• Journal of the korean academy of Pediatric Dentistry
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• v.24 no.4
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• pp.781-787
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• 1997

In spite of the improvements of the techniques in the field of preventive dentistry, many children still present with extensive destruction of primary anterior teeth. Not only the practioner must consider the pulp state of the primary incisor, but also restore the form, function and esthetics of the tooth. Restorative treatment of primary incisor tooth requires durability, retention and esthetics. Stainless steel crowns used in restoring primary anterior teeth is retentive and durable in comparison with the composite resin, celluloid crown. But they are not esthetic. To enhance the esthetics of the anterior stainless steel crown without reducing its superior retention, an open-face stainless steel crown has been suggested. Several authors have suggested cutting away the labial portion of the stainless steel crown and placing the composite resin in that area. By following this technique, the practioner can prepare a retentive, durable, and esthetic restoration for primary teeth which have suffered from extensive loss of teeth structure. In addition, the single missing primary anterior teeth can be successfully restored by soldering the stainless steel crown together. Open-face stainless steel crown is indicated in the areas of large interproximal lesions involving incisal edge, crown fracture with pulp exposure and congenital malformation of the teeth. By this technique, the practioner can restore primary anterior teeth successfully regardless of the amount of remaining tooth structure, bruxism habit and presence of attrition. In this case, rampant caries with extensive loss of tooth structure and single missing of primary anterior tooth hart been successfully treated with open-face stainless steel crown.

• Korean Journal of Environment and Ecology
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• v.33 no.5
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• pp.578-586
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• 2019

The purpose of this study was to investigate the change of spatial distribution of Korean red pine (Pinus densiflora Siebold & Zucc.) in Hallasan National Park by surveying the distribution and crown density and analyzing by the elevation, slope, orientation, and regional habitat in 2006 and 2015. The total area of the Korean red pine forest was 1,259.9 ha in 2015, which increased by 51.4 ha, or 4.1%, compared to 1,208.5 ha in 2006. For the past 10 years, the area of sparse density with crown density of 11% to 40% of Korean red pine increased by 59.8 ha, the area of moderate density with crown density of 41% to 70% increased by 59.0 ha, and the area of dense density with 71% or more crown density increased by 67.3 ha. In terms of the altitude above sea level, the Korean red pine forest area between 1,010 m and 1,400 m was the largest at 1,003.0 ha or 79.6% of the total area in 2015. The area between 1,100 m and 1,300 m increased, and the area of dense density decreased significantly while the areas of moderate density and sparse density increase. There was no notable change according to the land slope, and the area increased from 2006 regardless of the slope. By direction, 56.4% were distributed in the southwest and southeast directions centered on the south-facing slope with the increase of 27.8 ha over the 10 years while the northwest and northeast directions centered on the north-facing slope decreased by 7.6 ha. Regarding the distribution change of the Korean red pine forest by the region, the Yeongsil area showed an increase of 25.5 ha, or 49.6% of the total area increase, in 2006 while the Ibseog-oreum area including the right side on the Sanbeoleum mountain valley increased by 20.4 ha. The distribution in the Gaemideung area that includes Jogeundeule increased by 7.4 ha while that of Sogbat in Sungpanak Trail decreased by 1.9 ha. This study analyzed the changes in the distribution area and crown density of the Korean red pine forest according to the altitude, slope, direction, and regional habitat in Hallasan National Park. The expansion of Korean red pine forest distribution was limited to the areas where the grass and the shrub was the dominating vegetation structure, or the forest gap was created by the disturbance. On the other hand, the distribution area of the Korean red pine forest surrounded by deciduous broad-leaved forests or mixed vegetation structure is considered to result from the change in density more than the area due to competition with deciduous broad-leaved trees.

• Korean Journal of Environment and Ecology
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• v.35 no.4
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• pp.398-407
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• 2021

This study intended to identify causes of poor tree vigor in the Hanbando coastal forest by investigating its geographical environment, climate condition, soil physicochemical characteristics, and growth condition of Pinus thunbergii. It divided the forest into an area with poor tree vigor or dead standing trees and a control area with good tree vigor and examined them separately. The survey showed that stand density was significantly higher in the area with poor tree vigor. In contrast, the crown width in the area with good tree vigor was wider. The number of dead standing trees and the stand density showed a negative correlation. The stand density and diameter at breast height (DBH), tree height, crown height, and crown width also showed a negative correlation. The result indicated that, as the tree's stand density increases, the crowns of individual trees overlapped and the lower branches died. Then crown height and crown width decreased, and the number of leaves and photosynthesis was reduced, leading to lower tree height and weaker growth of breast diameter. As a result, tree vigor weakened, and combined with environmental pressures from the lack of moisture and nutrients in coastal soil and salty wind, P. thunbergii in coastal areas is expected to die massively. Although the causes of dead standing trees and poor tree vigor of P. thunbergii in the Hanbando coastal forest are complicated, poor management of adequate tree density in response to the growth of P. thunbergii is the primary cause. The secondary cause is external environmental pressures, including unfavorable soil conditions and salty and strong wind that obstruct the growth of P. thunbergii.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.3
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• pp.502-509
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• 2003

