26 Stomatologija, Baltic Dental and Maxillofacial Journal, 2021, Vol. 23, No. 1 ssEMG assessment of a new tool for the management of 3D vertical dimension of occlusion in prosthetic dental rehabilitations: A case report Riccardo Rosati 1 , Redento Peretta 2 , Francesco Rosati 3 , Federica Musto 1 , Claudia Dellavia 4 SCIENTIFIC ARTICLES SUMMARY In oral rehabilitation the new dental morphology requires changes in the occlusal relations and in case of whole dental arch restoration also the mandibular position can undergo three- dimensional spatial modifications. Overloads and/or altered distributions of the stresses on the temporomandibular joint, teeth and bones may therefore result with not clearly understood consequences. In the present case report a new tool -Vertical Tester- designed to manage the 3D vertical occlusion during an implant retained full mouth rehabilitation was combined with standardized surface electromyographic (ssEMG) analysis in order to respect the masticatory muscle symmetry and coordination. The Authors conclude that the standardized surface electromyography of the masticatory muscles coupled with custom made centric relation registration device is an easy to use proce- dure to reduce torsional strains on the oral hard structures. Key words: dental occlusion, prosthetic rehabilitation, electromyography, dental implant. CASE REPORT Stomatologija. Baltic Dental and Maxillofacial Journal, 23: 26-32, 2021 1 University of Milan, Milan, Italy 2 Private practice, Vicenza, Italy 3 Private practice, Udine, Italy 4 Department of biomedical, surgical and dental sciences, Uni- versity of Milan, Milan, Italy Address correspondence to Riccardo Rosati, via Luigi Mangiagalli 31, 20133 Milano, Italy. E-mail address: riccardo@riccardorosati.eu INTRODUCTION During adulthood, after childhood and adoles- cent development, all parts of the face continue to modify (1-3) and the masticatory performance too (4, 5). If physical and chemical mechanism like stress, friction, and corrosion exceed the adapta- tion capacity of the system, a pathological process can occur causing extensive destruction of patient’s natural tooth morphology and its supporting struc- tures (6). Altered dentition due to traumas, caries, tilted, drifted, rotated or malpositioned teeth results in compromised aesthetics, phonetics and mastica- tion (7). When an oral rehabilitation is approached, prosthetic dental reconstructions are often used to restore lost masticatory units, recreate compro- mised dental structures or replace incongruous prostheses. The new morphology requires changes in the occlusal relations and in case of whole dental arch restoration also the mandibular position can undergo 3D spatial modifications (8, 9). Occlusal morphologies that are not adequately designed and positioned may therefore alter the muscle generated forces distribution causing changes on temporoman- dibular joint, teeth and bones loads (10, 11) with not clearly understood consequences. Also neck muscles recruitment can suffer changes in teeth-perio-bone proprioception (12-14). These iatrogenic changes are perceived by the proprioceptive system requiring a functional adaptation to reduce the overload to the hard structures. If the posterior occlusal areas are not sufficiently sized (Fig. 1), an overload of the temporomandibular joint may occur together with a reduction of some masticatory muscle per- formance. This functional adaptation pattern is not proven to remain stable over time and during the day- and night-time parafunctional activities and the consequences of altered muscles behaviour on facial morphology are not completely understood (15). It should also be underlined that the selec- tive (non-uniform and homogeneous) inhibitions of the masticatory muscles can establish the onset of torsional stresses during maximum clenching, reaching not easily evaluable forces. Indeed, as reported by Koyano et al. (16), the “‘indirect’ meth- ods, that is, improving function by providing an appropriate morphology, are nevertheless superior to other prostheses, such as eye prostheses, that are