Crown retention with three resin-modified glass ionomer luting agents

The author used a standardized technique to investigate the retentive properties of three resin-modified glass ionomer (RMGI) cements in the cementation of precious gold copings.

The author machined premolars on a jeweler's lathe to a taper of 16 ± 0.5 degrees. The occlusal table measured 4 millimeters. The author fabricated wax patterns with a uniform 360-degree internal fitting surface of 2.7 mm. Each group consisted of 10 samples. The author invested the wax patterns and cast them in gold. He cemented the copings as follows: group 1, RelyX Luting Plus (3M ESPE, St. Paul, Minn.); group 2, Fuji Plus Resin-Reinforced, Multipurpose Cement (GC America, Alsip, Ill.) and group 3, UltraCem Resin-Reinforced Glass Ionomer Cement (Ultradent Products, South Jordan, Utah). The author performed the cementation under controlled pressure. After 24 hours, he applied a tensile force until catastrophic failure (expressed as kilogram force at failure) occurred. The author used analysis of variance for statistical analysis (P < .05).

A statistically significant difference was demonstrated between UltraCem and the other two cements tested (P < .05), whereas no statistical difference could be demonstrated between RelyX and Fuji Plus (P > .05).

By using an established standardized ex vivo crown retention test, the author found that the three RMGI cements he tested generated retention values that were clinically desirable when compared with those of other commercially available cements that have been used successfully for many years. UltraCem scored the highest values, followed by Fuji Plus and RelyX, respectively.

Cementation of precious alloy crowns and bridges by using RMGI cements tested in this study generated retentive values that mostly exceeded those of conventional luting agents.