Mechanical allodynia, defined as a reduction in mechanical pain threshold, is an essential diagnostic feature of inflammation of the periodontal ligament. Traditional methods for measuring mechanical allodynia in a tooth are not quantitative. This study evaluated the reliability of a new bite force transducer to measure mechanical pain thresholds, which might have application as a quantitative diagnostic aid for measuring mechanical allodynia in patients with apical periodontitis. To determine inter-observer reliability, subjects (n = 40) were given standardized instructions before generating maximal bite force on maxillary first molars; readings were then recorded by three examiners for a total of ten readings per examiner. To determine the test-retest reliability, the initial examiner then retested at two different sessions. The intraclass correlation coefficient was fair to substantial for inter-observer reliability (0.3-0.64) and substantial for intra-observer reliability (0.63-0.68). Thus, the force transducer used in our study is a reliable method to measure mechanical pain thresholds in endodontic patients.