## 1 Introduction  
Orthodontic treatment of class II and III skeletal malocclusions, both through camouflage and orthognathic surgery, is associated with appropriate orthodontic preparation involving proclination (labial movement), lingual movement, retraction, or torque movements of the upper incisors. Since all these manipulations occur in the anterior segment of the maxilla, the anatomy of this area is of key importance in the diagnosis and planning of orthodontic movements that will not violate the bone envelope of this section and will not lead to the direct contact of the maxillary incisor roots with the palatal/vestibular cortical bone or the cortical bone of the incisive canal. Previous studies by other authors have shown that such contact may cause complications such as incisor root resorption, and dehiscence and/or fenestration [1; 2; 3; 4; 5; 6]. A systematic review found that the risk of incisor root resorption is increased by root contact with the incisive canal [5]. Accurate diagnostics based on 3D imaging are needed to assess the diversity of the morphology of the incisive canal and its relationship with the incisor roots.  
The incisive canal serves as a communication between the oral and nasal cavities. It ends in the oral cavity in the incisal fossa below the incisive papilla, immediately behind the upper central incisors [6]. It is surrounded on each side by thick cortical bone and contains nerves and vessels supplying the upper incisors and the anterior part of the palate. The assessment and knowledge of the anatomical features of the incisive canal, its structure, size, and changes in inclination depending on age, sex, as well as parameters determining the position of the maxillary incisors, can help effectively prevent severe complications of orthodontic treatment, such as root resorption. These need investigation due to the insufficient assessment of this region on routinely performed panoramic radiographs and cephalometric images [7].  
The growth and development of soft and hard tissues are closely function-related. Since the skeletal unit is responsible for protecting and supporting the functional matrix, the size, shape, and position of anatomical structures change in order to meet the functional needs [8]. Therefore, it is very likely that the anatomy of the incisive canal may depend on age, sex, position of the upper incisors, direction of facial growth, and muscle activity. It may also be more or less susceptible to reconstruction and remodelling resulting from orthodontic manipulations, depending on parameters such as age, sex, or applied orthodontic forces [1].  
As a result of advances in 3D imaging in recent years, publications showing the morphological diversity of the incisive canal have appeared. However, their results are ambiguous. Some studies [8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19] indicated a significant impact of sex, age, and growth direction on the anatomical and morphometric features of the canal, supporting the need to consider the risk of complications when planning orthodontic and surgical interventions involving the anterior maxilla. However, others [6; 7; 20] have not shown such a relationship. Therefore, prior to orthodontic range of motion planning, it is important to identify high-risk patient groups that require thorough diagnostics, including CBCT of this segment, to minimise this risk. For years, there has been a debate as to whether CBCT should be performed before orthodontic treatment. Risk analysis in individual age and sex groups may answer the question of whether such an extended diagnosis is indicated.  
Cephalometric images are routinely used in orthodontic treatment planning, especially to assess the anterior-posterior relationship where the ANB angle is considered the gold standard in assessing the sagittal-mandibular relationship [21]. However, neither this nor a panoramic radiograph is sufficient to illustrate the area of the incisive canal in relation to the upper incisors.