Ovine craniofacial malformation: a morphometrical study.

Craniofacial malformation in 64 sheep was phenotypically described as mandibular distoclusion. Digital radiographs were examined in order to determine the degree of morphological changes in certain bones of the skull. Therefore, laterolateral standardised digital radiographs were used to determine anatomic reference points. Subsequently, five reference lines were defined and 16 linear and seven angular measurements were determined to describe malformations in the bones of the skull. Statistical analysis revealed a significant shortening of the rostral part of the corpus mandibulae and of the ramus mandibulae. However, the molar part of the mandible remained unchanged. These morphological changes caused premolar and molar malocclusion. No further craniofacial abnormalities, such as an elongation of the maxilla or of the incisive bone, were identified. In conclusion, the phenotypically observed mandibular distoclusion is caused by a shortening of specific parts of the mandible. This form of ovine craniofacial malformation is therefore best described as brachygnathia inferior.