## 4 Discussion  
NE is a common condition among children with breathing problems and the relationship between sleep-disordered breathing and enuresis has been discussed for many years [26]. Several studies reported enuresis in children suffering sleep apneas or heavy snoring becoming dry when their airway obstruction was treated [27; 28]. One epidemiological study indicated that more children with NE were at high risk of SDB (13.6%) compared to the mean prevalence in the orthodontic population (10.3%), with this difference being statistically significant [29]. In the present study, of the 23 NE patients who filled in the PSQ, 13 patients had a PSQ score characterizing them as at high risk of SDB (56.5%). This supports the hypothesis that children with bedwetting have a significant higher chance to present SDB problems, which thus should be looked for. If SDB is the background for enuresis for some children, these children are expected to be refractory to first line treatment with desmopressin and an enuresis alarm. In the current study, only one child had not been previously treated; two patients were refractory to the enuresis alarm, two failed a desmopressin (Minirin) treatment, and one was refractory to both alarm and desmopressin. To the best of our knowledge, there are ten studies dealing with the effect of RME on NE: nine of ten studies treated children characterized by normal transverse dimensions with expansion therapy, with the only aim being the cessation of NE [12; 14; 19; 20; 30; 31; 32; 33; 34]. A 100% relapse of the dental overexpression was assumed. On the contrary, in the present study, to be included, all the patients had to be diagnosed with a constricted palate, as it was considered inappropriate, potentially atrogenic, and ethically questionable to over-expand patients without a constricted maxillary. All the patients of the present study were treated with a hyrax-type palatal expander using a CAD/CAM procedure. This fully digital approach was chosen as it was shown to be precise, quicker to put in place, and does not require the use of separators [23]. The amount of maxillary expansion was in the range of 3.5 to 4.5 mm, which was more limited compared with previous studies [19; 35]. Figure 6: The average of night voided volume per week for the patients at the three time points. [PERSON] reported that the amount of expansion varied from 6 to 10 mm [35]; two studies reported a 5-8 mm expansion [30; 33]. [PERSON] et al. checked the interplanar distance and the change was 5.7 mm after RME [34], which is larger than the result of the present study. As relief of breathing problems could help the children with NE, the hypothesis was raised that RME could be related with resolution of bedwetting in some patients. In 1990, [PERSON] first published a paper to test this hypothesis. All the ten patients in his study became dry at night following treatment [35]. [PERSON] et al. reported significant improvement with respect to NE after RME and became completed dry after 3 years (19 patients, aged 6-15 years) [14]. In the present study, four out of six patients had a decreased amount of nocturnal urine production. The number of included participants was too low for statistical analysis as this was a pilot study; however, it seems that, in responders, nocturnal urine production was reduced following RME, and the reduction in frequency of bedwetting seemed associated with this reduction in nocturnal urine volume. The effect of RME on NE was based on the possible relationship between breathing patterns and NE. Therefore, before and after RME treatment, CBCTs were taken to assess the morphological changes in the nasal cavity (NC) and pharyngeal airway (PA). The CBCT results showed that two patients displayed a large volume increase in NC and PA. According to these results, we hypothesized that the greater the expansion, the greater the effect on NE.