Impact of surface roughness of gypsum materials on adaptation of zirconia cores

PURPOSE: The present study investigated the influences of various gypsum materials on the precision of fit of CAD/CAM-fabricated prostheses and analyzed their correlation with surface roughness. MATERIALS AND METHODS: The master model of the mandibular right first molar was replicated, and four experimental groups based on two types of Type IV stone (GC Fujirock EP, Die keen) and two types of scannable stone (Aesthetic-Basegold, Everest Rock) were created to include a total of 40 specimens, 10 in each group. The surface roughness of the working models for the respective experimental groups was measured. Once the zirconia cores had been fabricated, the marginal and internal fits were measured with a digital microscope using the silicone replica technique. The mean and standard deviation of the respective points of measurement were computed and analyzed through the one-way ANOVA and Tukey's HSD test. The correlation between surface roughness and the precision of fit of the zirconia core was analyzed using the Pearson correlation analysis (alpha=.05). RESULTS: The zirconia cores fabricated from the scannable stone working models exhibited a superior precision of fit as compared to those fabricated from the Type IV stone working models. The correlation analysis results showed a clear positive correlation between surface roughness and the precision of fit of zirconia cores in all of the experimental groups (P<.05). CONCLUSION: The results confirmed that the surface roughness of dental working models has a decisive influence on the precision of fit of zirconia cores.

Marginal and internal fitness of three-unit zirconia cores fabricated using several CAD/CAM systems / 대한치과보철학회지

PURPOSE: This study was aimed to compare the margin and internal fitness of 3-unit zirconia bridge cores fabricated by several CAD/CAM systems using replica technique. MATERIALS AND METHODS: Three unit-bridge models in which upper canine and upper second premolar were used as abutments and upper first premolar was missed, were fabricated. Fourty models were classified into 4 groups (Cerasys(R) (Group C), Dentaim(R) (Group D), KaVo Everest(R) (Group K), Lava(TM)(Group L)), and zirconia cores were fabricated by each company. Sixteen points were measured on each abutment by replica technique. Statistical analysis was accomplished with two way ANOVA and Dunnett T3 (alpha=.05). RESULTS: In most systems, there was a larger gap on inter margin than outer margin. In the Group K, overall fitness was excellent, but the incisal gap was very large. In the Group C, marginal gap was significantly larger than Group K, but overall internal gap was uniform (P<.05). The axial gap was under 100 microm in all system. The difference between internal and external gap was small on Group L and C. However, internal gap was significantly larger than external gap in Group D (P<.05). The fitness of canine was better than second premolar among abutments (P<.05). CONCLUSION: The marginal and internal gap was within the clinically allowed range in all of the three systems. There was a larger gap on second premolar than canine on internal and marginal surface. In most systems, there was a larger gap on occlusal surface than axial surface.

Evaluation using Replica Technique on the marginal and internal fitness of zirconia cores by several CAD/CAM systems / 대한치과보철학회지

PURPOSE: This study was aimed to compare the margin and internal fitness of single anterior all-ceramic crown zirconia core made by three deferent CAD/CAM systems. MATERIAL AND METHODS: Five single zirconia cores were manufactured by three deferent CAD/CAM systems(Cerasys(R)system, KaVo Everest(R)system, Lava(TM) system). The manufactured zirconia cores were duplicated through the use of replica technique, and a replicated sample was sectioned in the center of bucolingual and mesiodistal direction to measure the marginal and internal gap. Measurement was carried out by using measuring microscope (AXIO(R)) and I-Solution(R) and analysed through the use of ANOVA. RESULTS: As for the mean marginal fitness of the zirconia core, it was 84.74 +/- 27.57 micrometer, in Cerasys(R), 80.23 +/- 21.07 micrometer in KaVo Everest(R) and 96.37 +/- 11.45 micrometer in Lava(TM), and as for the mean internal gap, it was 94.11 +/- 30.07 micrometer in Cerasys(R), 92.31 +/- 25.18 micrometer in KaVo Everest(R), and 94.99 +/- 18.74 micrometer in Lava(TM). There was no significant statistically deference among the total average gap of three systems. The internal gap in KaVo Everest(R) seemed to be smaller than Lava(TM) (P < .05). The internal gap in the incisal area was larger in all of the three systems. CONCLUSION: There was no difference in marginal fitness in Cerasys(R), KaVo Everest(R) and Lava(TM). As for the internal fitness, it was smaller in KaVo Everest(R) system than Lava(TM)system. In all of the three systems, there was a larger gap in incisal area. The marginal and internal gap was within the clinically allowed range in all of the three systems.

