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Dilaceration: Review of an Endodontic Challenge
Review Article
Dilaceration: Review of an Endodontic Challenge Hamid Jafarzadeh, DDS, MSc,* and Paul V. Abbott, BDSc, MDS, FRACDS (Endo)† Abstract Dilaceration is the result of a developmental anomaly in which there has been an abrupt change in the axial inclination between the crown and the root of a tooth, but the criteria in the literature for recognizing root dilaceration vary. Two possible causes of dilaceration are trauma and developmental disturbances, and it has also been proposed that it might be associated with some developmental syndromes. Dilaceration can be seen in both the permanent and deciduous dentitions, and it is more commonly found in posterior teeth and in the maxilla. Periapical radiographs are the most appropriate way to diagnose the presence of root dilacerations. Diagnosis, endodontic access cavity preparation, root canal preparation and filling, and other related treatments might be complicated by the presence of a dilaceration. A review of the literature and a discussion of the options for managing this condition are presented. (J Endod 2007;33:1025–1030)
Key Words Dilaceration, endodontic treatment, trauma
From the *Department of Endodontics, Faculty of Dentistry and Dental Research Center, Mashhad University of Medical Sciences, Mashhad, Iran; and †School of Dentistry, University of Western Australia, Perth, Australia. Address requests for reprints to Dr Hamid Jafarzadeh, Faculty of Dentistry and Dental Research Center, Vakilabad Blvd, Mashhad, Iran. E-mail address: hamid_j365@yahoo. com. 0099-2399/$0 - see front matter Copyright © 2007 by the American Association of Endodontists. doi:10.1016/j.joen.2007.04.013
JOE — Volume 33, Number 9, September 2007
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tooth with a straight root and a straight root canal is an exception rather than normal because most teeth show some curvature of the canals. In addition, most canals have multiple planes of curvature throughout their length (1). The term dilaceration was first used by Tomes (2) in 1848, and it is defined as a deviation or bend in the linear relationship of a crown of a tooth to its root (Latin: dilacero ⫽ tear up) (3, 4) (Figs. 1 and 2). According to this definition, dilaceration is thus distinguished from the rarely used term flexion, which is defined as a tooth with a hooked or a bent root (4). Stewart (5) has likened tooth dilaceration to the hand of a traffic policeman, whereas Moreau (6) used the term scorpion tooth for this condition. The criteria for recognizing root dilaceration vary in the literature. According to some authors (7, 8), a tooth is considered to have a dilaceration toward the mesial or distal direction if there is a 90-degree angle or greater along the axis of the tooth or root, whereas others defined dilaceration as a deviation from the normal axis of the tooth of 20 degrees or more in the apical part of the root (9). Tooth dilaceration might present in various ways including non-eruption of the affected tooth, prolonged retention of the primary predecessor tooth, and apical fenestration of the labial cortical plate, or it can be asymptomatic (10 –13). If an erupted dilacerated tooth needs root canal treatment, then the presence of the dilaceration can severely complicate this treatment (1). Hence, this review will address the etiology, epidemiology, and diagnosis of dilacerations along with their association with other anomalies and some important treatment considerations.
Etiology Most authorities agree that there are 2 possible causes of dilaceration. The most widely accepted cause is mechanical trauma to the primary predecessor tooth, which results in dilaceration of the developing succedaneous permanent tooth. The calcified portion of the permanent tooth germ is displaced in such a way that the remainder of the permanent tooth germ forms at an angle to it (12, 14 –18). Although the prevalence of traumatic injuries to the primary dentition ranges from 11%–30%, the incidence of dilacerated permanent teeth is very low and disproportionate to the high prevalence of trauma. Hence, traumatic injuries to the primary dentition are unlikely to account for all cases of dilaceration and especially those of primary teeth themselves. An idiopathic developmental disturbance is proposed as another possible cause in cases that have no clear evidence of traumatic injury (5, 12, 19 –21). Although the damage frequently follows avulsion or intrusion of the overlying primary predecessor, an event that normally occurs before 4 years of age (19, 22), some reports (5, 19 –21, 23) have questioned the etiology of dilaceration and do not support the belief that trauma is the major etiologic factor. Some researchers support this view because most dilacerated teeth are found in posterior teeth, and these are not prone to direct trauma (7). Other possible contributing factors that have been reported include scar formation, developmental anomaly of the primary tooth germ, facial clefting (24), advanced root canal infections (25), ectopic development of the tooth germ and lack of space (5, 8, 19), the effect of anatomic structures (for example, the cortical bone of the maxillary sinus, the mandibular canal, or the nasal fossa, which might deflect the epithelial diaphragm) (26), the presence of an adjacent cyst, tumor, or odontogenic hamartoma (for example, odontoma and supernumerary tooth) (5, 22 ,27–29), orotracheal intubation and laryngoscopy (11, 22, 30), mechanical interference with eruption (for example, from an ankylosed primary tooth that does not resorb) (31), tooth transplantation (32), extraction of primary teeth (33), and hereditary factors (34 –36).
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Review Article extraction of deciduous tooth roots can lead to dilaceration of the developing permanent premolar crowns because of their close relationship with the deciduous molar tooth roots (33).
Diagnosis
Figure 1. A dilacerated mandibular third molar tooth.
