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Taurodontism part 2: biomechanics, differential diagnosis, clinical implications and management

From Volume 46, Issue 3, March 2019 | Pages 266-278

Authors

Muhammad Hasan

Assistant Professor and Head, Department of Operative Dentistry, Sir Syed College of Medical Sciences (Dental Section), Karachi, Pakistan

Articles by Muhammad Hasan

Abstract

The first article described history, aetiology, molecular signalling mechanism, epidemiology and classification of taurodontism. This final article of the two-part series focuses on the biomechanics and other clinical aspects of taurodontism.

In certain disorders, especially during initial stages, the teeth can appear taurodontic and may complicate diagnosis. These conditions, along with their key features, are highlighted in this article, as are several syndromes relevant to taurodontism. In addition, the sections on imaging and clinical considerations discuss diagnostic methods and management of taurodontic teeth, respectively. Taurodontism, especially in severe forms, can be a root canal challenge. Sometimes, multiple taurodontism is seen in association with various syndromes and perhaps may assist in early diagnosis.

CPD/Clinical Relevance: Taurodontism has clinical implications in various dental disciplines, such as endodontics, surgery, orthodontics and prosthodontics. However, it is most relevant to endodontists as this deviation exclusively affects the internal anatomy of teeth.

Article

The second article of this two-part series aims to review the biomechanics of taurodontic teeth, their diagnostic considerations, relevant syndromes, imaging methods, clinical management and prognosis. The hallmarks of taurodontism are:

  • Vertically enlarged pulp cavities;
  • Apically displaced pulpal floor and furcation;
  • Lack of cervical constriction; and
  • Short bulbous roots that are sometimes fused with each other.1
  • Taurodontism can occur in isolation, or in multiple teeth, unilaterally or bilaterally, in a normal population or associated with syndromes with a varying degree of severity (Figure 1).2 It is most commonly found in molars, followed by premolars and mandibular anterior teeth.3

    Figure 1. A panoramic view of a female patient showing multiple taurodontism in maxillary and mandibular molars. Affected teeth (marked red): UR7, UR8, UL7, UL8, LR7, LR8, LL7 and LL8. Patient is non-syndromic.

    Biomechanics of taurodontic teeth: Are there any advantages of taurodontism? Why was this anomaly common in the Neanderthals?

    Recent research studied the biomechanics of taurodonts on digital models of Neanderthal specimen ‘Le Moustier 1’. This study was conducted to help understand the reasons behind high frequency of taurodontism found in Neanderthals. To evaluate this, four hypotheses were projected as possible factors responsible for taurodontism:

  • Biomechanical hypothesis (ie adaptation to a specific occlusal loading regimen);
  • Adaptation to a high attrition diet to prolong tooth longevity and to support the health of periodontal apparatus;
  • Pleiotropic effects; or
  • Genetic drift effects.4
  • In this experiment, finite element analysis (FEA) and other advanced loading methods were used. The digital models of lower right first molar (RM1), along with reduced and hypertaurodontic models of RM1 of Neandertal specimen ‘Le Moustier 1’ were subjected to loading conditions. In addition, a simulated test was performed to evaluate para-masticatory efficiency of taurodontic teeth. In this test, an object was placed between teeth and pulled in various directions. The results from simulated tests did not reveal any significant biomechanical advantage of taurodontic teeth during para-masticatory function and, hence, rejected the biomechanical hypothesis. The authors of this study concluded that the high frequency of taurodontic teeth in Neanderthals most probably had evolved as an adaptive mechanism to high attrition diet routine or due to pleiotropic effects.4 It could also be a result of genetic drift and bottleneck effects, consequently elucidating the limited morphological discrepancy observed in Neanderthals.

    The researchers highlighted another point relevant to modern dentistry, namely that the pulp cavity, when filled with dentine-like restorative material, enhanced tooth stiffness. This in turn had a negative impact on the dental crown as the tensile stresses were also increased, ultimately contributing towards tooth fracture.

    Yet, in another study,5 scientists set out to investigate molar root morphology among Neanderthals (Middle and Late Pleistocene), Aterian (Late Pleistocene) and recent Homo sapiens.

    They sought to evaluate whether root morphology can act as a differentiating feature among species, and whether variances in root morphology suggest differences in tooth functionality.

