• The Journal of the Korean dental association
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• v.54 no.6
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• pp.414-428
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• 2016

Objectives: The aim of this study was to assess the morphologic characteristics of two types of stainless steel crowns (SSCs) for the first primary molar using a 3D scanner. Study design: Two types of SSCs, KIDS CROWN (KC) and 3M ESPE ND-96 (ND), for the first primary molars were scanned using a 3D scanner. The mesiodistal and buccolingual diameters at the height of the contour and the cervical margin, occlusocervical diameters on the mesial, distal, buccal, and lingual aspects were measured, and the crown shape ratio, the smooth surface crown height ratio, and the cervical convergence were calculated. Results: In the crown shape ratio of the mandibular SSC, KC was larger buccolingually compared with ND. In the smooth surface crown height ratio, ND was larger than KC in all of the maxilla and mesial, distal, and lingual aspects of the mandible. ND was more convergent to the cervical mesiodistally and buccolingually compared with KC. Conclusion: In the superimposed images of the maxillary SSC, the mesiolingual and distolingual line angles of KC were more prominent compared with ND. In the mandible, ND demonstrated higher cusps and more obvious buccal developmental lobes than KC. ND showed a larger cervical undercut than KC.

• Journal of Dental Rehabilitation and Applied Science
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• v.19 no.3
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• pp.139-151
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• 2003

This study was to evaluate and to compare the compressive strength and the displacement effecting the abutment or the residual ridge which are transformed by the angle and the heights of the konus denture inner crown when restorating the unilateral konus denture by using the mandibular canine and the 1st premolar as an abutment. The author made 9 different models for different inner crown heights and konus angles. The inner crown height were divided to 5mm, 6mm, and 7mm and konus angles was divided to $4^{\circ}$, $6^{\circ}$, and $8^{\circ}$. And then in each model, 5kg of $15^{\circ}$ mesial load was stressed on the central fossa of the 1st premolar and the 1st molar. The stresses and displacement were measured using the finite element analysis. The results were as follows 1. The maximum compressive strength was shown on the connective area of the abutment and the denture base. 2. As the angle of the inner crown becomes increased, the compressive strength was shown smaller. 3. As the height of the inner crown becomes increased, the maximum compressive strength was shown smaller while the compressive strength of the root apex and the residual ridge showed larger. 4. When the stress was loaded only on the 1st premolar, the more compressive strength was concentrated on the root apex area of the 1st premolar. 5. When the stress was loaded only on the 1st premolar, the compressive strength was concentrated uniformly on the abutment and the residual ridge. 6. When the stress was loaded only on the 1st molar, the maximum displacement was shown on the distal part of the residual ridge.

• Journal of Periodontal and Implant Science
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• v.28 no.3
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• pp.507-517
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• 1998

This study was performed to investigate the soft tissue changes around single implant-supported crowns during followup periods. Twenty patients(31 implants) whose single missing tooth in the maxillary anterior region had been replaced with an single implant-supported crown were recruited for the study. Crown length, soft tissue level and papilla height at the single implant-supported crowns were measured at follow-up examination and calculated from the slides taken at time of crown placement. as well Papilla index was scored from the slides taken at the time of crown placement and follow-up examination. A very little amount of recession occurred and the soft tissue level moved more apically and the papilla height increased significantly (p<0.01). Especially, both mesial and distal papilla index at single implant-supported crowns increased significantly during follow-up periods (p<0.001). When the two slides taken at the time of crown placement and follow-up were compared simultaneously, except one site, papillae size increased at all sites. From the results of the study, the interdental papillae at the single implant-supported crowns seemed to regenerate significantly and their crown margins were stable during follow-up periods. Hence it is indicated that various surgical interventions at on early stage to enhance soft tissue esthetics arourd single implants may be unnecessary.

• Journal of Korean Society of Forest Science
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• v.97 no.5
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• pp.501-507
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• 2008

The data of crown width with 4 directions, DBH, tree height, and coordinate for sample trees were collected from 30 permanent sample plots in secondary fore st of the Maoershan Experimental Forestry Farm, Northeast China. In this paper, the competition of individual trees in stand were discussed for secondary forest by using iterative Hegyi competition index and crown overlap index that represented the competitive and cooperative interactions among neighboring trees. Active competitors of subject tree in the competition zone were selected to calculate the iterative competition index. Using the results of crown classification based on the equal crown projection area, a new distance dependent competition index called crown overlap index (COI) was developed for secondary forest. The COI performed well in describing the crown competition rather than crown competition factor (CCF). The individual-based competition index discussed in this paper will provide more precise for developing individual tree growth models for secondary forest and it can also use to adjust the stand structure for spatial optimal management.

