IADR Abstract Archives
Effect of Firing Process on Accuracy of Machinable LDS Blocks
Objectives: A novel lithium disilicate (LDS) glass ceramic, Initial LiSi Block does not require the crystallization process after CAD/CAM fabrication. On the other, staining and glazing are applicable as one of options if required. The objective of the study is to evaluate the accuracy of the geometric crown before/after firing process.
Methods: Three LDS glass ceramic blocks shown in the table were tested. The geometric crowns were fabricated from these glass ceramic blocks using CEREC MC XL(Production repeatability: ±25µm, Dentsply Sirona). The obtained crowns ware crystallized or glazed according to manufacturers’ instructions. Then, the accuracy was compared by superimposing the crowns and the original STL data. The accuracy was defined as percentage within the production repeatability(±25µm). Therefore, higher values indicate better accuracy. The data was analyzed with one-way ANOVA and Tukey’s tests (p< 0.05).
Results: The table shows the results. Same superscripts indicate no significant difference. LS was the most accurate both before/after glazing process.
Conclusions: EM requires crystallization at the temperature above the deformation point as shown in the Table. Therefore, we considered that the dimensions were deformed during crystallization. CT was no significant difference before/after glazing process. However, we found CT has the lower accuracy values and the large standard deviation. CT is took longer grinding process time. This means CT is difficult to grind and it may affect to accuracy. Thus, CT is considered that it could not be grinded it accurately in accordance with the STL data. The accurate workpiece was fabricated from LS because LS has good grinding properties by CAD/CAM machines. In addition, LS is stable under heat treatment for glazing.
Methods: Three LDS glass ceramic blocks shown in the table were tested. The geometric crowns were fabricated from these glass ceramic blocks using CEREC MC XL(Production repeatability: ±25µm, Dentsply Sirona). The obtained crowns ware crystallized or glazed according to manufacturers’ instructions. Then, the accuracy was compared by superimposing the crowns and the original STL data. The accuracy was defined as percentage within the production repeatability(±25µm). Therefore, higher values indicate better accuracy. The data was analyzed with one-way ANOVA and Tukey’s tests (p< 0.05).
Results: The table shows the results. Same superscripts indicate no significant difference. LS was the most accurate both before/after glazing process.
Conclusions: EM requires crystallization at the temperature above the deformation point as shown in the Table. Therefore, we considered that the dimensions were deformed during crystallization. CT was no significant difference before/after glazing process. However, we found CT has the lower accuracy values and the large standard deviation. CT is took longer grinding process time. This means CT is difficult to grind and it may affect to accuracy. Thus, CT is considered that it could not be grinded it accurately in accordance with the STL data. The accurate workpiece was fabricated from LS because LS has good grinding properties by CAD/CAM machines. In addition, LS is stable under heat treatment for glazing.