    Scientists used microtomography imaging to study and quantify internal and external anatomy of specimen molars. The advanced imaging helped researchers in the evaluation of 3D root morphology. Through univariate and multivariate statistical analysis of the specimens, researchers found some similarities and differences between the teeth of Neanderthals (penecontemporaneous) and Aterian (H. sapiens):

  • Similarities in pulp volume and root length;
  • Differences such as pyramidal roots and volume of dental tissue.
  • On the other hand, recent H. sapiens had smaller molar proportions than Neanderthals and Pleistocene H. sapiens, but possessed reduced dental volume similar to Pleistocene H. sapiens and a smaller root to crown ratio relative to Neanderthals. In addition, the first molar's root surface area of Neanderthals and recent H. sapiens happened to be the greatest. Contrary to this, the second molar comprised the largest root surface area in Aterian H. sapiens. These differences among root surface area suggest that a distinct occlusal loading scheme was present in Neanderthals as compared to Pleistocene and recent H. sapiens.5

    Studies indicate that the Neanderthals had specific biomechanical alterations in their dentition, which gave rise to their increased masticatory force generated during consumption of highly abrasive foods.6 The Neanderthals had a reduced arch length, either as a result of a posterior shift of anterior teeth coupled with an anterior shift of molars or a reduction in mesio-distal dimension of molars that placed them in a forward position. This resulted in first and second molars being placed in an ideal position for the generation of higher masticatory forces, as an adaptive mechanism to a high attrition diet.6,7

    A number of studies debate in favour of selective advantage of taurodontic permanent molars. First, a large pulp cavity is thought to be an advantage among populations that consumed an attrition causing diet, since the large pulp cavity compensates for the occlusal tooth surface loss by laying secondary dentine. Secondly, a deep-seated furcation of taurodont molars secures this region from the oral environment and hence reduces the chances of periodontal disease.8,9,10-11

    Diagnostic considerations

    Previously, external morphological features have been used to diagnose taurodontism. However, it is difficult to rely on them alone and nowadays internal anatomical characteristics are used to diagnose this anomaly.12 The diagnosis of taurodontism is based on an evaluation of the following three aspects:

  • Clinical findings;
  • Internal morphology; and
  • Radiographic features.
  • Clinical findings

    Teeth affected by taurodontism appear to be similar to normal teeth from a clinical standpoint as they have a normal crown. Since these teeth have an unusually long root trunk developed at the expense of roots, the only feature identifiable is the lack of an inter-radicular area during periodontal probing of multi-rooted teeth. This feature is not identifiable clinically in a healthy dentition unless the area is probed.13,14 Therefore, taurodontism can be stated as a developmental anomaly found by chance during radiographic assessment.15

    Internal morphology and radiographic features

    Taurodont teeth demonstrate a number of internal and radiographic features that make them dissimilar from normal teeth and, hence, an endodontic challenge. The following are the characteristics of multi-rooted taurodont teeth (Figure 2):16,17,18,19,20,21,22,23,24-25

  • Cylindrical or rectangular-shaped teeth;
  • Vertically enlarged pulp cavity extending below CEJ;
  • High roof of pulp cavity;
  • Elongated body of tooth (tall root trunk);
  • Absent or under-developed cervical constriction at the CEJ;
  • Apical displacement of furcation;
  • Thin cervical dentine around canal orifices;
  • Small to absent inter-radicular area;
  • Short roots and root canals.
  • Figure 2. (a, b) Radiographic images showing treatment of a hypertaurodontic second mandibular molar. (Courtesy of John Wiley and Sons. From Parolia A, Khosla M, Kundabala M. Endodontic management of hypo-, meso- and hypertaurodontism: case reports. Aust Endod J 2012; 38: 36–41).