Epidemiology Dilaceration can be seen in both the permanent and deciduous dentitions, but the incidence in the latter is very low (10, 22, 28). Some researchers reported that the prevalence is greater in posterior teeth and in the maxilla with fewer occurrences among anterior teeth and in the mandible (8), although one author noted that two thirds of the dilacerations in their study were in the mandible (7). Bilaterally occurring dilacerations might be seen in many patients (37, 38), but bilateral dilaceration in both the maxilla and mandible of the same person is rarely found (35). There is no sex predilection for dilacerations of the teeth (39). Most publications concerning dilacerations are case reports (10 – 12, 17, 18, 20, 23, 33, 37, 38, 40 –50), and only a few (7–9, 51) have reported the prevalence of dilacerations, with the frequencies ranging from 0.32% (8) to 98% (9) of teeth (Table 1). Although Chohayeb (9) has reported that the frequency of dilaceration in upper lateral incisors is 98%, it is highly questionable whether 98% of teeth can be classified as having a large enough deviation to be classified as a dilaceration. It appears as though Chohayeb might have classified the distal curvature of the apical third of the root of the upper lateral incisors as being a dilaceration rather than considering it as the normal, or typical, anatomy of this tooth (52). Although any tooth might have a dilaceration (22), there is no consistency about the most and least affected teeth reported with this anomaly (Table 2). In addition, although dilaceration might occur anywhere along the length of the tooth, such as within the crown, at the cemento-enamel junction, anywhere along the length of the root, or just at the root apex, and this will depend on the extent of root that was formed at the time of injury (3), a recent study showed that root dilaceration in incisors, canines, and premolars is most common in the apical third of the roots. Dilaceration within the middle third of the root is more frequent in molars, whereas dilaceration within the coronal third of the root is most commonly seen in third molars (8). Crown dilacerations are less common than root dilacerations (40), and they usually occur in maxillary permanent incisors because of their close position to primary incisors where many traumatic injuries occur (33). The injuries to the primary dentition that can result in crown dilaceration are avulsion or intrusion (19). Crown dilacerations with palatal angulation of the crown occur most commonly in upper incisors, whereas labial angulation is more common in lower incisors (50). Apart from trauma as the result of an accident, trauma during 1026
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The recognition and diagnosis of a dilaceration are essential for any tooth that requires root canal treatment (9), extraction (55), or orthodontic movement (51). Although dilaceration of a crown can be visually observed in the mouth, radiographic examination is required to diagnose a dilaceration of a tooth root (7). The direction of root dilacerations should be considered in 2 planes, and they can be categorized as mesial, distal, labial/buccal, or palatal/lingual. If the roots bend mesially or distally, the dilaceration is clearly apparent on a periapical radiograph. However, when the dilaceration is toward the labial/buccal or palatal/lingual, the x-ray beam passes through the deflected portion of the root in an approximately parallel direction. The dilacerated portion then appears at the apical end of the unaltered root as a rounded opaque area with a dark “spot” in its center that is caused by the apical foramen of the root canal (this appearance has been likened to a bull’seye or a target) (Fig. 3). The periodontal ligament space around the dilacerated portion of the root might be seen as a radiolucent halo, and the radiopacity of this segment of the root is usually greater than the rest of the root as a result of the increased thickness of tooth structure that the x-rays have to pass through. In some cases, especially in the maxilla, the geometry of the projections might preclude the recognition of a dilaceration (21, 54, 56, 57). Panoramic radiography alone is not the method of choice for the diagnosis of root dilacerations, which can occur in the buccal/labial or palatal/lingual directions. Additional radiographs from different angles are recommended to assist with the diagnosis (51). Occasionally dilacerated roots are difficult to differentiate from fused roots, condensing osteitis, or a dense bone island. However, they can usually be distinguished from these conditions by taking radiographs from different angles (54).
Associated Syndromes Some syndromes and developmental anomalies such as SmithMagenis syndrome (58), the hypermobility type of Ehlers-Danlos syndrome (59), Axenfeld-Rieger syndrome (60), and congenital ichthyosis (61) have been associated with tooth dilaceration. The associations with these syndromes are summarized in Table 3.
Figure 2. A dilacerated maxillary central incisor tooth.
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Review Article TABLE 1. Prevalence of Dilacerations in Teeth: Summary of Reports in the Dental Literature Sample size*
No. of dilacerations*
Percentage (%)*
Mixed
480
470
97.9
Max lateral incisor
Mixed
442
433
98
All teeth
Not stated
All teeth
Jordanian
Max central incisor Max lateral incisor Max canine Max first premolar Max second premolar Max first molar Max second molar Max third molar Mand central incisor Mand lateral incisor Mand canine Mand first premolar Mand second premolar Mand first molar Mand second molar Mand third molar Max central incisor Max lateral incisor Max canine Max first premolar Max second premolar Max first molar Max second molar Max third molar Mand central incisor Mand lateral incisor Mand canine Mand first premolar Mand second premolar Mand first molar Mand second molar Mand third molar
Croatian
Author(s)
Year
Chohayeb (9)
1983
Max lateral incisor
Chohayeb (9)
1983
Thongudomporn 1998 and Freer (51) Hamasha et al 2002 (7) Malcic et al (8) 2006
Malcic et al (8)
2006
Tooth type
Race
Croatian
111 patients 4655
2 patients 176
1.8 patients 3.78
3 15 7 10 18 38 24 7 1 0 1 3 3 4 3 19 5 13 7 25 29 42 58 45 4 3 9 13 16 2 13 179
1.3 7 3.6 4.5 6.7 15 11.4 8.1 1.7 0 1.2 2.1 1.5 2.2 1.7 24.1 0.53 1.43 0.74 3.32 4.1 7.01 7.84 8.46 0.42 0.32 0.93 1.42 1.99 0.45 1.99 30.92
242 213 193 220 270 247 211 86 59 63 86 146 203 183 180 79 947 907 940 753 708 599 740 532 942 951 970 915 806 448 655 579
Type of study Visual inspection (in vitro) Periapical radiography (in vivo) Panoramic radiography Periapical radiography Periapical radiography
Panoramic radiography
Max, maxillary; Mand, Mandibular. *Data represent teeth unless indicated otherwise.
Treatment Considerations Central to successful endodontic treatment is a thorough knowledge, respect, and appreciation for root canal anatomy together with careful, thoughtful, and meticulously performed cleaning and shaping procedures. A variety of factors, including crown and root dilacerations, might complicate this treatment (1), so when attempting to perform
endodontic procedures, the clinician must use great care to avoid mishaps in teeth with significant dilacerations (22). In dilacerated teeth, the accepted basic endodontic techniques must be strictly followed, that is, good preoperative and working radiographs, unobstructed access to the root canal orifice, as direct access as possible to the apical third of the canal (within the constraints of the
TABLE 2. Most and Least Affected Teeth Reported to Have Root Dilacerations Race
Most affected teeth
Wheeler (53)
Author(s)
Not stated
Thongudomporn and Freer (51) Neville et al (22)
Not stated Not stated
White and Pharoah (54) Hamasha et al (7)
Not stated Jordanian
Malcic et al (8)
Croatian
Third molars Maxillary lateral incisors Maxillary lateral incisors (1.8%) Maxillary incisors Mandibular anterior dentition Maxillary premolars Mandibular third molars (19.2%) Mandibular first molars (5.6%) Mandibular third molars (24.1%) Maxillary first molars (15.3%) Maxillary second molars (11.4%) Maxillary third molars (8.1%)
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Least affected teeth Not stated Not stated Not stated Not stated Maxillary and mandibular incisors (1%) Mandibular lateral incisors (0%) Mandibular canines (1.2%) Maxillary central incisors (1.2%) Mandibular second premolars (1.5%)
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Review Article treatment of dilacerated cases, some important considerations in the treatment of such teeth have been summarized in this section.
