Digital Image Correlation and Strain Gauges to Map and Compare Strain in Teeth with Different Quantity and Quality of Remaining Tooth Structure

Purpose: To evaluate strain in teeth with differing quality and quantity of tooth surface loss by utilizing surface displacement field measured using digital image correlation (DIC) and strain gauges (SG). Materials and Methods: A total of 80 mesio-occlusodistal preparations were carried out in human maxillary premolars. Ten sound premolars served as a control group, and treated samples were divided into two groups of 40 each according to the composition of the prepared walls (composed of either enamel and dentin [E + De] or dentin only [De]). Each group was then divided into four subgroups of 10 each according to the selected cusp height-to-width ratio (A = 2:1 mm; B = 3:1 mm; C = 3:1.5 mm; D = 4.5:1.5 mm). The samples were uni-axially loaded to 130 N, and strain was recorded using DIC and SG. Results: With SG testing, control samples recorded the lowest strain values and were significantly different from all test groups. However, DIC failed to detect strain in control samples, as it was too low. With DIC, group D showed the lowest strain readings among all the dimension groups and was significantly different from groups A and B, but the composition of the remaining tooth structure did not show any significant effects. With SG testing, remaining wall dimension and composition both had significant effects: Group A scored the highest strain at all compositions, and E + De had better resistance to load stresses than De only. Conclusion: For both testing methodologies, height (≥ 3 mm) and width (1 to 1.5 mm) of the remaining tooth structure had an effect on strain. Tooth compositions of E + De resisted strain better than De counterparts at all dimensions.