On the Mechanics of Fatigue and Fracture in Teeth

Abstract

Tooth fracture is a major concern in the field of restorative dentistry. However, knowledge of the causes for tooth fracture has developed from contributions that are largely based within the field of mechanics. The present manuscript presents a technical review of advances in understanding the fracture of teeth and the fatigue and fracture behavior of their hard tissues (i.e., dentin and enamel). The importance of evaluating the fracture resistance of these materials, and the role of applied mechanics in developing this knowledge will be reviewed. In addition, the complex microstructures of tooth tissues, their roles in resisting tooth fracture, and the importance of hydration and aging on the fracture resistance of tooth tissues will be discussed. Studies in this area are essential for increasing the success of current treatments in dentistry, as well as in facilitating the development of novel bio-inspired restorative materials for the future.

Influence of structural hierarchy on the fracture behaviour of tooth enamel

“…The authors did not specify the contributions according to the size scales but only according to the mechanisms. Unbroken mineral ligaments have the highest contribution to toughening of enamel with bridging stress intensity between 0.2 and 0.6 MPa m 0.5 , which is approximately 25% of the global toughness in their study [7,13]. The reduction in the local stress intensity factor induced by bridging of organic matrix was estimated to be 0.1 MPa m 0.5 .…”

“…Identifying the features that enable this performance in biological materials with the aim of implementing them to improve engineering materials has become an increasingly important area over many years. This has resulted in renewed interest with further enamel studies employing advanced fracture mechanics being published [7][8][9][10][11][12][13]. These authors reported that bulk enamel exhibits increasing fracture toughness with crack extension (R-curve behaviour) compared with brittle materials that generally have a single value of fracture toughness.…”

“…Thus, we initially summarize the structural features at individual hierarchical levels, and then analyse the role and contribution of the corresponding features to the fracture behaviour (focusing on fracture toughness, fracture strength, deformation curves, toughening mechanisms). An overview of the characterization methods used in the literature [2][3][4][5][6][7][8][9][10][11][12][13]16,25,26,[34][35][36] that are reviewed here for assessing the fracture behaviour of enamel at different length scales can be found in the electronic supplementary material. Finally, we briefly summarize the findings.…”

Fracture tooth reattachment

“…The covering enamel of the tooth resists tooth fracture to a great extent due to its complex microstructure and decussation of enamel rods. Decussation of enamel rods deflects cracks and prevents them from reaching the dentino-enamel junction (Yahyazadehfar et al 2013, Yahyazadehfar et al 2014). If the crack reaches the dentino-enamel junction it well serve as the second defense line against tooth fracture (Dong et .…”

“…Human teeth are very resilient but covered with enamel which is a brittle material (Yahyazadehfar et al 2014). They are designed to withstand loads up to 700 n for repeated millions of cycles during life (Anusavice 1996, p. 90-91, Okiyama et al 2003).…”