The differences in children’s stress reaction based on salivary alpha-amylase activity were examined using a digital impression or alginate impression. Salivary alpha-amylase activity was measured by an enzyme analyzer just before the start of therapy, just after talking the impression, and after the end of the treatment period. The TRIOS^®3 intraoral scanner was used for taking digital impressions. As a result, the alginate impression group showed significantly increased alpha-amylase activity just after taking the impression in comparison with the digital impression group. There was no significant difference between just before the start of therapy and after the end of the treatment period. Therefore, salivary alpha-amylase activity measured by digital impression was lower than that by the conventional impression. These results suggest that digital impressions could reduce the stress for children caused by the impression-taking procedure.