Diagnosis Diagnosing root dilacerations before commencing endodontic treatment is essential to allow proper and safe use of endodontic instruments within the curved roots (7, 9, 65). Failure to recognize the multi-planar nature of the dilaceration is one of the factors that might contribute to the higher rate of unfavorable outcomes of endodontic treatment of singlerooted teeth such as upper lateral incisors, compared with the number of unfavorable treatment outcomes in multi-rooted teeth (66). To overcome this problem, periapical radiographs that determine the direction of dilaceration are adequate (9). However, such diagnostic findings can be confirmed by a computed tomography scan, which can help to determine the exact position and angulation of the dilaceration (41).
Figure 3. “Bull’s-eye” phenomena in a central incisor with a dilacerated root under orthodontic realignment. Reproduced with permission from Ingle JI, Bakland LK. Endodontics. 5th ed. London, UK. B.C. Decker Inc. 2002:230.
dilaceration), precurvature of all files used (the sharper the canal curvature, the nearer the bend of the file should be to its tip), and thorough irrigation (35). Orthodontic movement of dilacerated teeth might cause severe irreversible resorption of the root, which can severely complicate the endodontic treatment of these teeth (31, 62– 64). Although the body of literature lacks complete, multifarious, and informative research on techniques or materials that might facilitate the endodontic
Access Cavities Direct access to the apical foramen, as much as possible, is an important benefit gained through the access cavity preparation. To provide the most direct access possible to the apical foramen, enough tooth structure must be removed to allow the endodontic instruments to be moved freely within the coronal cavity. However, Luebke has made an important observation that an entire access cavity wall need not be extended in the event that instrument impingement occurs as a result of a dilacerated root. In extending only that portion of the wall needed to free the instrument, a cloverleaf appearance might evolve as the outline form. Luebke has termed this a “shamrock preparation”. In fact, this is a modified outline form to accommodate the instrument unrestrained in the severely curved canals (57). In teeth with crown dilaceration, endodontic treatment might be complex and might require modification of the affected crown. In severe cases, the affected part of the crown might need to be removed, and a provisional prosthesis will need to be placed until a definitive restoration is possible (67). Root Canal System Identification and Preparation In dilacerated teeth, it is often difficult to explore and negotiate the root canals, especially if the state of the pulp has caused apposition and/or resorption of the canal wall. Therefore, when an endodontic file is introduced into the root canal during treatment, it might be blocked by such irregularities, even if the file has been precurved, and this might
TABLE 3. Summary of the Associations between Dilacerations and Various Syndromes Disease
Type of inheritance
Oral features
Smith-Magenis syndrome (58)
Autosomal dominant
Tooth dilaceration, tooth agenesis, taurodontism
Ehlers-Danlos syndrome (59)
Autosomal recessive, autosomal dominant, X-linked recessive
Axenfeld-Rieger syndrome (60)
Autosomal dominant
Congenital ichthyosis (61)
Autosomal recessive
Tooth dilaceration, hypodontia, dentin dysplasia, transmigration, ectopic eruption, delayed eruption Tooth dilaceration, short roots, hyperplastic frenums, underdeveloped maxilla, anterior crossbite, bilateral posterior open-bite, anterior crowding Tooth dilaceration, delayed tooth eruption
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Systemic features Mental retardation, infantile hypotonia, lethargy in infancy, brachycephaly, brachydactyly, ocular abnormalities Joint hyperlaxity, skin hyperextensibility
Incidence of dilaceration 33%
Not stated
Ocular & extraocular malformations
Not stated
Hyperkeratosis of knees and elbows, fish-like scaly skin
Not stated
JOE — Volume 33, Number 9, September 2007
Review Article prevent the operator from reaching the ideal working length (35). Hence, the use of a “scout file” can provide critical information regarding the extent and direction of a root canal dilaceration. Scout files are not just measuring wires; rather, they provide critical information before initiating shaping procedures (1). Another problem in endodontic treatment of these cases is the inability to continuously follow the root canal curvature, and this might result in blocking of the canal, ledging, apical cavitation such as transportation and/or zipping, perforation, and instrument breakage (1, 65). When using manual instrumentation techniques, the flexibility of the instruments with respect to their size must be considered. It is essential to precurve all instruments, and especially those larger than size 20, to allow the files to follow the curve and not just cut in a straight direction (65, 68). The extent of the precurvature required for each instrument will depend on the curvature of the canal, the size of the instrument, and the depth at which the instrument is to be used in the canal (68). Instruments with non-cutting tips and those made from nickeltitanium (NiTi) have been shown to help maintain root canal curvatures in many teeth. However, in general, dilacerated root canals are not suitable for the use of NiTi rotary instruments because of the severe nature and extent of the curvatures that must be negotiated (1). All instruments used within severely curved canals should be discarded after use to prevent breakage within the canal, that is, they should be considered as “single use instruments” (57). Many dilacerated teeth, especially anterior mandibular teeth, will be pulpless and infected with periapical inflammatory lesions (22). Hence, the outcome of root canal treatment will depend largely on complete biomechanical debridement of the canals and the elimination of microorganisms from the root canal system (69). The use of copious irrigation, file recapitulation, and further irrigation should be repeated more frequently in these severely curved canals (1). A multi-visit approach should also be followed, with the use of interappointment intracanal medicaments to increase the predictability of the treatment. Intracanal medicaments are essential to help disinfect the root canal system, especially in areas that are inaccessible to mechanical instrumentation and irrigation, and to change the intracanal environment so microorganisms are not likely, or at least less likely, to be able to survive. Because the value of calcium hydroxide in endodontic treatment is now well-documented, it is proposed to use this material as a medicament in dilacerated teeth (1). To overcome the complexity of reaching calcium hydroxide to the apical third of dilacerated teeth, it has been proposed to mix calcium hydroxide with glycerin rather than with sterile water. It has been shown that glycerin is significantly superior to water in regards to the length of filling and density in the apical third of curved canals (70).