    Differential diagnosis

    There are certain developmental disorders that mimic taurodontism, such as amelogenesis imperfecta and dentinogenesis imperfecta26 (Figures 3 and 4). Large-sized pulp cavities (characteristic of taurodontism) are also seen during the initial stages of these disorders. However, underdeveloped roots and the presence of an open apex distinguish them from taurodontism27 (Figure 5). Other metabolic disorders that also exhibit large pulp cavities are rickets, hypophosphatasia and pseudo-hypoparthyroidism (Table 1).28,2930

    Figure 3. (a, b) Clinical and radiographic images of dentinogenesis imperfecta. Apart from characteristic features of this condition (extensive attrition and amber-yellow discoloration), large pulp cavities are evident on radiographs. (c) Large pulp cavities mimicking taurodontism during the early stage of disorder, although taurodontism can occur in association with dentinogenesis imperfecta. (Courtesy of John Wiley and Sons. From Li F, Liu Y, Liu H, Yang J, Zhang F, Feng H. Phenotype and genotype analyses in seven families with dentinogenesis imperfecta or dentine dysplasia. Oral Dis 2017; 23: 360–366).
    Figure 4. Vitamin D resistant rickets showing physical and dental features. (a) Physical signs: rachitic rosary (pronounced costochondral junction), short stature, stunted growth and bowed legs. (b) Dental radiographic features: periapical radiographs showing widened pulpal space of LR deciduous second molar, mimicking taurodontism. (From Choubey S, Meena D, Bafna Y, Kulkarni S, Swamy N. Diagnosis of a rare genetic disorder in the dental clinic: case report on vitamin d-resistant rickets. Int J Dent Case Reports 2013; 3: 16–19).
    Figure 5. Oral manifestations of vitamin D resistant rickets. (a) Clinical presentation of a child with partially edentulous maxillary arch (with only three posterior primary teeth) and edentulous mandibular arch. (b) Panoramic radiograph exhibiting hypoplastic alveolar ridges, several absent deciduous teeth, permanent molars with large pulp cavities and short roots with ill-defined lamina dura. (From Rathore R, Nalawade TM, Pateel D, Mallikarjuna R. Oral manifestations of vitamin D resistant rickets in orthopantomogram. BMJ Case Reports 2013; 2013: bcr2012008318).

    Developmental Conditions Differentiating Features from Taurodontism
    Amelogenesis imperfecta Incompletely developed roots, open apices (during initial stages of condition)
    Dentinogenesis imperfecta
    Metabolic Conditions Differentiating Features from Taurodontism
    Rickets Teeth have a normal appearance and form with widened pulp cavities
    Hypophosphatasia
    Pseudo-hypoparthyroidism

    Association with systemic syndromes

    Taurodontism most frequently occurs in isolation. A polygenic inheritance has been shown to be the cause of various forms of expression and the anatomical features seen in taurodontism.31 However, it can also be seen in association with syndromes.32 Several case reports show a higher prevalence of taurodontism when associated with developmental disorders and how it affects multiple teeth in these patients (Table 2).14,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,6162


