National Dental Assisting Examining Board (NDAEB) Practice Exam

How is impression material mixed when using an extruder gun?

1. Before placing it on the tray

2. After it leaves the nozzle

3. As it moves through the mixing tip

4. By hand in a separate bowl

The correct answer is: As it moves through the mixing tip

When using an extruder gun for mixing impression material, the correct process involves mixing the material as it moves through the mixing tip. The extruder gun is designed to simultaneously mix and dispense the material, ensuring a homogeneous mixture right before it is delivered onto the impression tray. This method offers the advantage of minimizing air incorporation and achieving a consistent mixture, which is crucial for accurate impressions. Mixing before placing it on the tray would not utilize the efficient mixing capabilities of the extruder gun, and doing so in a separate bowl would introduce additional steps that could potentially lead to inconsistent results or contamination. Mixing after the material leaves the nozzle would not be effective either, as it would cause the impression material to begin to set before it is adequately mixed. Thus, mixing within the mixing tip as the material is extruded provides the best outcome for creating reliable impressions.