• The Korean Journal of Ecology
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• v.8 no.4
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• pp.197-200
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• 1985

The relations of crown width and DBH for Pinus densiflora, Pinus rigida, Pinus koraiensis, and Ginkgo biloba were accomplished to estimate the level of crown competition. Measurements of the relations revealed that crown width and DBH were highly correlated for the same species. Also it seems that these relations are independent of age and site quality. The results of regression analysis were as follow: P. densiflora, Y=0.3477X+0.3828 r=0.95 p. rigida, Y=0.3537X+0.1645 r=0.95 P. koraiensis, Y=0.2895X+0.6310 r=0.92 G. biloba, Y=0.4360X+0.0995 r=0.90 The significant differences between G. biloba and pine species seems due to their structural differences of crown formation according to tree species. As results of computing Maximum Crown Area and Crown Competition Factor as indices of crown competition, they indicated that P. densiflora would grow better under the natural conditions.

• Korean Journal of Environment and Ecology
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• v.33 no.5
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• pp.587-595
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• 2019

This study analyzed the influence of the environmental factor of each vegetation type in an urban, mountainous park (Tangeumdae Park in Chungju) on air ion. The measuring points were divided according to the tree species, diameter at breast height, crown density, and layered structure, and the meteorological factors and the air ion were measured. The results of the measurement showed the average generation of positive ions of $610.90{\pm}50.27ea/cm^3$, the average generation of negative ions of $723.58{\pm}64.25ea/cm^3$, and the air ion index of $1.19{\pm}0.10$. The results of the analysis, according to the vegetation type, are as follows. Firstly, the air ion varied according to the species, the chest diameter at breast height, and the layered structure, and was analyzed to be statistically significant. Secondly, the air ion and the vegetation type showed a positive correlation with the species, diameter at breast height, crown density, and layered structure. The cation showed a negative correlation with the species, diameter at breast height, and the crown density, and the anion showed a positive correlation with the species, the diameter at breast height, crown density, and layered structure. Thirdly, the ion index in ridges had a higher correlation with the vegetation type than the meteorological factors. In detail, the correlation was higher in the species > layered structure > crown density > diameter at breast height. This study had the limitation of evaluating air ions in the ridge. Therefore, future studies on air ion should consider both terrain structure and vegetation type and analyze the seasonal changes and comparison.

• 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.

• Proceedings of KOSOMES biannual meeting
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• 2017.11a
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• pp.104-105
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• 2017

• Journal of Korean Society of Forest Science
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• v.89 no.2
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• pp.256-259
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• 2000

D.B.H., height, crown length, crown width, crown form, crown area, and crown volume of dead and live trees were measured and the discriminant analysis was conducted to assess individual tree risk-rating in the pine forest seriously infested by the pine needle gall midge. Thecodiplosis japonensis. Crown length, crown form, crown area, and crown volume of live tree were significantly higher than those of dead tree, while D.B.H. and tree height were not different significantly. These results represent that the trees with higher and wider crown and larger crown volume have relatively higher probability to survive from the infestation by the pine needle gall midge. Variables selected in the functions of discriminant analysis were crown area, ratio of crown length, crown form, ratio of crown volume to crown area, and ratio of crown width.

• Journal of The Korean Society of Grassland and Forage Science
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• v.5 no.1
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• pp.33-36
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• 1985

This experiment was carried out to investigate the effect of crown density of trees on the growth and yield of cool-season grasses in forest. The species used in this study was orchard-grass (Dactylis glomerata L.) and 4 levels of tree crown density(O=full sunlight, 25, 50 and 75%) were treated. The experiment was performed at the experimental filed of the Livestock Experiment Station in Suweon, during 1979 to 1950. The results obtained are summarized as follows: 1. Maximum leaf area was obtained at 25% crown density of trees, followed by 0, 50 and 75%, regardless of cutting times. 2. Plant height tended to increase as the crown density of trees increased. However, there was no difference between 0% and 25% crown density of trees. 3. There was a negative correlation between plant height and leaf area of orchardgrass grown under pine trees. 4. The more dry matter yield of orchardgrass was obtained at 25% crown density of trees (p<0.05), follwed by 0, 50 and 75%, respectively. However, there was no significant difference between 0% and 50% crown density of trees. Therefore it is suggested that the critical level of crown density of trees is 50% to culture of cool-season grasses in forest.