Pressure Pain Threshold of the Posterior Aspect of the Temporomandibular Joint Measured with a Semi-Spherical Probe

Aims: To develop and test a probe for measurement of the pressure pain threshold (PPT) over the posterior aspect of the temporomandibular joint (TMJ) in healthy individuals, including determination of PPT levels, reliability, and the smallest detectable difference (SDD) between measurements. Methods: A semi-spherical probe was designed to measure PPT levels over the posterior aspect of the TMJ through the external auditory meatus. The probe was connected to an electronic algometer. Three consecutive measurements were performed with this probe over the posterior and lateral aspects of the left and right TMJs as well as over a reference point on the forehead (glabella) in 31 healthy subjects: 10 male and 21 female. Measurements were also performed for comparison with a conventional flat probe with a 1 cm2 area over the lateral aspect of the TMJ and the reference point. Results: The PPT measured with the semi-spherical probe and the conventional probe showed similar degrees of interindividual variation and reproducibility. The relative SDD, expressed as the percentage of the mean PPT for 2 measurements, showed similar levels for the flat and semi-spherical probes, ie, 28% to 32% of the mean PPT at the TMJ. Conclusion: The semi-spherical probe shows similar reliability and relative SDD for measurement of PPT levels over the posterior aspect of the TMJ in healthy individuals as measurement over the lateral aspect with a flat probe. Measurement of the posterior PPT with a semi-spherical probe may be a useful adjunct to conventional lateral PPT measurements. Keywords: algometer probe, healthy, pressure pain threshold, smallest detectable difference, temporomandibular joint