Bubbles happen from time to time and can be unavoidable. Some of the most common reasons for air bubbles include:
Waxing too thick: Waxing too thick is the number 1 reason bubbles often occur. Flexible partials should be waxed approximately 1.5mm thick for small cases with abutment teeth and 2.5 - 3mm where the saddle connects to the abutment teeth in free end saddles. If a thicker wax-up is unavoidable, try to wax as close as possible to the final case.
Incorrect spruing method: When spruing use 2 - 3 sprues at the tip end of a wax-up and be sure the connection between the sprue and the waxed model is thin. Adding too much wax to the connection may cause an air bubble. Avoid placing the sprues too close to the teeth, as this will also cause air bubbles underneath the teeth. Refer to the diagram below for proper placement and sprue thickness.
Not using enough pressure: Use the correct pressure when injecting TCS resins. Injecting slowly or with a low pressure may cause bubbles to develop.
Overheating the flask: If injecting Unbreakable or iFlex, the flask should be at room temperature. (When working with a TCS Automatic Air Injector Unit, DO NOT leave the flask in the injecting position during the entire melt time. Alternatively, position the flask on top of the machine 1 minute before injecting).
Using the wrong cartridge size: Select the right cartridge size on a case by case basis. If a case is larger than the selected cartridge, the material will not fill the case properly, causing bubbles to cover the partial.