In dentistry, speech evaluation is important for appropriate orofacial dysfunction rehabilitation. The speech intelligibility test is often used to assess patients’ speech, and it involves an evaluation by human listeners. However, the test has certain shortcomings, and an alternative method, without a listening procedure, is needed. The purpose of this study was to test the applicability of an automatic speech intelligibility test system using a computerized speech recognition technique. Speech of 10 normal subjects, when wearing a dental appliance, was evaluated using an automatic speech intelligibility test system that was developed using computerized speech recognition software. The results of the automatic test were referred to as the speech recognition scores. The Wilcoxon signed rank test was used to analyze differences in the results of the test between the following 2 conditions: with the palatal plate in place and with the palatal plate removed. Spearman correlation coefficients were used to evaluate whether the speech recognition score correlated with the result of conventional intelligibility test. The speech recognition score was significantly decreased when wearing the plate (z = -2.807, P = 0.0050). The automatic evaluation results positively correlated with that of conventional evaluation when wearing the appliance (r = 0.729, P = 0.017). The automatic speech testing system may be useful for evaluating speech intelligibility in denture wearers.