Influence of polishing and pigment oxides on three-point flexural strength of commercial glass ceramics

Abstract

The present in vitro study aims to evaluate the possible influence of polishing and pigment oxides on the three-point flexural strength of commercially available glass-ceramic. The data will be compared between two glass-ceramic, considering that the differences in composition and processing may lead to different mechanical behavior. For this purpose, a block of lithium disilicate (IPS e.max CAD®, Ivoclar Vivadent) A1, a block of lithium disilicate A3, a block of lithium silicate reinforced by zirconia (Celtra Duo®, Dentsply Sirona) and a block of lithium silicate reinforced by zirconia A3 will be cut in a digital cutting machine using a diamond disk (245 rpm, under refrigeration) in bars of 4mm width X 2mm thickness X 14mm length, according to ISO 6872. In addition, other blocks of the same materials and shades will be cut into bars of 5mm width X 3mm thickness X 14mm length and worn on silicon carbide (320 grit) sandblasters coupled in a metallographic polisher (Aropol 2V, Arotec) until reaching the proposed measures by ISO 6872. In this way, 8 groups will be obtained, consisting of 10 bars of each material (n=10/group). Initially, these bars will be subjected to a 3-point bending test using a metallic device with a load cell of 5000 N at a constant speed of 0.5 mm / min through a KRATOS KE universal test machine and with the aid of the Tesc® 2.0 automation program. The qualitative fractographic analysis of the fractured specimens will be performed by the digital stereomicroscope Axio Zoom.V16. The obtained data will be organized and, if they present normal distribution, will be submitted to ANOVA and complemented with the Tukey test; if there is a non-normal distribution, they will be submitted to Kruskal-Wallis and Dunn non-parametric tests.