Exploring the biomechanics of taurodontism

Abstract

Taurodontism (i.e. enlarged pulp chamber with concomitant apical displacement of the root bi/trifurcation) is considered a dental anomaly with relatively low incidence in contemporary societies, but it represents a typical trait frequently found in Neandertal teeth. Four hypotheses can be envisioned to explain the high frequency in Neandertals: adaptation to a specific occlusal loading regime (biomechanical advantage), adaptation to a high attrition diet, pleiotropic or genetic drift effects. In this contribution we used finite element analysis (FEA) and advanced loading concepts based on macrowear information to evaluate whether taurodontism supplies some dental biomechanical advantages. Loads were applied to the digital model of the lower right first molar (RM1 ) of the Neandertal specimen Le Moustier 1, as well as to the digital models of both a shortened and a hyper-taurodontic version of Le Moustier RM1 . Moreover, we simulated a scenario where an object is held between teeth and pulled in different directions to investigate whether taurodontism might be useful for para-masticatory activities. Our results do not show any meaningful difference among all the simulations, pointing out that taurodontism does not improve the functional biomechanics of the tooth and does not favour para-masticatory pulling activities. Therefore, taurodontism should be considered either an adaptation to a high attrition diet or most likely the result of pleiotropic or genetic drift effects. Finally, our results have important implications for modern dentistry during endodontic treatments, as we observed that filling the pulp chamber with dentine-like material increases tooth stiffness, and ultimately tensile stresses in the crown, thus favouring tooth failure.

Keywords: Homo neanderthalensis; biomechanics; finite element analysis (FEA); taurodontism; teeth.

Figure 1

Dental tissues and supporting structures for the lower right first molar Le Moustier 1 (RM₁-original), as well as for two further versions where the pulp chamber of the RM₁ was both reduced, to simulate the Homo sapiens condition (RM₁-reduced), and increased, to simulate a hyper-taurodontic root (RM₁-hyper). EDJ, enamel-dentine junction; PDL, periodontal ligament.

Figure 2

(a) Collision detection for Le Moustier 1 RM₁ with the antagonists RP⁴-RM¹ in the occlusal fingerprint analyser software (OFA) during maximum intercuspation contact. (b) The RP⁴-RM¹ are transparent to show the collision (red spots) in the occlusal surface of the RM¹. (c) The FE mesh of RM₁-original consisting of 939 380 10-node tetrahedral elements. B,  buccal; D, distal; L, lingual; M, mesial;PDL, periodontal ligament.

Figure 3

An object was embedded on the occlusal surface of the RM₁ and then a force was applied perpendicular to the object surface (load case 1 – LC1), parallel to the x-axis (i.e. buccally; load case 2 – LC2) and parallel to the y-axis (i.e. mesially; load case 3 – LC3).

Figure 4

The maximum principal stress (MPa) distribution for specimen RM₁-original, RM₁-reduced (i.e. the bifurcation was moved upward) and RM₁-hyper (i.e. the bifurcation was moved downward) with either unfilled (a) or filled (b) pulp chamber (i.e. RM₁-original-F, RM₁-reduced-F and RM₁-hyper-F). Blue spots in the occlusal surface (compressive stress) represent the contact areas with the antagonistic teeth during maximum intercuspation (where the load was applied), whereas red spots represent tensile stresses. B,  buccal; D, distal; L, lingual; M, mesial.

Figure 5

The maximum principal stress (MPa) distribution for specimen RM₁-original, RM₁-reduced and RM₁-hyper when loads are applied on the embedded object (see Fig.3) parallel to the z-axis (LC1), the x-axis (i.e. buccally; LC2) and the y-axis (i.e. mesially; LC3). Red spots represent tensile stresses. B,  buccal; D, distal; L, lingual; M, mesial.