No abstract

In contrast to wild lagomorphs, pet rabbits exhibit a noticeably high frequency of dental problems. Although dietary habits are considered as a major factor contributing to acquired malocclusions, the exact causes and interrelationships are still under debate. In this regard, an important aspect that has not been considered thoroughly to date is the effect of diet-induced phenotypic plasticity in skull morphology. Therefore, we conducted a geometric morphometric analysis on skull radiological images of wild and pet rabbits in order to quantify intraspecific variation in craniomandibular morphology. The statistical analyses reveal a significant morphological differentiation of the craniomandibular system between both groups. Furthermore, the analysis of covariance shows that the force-generating modules (cranium and mandible) vary independently from the force-receiving module (hypselodont teeth) in pet rabbits, which is in contrast to their wild relatives. Our findings suggest that the phenotypic changes in domestic rabbits impact mastication performance and, consequently, oral health. An adequate close-to-nature nutrition throughout the whole life and especially beginning early parallel to weaning (phase of increased phenotypic plasticity) is necessary to ensure a normal strain on the teeth by promoting physiological lateral gliding movements and avoiding direct axial loads.

ZusammenfassungDie Extraktion der Schneidezähne ist bei Kaninchen mit angeborener (Brachygnathie) als auch erworbener Schneidezahnmalokklusion eine etablierte Alternative zur regelmäßigen Zahnkürzung. In der vorliegenden Arbeit wird nach kurzer Erläuterung einiger tierartspezifischer anatomischer Besonderheiten der Schneidezähne das genaue, schrittweise Vorgehen bei der Extraktion der Incisivi beschrieben. Darüber hinaus werden weitere Indikationen zur Entfernung eines oder mehrerer Schneidezähne bei Hasenartigen oder Nagern angeführt.

Acquired dental problems are among the most frequently encountered diseases in pet rabbits. However, early symptoms are often overlooked because the affected animals first appear completely asymptomatic. Alterations from anatomical reference lines according to Böhmer and Crossley applied to standard skull X-ray images, have been shown to be indicative of tooth health problems in pet rabbits. Despite its proven usefulness, there are exceptions in which the anatomical reference lines appear not to be suitable for application. We addressed this issue by quantifying the cranial morphology of a large data set of pet rabbit patients (N = 80). The results of the morphometric analyses revealed considerable diversity in skull shape among the typical pet rabbits, but variance in only a few parameters influences the applicability of the anatomical reference lines. The most substantial parameter is the palatal angle. Specimens in which the anatomical reference lines could not be applied, have a rather large angle between the skull base and the palatal bone. We recommend to measure the palatal angle before applying the anatomical reference lines for objective interpretation of dental disease. Pet rabbits with a palatal angle larger than 18.8° are not strictly suitable for the successful application of the anatomical reference lines.

A traumatic osseous bridge between lumbar transverse processes is a bone formation occurring after severe or even mild trauma of the back. However, only few of the patients with a contusion of the back or a fracture of a lumbar transverse process develop such an osseous bridge. The localisation of the haematoma plays an important role in this process, but myositis ossificans is a mandatory condition. Anamnesis will not lead to traumatic aetiology in all cases, because sometimes the patient is not aware of the fact that a transverse process has been fractured. The diagnosis finally depends on the recognition of the different shapes. The traumatic osseous bridge is characterised by the kind of trauma that causes the fracture of the transverse process. The shapes can be classified as "h", "H", "K", or "Z". Among 72 patients with inter-transverse osseous bridges, only 11 patients have congenital bridges. The congenital osseous bridge shows typical features that can be explained by means of embryogenic and functional dynamic considerations. These symptoms are the O-shape, concavity of the lumbar spine of a pathological nature and the absence of degenerative changes in the corresponding intervertebral space.