Root Canal Filling Although lateral compaction of curved canals can be very effective in most teeth, this technique might be difficult and sometimes impossible in dilacerated canals. If small, flexible spreaders cannot reach to within 1 mm of the working length, or the taper of the root canal preparation is less than that of the spreader, then lateral compaction is not the technique of choice (57). If the lateral compaction technique is chosen, then spreaders made from NiTi are highly recommended for the filling of severely curved root canal systems (1) because they will penetrate to greater depths and distribute forces more evenly than stainless steel spreaders (57). In nondilacerated cases, as the spreader reaches the desired depth, the master gutta-percha cone is compacted laterally and vertically by moving the instrument in an arc up to 180 degrees, whereas in dilacerated canals, the arc of movement should be limited to 90 degrees or even less (1). JOE — Volume 33, Number 9, September 2007
The use of warm or thermoplasticized gutta-percha techniques might be more applicable in many cases, although these techniques might also be difficult to perform because of the presence of the dilaceration (57). Some studies have shown that in curved canals, ThermaFil (Tulsa Dental Products, Tulsa, OK) results in comparable to (71) or better apical seal than lateral condensation technique (72, 73), although Barkins and Montgomery (74) did not agree with this idea.
Intentional Replantation Intentional replantation of dilacerated teeth is generally not recommended because extraction of the dilacerated tooth might be difficult and could easily result in fracture of the dilacerated root (22, 34, 69), especially if the surgeon is not prepared with a preoperative radiograph (54). Forced Eruption In rare instances in which orthodontic treatment is used to extrude a dilacerated tooth, the dilaceration of the root might make this procedure quite complicated or even impossible (31). Prosthetic Treatment Finite element stress analysis has indicated that root dilaceration concentrates the stresses in the supporting structures if the dilacerated tooth is used as an abutment for a dental prosthesis, so this should be considered as a risk factor in abutment selection. This increased stress might affect the stability and longevity of the abutment tooth and hence also that of the prosthesis. Splinting the dilacerated abutment tooth to an adjacent tooth to obtain a multi-rooted abutment might be an approach to consider in some cases (22, 75). Prognosis The prognosis of dilacerated teeth that require endodontic treatment varies according to the severity of the deformity and the practitioner’s skills (22, 57). It will also depend on many other factors such as the reason why endodontic treatment was required, how much tooth structure remains, and the prognosis for any restoration that is placed on the tooth. It is difficult to predict the prognosis before treatment, and in many cases, the prognosis will not become evident until the practitioner has undertaken initial endodontic treatment to determine whether the canal can be negotiated completely and then adequately disinfected and filled.
Summary and Conclusions Dilacerated teeth are not common, but they do pose a number of diagnostic, management, and prognostic challenges to dental practitioners. The presence of a dilaceration must be identified before treatment, and this can be achieved by a thorough clinical and radiographic examination. Once identified, the effect of the defect on the endodontic and restorative dental management of the tooth can be more fully assessed. Where other treatment (such as extraction, orthodontics) is required, the identification of a dilaceration is equally important to ensure appropriate management.
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40. Asokan S, Rayen R, Muthu MS, Sivakumar N. Crown dilaceration of maxillary right permanent central incisor: a case report. J Indian Soc Pedod Prev Dent 2004;22:197–200. 41. Agnihotri A, Marwah N, Dutta S. Dilacerated unerupted central incisor: a case report. J Indian Soc Pedod Prev Dent 2006;24:152– 4. 42. Prabhakar AR, Reddy VV, Bassappa N. Duplication and dilaceration of a crown with hypercementosis of the root following trauma: a case report. Quintessence Int 1998;29:655–7. 43. Meadow DM, Needleman HL. Dilaceration of the mandibular permanent incisor teeth: two case reports. Pediatr Dent 1981;3:276 – 8. 44. Yen HT, Diau MH, Tsai JW, Roan RT. Dilaceration of a central incisor with iatrogenic root perforation: a case report. Gaoxiong Yi Xue Ke Xue Za Zhi 1991;7:386 –90. 45. McNamara TG, McNamara CM. Dilaceration of a mandibular incisor: case report. Singapore Dent J 2000;23:29 –31. 46. Maia RL, Vieira AP. Auto-transplantation of central incisor with root dilacerations: technical note. Int J Oral Maxillofac Surg 2005;34:89 –91. 47. Glenn FB, Stanley HR Jr. Dilaceration of a mandibular permanent incisor: report of a case. Oral Surg Oral Med Oral Pathol 1960;13:1249 –52. 48. Ngeow WC. An unusual dilacerated root of a second maxillary molar. J Ir Dent Assoc 1996;42:51–2. 49. Edler R. Dilaceration of upper central and lateral incisors: a case report. Br Dent J 1973;135:331–2. 50. Lowe PL. Dilaceration caused by direct penetrating injury. Br Dent J 1985;159:373– 4. 51. Thongudomporn U, Freer TJ. Prevalence of dental anomalies in orthodontic patients. Aust Dent J 1998;43:395– 8. 52. Ingle JI, Taintor JF. Endodontics. 3rd ed. Philadelphia: Lea & Febiger, 1985:120 –1. 53. Wheeler RC. Textbook of dental anatomy and physiology. 4th ed. Philadelphia: WB Saunders, 1965:133. 54. White SC, Pharoah MJ. Oral radiology: principles and interpretation. 5th ed. St Louis: Mosby, 2004:340. 55. Davies PH, Lewis DH. Dilaceration: a surgical/orthodontic solution. Br Dent J 1984;156:16 – 8. 56. Sawamura T, Minowa K, Nakamura M. Impacted teeth in the maxilla: usefulness of 3D Dental-CT for preoperative evaluation. Eur J Radiol 2003;47:221– 6. 57. Ingle JI, Bakland LK. Endodontics. 