A Review of Equine Developmental Dental Disorders

Craniofacial abnormalities Foals can develop a number of developmental abnormalities of their craniofacial bones that cause dental malocclusion and dysfunction. Although some of these abnormalities such as over jet and overbite (“parrot mouth”) are often regarded as being primary dental abnormalities, these dental abnormalities are just one manifestation of an underlying craniofacial skeletal abnormality. Consequently, correction of the dental abnormalities, such as reducing dental overgrowths, will not affect the underlying craniofacial abnormality.

Overjet and overbite Many horses have some degree of overjet, (“overshot jaw”) i.e. where the occlusal aspects of the upper incisors lie rostral to the occlusal aspects of the lower incisors. If very marked and untreated, cases of severe overjet will often develop overbite (“parrot mouth”) where the upper incisors lie rostral to the lower incisors as above but also now lie in front of the erupted crowns lower incisors due to marked overgrowth of the upper incisors and/or to ventral curvature of the premaxillary (incisive) bones due to absence of occlusal contact. Overjet and overbite are aesthetically undesirable but surprisingly, these problems rarely cause difficulty in prehension. As the more rostrally situated incisors (01s) have the least occlusal contact, they overgrow most and so affected horses develop a convex appearance of their upper incisor occlusal surface (“smile”), which should be gradually reduced in stages if it is pronounced. The main clinical significance of incisor overjet or overbite are the concurrent CT disorders usually present, due to the upper CT row being rostrally positioned in relation to the lower CT row as discussed below […]