The correct term for incisors is incisors, and cracks on incisors are usually occurrences of dental cryptic fracture. The causes of dental cryptic fracture can be categorized into endogenous and exogenous causes, as follows. 1. Internal causes: incisors have weak morphological structures, such as enamel plates in the enamel, which are weak in resistance to external forces and are prone to cryptic cracks. In addition, if the incisors have high tip and steep slope due to abrasion, trauma, caries, etc., the stress will be concentrated during occlusion and cryptic fracture will easily occur. 2. Exogenous causes: sudden biting into gravel, bone slag, etc. in chewing, as well as trauma or medical injury, such as uncontrolled impact of instruments can lead to occult fracture. If you find cracks on your incisors, it is recommended to go to the hospital in time to receive early treatment.