Effect of chemical composition and microstructure on the mechanical properties of resin composite CAD-CAM materials.
Fernando Ledesma-Renedo1, Dr. Francisco Martínez-Rus1, Dr. María Paz Salido1, Dr. Marta Aragón-Camino2, Prof. Miguel Ángel Rodríguez-Pérez3, Prof. Guillermo Pradíes4
1 Department of Conservative and Prosthetic Dentistry, Faculty of Odontology, Complutense University of Madrid, Madrid, Spain,
2 BioCritic. Group for Biomedical Research in Critical Care Medicine, Valladolid, Spain,
3 Cellular Materials Laboratory (CellMat), Condensed Matter Physics Department, University of Valladolid, Valladolid, Spain,
4 Department of Conservative and Prosthetic Dentistry, Faculty of Odontology, Complutense University of Madrid, Madrid, Spain.
Objectives
To assess the influence of chemical composition and microstructure on the mechanical properties (flexural strength, flexural modulus, and modulus of resilience) of ten commercially available resin composite blocks indicated for chairside CAD/CAM restorations.
Materials and Methods
The materials studied were Brava (BR; FGM Dental), Grandio-Block (GD; Voco), Shofu Block (SB; Shofu), Cerasmart 270 (CS; GC Dental Products), Brilliant Crios (BC; Coltene), Tetric-CAD (TC; Ivoclar Vivadent), Katana Avencia (KA; Kuraray Noritake), Lava Ultimate (LU; 3M ESPE), Mazic (MZ; Normon), Estelite P-Block (ES; Tokuyama Dental), IPS e.max CAD (EM; Ivoclar Vivadent) as positive control group, and G-Cam (GC; Graphenano) as negative control group. Mechanical properties were measured using a three-point bending test and density using pycnometry. The curing process were characterized by differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) was performed to determine the filler content. Data were analyzed using descriptive and inferential statistics. A principal components analysis (PCA) was also conducted to examine relationships between the different variables.
Results
The mean flexural strength ranged from 130.93 MPa (SB) to 224.25 MPa (GD). The mean flexural modulus varied from 10.15 GPa (SB) to 20.88 GPa (GD). The mean modulus of resilience ranged from 0.67 MPa (LU) to 1.71 MPa (TC). Density values varied from 1.671 g/cm3 (SB) to 2.19 g/cm3 (TC). DSC plots only showed exothermic reaction peaks for BR. Inorganic filler content ranged from 60.65 wt% (BC) to 82.31 %wt (GD).
Conclusions
Density did not affect the mechanical properties of the tested materials. Instead, filler content proved to be a critical determinant. BR was the only material that exhibited free radicals. Therefore, the ability of achieving an adequate chemical bonding of these materials to the substrate remains questionable, since the industrial high-temperature-pressure polymerization results in a higher degree of conversion and less residual monomer in the material.