooth movement.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.1
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• pp.15-24
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• 2003

The purpose of this study is to investigate the sterilization effect of Er:YAG laser against the intraoral acid producing bacterium, S. mutans, by irradiating the culture solution containing S. mutans KCTC 3065 with Er:YAG laser having a $650{\mu}m$ diameter beam through the non-contact method. We obtained the following results after examining the temperature changes of the culture solution, numbers of bacterial colonies, and acid-producing ability and attaching ability on teeth by measuring the amount of extracellular polysaccharide produced by S. mutans. The number of bacterial colony was decreased in $10{\mu}l$ culture solution irradiated with laser in overall compared to the control solution. The number decreased as the irradiation intensity and pulse repetition rate were larger and as the exposure time was increased. However, it did not change significantly in $100{\mu}l$ culture solution compared to the control solution. Although the acid-producing ability of S. mutans was inhibited for a certain duration after laser irradiation in 10r1 bacterial culture solution, it did not change in $100{\mu}m$ solution compared with the control solution. The amount of extracellular polysaccharide synthesized by S. mutans was partially decreased through laser irradiation in $10{\mu}m$ culture solution but did not change in $100{\mu}m$ culture solution. Based on these findings, we concluded that Er:YAG laser has an sterilization effect on S. mutans in which we presume that the mechanism is through the heat effect rather than the mechanical effect from development of ultrasound.