Why are some furnaces fitted with an infrared camera?

You may have heard that certain ceramic furnaces are now available with an integrated infrared (IR) camera. If you would like to find out more about the benefits of infrared technology, read on!

Entirely new possibilities

Infrared imaging technology is now being used in dental ceramic furnaces. The dental community is excited about this development because it opens up entirely new possibilities.

Background I: What does an infrared camera do?

An IR camera detects infrared radiation, evaluates it and then generates a thermal image. This procedure is called thermography. The produced thermal images are based on temperature measurements which are not visible to the human eye.

Since we are unable to see infrared rays, we have to rely on a simple trick to make them visible. The camera allows us to display false colour images on its display. These pictures enable us to recognize the temperature information. Blue usually represents cold areas and red shows the hot areas.

All objects and living things with a temperature above absolute zero (= -273.15 °C) emit rays in the infrared spectrum. Even objects which we perceive to be very cold release infrared energy.

Background II: Where is infrared technology used?

Infrared imaging is used in civil engineering, for example, to check the thermal insulation of roofs and to analyze brickwork and windows. Cracks in walls and leaks in plumbing can also be identified with thermal imaging.

In addition, fire fighters use IR cameras to detect smouldering pockets in fires and to search for people in buildings in situations where visibility is poor.

In recent years, the automobile industry has also started to recognize the benefits of infrared technology. IR cameras are built into cars to detect the heat given off by people and animals in or on the side of the road at dusk or at night. As a result, potential dangers can be recognized early and accidents prevented.

Thermal imaging is also used in the aviation industry, in medical technology and in quality assurance.

Why equip ceramic furnaces with an infrared camera?

Infrared imaging also offers many advantages for dental ceramic furnaces. The temperature of the restoration is measured by the furnace software using a non-contact method. It determines the optimum predrying and closing parameters for each firing cycle. The temperature is measured directly on the surface of the restoration. The position of the furnace head and the heating energy is controlled fully automatically. As a result, furnace users have the following benefits:

• higher precision due to object-related temperature control;
• improved quality of the firing results of large restorations;
• the firing time of small restorations is reduced by 20 per cent.

Therefore, infrared technology offers dental technicians enhanced reliability, quality and efficiency.

Where is the infrared camera located within the ceramic furnace?

In the Programat P510, for example, the IR camera is located at the back of the furnace near the furnace head opening mechanism behind the cover. In order for the lens to detect the restoration, the cover plate has to have a corresponding opening. In this position within the furnace, the camera is protected from the heat in the firing chamber and optimally positioned to detect the chamber contents during the predrying process.

Since the camera cannot be located within the firing chamber itself due to thermal engineering reasons, an object’s temperature can only be measured with the furnace head open or closed to within 30 millimetres. The critical processes for the ceramic material take place during the predrying stage with an open furnace head. The IR camera is used during this phase.

How many pixels does the camera have? How many points can it measure?

The thermal images taken by the IR camera of the Programat P510 consist of approximately 1000 pixels. There will be at least 2 measuring points on a thin single veneer. A large molar may have 12 or more measuring points. The surface of a measuring point depends on the distance. Near the firing tray on which the dental restorations are placed, the surface area of a measuring point is always smaller than 2.5 mm x 2.5 mm.

What are the advantages of using infrared imaging in a ceramic furnace compared with using conventional thermal elements?

In conventional dental furnaces a thermal element measures the temperature within the firing chamber. This thermal element is usually located in the upper part of the firing chamber and the restoration is usually positioned at a close distance. The software measures the temperature on the restoration while the furnace is closed and a correction factor is subsequently applied. However, when the restoration is predryed while the furnace head is open, draughts can distort the temperature reading on the restoration and the thermal element. This may cause temperature deviations. The preset time (closing time and predrying time) will not make allowance for these variations and the program will run by default. The occurrence of cracks and fractures in the ceramic is inevitable.

In contrast, infrared imaging allows the temperature on the restoration to be measured with a non-contact method. The Programat P510 does not rely on a correction factor to estimate the temperature on the restoration when the furnace is open. The IR camera always measures the precise temperature on the surface of the restoration even if there is a draught. This represents the greatest and most decisive advantage over furnaces that operate with conventional methods.

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Source: R. Grünenfelder/J. Jussel: Special Update 12/2013

Programat® is a registered trademark of Ivoclar Vivadent AG. The availability of certain products may vary from country to country.