Nucleation Heat Treatment on the Crystalline Fraction and Crystal Morphology of Lamav Cad Lithium Disilicate

Abstract

Thus, this study aimed to evaluate the influence of different nucleation heat treatments on the crystalline fraction and crystal morphology of the LS2 LaMaV CAD. Discs (12 mm diameter x 1.2 mm thickness) of LS2 LaMaV CAD and IPS e.max CAD (C, control group, n=3) were made. LS2 LaMaV CAD discs were annealed at 380oC/2h followed by different nucleation heat treatments in which time and temperature were varied composing 4 groups (n=3): T1 (1h30/500oC), T2 (3h/500oC), T3 (6h/500oC) and T4 (6h/480oC). Scanning Electron Microscopy images were obtained to characterize the microstructure and to quantify the crystalline fraction using the ImageJ software. X-ray diffraction with Rietveld refinement was performed. ANOVA one-way with Tukey post-hoc test (a = 0.05) was used to analyze the ImageJ images and the Rietveld refinements for X-ray diffraction data. X-ray diffraction analysis showed peaks of approximately 86% of lithium disilicate for all groups. The morphology of crystals was in lath-shaped and homogeneous format for all groups; the group that most resembled the C group was T1. The crystalline fraction (%) was: C = 59.33 ± 0.47, T1 = 61.63 ± 0.61, T2 = 61.07 ± 1.09, T3 = 56.39 ± 0.32, and T4 = 57.48 ± 0.90, all the groups were statistically different to the C group. It was concluded that the nucleation temperature influenced the size and quantity of the crystals of lithium disilicate; treatment that showed the best result was that that received nucleation treatment for 1 hour and 30 minutes at 500ºC.