After 800 students of Chonbuk National University was examined, 86 people (male : 43, female : 43, mean age : 22.2 years old) was selected as a group of normal occlusion. From their gypsum cast, this conclusion was obtained. 1. Intra-observer measurement errors in buccolingual diameter, maxillary lateral incisors have somewhat bigger errors. In mesiodistal diameter, maxillary first molars and maxillary second molar have bigger numerical value. Mean errors of measurement are 0.051mm at buccolingual diameter of crown and 0.083mm at mesiodistal diameter. 2. Fluctuating asymmetry is 0.030 average in buccolingual diameter, and 0.037 average in mesiodistal diameter. Statistically there are no big differences. 3. Male has longer buccolingual diameter than female in every permanent teeth. Teeth which have statistical difference in buccolingual diameter are maxillary lateral incisor, maxillary canine, maxillary second molar, mandibular central incisor, mandibular canine, mandibular second premolar, and mandibular first molar. In mesiodistal diameter maxillary central incisor, maxillary canine, and mandibular first molar have statistically difference. 4. Tooth which has the biggest difference depending on gender is maxillary lateral incisor in buccolingual diameter and mandibular canine in mesiodistal diameter. 5. Both sexes have similar crown index. Male has bigger value of crown module measurement and crown area measurement in every tooth. Crown area considered as size of tooth from occlusal surface was bigger in male than in female statistically except some teeth, maxillary first premolar, mandibular lateral incisor, first premolar and second premolar.

• Imaging Science in Dentistry
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• v.54 no.1
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• pp.49-56
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• 2024

Purpose: This study evaluated the impact of artifacts generated by metal crowns on the detection of proximal caries lesions in teeth at various distances using cone-beam computed tomography (CBCT). Additionally, the diagnostic impacts of tube current and metal artifact reduction (MAR) were investigated. Materials and Methods: Thirty teeth were arranged within 10 phantoms, each containing 1 first premolar, 1 second premolar, and 1 second molar. A sound first molar (for the control group) or a tooth with a metal crown was placed. Of the 60 proximal surfaces evaluated, 15 were sound and 45 exhibited enamel caries. CBCT scans were acquired using an OP300 Maxio unit (Instrumentarium, Tuusula, Finland), while varying the tube current (4, 8, or 12.5 mA) and enabling or disabling MAR. Five observers assessed mesial and distal surfaces using a 5-point scale. Multi-way analysis of variance was employed for data comparison, with P<0.05 indicating statistical significance. Results: The area under the curve (AUC) varied from 0.40 to 0.60 (sensitivity: 0.28-0.45, specificity: 0.44-0.80). The diagnostic accuracy was not significantly affected by the presence of a metal crown, milliamperage, or MAR(P>0.05). However, the overall AUC and specificity were significantly lower for surfaces near a crown (P<0.05). Conclusion: CBCT-based caries detection was not influenced by the presence of a metal crown, variations in milliamperage, or MAR activation. However, the diagnostic accuracy was low and was further diminished for surfaces near a crown. Consequently, CBCT is not recommended for the detection of incipient caries lesions.

• Journal of the Korean Association of Geographic Information Studies
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• v.17 no.1
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• pp.1-12
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• 2014

Crown fire, the main propagation type of large forest fire, has caused extreme damage with the fast spread rate and the high flame intensity. In this paper, we developed the probability equation to predict the crown fires using the spatial features of topography, fuel and weather in damaged area by crown fire. Eighteen variables were collected and then classified by burn severity utilizing geographic information system and remote sensing. Crown fire ratio and logistic regression model were used to select related variables and to estimate the weights for the classes of each variables. As a results, elevation, forest type, elevation relief ratio, folded aspect, plan curvature and solar insolation were related to the crown fire propagation. The crown fire propagation probability equation may can be applied to the priority setting of fuel treatment and suppression resources allocation for forest fire.

