An important task in the dental prosthodontics clinic is to take impressions, pour impressions, and make restorations for each restoration patient. During the process of taking impressions, trays and impression materials are used to place them in the patient’s mouth.

After the impression is poured into the plaster model, the tray must be separated from the used impression material in the tray so that the tray can be reused after disinfection.

It is difficult to separate the impression material from the tray. Since there are many small retention holes on the tray, the small holes are filled with impression material during the impression taking process, making it very difficult to clean, especially now that more and more silicone rubber impressions with high strength and hardness are used clinically.

The material, polyether rubber impression material, is even more difficult to clean and separate. It usually takes about 2 minutes to clean a tray. When the outpatient volume is large, the prosthetic department of our hospital requires 2 nurses to clean for about 2 hours every day.

After long-term exploration, we have found a way to easily separate the tray and impression material by using the principle of thermal expansion and contraction.

① Soak the tray with the impression material after the model has been filled in a disinfectant solution containing 500mgL of available chlorine for 15 to 30 minutes to perform preliminary disinfection of the tray to prevent the tray from drying out.

② Take out the tray that has been soaked in disinfectant and place it in the freezer of the refrigerator at -18°C for 2 hours.

③ Take out the frozen tray and rinse it under running cold water. At this time, the tray and the impression material have cracked. Just tear it off gently with your hands.

④ If there is still a little impression material stuck to the edge of the tray, you can bake it in an oven at 180°C to shrink and dry it, or soak it in 1% sodium carbonate solution for 2 hours to dissolve the fine impression material, and rinse it with clean water. After rinsing, perform pressure steam sterilization and set aside.

Using the above method to clean and disinfect trays can achieve twice the result with half the effort, greatly improving work efficiency and reducing the labor intensity of nurses.