## 1 Introduction  
One of the most critical reasons for endodontic treatment failure is the overlooked diagnosis of anatomical and morphological variations in the roots and root canal systems. A commonly missed variation, often found in maxillary anterior teeth--especially in maxillary lateral incisors--is the palatoradicular groove, which is a developmental anomaly that can pose significant challenges during endodontic treatment [1]. First described as a radicular groove by [PERSON] in 1908 [2], the palatoradicular groove (PRG) has since been recognized under various terminologies as the distolingual groove [3], developmental radicular anomaly [4], cinguloradicular groove [1], palatal groove [5], radicular lingual groove [6, 7], and palatoradicular groove [8], reflecting its complex morphology and clinical implications. The etiology of PRGs is multifactorial and remains unclear. Possible causes include enamel epithelium infolding, [PERSON]'s epithelial root sheath anomalies [9], variants of dens invaginatus or genetic factors [10; 11], and failed attempts to form an additional root [4; 12]. Although some authors have mentioned a possible genetic contribution to palatoradicular groove formation [13], no controlled studies have demonstrated a hereditary pattern; thus, current evidence remains inconclusive. A PRG normally begins in the region of the central fossa or in the cingulum, and its extension may be limited to the dental crown or involve the root surface, proceeding in a distal, midpalatal, or mesial direction [5]. PRGs are typically located on the palatal root surface, but labial involvement, though rare, has been reported, primarily in maxillary central incisors [14; 15]. Some cases also show both labial and palatal grooves [16]. Palatoradicular grooves are classified into three types based on the criteria proposed by [PERSON] and [PERSON]:  
Type I--a short groove limited to the coronal third of the root. Type II--a long but shallow groove extending beyond the coronal third, typically associated with a normal or simple root canal morphology. Type III--a long and deep groove extending beyond the coronal third, which may be further divided into two subtypes:  
Type IIIa--a long and deep groove corresponding to a C-shaped canal system. Type IIIb--a long and deep groove involving two separate root canals with normal morphology and apices, representing a labial groove connected to a palatal groove [17; 18] (Figure 1). A PRG can compromise the integrity and prognosis of the affected teeth, which makes the early diagnosis of this morphological alteration important to reduce the risk of complications [19]. Shallow, short palatoradicular grooves are usually innocuous, whereas deeper, more elongated grooves can create a pathway for infection, predisposing the tooth to pulp necrosis, periapical pathology, sinus-tract formation, periodontal pocketing and progressive alveolar bone loss via the apex, accessory foramina, lateral canals, and dental tubules [20]. Three-dimensional cone-beam computed tomography is a noninvasive diagnostic tool that helps provide three-dimensional anatomical configuration thereby facilitating diagnosis, classification, and treatment planning and improving treatment outcomes [21]. Recent studies have explored the use of cone-beam computed tomography as a tool for assessing the morphology and prevalence of dental structures [22]. These studies have demonstrated the reliability and accuracy of CBCT imaging for visualizing complex root canal anatomy and soft tissue structures in the detongigival unit. In this retrospective study, a CBCT-based evaluation was performed to determine the prevalence of palatoradicular grooves (PRGs) in maxillary anterior teeth within a Turkish population. The analysis included an assessment of gender-based distribution, the presence of unilateral or bilateral grooves, and detailed localization and classification based on radiographic features.