A thermoform machine is used to fabricate aligners by pressure-forming the plastic aligner material over the printed model.
There are two types of machines that orthodontists use to mold plastic sheets: vacuum and pressure molding. Only pressure molding is recommended for in-house aligners.
The primary differences between the two are the reproducibility and the amount of pressure that can be generated.
For Retainers Only
The vacuum machine utilizes an electrically driven vacuum motor to mold a plastic sheet that has been partially melted with a heating unit. The plastic sheet is placed in a sliding hinged frame that is raised against the heating unit. The melting of the plastic sheet is eyeball-measure by the operator and then the frame is manually lowered over the model below. Since atmospheric pressure is 14.7 pounds per square inch (1 bar unit), this is the theoretical maximum forming pressuring available when vacuum forming.
A classic vacuum machine that orthodontists are familiar with is the “Essix Machine.”
For Retainers and Aligners
The pressure molding machine is an enhancement of the vacuum forming process by utilizing both a vacuum and pressure on opposite sides of the plastic sheet. Simply put, a pressure box is added to the non-mold side of the sheet. Furthermore, the pressure molding machine has the heating and cooling times programmed via a keypad for consistency. Most importantly, a pressure molding machine can generate between 3-7 bars of pressure.
The ideal range of pressure to fabricate in-office aligners is 3-4 bars, or 50 pounds per square inch, which is significantly greater than can be generated by a vacuum machine.
Therefore, only a pressure molding machine is appropriate for fabrication of in-office aligners.
Depending on the type of pressure molding machine and the amount of bars that it can generate, the cost will range between $2,500-4,000.