Root Dilaceration: A Case Report and Literature Review

Root dilaceration is a dental malformation that has been recognised since 1848.¹ It is characterised by a significant angulation between the long axis of the crown and the root of the affected tooth.¹ Due to the deviation of the usual linear relationship between the dilacerated crown and root, impaction is often a complicating factor.² The position of the bend or curve can make it difficult for the tooth to be moved and presents a high risk of complications related to root resorption, bony fenestration, and perforation of a cortical plate.^1,3,4 The majority of the current research has defined dilaceration as an angle of 90° or more affecting the long axis of the tooth while some studies have considered root deviation greater than 20° constitutes dilaceration.⁵ Due to the unusual crown-root morphology, root dilaceration has been further considered as the most common cause of impaction of maxillary central incisors in children and adolescents.⁶

The prevalence of root dilaceration is approximately 1.6– 3.8% in the permanent dentition,^7–10 and 0.4–1.2% affecting the permanent maxillary incisors.^7,11,12 The condition occurs more frequently in the maxillary arch than the mandibular arch,^7,10 and without gender predication,^7,11–13 but several studies have indicated that females are more susceptible.^9,10,14 Most of the identified cases have been unilateral without a significant difference in distribution between left and right sides;⁷ bilateral cases have also been reported, although rare.^8,15

The aetiology of root dilaceration is unclear. Trauma and developmental anomalies are believed to be the main causes while it has been suggested that developmental syndromes, the formation of scar tissue, infection, cleft lip or palate, and ectopic tooth development can be contributing factors.^7,16 Dependent on the developmental stage of tooth formation, the position of the dilaceration can vary significantly and be identified by an abrupt deviation in the long axis between the tooth crown and the root.^7,16 Published case reports have associated dilaceration with previous trauma of the deciduous precursor and have suggested that trauma is a major contributing factor.^8,15,17 It is believed that the (permanent) tooth can be affected during its calcification stage by a traumatic force with upwards and labial vectors, resulting in the deviation in crown and root angulation.¹ However, anterior tooth dilaceration cases also have been identified in patients without a history of previous trauma.^2,18 In some circumstances, the dilaceration occurred in both the maxillary and mandibular dentitions; however, the patient experienced trauma only to the maxillary arch.⁷

Published studies have reported that mandibular third molars are the most frequently affected by this condition, yet this region is not likely to be subjected to direct trauma.^7,11,12 Further studies have suggested that, if dental trauma was the major cause of dilaceration, the prevalence would have occurred more often in the maxillary anterior region as the most susceptible area, but the mandibular posterior teeth have also recorded a high rate of root dilaceration.¹⁰ Traumatic injuries, therefore, cannot provide a total explanation for all dilaceration cases and are unlikely to be the only aetiological factor.¹⁶ Other risk factors related to root dilaceration have been found to be associated with non-eruption, impaction, an over-retained deciduous precursor and, less commonly, associated with fenestration of the cortical plate with or without obvious clinical symptoms.¹

The diagnosis of root dilaceration is usually aided by routine radiography, such as panoramic radiographs, periapical radiographs, and cone beam computed tomography (CBCT).¹² Occlusal radiographs and lateral cephalometric radiographs are occasionally used to provide additional information.¹ Of the twodimensional radiographs, periapical radiographs are more diagnostic than panoramic radiographs, and sometimes multiple periapical radiographs are required.⁵ Through the examination of twodimensional radiographs, the dilacerated root apices can appear as a radiolucent halo due to their unusual morphology.¹ The use of a CBCT scan can greatly assist clinicians to visualise the tooth in three dimensions, enable the assessment of crown and root morphology, canal configuration, the degree of root resorption of the adjacent teeth, and the presence of a periapical lesion.¹⁹

The clinical management of an impacted dilacerated tooth is usually challenging, time consuming, costly, and often requires multidisciplinary triaging to deliver treatment. It has been found that 35% of impacted maxillary incisors have been associated with dilaceration.²⁰ The impacted dilacerated maxillary incisor can significantly affect dentofacial aesthetics as well as the psychological well being of the patient as the problem is visibly located in the centre of the smile.²¹ Although spontaneous eruption of dilacerated incisors has been reported, intervention is usually indicated in most cases.²² Surgically, a higher risk of root fracture may occur during extraction due to the curved roots.⁷ Orthodontically, dilacerated teeth are difficult to manage as they are often associated with impaction.^1,2 Endodontically, negotiating and biomechanical debridement of the canal can be difficult due to the extensive angulation of the pulp canal system.

