• The Journal of Korean Academy of Prosthodontics
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• v.49 no.1
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• pp.22-28
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• 2011

Purpose: This article attempted to examine how teeth for restoration is made in a clinical practice and utilize it as future educational material of teeth formation and basic data for additional research. Materials and methods: This experiment investigated the models sent to milling center for production of zirconia crowns. After scanned with Lava CAD/CAM System (3M ESPE, Seefeld, Germany), they are measured on 'ImageJ (version 1.32j, National Institutes of Health, USA)' program and compared and analyzed. Convergence angle from mesio-distal surfaces and bucco-lingual surfaces of each teeth are measured. Also, bucco-lingual diameter of the region lowered as much as 0.4 mm from incisal edge in anterior teeth except canines.(This measure is defined as the Peak 0.4) The analysis of data between each group was conducted by Windows SPSS statistic program, and was proved significant on 95% confidence level by independent t-test, one-way ANOVA and multiple analysis (Sheff${\'{e}}$ test). Results: The mean value of convergence angle was $18.67^{\circ}$ It is ranked as molar ($26.70^{\circ}$) > premolar ($16.87^{\circ}$) > anterior teeth ($14.81^{\circ}$) in the order of mesio-distal convergence angle; anterior teeth ($22.32^{\circ}$) > molar ($20.93^{\circ}$) > premolar ($15.41^{\circ}$) in the order of bucco-lingual convergence angle. The mean value of Peak 0.4 was 1.18 mm. Conclusion: Convergence angle of abutment of zirconia all ceramic crown has difference depending on the location in the arch. Due to the nature of production of zirconia all ceramic crown, convergence angle of abutment and line angle finishing degree can have an effect on internal suitability of restoration.

• Journal of the korean academy of Pediatric Dentistry
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• v.33 no.4
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• pp.717-721
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• 2006

Premature loss of maxillary primary incisors often results from early childhood caries (ECC), trauma. While space maintenance in the posterior region is an important consideration when there is early loss of primary molars, the anterior segment appears to be stable, even with the early loss of several incisors, once the primary canines erupt. However, collapse of anterior arch integrity is evident in cases where incisor teeth are in a crowded dentition prior to extraction or lost before the eruption of the primary canines. So, when early loss of maxillary primary incisors, the aim of restoration is esthetics, speech problem, oral habit such as tongue thrusting than space maintenance. This paper reports that the esthetic problem due to premature loss of maxillary incisors can be successfully resolved by soldered open-faced stainless steel crown.

• Journal of the korean academy of Pediatric Dentistry
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• v.47 no.2
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• pp.140-147
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• 2020

This study analyzed the longevity of preformed metal crowns (PMCs) in first permanent molars and evaluated factors influencing their survival during a long-term follow-up period. In all, 115 first permanent molars treated with PMCs between June 2008 and June 2018 were retrospectively analyzed. The overall combined success rate for the study group was 84.3%. The 5-year survival rate was 82.8%. Multivariate Cox regression analyses identified distal cavities and mandibular PMC placement as risk factors for restoration failure. Careful placement of PMCs at the final try-in stage augments the longevity of the crown.

• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.2
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• pp.135-142
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• 2017

Adoption of CAD/CAM milling in dentistry has allowed production of more analytic and precise prosthesis. Such precision enables definite path of insertion and undercut to be provided in removable partial denture especially when designing a surveyed crown on an abutment tooth. This case is about the production of surveyed crown with proper path of insertion utilizing CAD/CAM electronic surveying method on a patient with edentulous maxilla. Resulting removable partial denture fit well and showed acceptable stability and retention with no clinical problem.

