Table 1.

Etiological factors of fatigue tooth fracture (after Ellis et al. [9] and Bhanderi et al. [10]).

Etiological factors of tooth fracture
Factors that increase occlusal overloads	-long term unilateral chewing -decreased number of teeth -rotation and tilting of teeth -isolated teeth -awake and sleep bruxism
Factors that decrease tooth resistance to occlusal forces	Non-iatrogenic	-increased levels of dental fatigue in teeth with age -increased number of restored teeth with age -loss of dentin elasticity with age -the tooth structural defect (hypoplasia, dentinogenesis imperfecta) -tooth morphology (steep cusp inclination, deep grooves) -thermal cycling eating habits -tongue piercing
	Odonto-iatrogenic	-excessive removal of tooth tissue in restorative procedures or root canal treatment -tooth dehydration and collagen depletion (higher concentration of sodium hypochlorite in root canal treatment) -large tooth restorations without cuspal protection -use of restorative materials with different thermal expansion coefficient and different mechanical properties compared with the tooth