###### Abstract
It is contraindicated in the presence of certain conditions, specifically: (1) an inadequate number of teeth to serve as anchorage; (2) ongoing periodontal disease; (3) existing temporomandibular joint disorders; or (4) a limited capacity for mandibular protrusion, defined as less than 6 mm [11]. Overall, while MAD therapy is characterized by suboptimal efficacy, therapeutic effectiveness is favored by high patient compliance [8]. The mechanism of action of MAD is to keep the mandible forward, improving upper airway patency and decreasing pharyngeal collapsibility during sleep [12; 13]. MADs may be employed as a standalone therapy or as an adjunct to other treatments that, in isolation, fail to achieve optimal therapeutic outcomes [12; 14; 13]. Additionally, MAD can be used to lessen the pressures during CPAP therapy, thereby enhancing patient compliance. Drug-induced sleep endoscopy (DISE) has been progressively advocated as a useful assessment to help determine the most suitable treatment option for the individual patient seeking an alternative to CPAP therapy [15]. This procedure provides a dynamic assessment of the upper airway to determine the level and the pattern of upper airway collapse. This is achieved through the use of a flexible nasopharyngeal possible while the patient is under sedation [16; 17]. The evaluation of the upper airway obstruction levels is generally assessed by using the vote (velum, orophnx, tongue base, epiglottis) classification that allows for the description of levels and structures that may be involved in the upper airway obstruction [15; 18]. For each level, the degree of obstruction can also be reported as complete, partial, or none. Notably, there are no significant differences in respiratory parameters or the sites of upper airway obstruction when comparing natural sleep to drug-induced sleep [19; 20]. Various mandibular advancement maneuvers have been documented in conjunction with DISE as a means to discern the individual patient's responsiveness to MAD therapy and thereby contribute to a more targeted treatment plan. However, the need for standardization of the diagnostic maneuvers during DISE has been widely recognized [16]. The use of manual maneuvers is not recommended due to the risk of awakenings during DISE and, also, because they may not accurately resemble the real effect of a MAD. Simulation bites or provisional devices have also been proposed, but the use of titratable MAD simulators is desirable in order to perform an intra-operatortitration to observe the response of the upper airway at various stages of protrusion and to identify the less protruded position effective for each patient [21]. A recent study investigated the locations and degrees of upper airway collapse at various mandibular advancements during DISE using a selector advance mandibular device in 161 snoring and OSA patients; however, it failed to evaluate collapse patterns, which are important for identifying phenotypes. The study included both snoring and OSA patients [22]. The primary objective of this study was to compare the general, polygraphic, and endoscopic characteristics between responders to advancement with a titratable mandibular advancement (TMA) simulator during DISE and non-responders. A further aim was to describe the sites (velopharyngealrx, orophnx, tongue, epiglottis), degrees (none, partial, complete), and patterns (latero-lateral, anteroposterior, circular) of upper airway collapse in the baseline patient's condition and with TMA simulator in situ.