SPECIAL ISSUE ARTICLE Crack simulation in human teeth Ahmed Al-Mukhtar 1,2 | Carsten Könke 3 1 Al-Hussain University College, Iraq 2 Institute of Structural Mechanics, Bauhaus-Universität Weimar, Germany 3 Institute of Material Research and Testing (MFPA), Institute of Structural Mechanics, Bauhaus-Universität Weimar, Weimar, Germany Correspondence Ahmed Al-Mukhtar, Al-Hussain University College, Iraq; Institute of Structural Mechanics, Bauhaus- Universität Weimar, Germany, Marienstrasse 15, 99423 Weimar, Germany. Email: almukhtar@hotmail.de Abstract Early observations of cracks protect the teeth. The crack in teeth initiates due to the flaws, defect, or inappropriate fillings design. The brittleness allows the crack to extend from any notches over the enamel due to the lower plasticity. Therefore, in this issue, linear elastic fracture mechanics (LEFM) assumptions will be used instead of the elastic–plastic fracture mechanics (EPFM). Tradi- tionally, the vertical crack in the teeth is predominated. The load distributions over the crown and the cyclic loading will propagate the crack. There are lim- ited works trying to simulate the crack in the teeth. In this work, the crack path (CP) and the fracture behavior of the tooth have been simulated. It was shown that LEFM is sufficient for such simulation. KEYWORDS crack, fracture mechanics, Franc2D, linear elastic, stress concentrations, teeth 1 | INTRODUCTION The existence of cracks reduces teeth toughness. Understanding teeth failure aims to decrease the damage risk; see Al-Mukhtar. 1 In addition, it gives an insight for repair and restoration. Early observations of cracks will protect the teeth. The dentin–enamel margins resist crack propagation because of their fracture toughness. Enamel–dentin inter- faces serve as a crack arrest. 2,3 Aged teeth suffer from brittleness and rapid cracking. 4 Hence, the early observation of cracks will protect the teeth's body. The earliest studies on the crack in dentin were carried in 1964. 4–6 The crack growth resistance in young dentin is higher than in the aged dentin. Because the effect of the plasticity or bridging in teeth enamel can be neglected, linear elastic fracture mechanics (LEFM) is predominantly used because the fracture toughness mostly comes from the bridg- ing in the dentin–enamel junction (DEJ) and from the dentin. In addition, few studies used the LEFM and carried out the fatigue experiments in teeth. 7,8 Moreover, the majority of the crack path (CP) occurs in the enamel in which the brittleness is predominant, and the linear elastic is considered. Mainly, the enamel also suffers from thermal fatigue. 9–12 In general, fatigue as an expression of cyclic effect on the teeth will increase the crack propagation. This crack propagation will increase due to the flaws and the microcrack inside the brittle enamel. 7 The incomplete fracture causes tooth pain under bite pressure and temperature change until the complete fracture as the next step. 4,13 LEFM can be used for teeth enamel as well as in cortical bone because no moderate plasticity or zero plasticity has existed. In this work, fracture analysis code (Franc2D) as based on LEFM assumptions is used. The CPs and stress con- centrations are presented. Received: 19 May 2020 Revised: 27 July 2020 Accepted: 28 July 2020 DOI: 10.1002/mdp2.200 Mat Design Process Comm. 2020;1–6. wileyonlinelibrary.com/journal/mdp2 © 2020 John Wiley & Sons, Ltd. 1