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Working with dental laboratories across the country one of the common problems our technical department deals with are issues with the laboratory's vacuum mixer. All too often it's the oldest and least taken care of piece of equipment in the dental laboratory. But the fact is that the vacuum mixer is still one of the most important pieces of equipment in the laboratory.

You might be thinking that with all the advancements in digital technology how can the vacuum mixer be so important. The reason we say this is because the vacuum mixer can greatly impact many materials such as gypsum, investment or silicone. All of these materials are foundations that can greatly impact the finished restoration.

One of the problems we find with many vacuum mixers is that the machine is not pulling proper vacuum because of clogging, and the lab does not even realize it. This is common with mixers that have a hose that plugs into the bowl, such as the Power Mixer Plus, but can also be an issue with more modern mixers that do not use a hose. One thing to remember is that just because the gauge reads 27 inHg or more it doesn't mean that it is truly pulling that amount of vacuum.

Here is one way you can check your vacuum mixer if it is the type with a hose that connects to the bowl:

- Turn the machine on without any bowl attached. Then look at the vacuum gauge and if it is reading above 5 or 6 inHg then you may have some blockage from gypsum or investment that got drawn into the hose. To fix this you can typically change the gauze at the end of the hose or clean the tip of the metal piece that is inserted into the bowl.

If you have the type of vacuum mixer where the bowl connects directly to the machine it can be a little more difficult to test your mixer:

- While these newer mixers don't use a hose they can still be prone to clogging. Typically these mixers have an inlet where the bowl connects to the machine, and on the inside of the machine there is usually a filter that can get coated with gypsum and investment. Most manufacturers include instructions for checking and cleaning the vacuum inlet with the machine. Since each machine varies it is best to follow the recommendations the manufacturer outlines.

Some of the other common problems with vacuum mixers are; clogged hoses that cause restricted air flow, worn out seals and gaskets, and missing parts that can cause unwanted problems. Some mixers merely need to have their mixing bowls replaced due to wear and tear.

Checking your vacuum mixer on at least a weekly basis can save you from having a big headache with your casting investment, die stones and other materials.