Description of surface defects and micro-hardness in cobalt chromium structures for dental prostheses made using the CAD-CAM technique
Objective: to describe surface and micro hardness defects in cobalt chromium structures for dental prostheses made using the CAD-CAM technique.
Method: Type of descriptive study. Population and sample: 10 cobalt-chromium alloy frameworks for 3-piece bar-type dental prostheses, dimensions 10 cm x 1.5 cm. The plaster model was obtained from a conventio-nal impression, the model was prepared for scanning and the design of the structure, then the structure was ordered to be milled under the supervision of the project researchers. Subsequently, they were analyzed in the scanning electron microscope and in the Shimadzu Micro Vickers Hardness Tester HMV-G 21 equipment.
Results: through the scanning electron microscopy, images with magnifications of various sizes were obtained where different defects of surface such as surface irregularities, dirt and foreign bodies. The samples milled with three axes are found to have a hardness of 294.6 ± 21 HK0.1 and an elastic modulus of 239 ± 22.3 GPa, while the samples milled with five axes have a hardness of 336.2 ± 20.9 HK0.1 and an elastic modulus of 237.7 ± 18.3 GPa.
Conclusions: through scanning electron microscopy, surface defects were observed that are not visible to the naked eye, such as surface irregularities, unevenness and mainly fatty dirt due to the high carbon content. However, cracks and porosities are not observed. Milling has a slight influence on the hardness, but not on the elastic modulus of the alloy.
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