• Restorative Dentistry and Endodontics
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• v.12 no.2
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• pp.65-72
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• 1987

The purpose of this study was to examine the influence of several root canal sealers on the discoloration of internal surface after root canal obstruction. Twenty four sound human premolars, extracted for orthodontic or prosthodontic purposes, were randomly selected and divided into eight groups. Extracted premolars were prepared, and the following seven materials were introduced into the pulp cavities: AH 26, Fuji ionomer (Type I) cement, N2, Oxypara "Murakami", Kerr sealer, PCA sealer, and G-C's Propac ZOE cement. After 7 weeks of incubation; the discolored tooth crowns were hemisectioned, and the internal staining patterns were examined. Then, with an association of observed values the mean intensity scores and percentage of coverage scores of the internal staining patterns in teeth attained by two observers using for Chisquare test were analyzed. The results were as follows: 1. All the experimental premolar's crown showed various ranged discoloration of internal surface. 2. There was no significance between the association scores of two observers participated into this experiments:% coverage scores (P > 0.05) and intensity (P > 0.05) 3. The crowns filled with PCA sealer, AH 26, and Fuji ionomer cement was visible within a depth of one third of dentin. (P> 0.05) 4. For N2, Kerr sealer, and G-C's Propac cement, A slight dentinal staining was recorded, which penetrated up to half way into the dentin. (P> 0.05) 5. It was noticed that the teeth filled with Oxypara "Murakami" were discolored more than two thirds of the dentinal layer. 6. On the control group, there was no discoloration.

• Journal of the korean academy of Pediatric Dentistry
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• v.44 no.3
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• pp.306-316
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• 2017

The purpose of this study was to evaluate the effects of exposure to various children's drinks on the color stability of anterior primary teeth and different esthetic restorative materials clinically used in pediatric dentistry. Exfoliated maxillary primary central incisors that had been unaffected by caries were chosen as control group. Maxillary primary central incisor-shaped specimens made of strip crown and Nu-smile zirconia crowns were chosen as test groups. Polished strip resin crowns were additionally prepared to compare with unpolished strip resin crown. Each specimen and teeth were divided into 4 groups in which the test samples (n=5 each) were immersed in 4 different drinks (distilled water, cola, grape juice, jelly juice) for 6 days. In all 4 drink groups, all specimens generally showed increasing ${\Delta}E^*$ value (color difference) with time. Polished resin strip crown had higher ${\Delta}E^*$ value than the unpolished in cola, grape juice and jelly juice groups. ${\Delta}E^*$ value of zirconia crown in cola, grape juice and jelly juice groups were significantly different (p < 0.05). In conclusion, dietary control of children's drinks is required for preventing discoloration of restorative materials.

• Journal of Dental Rehabilitation and Applied Science
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• v.29 no.1
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• pp.95-101
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• 2013

Recently, the demand for esthetic improvement by a treatment neither time consuming nor invasive is increasing. The patient wanted the maxillary anterior teeth appearance to be improved by prosthetic treatment, not other treatments such as orthodontic, periodontal, and endodontic treatments, despite the limit of esthetic improvement. In this case, among the recent variety of all ceramic systems for the aesthetic prosthetic restoration, we selected the zirconia-based system as a method of restoration in order to conceal the discoloration of teeth. The patient was satisfied with the esthetic results.

• Restorative Dentistry and Endodontics
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• v.40 no.4
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• pp.322-327
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• 2015

A recent treatment option for non-vital immature teeth in young patients is revascularization with triple antibiotic paste (TAP). However, tooth discoloration was reported with the use of conventional minocycline-containing TAP. In this case report, amoxicillin-containing TAP was used for revascularization of non-vital immature teeth to prevent tooth discoloration. At the 1 yr follow up, the teeth were asymptomatic on clinical examination and showed slight discoloration of the crown due to mineral trioxide aggregate (MTA) filling rather than amoxicillin-containing TAP. Radiographic examination revealed complete resolution of the periapical radiolucency, and closed apex with obvious periodontal ligament space. However, the root growth was limited, and the treatment outcome was more like apexification rather than revascularization. These results may be due to unstable blood clot formation which could not resist the condensation force of MTA filling, whether or not a collagen matrix was in place. These cases showed that although revascularization was not successful, apexification could be expected, resulting in the resolution of the periapical radiolucency and the closure of the apex. Therefore, it is worthwhile attempting revascularization of non-vital immature teeth in young patients.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.4
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• pp.454-464
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• 1999

