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KMID : 0362120190410020063
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Journal of Technologic Dentistry
2019 Volume.41 No. 2 p.63 ~ p.69
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Effect of milling tool wear on the internal fit of PMMA implant interim prosthesis
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Shin Mi-Sun
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Abstract
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Purpose: The purpose of this study is to evaluate the effect of CAD/CAM system milling tool wear on the marginal and internal fit of PMMA implant interim prosthesis three-dimensional manner.
Methods: A total of 20 crowns were fabricated with CAD/CAM method. Their designs were unified to first molar of the left maxilla. The Customized abutments were prepared and scanned with on optical model scanner. Five crowns were milled by the newly replaced tool (1st milling), and 15 crowns were milled by 2nd, 3rd, 4th milling tool. The marginal and internal fit of 20 interim crowns were measured using the triple-scan protocol.
Results: Statistically significant difference was found between the 1st milling group (51.8±14.6μm) and the 3rd, 4th milling group (128.6±43.8μm, 146.2±38.1μm, respectively) at the distal margins. In the mesial margins, There was a statistically significant difference between the 1st milling group (63.6±25.9μm) and the 3rd, 4th milling group (137.2±25.9μm, 186.8±70.6μm, respectively). In the distal line angle, significant difference was found between the 1st, 2nd, 3rd milling groups and the 4th milling group. In the mesial axial wall, significant difference was found between the 1st milling group (52.2±20.3μm) and the 3rd, 4th milling groups (22.8±8.8μm, 7.8±5.7μm).
Conclusion: As a result of the experiment, decrease of the marginal and internal fit was statistically significant as the number of machining cycles increased. In order to produce clinically excellent restorations, it is recommandable to consider the condition of the milling tool wear, when designing the restoration with CAD program.
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KEYWORD
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CAD/CAM, triple-scan protocol, milling tool, PMMA implant interim prosthesis
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