In groups QTH and LED the intrapulpal temperature increased by 6.4 degrees C and 3.4 degrees C, respectively. The difference between both groups was statistically significant (Mann-Whitney; P < 0.05). QTH and LED reduced the cell metabolism by 36.4% and 33.4%, respectively. Regarding the cell metabolism, no statistically significant difference was observed between both groups (Mann-Whitney; P > 0.05). However, when compared to the control, only QTH significantly reduced the cell metabolism (Mann-Whitney; P < 0.05). It was concluded that the irradiance of 0.5 mm-thick human dentin discs with a QTH in comparison to a LED curing unit promoted a higher temperature rise, which propagates through the dentin negatively affecting the metabolism of the underlying cultured pulp cells.