## 4 Discussion
The present retrospective study wanted to further investigate the possibility of obtaining beneficial effects on obstructive and non-obstructive pediatric oral respiratory patients with concomitant upper jaw contraction through the use of an RPE. The sample examined appeared to be mostly affected by obstructive respiratory disease, so as to favor oral breathing. Second, we aimed to explore the treatment potential available to the orthodontic specialist, who increasingly assesses patients with interdisciplinary problems. Since the scientific evidence [36] shows that the skeletal and dento-alveolar effects of RPE are more significant when treatment is undertaken before the peak of pubertal growth, it was decided to include only growing patients aged 5 to 12 years. The current study group, consisting of 42 individuals with a mean age of 7.7 years, was not evenly distributed by age. The reason lies in the scientific evidence: depending on the age of the subject and the sutural activity present, there is a variable amount of orthopedic expansion. This variation is related to the fact that the resistance to maxillary expansion increases with sutural activity and thus the extent of expansion decreases as the degree of skeletal maturity increases [37; 38]. For this reason, the literature agrees in emphasizing the importance of early treatment with RPE in order to maximize the magnitude of skeletal expansion in the presence of a perfectly adaptable palatine medial suture [39]. The results obtained from the AAR show a reduction in nasal resistance to airflow, confirming the findings achieved by the previously mentioned studies. In particular, the airflow varied in a statistically significant manner (\(p\)-value = 0.00) with an improvement that is similar for both nostrils, although showing slightly higher, by about two percentage points, on the right nasal side (Figure 3b). Regarding the subjective perception of the patient and parents about the possible improvement in nasal breathing, quality of sleep, and daytime behavior, no statistically significant results emerged with the two questionnaires employed, SRDB and PSQ-SRDB. In fact, in no case did a subject in the study group score equal to or higher than that considered,based on the literature, to be significant for OSAS. On the other hand, evaluating the change in the overall score between T0 and T1, the PSQ-SRDB shows a reduction in the same in 67% of the cases, while in 33% the final score appears even increased (Figure 5). Relative to the SRDB scale, assessing the change in the final score between pre- and post-treatment, it appears reduced in 49% of cases, unchanged in 31%, and increased in 20% (Figure 4). As is well known, obstructive sleep apnea syndrome (OSAS) in childhood is a severely underdiagnosed condition. Confirmatory PSG is held to be the gold standard [15,16] to diagnose this syndrome; however, it has numerous limitations. So, alternative tools are emerging, which include questionnaires. These simple, noninvasive, repeatable and reproducible devices can be the starting point for the correct diagnostic framing of the patient. Because they are filled out by the parent, they encourage more information about the disease, still burdened by general misinformation. In particular, the 22-item Pediatric Sleep Questionnaire shows the highest sensitivity for the identification of mild OSAS [40], as confirmed with the systematic review of [PERSON] et al. [41] and holds the best diagnostic accuracy. Another issue affecting this condition is the lack of a universally accepted classification for estimating the severity of pediatric OSAS. Many studies employ the apnea and hypopnea index (AHI) to classify the disease as mild (1 < AHI > 4.9), moderate (5 < AHI > 9.9), or severe (AHI > 10).