A COMPARATIVE STUDY OF THE ANGLES BETWEEN CROWN AXIS AND ROOT AXIS IN MESIODISTAL DIRECTION BY USING ORTHOPANTOMOGRAM

Kim, Young Joon,Choi, Hyun Sil 대한치과교정학회 1996 대한치과교정학회지 Vol.26 No.6

Orthopantomogram is commonly used to evaluate root parallelism. "Good parallelism" between roots is widely accepted as one of the guidelines of a successful orthodontic treatment. In case there was a large angle between crown axis and root axis, and if we valued only the position of crown in establishing occlusal relationship without considering of the situation of root, the problem of root arrangement between adjacent teeth would be occurred. The estimate of root parallelism in mesiodistal direction before and after orthodontic treatment must be emphasized. The intent of this study was to determine the clinical importance and correlation of the angle between crown axis and root axis. Orthopantomograms of 105 orthodontic patients being treated in Yonsei university were used in this study. Twenty-eight teeth in both maxilla and mandible were selected and analyzed quantitively to evaluate the angle between crown axis and root axis, and obtain the correlationship among the individual teeth. The results are as follows: 1. Among the teeth presenting normal distribution, the maxillary right canine showed the largest mean value(5.73±4.42°), which was composed of the crown-root angles, and the mandibular left lateral incisor showed the smallest mean value(0.60±3.76°). 2. The crown-root angles of the maxillary incisors and the first molars, and the mandibular central incisors and the first molars didn`t show normal distribution and the ranges of these angles were dispersed. 3. Significant differences were present between the crown axis and the root axis except for lower first premolars.(p<0.05) 4. No significant difference was present for the crown-root angle between right and left side.(p<0.05) 5. No significant difference was present for the crown-root angle between male and female except for lower left first premolar.(p<0.05) 6. In the upper right quadrant, significant correlations were present between crown-root angles of the central incisor and lateral incisor, lateral incisor and canine. In the upper left quadrant, significant correlations were present between crown-root angles of the central incisor and lateral incisor. In the lower right quadrant, significant correlations were present between crown-root angles of the central incisor and lateral incisor, first molar and second molar. In the lower left quadrant, significant correlations were present between crown-root angles of the central incisor and lateral incisor, lateral incisor and canine, first molar and second molar.(p<0.05)

