A generally valid and commonly accepted model for assessing the reliability of measurements in the field of medical and dental materials is hard to establish. The results obtained in different laboratories sometimes are difficult to compare. We therefore discuss different assessors of the quality of measurements from both conceptual and operational perspectives. Especially addressed are the customary terms accuracy, error and uncertainty, these terms that often are mixed rather confusingly in expressing the quality of experiments. The aim of this work is to present the advantages of choosing uncertainty rather than error as the appropriate assessor of the reliability of measurements. The transverse deflection testing of four denture-base acrylic resins served as an experimental basis for the analysis.