5th ed. London: BC Decker Inc, 2002:409 –10, 489, 540, 609 –36, 776 –7. 58. Tomona N, Smith AC, Guadagnini JP, Hart TC. Craniofacial and dental phenotype of Smith-Magenis syndrome. Am J Med Genet A 2006;140:2556 – 61. 59. Yassin OM, Rihani FB. Multiple developmental dental anomalies and hypermobility type Ehlers-Danlos syndrome. J Clin Pediatr Dent 2006;30:337– 41. 60. Jena AK, Kharbanda OP. Axenfeld-Rieger syndrome: report on dental and craniofacial findings. J Clin Pediatr Dent 2005;30:83– 8. 61. Pinkham JR, Casamassimo PS, McTigue DJ, Fields HW, Nowak AJ. Pediatric dentistry: infancy through adolescence. 4th ed. St Louis: Elsevier Inc, 2005:66. 62. Mirabella AD, Artun J. Risk factors for apical root resorption of maxillary anterior teeth in adult orthodontic patients. Am J Orthod Dentofacial Orthop 1995;108: 48 –55. 63. Sameshima GT, Sinclair PM. Predicting and preventing root resorption: part I. Diagnostic factors. Am J Orthod Dentofacial Orthop 2001;119:505–10. 64. Kjaer I. Morphological characteristics of dentitions developing excessive root resorption during orthodontic treatment. Eur J Orthod 1995;17:25–34. 65. Walton RE, Torabinejad M. Principles and practice of endodontics. 2nd ed. Philadelphia: WB Saunders, 1996:330 –2. 66. Grahnen H, Hansson L. The prognosis of pulp and root canal therapy. Odontol Revy 1961;12:146 – 65. 67. Diab M, elBadrawy HE. Intrusion injuries of primary incisors. Part III: Effects on the permanent successors. Quintessence Int 2000;31:377– 84. 68. Cohen S, Burns RC. Pathways of the pulp. 3rd ed. St Louis: Mosby, 1984:185– 6. 69. Seltzer S. Endodontology: biologic considerations in endodontic procedures. New York: McGraw-Hill, 1971:386. 70. Rivera EM, Williams K. Placement of calcium hydroxide in simulated canals: comparison of glycerin versus water. J Endod 1994;20:445– 8. 71. Schafer E, Olthoff G. Effect of three different sealers on the sealing ability of both thermafil obturators and cold laterally compacted Gutta-Percha. J Endod 2002;28:638 – 42. 72. Lares C, elDeeb ME. The sealing ability of the Thermafil obturation technique. J Endod 1990;16:474 –9. 73. Leung SF, Gulabivala K. An in-vitro evaluation of the influence of canal curvature on the sealing ability of Thermafil. Int Endod J 1994;27:190 – 6. 74. Barkins W, Montgomery S. Evaluation of Thermafil obturation of curved canals prepared by the Canal Master-U system. J Endod 1992;18:285–9. 75. Celik E, Aydinlik E. Effect of a dilacerated root on stress distribution to the tooth and supporting tissues. J Prosthet Dent 1991;65:771–7.
JOE — Volume 33, Number 9, September 2007
Dilaceration: Review of an Endodontic Challenge Hamid Jafarzadeh, DDS, MSc,* and Paul V. Abbott, BDSc, MDS, FRACDS (Endo)† Abstract Dilaceration is the result of a developmental anomaly in which there has been an abrupt change in the axial inclination between the crown and the root of a tooth, but the criteria in the literature for recognizing root dilaceration vary. Two possible causes of dilaceration are trauma and developmental disturbances, and it has also been proposed that it might be associated with some developmental syndromes. Dilaceration can be seen in both the permanent and deciduous dentitions, and it is more commonly found in posterior teeth and in the maxilla. Periapical radiographs are the most appropriate way to diagnose the presence of root dilacerations. Diagnosis, endodontic access cavity preparation, root canal preparation and filling, and other related treatments might be complicated by the presence of a dilaceration. A review of the literature and a discussion of the options for managing this condition are presented. (J Endod 2007;33:1025–1030)
Key Words Dilaceration, endodontic treatment, trauma
From the *Department of Endodontics, Faculty of Dentistry and Dental Research Center, Mashhad University of Medical Sciences, Mashhad, Iran; and †School of Dentistry, University of Western Australia, Perth, Australia. Address requests for reprints to Dr Hamid Jafarzadeh, Faculty of Dentistry and Dental Research Center, Vakilabad Blvd, Mashhad, Iran. E-mail address: hamid_j365@yahoo. com. 0099-2399/$0 - see front matter Copyright © 2007 by the American Association of Endodontists. doi:10.1016/j.joen.2007.04.013
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A
tooth with a straight root and a straight root canal is an exception rather than normal because most teeth show some curvature of the canals. In addition, most canals have multiple planes of curvature throughout their length (1). The term dilaceration was first used by Tomes (2) in 1848, and it is defined as a deviation or bend in the linear relationship of a crown of a tooth to its root (Latin: dilacero ⫽ tear up) (3, 4) (Figs. 1 and 2). According to this definition, dilaceration is thus distinguished from the rarely used term flexion, which is defined as a tooth with a hooked or a bent root (4). Stewart (5) has likened tooth dilaceration to the hand of a traffic policeman, whereas Moreau (6) used the term scorpion tooth for this condition. The criteria for recognizing root dilaceration vary in the literature. According to some authors (7, 8), a tooth is considered to have a dilaceration toward the mesial or distal direction if there is a 90-degree angle or greater along the axis of the tooth or root, whereas others defined dilaceration as a deviation from the normal axis of the tooth of 20 degrees or more in the apical part of the root (9). Tooth dilaceration might present in various ways including non-eruption of the affected tooth, prolonged retention of the primary predecessor tooth, and apical fenestration of the labial cortical plate, or it can be asymptomatic (10 –13). If an erupted dilacerated tooth needs root canal treatment, then the presence of the dilaceration can severely complicate this treatment (1). Hence, this review will address the etiology, epidemiology, and diagnosis of dilacerations along with their association with other anomalies and some important treatment considerations.