    Syndromes Key Oral Features/Manifestations
    Cleft lip and palate Ectopic eruption (primary maxillary anterior dentition), oro-antral fistulas, congenitally missing teeth, malformed and mal-rotated teeth and taurodontism, supernumerary teeth, malocclusion
    Amelogenesis imperfecta Hypoplastic or hypomaturative enamel, enamel defects, taurodontism (infrequently associated)
    Hypodontia Agenesis of permanent teeth (at least 2 and less than 6), taurodontism, diastemas and microdonts
    Down's syndrome Hypodontia (lateral incisors most commonly absent), delayed eruption, altered teeth morphology such as peg laterals, taurodontism, periodontal disease; mainly due to impaired host response, and lower incidence of caries (due to high salivary IgA concentrations directed towards Streptococcus mutans)
    Klinefelter syndrome Periodontal disease, taurodontism, high caries rate, prognathism and reduced facial height
    Lacrimo-auriculo-dento-digital syndrome (Levy Hollister syndrome) As the name indicates, it affects lacrimal system, ears, dentition and fingers. Oral features: xerostomia, high caries rate, peg-shaped incisors and microdontia, enamel hypoplasia, taurodontism and malformed molars
    Barber-Say syndrome Taurodontism, macrostomia, broad alveolar ridges, gingival fibromatosis, delayed tooth eruption and malocclusion, prognathism
    Tricho-dento-osseous syndrome Hypertaurodontism of first mandibular molars (frequent finding), thick and sclerosed cortical plates, severe amelogenesis imperfecta
    Tricho-onycho-dental syndrome Dentin dysplasia, taurodontism of molar teeth, hypoplastic-hypomaturative enamel
    Mohr syndrome (oral-facial-digital syndrome type II) Taurodontism, high-arched palate, tongue nodule(s), retromicrognathia, feline lip (pseudocleft of upper lip)
    Van der Woude syndrome Cleft lip (common), cleft lip and palate, or only cleft palate, hypernasal voice, bifid uvula, fusion of teeth, taurodontism, hypodontia (mainly premolars), ankyloglossia, syngnathia and high-arched palate
    Smith-Magenis syndrome Hypodontia (commonly premolars), taurodontism, high caries rate, root dilacerations
    Hypohidrotic ectodermal dysplasia Hypodontia, hypohidrosis, hypotrichosis, xerostomia, dysphagia, congenitally missing and malformed teeth, moderate to severe taurodontism, crown/root dysmorphism, microdontia, conical crowns and weak enamel.
    Oligodontia Agenesis of more than 6 teeth, presence of taurodontic molars, reduced dimensions of teeth
    Sex chromosomal abnormalities Taurodontism
    Thalassemia major Absent or faint inferior alveolar nerve canal and thin mandibular cortex, taurodonts, spiky-short roots, diminished lamina dura
    McCune-Albright syndrome Taurodontic teeth, high caries rate, malocclusion, rotated teeth. Generalized spacing between teeth may be present due to expansion of fibro-osseous lesions
    Williams syndrome Malformed teeth (screwdriver-shaped teeth), spacing between teeth, malocclusion, taurodontism, hypoplasia, pulp stones
    Lowe syndrome (Oculo-cerebro-renal syndrome) Underdeveloped maxilla and mandible, impacted teeth, generalized periodontal disease coupled with extensive bone loss, taurodontism
    Wolf-Hirschhorn syndrome (4p-syndrome) Cleft lip and palate common, taurodontism, agenesis of multiple permanent teeth (mainly premolars and molars), and over-retained primary teeth

    Nevertheless, a few case reports have shown multiple taurodontism without syndromes.20,63 The following are the developmental disorders in which taurodonts are frequently seen:

  • Cleft lip and palate;31
  • Amelogenesis imperfecta;34,35
  • Hypodontia36,3738
  • Down's syndrome,39,40,41,4243
  • Klinefelter syndrome;44,4546
  • Lacrimo-auriculo-dento-digital syndrome;47
  • Barber-Say syndrome;48
  • Tricho-dento-osseous syndrome;49
  • Tricho-onycho-dental syndrome;50
  • Mohr syndrome;51
  • Van der Woude syndrome;52
  • Smith-Magenis syndrome;53
  • Hypohidrotic ectodermal dysplasia;54
  • Oligodontia;55
  • Sex chromosomal abnormalities;56,5758
  • Blood dyscrasias such as Thalassemia major;59
  • McCune-Albright syndrome;60
  • Williams syndrome;61
  • Lowe syndrome; and
  • Wolf-Hirschhorn syndrome.62
  • For syndromic patients presenting with taurodontism, it is imperative to constitute a team of professionals and have a holistic approach for their management.

    Conventional radiography vs CBCT

    Periapical and panoramic radiographs have long been used as the method of choice for both identification and biometric evaluation of taurodontism. However, these radiographs have an inherent problem of providing a limited 2D view20 and, hence, can only assist in formulating initial diagnosis. Other drawbacks of conventional radiography include image foreshortening or elongation, distortion, overlapping, magnification and non-reproducibility. Whereas in panoramic radiographs there is frequently lack of definition, superimposition of structures, teeth appearing rotated (especially premolars) and images sometimes having motion blur due to movement of patient.63,64-65

    Therefore, conventional radiography should be used for initial assessment only and a detailed view of taurodonts should be obtained with cone beam computed tomography (CBCT). On evaluating the CBCT image of a hyperdont, special attention should be given to the thickness of the pulpal floor adjacent to root canal orifices, and the number of root canals should also be noted. Furthermore, canal curvatures (especially in bucco-lingual direction) can also be identified through the CBCT image.

    While there are not many studies advocating CBCT use for managing taurodonts, in the author's opinion it may be worthwhile for the clinician to obtain a pre-operative CBCT image, especially for hyperdonts. This will aid in the prevention of accidental events, such as perforations in cervical regions and missed root canals. However, it is prudent to adhere to ALARA guidelines and unwarranted use of radiation should be avoided, such as in cases of mild to moderate taurodontism.

