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

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:

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):

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:

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.

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).^28,29–30

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).^{14,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61–62}

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:

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).

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

Periodontic management

Prosthodontic management

Surgical management

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.