Etiology Most authorities agree that there are 2 possible causes of dilaceration. The most widely accepted cause is mechanical trauma to the primary predecessor tooth, which results in dilaceration of the developing succedaneous permanent tooth. The calcified portion of the permanent tooth germ is displaced in such a way that the remainder of the permanent tooth germ forms at an angle to it (12, 14 –18). Although the prevalence of traumatic injuries to the primary dentition ranges from 11%–30%, the incidence of dilacerated permanent teeth is very low and disproportionate to the high prevalence of trauma. Hence, traumatic injuries to the primary dentition are unlikely to account for all cases of dilaceration and especially those of primary teeth themselves. An idiopathic developmental disturbance is proposed as another possible cause in cases that have no clear evidence of traumatic injury (5, 12, 19 –21). Although the damage frequently follows avulsion or intrusion of the overlying primary predecessor, an event that normally occurs before 4 years of age (19, 22), some reports (5, 19 –21, 23) have questioned the etiology of dilaceration and do not support the belief that trauma is the major etiologic factor. Some researchers support this view because most dilacerated teeth are found in posterior teeth, and these are not prone to direct trauma (7). Other possible contributing factors that have been reported include scar formation, developmental anomaly of the primary tooth germ, facial clefting (24), advanced root canal infections (25), ectopic development of the tooth germ and lack of space (5, 8, 19), the effect of anatomic structures (for example, the cortical bone of the maxillary sinus, the mandibular canal, or the nasal fossa, which might deflect the epithelial diaphragm) (26), the presence of an adjacent cyst, tumor, or odontogenic hamartoma (for example, odontoma and supernumerary tooth) (5, 22 ,27–29), orotracheal intubation and laryngoscopy (11, 22, 30), mechanical interference with eruption (for example, from an ankylosed primary tooth that does not resorb) (31), tooth transplantation (32), extraction of primary teeth (33), and hereditary factors (34 –36).
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Review Article extraction of deciduous tooth roots can lead to dilaceration of the developing permanent premolar crowns because of their close relationship with the deciduous molar tooth roots (33).
Diagnosis
Figure 1. A dilacerated mandibular third molar tooth.
Epidemiology Dilaceration can be seen in both the permanent and deciduous dentitions, but the incidence in the latter is very low (10, 22, 28). Some researchers reported that the prevalence is greater in posterior teeth and in the maxilla with fewer occurrences among anterior teeth and in the mandible (8), although one author noted that two thirds of the dilacerations in their study were in the mandible (7). Bilaterally occurring dilacerations might be seen in many patients (37, 38), but bilateral dilaceration in both the maxilla and mandible of the same person is rarely found (35). There is no sex predilection for dilacerations of the teeth (39). Most publications concerning dilacerations are case reports (10 – 12, 17, 18, 20, 23, 33, 37, 38, 40 –50), and only a few (7–9, 51) have reported the prevalence of dilacerations, with the frequencies ranging from 0.32% (8) to 98% (9) of teeth (Table 1). Although Chohayeb (9) has reported that the frequency of dilaceration in upper lateral incisors is 98%, it is highly questionable whether 98% of teeth can be classified as having a large enough deviation to be classified as a dilaceration. It appears as though Chohayeb might have classified the distal curvature of the apical third of the root of the upper lateral incisors as being a dilaceration rather than considering it as the normal, or typical, anatomy of this tooth (52). Although any tooth might have a dilaceration (22), there is no consistency about the most and least affected teeth reported with this anomaly (Table 2). In addition, although dilaceration might occur anywhere along the length of the tooth, such as within the crown, at the cemento-enamel junction, anywhere along the length of the root, or just at the root apex, and this will depend on the extent of root that was formed at the time of injury (3), a recent study showed that root dilaceration in incisors, canines, and premolars is most common in the apical third of the roots. Dilaceration within the middle third of the root is more frequent in molars, whereas dilaceration within the coronal third of the root is most commonly seen in third molars (8). Crown dilacerations are less common than root dilacerations (40), and they usually occur in maxillary permanent incisors because of their close position to primary incisors where many traumatic injuries occur (33). The injuries to the primary dentition that can result in crown dilaceration are avulsion or intrusion (19). Crown dilacerations with palatal angulation of the crown occur most commonly in upper incisors, whereas labial angulation is more common in lower incisors (50). Apart from trauma as the result of an accident, trauma during 1026
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The recognition and diagnosis of a dilaceration are essential for any tooth that requires root canal treatment (9), extraction (55), or orthodontic movement (51). Although dilaceration of a crown can be visually observed in the mouth, radiographic examination is required to diagnose a dilaceration of a tooth root (7). The direction of root dilacerations should be considered in 2 planes, and they can be categorized as mesial, distal, labial/buccal, or palatal/lingual. If the roots bend mesially or distally, the dilaceration is clearly apparent on a periapical radiograph. However, when the dilaceration is toward the labial/buccal or palatal/lingual, the x-ray beam passes through the deflected portion of the root in an approximately parallel direction. The dilacerated portion then appears at the apical end of the unaltered root as a rounded opaque area with a dark “spot” in its center that is caused by the apical foramen of the root canal (this appearance has been likened to a bull’seye or a target) (Fig. 3). The periodontal ligament space around the dilacerated portion of the root might be seen as a radiolucent halo, and the radiopacity of this segment of the root is usually greater than the rest of the root as a result of the increased thickness of tooth structure that the x-rays have to pass through. In some cases, especially in the maxilla, the geometry of the projections might preclude the recognition of a dilaceration (21, 54, 56, 57). Panoramic radiography alone is not the method of choice for the diagnosis of root dilacerations, which can occur in the buccal/labial or palatal/lingual directions. Additional radiographs from different angles are recommended to assist with the diagnosis (51). Occasionally dilacerated roots are difficult to differentiate from fused roots, condensing osteitis, or a dense bone island. However, they can usually be distinguished from these conditions by taking radiographs from different angles (54).
Associated Syndromes Some syndromes and developmental anomalies such as SmithMagenis syndrome (58), the hypermobility type of Ehlers-Danlos syndrome (59), Axenfeld-Rieger syndrome (60), and congenital ichthyosis (61) have been associated with tooth dilaceration. The associations with these syndromes are summarized in Table 3.
Figure 2. A dilacerated maxillary central incisor tooth.
