# Cephalometrics in Obstructive Sleep Apnea Patients with Mixed Dentition
## 4 Discussion  
This is the first study to analyze polysomnographic and cephalometric characteristics and contributors on positional and REM dependency in patients with mixed dentition and varying degrees of severity of OSA. A correlation analysis was carried out between the parameters of the sleep cycles (REM sleep) and the airway space at the level of PAS1, PAS2, and MPH (the distance between the mandibular plane and the hyoid).  
According to night polygraphy data, the subjects were divided into subgroups based on the severity of pediatric OSA. Snoring was detected in 7 children, severe OSA was diagnosed among 4 children, moderate OSA among 10 children, and mild OSA among 18 children.  
During comparison of polysomnographic parameters in children with different severities of OSA, significant differences in AHI, ODI, and non-supine AHI were revealed in almost all groups.  
There were no differences in these parameters between subgroups of children with severe OSA and moderate OSA.  
The REM sleep was significantly higher in the subgroup of children with severe OSA compared with patients with mild OSA.  
Cephalometric parameters showed no significant differences between the groups of patients with snoring and moderate OSA, and mild and moderate OSA. However, between groups of patients with snoring and mild OSA, there were significant differences between MnPl and MxPl. Significant differences were observed between BaSN values (the angle of the posterior cranial base) between the subgroups of patients with moderate OSA and mild OSA with the group of patients with severe OSA and ANSPNSSSPT in the same subgroups.  
In the comparison of cephalometric parameters, a significant difference between PAS 2 (posterior airway space at the level of the occlusal plane), PAS 3 (anterior-posterior pharyngeal size at the level of the mandibular plane), SNA, MnPLSN, and ad2 (distance from the PNS point to the nearest point of the adenoid tissue) was observed in subgroups of children with mild OSA and severe OSA. The difference between PAS 2, PAS 3, and ad2 was also observed between groups of children with mild OSA and severe OSAS. Obtained data were comparable with the study results of [PERSON] et al. [26] and [PERSON] et al. [27].  
The PAS1, PAS2, and ad2 parameters were negatively correlated with the REM sleep phase, and ad1 was positively correlated with NREM1 (the parameter correlation was statistically significant).  
A moderate correlation was found between the MPH (the distance between the mandibular plane and the hyoid) and the NREM2 and NREM3 sleep stages (r = \(-\)0.457; \(p\) = 0.019; r = 0.409; \(p\) = 0.038, respectively).  
A 1.06 times increase in the SNA index indicated the anterior position of the upper jaw. [PERSON]'s class II skeletal form was also evidenced by an increase in the ANB angle by almost 2.3 times [8]. The SNB index was 1.05 times less than normal and indicated a more posterior position of the lower jaw. The angle of the lower jaw relative to the base of the skull exceeded the norm by 1.3 times, which also indicated the posterior position of the lower jaw and the vertical type of growth of the facial skull. The decrease in the U1 NA angle was almost 1.2 times. According to the literature, a decrease in this angle below 22\({}^{\circ}\) also indicates II class 2 nd subclass according to the angle. An increase in the ANSPNSSPT angle by 1.1 times from the norm indicated an inclination of the upper jaw in the posterior position and a decrease in the nasal passages.  
The MSPT data indicated a normal soft palate thickness. A decrease in EbTt by 1.4 times indicated a decrease in the airway space. Thus, patients with pediatric OSA had a significantly smaller lower airway space and MPH parameter.  
The main limitation of this study was the small number of participants in each group. The race of participants was Armenian.