Fracture strength of borosilicate glass melt infiltrated zirconia 3-unit bridge

This study examined the fracture strength of 3-unit all-ceramic zirconia bridges treated with a melt-infiltration process of borosilicate glass. The zirconia specimens were milled with presintered yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) blocks. Before veneering the porcelain, borosilicate glass was infiltrated into the zirconia at 1,100°C for 1 hr. A 3-point flexural test was carried out at crosshead speed of 0.1 mm/min. The fracture surface and interface between the zirconia and veneer porcelain were observed by scanning electron microscopy. The fracture strength of the Y-TZP specimens was increased significantly by the melt-infiltration process of borosilicate glass (P < 0.05). The bond strength of the porcelain on zirconia was also improved significantly by meltinfiltration process of borosilicate glass (P < 0.05). The resistance to the initial chipping of the veneered porcelain in the 3-unit allceramic zirconia bridges was increased significantly by melt-infiltration process of borosilicate glass (P < 0.05). According to the microscopic observations of the fracture surface of porcelain, the glass-infiltrated zirconia group showed a rough fracture surface, whereas the sintered zirconia group showed a smooth fracture surface containing many pores.