5~6세기 신라 慶山地域 政治體의 冠

金載烈(Kim, Jae-yul) 신라사학회 2010 新羅史學報 Vol.0 No.20

冠은 5~6세기 신라를 대표하는 고분 출토 유물 중 하나다. 기존 新羅冠 연구는 신라 전체 영역 출토품을 대상으로 冠의 기원과 계통, 정치, 사회적 의의를 논했다. 이 같은 기존 신라관 연구는 신라 전반에 걸친 冠의 양상과 의의를 파악하기에는 매우 적합하지만, 당시 신라를 구성했던 지역 정치체 내부의 冠에 대한 미시적인 관찰과 의의 도출에는 한계를 지니기 마련이다. 이 글은 그런 관점에서 慶山地域 政治體의 冠을 대상으로 삼았다. 경산지역의 冠은 양적 풍성함과 함께 古塚이 조영되는 모든 기간에 걸쳐 지속된다. 따라서 冠의 소유자의 구별, 소유자에 따른 冠의 획득, 동시기의 金銅冠의 제작 기법 비교를 통한 제작공인과 제작지의 구별, 경산지역 정치체 제작 여부 등을 살펴볼 수 있다. 경산지역의 冠은 金銅冠과 帽冠(冠飾ㆍ冠帽)으로 구성된다. 金銅冠은 신라 시원ㆍ표준ㆍ퇴화형식 관이 모두 확인되고 순차적 변화상을 보인다. 冠飾과 冠帽 역시 그러하다. 경산지역의 冠 소유자는 고총급 대형묘와 중형묘 주피장자로 구분되며, 전자는 신라 왕경에서 冠을 획득했을 가능성이 높고 후자는 경산지역 고총 세력의 영향력 아래冠 소유가 이루어졌다. 경산지역의 5세기 초엽 고총급 대형묘 주피장자가 소유한 金銅冠 두 점은 제작기법 차이를 보여 분명히 다른 공인이 제작한 것이다. 그리고 冠의 수요가 증가하는 시점에 들어 중형묘 주피장자의 冠을 중심으로 경산지역의 金銅冠 제작이 확인된다. This article is to investigate the aspect of Silla crown in Gyeongsan during 5~6C Silla on the basis of archeological materials. The existing archeological study on Silla crown tends to investigate the diachronic change in Silla crown and spreading course. As such, it studies the Silla crown excavated in all area of Silla. Such tendency of study is quite proper to elucidate the overall aspect of Silla crown. However, checking the aspect of Silla crown in the local polity of diverse regions which constituted Silla is subject to limit. Thus, this article focuses on the materials on Silla crown excavated in Gyeongsan where most of Silla crown was excavated among diverse local polity of Silla. Namely, it intends to identify what kind of Silla crown existed in the local polity of Gyeongsan, what the position of owner of Silla crown was and that the local polity in Gyeongsan personally produced some crown. Further, it intends to investigate the spreading course in the age. As a result, Silla crowns composed of gilt-bronze crown, crown ornament, crown in the form of hat are identified in the local polity in Gyeongsan, Among them, gilt-bronze crown is sequentially identified in the form of original type standard type and degradation type. The owner of Silla crown is divided into the possessors of large tomb and medium tomb. While the Silla crowns owned by possessors of large tomb are usually well finished, those owned by possessors of medium tomb are poorly finished in degraded form. Among them, the crown owned by possessors of medium tomb were surely produced in local polity in Gyoengsan. Appearing in local polity in Gyeongsan at the beginning of the 5th century for the first time, the crown continued until the middle of the 6th century without interruption. It seems that the possessors of large tombs acquired Silla crown from political body in Gyeongju, the capital of Silla. Then, the possessors of medium tomb in local polity of Gyeongsan also began to own Silla crown. Then, the possessor of medium tomb and crown was judged to bury the crown in the tomb due to time.

신품종 사계성 딸기 ‘고하’의 고랭지 여름재배 시 관부수와 화방제거에 따른 생육 및 수량

이종남(Jong Nam Lee),김혜진(Hye Jin Kim),김기덕(Ki Deog Kim),유동림(Dong Lim Yoo),임주성(Ju Sung Im),용영록(Young Rok Yeoung) 한국원예학회 2014 원예과학기술지 Vol.32 No.1

This study was conducted to investigate the effects of crown numbers on growth and yield of ever-bearing strawberry (Fragaria × ananassa Duch.) Goha cultivar. Strawberry seedlings were planted with 55 × 30 cm distance on April 29, and the randomized block experimental was designed by putting the crown numbers by 1, 3, 5 and crown-unremoved as the control. At the early growth stage, as the numbers of crown decreased, the size of leaf became larger and inflorescence diameter became thicker. Plant height became higher as the number of crown increased at the final harvesting time. Fresh weight of crown-unremoved plants was 118 g, showing 77.2 g higher than that of plants with one crown. Numbers of the developed inflorescence of plants with five crowns and crown-unremoved was 20.1, whereas 6.8 of plants with one crown, resulted in 13.3 more crowns. However, crown number did not significantly affect the fruit quality. As the crown number increased, the average fruit weight was lighter and the marketable fruit rate was shown to decrease significantly. The marketable yield of crown-unremoved plants was 17,372 kg?ha^-1, showing 68% higher than plants with one crown. Therefore, crown management without thinning crowns was recommended and inflorescence thickness less than 3 mm should be removed for successful production of ever-bearing strawberry ‘Goha’ cultivar during summer season.