    Clinical management

    Taurodontism mainly affects molar teeth, in both permanent and deciduous dentitions, the former being more common. It has three classes; mild, moderate and severe, based on the degree of apical displacement of the pulpal floor.

    When it comes to the management of taurodonts, it may not be much different from normal teeth requiring endodontic treatment. The challenge is to manage the severe form of cases, such as hyperdont molars that show most morphologic deviations of a root canal system, thus influencing endodontic treatment. However, taurodonts can also have clinical implications in prosthodontics, extractions, intentional implantation, orthodontics and periodontics (Table 3).


    Clinical Parameters Concerns/Reasons
    Endodontic
    Excessive bleeding upon access Can mislead clinician to see excessive bleeding as perforation
    High volume of pulp tissue Along with mechanical excavation, a high volume and concentration of irrigant may be needed to disintegrate extra pulpal tissue
    Irrigation and preparation Complex morphology may need ultrasonic irrigation
    Vertically enlarged pulp chambers and apically displaced furcation Difficult visualization of the pulpal floor and instrumentation of root canals
    Root canals (number, shape, location, negotiation) It is difficult to confirm in hyperdonts. CBCT and magnification recommended
    Obturation Multiple apical channels can be present, such as in hyperdonts, therefore it is important to seal all and avoid material extrusion. Alternatively, vital pulpotomy can be performed with root canal pulp left intact.
    Post placement is discouraged Short roots and thin cervical region around orifices increase chances of perforation.
    Periodontic
    Periodontally stable A long root trunk (especially in hyperdonts) makes furcation lie well below the crest of alveolar bone and less susceptible to bacterial intrusion
    Prosthodontic
    May not be an ideal prosthetic abutment Lack of long and divergent roots
    Surgical
    Extraction is less complicated Lack of long and divergent roots
    Intentional replantation could be a problem Taurodonts have a bulbous apical area that may pose a problem
    Orthodontic
    May not be suitable for anchorage Lack of long and divergent roots

    Endodontic management

    The anatomical challenges encountered during endodontic treatment are profuse bleeding upon access, difficult visualization of deep pulp cavity and identification of orifices, unpredictable disinfection of complex pulp-radicular system, mechanical preparation of thin cervical areas, short roots and their obturation. Other complications include high chances of perforation, accidental extrusion of irrigant or obturant from short roots, and increased stiffness of a tooth upon filling the large pulp cavity with dentine-like restorative material.4

    Vital pulpotomy

    In the case of irreversible pulpitis, ordinary root canal treatment is indicated. For complex cases such as hyperdonts, where the pulp cavity extends up to the apex and divides into several portals of exit, the recommended treatment is vital pulpotomy.15,66 However, if periapical pathology is evident then pulpectomy becomes necessary.

    Excessive bleeding upon access

    A vertically elongated pulpal cavity harbours extra pulpal tissue. Once inflamed, this excess tissue causes profuse bleeding during extirpation and is often difficult to control, raising a false alarm of perforation to the clinician. After coronal pulp extirpation, bleeding usually subsides and instrumentation of apically positioned orifices becomes practical.

    Irrigation and preparation

    With the advent of modern irrigation systems, such as ultrasonics and water lasers, it would be both effective and time saving to use root canal disinfection in taurodontism. A higher concentration and temperature of sodium hypochlorite (NaOCl) will rapidly disintegrate excess pulpal tissue. This higher concentration might also be useful for disinfecting thin cervical regions, where instrumentation carries a risk of perforation.

    Deep-seated orifices

    Reaching root canal orifices will require complete removal of coronal pulpal tissue. Owing to the long pulp cavity and apically displaced furcation, the root canals are deep-seated, making them difficult to identify and manipulate with instruments. To accomplish this task, prior knowledge of the anatomy, use of magnification aid and a good skill set are necessary.

    Root canal configuration (number, shape, location and negotiation)

    Taurodonts demonstrate a wide variation of root canal anatomy such as apically positioned root canals, their number, configuration, and the likelihood of accessory root canals. While instrumenting the short roots, a precise control of working length is essential to prevent extrusion of the gutta-percha. To achieve this, it is best to use a combination approach that involves radiographic estimation, an electronic apex locator, a paper-point test and, finally, a dry-run gutta-percha radiograph. Depending on the severity of taurodontism, each case brings its own unique challenges and may require advanced tools, such as cone beam computed tomography and a dental operating microscope.

