## 1 Introduction  
Obstructive Sleep Apnea Syndrome (OSAS) is the most common sleep breathing disorder and reaches a frequency of 3-18% in men and 1-17% in women [1; 2]. OSAS is characterized by daytime sleepiness and/or impaired daytime performance and nocturnal snoring from a clinical point of view. During sleep, it is characterized by the appearance of repeated episodes of partial or complete obstruction of the upper airways associated with phasic falls in hemoglobin saturation from a pathophysiological point of view. The obstruction of the upper airways can be of various entities and multilevel and initiates various respiratory events. In the field of sleep disorders, we find many clinical pictures as insomnia, parasomnia, hypersomnia or excessive daytime sleepiness, restless legs syndrome, snoring, upper airway resistance syndrome (UARS), cot death syndrome, Pickwick syndrome and especially obstructive sleep apnea syndrome (OSAS), central, peripheral type and mixed [3]. Therefore, in addition to the nocturnal polygraphic examination, which remains the gold standard, it is necessary to identify reliable predictability screenings, such as composite questionnaires with anthropometric and clinical parameters, as well as biological markers, in order to then initiate sleep studies only for those most at risk [4]. Natural sleep endoscopy (NSE) is currently regarded as the gold standard of diagnostic tests to assess the site(s) of upper airway collapse. [PERSON] et al. described this procedure for diagnostic examination for the first time in 1978 [5]. During drug-induced sleep endoscopy it is possible to perform a mandibular advancement maneuver, called the jaw thrust maneuver. The purpose of the maneuver is to have indications on the possible outcomes of a symptomatic therapy of OSAS with oral devices for mandibular advancement (MAD) [6]. Mandibular advancement devices are custom-made appliances that can be used as a first-line treatment for mild-to-moderate OSAS patients [7]. To produce a mandibular advancement device, it is necessary to take a registration of the mandibular protrusion. To take the advancement record, the George Gauge(tm) (Great Lakes Dental Technologies, 200 Cooper Ave, Tonawanda, NY 14150, USA) is the most commonly used tool. The George Gauge(tm) allows for the millimeter measurement of the advancement and allows for the establishment of the height of the rise necessary for the thickness of the MAD, so that the patient can be in a comfortable position [8; 9]. The advancement of the initiation of MAD therapy is usually between 65% and 70% of maximal protrusion, and the mandibular forward position may be increased during treatment in cases of titratable devices [10]. The mandibular advancement with the manual maneuver during DISE fails to give information on the exact position obtained or on the possible discomfort that the patient could have in maintaining it during sleep. One way to get a more accurate assessment is to use a custom-made simulation bite. The simulation bite can be prepared by recording the exact advancement and thickness with the George Gauge(tm) or other systems that allow for an accurate measurement. In this way, both the mandibular advancement and the vertical mouth opening in the individualized therapeutic position can be recorded before the DISE. The mandibular advancement maneuver with the simulation bite provides more reliable predictions of the effectiveness of the MAD [11]. The advantage of using an individual simulation bite was demonstrated by [PERSON] et al. [12]. The procedure described for making the bite requires the use of a registration paste, to be applied on a preformed rigid support, which has the shape of the dental arch. This support can be called a bite fork. First, the position of the upper arch on the fork is recorded, and subsequently, that of the lower arch in the advanced position. The fork described in the article thus has two layers of paste, which are cured after registration and reproduce the indentation of all teeth.