PSI - Issue 25

A.M. Al-Mukhtar / Procedia Structural Integrity 25 (2020) 8–12

9

Author name / Structural Integrity Procedia 00 (2019) 000–000

The most early studies on the crack in teeth were presented in Refs (Cameron 1964, 1976). The fatigue crack propagation and fractography is studied in the region of the dentin-enamel interfaces (Dong and Ruse 2003) (Rasmussen and Patchin 1984). The morphology and the crack propagation path across the dentin-enamel was investigated also in Refs (Gallagher et al. 2003) (Yoldas et al. 2012)(Arola and Rouland 2003; Bechtle et al. 2010; Dong and Ruse 2003; Lin and Douglas 1994; Rasmussen 1984; Rasmussen and Patchin 1984; White et al. 2000)(Lin, Douglas, and Erlandsen 1993; Snyder 1976). The changes in histological structure between the enamel and dentine deflected the crack path since they have different composition and highly mineralized tissues (Lin et al. 1993) (Dong and Ruse 2003). Hence, the dentin-enamel junction (DEJ) will resist the crack propagation. Because it tougher than dentin and enamel. DEJ provides unique biomechanical properties as a crack arrest-barrier, however its ranging from 7 to 15 µm (Imbeni et al. 2005)(Lin et al. 1993). Because its ranging from 7 to 15 µm (Gallagher et al. 2003), SEM was used to investigate the fracture properties near the DEJ (Rasmussen 1984) (Lin et al. 1993) (Koester, Ager, and Ritchie 2008). To the mind of the author, the structures of the enamel-dentin region, and the cohesive between them playing a significant role to arrest the crack, see Ref. (Snyder 1976). The crack growth resistance was higher in young dentin than aged dentin. The brittle teeth due to the aging are very likely for cracking (Cameron 1964) (Cameron 1964). Hence, the early observation of crack will protect the teeth. The thermal fatigue will damage specifically the brittle enamel (Brown, Jacobs, and Thompson 1972)(Brown, Dewey, and Jacobs 1970; Brown et al. 1972; Jacobs, Thompson, and Brown 1973; Lloyd, McGinley, and Brown 1978). The experimental studies on the thermal fatigue in vivo and vitro was studied in Refs (Brown et al. 1972; Lloyd et al. 1978). The flaws, and micro-crack could be easily formed and extended in the brittle enamel (Imbeni et al. 2005). Figure 1 shows the consequences of the crack, and FE simulation of the crack initiation. The review of fatigue, micro-damage initiation, and the crack propagation was addressed in Ref. (Kruzic and Ritchie 2008). The microdamage with time plays a big role in teeth. Because an incomplete fracture causing tooth pain under the pressure and the temperature change (Kruzic and Ritchie 2008)(Cameron 1964). The understanding of the crack behaviour will enhance the treatments and the teeth life. Moreover, the early diagnosis and treatment could prevent the crack growing into the tooth pulp. The main purpose of this work is to show the validity of the Franc2D program to define the crack path in the enamel and dentin using LEFM.

Fig. 1. Crack initiation and propagation consequences in the teeth.