Effect of Polishing Protocols on the Properties of CAD/CAM Ceramics

Objectives: The aim of this study was to evaluate the physical, chemical and mechanical of lithium disilicate ceramics for the CAD/CAM system, submitted to different clinical polishing protocols and after cycles of thermal fatigue with and without repolishing.
Methods: A total of 204 specimens were prepared and divided into 07 groups according to the polishes performed on their surfaces and thermal cycling cycles (TC). Three polishing systems will be evaluated: Glaze, Ceramisté Polishing Kit and OptraFine Polishing Kit. The aging was perfomed by different tests: T1- storage in distilled water for 24 hours; T2 - after 21,900 cycles for 30 seconds of TC (TC1); T3 - after 43.800 cycles of TC (TC2) and after 21.900 cycles of TC + repolishing of the specimens + 21.900 cycles of TC. Five response variables were considered: (1) surface roughness (Ra), (2) surface energy (SE), (3) scanning electron microscopy (SEM) associated with energy dispersive spectroscopy (EDS), (4) flexural strength (FS), and (5) modulus of elasticity (ME).
Results: The results of Ra showed statistical difference among all groups, and the Glaze Group showed lower values. For SE, there was a decrease in values after 43,800 cycles of thermal cycling in all groups. The SEM images showed a smoother and homogeneous surface in Glaze Group specimens. In FS, after 43,800 cycles of thermal cycling, the Glaze Group presented higher values, being statistically different from all other groups. In ME, the groups that received glaze had higher values than the other groups
Conclusions: The repolishing protocol favored the surface characterization of the specimens but did not influence flexural strength and modulus of elasticity, except the group that was polished with the OptraFine kit. In all quantitative analyzes, aging through thermal cycling had a negative influence on the evaluated properties, except for ES analysis, which, in general, after aging, decreased values.