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AN EXPERIMENTAL STUDY ON THE CERVICAL MARGIN FITNESS IN THE COLLARLESS METAL CERAMIC CROWNS FORMED BY DIFFERENT TECHNIQUES (Collarless도재소부전장금관의 제작방법에 따른 치경부 변연적합도에 관한 실험적 연구)

  • Lee, Jae-Hyeuk
    • The Journal of Korean Academy of Prosthodontics
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    • v.28 no.1
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    • pp.203-216
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    • 1990
  • The purpose of this study was to evaluate the cervical margin fitness in the collarless metal ceramic crowns formed by different techniques. Specimens were divided as follows : the metal ceramic crowns with metal butt margin as group I, the collarless metal ceramic crowns formed with resin binder technique as group II, and the collarless metal ceramic crowns formed with shoulder powder mixed with phosphate-bonded investment liquids on a refractory die as group III. Each group was made of five specimens, and their marginal fitness on each epoxy die was evaluated under scanning electron microscope of x200 magnification at three measuring points : mesial, central, distal. The following results were obtained. 1. The metal ceramic crowns with metal butt margin exhibited significantly better marginal fitness than the collarless metal ceramic crowns. The marginal fitness in descending order was group I, III, II. 2. The collarless metal ceramic crown formed with resin binder technique had the worst marginal fitness & showed cervical color variation and dermacation between the corrected porcelain & the dentin porcelain. 3. The collarless metal ceramic crowns formed with shoulder powder mixed with phosphate-bonded investment liquids on a refractory die exhibited significantly better marginal fitness & sharper marginal configuration than the other collarless group.

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A STUDY OF THE SHEAR BOND STRENGTH OF METAL BRACKETS AND CERAMIC BRACKETS AND THE CONDITION AFTER DEBONDING (Metal bracket과 ceramic bracket의 전단 결합 강도와 debonding 상태에 관한 연구)

  • Yoon, Jung-Jin;Ryu, Young-Kyu
    • The korean journal of orthodontics
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    • v.22 no.2 s.37
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    • pp.327-343
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    • 1992
  • Metal brackets and ceramic brackets were bonded to natural teeth, porcelain crowns and gold crowns After stored in artificial saliva solution for 72 hours at $37^{\circ}C$, the shear bond strengths were measured by Instron and compared with them, the bonding sites and bracket bases were examined by scanning electron microscope and light optical stereomicroscope. The results were as follows: 1. The shear bond strengths of the group which metal brackets were bonded to natural teeth and the groups which ceramic brackets were bonded to natural teeth and porcelain crowns were comparable to each other, the shear bond strength of the group which metal brackets were bonded to gold crowns was significantly low. 2. The bond failed predominantly at the bracket base/adhesive interface with the bulk of adhesive remaining on enamel in the group which metal brackets were bonded to natural teeth. 3. The bond failed consistently at the crown/adhesive interface with all of adhesive remaining on the bracket babes in the group which metal brackets were bonded to gold crowns. 4. The bond failed at the enamel or crown/adhesive interface with the bulk of adhesive remaining on the bracket bases in the groups which cramic brackets were bonded to natural teeth and porcelain crowns. 5. The shear bond strengths of the groups which ceramic brackets were bonded to porcelain crowns were not affected by etching time.

