BACKGROUND A clinical assessment of the masticatory performance of edentulous people treated with bimaxillary implant-supported fixed prostheses is lacking. OBJECTIVE The purpose of this case-control study was to compare the masticatory performance of edentulous people treated with bimaxillary implant-supported fixed prostheses to that of those with a natural dentition by using a simplified comminution test with hard viscoelastic test food and a mixing ability test. METHODS Thirty-six participants were recruited and divided into 2 equal groups (n=18) based on their dental status. The experimental group (7 women, mean ±standard deviation age=69.8 ±7.5 years) had bimaxillary implant-supported fixed prostheses, and the control group (9 women, mean ±standard deviation age=68.3 ±5.6 years) had a natural dentition. A hard viscoelastic food comminution test and a mixing ability test with 2-colored chewing gum were performed in both groups. The number and total area of the particles during the comminution test and the variance of hue during the mixing ability test were measured. The data were analyzed with the parametric (paired t test) and nonparametric (Mann-Whitney U) tests to assess differences between the groups (α=.05). RESULTS The experimental group exhibited significantly fewer pieces in the food comminution test than the control group (P=.001). The experimental group also showed significantly higher variance of hue values than the control group (P<.001). CONCLUSIONS Patients treated with bimaxillary implant-supported prostheses had reduced masticatory performance in comparison to those with a natural dentition, despite having been provided with satisfactory and well-functioning prostheses.