Digital Speckle Shearing Pattern Interferometry (DSSPI) allows to directly quantify deformations in teeth that are
subjected to stress. Eighteen second premolars (2PM) were studied both before and after endodontic treatment made with
the ProTaper method in order to evaluate the variation of dental elasticity. We present a protocol for determination tooth
Apparent Young's Modulus (AYM). Each tooth underwent different flexion loads from 50 to 300 g. DSSPI technique,
makes it possible to show the deformation at each point of a line, selected by the researcher, that goes from the
attachment point (Point 0) to the root area where the load is applied (Point 300-350, depending on the tooth size). The
deformation of each tooth was characterized by the deformation value of point 150, located around the mid-area of tooth.
This value was obtained from a linear regression applied on the deformation values of all the points in the fitted line. The
correlation coefficients of these fitted regression lines were always higher than 0.972. The elasticity constant of each
tooth was obtained as the slope of a new regression line, corresponding to the different loads applied on the tooth versus
the corresponding deformation at point 150. This value, divided by the length of the tooth, is the apparent Young's
modulus (AYM), which is expressed in arbitrary units (a.u.). Values of the AYM before (4.16 104 a.u) and after
endodontic treatment using the ProTaper method (4.30 104 a.u.) showed no statistically significant difference in the
elasticity of teeth (p>0.7).