## 1 Introduction  
Rapid palatal expansion (RPE) is an orthodontic approach that addresses maxillary transverse deficiency by applying orthopedic forces to separate the midpalatal suture and open the circummaximillary sutures [1]. RPE has been reported to be effective in addressing transverse discrepancies in the dental arch [2,3], increasing nasal cavity volume [4], improving insufficient arch perimeter [5,6], and correcting posterior crossbites in the maxillary region [7,8]. A conventional tooth-borne rapid palatal expander directly transmits expansion forces to the dentoulveolar structures using teeth as anchorage. With increasing age, the midpalatal suture exhibits a more interdigitated pattern, resulting in greater suture resistance to expansion forces [9,10]. The application of tooth-borne expanders may lead to undesirable dental effects, including the buccal inclination of posterior teeth, reduction in the thickness of buccal alveolar bone, and root resorption on the buccal aspect, thereby potentially limiting the effectiveness of RPE [11, 12, 13]. Therefore, a thorough assessment of the patient's skeletal maturity is crucial prior to RPE treatment, emphasizing that appropriate timing is a critical factor influencing treatment success. In order to prevent such complications, surgically assisted RPE (SARPE) is commonly advocated as a suitable alternative method to CRPE for achieving maxillary expansion in late adolescent and adult patients [14]. SARPE is generally considered a simple and safe procedure with relatively low risks. However, various complications have been documented. Severe complications include potentially life-threatening vascular and neurological events [15]. Additionally, milder postoperative issues, such as pain, periodontal problems, asymmetry, incorrect expansion, sinusitis, and relapse, have also been reported [16]. These complications, along with surgical complexity and high costs, may restrict the clinical application of this technique [17]. Recently, miniscrew-assisted RPE (MARPE) has emerged as an effective non-surgical alternative for correcting transverse maxillary deficiencies in late adolescent and adult patients [18]. This approach typically employs either a tooth-bone-borne-anchored or exclusively bone-borne-anchored rigid appliance connected to miniscrews penetrating the palatal cortical bone, allowing for the direct transmission of orthopedic forces to the basal bone. Consequently, MARPE promotes parallel skeletal expansion along the midpalatal suture [19]. Compared to CRPE, MARPE offers reduced biological risks, lower financial costs, and fewer dentoulveolar side effects [20]. According to a finite element analysis performed in young adults, MARPE demonstrated a more uniform distribution of stress compared to CRPE, resulting in a reduction of undesirable dentoulveolar effects [21]. The success rate of midpalatal suture separation using MARPE has been reported to decrease with advancing age [12]. However, other studies have found that age does not significantly influence outcomes [22]. Histologic studies have led to consensus that CRPE is appropriate for palatal suture separation in patients younger than 15 years [9,10]. A recent meta-analysis involving late adolescents and adults demonstrated that MARPE led to a significant increase in dental tipping and a decrease in buccal bone thickness and alveolar bone height [23]. In comparison, a study in growing patients revealed that although MARPE caused less reduction in buccal bone thickness than CRPE, the difference was not clinically significant, and both modalities were considered safe for the alveolar bone morphology [24]. In contrast, [PERSON] et al. reported that MARPE resulted in less buccal bone thickness reduction in the premolar region compared to CRPE. However, their meta-analysis did not stratify outcomes according to age group [25]. These findings collectively underscore the need for age-specific evaluation of dentoulveolar outcomes in MARPE application.