Fractures of the incisive bone can occur when horses bite onto vertical metal bars in the stall; the horse bites the bar with its head in a slightly horizontal position and then suddenly pulls back after positioning its head vertically. Because of the relatively large total width of the upper incisors, they become wedged between the bars, resulting in alveolar fractures with rostral dislocation of the incisors. Such fractures are more common in nervous or curious young horses.
Fractures of the incisive bone may also occur because of the inappropriate use of a mouth gag. Weakened bone in an old horse or inadequate sedation or too wide opening of the mouth can lead to a fracture of the incisive bone.
Fracture caused by the use of a mouth gag.
Typically, the fracture line follows the line of the tooth roots. They can involve just one or multiple teeth. Fractures of the incisive bone are the least stable fractures because the cheek teeth and muscles, which provide some stability, are lacking in this region.
A diagnosis is usually possible based on a clinical examination. A radiographic and endoscopic examination may be performed to rule out additional injuries. These fractures often cause little pain and, if the dislocation is minimal, can be missed and left to heal without treatment.
Fractures of the incisive bone can occur uni or bilaterally.
Dental alveoli are usually involved in these fractures but the teeth themselves are rarely fractured. If dental alveoli are involved, loss of one or more teeth can result either immediately during the traumatic event or later as a result of infection.
In some cases, the teeth roots are fractured (see examples). This requires additional examinations of the teeth at a later stage.
Facial skull fractures
Most trauma to the facial region include large impression fractures with multiple large, but also smaller, fragments that are pushed inward by an external force. Like most head fractures in the horse, facial fractures are usually open and frequently large sections of skin are separated from the bone.
As with fractures of other parts of the skull, the extent of involvement of the facial skull is often underestimated without a thorough radiographic or computed tomographic examination. The surgeons are frequently surprised by the actual extent of the traumatic insult depicted by computed tomography and/or encountered during surgery. The prognosis of facial skull fractures, even large ones, is usually very good because of the abundance of vascular supply to the region and the low physical load most bones encounter during mastication.
Fractures of the facial skull must be examined thoroughly for possible involvement of adjacent structures such as the oral and nasal cavities, sinuses, the orbit, eyes and adnexa, as well as the cerebrum and other parts of the nervous system.