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IN VITRO MARGINAL FIT OF THE COMPUTERAIDED MILLED CERCON CROWNS

  • Chang, Jae-Yoon;Yang, Jae-Ho;Han, Jung-Suk;Lee, Jai-Bong
    • The Journal of Korean Academy of Prosthodontics
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    • v.43 no.3
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    • pp.306-313
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    • 2005
  • Statement of problem. There have been many studies about marginal discrepancy of single restorations made by various systems and materials. But most of statistical inferences are not definite because of sample size, measurement number, measuring , instruments, etc. And there have been few studies about the marginal fit of Computer-aided Cercon crowns. Purpose. The purpose of this study was to compare the marginal fit of the anterior single restorations made using computer-aided milled Cercon crowns with metal-ceramic restorations and to obtain more accurate information by using a large enough sample size and by making sufficient measurements per specimen. Material and methods. The in vitro marginal discrepancies of computer-aided milled Cercon crowns and control groups (metal ceramic crowns) were evaluated and compared. The crowns were made from one extracted maxillary central incisor prepared by milling machine. 30 crowns per each system were fabricated. Measurements of a crown were recorded at 50 points that were randomly selected for marginal gap evaluation. Parametric statistical analysis was performed for the results. Results. The means and standard deviations of the marginal fit were 85$\pm$22$\mu$m for the control group and 91$\pm$15$\mu$m for the Cercon crowns. The t-test of the marginal discrepancies between Cercon crowns and metal-ceramic crowns were performed. Significant differences were not found between groups (P=0.230>.05). Based on the criterion of 120$\mu$m as the limit of clinical acceptability, the mean marginal fits of Cercon crowns and metal-ceramic crowns were acceptable. Conclusion. Within the limitations of this in vitro study, the following conclusions were drawn: 1. Mean gap dimensions and standard deviations at the marginal opening for maxillary incisal crowns were 85$\pm$22$\mu$m for the control (metal-ceramic crowns), 91$\pm$15$\mu$m for Cercon crowns. 2. The Cercon crowns showed slightly larger marginal gap discrepancy than the control but marginal gap between Computer-aided milled Cercon crowns and metal ceramic crowns did not showed significant difference (P>.05). 3. The Cercon crowns and metal ceramic crowns showed clinically acceptable marginal discrepancy.

A Study on How Cyclic Casting of Base Metal Alloy for Dental Ceramic Crown May Effects upon Its Mechanical Properties and Microstructure (치과 도재용착 주조관용 비귀금속 합금의 반복주조가 기계적 특성 및 미세조직에 미치는 영향)

  • Choi, Un-Jae;Shin, Moo-Hak;Chung, Hee-Sun;Koh, Myoung-Won
    • 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.

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A STUDY ON THE FRACTURE STRENGTH OF THE IPS-EMPRESS CERAMIC CROWN ACCORDING TO MARGIN TYPE (IPS-Empress 도재관의 변연형태에 따른 파절강도에 관한 연구)

  • Kim, Hyun-Soo;Ju, Tae-Hun;Oh, Sang-Chun;Dong, Jin-Keun
    • The Journal of Korean Academy of Prosthodontics
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    • v.35 no.2
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    • pp.296-307
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    • 1997
  • The purpose of this study was to compare the fracture strength of the IPS-Empress ceramic crown according to margin types such as bevel, shoulder, rounded shoulder, shoulder with bevel, rounded shoulder with bevel and bevel with groove. After 10 metal dies were constructed for each group, the IPS-Empress ceramic crown were fabricated and each crown was cemented on each metal die with Bistite resin cement. The cemented crowns mounted in the testing jig were inclined 30 degree and universal testing machine (Zwick 1456 41, Zwick Co., Germany) was used to measure the fracture strength. The obtained results were as follows : 1. The fracture strength of the crown with rounded shoulder was the highest of all. The mean fracture strength was 484N in rounded shoulder, 357N in bevel, 341N in rounded shoulder with bevl, 300N in shoulder with bevel, 280N in shoulder and 275N in bevel with groove. 2. The fracture strength of rounded shoulder was statistically different from those of shoulder with bevel, shoulder and beve41 with groove. 3. In the strain at fracture, there was no significant difference among each group. 4. The fracture mode of the crown was similar and most of fracture line began at the loading area and extended through proximal surface perpendicularly to the margin, irrespective of margin type.

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Fracture strength of zirconia ceramic crowns according to tooth position (치아 부위에 따른 지르코니아 도재관의 파절강도)

  • Lee, In-Seob;Kim, Jeong-Mi;Dong, Jin-Keun
    • The Journal of Korean Academy of Prosthodontics
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    • v.48 no.2
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    • pp.94-100
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    • 2010
  • Purpose: The purpose of this study was to compare the fracture strength of the zirconia ceramic crowns according to tooth position. Material and methods: After 10 metal dies were made for each group, the zirconia ceramic crowns were fabricated using CAD/CAM system ($Lava^{TM}$ All-Ceramic System) and each crown was cemented on each metal die with resin cement (Rely $X^{TM}$ Unicem). The cemented zirconia ceramic crowns mounted on the testing jig were inclined with 30 degrees to the long axis of the tooth and the universal testing machine was used to measure the fracture strength. Results: 1. The fracture strength of the zirconia ceramic crown in the lower 1st molar (2963 N) had the highest and that in the lower central incisor (1035 N) had the lowest. 2. The fracture strength of zirconia ceramic crown was higher than that of the IPS Empress crowns in all tooth position. 3. The fracture mode of the crowns was similar. Most of fracture lines began at the loading area and extended through proximal surface perpendicular to the long axis of the crowns. 4. There were no significant differences on the fracture strength of the zirconia ceramic crowns according to tooth position except in premolar group. Conclusion: Within the limitations of this study, the results suggested that strength of zirconia ceramic crown is satisfactory for clinical use.