The metal ceramic crown is currently the most popular complete veneer restoration in dentistry, but in many cases, the metal cervical collar at the facial margin is unesthetic and unacceptable. Facial porcelain margin has been used in place of it. But this dose not solve the problems, such as dark gingival discoloration and cervical opaque reflection of porcelain veneer. Recently, metal copings which were designed to terminate its labio-cervical end on the axial walls coronal to the shoulder have been clinically used to solve the esthetic problem of metal ceramic crown. But in this design, porcelain veneer of labio-cervical area which is not supported by metal may not be able to resist the stress during cementation and mastication. The purpose of this study was to evaluate fracture strength and fractured appearance of crowns according to different coping designs. A resin maxillary left central incisor analogue was prepared for a metal ceramic crown, and metal dies were made with duplication mold. Metal copings were made and assigned to one of four groups based on facial framework designs: group 1, coping with 0.5mm metal collar; group 2, metal extended to the shoulder; group 3, metal extended to 1mm coronal tn the shoulder: group 4, metal extended to 2mm coronal to the shoulder. Copings and crowns were adjusted to be same size and thickness, and cemented to metal dies with zinc phosphate cement by finger pressure. Fracture strength was measured with Instron Universal Testing Machine. Metal dies were anchored in Three-way-vice at 3mm below finish line and at $130^{\circ}$ inclined to the long axis of the crown. Load was directed lingually at 2mm below midincisal edge. Load value at initial crack and at catastrophic fracture was recorded. The results obtained were as follows : 1. Fracture strength values at initial crack were higher in groups 1, 2 than in groups 3, 4 but this difference was not statistically significant(P<0.05). 2. Conventional metal collared crown had greater catastrophic fracture strength than any other collarless crowns. 3. The greater the labial metal coping reduction, the lower the catastrophic fracture strength of crowns but when more than 1mm of labial metal reduction was done, the difference in strengths was not statistically significant(p<0.05). 4. The strongest collarless coping design was group 2.

• Journal of the korean academy of Pediatric Dentistry
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• v.50 no.3
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• pp.277-291
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• 2023

This study aimed to compare the effects of applying different types of dentin bonding agents (DBAs) on tooth and on the sealing ability of CSC in regenerative endodontic procedures (REPs). Specimens were made from 120 human first premolars and categorized into the following groups based on the presence and the type of DBA: Group I, no bonding; Group II, One-Step; Group III, Clearfil SE Bond; and Group IV, Single Bond Universal. Subsequently, the groups were categorized into Subgroup a and Subgroup b, in which Endocem MTA^® Premixed Regular and Biodentine were used, respectively. The CIE L^*a^*b^* on the photos taken prior to TAP placement (S0), 1 week after TAP placement (S1), 2 weeks after TAP placement (S2), 4 weeks after TAP placement (S3) and 2 weeks after CSC placement (S4) was used to assess discoloration. The samples were submerged in a 2% methylene blue solution and magnified by 30 times under a stereomicroscope to assess microleakage. The application of DBA during REP reduced crown discoloration, while Biodentine showed minimal discoloration with or without DBA and regardless of the DBA type. Additionally, the application of DBA did not increase microleakage.