Spectrophotometric analysis of the influence to shade of zirconia core on the color of ceramic / 대한치과보철학회지

STATEMENT OF PROBLEM: At all times people have tried to fabricate tooth restorations using tooth colored materials. Recently, demands for esthetics, even in restorations requiring strength, has brought a revolution to dentistry and increased use of zirconia. The basic color of zirconia is white to ivory. The color can be partially adapted by veneering it with ceramic materials. However, it would be better if the substructure could already be adapted to the basic color shade of neighboring teeth. By adaptation to the basic shade, it can help to reduce the necessary layer thickness of the veneer ceramic to achieve the desired color. PURPOSE: The purpose of this study was to spectrophotometrically evaluate the influence of shading of zirconia core on the final shade of all-ceramic restorations using the CIE L*a*b* system. MATERIAL AND METHODS: Core specimens (n = 20 per group) of Lava Frame Zirconia, KaVo Everest Zirconia, Digident CAD/CAM Zirconia were fabricated at 20 mm in diameter and 0.5 mm in thickness. Halves of each groups were shaded in A3 color. These core specimens were veneered with A3 porcelain of the recommended manufacturer at thickness of 0.5 mm. CIE L*a*b* coordinates were recorded for each specimen with a spectrophotometer (Model CM-2600d, Minolta, Japan) at 0.5 mm, 0.4 mm, 0.3 mm in thickness. Color differences were calculated using the equation deltaE* = [(deltaL*)2+(deltaa*)2+(deltab*)2]1/2. RESULTS: 1. In the case where porcelain layer has a thickness of 0.5 mm, Lava Frame Zirconia and KaVo Everest group did not show clinically perceived color difference, however Digident CAD/CAM Zirconia group showed clinically perceived color difference according to shade allowed on core. 2. When the thickness of porcelain layer decreased from 0.5 mm to 0.4 mm, Lava Frame Zirconia and KaVo Everest group did not show clinically perceived color difference, on the other hand Digident CAD/CAM Zirconia group showed clinically perceived color difference according to shade allowed on core. 3. When the thickness of porcelain layer decreased from 0.5 mm to 0.3 mm, clinically perceived color differences were observed from all three groups. CONCLUSIONS: Ziroconia system, which is possible to allow shade on core, are thought to be much more favorable to reproduce natural shade compared to systems that is impossible to give shade. Therefore, clinicians ought to choose adequate system for certain clinical situation by considering above specific character.

Comparative study in marginal adaptation of zirconia cores fabricated with 3 different CAD/CAM systems / 대한치과보철학회지

STATEMENT OF PROBLEM: There have been many studies about marginal adaptation of Zirconia core fabricated with various CAD/CAM systems. But, the comparative study has not been conducted much. PURPOSE: This study was to compare marginal adaptations of zirconia cores fabricated with 3 different CAD/CAM systems. MATERIAL AND METHODS: The in vitro marginal adaptations of zirconia cores fabricated with 3 different CAD/CAM systems(Adens(R) system, Lava(R) system, and Cerasys(R) system) were evaluated and compared. In this study 30 zirconia cores were fabricated(10 zirconia cores per each system). The measurements of the marginal adaptatioin were carried out using microscope L-150A(R)(Nikon, Japan). Measurements were recorded at 50 points. The measurements were analyzed using Kruskal-Wallis test and Wilcoxon rank sum test. RESULTS: Within the limits of this study, the results were as follows. 1. Mean marginal gap values obtained were 284.5+/-152.9 micrometer in Adens(R) system, 99.0+/-73.0 micrometer in Lava(R) system, and 153.5+/-85.7 micrometer in Cerasys(R) system. 2. Zirconia core made by Lava(R) system showed the smallest marginal gap(P<0.05). CONCLUSION: In the limitation of this study, we concluded that Lava(R) System was superior than other systems(Adens(R) system and Cerasys(R) system) in the marginal adaptation.