A 2-year clinical evaluation of Sculpture crowns

  • Ku, Chul-Whoi;Yang, Hong-So
    • The Journal of Korean Academy of Prosthodontics
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    • v.38 no.6
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    • pp.806-813
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    • 2000
  • Statement of problems. There are only a few studies available that deal with the clinical behavior of ceromer systems as potential substitutes for metal-ceramic crowns. Purpose. This prospective study was initiated to evaluate the clinical performance of 35 Sculpture crowns after 2 years in service. Material and methods. Thirty five Sculpture crowns were placed for 20 patients (7 men and 13 women). All patients were treated by the same dentist, and all restorations were fabricated by the same dental laboratory. Crown placement involved both the anterior and posterior regions of the dental arches. Patients were evaluated by two examiner at baseline, 12, and 24 months using the CDA quality assessment system in addition to periodontal criteria. Results. Of 34 crowns remaining in the study after 2 years, only one crown had experienced a marginal fracture. The crown was replaced as a result of recurrent caries. All remaining crowns were ranked as either excellent or acceptable for surface and color, anatomic form, and marginal integrity. Conclusion. The 2-year clinical observations and ranking with the CDA quality assessment criteria supported the conclusion that Sculpture crowns may be used in substitutes for metal-ceramic crowns.

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THE FRACTURE RESISTANCE AND STRESS DISTRIBUTION OF ALL CERAMIC CROWNS WITH TWO TYPES OF FINISH LINE ON MAXILLARY CENTRAL INCISOR (상악중절치에서 전부도재관의 finish line형태에 따른 파절강도와 응력 분포에 관한 연구)

  • Ki Tae-Seok;Kim Kyea-Soon;Lee Jin-Han;Kim Yu-Lee;Dong Jin-Keun
    • The Journal of Korean Academy of Prosthodontics
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    • v.41 no.4
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    • pp.405-420
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    • 2003
  • Purpose : The purpose of this study was to compare the fracture resistance of the IPS Empress ceramic crown with 1.0mm width rounded shoulder, which is usually recommended in all ceramic crown. and 0.5mm width chamfer finish lines on the maxillary central incisor. Material and method : After 15 metal dies were made for each group, the IPS Empress all ceramic crowns were fabricated and cemented with resin cement(Bistite resin cement, Tokuyama Soda Co. LTD., Japan) on the metal die. The cemented crowns were mounted on the positioning jig and the universal testing machine(Zwick Z020, Zwick Co. Germany)was used to measure the fracture strength with loading on the incisal edge. And also, three-dimensional finite element stress analysis was used to measure the stress distribution with the various types of the finish lines(1.0mm width rounded shoulder, 0.5mm width chamfer), the loading site(incisal edge, incisal $\frac{1}{3}$) and the type of loading(concentration loading, distribution loading). Results and conclusion : 1. In the fracture resistance experiment according to the finish line, the mean fracture strength of rounded shoulder(876N) and the mean fracture strength of chamfer(882N) did not skew any significant difference between each other(p>0.05). 2. The stress distribution of all ceramic crown in three dimensional finite element analysis showed concentration aspect at loading point and cervical area or labial surface. 3. In metal die, there were no differences in stress distribution between finish lines, but in natural teeth model, chamfer finish line showed higher stress than rounded shoulder finish line. 4. When force was loaded on the incisal edge the stress was concentrated on the incisal edge and the cervical area of labial surface. When force was loaded on the incisal $\frac{1}{3}$, the stress concentrated on the cervical area of labial surface and the cingulum area. 5. Generally, natural teeth model showed higher and various stress than the metal die.