Use of the Krogh-Poulsen Test, Cone-Beam Computed Tomography, and Surface Electromyography in Distinguishing Muscular From Articular Temporomandibular Disorders

ObjectivesThe objective of this study is to assess whether the Krogh-Poulsen bite test agrees with cone-beam computed tomography (CBCT) and surface electromyography (sEMG) in distinguishing muscular from articular temporomandibular disorders (TMD). Materials and methodsThis prospective study included 88 consecutive adults with TMD seen between 1 June 2019 and 30 March 2022.Each side was classified as muscular or articular with the bite test.Condylar changes were graded on CBCT with the Koyama classification, and masseter and anterior temporalis activity was recorded at rest and in maximum intercuspation (MI).Condylar types were compared with an exact permutation chi-square test, sEMG parameters with Student's t-test, and one-way analysis of variance (ANOVA). ResultsThe mean age was 32.2 ± 10.1 years, and 55 of the 88 patients (62.5%) were men.The bite test was positive on 55 right sides (62.5%) and 63 left sides (71.6%).On the right, no muscular side (0/29, 0.0%) showed erosion or deformation, compared with 14 of 26 articular sides (53.8%) (χ²(4) = 21.7,exact p < 0.0001, and Cramér's V = 0.63).On the left, the corresponding figures were three of 27 (11.1%)and 21 of 36 (58.3%) (χ²(4) = 18.7, exact p < 0.001, and V = 0.54).Resting sEMG did not differ between groups.In MI, temporalis amplitude was higher on muscular sides (198.0 versus 161.2 µV; t(116) = 2.20, p = 0.030, and d = 0.41), whereas masseter firing rate was higher on articular sides (28.7 versus 21.1 Hz; t(116) = -3.59,p < 0.001, and d = -0.66).On the left, masseter amplitude in MI varied with condylar morphology (F(4, 58) = 3.53, p = 0.012, and η² = 0.20). ConclusionsThe Krogh-Poulsen test separated muscular from articular disorders in a way largely confirmed by imaging and electromyography.It may help to orient the indication for tomography, but because CBCT and sEMG were performed only on sides with a positive test, its use as a first-line triage tool requires validation against an appropriate diagnostic reference standard before it can be recommended in routine practice.