## 2 Materials and Methods  
In November 2022 two patients with breathing problems during sleep were seen at the institute of Otorhinolaryngology (Department of Head and Neck Surgery, \"A. Gemelli Hospital\", Catholic University School of Medicine and Surgery, Rome, Italy). All the usual diagnostic and interventional steps foreseen for this pathology were followed. The patients were a 57-year-old female, with BMI 24.61, and Epworth index 9, and a 57-year-old man, with BMI 24.34 and Epworth index 1. From the ortholinolaryngoatric examination, the female patient presented an oral cavity with a normal appearance, motility of the lingual and veil within the limits, Mallampati Friedmann type III. Furthermore, a modest deviation of the nasal septum to the left, hypertrophy of the inferior turbinates and free nasopharynx were observed, with a slightly hypertrophic base of the tongue, normal shaped epiglottis, glottic plane within the limits of morphology and motility, good respiratory space, free piriform sinuses and slight retrocricoid edema from laryngopharyngeal reflux. At the Muller maneuver, the oropharyngeal retropalatal space was reduced by 40%. The Dynamic Polygraphy performed with the Nox T3 Polygraph (MedicAir Italia Srl., Via Monte Rosa 61, 20149 Milano, Italy) gave the following results: presence of some pathological respiratory events, obstructive apneas and hypoapneas, collected in clusters. The AHI was 6.5 events/hour (supine AHI = 11.1 events/h), associated with falls in hemoglobin saturation. The ODI was 6.5 events/h, almost constantly within the normal range (T90 = 0.2%), with a mean desaturation of 93.2% and mean saturation of 95.5%. There was associated snoring of a marked entity, which, coincident with the pathological respiratory events, was of the intermittent type, and considerable heart rate variability was recorded. The second patient was a 57-year-old man with mild OSAS with a positional component. At the examination, the patient reported that he had been suffering from OSAS and snoring for years. Anterior rhinoscopy showed clear nasal passages, an irregular septum and bilateral inferior nasal turbinate hypertrophy. Mallampati was II-III, and the tongue, epiglottitis and mucous membranes were normal. The glottic plane was within the limits of morphology and motility, with good respiratory space and free piriform sinuses. The Dynamic Polygraphy performed highlighted the presence of some pathological respiratory events, obstructive, central apneas and hypoapneas, collected in clusters and present above all in the supine position. The AHI was 12.9 events/h, but in the supine position, it was 24.7 events/h. It was associated with a fall in maximum oxy-hemoglobin saturation of 89% and mean of 92.4%, with mean saturation of 94.9% and an ODI = 12.9 events/h. Snoring was marked and related to the supine position, and considerable heart rate variability was observed. The results allowed for the classification of the patients as mild-to-moderate OSAS (AHI \(\geq\) 5 to \(\leq\)30/h of sleep). From the results of the tests performed, the DISE and the visit with the orthodontic specialist were scheduled to assess whether there were conditions for the construction of a MAD. Patients were informed of the purpose of the dental examination, which serves to establish the oral health status necessary for the application of the MAD. Furthermore, the need to take the bite registration in an advanced position was explained to the patients, which is necessary for the construction of the individual fork to be used during the DISE for the advancement maneuver. All patients were willing to participate and gave their consent. The outcome of the orthodontic visit for the female patient highlights the presence of a Class 2 malocclusion with a deep bite. The state of health of the teeth and of the periodontitis was good.