Influence of the Translucency and Thickness of Permanent 3D-Printed Resins on the Microhardness and Degree of Conversion of Resin Cements
Printing Three-Dimensional; Resin Cements; Polymerization.
Objective: The present study aims to evaluate the influence of the thickness and translucency of 3D-printed resins for definitive restorations on the microhardness and degree of conversion of two types of resin cements. Materials and Methods: Printed resin blocks measuring 9 mm × 7 mm will be fabricated with thicknesses of 0.5 mm, 1 mm, and 2 mm, and with three translucency levels: high, medium, and low translucency. The blocks will be produced using a FlashForge Foto 6.0 printer (FlashForge) and the Voxelprint Ceramic resin (FGM) indicated for definitive restorations.For the fabrication of cement specimens, an adapted mold will be used to standardize the area to be light-cured, as well as the angulation and positioning of the resin and cement blocks. Specimens will be prepared using two types of resin cement (dual-cure cement – All Cem FGM, and light-cure-only cement – All Cem Venner FGM) (N = 200), with dimensions of 3 mm × 3 mm × 1 mm. The groups will be divided according to the following factors: “resin translucency” (HT, MT, LT), “cement type” (dual-cure and light-cure), and “thickness” (control, 0.5 mm, 1 mm, and 2 mm). In the control group, no printed resin will be interposed; therefore, the cement will be polymerized in direct contact with the light source (n = 10).The polymerization protocol will be performed using a Poliwave Bluephase NG4 light-curing unit (Ivoclar Vivadent® Inc., Schaan, Liechtenstein) at an irradiance of 1200 mW/cm² for 40 seconds. Subsequently, Vickers microhardness testing will be carried out using a microhardness tester (402 MVD, Wolpert Wilson Instruments, Aachen, Germany), with a load of 300 g applied for 5 seconds, performing three measurements on each surface (top and bottom). The degree of conversion will be evaluated using Fourier Transform Infrared Spectroscopy (FTIR). The obtained data will be subjected to the Shapiro–Wilk test, three-way ANOVA, and one-way ANOVA to compare the values between the top and bottom surfaces of the specimens.