· Ceramic surfaces were exposed to acid etching for four different time intervals with 5% hydrofluoric acid gel for dental use (IPS Ceramic etching gel™, Ivoclar Vivadent, Schaan, Liechtenstein). The etched samples were examined under a scanning electron microscope (SEM) (JSM6360LV, JEOL, Tokyo, Japan) to study the pore pattern, width, and depth.