## 1 Introduction  
Innovative materials and technologies that improve treatment outcomes while reducing morbidity and biological and surgical times are contentious issues in dentistry [1]. Endosseous implants are used in a variety of ways, from the restoration of missing teeth to the absolute anchor in the orthodontic field. In particular, the intraosseous mini-implant in the field of orthodontics broadened the treatment range of non-surgical orthodontics and increased the effectiveness of orthopedic treatment. Maxillary transverse deficiency is a common orthodontic condition that may cause posterior crossbite and unstable occlusion [2, 3]. Various tooth-borne appliances have been created to correct maxillary constriction since the introduction of the Hass-type rapid palatal expander [4, 5, 6]. Young, growing patients with a maxillary transverse deficiency can be treated with various tooth-borne appliances because the midpalatal suture is not heavily interdigitated in these people [4; 5; 7]. However, in non-growing patients, it is difficult to obtain sufficient maxillary expansion with this type of appliance, and it can cause undesirable side effects, including unwanted buccal tipping, root resorption, buccal bone dehiscence, diminished skeletal effects of the expansion, loss of long-term stability and gingival recession [8; 9; 10]. In order to correct the transverse maxillary deficiency in skeletally mature individuals, surgically assisted rapid palatal expansion was proposed [11]. However, a lot of patients turned down surgical intervention due to high expenses, dangers, and complications, as well as surgical complexity and morbidity. Lately, mini-implant-assisted rapid palatal expansion (MARPE) has been suggested as an alternative to surgically assisted rapid palatal expansion [12], and many studies have reported successful maxillary skeletal expansion in young adults using MARPE [13; 14; 15; 16]. Orthodontic mini-implants have been recommended as a skeletal anchorage for RPE in order to offer greater orthopedic expansion while minimizing unwanted side effects [15; 17]. Due to this, good skeletal expansion can be obtained even in adults with mature sutures. According to its shape, MARPE can be divided into a bone-borne type that uses only a skeletal anchor and a hybrid type that uses both a skeletal anchor and a tooth anchor. A maxillary skeletal expander (MSE) is one of the hybrid-type MARPE devices with four mini-implants positioned more posteriorly to maximize the possibility of bicortical engagement into the palatal bone and nasal floor [18]. MARPE increases the possibility of non-extraction treatment by creating extra space [19]. However, in the case of severe crowding or lip protrusion, a significant amount of retraction of the maxillary incisors may be required along with MAPRE. Recent studies have reported the increased risk of external apical root resorption when roots contact the incisive canal (IC) [20; 21; 22]. A strong cortical bone surrounds the IC, which is situated posterior to the roots of the central incisor on the median plane of the palatine process of the maxilla [23; 24]. It carries the maxillary artery, branches of the trigeminal nerve's maxillary division, and nasoplatine arteries and nerves [24; 25]. The palatal cortical plate is thought to be the anatomical limit of maxillary incisor retraction. The IC, another anatomical component, runs parallel more closely than the palatal cortical plate to the maxillary incisor roots between the central incisor roots in the median plane. Due to its closeness to the maxillary incisors, there is a chance that the IC may be invaded during dental treatments. Although the dental and skeletal effects of MARPE have been variously studied [15; 26; 27], there is no study confirming the effects on the IC morphology and tooth-canal relationship.