Influence of erosive challenge and immersion in coloring solution on the optical properties of glass ceramics for CAD/CAM, submitted to different surface treatments (glaze versus mechanical polishing)

Abstract

The aim of this study will be to evaluate the influence of erosive challenge and immersion in coloring solutions on the optical properties of two glass ceramics for CAD/CAM, submitted to different surface treatments, then 170 specimens of each glass ceramic tested will be manufactured: (FC) feldspar ceramic (CEREC Blocs) and (LS) ceramic based on lithium disilicate (IPS e.max CAD) which will be divided into 2 groups according to the surface treatment : (G) Glaze (Ivoclar) (n=60) or mechanical polishing (Ceramisté kit - Shofu) that will be subdivided into: MP - mechanical polishing (n=60) and CP - clinical polishing/repolishing (n=20). Each group will be subdivided according to erosive challenge and solution immersion: (EC) Erosive challenge: immersion in 5% HCl (pH = 2.0) for 91 hours (EC1), 182 hours (EC2) and 273 hours (EC3) ; (EC + I): after each EC period the specimens will be immersed for 90 days in different solutions (IDW - distilled water and IBT - black tea); and (C) Control: the specimens (n=10) will be kept in controlled humidity throughout the experiment (C = 24 hours, C1 = 91 hours, C2 = 182 hours and C3 = 273 hours). For groups CP - Clinical polishing, after EC1, EC2, C1, and C2, specimens will be polished to simulate periodic intraoral polishing (CP). The analyzes will be carried out after the periods of C, EC and EC + I. The groups that will receive clinical repolishing (CP) will be analyzed after EC2 (repolished after EC1), EC3 (repolished after EC1 and EC2), C2 (repolished after C1) and C3 (repolished after C1 and C2). Response variables will be considered: color change (”E00, ”L, ”C, ”H), translucency (TP) and contrast (CR). The data obtained in each analysis will be submitted to the normality test and later to the most appropriate statistical test, with a 5% significance level. (AU)