I often have calls concerning ill-fitting partials. One of the areas overlooked when troubleshooting partials not fitting properly is dehydrating the refractory model. Often, we do not have the correct type of hardware for dehydration. That is to say, you generally cannot rely on the accuracy of the temperature of the toaster oven! Usually these ovens are designed to make toast and not sustain and accurate temperature for a period of time. When dehydrating refractory models, be aware of the precise temperature of the dehydrating oven!

You achieve minimal expansion of the refractory model in the dehydration oven from 200°F to 425°F; however, if you go higher than the recommended 425°F, you run the risk of beginning the thermal expansion that would normally be reserved for the burnout process. Ethyl Silicate investments may begin their thermal burnout expansion around 450°F. Oxy-phosphate investments usually begin their thermal expansion, in terms of burnout, at approximately 475°F. If the dehydration oven is allowed to exceed these temperatures, the refractory models behave as if they were in the burnout oven and they begin its thermal expansion for burnout.

In short, know your equipment and the accuracy of the equipment!

 

 

 

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