• The International Journal of Costume Culture
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• v.7 no.2
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• pp.151-157
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• 2004

This research is to conservate the old hat and restore its shape and place it on a supportive form in a stable protective container. The hat is a homemade construction, utilizing three different machine made laces, and two cotton net fabrics. The exterior, particularly the top crown piece, as well as the lace along the brim's edge has been generally soiled and discolored. Inside the crown, the cotton net has broken threads, and thread loss in several areas. The paper covering the two wires is very weak, and has discolored the lace in the areas of contact. The plastic buckles of the velvet ribbon have also discolored the areas where there is contact. The wash/bleach bath procedure was very effective. Virtually all of the light brown surface discoloration stains were removed. The darker brown spots, particularly concentrated around the two paper covered wires and assumed to be rust, were $90\%$ removed by the treatment. The brown spots apparently were due to the degradation of the paper covering, and not caused by the wire itself. The buckram foundation lost about $50\%$ of its stiffness, but this was not a major concern due to the fact that this hat should remain it its mount, which has been designed to serve for both storage and exhibition purposes.

• Journal of Technologic Dentistry
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• v.25 no.1
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• pp.9-20
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• 2003

Using a nickel-chrome casting alloy called 'Rexillium V' which is also available as base metal alloy for dental ceramic crown, 4 types of mixtures(A, B, C, D) with old and new metal were prepared for cyclic casting. The results of cyclic casting can be outlined as follows: 1. For Vickers hardness after casting, specimen A and D tended to have lower hardness in the course of cyclic casting, while specimen B and C tended to higher hardness. 2. The results of X-ray diffraction analysis showed that major crystal phase contained nickelchrome compounds and carbide. 3. The observation results of SEM photographs after cyclic casting show that there was a significant tendency to have similar structures among experimental groups. 4. The results of EDX analysis after cyclic casting showed that there were little differences in chemical composition between parent metal and base metal alloy. Although industrial nickel-chrome cast alloy did not show any significant change in material properties even through cyclic casting over several times, it is recommended that more there be more in-depth studies on how to detect any potential corrosion, discoloration and toxication of dental ceramic crown implanted in patient's oral cavity.

• Korean Journal of Remote Sensing
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• v.35 no.4
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• pp.545-560
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• 2019

Unlike other critical forest diseases, pine pitch canker in Korea has shown rather mild symptoms of partial loss of crown foliage and leaf discoloration. This study used high-resolution satellite images to detect and monitor canopy decline by pine pitch canker. To enhance the subtle change of canopy reflectance in pitch canker damaged tree crowns, multi-temporal analysis was applied to two KOMPSAT multispectral images obtained in 2011 and 2015. To assure the spectral consistency between the two images, radiometric corrections of atmospheric and shadow effects were applied prior to multi-temporal analysis. The normalized difference vegetation index (NDVI) of each image and the NDVI difference (${\Delta}NDVI=NDVI_{2015}-NDVI_{2011}$) between two images were derived. All negative ΔNDVI values were initially considered any pine stands, including both pitch canker damaged trees and other trees, that showed the decrease of crown foliage from 2011 to 2015. Next, $NDVI_{2015}$ was used to exclude the canopy decline unrelated to the pitch canker damage. Field survey data were used to find the spectral characteristics of the damaged canopy and to evaluate the detection accuracy from further analysis.Although the detection accuracy as assessed by limited number of field survey on 21 sites was 71%, there were also many false alarms that were spectrally very similar to the damaged canopy. The false alarms were mostly found at the mixed stands of pine and young deciduous trees, which might invade these sites after the pine canopy had already opened by any crown damages. Using both ${\Delta}NDVI$ and $NDVI_{2015}$ could be an effective way to narrow down the potential area of the pitch canker damage in Korea.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.8 no.1
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• pp.64-74
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• 1999

The use of fluoride and other preventive methods caused a dramatic decline in dental caries and the need for restorative dentistry. In our modern society that places a high value on appearance, emphasis is now shifting towards esthetic dentistry which has experienced a high popularity with the development of bonding techniques and materials including porcelain and composite. To satisfy patients wanting whiter teeth and a better looking smile, there are many treatment options ranging from full crown coverage to conservative procedures such as bleaching. Whether bleaching should be combined with other esthetic procedures or used alone depends on the type of discoloration and the patient's willingness to accept the various treatment options. Therefore, in order to obtain a successful esthetic outcome, careful diagnosis and treatment planning followed by consultation with the patient is of utmost importance.