• Restorative Dentistry and Endodontics
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• v.26 no.2
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• pp.180-187
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• 2001

The structure of current guides is largely illogical and without any rational use of color ordering. The shade guides are generally made of plastic (rather than the actual composite material) and do not accurately depict the true shade. translucency. or opacity of the composite resin after polymerization. To solve this problem, information based on evaluations of natural teeth and material that use the same method and experimental conditions is necessary. The present investigation measured the color of natural maxillary anterior teeth in vivo and compared the results with those of composite resins. 269 Korean subjects were selected for this study. Intact central incisor. lateral incisor. and canine were selected. The clinical crowns were free of caries or restorations. The middle site of the coronal portion on the labial surface of the tooth was measured by Chroma Meter. The five light activated. resin-based materials (Amelogen, Denfil, Elitefil, Spectrum, Z100) were used in this study. Resin composite was condensed into plastic mold with a diameter of 8mm and a thickness of 4mm. pressed between glass plates to flatten the surfaces. and polymerized using a Visilux II visible light activation unit. The surfaces were polished sequentially on wet sandpaper. Color measurements of each specimen were accomplished by Chroma Meter. A computer program that compares each tooth color with each composite resin color was written and the minimum CIELAB color difference ($\Delta$E$^*$) between tooth and each material was calculated. Under the conditions of this study: 1. Teeth tend to become darker with advancing age. 2. Canines were darker. more yellow. and less green than incisors. 3. The teeth from the women were lighter. more green. and less yellow than the male teeth. 4. In general. composite resins were lighter. more green. and less yellow than teeth. Deficiencies were noted in Hues in YR range. 5. Mean color differences between the five composite resin products and teeth were detectable to the naked eye($\Delta$E$^*$>1.0). 6. In comparing the mean $\Delta$E$^*$ values of materials. Spectrum showed the least followed by Z100, Elitefil, Amelogen, Denfil in increasing order.

• Journal of Korean society of Dental Hygiene
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• v.12 no.4
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• pp.733-739
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• 2012

Objectives : To Compare the degree of survival rate of gingival fibroblasts, which is concerned with teeth adherence based on the type of avulsed tooth's storage solution. Methods : Different media gingival fibroblasts were stored in Dulbecco's modified Eagle's medium(DMEM), Hank's balanced salt solution(HBSS), milk, saline, and green tea in for 1, 2, 3 hours. And, MTT assay was conducted to compare survival rate of human gingival fibroblasts. Results : 1. The survival rate of gingival fibroblasts in DMEM and HBSS was higher than thoes in other storage media( Milk> Saline> Green tea). 2. The survival rate of gingival fibroblasts in milk, saline and green tea decreased as time passed. 3. Because of low osmotic pressure, green tea showed decrease of survival rate of gingival fibroblasts. Conclusion : DMEM and HBSS were the most effective storage media for gingival fibroblast. Among milk, saline, green tea, milk is most effective storage media for keeping gingival fibroblasts. Milk is recommended for storage media of avulsed tooth for keeping viability of cells.

• Journal of dental hygiene science
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• v.13 no.2
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• pp.191-196
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• 2013

The purpose of this study was to evaluate the tooth brightening of whitening dentifrice and to determine the tooth stain level over 20 days depending on beverages that have various pH values after using whitening dentifrice. Thirty teeth were randomly divided into two groups. Group 1 was provided with a whitening dentifrice for 3 minutes and group 2 was treated with a control dentifrice for 3 minutes thrice a day for four weeks. All teeth were photographed using a digital imaging system under a stereomicroscope (magnification, ${\times}10$). After four weeks, the ten teeth were immersed in the tea solution, another of ten teeth were immersed in the orange juice and the other of the teeth were immersed in the coffee solution. Three solutions were renewed each day for the appropriate groups. Stain development was monitored under a stereomicroscope daily over 20 days period by immersion of teeth in a tea, juice, coffee solution at room temperature ($25^{\circ}C$) in individual container. Whitening dentifrice gave a statistically higher value of overall color change as compared to control dentifrice after 21 days (p<0.05). Stain level of whiten tooth immersed in orange juice was the grestest overall color change, but there was not statistically significant difference (p>0.05). On the other hand, stain level of whiten tooth immersed in coffee and green tea showed a statistically significant difference after 15 days and 5 days, respectively (p<0.05). Tooth immersed in green tea was higher negative value than control dentifrice. The tooth using whitening dentifrice was shown to be effectively whiter color than control dentifrice. However, stain level by orange juice, coffee and green tea has a strong staining effect.

• Journal of the korean academy of Pediatric Dentistry
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• v.44 no.3
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• pp.378-383
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• 2017

There are many reasons for tooth discoloration. An increase in the bilirubin level may cause tooth discolorations. Such cases are rare, but most involve tooth discoloration with a greenish hue. The purpose of this case report is to describe green discoloration of the primary dentition in the presence of neonatal hyperbilirubinemia. 2 boys aged 16 and 22-months presented with chief complaints of erupting teeth of abnormal color. Their primary teeth exhibited a greenish discoloration along enamel hypoplasia. Both patients were born prematurely with a low birth weight and had been diagnosed with neonatal hyperbilirubinemia. Systematic diseases can affect the hard tissue of teeth during their formation and result in changes in tooth color. Periodic follow-ups are required for establishing a normal dental condition and meeting the esthetic needs of patients. A pediatric dentist may be the first person to observe patients with discoloration in their primary dentition. In such cases the dentist can deduce the systematic disease responsible for this discoloration.

• Archives of Pharmacal Research
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• v.21 no.3
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• pp.348-352
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• 1998

Different bacteria wwere seperated from saliva and teeth of cariogenic patients and identified by a variety of morphological and biochemical tests. Extracts of green tea strongly inhibited Escherichia coli, Streptococcus salivarius and Streptococcus mutans. The antibacterial effect of green and black tea extracts were compared with those of amoxicillin, cephradine and eugenol.

