Dysgnathia appears as brachygnathia inferior [1–4] or brachygnathia superior [5]. Other terms used for brachygnathia inferior are overbite, undershot, parrot mouth, prognathia superior whereas brachygnathia superior is referred as underbite, overshot, prognathia inferior [1, 3, 5, 6]. Dysgnathia is a common congenital anomaly in sheep that could be reproduced in a breeding trial with East Friesian sheep [1, 7]. Due to the shortening of specific parts of the mandible, the ovine craniofacial malformation is best described as brachygnathia inferior in sheep [1, 8].
Different measurement approaches have been chosen in sheep with brachygnathia inferior. Nordby et al. [5] found a shortening of the interalveolar part of the mandible and an elongation of the rostral part of the maxilla. The measurements of premolar/molar parts were actually also considered by [5] but sheep with brachygnathia inferior did not show any deviations from standard measurements in these parameters. Measurements of the mandibular distocclusion were frequently based on the distance of the rostral point of the incisor to the dental pad [5, 9, 10]. As indicated by [8] with descriptive statistic programs, different particular parts of the mandible succumb to shortening; other craniofacial abnormalities in sheep were not identified in this study.
As found in the above cited literature (except [8]), measurements were carried out using macerated skulls. Today, due to the progressive development of x-ray technology, animals can also be assessed in vivo. As a starting point for the following study, advanced techniques used for evaluation of x-rays in orthodontics human medicine were adopted. The laterolateral x-ray can be analysed by means of cephalometric measurement points. Structures or positional relationships of skull bones, soft tissues, growth forecasts or treatment options will be shown.
According to [11], there is no uniform nomenclature or classification for the different types of dysgnathia. Even today, the starting point for diagnosing dysgnathia is the classification according to [12] based on molar teeth-occlusion. This is the same also internationally.
Angle-Class I defines normocclusion; Angle-Class II classifies the rostral placement of the maxillary first molar and is subdivided into two groups. Shortened mandible and elongated maxilla and the mandible in posterior position and the maxilla in anterior position [13]. Angle-Class III is used to classify a caudal placement of the maxillary first molar.
Additionally the different affected two Angle Classes could share in altered region (alveolar, skeletal) and changes in main directions (vertical, sagittal and transverse) [11]. Gattinger and Obwegeser [14] divided the malocclusion in the hypo- / hyperplasia of mandible and maxilla.
The projection onto affected sheep, we are trying to implement in this study. A valid normocclusion for the sheep shall be found. Additional changes of other bones of skull which are affected by malformations will be proved. Based on the current human medical knowledge, we will try to find a descriptive definition to represent the exact localization of changes by applying multivariate statistics.