Vinyl Polysiloxane, or VPS, impression material involves a chemical reaction between 2 substances known as a base and a catalyst. These two components must be mixed evenly and thoroughly for the product to set correctly. There are 4 main delivery methods to creating this mixture. Each has its own benefits and drawbacks and there are many different products and vendors to meet your specific needs.
Hand Mixing, tubes. In this method, two separate tubes of a base and a catalyst are mixed together by hand. A line of each component is squeezed out onto a mixing pad or a glass slab and mixed using a spatula. Equal amounts of each are used and mixing is complete when it becomes homogenous, or all the same color. As with any product though, follow specific direction from the manufacturer. While this method can allow room for error by using disproportionate amounts of each, the benefit is that there is typically less waste than other methods.
Hand mixing, putty. Similarly to above, this method involves mixing a base with a catalyst manually. The difference is that each component is scooped from a tub and mixed using your hands instead of a spatula. It’s important to note that using latex gloves and lotions are not recommended because they can interfere with how the product sets. This method is less messy than the above and is easy to use with a tray.
Cartridge delivery form. A preloaded cartridge contains a base and a catalyst in two separate chambers. Using a dispenser gun, the components are squeezed out through a mix tip which automatically dispenses and mixes the exact amount of each to create a homogenous solution. This method eliminates room for error and mess, but it does leave material left in the mix tip that must be discarded. It is an otherwise easy method and is simple to use with a tray.
Automatic mixing machine. The base and the catalyst are mixed together using a special unit that dispenses through 1-time use tips. Once the foil bags are loaded into the machine and locked in place, dispensing the impression material into a tray is as easy as pushing a button. There isn’t any mess with this delivery form, but the drawback comes with the price tag of the mixing unit. Perhaps the biggest advantage though is that once the foil bags are loaded, the system is ready to go until the material runs out as long as a new tip is added before every use.