• The korean journal of orthodontics
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• v.15 no.2
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• pp.271-277
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• 1985

With modification of the acid etch technique and improvements of the physical and mechanical properties of the acrylic resin, the removal of directly bonded attachments and the finishing of the underlying enamel have become an acute clinical problem. This study was to evaluation the efficacy of recently introduced instrumentation and techniques to remove bonded brackets and residual resin, and restore the affected enamel surface to an acceptable clinical condition. Fortyeight premolar which were scheduled for extraction for orthodontic purposes were bonded with brackets using super-C ortho. Four additional premolars with untreated surfaces were used as controls. After one weak the brackets were removed and the residual resin removed by hand scaler, green stone, green rubber wheel, sandpaper disc, tungsten carbide bur, Sof-lex disc. Half the experimental teeth were given a final pumicing and then all were extracted and stored in 50 percent ethanol. The scanning electron microscopy was used to evaluated the enamel surface. Following results were obtained; 1. A satisfactory result was obtained by means of the Sof-lex disc. 2. The order of the scratch formation was the procedure using hand scaler, green atone, tungsten carbide bur, sandpaper disc, green rubber wheel, and Sof-lex disc. 3. The procedures using green stone and tungsten carbide bur showed many groove formations and the other procedures showed none. 4. final pumicing serves effectively to remove residual adhesive and restore the enamel surface.

• Journal of Computational Design and Engineering
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• v.1 no.1
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• pp.27-36
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• 2014

Similar to the essential components of many mechanical systems, the geometrical properties of the teeth of spiral bevel gears greatly influence the kinematic and dynamic behaviors of mechanical systems. Logarithmic spiral bevel gears show a unique advantage in transmission due to their constant spiral angle property. However, a mathematical model suitable for accurate digital modeling, differential geometrical characteristics, and related contact analysis methods for tooth surfaces have not been deeply investigated, since such gears are not convenient in traditional cutting manufacturing in the gear industry. Accurate mathematical modeling of the tooth surface geometry for logarithmic spiral bevel gears is developed in this study, based on the basic gearing kinematics and spherical involute geometry along with the tangent planes geometry; actually, the tooth surface is a parametric surface defined on a parallelogrammic domain. Equivalence proof of the tooth surface geometry is then given in order to greatly simplify the mathematical model. As major factors affecting the lubrication, surface fatigue, contact stress, wear, and manufacturability of gear teeth, the differential geometrical characteristics of the tooth surface are summarized using classical fundamental forms. By using the geometrical properties mentioned, manufacturability (and its limitation in logarithmic spiral bevel gears) is analyzed using precision forging and multiaxis freeform milling, rather than classical cradle-type machine tool based milling or hobbing. Geometry and manufacturability analysis results show that logarithmic spiral gears have many application advantages, but many urgent issues such as contact tooth analysis for precision plastic forming and multiaxis freeform milling also need to be solved in a further study.

• Journal of the korean academy of Pediatric Dentistry
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• v.24 no.1
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• pp.235-246
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• 1997

This study was done as a pilot study to develop a color test measuring children's dental anxiety. The subjects of study were 511 preschool children aged from 3 to 6. Caries experience was examined. Children's drawings of the dentist were collected and analyzed by the method of human figure drawing test modified by Sonnenberg and Venham. Colors of high dental anxiety level were black, brown, purple, red, yellow, pink, green, orange, blue, gray, yellow ochre, and white in that order. Colors of high frequency of use were yellow ochre, green, blue, red, orange, pink, black & purple, yellow, brown, gray, and white in that order. As the age increased, white & gray, yellow ochre, and blue increased and black, purple, and pink decreased. Boys liked green and blue, and girls liked orange and yellow. Filled teeth rate was highest in yellow ochre group and very low in black group. Children who had an educational dental visit before the test used green color more than the rest of children.

• Restorative Dentistry and Endodontics
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• v.15 no.2
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• pp.115-121
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• 1990

Forty extracted human mandibular second molars with C-shaped canal were chosen to study the anatomy of the root canal. The experimental teeth were injected with china ink, decalcified and cleared with Winter green oil, in vitro, to study the number of root, root canal, canal per root, frequency and location of lateral canal and transverse anastomosis. 1. All teedth had one root. 2. Mesial roots with two canals were 25%, and mesial roots with one canal were 75%. All distal roots had one canal. 3. In the roots with two canals, the common apical foramen appeared in 20% and the separte apical foramen appeared in 80%. 4. The frequence of lateral canal was 33.3% and the most frequent region was middle 1/3. 5. All teeth had the transverse anastomosis in all region of the roots.

• Korean Journal of Environmental Biology
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• v.37 no.3
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• pp.293-298
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• 2019

A marine ulvalean species (Chlorophyta) was collected from the eastern coast of Korea. This species is morphologically characterized by a distromatic, dark to medium green and mostly irregularly orbicular or irregularly expanded thallus with entire or undulate margin without serrations. Vegetative cells are irregularly polygonal with distinctly rounded corners in shape, and have chloroplast completely covering the outer cell wall and one to two pyrenoids per cell. In a phylogenetic tree based on ITS (Internal Transcribed Spacer) sequences, this Korean alga nests in the same clade with Ulva sublittoralis, as a sister clade of U. californica, U. flexuosa and U. tanneri, which share the irregularly orbicular or expanded thallus normally without teeth cells. The genetic divergence between them is intraspecific within Ulva. Accordingly, it is identified as U. sublittoralis based on the morphological and molecular data. This is the first record of Ulva sublittoralis in the Korean marine algal flora.