Aging characteristics of four hybrid glass ionomers

Summary form only given. The objective of this study was to evaluate the change in Barcol hardness of five different hybrid glass ionomers (GI) after storage in distilled H/sub 2/O at 37/spl deg/C. The materials were (A) Encapsulated and (B) Handmixed Variglass (Caulk Dentsply, Milford, DE), (C) Vitremer (3M, St. Paul, MN), (D) Fuji II (GC Corp., Tokyo, Japan) and (E) Photacfil (ESPE Premier, Norristown, PA). Barcol hardness measurements were taken on all the samples after twenty-four hours, 1 week and 1 month of aging. Comparison of the initial hardness using ANOVA (p<0.05) revealed no significant differences. However, materials A and B showed a decrease in hardness after 1 week of storage. In contrast, materials C, D and E showed a significant increase (p<0.05) in hardness after storage. Based upon these results, it may be concluded that materials C, D and E continue to react during aging resulting in a harder material. In contrast, the materials A and B do not continue to react but actually become softer due to plasticization by absorbed water. The additional reaction of materials C, D and E is most probably the result of further ionic crosslinking which may be facilitated by water absorption.