Accuracy of Chairside Fabricated Endocrowns Using Two Milling Machines and Two Glass Ceramic Materials (in-vitro study)

Background : The accuracy of chairside-manufactured restorations plays a vital role in ensuring the long-term success of endocrown restorations. Factors, such as the type of ceramic material and the milling technique, need to be thoroughly examined to understand their impact on fabrication accuracy in dental offices. Materials and Methods : A typodont model of a maxillary right first molar was prepared for an endocrown restoration, digitally scanned, and designed using CEREC CAD software. A total of 40 endocrowns were fabricated based on the reference design from two materials. Group (E) utilized IPS Emax CAD (N=20), and group (T) used Tessera CEREC blocks (N=20); 10 of each group were milled using MCXL (EX), and the other 10 were milled using primemill (EP), and the same for Tessera (TX) and (TP). All fabricated endocrowns were scanned, and test data were collected in standard tessellation language (STL) format. These datasets, along with the reference design, were compared using reverse engineering software to evaluate the 3D trueness and precision of the fabricated restorations. Data were analyzed using two-way ANOVA. The significance level was set at p<0.05 within all tests. Statistical analysis was performed with R statistical analysis software version 4.4.1 for Windows. ^[1] Results : Root mean square (RMS) values were used to evaluate the 3D trueness and precision between tests. No significant differences in trueness were found between Tessera and Emax samples milled with Primemill (p=0.488) or MCXL (p=0.437). Similarly, no notable differences were observed between Emax (p=0.593) or Tessera (p=0.537) samples milled by either machine. For precision, Emax and Tessera samples milled with MCXL showed no significant difference (p=0.827). However, Tessera samples milled with Primemill had higher precision (23.46±2.03 µm) than Emax (32.81±4.35 µm) (p<0.001). Primemill also produced more precise Emax (p<0.001) and Tessera (p<0.001) samples compared to MCXL. Conclusion : The two milling systems offer comparable accuracy for restoration fabrication, ensuring clinical reliability for chairside use. However, the Primemill machine showed superior precision in fabricating Endocrown restorations compared to the MCXL, suggesting that advancements in milling technology, like improved calibration and milling algorithms, enhance consistency and precision. [1] R Core Team (2024). R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. URL https://www.R-project.org/.