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This study aims to measure the trueness of zirconia crowns with different build directions of materials fabricated using the stereolithography (SLA) method. The anatomic contour crown of prepped maxillary right first molar was designed using CAD software to obtain the standard tessellation language (STL) file. Two different build directions were set for the crowns using Materialize Magics software. One group was built with a margin base platform, while the other group was built in the direction opposite to the occlusal surface base platform. The 20 crown-shaped parts were printed. The STL files of scanned printing zirconia crowns were superimposed each segment by the 3D analysis software. The two groups were statistically analyzed using t-tests. Significant differences were found in the marginal and internal discrepancies between the groups. The build direction had a significant influence on the accuracy of the zirconia crown. The results indicate the most effective build direction for manufacturing SLA 3D-printed crowns. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the digitization of alginate impressions by analyzing differences between the scan data of two types of impressions (alginate and rubber) taken from the master die and the scan data for the master die. The master die and impressions were digitized using a dental laser scanner (7 series, Dental Wings, Montreal, Canada). The crown portion of the abutment teeth in the digital data of 20 impressions was divided into three regions: cervical surface, middle surface, and occlusal surface. An independent t-test showed a significant difference (p<0.05) in the mean difference for each experimental group (alginate and rubber). One-way ANOVA and Tukey's honest significant difference test revealed a significant difference (p<0.05) among the three regions in the rubber impression. The results of this study also carefully suggest the possibility of digitization of alginate impressions in the future. [ABSTRACT FROM AUTHOR]

In this study, we evaluated the repeatability of scans of stone models and impressions of abutment teeth using a blue LED scanner and compared the findings between different abutment teeth types. For the stone models as well as impression of the canines, premolars, and molars, we generated 10 color-difference-maps and reports for each tooth type (n=10 per tooth type). One-way analysis of variance (ANOVA) and independent f-tests were performed to evaluate the repeatability of scans of the stone models and impressions obtained from a blue LED scanner. Our results indicate a high repeatability of scans of stone models and impressions of abutment teeth using the blue LED scanner and suggest a possible clinical advantage for scanning impressions of different abutment teeth types. [ABSTRACT FROM AUTHOR]

The clinical applicability of CAD/CAM-fabricated zirconia copings is tested using working models made from four different highstrength Type IV gypsum materials. Each of the four materials was used tofabricate 15 zirconia copings. Precision of fit was measured with a digital electron microscope using the silicone replica technique. The mean and standard deviation of each reference point were analyzed using the one-way analysis of the variance (ANOVA) and Tukey's honest significant difference (HSD) tests (a=0.05). The overall marginal and internal fits of the zirconia copings were as follows: GS (GS: Grey Stone) group: 91.43 pm, LS (LS: Light green Stone) Group: 87.89 pm, RS (RS: Red Stone) Group: 88.75 pm, BS (BS: Beige Stone) Group: 82.78 pm. There were no significant differences between the mean adaptations of the gypsum varieties (p>0.05). This confirmed that the type of gypsum material used does not determine the precision of fit of a prosthesis. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate, by measuring the gap, the possible clinical use of three-unit fixed dental prostheses (FDPs) manufactured using stereolithography. A total of 20 epoxy models were built with a same case (abutment teeth 14, 16). The 40 specimens were produced using the stereolithography (SLA) and wax-up (LW). The 960 gaps of the 40 specimens produced were measured by a silicone replica. The Wilcoxon rank sum test was then used to compare and analyze the data obtained from the two groups (α=0.05). The total gap, as measured from the SLA and LW groups, was 98.6 and 66.6 pm, respectively. The results indicate that the gap in the SLA group is statistically significantly greater than that in the LW group (p<0.05). Further assessment and improvement of the SLA method for the fabrication of FDPs is evidently still required. [ABSTRACT FROM AUTHOR]