Figure 3. HSP72 expression after HEMA and TEGDMA exposure as a percentage of the six-hour, no-resin controls (arbitrarily set to 100%). Cells were heat-stressed for 1 hr, followed by 2, 4, or 6 hrs of recovery. The letter ‘D‘ indicates a statistical comparison among the heat-stressed groups with six-hour recovery and various resin concentrations. Lower-case letters denote a statistical difference from the no-resin (upper-case) control (ANOVA, Dunnett's, = 0.05). The letter ‘C’ compares the four-hour recovery groups at various resin concentrations, whereas ‘B‘ compares two-hour recovery, and ‘A‘ compares the no-heat-stress groups.