Two clinical treatment options are invariably considered: extraction followed by prosthodontic restoration, or surgical exposure followed by orthodontic traction.^1,2,21,23 Other treatment options may also be considered in specific cases, such as extraction followed by autotransplantation,²¹ and surgically repositioning the tooth and splinting.²⁴ When the dilacerated tooth is preserved, endodontic treatment with or without apicectomy may also be indicated, as the abnormal morphology of the root can cause bony fenestration.²¹ Considering the long-term prosthodontic burden for the patient, the surgical exposure and orthodontic traction is often preferred. The clinical challenge of treatment is well recognised and may present complications including ankylosis, periodontal recession and pocketing, root resorption, fenestration, and a loss of tooth vitality.^1,21

The present case report describes the treatment of an adolescent female patient presenting with a deeply impacted, dilacerated, maxillary central incisor. The incisor was successfully aligned into the arch after being rotated 100 degrees in the sagittal plane using orthodontic traction following a closed surgical exposure.

A 12-year-old female presented with the main concern of an impacted tooth and crossbite (Figures 1 and 2). She was physically healthy and without a significant family or medical history related to the impacted tooth. No trauma to the anterior region was reported.

Figure 1.

Figure 2.

A clinical examination revealed that there was a balanced facial appearance (Figure 1). Her lower dental midline was coincident with the facial midline but the upper dental midline was 3 mm to the right of the facial midline due to space loss. There was moderate crowding in the maxillary arch and mild crowding in the mandibular arch. The upper left maxillary lateral incisor was in crossbite which was the patient’s main concern. The impacted central incisor’s crown was palpable in the labial sulcus. The lower right first molar was heavily restored due to enamel hypomineralisation (Figures 1 and 2).

Panoramic radiography (Figure 3) showed normal mandibular condyles with no evident pathology. The patient was in the late mixed dentition phase, with unexfoliated upper left, lower left, and lower right second deciduous molars. The lower right second premolar was agenic and the corresponding deciduous tooth roots were short. A lateral cephalometric radiograph (Figure 4) showed a mild hyperdivergent Class III skeletal pattern, with minor dental compensation of proclined upper incisors and retroclined lower incisors (Figures 2 and 4).

Figure 3.

Figure 4.

Cone-beam computed tomography (CBCT) (Figure 5) showed that the upper right central incisor was rotated and impacted, and had a dilacerated root (a bend at the cementoenamel junction). The crown was rotated 100 degrees anticlockwise at the incisal edge in the sagittal plane. The root showed complete apex formation and no obvious root resorption to the adjacent teeth was noted.

Figure 5.

Two options were considered and discussed with the patient and parents. Option 2 was chosen.

Option 1: Surgical extraction of the impacted incisor 11 and prosthetic restoration or an implant after growth had ceased. Removal of the retained lower right second deciduous molar 85 and the lower left second premolar 35 followed by fixed appliances to close the spaces.

Option 2: Regaining space for the impacted incisor 11, surgical exposure and traction of the tooth into the dentition. Removal of the retained lower right second deciduous molar 85 and the lower left second premolar 35 and fixed appliances to close the spaces.

A referral to the paediatric dentistry clinic was planned to assess the long-term prognosis and restorability of the hypoplastic 46.

Fixed appliances with arch wires progressing from 0.012” NiTi to 0.016” Wilcock stainless steel wires and open-coil springs were used to regain space for the impacted central incisor. After space was sufficient, an 0.016” Wilcock stainless steel arch wire and a passive open-coil spring were used for maintenance before the surgical exposure (Figure 6).

Figure 6.

To avoid potential damage to the root of the 12, the bracket of 12 was positioned to provide additional distal root tip, and a V-bend in the arch wire was applied to achieve root divergence between 12 and 21 (Figure 6).