Six-year clinical performance of lithium disilicate glass-ceramic CAD-CAM versus metal-ceramic crowns

Ahmed Aziz,Omar El-Mowafy 대한치과보철학회 2023 The Journal of Advanced Prosthodontics Vol.15 No.1

PURPOSE. To assess the clinical performance of monolithic CAD-CAM lithium disilicate glass-ceramic (LDGC) crowns and metal-ceramic (MC) crowns provided by predoctoral students. This study also assessed the effects of patient and provider-related factors on their clinical performance as well as patient preference for these types of crowns. MATERIALS AND METHODS. Twenty-five patients who received 50 crowns (25 LDGC CAD-CAM and 25 MC) provided by predoctoral students were retrospectively examined. LDGC CAD-CAM crowns were milled in-house using the CEREC Bluecam system and cemented with either RelyX Unicem or Calibra Esthetic resin cements. MC crowns were cemented with RelyX Unicem cement. Clinical assessment of the crowns and the supporting periodontal structures were performed following the modified California Dental Association (CDA) criteria. Patients’ preference was recorded using a visual analog scale (VAS). The results were statistically analyzed using log-rank test, Pearson Chi-squared test and Kaplan-Meier survival analysis. RESULTS. Twelve complications were observed in the MC crown group (9-esthetic, 2-technical and 1-biological). In comparison, 2 complications in the LDGC CAD-CAM crown group were observed (1-technical and 1-esthetic). The 6-year cumulative survival rates for MC crowns and LDGC CAD-CAM were 90.8% and 96%, respectively, whereas the success rates were 83.4% and 96%, respectively. Overall, patients preferred the esthetic outcomes of LDGC CAD-CAM crowns over MC crowns. CONCLUSION. The high survival and success rates, low number of complications, and the high level of patients’ acceptance of monolithic LDGC CAD-CAM crowns lend them well as predictable and viable alternatives to the “gold standard” MC crowns.

이중관 국소의치의 외관 제작기법에 관한 고찰

임장섭 부산대학교 병원 암연구소 2006 부산대병원학술지 Vol.- No.20

Purpose: The purpose of this study was to investigate clinical usability of the outer crown fabrication methods for double crown retained RPD. Method: Three inner crowns with cone angles of 2 degrees, made of Co-Cr alloys, were prepared. According to different fabrication methods for outer crown, such as lost-wax, cast-on, and electroformed technique, three different outer crowns were fabricated. Using the universal testing machine (Tinius Olsen 1000, Tinius Olsen, USA), inner and outer crowns were connected under 5kgf, invested into clear resin blocκ half sectioned along the long axis of specimens and examined under light microscope. Results: Under the conditions of this study, the following conclusions were drawn: 1. The fitness between inner and outer crown using lost-wax technique was the poorest. Multiple casting porosity were observed at inside of the outer crown. 2. The inner and outer crown using cast-on technique were fused together. It is very difficult to find gap between the crowns and to remove inner crown from outer crown. 3. The electroformed outer crown was fabricated directly on the inner crown by using electroforming machine and showed very precise, even space between inner and outer crown. Conclusion: Under the conditions of this study, the electroforming system was the best method for the fabrication of outer crown of double crown retained RPD.

THE COMPARISON OF INITIAL RETENTIVE FORCE IN DIFFERENT DOUBLE CROWN SYSTEMS

Kwon, Ho-Beom,Roh, Yoon-Ho,Lee, Seok-Hyung The Korean Academy of Prosthodonitics 2006 대한치과보철학회지 Vol.44 No.6

Statement of problem. Various double crown systems have been used with removable partial dentures in the clinical field. Although retentive force between inner and outer crown are affected by several factors, differences between the retentive forces of different double crown system types are expected. Purpose. The purpose of this study was to evaluate the initial retentive force of outer crowns fabricated by the conventional casting technique in conus and hybrid double crowns. Material and methods. Ten double crowns were fabricated. The groups were as follows. Group 1, double crowns of hybrid inner and outer crowns using the conventional casting method; Group 2, double crowns of conus inner and outer crowns using the conventional casting method. Tensile strengths of double crowns when the inner and outer crowns were separated on a universal testing machine were measured. These values of retentive force were then statistically analyzed using the Kruskal-Wallis test. Results. Retentive force in group 2 was significantly higher than that in group 1(p<.05). Conclusion. The initial retentive forces of double crowns were affected by the types of the double crown system.

