3Y-TZP electrostatic painting to increase bond strength to dentin and dental prostheses

Although the clinical method used to improve the adhesion of zirconia prostheses to other materials is sandblasting or acid etching surface, the failure rate of the bond is high. The present work aims to propose an innovative method of zirconia surface painting with an electrostatic technique using epoxy powder paint with antibacterial and antifungal properties to improve the adhesion to dentin. The zirconia samples were divided into 4 groups: without surface painting (GC), painted without surface treatment (G1), hydrofluoric acid etching before painting (G2), and blasted with alumina before painting (G3). The samples were characterized by X-ray diffraction, scanning electron microscopy, Vickers hardness, 3D roughness, and cytotoxicity. Shear bond strength (SBS) tests were used to measure the zirconia bonding to synthetic dentin (NG-10 polymer). The opacity of painted zirconia was evaluated using a spectrophotometer with contrast ratio as a translucency parameter. The results showed the sintered zirconia had high densification, and submicrometric tetragonal (t-ZrO2) and cubic (c-ZrO2) grains. The bonding shear strength of zirconia without surface painting and surface treatment (3.51 MPa) was the lowest. The highest bonding strength was painted zirconia without surface treatment (15.51 MPa). The zirconia etched with HF had a lower shear strength (5.75 MPa) than the zirconia blasted with alumina (7.76 MPa). As the painting coating thickness increased, the opacity increased. The cytotoxicity tests showed that the coated zirconia is biocompatible. The zirconia painting with epoxy powder paint methodology facilitates the manufacture of dental prostheses and increases the shear bonding strength to dentin.