Most dentists, assistants, and lab technicians want to convey a good experience for the patient, so they take pride in the services they provide. Part of this service is ensuring accuracy and avoiding unnecessary visits for the patient. This helps lower anxiety and expense for all involved. When it comes to using dental gypsums or investments, consistent accuracy is the best way to deliver quality treatment. One way to achieve consistent accuracy is to use pre-weighed envelopes. The proper amount of liquid amount is indicated on every package, thereby eliminating the need for guessing the liquid/powder ratio.
The advantage of bulk powder, especially for a busy facility, is purchasing greater volume at an economical price point. At some point during our training, we learned that gypsums and investments require very specific liquid and powder ratios. However, over time we forget this, and get into the (bad) habit of mixing the powder and liquid to what we “feel” is the right consistency. Some of this mindset comes from alginate proportions, i.e. so many units of water to so many scoops of powder. For alginate, this is fine and works well due the nature of the material.
With gypsums and investments, each has a specific liquid/powder ratio. Getting ratios right every time is crucial if consistent accuracy is the goal. The only way to do this is to weigh the powder and measure the liquid. The thought of doing this every time we mix does not appeal to most people. The reality is we resort to mixing it to the point that it “feels” right. No matter how experienced a technician is, “feeling” cannot be accurately quantified – nor repeated - every time. Therefore, what we have done for the sake of speed and convenience is to sacrifice predictability. As the old saying goes, if you have time to do it wrong, you have time to do it twice. Do you want it right or right now? I think most people would want to do the task correctly the first time.
A good solution is make your own pouches. All you need is a digital scale, some sandwich bags and a tray to put your pouches on. Make sure to tare the scale when you place the empty bag on the scale. Failing to do this could make your pouches off weight. Most gypsums and investments publish their liquid/powder ratios in 100-gram increments, so keeping the bags evenly 100, 200, and 300 grams, etc., would be best when calculating the liquid needed. Usually someone in the lab or the clinic has some free time throughout the day to do this. Once a system is set with weighed pouches, it takes surprisingly very little time. This makes for an easy and fast way to get accurate results without the expense of pre-weighed envelopes.