Feline Dentistry. Jan Bellows

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СКАЧАТЬ Attached Gingiva

      The attached gingiva is located apical to the marginal gingiva and is normally tightly bound to the periosteum of alveolar bone. Attached gingiva is keratinized to withstand the stress of mastication. The width of the attached gingiva varies in different areas of the mouth. It is widest at the maxillary canines.

      The firmly attached gingiva is contiguous with loose alveolar mucosa at the mucogingival junction, also referred as the mucogingival line. The mucogingival junction remains stationary throughout life, although the gingiva around it may change in height due to attachment loss or hyperplasia.

      1.9.4 Gingival Sulcus

The gingival sulcus is a shallow space between the marginal gingiva and the tooth. The sulcus depth is generally under 1 mm but varies depending on the specific tooth and the size of the cat. In cases of periodontal disease, the abnormal sulcus is termed a pocket, which extends further apically due to destruction of the periodontium (Figure 1.8).

1.10 Periodontal Ligament

      The periodontal ligament is a dense, fibrous connective tissue that attaches the tooth root to the bony alveolus. The periodontal ligament also acts as a suspensory cushion against occlusal forces and as an epithelial attachment to keep debris from entering deeper tissues.

      The blood supply to the periodontal ligament originates from the alveolar artery. Arterioles enter the ligament near the apex of the root and from lateral aspects of the alveolar socket and branch into capillaries within the ligament along the long axis of the tooth. Collagen fibers also run through these spaces. The blood vessels are closer to the bone than to the cementum. Venules drain the apex through apertures in the bony wall of the alveolus and into the marrow spaces. Cells commonly found in the periodontal ligament are fibroblasts, osteoblasts, cementoblasts, osteoclasts, cementoclasts, rest cells of Malassez, and undifferentiated mesenchymal cells (progenitor cells).

      Nerve bundles enter the periodontal ligament through numerous foramina in the alveolar bone. They branch and end in small rounded bodies near the cementum. The nerves carry pain, touch, and pressure sensations and form an important part of the feedback mechanism of the masticatory apparatus.

The periodontal ligament has great adaptive capacity. It responds to chronic functional overload by widening to relieve the load on the tooth. Vascular communications between the pulp and periodontium form pathways for transmission of inflammation and microorganisms between the tissues (Figure 1.9a,b).

1.11 Cementum

      Cementum covers the healthy root and provides attachment for the periodontal ligament. Cementum is produced continuously by cementoblasts, slightly increasing in thickness throughout life. Acellular cementum is present at the coronal one‐third of the root, while cellular cementum appears at the root apex. Cementum is capable of formation, destruction, and repair, and is involved in both resorptive and reparative processes. It is nourished from vessels within the periodontal ligament. Cementocytes in cellular cementum communicate with underlying dentin with each other via canaliculi.

1.12 Alveolar Bone

      Alveolar processes house the alveoli, which support the teeth by providing attachment for the fibers of the periodontal ligament. An alveolus can be divided into two parts:

      1 Alveolar bone proper, which is a thin layer of bone surrounding the root that allows attachment to the periodontal ligament.

      2 Supporting alveolar bone, which consists of compact, cortical, or cancellous bone on the vestibular and oral aspects of the alveolar process. The alveolar bone proper is also referred to as the cribriform plate. It covers the alveolar socket and is identified on radiographs as lamina dura (Figure 1.10).

Figure 1.9 (a) Sagittal section revealing the periodontal ligament location (arrow). (b) Intraoral radiograph of the left maxillary canine demonstrating the periodontal ligament space.

Figure 1.10 Lamina dura (arrows pointing to the white line surrounding the tooth root).

      The alveolar bone and cortical plates are thickest in the mandible. The shape and structure of the trabeculae of spongy bone reflect the stress‐bearing requirements of a particular site. In some areas, alveolar bone is thin with no spongy bone.

The alveolar bone height is in equilibrium between bone formation and bone resorption. When bone resorption exceeds formation, the alveolar bone height is reduced (Figure 1.11a,b).

1.13 Bones and Joints

      1.13.1 Cranium

The skull can be divided into the fused bones of the calvaria, the upper jaw (maxillae), and lower jaw (mandibles). The dorsal aspect of the skull (cranium) is composed of the paired frontal and parietal bones. The occipital region of the cranium is the caudal aspect of the skull formed by the occipital bone. The temporal region is composed of the lateral walls of the cranium formed by the temporal bones. The rostral wall of the cranium is formed by the ethmoid bone (Figure 1.12a,b).

Figure 1.11 (a) Alveolus encasing a fractured maxillary canine tooth. (b) Decreased alveolar margin height (arrows) secondary to periodontal disease.

Figure 1.12 (a) Left lateral aspect of the skull with the zygomatic arch removed; 1. Parietal bone; 2. Squamous temporal bone; 3. Sphenopalatine foramen; 4. Maxilla; 5. Incisive bone; 6. Frontal bone; 7. Lacrimal bone; 8. Optic canal. (b) Medial aspect of a sagittal section of the left aspect of the skull: 1. Incisive bone; 2. Maxilloturbinates; 3. Nasal bone; 4. Nasal septum; 5. Palatine bone; 6. Pterygoid bone; 7. Ethmoid bone. (c) Dorsal aspect of the skull: 1. Incisive bone; 2. Nasal bone; 3. Maxilla; СКАЧАТЬ