Due to the location and degree of impaction of the 11, a closed surgical exposure was performed (Figure 7A) and a button with gold chain was bonded to its palatal surface (Figure 7B). By the activation of power threads, the tooth was moved slowly in an occlusal direction and away from the roots of 12 and 21 (Figure 8).

Figure 7.

Figure 8.

For directional control of the traction, a Ballista spring was incorporated into the arch wire to encourage tooth movement vertically and sagittally into the centre of the alveolus. The links of the attached gold chain were subsequently incrementally shortened until all of the links were removed.

After 10 months of traction, the tooth was close to eruption and surgical re-exposure of 11 was performed in order to bond a bracket onto the labial surface. A three-sided incision with two parallel vertical cuts involving keratinised palatal mucosa was made, and the created soft tissue flap was repositioned at the mucogingival junction.

A step-down bend with an eyelet in an 0.018” Wilcock stainless steel arch wire was inserted to bypass the tooth 11, and power chain was tied to continue the traction (Figure 8B). The tooth was completely aligned into the arch by using a piggyback technique of 0.012” NiTi to 0.016×0.022” stainless steel arch wires to achieve the final alignment of the maxillary dentition (Figure 8C).

A referral was arranged to the paediatric dentistry clinic to have the 35 and 85 removed due to the guarded prognosis of 85. A symmetrical extraction pattern was chosen, therefore 35 was removed during the same surgical session. The extraction spaces were closed successfully by using NiTi closing coil springs and sliding biomechanics. The hypomineralised 46 was assessed by a paediatric specialist and a stainless-steel crown was placed to prevent further surface breakdown.

The active orthodontic treatment time was 43 months. After the alignment and arch form co-ordination, normal overjet, overbite, and intercuspation were established (Figures 9 and 10). There was mild plaque-induced gingival inflammation around the buccal surface of the 11. The 11 root torque and dental aesthetics were balanced in order to keep the dilacerated root within the alveolar bone housing.

Figure 9.

Figure 10.

No evident root resorption was identified on the radiographs (Figures 11 and 12). The tooth was vital and asymptomatic, and presented a satisfactory aesthetic appearance.

Figure 11.

Figure 12.

A maxillary 2-2 palatal fixed retainer and mandibular 3-3 lingual fixed retainer were applied for retention (Figure 9).

Clinical management of dilacerated and impacted incisors is usually complex, time-consuming, and costly.²⁵ The current case involved the multidisciplinary treatment by the orthodontic, oral surgery, and paediatric dentistry clinics to achieve a satisfactory overall treatment outcome. Two routine treatment options (i.e. extraction followed by prosthodontic restoration or surgical exposure with orthodontic traction) were discussed with the patient and parents. The final plan involved regaining space for the impacted dilacerated 11 using fixed appliances, a two-stage closed surgical exposure (due to the deep location and severe degree of ectopia and impaction), and extraction of 35 and 85. The restoration of the hypomineralised 46 was performed by the paediatric dentistry specialist. The impacted dilacerated incisor was successfully rotated 100 degrees in the sagittal plane and aligned into the dentition, with minimal root resorption and leaving an acceptable gingival contour (Figures 9–11).

The patient and parents chose the option of a surgical exposure followed by orthodontic traction rather than the alternative of extraction and prosthodontic restoration, due to their consideration of dental aesthetics and the future prosthodontic burden. To track the impacted tooth into the dentition, orthodontic movements usually include regaining sufficient space, surgical exposure, and traction of the tooth by an elastic thread.²⁶ In addition, to control the direction of traction, loops, such as a Ballista spring, eyelet loop, or a step-down/up bend may be incorporated into the arch wire. It is important to note that, to account for the angulation of the root dilaceration, patients and clinicians may need to balance the dental aesthetics (final position of the tooth) and dental health (keeping the dilacerated root apex within the alveolar housing). In severe root dilaceration cases with a labial projection of the root, apicectomy and endodontic treatment may be indicated to avoid bony fenestration.^21,26

