TEETH MOBILITY MEASUREMENT - A LASER VIBROMETRY APPROACH

Objective: This work presents a new technique based on the assessment of the mobility degree through the application of dynamic loads and th e measurement of the tooth displacement with a laser Doppler vibromete r, Snmmary Background Data; Measurements of the mobility degree have b een made, up to now, by the application of static loads and the measur ement of the consequent displacement. The results obtained with the me asurement technique proposed by Muhlemann (1967) have been validated b y O'Leary et al, (1964) and by Persson and Sweson (1980), This approac h, however, has not been clinically disseminated both because of the h igh cost of the equipment and, above all, because of the difficulty in performing the measurements. Methods: The ratio between the maximum o f the tooth displacement and the input force peak has been considered as the mobility degree index. Dynamic loads have been applied and meas ured on teeth, with a small hammer and a load cell. The consequent dis placement of tooth has been measured with a Laser Doppler vibrometer t hat allows easy to use and versatile noncontact measurements with high accuracy and sensitivity (<0.1 mm/sec), Results: An introductory in v itro study has been carried out on real teeth extracted and mounted on structures with different-stiffness silicone cast (stiffness of the s upport is one of the parameters responsible for teeth mobility), in or der to evaluate the technique. An in vivo study has also been carried out on different teeth of a healthy patient. It is possible to observe the agreement between the O'Leary results and ones obtained in this w ork. The practicality of the procedure has also been demonstrated. Con clusions: Good correspondence between data available in literature and results obtained has been demonstrated. The use of the technique here proposed could allow having a deeper knowledge of the behavior of the periodontal teeth system: the tooth mobility under dynamic loads. Wit h this new technique, it will be possible to quickly measure a patholo gical mobility of the tooth, before it becomes evident and problematic .