In Vitro Analysis of Techniques that Alter the Surface Hardness of a Glass Ionomer Restorative Material.

Aim: The aim of this in vitro study was to compare the effect of different manipulation techniques on the surface hardness of ChemFil Rock glass ionomer.
Materials and Methods: The changes in Vickers surface hardness (VH) of ChemFil Rock were evaluated after the application of five manipulation techniques and compared with one control group ( n = 60). The manipulation techniques included: finger pressure set, electronic piezo producing a high frequency set, air piezo producing a low frequency set, heat-set achieved with a curing light and the last technique was a combination of electronic piezo followed by heat-set. Standard set was the control.
Results: The average surface hardness for the standard set was 49.5 VH. No statistical differences were demonstrated when the means were compared for finger pressure set (49.2 VH) or the air piezo set (48.49 VH) with standard set. The electronic piezo (54.21 VH) and the heat-set (57.5 VH) had an increased mean surface hardness when compared to other techniques. Heat-set had the highest surface hardness demonstrating a significant statistical difference when compared with standard set, finger pressure set, air piezo set as well as the combination of electronic piezo ( p < 0.05).
Conclusion: The surface hardness of the glass ionomer cement (GIC) material assessed in this study can be predictably improved by applying the heat-set technique. A command set can be achieved with the electronic piezo or the air piezo, however, the surface hardness will only increase with the use of the electronic piezo.
Clinical Significance: The clinical advantage of using the air piezo as well as the electronic piezo technique would lie in preventing moisture contamination and dissolution of the GIC due to the command set effect of the ultrasonic vibrations within 15 seconds. The heat technique with the LED curing light will reduce the setting time to 90 seconds.