Dilacerated incisors can be susceptible to root resorption during orthodontic movement. Previous studies have reported evident external root resorption with shorter and thinner roots after traction of a dilacerated impacted tooth.^26,27 In the current case, the CBCT analysis showed minimal root resorption of the dilacerated 11 (Figures 11 and 12). The pre-op root length was 16.10 mm; the post-op root length was 15.97 mm (Figure 12). The root of 21 was selected as the control reference, with the pre-op root length of 19.60 mm and post-op root length of 19.39 mm (Figure 13). Treatment success of the current case related to root resorption was similar to other reported cases;^{2,21,26,28,29} however, the previous studies only qualitatively evaluated the root status on post-operative panoramic radiographs, without quantitative measurements. To the best of current knowledge, this is the first case report that measured and compared the resorption of the dilacerated root using CBCT with the contralateral incisor as the control reference. Some published cases have shown a significant crown/root angle hence the high likelihood of labial alveolar bone perforation or root canal treatment following tooth correction.^1,3,21 CBCT images of the current case showed that the dilacerated root was short, and therefore a successful clinical outcome was relatively easier to achieve and no alveolar bone perforation or endodontic treatment was indicated nor performed.

Figure 13.

The variation in previous reports of root resorption of a dilacerated root may be due to the difference in the severity of dilaceration, the position of the root, the adjacent anatomical structures, the range of orthodontic movement, the management of biomechanics during traction, and the length of overall treatment.

Treatment time for an impacted dilacerated tooth has varied significantly between 11 and 45 months.^2,26–29 The treatment time for the current case was 43 months due to the deep impaction and severe displacement. The influencing factors of treatment time usually include the complexity of the case, the type of malocclusion, and the stage of dental development. If the treatment was initiated early when the patient was in the mixed dentition, the overall treatment time could also be longer.²⁶ In addition, if endodontic treatment or apicectomy are indicated, the overall treatment time can be increased by several months to allow for root canal treatment and monitoring.²¹

The periodontal condition of the 11 was also monitored closely throughout treatment. The buccal gingival margin of 11 appeared slightly red and inflamed with minor recession following alignment, which was particularly visible on the debond intraoral photographs (Figure 9). It is common for impacted teeth to have periodontal issues²⁵ and it has been reported that surgically exposed teeth usually have 0.5 mm more attachment loss and 0.2 mm more gingival recession than an unoperated control tooth.²⁵ A greater frequency of gingival recession in surgically exposed teeth has also been reported.³⁰ In general, inferior periodontal outcomes have been observed for surgically exposed canines despite the surgical method used. This was similar with the presented case as the 11 had localised gingivitis and mild gingival recession.

A closed or open exposure are two main surgical options for impacted teeth. Both methods involve a similar degree of bone removal to uncover the ectopic tooth. In the closed method, the palatal mucosa is left intact, while the open method will have a surgical dressing placed directly over the exposed tooth.³¹ The closed surgical exposure was preferred in the current case because the position of the impacted incisor was above mucogingival junction and in the alveolus.³² However, the disadvantage was that a second surgical exposure was required due to the deep location, severe tipping and impaction of the incisor.

Many studies have investigated the difference between the closed and open surgical exposure methods as well as the periodontal status after the orthodontic movement of the impacted teeth.^31,33–36 A systematic review found no evidence favouring one surgical exposure method over another to uncover a labially impacted canine with respect to the periodontal status.³³ Similarly, a Cochrane review that investigated palatally impacted canines and compared the open versus closed exposure, concluded neither technique was superior to the other regarding periodontal health. As the periodontal outcome was often measured and reported in different ways, a comparation was difficult.³⁴ Although reported research findings favoured a closed exposure technique,^31,35 to date, the choice between the two methods produces no conclusive benefit in dental health, aesthetics, cost-effectiveness, and patient comfort.³⁶

The clinical management of a dilacerated and severely impacted incisor is complicated and requires careful treatment planning, multidisciplinary triaging, skilful practices, and a relatively long treatment time. The treatment option of surgical exposure and orthodontic traction can preserve the natural dentition and aesthetics, and reduce future prosthodontic burden.