Thermography in Dental Practice

Thermography is not new in dentistry. The first articles about thermography in dentistry appeared in the 1970s but it has never been taken up as a useful adjunctive diagnostic tool in either hospital or general practice settings. A thermography camera picks up infrared heat emissions and displays the result in a coloured picture where each colour represents a certain temperature.

left dentalThermal image showing hotter area on left side of face. This could be a sinus infection or a dentally related infection or a skin infection. Controlling the variables eliminates errors such as sitting near a heat source, rubbing the cheek etc.

Thermography compares the right side with left side of the face. The reason for the difference in temperature now has to be investigated. It has always created controversy in the academic world and has not been generally accepted as either accurate or useful. However, recent advances in the technology of thermal cameras and their software have, in our view, rendered these objections invalid. Provided the variables are controlled as discussed below, we have found thermography to be both accurate and useful.

right dental

Patient right side of face

We were after a screening tool to look for NICO’s, (Neuralgia Inducing Cavitational Osteitis), cavitation infections and inflammations in the head and neck associated with infections.

X-Rays do not always show such pathologies, and ultrasound devices such as the Cavitat, although accurate, take time, are expensive and intrusive. We have used the Cavitat for ten years and have found it to be excellent at picking up structural defects such as chronic cavitation infections in the bone, but as a screening aid it has serious limitations.

Thermography picks up physiological and functional changes in tissues that occur before any structural changes can be seen. Thermography could be used to screen all patients; it can pick up pathological changes before any of the conventional diagnostic aids such as radiographs and ultrasound.

Thermography is non invasive, no ionising radiation is used, no physical contact is made with the patient and it can be used to detect inflammation and as a monitoring tool post treatment. These are distinct advantages over all other diagnostic systems. Thermography can only show radiant heat pictures with increased heat meaning inflammation. This can detect infection in the tissues is picked up earlier than with any other diagnostic aid as it shows physiological rather than physical or structural changes. Physiological changes always occur before physical changes.

In humans, radiation is the primary source of heat transfer and exchange to the environment. The infrared spectrum is from 0.8 microns to 25 microns. Human skin peak emission occurs at 9 microns and has an emissivity of 0.98 which is close to the emissivity of a black body at 1.0, so skin is close to the ideal emitter of infrared radiation. This makes thermography a good tool to use in the diagnosis and monitoring of pathologies.

Men are hotter than women interestingly enough from a thermography point of view, but absolute values are not used. Thermography uses comparative values. One side is compared to the other side and to adjacent tissues. In the head and neck, temperature differences up to 0.25ºC are regarded as normal. Up to 0.35ºC difference is equivocal, greater than 0.35 is a hot area, i.e. inflamed. Any area lower than 0.35ºC is regarded as a cold area.

In peripheral nerve mediated pain and mental or ID nerve damage the temperature is 0.5ºC lower than the contra lateral side.

In TMD syndrome, if the differential between the right and left TMJs is 0.4ºC or greater, this indicates a TMJ problem. It is an ideal way of monitoring progress in treating TMD. We have found this to be very valuable in practice. It is quick, easy and accurate.

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