STANDARDIZED ELECTROMYOGRAPHIC INDEXES ALLOW A RELIABLE MEASUREMENT OF MASTICATORY MUSCLES FUNCTION
recruitment . This performance alteration hesitated in a torque effect during maximal voluntary clenching ( Torque index -20 %). The Impact index confirmed that the occlusal condition needed muscular adaptation ( while clenching in maximal intercuspation , the muscles performed only 51 % of electrical activity developed while clenching with cotton rolls ). After a detailed explanation of the clinical and instrumental conditions , the patient agreed to rehabilitate her first and second right mandibular molars with overlays , changing her right posterior occlusal support . During the final impression taking appointment , a stiff flat resin jig was set on reduced tooth substance to slightly increase the posterior vertical dimension . A sEMG acquisition was made , and the patient was invited to perform two maximal voluntary clench : the first one with cotton rolls between the dental arches and the second one wearing the jig ( Fig . 4 ). Figure 5 shows that the torque effect was reduced ; muscular total work and Masseter coordination increased but did not reach physiologic values ( Impact index from 51 to 71 % and POC Masseter 78 %). The jig was then slightly reduced and retested obtaining a muscular recruitment very similar to those recorded in healthy young subjects with sound dentition ( Fig . 6 ) 24 , 41-42 . The new EMG tested mandibular position ( wearing the modified jig ) was used as occlusal posterior vertical index to produce the final indirect overlays .
During the subsequent appointment , the overlays were bonded in a dry setting and the function verified again acquiring muscle performance with the same standardized protocol . The new posterior occlusal morphology well integrated in the patient stomatognathic structures , and she had a good masticatory muscles coordination : her performance with the new dental surfaces well overlapped the “ occlusion-free ” reference test ( clench on cotton rolls ) ( Fig . 7 ). The functional test was satisfactory so reconstructions were accurately polished ( Fig . 8 ).
5 . Conclusions
Standardized sEMG indexes allow the evaluation of occlusal-induced proprioceptive mediated muscular recruitment in a reliable way . Merging biomechanical concepts with sEMG standardized indexes , occlusal devices and prosthesis adapting procedures could be clinically performed in order to reduce the muscular adaption to the new occlusal conditions or to reestablish physiological muscular coordination 45 .
Acknowledgments
The authors declare no conflict of interest related to this study . There are no conflicts of interest and no financial interests to be disclosed .
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