Producing Stress Analysis from Strain data

I am doing research on the stresses that are produced when a retainer (a thermoplastic sheet) is placed on the teeth. We've designed the project so that we take an initial scan of the sheet and a final "shifted" scan of the sheet. We'd like to compare, find the strain, and calculate the stress neccessary to produce this strain.

I was hoping to use FEA for this...is it possible? I have access to Abaqus and Ansys, and where can i find the commands that allow me to do this.