Comparative study in fracture strength of zirconia cores fabricated with three different CAD/CAM systems / 대한치과보철학회지

PURPOSE: The purpose of this study is to compare three different CAD/CAM systems through the fracture strength of zirconia core and to evaluate the clinical availability of each system. MATERIAL AND METHODS: The following three groups of 30 maxillary mesial incisor core for all-ceramics(each group 10) were fabricated as follows: group 1. Adens(R) CAD/CAM system, group 2. Cerasys(R) CAD/CAM system, group 3. 3M LAVA(R)CAD/CAM system. All specimens were manufactured consistently thickness 0.5mm and relief 40 micrometer. Specimens were subjected to compressive loading on the lingual area by Z250/SN5S(R). Each group's mean and standard deviation were calculated and Kruskal Waillis test, Wilcoxon Rank Sum test were utilized to find out the relationship among the groups. RESULTS: The results were as follows: 1. The mean fracture strength of Adens(R) system was 615.89+/-156.1N, the Cerasys(R) system was 863.98+/-151.5N, and the 3M LAVA(R) system was 1143.1+/-286.6N. 2. The fracture strength of the systems showed the significant statistical differences in order of 3M LAVA(R) system, Cerasys(R) system, Adens(R) system. CONCLUSION: In this study, in spite of the differences among the groups, every group showed clinically useful results. It is necessary to study further clinical experiments on a long term basis.

Spectrophotometric analysis of the influence of zirconia core on the color of ceramic / 대한치과보철학회지

STATEMENT OF PROBLEM: Problem of matching the appearance of porcelain restorations with the patient's natural dentition has always been a concern to dental clinicians. Recently, demands for esthetics, even in restorations requiring strength, has brought a revolution to dentistry and increased use of zirconia. Among the various factors, shade and translucency of the core can significantly affect the overall esthetics of the restoration and should be considered when selecting an all-ceramic system. PURPOSE: The purpose of this study was to spectrophotometrically evaluate the influence of different zirconia systems and core thickness on the final shade of all-ceramic restorations using the CIEL*a*b* system. MATERIAL AND METHODS: Core specimens (n = 20 per group) of In-Ceram Alumina, In-Ceram Zirconia, Digident CAD/CAM Zirconia, Cercon Zirconia were fabricated 20mm in diameter. 10 specimens of each group were fabricated at core thickness of 0.5mm and 0.7mm. These core specimens were veneered with shade A1 and A3 porcelain of the recommended manufacturer. CIEL*a*b* coordinates were recorded for each specimen with a spectrophotometer (Model CM-2600d, Minolta, Japan). Color differences were calculated using the equation delta E*=[(delta L*)2+(delta a*)2+(delta b*)2]1/2. RESULTS: 1. Specimens of core thickness 0.5mm and 0.7mm did not exhibit clinically perceived color difference. 2. Regarding shade reproducibility, In-Ceram Alumina and In-Ceram Zirconia showed significant difference within each group. 3. Cercon Zirconia group showed the highest L* value and Digident Zirconia group showed lowest a* and b* value. 4. Generally, the shade difference between materials was higher in the A3 shade group than in the A1 shade group. CONCLUSION: Within the limitations of this study, there was no color difference after increase in core thickness and every all-ceramic system has color characteristics that clinicians have to consider when selecting materials. Also, manufacturers of different porcelain systems must make every effort to achieve color reproducibility.