유구치 인접면 우식증 수복 시 지르코니아 전장관과 기성금속관의 생존율 비교 평가: 후향적 연구

정가희,이난영,신혜원,박수현,지명관 대한소아치과학회 2023 大韓小兒齒科學會誌 Vol.50 No.3

Due to increasing demand for aesthetics, zirconia crowns have become a popular choice for treating primary molars. However, there is limited literature available comparing the survival rates of zirconia crowns with those of other restorative materials. The objective of this study was to compare the 36-month survival rates of zirconia crowns and stainless steel crowns for proximal caries, as well as to analyze failure types associated with each crown type. Electronic medical records and radiographs of 1,061 primary molars from 498 patients treated with 2 types of prefabricated crowns at Chosun University Dental Hospital and 2 private dental clinics between 2017 and 2019 were collected and analyzed. The survival rate of zirconia crowns was found to be lower compared to that of stainless steel crowns. Regarding the groups without pulp treatment, the survival rate of stainless steel crowns was significantly higher than that of zirconia crowns. However, in the groups that received pulp therapy, no significant difference in the survival rates was observed between the two preformed crowns. Notably, abnormal root resorption or periapical lesions were identified as the primary cause of restorative failure in stainless steel crowns, whereas loss of restoration was the predominant cause in zirconia crowns. This study holds valuable implications for clinicians when selecting preformed crowns for primary molars.

新羅冠의 양식변화와 자립화 시기 신라정치- 황남대총남분 출토 신라관들을 중심으로 -

김정희 동국대학교 WISE(와이즈)캠퍼스 신라문화연구소 2019 新羅文化 Vol.54 No.-

Silla crowns underwent a changing process in a couple of stage until the standard form of its golden crowns with three right-angled branch types and two antler types. The early crowns of Silla made a start with no standardized style and used the Goguryeo style common to them. Many gilt-bronze crowns in the branch type that had the same form as the early crowns were excavated at the Hwangnam Daechongnam Tombs, which indicates that Silla crowns had become increasingly standardized. This study focused on changes to Silla crowns and politics before their standard, golden crowns. The study thus began by asking a question about the internal and external driving force behind changes to Silla crowns at the stage of the Hwangnam Daechongnam Tombs, which were the first important junction in the standardization process of its crowns. The investigator focused on changes to Silla's relations with Goguryeo and the reinforcement of the Kim family's royal power as the biggest driving force that affected the society and politics of Silla those days and examined Silla crowns and politics. The individual buried in the Hwangnam Daechongnam Tombs was assumed to be Nulji Maripgan according to the estimation of years based on the gold craftwork excavated at the tombs and the excavation patterns of Silla crowns. In turn, the study examined the effects of Silla politics during the era of Nulji Maripgan, which was characterized by the self-reliance policy and the reinforcement of the Kim family's royal power, on changes to Silla crowns at the tombs. Of Silla crowns excavated at the tombs, the feather-type ones, which were the earliest form of them, were under the influence of Goguryeo and reflect the political situation under the powerful influence of Goguryeo in the early days of Nulji Maripgan. Early Silla crowns excavated locally also show the strong influence of Goguryeo. Later, the Goguryeo style disappeared with the appearance of the branch-type crowns that could be called the Silla style, which is supported by the local excavation patterns. These findings indicate that Nulji Maripgan's efforts and determination to pursue self-reliance from Goguryeo led to the creation of golden crowns in the Silla style. They also reflect his political efforts to control local areas and make them his supportive base by giving golden crowns in the Silla style to local heads as prestige goods. When the appearance of right-angled branch-type crowns of Silla is understood in the same context as the Sujeupgisa of Nulji Maripgan's tomb, they can be seen as part of his efforts to integrate the groups of the Kim clan and establish the sacredness of the Kim family's royal power. It is thus likely that the myth of the Kim family as the founder was embodied in the icons of three branch-type crowns of Silla. Finally, the crowns in a primitive form with the addition of an antler element can be estimated to be in the transitional period right before the golden crowns at the Hwangnam Daechongnam Tombs, but there is a question about whether this particular fragment means only an antler. The present study shows that the changing patterns of Silla crowns in the early days of Maripgans reflect fully the changing relations of Silla with Goguryeo and the Kim family's strong determination to establish its royal power and offers some inspirations about the following creation of Silla golden crowns and their political functions.