    Obturation

    Root canals in taurodontism can either be short or present in the form of multiple channels exiting from an elongated root trunk, as seen in hypertaurodontism. Obturation in such cases is a challenge and could be carried out by providing an initial apical cork of gutta-percha followed by a back-fill with thermoplasticized gutta-percha (continuous wave compaction). This will completely fill irregularities of the long rectangular pulp chamber of hyperdonts (which extend well below the crest of alveolar bone).

    Post-space preparation

    Posts can be placed but with caution, especially in hyperdonts. Because these teeth have thin cervical dentine around the orifices, a deep-seated furcal floor and short roots, Tsesis et al have advised against post-placement for reconstruction.24

    Restoration of endodontically treated tooth

    In taurodonts with reduced crown height (eg due to attrition), or where a post is contra-indicated, a bonded restoration can be used as a core build-up and small tags can be placed inside the canal orifices to improve retention. However, Benazzi et al found that the filling of the entire pulp cavity of taurodonts with dentine-like restorative material increased their stiffness. He suggested that this could contribute towards tooth fracture, as high stiffness increased tensile forces in the crown.4 Additional measures for cases with reduced crown height or limited ferrule include orthodontic extrusion or crown lengthening surgery.

    Periodontic management

    Overdeveloped root trunk

    An elongated root trunk and a below the alveolar crest inter-radicular region might protect a tooth from the oral environment, hence assisting in the prevention of periodontal disease. Moreover, these teeth do not have external surface aberrations and possess a normal anatomical crown.

    Reduced surface area of roots

    In contrast, short and less diverged roots reduce the surface area of taurodonts, thereby decreasing contact with bone. Hence, this may have a negative impact on the stability of taurodonts within the alveolar socket.

    Prosthodontic management

    Crown preparation

    Due to lack of cervical constriction and a reduced cervical bulge, it might be easier and relatively conservative to perform crown preparation on these teeth.

    Prosthetic abutment

    Short roots provide a reduced surface area and limited anchorage into the alveolus as compared to long and divergent roots of a normal tooth. Therefore, a hyperdont might not be a suitable abutment for fixed bridge prosthesis.67 The author was unable to find significant data on this hypothesis, therefore, this needs to be confirmed through suitable research.

    Surgical management

    Intentional replantation

    Mesodonts and hyperdonts have a bulbous apical area, which may complicate extraction, resulting in damage to the apical region that is critical to the success of the procedure. Therefore, intentional replantation could pose a challenge and should be done with careful planning.

    Extraction

    Extraction is less complicated due to an elongated body and short coalesced roots. This is because a long root trunk with shortened roots reduces the firmness of the tooth within the socket.

    Orthodontic management

    From an orthodontic standpoint, these teeth are not ideal for anchorage purposes due to the lack of long divergent roots that provide strength and reliability.67

    Prognosis

    The author was unable to find failed endodontic cases of taurodonts in the literature. Therefore, it could be opined that taurodonts do not have an increased failure rate after endodontic treatment as compared to normal teeth after treatment, providing that they are carefully managed. Taurodonts might be, to a certain extent, more resistant to occlusal attrition and pulpal exposure (owing to their large-sized pulp cavity and resultant enhanced ability to lay secondary dentine), as depicted in Neanderthals who consumed a high attrition diet and typically showed taurodontism.

    Nevertheless, these hypotheses should be substantiated through appropriate studies. In contrast, these teeth offer more resistance from periodontal disease entering the furcal region because of their long root trunk seated within the alveolar bone.

    Summary

    This article reviewed the biomechanics of taurodontic teeth and discussed various factors that may influence the functionality of these teeth. The clinician also needs to be heedful of the developmental disorders that could mimic taurodontism, and look out for key distinguishing features prerequisite to formulating a differential diagnosis. Furthermore, multiple taurodontism sometimes occurs in association with syndromes and, perhaps, may assist in early diagnosis.

    The author advocates the use of cone beam computed radiography (in addition to radiographs) for handling difficult cases. In such cases, the teeth may take a rectangular or cylindrical shape and can complicate endodontic treatment.