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Review Article TABLE 1. Prevalence of Dilacerations in Teeth: Summary of Reports in the Dental Literature Sample size*
No. of dilacerations*
Percentage (%)*
Mixed
480
470
97.9
Max lateral incisor
Mixed
442
433
98
All teeth
Not stated
All teeth
Jordanian
Max central incisor Max lateral incisor Max canine Max first premolar Max second premolar Max first molar Max second molar Max third molar Mand central incisor Mand lateral incisor Mand canine Mand first premolar Mand second premolar Mand first molar Mand second molar Mand third molar Max central incisor Max lateral incisor Max canine Max first premolar Max second premolar Max first molar Max second molar Max third molar Mand central incisor Mand lateral incisor Mand canine Mand first premolar Mand second premolar Mand first molar Mand second molar Mand third molar
Croatian
Author(s)
Year
Chohayeb (9)
1983
Max lateral incisor
Chohayeb (9)
1983
Thongudomporn 1998 and Freer (51) Hamasha et al 2002 (7) Malcic et al (8) 2006
Malcic et al (8)
2006
Tooth type
Race
Croatian
111 patients 4655
2 patients 176
1.8 patients 3.78
3 15 7 10 18 38 24 7 1 0 1 3 3 4 3 19 5 13 7 25 29 42 58 45 4 3 9 13 16 2 13 179
1.3 7 3.6 4.5 6.7 15 11.4 8.1 1.7 0 1.2 2.1 1.5 2.2 1.7 24.1 0.53 1.43 0.74 3.32 4.1 7.01 7.84 8.46 0.42 0.32 0.93 1.42 1.99 0.45 1.99 30.92
242 213 193 220 270 247 211 86 59 63 86 146 203 183 180 79 947 907 940 753 708 599 740 532 942 951 970 915 806 448 655 579
Type of study Visual inspection (in vitro) Periapical radiography (in vivo) Panoramic radiography Periapical radiography Periapical radiography
Panoramic radiography
Max, maxillary; Mand, Mandibular. *Data represent teeth unless indicated otherwise.
Treatment Considerations Central to successful endodontic treatment is a thorough knowledge, respect, and appreciation for root canal anatomy together with careful, thoughtful, and meticulously performed cleaning and shaping procedures. A variety of factors, including crown and root dilacerations, might complicate this treatment (1), so when attempting to perform
endodontic procedures, the clinician must use great care to avoid mishaps in teeth with significant dilacerations (22). In dilacerated teeth, the accepted basic endodontic techniques must be strictly followed, that is, good preoperative and working radiographs, unobstructed access to the root canal orifice, as direct access as possible to the apical third of the canal (within the constraints of the
TABLE 2. Most and Least Affected Teeth Reported to Have Root Dilacerations Race
Most affected teeth
Wheeler (53)
Author(s)
Not stated
Thongudomporn and Freer (51) Neville et al (22)
Not stated Not stated
White and Pharoah (54) Hamasha et al (7)
Not stated Jordanian
Malcic et al (8)
Croatian
Third molars Maxillary lateral incisors Maxillary lateral incisors (1.8%) Maxillary incisors Mandibular anterior dentition Maxillary premolars Mandibular third molars (19.2%) Mandibular first molars (5.6%) Mandibular third molars (24.1%) Maxillary first molars (15.3%) Maxillary second molars (11.4%) Maxillary third molars (8.1%)
JOE — Volume 33, Number 9, September 2007
Least affected teeth Not stated Not stated Not stated Not stated Maxillary and mandibular incisors (1%) Mandibular lateral incisors (0%) Mandibular canines (1.2%) Maxillary central incisors (1.2%) Mandibular second premolars (1.5%)
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Review Article treatment of dilacerated cases, some important considerations in the treatment of such teeth have been summarized in this section.
Diagnosis Diagnosing root dilacerations before commencing endodontic treatment is essential to allow proper and safe use of endodontic instruments within the curved roots (7, 9, 65). Failure to recognize the multi-planar nature of the dilaceration is one of the factors that might contribute to the higher rate of unfavorable outcomes of endodontic treatment of singlerooted teeth such as upper lateral incisors, compared with the number of unfavorable treatment outcomes in multi-rooted teeth (66). To overcome this problem, periapical radiographs that determine the direction of dilaceration are adequate (9). However, such diagnostic findings can be confirmed by a computed tomography scan, which can help to determine the exact position and angulation of the dilaceration (41).
Figure 3. “Bull’s-eye” phenomena in a central incisor with a dilacerated root under orthodontic realignment. Reproduced with permission from Ingle JI, Bakland LK. Endodontics. 5th ed. London, UK. B.C. Decker Inc. 2002:230.
dilaceration), precurvature of all files used (the sharper the canal curvature, the nearer the bend of the file should be to its tip), and thorough irrigation (35). Orthodontic movement of dilacerated teeth might cause severe irreversible resorption of the root, which can severely complicate the endodontic treatment of these teeth (31, 62– 64). Although the body of literature lacks complete, multifarious, and informative research on techniques or materials that might facilitate the endodontic
Access Cavities Direct access to the apical foramen, as much as possible, is an important benefit gained through the access cavity preparation. To provide the most direct access possible to the apical foramen, enough tooth structure must be removed to allow the endodontic instruments to be moved freely within the coronal cavity. However, Luebke has made an important observation that an entire access cavity wall need not be extended in the event that instrument impingement occurs as a result of a dilacerated root. In extending only that portion of the wall needed to free the instrument, a cloverleaf appearance might evolve as the outline form. Luebke has termed this a “shamrock preparation”. In fact, this is a modified outline form to accommodate the instrument unrestrained in the severely curved canals (57). In teeth with crown dilaceration, endodontic treatment might be complex and might require modification of the affected crown. In severe cases, the affected part of the crown might need to be removed, and a provisional prosthesis will need to be placed until a definitive restoration is possible (67). Root Canal System Identification and Preparation In dilacerated teeth, it is often difficult to explore and negotiate the root canals, especially if the state of the pulp has caused apposition and/or resorption of the canal wall. Therefore, when an endodontic file is introduced into the root canal during treatment, it might be blocked by such irregularities, even if the file has been precurved, and this might
TABLE 3. Summary of the Associations between Dilacerations and Various Syndromes Disease
Type of inheritance
Oral features
Smith-Magenis syndrome (58)
Autosomal dominant
Tooth dilaceration, tooth agenesis, taurodontism
Ehlers-Danlos syndrome (59)
Autosomal recessive, autosomal dominant, X-linked recessive
Axenfeld-Rieger syndrome (60)
Autosomal dominant
Congenital ichthyosis (61)
Autosomal recessive
Tooth dilaceration, hypodontia, dentin dysplasia, transmigration, ectopic eruption, delayed eruption Tooth dilaceration, short roots, hyperplastic frenums, underdeveloped maxilla, anterior crossbite, bilateral posterior open-bite, anterior crowding Tooth dilaceration, delayed tooth eruption
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Systemic features Mental retardation, infantile hypotonia, lethargy in infancy, brachycephaly, brachydactyly, ocular abnormalities Joint hyperlaxity, skin hyperextensibility
Incidence of dilaceration 33%
Not stated
Ocular & extraocular malformations
