Shedding deciduous teeth can be a source of oral irritation in horses that are 2–5 yr old. Deciduous tooth caps can become loosened, displaced, or fractured, leading to problems with mastication and biting. Abnormal eruption of permanent teeth is commonly a sequela of mandibular or maxillary trauma, eg, incisor avulsion fractures in cattle and horses in which the developing dental bud of the permanent tooth is damaged by the fracture itself or by the repair process. In horses, delayed eruption or impaction of cheek teeth is a common cause of periapical infection. This particularly affects the second and third cheek tooth (premolar 3 [Triadan 07s] and premolar 4 [Triadan 08s]) in both the upper and lower arcades and is a sequela of dental overcrowding. Medial displacement of the third cheek tooth is another form of abnormal eruption due to overcrowding.