# Root Dilaceration and Dentigerous Cyst--A Cause-Effect Relationship?--\"Case-Series Study\"
## 1 Introduction  
Root dislocation (DL) is a dental anomaly that has been defined in various ways over time, depending on the criteria set by different authors. The term dilaceration (DL) was first used by [PERSON] in 1848, and according to the glossary of dental terms, DL is defined as the deformity of a tooth due to a disturbance between the mineralized and unmineralized portions of the developing tooth germ [1, 2]. Its most concise definition describes DL as an angulation, deviation, or sharp bend of either the crown or root axis, differentiating it from smooth curvatures of the root, also known as flexion [3, 4]. The criteria for acknowledging DL vary in the literature. According to [PERSON] et al., a tooth is considered to have a DL toward the mesial or distal direction if there is a 90-degree angle or more along the axis of the tooth or root [5]. [PERSON] et al. consider that DL is present when there is a deviation of 20 degrees or more of the apical part of the root to the normal axis of the tooth or root [6]. Root angulation (\"sickle\" incisor) is distinguished from DL as it denotes a curvature of the root resulting from a gradual change in the direction of root development without any evidence of abrupt displacement of the tooth germ during odontogenesis [4, 7, 8]. [PERSON] has described this condition as \"classic\" dilaceration [9]. DL can be seen in both permanent and deciduous dentitions, but the incidence in the latter one is significantly lower [10, 11, 12]. Some researchers reported that the prevalence of DL is higher in posterior teeth and the maxilla, with fewer occurrences among anterior teeth and in the mandible [5]. Bilaterally occurring DL in the same jaw might be seen in many patients, but bilateral DL in both the maxilla and mandible is rarely found [13, 14, 15]. Most publications concerning DL are case reports, and only a few have reported the prevalence of DL [5, 6, 10, 13, 14, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35]. Although any tooth may be affected by DL, there is no consistency between the most and least affected teeth reported with this anomaly [11]. DL might occur anywhere along the length of the tooth, such as within the crown, at the cemento-enamel junction, along the long axis of the root, or just at the root apex, depending on the extent of root that was formed at the time of injury [3]. There is no sex prediction regarding the DL of the teeth [36]. Without the consensus of the researchers, the etiology of DL is not fully understood. There are two main explanations for the causes of DL. The most widely accepted cause is trauma, an acute mechanical injury to the primary predecessor tooth, which leads to the DL of the underlying developing succedaneous permanent tooth. The calcified part of the permanent tooth germ is shifted in such a manner that the rest, the noncalcified part of the tooth germ, forms an angle to it [18; 19; 20; 37; 38; 39; 40]). Despite the high prevalence of traumatic injuries in primary dentition (ranging from 11-30%), the incidence of ollacetrated permanent teeth is minimal because most of the traumatic injuries do not damage the permanent tooth [37; 41]. Hence, traumatic injuries to the primary dentition are unlikely to account for all cases of DL, the high-risk injuries being those that reduce the intrabony space for permanent tooth development (i.e., intrusion, ankylosed primary tooth after trauma). An idiopathic developmental disturbance is proposed as another possible cause in cases without clear evidence of traumatic injury [7; 18; 21]. Dentigerous cyst DC (follicular cyst) is the second most prevalent epithelial-lined developmental odontogenic cyst, associated with partially erupted, developing, or impacted teeth [42; 43; 44]. It is formed due to an alteration in the reduced epithelium, by the accumulation of fluid between the reduced epithelium and the crown of an unerupted tooth.