The effects of gingival biotype on the aesthetics of anterior teeth with all ceramic crown / 实用口腔医学杂志

56 teeth in 48 patients were divided into thick gingiva group (28 teeth)and thin gingiva group (28 teeth) and repaired with zirconia ceramic crown.Before 1 and 2 years after repair,gingival index,gingival margin recession and edge color satisfaction were evaluated.1 and 2 years after,repair gingival index was increase in thick group (P ＜ 0.05),but other indices were not (P ＞ 0.05);in thin gingiva group 2 years after repair the gingival margin recession index was increased(P ＜0.05),the other indices were not(P ＞ 0.05).

A comparative study on the fracture behavior of zironia, glass infiltrated alumina and PFM full crown system / 대한치과보철학회지

PURPOSE: The purpose of this study was to compare the fracture behavior of Zironia, glass infiltrated Alumina and PFM full crown system. MATERIALS AND METHODS: Fifteen crowns for each of 3 experimental groups (Zironia, glass infiltrated Alumina and PFM full crown) were made by the conventional method. The crowns mounted on the testing jig were inclined in 30 degrees to the long axis of the tooth and the universal testing machine was used to measure the fracture strength. RESULTS: 1. The mean fracture strengths were 588.3 +/- 49.6 MPa for zirconia system, 569.1 +/- 61.8 MPa for PFM system and 551.0 +/- 76.5 MPa for glass-infiltrated alumina system (P>.05). 2. The mean shear bond strengths were 25.5 +/- 5.6 MPa for zirconia system, 38.9 +/- 5.0 MPa for Ni-Cr alloy system and 39.4 +/- 5.1 MPa for glass-infiltrated alumina system. 3. The chemical bonding was observed at interfaces between PFM or glass-infiltrated alumina and veneering porcelain, however, no chemical bonding was observed at interface between zirconia and veneering porcelain. CONCLUSION: With the study, the fracture strengths of PFM crown system had a higher fracture strength than conventional zirconia system crown and glass-infiltrated alumina crowns. and than the shear bond strengths glass-infiltrated alumina system had a higher shear bond strength than conventional PFM system and zirconia system.

Fracture strength of zirconia ceramic crowns according to tooth position / 대한치과보철학회지

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.

Influence of porcelain veneering on the marginal fit of Digident and Lava CAD/CAM zirconia ceramic crowns

PURPOSE: Marginal fit is a very important factor considering the restoration's long-term success. However, adding porcelain to copings can cause distortion and lead to an inadequate fit which exposes more luting material to the oral environment and causes secondary caries. The purpose of this study was to compare the marginal fit of 2 different all-ceramic crown systems before and after porcelain veneering. This study was also intended to verify the marginal fit of crowns originated from green machining of partially sintered blocks of zirconia (Lava CAD/CAM system) and that of crowns obtained through machining of fully sintered blocks of zirconia (Digident CAD/CAM system). MATERIAL AND METHODS: 20 crowns were made per each system and the marginal fit was evaluated through a light microscope with image processing (Accura 2000) at 50 points that were randomly selected. Each crown was measured twice: the first measurement was done after obtaining a 0.5 mm coping and the second measurement was done after porcelain veneering. The means and standard deviations were calculated and statistical inferences among the 2 groups were made using independent t-test and within the same group through paired t-test. RESULTS: The means and standard deviations of the marginal fit were 61.52 +/- 2.88 micrometer for the Digident CAD/CAM zirconia ceramic crowns before porcelain veneering and 83.15 +/- 3.51 micrometer after porcelain veneering. Lava CAD/CAM zirconia ceramic crowns showed means and standard deviations of 62.22 +/- 1.78 micrometer before porcelain veneering and 82.03 +/- 1.85 micrometer after porcelain veneering. Both groups showed significant differences when analyzing the marginal gaps before and after porcelain veneering within each group. However, no significant differences were found when comparing the marginal gaps of each group before porcelain veneering and after porcelain veneering as well. CONCLUSION: The 2 all-ceramic crown systems showed marginal gaps that were within a reported clinically acceptable range of marginal discrepancy.

Marginal fit of the digident CAD/CAM zirconia ceramic crowns / 대한치과보철학회지

Statement of problem. There have been many studies about marginal discrepancy of single restorations made by various systems and materials. However most of the 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 the Digident CAD/CAM zirconia ceramic crowns. Purpose. The purpose of this study was to compare the marginal fit of the anterior single restorations made by using the Digident CAD/CAM zirconia ceramic 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 crowns were made from one extracted maxillary central incisor prepared with a 1mm shoulder margin and 6.taper walls by milling machine. The in vitro marginal discrepancies of the digident CAD/CAM zirconia ceramic crowns and control groups(metal ceramic crowns) were evaluated and compared. Twenty 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. 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 88+/-10microm for the control (metal-ceramic crowns), 92+/-4microm for Digident CAD/CAM zirconia ceramic crowns. 2. Marginal gap between Digident CAD/CAM zirconia ceramic crowns and metal ceramic crowns did not show significant difference (P>.05). 3. The Digident CAD/CAM zirconia ceramic crowns and metal ceramic crowns showed clinically acceptable marginal discrepancy.