COMPARATIVE-STUDY OF 4 GLASS-IONOMER LUTING CEMENTS DURING POST PULL-OUT TESTS

Objectives. The aim of this study was to compare the maximum loads and modes of failure of four glass ionomer luting cements during post pull-out tests. Methods. The cements studied included two based on conventional glass ionomer cement chemistry, i.e., a hand-mixed cement and an encapsulated cement, and two based on the newer light-cured chemistry, i.e., a restorative cement used at a low powder:liquid ratio and an experimental luting cement. One hundred and forty bovine incisors were cut 13 mm from the apex and prepared with post channels, 1.75 mm in diameter and 9 mm long. Ni-Cr-Mb bonding alloy posts were cast and sandblasted prior to cementation into the roots with each of the cements. Twenty-four hours later, pull-out tests were carried out at a strain rate of 0.5 mm/min. The maximum loads and modes of failure were noted. The data obtained were analyzed using a Kruskal-Wallis test followed by comparison of groups using Mann-Whitney tests. Results. Comparison of the maximum loads revealed a significant difference between the conventional encapsulated cement and all other cements. Weibull analysis of the results gave values for the Weibull moduli and probabilities of survival for a post under a given load for each cement and indicated that the newer cements performed better than the conventional cements. Significance. Further research into the in vitro and in vivo behavior of the resin-modified glass ionomer cements in clinical situations where light-curing is not possible is justified.