Measurement of the Physiological Mobility of Individual Teeth in an Axial Direction

Forces such as those produced during the mastication of food cause the tooth to move in its socket. This movement is resisted by the resiliency of the tissues surrounding the tooth, particularly those comprising the periodontal membrane. Although lateral movements have been measured by Muhlemann'-8 and others, only a few devices have been described that are capable of measuring the small physiological axial tooth movements. Zwirner9' 10 described a method utilizing the movable plates of a condenser, one attached to the tooth to be measured and the other to the substance in which the jaws of a rat were imbedded. Picton'1 described a clinical method of measuring axial tooth movement by means of a resistance-strain gauge. One end of the gauge was attached to a single tooth and the other through a spring to the adjacent teeth. Axial movement has been studied because direct measurement of tension or compression of tissues can be made as the tooth can be moved bodily in this direction without tilting, so that all points on the tooth move the same amount and in the same direction. The points of application of the measurement devices are, therefore, not critical.