• Journal of Oral Medicine and Pain
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• v.13 no.1
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• pp.13-21
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• 1988

The author studied the vertical height of tooth crown and the amounts of alveolar bone resorption with age. All 84 subjects(44 male, 40female) who visited Dental hospital of Wonkwang University with no history of sever periodontal disease and no experience of periodontal surgery. 84 subject were divided into 3 groups by age, that is, group I(28-32yrs), group II(38-42yrs), and group III(48-52yrs). Informal radiogram with bite wing film(horizontal angulation : $0^{\circ}$, vertical angulation : $+5^{\circ}~+10^{\circ}$) were taken on premolar and molar area. The distances from cusp tip to cementoenamel junction (vertical height of tooth crown) and from cementoenamel junction alveolar crest(amount of alveolar bone resorption) were measured, and then recorded data from 946 teeth were statistically analysed. This study was undertaken to obtain the data for age estimation by the changes of tooth crown height and alveolar bone resorption in the point of forensic odontology. The obtained results were as follows : 1. The average crown height of mandibular right 1st. molar was 7.1mm in group I, 6.7mm in group II, and 6.6mm group III, and the average amount of alveolar bone resorption on mandibular right 1st. molar were 1.8mm in group I, 2.5mm in group II, and 3.0mm in group III. Ratio of tooth crown height to amount of alveolar bone resorption was 4.0:1 in groupI, 2.7:1 in group II, and 2.2:1 in group III, the ratio was decreased with age. 2. In comparison with upper teeth and lower teeth in ipsilateral side, the average value of tooth crown height and amount of alveolar bone resorption were slightly higher in upper arch than those in lower arch, but there was not a statistically significant difference. 3. The ratio of height of tooth crown to amount of alveolar bone resorption was decreased with age, and which depended mainly upon the change of amount of alveolar bone resorption rather than the change of tooth crown height.

• The Journal of Korean Academy of Prosthodontics
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• v.50 no.3
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• pp.204-209
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• 2012

Surgical extrusion, immediate extrusion following tooth luxation, is a method to preserve one's natural tooth and achieve esthetic restoration without additional periodontal surgery when subgingival dental caries or crown fracture occurs. A 16-year-old male was referred to the clinic from the department of operative dentistry for the esthetic restoration of maxillary left lateral incisor. Due to the crown to root fracture, the tooth was endodontically treated with a buccal crown length of 4 mm. When the palatal flap was elevated, the mesiopalatal cervical fracture area was situated 3-4 mm subgingivally. Crown lengthening was achieved through surgical extrusion. After 3 months of clinical observation and provisional restoration, the maxillary left central incisor was restored with all ceramic crown and obtained a satisfactory clinical result.

• Korean Journal of Agricultural Science
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• v.10 no.1
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• pp.9-21
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• 1983

The structures of oak stands were studied in relation to their productivity. Three plots classified by the site quality following to altitude, were selected on the oak stand located at Naryongri Eunsanmyun Buyeogun. The site qualities of the stand studied were generally estimated to be moderate in respect to some soil physical and chemical properties. Quercus variabilis was dominant species in the vegetation composition of the stand studied. The crown densities of the stand were varied from 65.4% in plot I to 78.2% in plot III and the parts, occupied with oak trees, ranged from 44.4% in plot I to 65.9% in plot III in the density. In the contrast to crown density, the growing stocks of oak trees ranged from $3.937m^3$ in plot I (73.4% of plot total) to $2.075m^3$ in plot III (84.3% of plot total). The occupied ratios, measured by crown class, exhibited dissimilarity between crown projection area and volume, and also the ratios brought into different patterns by plot. Highly significant correlations were proved between crown projection areas and volumes of individual oak trees by plot, but not proved in the relations by crown class. The cumulative growth, current annual increment and mean annual increment displayed various patterns by plot and by crown class in the heights, D. B. H. s and volumes of oak trees. The maximum values of current annual increment of height were generally recorded in 10 to 20 years, earlier than those of D. B. H. The mean annual increment of height, D. B. H. and volume maintained similar levels after about 10 years and fluctuated irregularly. The crown projection area and volume following to thinning decreased in the order of the thinning methods of grade A < grade B < crown thinning$90m^3/ha$ in about 40 years in the productivity of volume of the oak stand studied.

• Journal of Korean Society of Forest Science
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• v.100 no.3
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• pp.359-366
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• 2011

The objective of this study was to analyze the changes of crown fire hazard possibility from the effects of forest tending works (FTW) in Pinus densiflora stands in Korea. The study sites were located in Youngju (FTW) and Bonghwa (Control) areas. Ten representative sample trees were destructively felled at each areas to analyze the crown fuel characteristics. The results of this study showed that crown fuel moisture content in Youngju and Bonghwa areas were 103.6% and 104.4%, respectively. The needles and twigs with less than 1cm diameter accounted 50.3% of the total crown fuel load in Youngju area and 62.0% in Bonghwa area. On the other hand, it was observed in Youngju that the canopy bulk density was $0.11kg/m^3$ lower but have 1.3 m higher average canopy base height therefore having a possibility of lower crown fire hazard as compared to Bonghwa that had higher canopy bulk density and lower canopy base height.