pH changes of glass-ionomer lining materials at various time intervals

The purpose of this in vitro study was to evaluate pH changes of resin modi fied glass-ionomer (RMGI) and conventional glass-ionomer liners at short-te rm intervals after mixing to relate the timing of light activation on the a cidity of RMGI lining materials. The RMGI liners tested were Vitrebond(TM) (3M), Variglass VLC(TM) (Dentsply), Fuji Lining LC(TM) (GC Dental Industria l Corp.) compared to a traditional glass-ionomer liner: Lining Cement(TM) ( GC, control). Light activation of liners was carried out at different time intervals after mixing. The pH changes of each liner were evaluated immedia tely after mixing and thereafter every minute for 8 min using a surface pH meter. All liners tested exhibited a gradual increase in surface pH over ti me. The delay of light activation of RMGI lining materials after mixing did not significantly decrease the acidity of the liner during the first 9 min post-mixing.