Michal Kyllar

The pig as an experimental model for clinical craniofacial research

The pig represents a useful, large experimental model for biomedical research. Recently, it has been used in different areas of biomedical research. The aim of this study was to review the basic anatomical structures of the head region in the pig in relation to their use in current research. Attention was focused on the areas that are frequently affected by pathological processes in humans: the oral cavity with teeth, salivary gland, orbit, nasal cavity and paranasal sinuses, maxilla, mandible and temporomandibular joint. Not all of the structures have an equal morphology in the pig and human, and these morphological dissimilarities must be taken into account before choosing the pig as an experimental model for regenerative medicine.

Gingival Thickness in Dogs: Association with Age, Gender, and Dental Arch Location

Reduced gingival thickness is one of many factors that might predispose humans to periodontal disease and subsequent gingival recession. Gingival thickness differs between individuals, and is associated with age, gender, and location on the dental arch. Different gingival phenotypes exist in the human population according to the thickness of gingiva. Similar information on gingival phenotypes in dogs is unknown. The aim of this study was to investigate the thickness of the gingiva in dogs and its relation to age, gender, and location on the dental arch. For this study, 48 dogs of comparable size (40-cm at withers) were divided into three groups according to their age as follows: < 2-years of age; 2 to 8-years of age; > 8-years of age. Gingival thickness was measured in both the mandible and maxilla using a transgingival probing technique. The graded probe was inserted midway into the attached gingiva at the level of each tooth class region. Young and middle aged dogs had significantly thicker gingiva (1.67 ± 0.17 mm and 1.68 ±0.18 mm, respectively) compared with older dogs (1.54 ± 0.16 mm). There was no significant difference in gingival thickness based on location or gender. Generally, the gingiva was thicker at the level of large teeth such as canine and carnassial teeth. Regions of thinner gingiva at the level of incisor and premolar teeth correlated with the regions of highest prevalence of periodontal disease found in previous studies.

Radiography, Computed Tomography and Magnetic Resonance Imaging of Craniofacial Structures in Pig

The pig has recently become popular as a large animal experimental model in many fields of biomedical research. The aim of this study is to evaluate the basic anatomical structures in the head region of the pig to lay the groundwork for its practical clinical usage or pre‐clinical research in the future. We used three different diagnostic imaging methods: radiography, computed tomography (CT) and magnetic resonance imaging (MRI). The analysis showed that radiographic imaging is suitable only for general evaluation of the facial area of the pig skull. CT images showed excellent spatial definition of bony structures of the whole craniofacial area, and MRI images revealed fine soft tissue details. Radiography is preferentially suited to general assessment of bone structures of the facial skeleton; however, the thick layer of adipose tissue in the craniofacial region of the pig makes the imaging of some parts difficult or even impossible. CT is useful for revealing morphological details of mineralized tissues, whereas MRI is more suitable for soft tissue analysis and the detection of subtle pathologic changes in both bone and soft tissues. Therefore, before using pigs as an experimental model in craniofacial research, it is necessary to evaluate the suitability and disadvantages of potential imaging methods and how appropriate they are for accurate visualization of desired structures.

Morphometric assessment of the canine hip joint using the acetabular angle of retrotorsion.

Morphometric assessment of the canine hip joint using acetabular angle of retrotorsion was used in this study. The aim of our study was to compare the acetabular angle of retrotorsion (AAR) with values of the Norberg angle (NA) and the hip score (HS) in the Leonberger dog breed and to determine the cut-off point of AAR that distinguish between normal and dysplastic hip status on the basis of Fédération Cynologique Internationale (FCI) hip evaluation. Retrospective analysis of NA and AAR was measured from standard ventrodorsal pelvic radiographs with extended femurs in 387 Leonberger dogs (141 males and 246 females) from 18 to 63 months of age, which were then divided into five age-groups. Through analysis of these radiographs, it was determined that the cut-off point for NA was 105°, AAR was 15°, and the acetabular angle of retrotorsion was positively correlated with Norberg angle and negatively correlated with hip score. The results of our study indicate that the acetabular angle of retrotorsion may represent a reliable morphometric assessment tool in evaluating acetabular cup conformation, and values of AAR may help to assess the FCI grade of canine hip dysplasia.

Gingival stippling in dogs: clinical and structural characteristics.

Diagnosis of periodontal disease, a frequent disorder in dogs, rests mainly upon the assessment of changes affecting the gingiva. Loss of gingival stippling, one of the early symptoms of periodontal disease in the human, could also indicate early periodontitis in the dog. The aim of this study was to determine the presence of gingival stippling in dogs, its location on alveolar processes, its association with age and inflammation, and its relation to the microstructure of the gingiva. The study concerns clinical, scanning electron and light microscopic examination of the gingiva of 48 dogs. Stippling, i.e. the granular appearance of the gingiva resembling irregularly distributed crater-like depressions of varying sizes, was present in adult but absent in young and senescent dogs. Stippling was most prominent at the level of the canine and the carnassial teeth. In contrast to the human gingiva, depressions and elevations of the stippled gingiva of the dog were not distributed uniformly. Presence of stippling indicates the presence of well developed mucosal layers and extensive interdigitation of epithelial rete pegs and papillary layer. Interaction of inelastic collagen fibres and a high hyaluronan content within papillary layer resulting in a high turgor of tissue due to the extensive water binding capacity of hyaluronic acid could also play a role in shaping of the gingival surface. The significance of gingival stippling in the diagnosis of periodontal disease in dogs is limited, as stippling occurs in healthy but also slightly inflamed attached gingiva of adult individuals.

