Maturation affects fluoride uptake by glass-ionomer dental cements

Objectives. Four commercial glass-ionomer cements have been studied for their ability to take up fluoride from aqueous solution following variable maturation times in the dry at 37 ◦C. Methods. Sets of five specimens of four different materials were cured for times of 10 min, 24 h and 1 month, then transferred to a neutral solution of NaF at approximately 1000 ppm in fluoride. Fluoride concentration was then measured at regular time intervals up to 1 month using a fluoride ion selective electrode. Results. Specimens cured for 1 month showed little or no uptake over 24 h, specimens cured for 24 h showed fluctuating uptake over time, and specimens cured for 10 min showed the greatest fluoride uptake. For the latter specimens, simple kinetic models were found to apply in two cases (pseudo-first order and pseudo-second order for Chemflex and Ketac Molar Quick respectively). Significance. The ability to take up fluoride has been shown to decline with age of cement which suggests that in clinical use glass-ionomers may become less effective at undergoing fluoride recharge than has been previously assumed.