Conventional and electric field-assisted ion exchange on glass-ceramics for dental applications

Ion exchange can be used to mechanically reinforce dental glass-ceramics to reduce the problems associated to the flaws created upon various processing steps and handling. This work introduces a novel ion exchange method to the field of dental glass-ceramic to increase the possibilities of preparing highly reliable glass-ceramic restorations. The aim of the study was to compare Electric Field-Assisted Ion Exchange with conventional method, for newly developed nepheline based dental glass-ceramic. Multicomponent glass system was synthesized using melt-quench method and then prepared into glass-ceramic specimens via powder sinter-crystallisation route. The prepared glass-ceramic specimens were tested for bi-axial flexural strength before and after ion exchange according to the dental ceramics ISO 6872:2015. Ion exchange process was carried out in molten potassium nitride and the potassium penetration depth determined by EDXS was found greater and occurring in a matter of minutes within the nepheline crystal structure during electrical field assisted ion exchange compared with several hours of conventional treatment. The newly developed nepheline glass-ceramic system and the results achieved by electrical field assisted ion exchange may renew the ion exchange concept for dental application.