• Conservation Science in Museum
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• v.21
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• pp.41-52
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• 2019

The findings of a 2017 safety inspection of the Three-story Pagoda from the Goseonsa Temple site in Gyeongju suggested the possibility that the stone for the second story of the pagoda may have been rotated after the pagoda was disassembled for removal from its original site in 1975. The materials from the pagoda were investigated using photographs and other relevant data from both the Japanese colonial period and from around 1975. The analysis found that the materials of the pagoda were not changed after analleged reconstruction in 1943, but that during the process of relocating the pagoda in 1975 the body of the second story was indeed rotated counter clockwise by 90 degrees and one of the four stone elements making up the first-story roof was exchanged with a part from the second-story roof. In order to discover whether the materials had been incorrectly placed, each part of the pagoda was precisely measured and the elements of the roofs were virtually reconstructed using 3D scanning data. The investigation did not find any singularities with in the components of each roof; the four part sof the first-story roof were 75 to 76 centimeters thick and those for the second-story roof were 78 to 79 centimeters thick. The connections between each part of the roofs also appeared natural. This seems to indicate that there was indeed an undocumented repair of the pagoda at some point between its creation and 1943 and an error that took place during this repair was corrected in 1975. In addition, the study suggested a possibility that the body of the second story was rotated counter clockwised to a change in the locations of parts of the two roofs.

• The Journal of Korean Academy of Prosthodontics
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• v.48 no.4
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• pp.294-300
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• 2010

Purpose: The template-guided implant surgery offers several advantages over the traditional approach. The purpose of this study was to evaluate the accuracy of coordinate synchronization procedure with 5-axis milling machine for surgical template fabrication by means of reverse engineering through universal CAD software. Materials and methods: The study was performed on ten edentulous models with imbedded gutta percha stoppings which were hidden under silicon gingival form. The platform for synchordination was formed on the bottom side of models and these casts were imaged in Cone beam CT. Vectors of stoppings were extracted and transferred to those of planned implant on virtual planning software. Depth of milling process was set to the level of one half of stoppings and the coordinate of the data was synchronized to the model image. Synchronization of milling coordinate was done by the conversion process for the platform for the synchordination located on the bottom of the model. The models were fixed on the synchordination plate of 5-axis milling machine and drilling was done as the planned vector and depth based on the synchronized data with twist drill of the same diameter as GP stopping. For the 3D rendering and image merging, the impression tray was set on the conbeam CT and pre- and post- CT acquiring was done with the model fixed on the impression body. The accuracy analysis was done with Solidworks (Dassault systems, Concord, USA) by measuring vector of stopping’s top and bottom centers of experimental model through merging and reverse engineering the planned and post-drilling CT image. Correlations among the parameters were tested by means of Pearson correlation coefficient and calculated with SPSS (release 14.0, SPSS Inc. Chicago, USA) ($\alpha$ = 0.05). Results: Due to the declination, GP remnant on upper half of stoppings was observed for every drilled bores. The deviation between planned image and drilled bore that was reverse engineered was 0.31 (0.15 - 0.42) mm at the entrance, 0.36 (0.24 - 0.51) mm at the apex, and angular deviation was 1.62 (0.54 - 2.27)$^{\circ}$. There was positive correlation between the deviation at the entrance and that at the apex (Pearson Correlation Coefficient = 0.904, P = .013). Conclusion: The coordinate synchronization 5-axis milling procedure has adequate accuracy for the production of the guided surgical template.