A porcine model: surgical anatomy of the orbit for maxillofacial surgery

Due to its similarity to humans, the pig has proven to be a suitable biomodel for both research purposes and for training medical professionals, particularly in surgical specializations. For example, new implant materials have been tested on pig jaws and pigs have also been used in the development of new surgical techniques. For optimizing the effectiveness of such research or training, detailed data on the anatomy of their particular features are needed. At present, however, only limited information related to surgical and imaging anatomy of the facial and orbital areas of the pig and its comparison to human structures from the experimental surgery point of view is available in the literature. The aim of this study was to obtain such data and to compare the morphological structures of the porcine and human orbital regions and to lay down the foundation for practical use in experimental surgery. Ten pig heads were examined using computed tomography (CT) and magnetic resonance imaging (MRI) and, subsequently, a dissection of the orbit was carried out. Attention was focused on the structure of the orbit (floor, rim and nerves) frequently affected by pathological processes in humans (such as trauma, infection or tumours) and which consequently are frequently the subject of maxillofacial surgery. The porcine orbit is suitable for use in experimental medicine. However, if used in experiments, its anatomical peculiarities must be taken into consideration. Our study presents a foundation of basic knowledge for researchers who plan to use the pig as a biomedical model to investigate alternative treatments in the head region.

Diagnostic imaging modalities and surgical anatomy of the temporomandibular joint in rabbits

The temporomandibular joint (TMJ) is a condylar synovial joint that, together with the masticatory muscles, controls mandibular movement during mastication. The rabbit is often used as a model species for studying the mechanisms of TMJ diseases, and in regenerative research. However, there are significant differences between rabbit and human TMJs that should be taken into account before using this model for experimental research. Here, we use several analytical approaches (radiography, computed tomography and magnetic resonance imaging) to enable a detailed description and analysis of the rabbit TMJ morphology. Moreover, possible surgical approaches have been introduced with a focus on available access into the rabbit TMJ cavity, which relate our findings to clinical usage.

Cranial cruciate ligament structure in relation to the tibial plateau slope and intercondylar notch width in dogs

Cranial cruciate ligament (CCL) rupture is one of the most common orthopedic conditions in dogs. The pathogenesis of CCL rupture is not fully described and remains to be elucidated fully. Several hypotheses have been proposed to explain the etiology of these changes. The objective of this study was to investigate structural changes in the CCL in relation to the tibial plateau angle (TPA) and the intercondylar notch (ICN) width in dogs. Fifty-five skeletally mature dogs were included in this study. ICN width and TPA measurements were obtained from intact CCL stifles. Samples of the CCL, caudal cruciate ligament (CaCL), and femoral head ligament (FHL) were harvested and stained for routine histological and immunohistochemical analysis. Microscopic changes in the ligaments were observed and were found to correlate with the TPA and ICN width values. The degree of structural changes within the CCL was observed to correlate with an increasing TPA and a narrowing ICN width. Changes in the CCL are likely to be caused by excessive forces acting through the ligament in stifles with a high TPA. Chondroid metaplasia of the CCL is an adaptation to abnormal mechanics within the stifle joint caused by altered bone morphology.

A radiographic and anatomic study of caudolateral curvilinear osteophytes on the canine femoral neck

Caudolateral curvilinear osteophytes (CCOs) are considered to be an important finding for the early detection of canine hip dysplasia. The objective of this study was to determine the association between the radiographic and anatomic appearance of CCOs, and to determine whether CCOs are indicative of osteoarthritis. One hundred canine femurs were used to determine the topographical location of CCOs on the femoral neck, and the anatomic and radiographic presence of CCOs and their association with weight, sex, osteoarthritis, and femoral morphometry. Three angles were calculated to assess femoral conformation. The alpha angle and gamma angle described the angulation of the proximal femur and femoral neck, respectively. The beta angle described the angulation of the distal femur. Anatomic CCO was not detected in four femurs. No radiographic CCO was detected in 35 femurs and osteoarthritis changes were not found in 30 femurs. Statistically significant relationships were observed between anatomic CCO, alpha angle, and gamma angle. Statistically significant associations were observed between radiographic CCO, alpha angle, and gamma angle. The results of this study support an association between radiographic CCO on the femoral neck and osteoarthritis changes in the proximal femur. It can also be concluded that CCOs develop in association with femoral neck angulation, and may therefore be considered as an adaptation to the forces created by body weight that act through the femoral neck.

Facial pillars in dogs: an anatomical study.

This study describes the facial pillar system in dolichocephalic and brachycephalic breeds of dogs, and highlights its differences. Knowledge of facial pillar system anatomy is imperative to carry out successful fracture repair. The aim of our study was to describe the pillar system of the facial skeleton in dogs, and compare different shapes of dog skulls using native skulls, radiographs and computed tomography (CT). The heads of brachycephalic and dolichocephalic dogs were investigated following a maceration process using trans-illumination, radiography and CT. Ground sections were created from bones of the facial skeleton for investigation of osteon directions. This study has revealed that the facial skeleton of the dog has numerous sinuses supported by vertically and horizontally oriented bone pillars. These pillars can be divided into five principal regions in dolichocephalic skulls and six principal regions in brachycephalic skulls. Radiographic imaging of both the brachiocephalic and dolichocephalic skulls was not capable of discerning bone pillars. Computed tomography transverse and horizontal section images discerned all pillars observed in the illuminated skulls.