Not stated
Hyperkeratosis of knees and elbows, fish-like scaly skin
Not stated
JOE — Volume 33, Number 9, September 2007
Review Article prevent the operator from reaching the ideal working length (35). Hence, the use of a “scout file” can provide critical information regarding the extent and direction of a root canal dilaceration. Scout files are not just measuring wires; rather, they provide critical information before initiating shaping procedures (1). Another problem in endodontic treatment of these cases is the inability to continuously follow the root canal curvature, and this might result in blocking of the canal, ledging, apical cavitation such as transportation and/or zipping, perforation, and instrument breakage (1, 65). When using manual instrumentation techniques, the flexibility of the instruments with respect to their size must be considered. It is essential to precurve all instruments, and especially those larger than size 20, to allow the files to follow the curve and not just cut in a straight direction (65, 68). The extent of the precurvature required for each instrument will depend on the curvature of the canal, the size of the instrument, and the depth at which the instrument is to be used in the canal (68). Instruments with non-cutting tips and those made from nickeltitanium (NiTi) have been shown to help maintain root canal curvatures in many teeth. However, in general, dilacerated root canals are not suitable for the use of NiTi rotary instruments because of the severe nature and extent of the curvatures that must be negotiated (1). All instruments used within severely curved canals should be discarded after use to prevent breakage within the canal, that is, they should be considered as “single use instruments” (57). Many dilacerated teeth, especially anterior mandibular teeth, will be pulpless and infected with periapical inflammatory lesions (22). Hence, the outcome of root canal treatment will depend largely on complete biomechanical debridement of the canals and the elimination of microorganisms from the root canal system (69). The use of copious irrigation, file recapitulation, and further irrigation should be repeated more frequently in these severely curved canals (1). A multi-visit approach should also be followed, with the use of interappointment intracanal medicaments to increase the predictability of the treatment. Intracanal medicaments are essential to help disinfect the root canal system, especially in areas that are inaccessible to mechanical instrumentation and irrigation, and to change the intracanal environment so microorganisms are not likely, or at least less likely, to be able to survive. Because the value of calcium hydroxide in endodontic treatment is now well-documented, it is proposed to use this material as a medicament in dilacerated teeth (1). To overcome the complexity of reaching calcium hydroxide to the apical third of dilacerated teeth, it has been proposed to mix calcium hydroxide with glycerin rather than with sterile water. It has been shown that glycerin is significantly superior to water in regards to the length of filling and density in the apical third of curved canals (70).
Root Canal Filling Although lateral compaction of curved canals can be very effective in most teeth, this technique might be difficult and sometimes impossible in dilacerated canals. If small, flexible spreaders cannot reach to within 1 mm of the working length, or the taper of the root canal preparation is less than that of the spreader, then lateral compaction is not the technique of choice (57). If the lateral compaction technique is chosen, then spreaders made from NiTi are highly recommended for the filling of severely curved root canal systems (1) because they will penetrate to greater depths and distribute forces more evenly than stainless steel spreaders (57). In nondilacerated cases, as the spreader reaches the desired depth, the master gutta-percha cone is compacted laterally and vertically by moving the instrument in an arc up to 180 degrees, whereas in dilacerated canals, the arc of movement should be limited to 90 degrees or even less (1). JOE — Volume 33, Number 9, September 2007
The use of warm or thermoplasticized gutta-percha techniques might be more applicable in many cases, although these techniques might also be difficult to perform because of the presence of the dilaceration (57). Some studies have shown that in curved canals, ThermaFil (Tulsa Dental Products, Tulsa, OK) results in comparable to (71) or better apical seal than lateral condensation technique (72, 73), although Barkins and Montgomery (74) did not agree with this idea.
Intentional Replantation Intentional replantation of dilacerated teeth is generally not recommended because extraction of the dilacerated tooth might be difficult and could easily result in fracture of the dilacerated root (22, 34, 69), especially if the surgeon is not prepared with a preoperative radiograph (54). Forced Eruption In rare instances in which orthodontic treatment is used to extrude a dilacerated tooth, the dilaceration of the root might make this procedure quite complicated or even impossible (31). Prosthetic Treatment Finite element stress analysis has indicated that root dilaceration concentrates the stresses in the supporting structures if the dilacerated tooth is used as an abutment for a dental prosthesis, so this should be considered as a risk factor in abutment selection. This increased stress might affect the stability and longevity of the abutment tooth and hence also that of the prosthesis. Splinting the dilacerated abutment tooth to an adjacent tooth to obtain a multi-rooted abutment might be an approach to consider in some cases (22, 75). Prognosis The prognosis of dilacerated teeth that require endodontic treatment varies according to the severity of the deformity and the practitioner’s skills (22, 57). It will also depend on many other factors such as the reason why endodontic treatment was required, how much tooth structure remains, and the prognosis for any restoration that is placed on the tooth. It is difficult to predict the prognosis before treatment, and in many cases, the prognosis will not become evident until the practitioner has undertaken initial endodontic treatment to determine whether the canal can be negotiated completely and then adequately disinfected and filled.
Summary and Conclusions Dilacerated teeth are not common, but they do pose a number of diagnostic, management, and prognostic challenges to dental practitioners. The presence of a dilaceration must be identified before treatment, and this can be achieved by a thorough clinical and radiographic examination. Once identified, the effect of the defect on the endodontic and restorative dental management of the tooth can be more fully assessed. Where other treatment (such as extraction, orthodontics) is required, the identification of a dilaceration is equally important to ensure appropriate management.
References 1. Cohen S, Burns RC. Pathways of the pulp. 8th ed. St Louis: Mosby, 2002:94, 243–74, 325–31, 644 –5. 2. Tomes J. A course of lectures on dental physiology and surgery (lectures I-XV). London: 1846 –1848. 3. Shafer WG, Hine MK, Levy BM. A textbook of oral pathology. 4th ed. Philadelphia: WB Saunders, 1983:40, 308 –11. 4. Tiecke RW. Pathologic physiology of oral disease. St Louis: Mosby, 1959. 5. Stewart DJ. Dilacerate unerupted maxillary central incisors. Br Dent J 1978;145:229 –33.
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JOE — Volume 33, Number 9, September 2007