Thermomechanical Analysis of Glass Ionomer Restorative Materials

Objectives: Objective: To analyze high-viscosity glass ionomer (GIC) and resin modified glass ionomer (RMGI) restorative materials using thermal mechanical analysis (TMA).
Methods: Methods: Approximately 3mm x 5mm x 8mm specimens (n = 12) were fabricated following manufacturer directions of each material and were stored at 37C in distilled water. The materials during evaluation were kept moist using a specially-designed silica boat, placed in a TMA unit (Mettler Toledo), and subjected to a 15-50C heating and cooling cycle at 5C/min rate. Coefficient of Thermal Expansion (CTE) was determined using the slope of each respective cycle. Each sample was run 3 times with the mean representing each sample. Mean results between heating and cooling for each sample were compared with paired t-test while results between materials were compared with ANOVA and Tukey post hoc (p=0.05).
Results: Results: Results are listed in the Table.

Conclusions: Conclusions: This is the first evaluation reporting material CTE during both heating and cooling cycles. Conventional GIC materials have lower CTE values than RMGI. RMGI products have CTE comparable to that of some resin composite materials. CTE difference between heating/cooling may not be clinically significant.