Development and Application of an Orthodontic Photometer and Thermometer to Monitor the Effect of Near Infrared Light on Root Resorption and Orthodontic Tooth Movement

Abstract

The chapter describes the development, calibration and testing of a custom made photometric-thermometric sensor used to measure the penetration of NIR radiation from an intraoral therapeutic LED source, and the resultant temperature increase in tooth sockets. The use of NIR light to aid with bone resorption and tooth movement is a relatively new technique used to hasten tooth realignment after an orthodontic procedure. One of the unanswered questions in this application is whether there is sufficient light penetration through the tissue and bone into the tooth socket, from an external array of LEDs to have the required effect. The difficulty of conducting these measurements from within a tooth socket is due to the small size of the sensor required. However a judicious choice of probes enabled successful development, calibration and in vivo testing to take place. Measurements on the full cohort of 18 patients (36 measurements in total as each patient had two teeth removed) showed much higher attenuation than expected through to the socket. The attenuation was found to be strongly correlated to the bone thickness with an attenuation coefficient close to that of haemoglobin, implying that the in vivo bone is saturated with blood. Apart from photometric and thermometric data the heart rate of the patients was also apparent, due to swelling of the capillaries in the gum tissue during systole—the contraction phase—of the cardiac cycle.