Learn More About Dry Heat
What is dry heat?
Dry heat is basically convection heat – a convection oven. A convection oven uses a fan to circulate warm air throughout the oven to maintain a uniform temperature. In other words, a convection oven is an oven with a fan inside.
How does dry heat work?
Thermoplastic masks and cushions are heat-activated to become moldable when warmed. In a water bath, the hot water transfers heat directly to the thermoplastic. An oven works in the same way. Convection ovens continuously pull hot air across the thermoplastic, exerting a constant temperature differential that quickly and evenly heats the mask or cushion.
All thermoplastic masks can be prepared in an oven. The different proprietary methods each thermoplastic manufacturer uses will create small differences in how the thermoplastic reacts to dry heat, just as there are small differences in each type of mask when prepared in water. Any standard thermoplastic device can be prepared in an oven.
Why is dry heat recommended?
Using dry heat to prepare thermoplastics is beneficial for therapists and patients.
Ovens warm up quickly – Klarity ovens heat up to working temperatures in six minutes. They can be turned off when not in use, and require very little cleaning.
Masks go straight from the oven to the patient, so there is no need for drying space or damp towels on the counter. Ovens can also be moved easily, on a cart for example, with no worry about water spilling out.
A dry thermoplastic mask is more comfortable than a wet slimy mask. Patients are not getting damp or dripped on. With water baths, water evaporation accelerates the cooling process, which creates more shrinkage. Masks prepared in dry heat shrink less and fit better.
Less risk of bacterial infection
Ovens are ultimately safer for patients and therapists. Ovens help reduce the risk of bacterial infection by removing water from the treatment room.
Standing water is nearly always a breeding ground for bacteria unless significant steps are taken to kill the bacteria. At temperatures under 250˚F, bacteria can produce spores that can survive quite extreme conditions for a long period of time. These spores will reproduce and form new colonies when a hospitable environment occurs. Though most mesophilic bacteria and human pathogens will be killed at 165˚F, some mesophiles exhibit increased tolerance to heat when they are exposed to high temperatures for short periods. Additionally, some heat-tolerant bacteria such as bacillus respond to heat by rapidly forming spores. The temperature needed to effectively inactivate bacillus spores is well above the range used to heat thermoplastics. Bacteria can easily take to the air via aerosols, or tiny water droplets if the water is shaken around at all.
Ovens mitigate the risk of bacterial infection by removing water from the mask making process. The fans circulating heat throughout the oven create an exceptionally dry atmosphere, so no water, and therefore no waterborne bacteria, is present.
A recent study titled “Risk of Patient Infection From Heating Appliances Used to Produce Thermoplastic Immobilization Devices”, was published in the 2014 Radiation Therapist Journal and awarded the Radiation Therapist Distinguished Author Award in Honor of Harold Silverman. This study documents the risk of patient infection from water baths.
This study tested twelve water bath devices in different clinics in a 200 mile range. Of the twelve, 5 showed bacteria on the lid, and 2 showed bacteria on the base. One base showed Bacillus, and the other showed coagulase-negative staphylococcus (CNS). Of the lids, one showed Bacillus, 3 showed CNS, and one showed both CNS and Corynebacterium.
The study also found that only one of the twelve sites was allowing the water to warm for 2 to 3 hours before using, as recommended by the manufacturer.
According to the Center for Disease Control and Prevention, Pseudomonads along with other waterborne bacteria are associated with occasional infection outbreaks. Patient infection means that a transmission of microorganisms has occurred, which can happen through several avenues, but all require an infection source. Dry heat helps to mitigate the risk of bacterial infection by eliminating water from the treatment room.
Though switching to dry heat may initially require an adjustment in work flow, once they make the switch, therapists report being much happier overall. We at Klarity believe that dry heat is a superior method for preparing thermoplastics, and is ultimately safer and better for you and your patients. We encourage you to check out our new AirFlow Oven, which features a faster heating time and double shelving for heating multiple thermoplastic devices simultaneously. For more information, please contact us directly.