Repeatability of a surface electromyography (EMG) protocol for the analysis of the Masseter and anterior Temporalis muscles during maximum clenching

Objectives The aim of this study is to assess the repeatability of a surface electromyographic (EMG) device designed for the analysis of the masseter and anterior temporalis muscles. Materials and Methods 30 TMD-free healthy individuals (20 females and 10 males; mean age 44 years, range 16–60 years) took part in the study and underwent three sessions of EMG recordings. Each trial consisted of two distinct recordings: i) the patient is asked to clench with maximum voluntary contraction (MVC), with two cotton rolls interposed between the dental arches; ii) the patient is asked to repeat the same clenching activity without the cotton rolls. The signal from the four electromyographic probes provides six indices based on the differences between the test on cotton rolls and on dentition. Recording trials were performed at five minutes intervals, with the patient sitting upright in a chair and without detaching the electrodes between trials. Results The Global Index, which comprehends the main parameter measured by the EMG, resulted to be the most reliable value. The POC MM and IMPACT indices showed weak-to-medium correlation levels between the three trials. Conclusions The investigation provided data on the correlation levels between different recording trials performed with a chairside EMG device. Findings showed a very wide range of correlation values for the various indices proposed by the manufacturer. Clinical Relevance The clinical usefulness of the applied protocol remains questionable. Further studies should test the repeatability of EMG findings gathered with this device under various circumstances, in a more heterogeneous population.