Hybrid-Ceramic Crown과 금속 도재관의 파절강도 비교

구철회,양홍서,Ku Chul-Whoi,Yang Hong-So 대한치과보철학회 2001 대한치과보철학회지 Vol.39 No.1

The purpose of this study was to compare the fracture strengths and the fracture patterns of several hybrid-ceramic crowns and metal-ceramic crown. Ten crowns were constructed for each group according to the manufacturer's instruction. Removable template of silicone rubber impression material was used for standardization of each crowns. Each crown was cemented on a metal die with hybrid glass ionomer cement. All crowns cemented were stored in distilled water, $36^{\circ}C$ for 24 hours prior to loading in an universal testing machine. The load was directed at 130 degrees the long axis of metal die. The fracture strengths were measured and the fracture patterns were observed. The following results were obtained from this study 1. The mean fracture strengths of $Artglass^{(R)}$, $Sculpture^{(R)}$ and $Targis^{(R)}$ were $57.5{\pm}9.5Kgf,\;62.7{\pm}12.2Kgf$ and $60.2{\pm}10.1Kgf$ respectively. There was no significant difference among each hybrid ceramic crown group. 2. The toad required to fracture hybrid-ceramic crowns was significantly smaller than metal-ceramic crowns($131.7{\pm}22.0Kgf$). 3. In the metal-ceramic crowns, labial porcelain detached partially from porcelain-metal junction of proximal side by load. 4. Hybrid-ceramic crowns showed a simple fracture pattern that fracture line began at the loading area and extended through proximal surface, perpendicular to the margin. The crown was separated into two parts of labial side and lingual side. Above results revealed that three kinds of the hybrid-ceramic crowns used in this study must have careful application in clinical use since the strength of hybrid-ceramic crown was lower(about 1/2) than that of metal-ceramic crown.

Ceramic molar crown reproducibility by digital workflow manufacturing: An in vitro study

정일도,김웅철,박진영,김총명,김지환 대한치과보철학회 2017 The Journal of Advanced Prosthodontics Vol.9 No.4

PURPOSE. This in vitro study aimed to analyze and compare the reproducibility of zirconia and lithium disilicate crowns manufactured by digital workflow. MATERIALS AND METHODS. A typodont model with a prepped upper first molar was set in a phantom head, and a digital impression was obtained with a video intraoral scanner (CEREC Omnicam; Sirona GmbH), from which a single crown was designed and manufactured with CAD/CAM into a zirconia crown and lithium disilicate crown (n=12). Reproducibility of each crown was quantitatively retrieved by superimposing the digitized data of the crown in 3D inspection software, and differences were graphically mapped in color. Areas with large differences were analyzed with digital microscopy. Mean quadratic deviations (RMS) quantitatively obtained from each ceramic group were statistically analyzed with Student’s t-test (α=.05). RESULTS. The RMS value of lithium disilicate crown was 29.2 (4.1) µm and 17.6 (5.5) µm on the outer and inner surfaces, respectively, whereas these values were 18.6 (2.0) µm and 20.6 (5.1) µm for the zirconia crown. Reproducibility of zirconia and lithium disilicate crowns had a statistically significant difference only on the outer surface (P<.001). The outer surface of lithium disilicate crown showed over-contouring on the buccal surface and under-contouring on the inner occlusal surface. The outer surface of zirconia crown showed both over- and under-contouring on the buccal surface, and the inner surface showed under-contouring in the marginal areas. CONCLUSION. Restoration manufacturing by digital workflow will enhance the reproducibility of zirconia single crowns more than that of lithium disilicate single crowns.