An in vitro investigation of a poly(vinyl phosphonic acid) based cement with four conventional glass-ionomer cements. Part 1. flexural strength and fluoride release

Objective: To investigate the flexural strength and fluoride release of fou r conventional glass-ionomer cements: Ketac-Molar (KM), HiFi (HF), Vivaglas s Fil (VF), Ketac-Fil (KF) and a newly developed glass polyphosphonate ceme nt, Diamond Carve (DC). Method: Disc specimens (10 mm diameter, 1 mm thick) were prepared and mould stored at 37 degrees C. After one hour, the specimens were removed from th eir mould and immersed in 20 mi of deionised wafer until required for testi ng. Biaxial flexural strength was determined at 1 hour and at 1, 7, 30 and 90 days after the start of mixing. Measurements of fluoride release from th e specimens were carried out at 2 hours and at 1, 3, 7, 14, 30, 60 and 90 d ays after the start of mixing using a fluoride ion selective electrode. The results were analysed using ANOVA and student 't' tests. Results: All the materials displayed different flexural strength patterns, KM and DC became stronger whilst KF and VF plateaued in strength Lc;with ti me. HF peaked in strength and then became weaker. At 90 days, the mean flex ural strengths in decreasing order was as follows. KM greater than or equal to VF greater than or equal to DC greater than or equal to HF > KF. An ini tial fast rate of fluoride release followed by a slower but steady release of fluoride was observed in each of the materials. The mean cumulative fluo ride release in decreasing order was as follows: VF > KF greater than or eq ual to KF > DC > KM, VF released significantly higher level and KM signific antly lower level of fluoride than the other materials. Conclusions: The acid used to form the cement could nor be used to predict changes in cement strength behaviour with respect to time. DC increased in strength with time and its flexural strength at 90 days was comparable to t hat of HF and VF. The cumulative and rate of fluoride release varied for th e materials. DC had a low fluoride release consistent with a fast setting m aterial with good early resistance to water. (C) 1999 Elsevier Science Ltd. All rights reserved.