A 2.00 mm circular spot was projected onto the bottom of the slide with varying intensity and exposure times. The uncured ink was rinsed off with isopropanol and the cured spot was dried with compressed air. The cure depth (Cd) of the material was measured using a digital caliper with a 0.01 mm precision. The Ec of each material could be determined from the Cd values at each energy via the Jacobs working curve.