## 4 Discussion  
MARPE is a technique that has gained popularity for treating transverse discrepancies in adult patients where the midpalatal suture is already fused or presents significant resistance to conventional expansion [13]. One of the determining factors for the success of this treatment is the likelihood that the midpalatal suture will open adequately under the forces exerted by the MARPE device. In this context, studying the anatomy and bone density of the midpalatal suture is of vital importance in predicting the success or failure of the treatment [14]. This research aims to shed light on the success of midpalatal suture opening and its relationship to the variables of age, sex, and bone density calculated with CBCT UHs. The midpalatal suture is a key anatomical structure for maxillary expansion treatments. During development, this suture undergoes a process of synostosis or fusion, which varies with age and between individuals. In adolescents, the suture is not yet fully fused, which facilitates expansion with conventional appliances [13]. However, in adults, bone strength increases due to progressive ossification, which limits the effectiveness of traditional rapid jaw expansion treatments. The use of microimplants in MARPE helps to transfer expansion forces directly to the basal bone, increasing the likelihood of success, although the structure and density of the midpalatal suture remain important factors [15]. This present study indicates that younger patients, as well as those with lower HU values in the middle and posterior nasal spine (MNS and PNS), are more likely to achieve successful midpalatal suture (MPS) opening. Studies have shown that the anatomy of the midpalatal suture is highly variable, both in shape and the degree of ossification [16]. The morphology of this suture may influence the resistance to movement of the maxillary segments during expansion. Our findings regarding age are consistent with those found by [PERSON] [17], who argues that the midpalatal suture in adult patients has greater structural complexity, with areas of partial fusion and greater bone density compared to younger patients, making expansion more difficult and causing a higher risk of complications such as asymmetry in the suture opening. Additionally, no significant predictive factors for treatment success were identified based on patient sex. These findings align with the existing literature, which also reports no correlation between sex and the success of midpalatal suture opening in microimplant-assisted expansion treatments [14; 18; 19]. This lack of an association may be attributed to the substantial variability in suture consolidation between individuals. Different methods have been described to understand the individuality of the maturation status of the midpalatal suture: the obliteration index is not a valid factor to determine the type of expansion treatment in adults [15; 20]; midpalatal suture density (MPSD) is the method that has the potential to be used to clinically assess the skeletal response to RPE [21; 22], although other research does not recommend grey scale CBCT for the study of midpalatal suture bone density [23]. A key study in this field is that of [PERSON] et al. [15], which classified the midpalatal suture into different stages of ossification, using CBCT images to assess the likelihood of suture opening during maxillary expansion. Their classification ranges from stage A (no ossification evident) to stage D (complete ossification), with stage C being the point where suture opening is least predictable. This study highlights the importance of prior CBCT evaluation to determine the degree of ossification of the suture before deciding on the MARPE treatment protocol. Several studies have addressed the influence of bone density and midpalatal suture anatomy on the success of microimplant-assisted maxillary expansion. [PERSON] et al. [24]studied the relationship between cortical bone density and suture opening success in adults treated with MARPE.