• The Journal of Advanced Prosthodontics
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• v.7 no.1
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• pp.27-31
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• 2015

PURPOSE. The purpose of this report was to evaluate the effect of the fabrication method and material type on the fracture strength of provisional crowns. MATERIALS AND METHODS. A master model with one crown (maxillary left second premolar) was manufactured from Cr-Co alloy. The master model was scanned, and the data set was transferred to a CAD/CAM unit (Yenamak D50, Yenadent Ltd, Istanbul, Turkey) for the Cercon Base group. For the other groups, temporary crowns were produced by direct fabrication methods (Imident, Temdent, Structur Premium, Takilon, Systemp c&b II, and Acrytemp). The specimens were subjected to water storage at $37^{\circ}C$ for 24 hours, and then they were thermocycled (TC, $5000{\times}$, $5-55^{\circ}C$) (n=10). The maximum force at fracture (Fmax) was measured in a universal test machine at 1 mm/min. Data was analyzed by non-parametric statistics (${\alpha}$=.05). RESULTS. Fmax values varied between 711.09-1392.1 N. In the PMMA groups, Takilon showed the lowest values (711.09 N), and Cercon Base showed the highest values (959.59 N). In the composite groups, Structur Premium showed the highest values (1392.1 N), and Acrytemp showed the lowest values (910.05 N). The composite groups showed significantly higher values than the PMMA groups (P=.01). CONCLUSION. Composite-based materials showed significantly higher fracture strengths than PMMA-based materials. The CADCAM technique offers more advantages than the direct technique.

• The Journal of Advanced Prosthodontics
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• v.3 no.2
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• pp.69-75
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• 2011

This study assessed the effect of preparation design on marginal adaptation and also compared the sensitivity and specificity of clinical evaluation techniques for marginal accuracy of cast restorations to stereomicroscopy. MATERIALS AND METHODS. Three Ivorine molar teeth of different designs were prepared. (A)-A complete crown preparation with buccal shoulder and beveled finish line. (B)-A complete crown preparation with chamfer finish line. (C)-A three-quarter crown preparation with proximal boxes and beveled finish line. Twenty four castings were prepared with eight castings for each design respectively. Each casting underwent examination with an explorer, disclosing media, and a stereomicroscope. Stereomicroscopy at a value less than or equal to 30 microns was used as a gold standard to evaluate the significance of different designs on marginal adaptation. Chi-square tests of independence and Kruskal-Wallis were used to evaluate the effect of preparation design and compare the agreement between examination methods for detection of marginal gap size of greater than or equal to 30 microns (${\alpha}$=.05). Sensitivity and specificity for explorer and disclosing media as compared to stereomicroscope was calculated using statistical formula given by Park. RESULTS. The preparation design did not significantly affect overall marginal adaptation. Examination by explorer and disclosing media at $30 \;{mu}m$ revealed 39% and 10.06% sensitivity and 91% and 82% specificity respectively. CONCLUSION. Preparation designs examined in this study did not significantly affect the marginal adaptation of the castings. Commonly used clinical evaluation techniques using explorer and disclosing media appeared to be inadequate for assessment of marginal accuracy.

• Fashion & Textile Research Journal
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• v.3 no.4
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• pp.337-343
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• 2001

This study was purposed to see how men's hair styles of Japan had changed throughout history and results of the study was as follows. There are such evidences as topknots in its primitive styles and wooden combs that several hair styles were tried already in the primitive Jomon Period. In the Yayoi period, bare topknot style without crowns and Mizura style in which hair drop down both ears were popular. In the period of ancient burial mounds, Mizura style was dominative style and varied its form and shape according to classes and status. In the Aska and Nara era, topknot-in-the-crown style in which hair bound in one as in continental style and put in crown or hood, which style was influenced by the Sui and the Tang periods of China. Since the Heian period, topknot-in-the-Ebosi style, binding style, and Karawa style as well as topknot-in-the-crown style came in sight and Sakayaki style became popular in the Kamakura and Muromachi periods. In the Momoyama period, Chasenmage style and Ichomage style were spread widely. In the early Edo era, Wakashumage style and Yaromage style as well as Ichomage style were preferred. In the middle of Edo era in which form and shape of topknot was more distinct symbol of class, status and job than in any other period, Tachmach style under the influence of the Punkin and Honda modes. Sonno style was popular in the late Edo era. There was a drastic disappearance of topknot style by the hair-cutting order during the Meiji Restoration period and civilized hair style of the Jankiri style, a kind of dishevelled hair style without making a topknot was in fashion and continued to the present.

