Effect of triturator speed variation on physical properties of encapsulated glass-ionomer luting cements

This in vitro study evaluated the effect of variation of triturator mixing speed on the physical properties of two encapsulated glass-ionomer luting cements. Physical properties evaluated were working time, setting time, film thickness, and 24-hour and 7-day compressive strengths. Encapsulated glass-ionomer luting cements were mixed at 3000, 3500, 4000 (control), and 4500 cycles per minute (cpm). An oscillating rheometer was used to determine working and setting times. Film thickness and compressive strength were determined using methods described in ANSI/ADA Specification No 66 for dental glass-ionomer cements. Results of the study indicated that decreased mixing speed may prolong working and setting times for Ketac-Cem Maxicap Fuji Cap I. Within the range of 3500 to 4500 cpm, variations in mixing speed do not significantly affect compressive strength or film thickness values for either cement. Excessively slow mixing speed (3000 cpm) often resulted in the presence of unmixed powder expressed from the capsule nozzle prior to the expression of mixed cement. The presence of this unmixed powder results in a decreased powder/liquid ratio, which may have an adverse effect on the physical properties of the set cement.