Anatomy and physiology of the periodontal tissue is extremely important to the veterinary dental clinician. Periodontal disease
is ubiquitous in our patients and represents the majority of cases we see in general practice. The periodontal ligament is
a collection of miniscule collagen fibers that attach the cementum to the alveolar bone. Radiographically, the space between
the cementum and bone coincides with the region where these fibers reside. A change in the width of this periodontal ligament
space around the tooth indicates pathology (Photo 7).
Photo 7: Bone loss from periodontal disease.
The bone that surrounds the periodontal ligament space and the tooth is known as the alveolar process. Collectively, it is
the cribriform plate (bone lining the tooth socket) known radiographically as the lamina dura, the alveolar margin and the
trabecular bone. Radiographic density changes in the various portions of the alveolar process indicate pathology. Periodontal
disease, neoplasia, cysts and fractures are examples that may result in changes in alveolar process radiographic density.
Photo 8: Start of periodontal disease.
Photo 9: Gross anatomy.
The alveolar process is covered by periosteum. A region of attached gingiva is tightly adhered to the periosteum and is separated
from vestibular mucosa (unattached gingiva) by the mucogingival line or junction. The edge or free margin of the gingiva is
termed marginal gingiva (Photo 8). Mobilization of tissue for closure at extraction sites often requires periosteal elevation
of the attached gingiva beyond the mucogingival line (Photo 9). The tissue that attaches the gingiva to the tooth is called
the junctional epithelium. It rests at the base of the gingival sulcus. A periodontal probe properly placed within the sulcus
will come to rest on the junctional epithelium (Photo 10).
Photo 10: Junctional epithelium.
Photo 11: Terms applied to the roots.
Periodontal disease compromises the junctional epithelium and increased probing depths and bleeding upon probing are encountered.
Radiographic or gross pathology is generally described by the location of the pathology in relation to various structures
within the oral cavity. Directional terms commonly used to describe pathology in relation to the dental arcades are defined
as follows (Photos 11, 12 and 13) :
- Mesial = toward the midline of the dental arch in either mandible or the maxilla,
- Distal = away from the midline of the dental arch,
- Vestibular = (formerly buccal) toward the cheek,
- Lingual = toward the tongue,
- Palatal = toward the palate,
- Labial = toward the lip. This pertains to the canine and incisor region.
- Facial = general term used to indicate either vestibular or labial direction.