• The Journal of Korean Academy of Prosthodontics
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• v.54 no.1
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• pp.21-27
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• 2016

In removable dental prostheses, it is important to minimize impairment of residual tissue caused by wearing dentures. There are two factors that harm residual tissue. The first is functional load bearing of remaining teeth and alveolar ridges and the second is the effect of poor oral hygiene. Double crown retained removable dental prostheses provide rigid support, and it may reduce impairment caused by load bearing of alveolar ridges. Also, dental plaque and oral deposits, which are attached to outer crowns and dentures, can be easily managed extra-orally. In addition, it is beneficial to the health of the marginal gingiva because inner crowns have easy access for oral hygiene. In this case, double crown retained removable dental prostheses were used for the partially edentulous patient with severe residual alveolar bone resorption and poor oral hygiene, and the result was clinically satisfactory in terms of functional, esthetical, and oral hygiene aspects.

• Journal of dental hygiene science
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• v.22 no.3
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• pp.139-147
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• 2022

Background: Temporary crown resins are used prior to prosthesis placement, indicating the importance of aesthetics. The aim of this study was evaluate the color stability of various staining solutions according to the color of temporary crown resins using VITA Easyshade^Ⓡ V. Methods: The temporary crowns used were the powder-liquid type and included four shades. A total of 36 specimens were fabricated in the form of disks with a diameter of 1.8 mm and a depth of 2 mm. They were divided into four groups of nine each, and staining was performed for seven days by precipitation in 3 mL of three staining solutions composed of distilled water, black coffee, and red wine. Color and color stability evaluations were performed by a trained examiner using a digital spectrophotometer (VITA Easyshade^Ⓡ V). Color stability was analyzed using the ΔE value. Results: Because of the color stability evaluation using the ΔE value, the difference between three and seven days was significant in the specimen I and III groups (p<0.05). Further, post hoc analysis showed that the ΔE value of red wine was significant, indicating that the color stability in red wine was low. The ΔE values in group II between days three and seven were statistically significant (p<0.05). Post hoc analysis showed that distilled water, coffee, and wine had the highest ΔE values on day three. On day seven, the ΔE value for wine was significant, and the color stability was low. There was no significant difference in group IV according to the staining period and staining solution; therefore, color stability was high (p>0.05). Conclusion: This study showed that most temporary resin restorations exhibited color stability in the staining solution. The darker the color of the temporary resin restoration, the higher the color stability against extrinsic staining.

• Journal of Technologic Dentistry
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• v.45 no.3
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• pp.67-73
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• 2023

Purpose: This in vitro study aimed to evaluate the clinical acceptability of precision of fit of the support thickness of Co-Cr alloy copings fabricated using selective laser melting (SLM). Methods: Thirty dental stone models of maxillary left molar abutments were manufactured, images were taken using a scanner, and a computer-aided design program was used to design the form of a conventional metal ceramic crown coping. Overall, 30 single copings were made from Co-Cr alloy using SLM and divided into three support radius groups (0.1, 0.25, and 0.35 mm) of 10 for each. Digitized data were superimposed with three-dimensional inspection software to quantitatively obtain the machinability of a ceramic crown coping, and visual differences were confirmed using a color map. The root mean square values of the ceramic crown coping group were statistically analyzed using one-way analysis of variance (α=0.05). Results: The precision of fit was superior with 0.25 mm compared with 0.1 mm and 0.35 mm, and the results exhibited significant differences (p<0.05). All specimens showed that various support thicknesses did not exceed the clinically permitted value of 120 ㎛, which mean that more than 0.1 mm and 0.35 mm of support radius for SLM was adequate. Conclusion: The support thickness of Co-Cr alloy restoration fabricated using SLM is shown to affect the adaptation.