In vitro fatigue resistance of glass ionomer cements used in post-and-coreapplications

Statement of problem. New glass ionomer cements exhibit better mechanical p roperties than their older counterparts. However, there is concerti about t heir use as a core material in post-and-core applications. Purpose. This in vitro study evaluated the fatigue resistance of 2 new glas s ionomer cements, Shofu Hi-Dense and Fuji IX GP, and compared their mechan ical behavior as a core material under masticatory load with a silver-reinf orced glass ionomer (ESPE Ketac-Silver) and a silver amalgam (Cavex Avaloy LC). Material and methods. A total of 100 commercial plastic teeth were divided into 4 groups of 25 specimens each. Titanium posts were placed in the prepa red root canals, and cores were built up in amalgam, silver-reinforced glas s ionomer cement, and the 2 new glass ionomer cements. The post-and-core sp ecimens were prepared for full cast metal crowns, which were fabricated and cemented with glass ionomer cement, Twenty specimens from each group were placed in a mastication simulator and cyclically loaded with a 400 N force for 1.5 million cycles. The 5 remaining specimens were used as controls. Th e specimens were sectioned and observed macroscopically and microscopically to determine the number of defects (alterations) in each material. Observe d defects were verified with the Kruskal-Wallis test, and the 4 core materi als were ranked with the Tukey multiple comparisons test. Results. The mean rank sum values of the defects were as follows: Cavex Ava loy LC Amalgam (16.75), Fuji IX GP (38.50), Shofu Hi-Dense (39.53), and ESP E Ketac-Silver (67.22). The amalgam alloy was significantly different (P < .05) from the others. Conclusion. Under the conditions of this study, the 2 new glass ionomer cem ents used as core materials showed a higher number of defects than amalgam. These results suggest that their fatigue resistance may be inadequate for post-and-core applications.