Avaliação da adaptação marginal e interna de coroas cad/cam de dissilicato de lítio fabricadas por diferentes unidades de fresagem

Abstract

Objetive: This study aimed to compare the marginal and internal adaptation of lithium disilicate crowns milled using two distinct CAD/CAM systems: MCXL (MX) and Primemill (PM). A secondary objective was to characterize and compare the macrostructural and microstructural features of the diamond burs employed by each system, considering their potential influence on restoration accuracy. Methods: A standardized die simulating a full-crown preparation was scanned ten times (n=10) using the Primescan 1.0 intraoral scanner. Identical crown designs were generated in CEREC 5.0 software and milled using both units. Adaptation was assessed through the triple-scan technique with STL file alignment in Exocad software. Internal fit was measured at five reference points, while marginal adaptation was evaluated in both vertical (MG) and horizontal (MH) dimensions. The surface topography of the burs was analyzed via scanning electron microscopy (SEM). Statistical analysis included homogeneity testing and Tukey’s post hoc test. Results: The PM group demonstrated significantly improved adaptation in all evaluated regions, with the exception of the axial wall (AW), where no statistical difference was observed. Adaptation values for PM and MX, respectively, were: FL [149.5(24.9)–267.4(22.0)] (p<0.0001); AW [114.6(48.9)–127.6(18.2)] (p<0.0001); BC [126.5(19.6)–104.6(13.7)] (p=0.0098); OCF [80.5(26.2)–172.4(17.0)] (p<0.0001); LC [94.1(31.5)–134.6(15.4)] (p=0.0018); MG [2.9(6.2)–16.2(13.07)] (p=0.0002); MH [49.3(43.6)–84.7(46.3)] (p=0.0174). SEM analysis revealed a higher density of diamond particles on MX burs, whereas PM burs exhibited greater overall length and diameter. Conclusion: Primemill demonstrated superior adaptation performance, and distinct bur geometries may significantly influence the precision of crown fabrication.