Periodontal disease in the horse
These animals may present with mouth pain, tooth loss and dysmasti-cation. Exfoliated teeth may sit atop a healed alveolus held in position by mastication forces and gravity. Chewing may be painful and inefficient, and some teeth may be so loose they literally can be removed by hand.
Periodontal disease is "a general term referring to the altered state of the perio-dontium," including both the resting and active states of the disease process, according to David Klugh, DVM, fellow, Academy of Veterinary Dentistry/Equine in Newberg, Ore. Periodontitis, he says, refers to "the active state of the disease with inflammation of the periodontium, while gingivitis refers to inflammation of the gingiva only."Pathophysiology
The initial clinical sign of the pathological process is gingivitis, with tissue becoming edematous and reddened. The sulcular epithelium is inflamed, and gingival collagen support is lost. Further inflammation leads to involvement of deeper periodontal tissues.
Periodontal pocket formation occurs as the junctional epithelium proliferates apically in an attempt to maintain tooth contact, while detachment occurs at the coronal margin. Bacterial invasion results in inflammation and thickening of the sulcular epithelium, which eventually becomes necrotic. If uninterrupted, the cycle continues until the tooth is exfoliated.
Equine dental anatomy is unique in that the cementum of the clinical and reserve crown is involved in perio-dontal disease. Supragingival and subgingival cementum can become necrotic.
Unlike animals with brachydont teeth, equine hypsodont teeth rarely build up enough plaque and calculus to cause attachment loss. "In most cases of equine periodontal disease, no calculus or plaque is present," says Klugh. "The triggering event in horses is stasis of feed material and its resulting decomposition."
Feed stasis and putrefaction result from several factors, including alteration of the normal range of motion in mastication, direct gingival abrasion and orthodontic tooth movement by malocclusion.
The pathological endpoint of perio-dontal disease is tooth exfoliation. Affected teeth eventually become loose with excessive attachment loss and succumb to mastication forces. Tooth mobility can be measured, ranging from no movement to movement of greater than 3 mm for severe disease.
Stage 1 of periodontal disease is characterized by gingivitis, the gingiva being swollen and reddened. The gingival sulcus is of normal depth, but might bleed when probed. No attachment loss is present. The cementum may be normal or decayed.
Feed material is present in the depressions of the periodontal topography of Stage 2 disease, just as in Stage 1. Further disease progression presents with pocketed food debris.
During early periodontal disease there is less than 25 percent attachment loss and/or crestal bone loss around teeth. Gingival sulcus depth is > 5 mm. The gingiva has receded and is ulcerated. Supragingival cementum is decayed. Sulcular epithelium varies from mild to severe inflammation and necrosis. Subgingival cementum is decayed. Tooth mobility is slight.
In Stage 3, pockets appear similar to Stage 2, and the condition of the gingival, cementum and sulcular epithelium are similar. But during this moderate stage there is 25 percent to 50 percent attachment loss or a bone loss of up to 50 percent around teeth roots.
At Stage 4, prior to tooth exfoliation, the disease is widespread and severe, including gingival recession, ulceration and edema, with excessive bleeding. Cementum is decayed supra- and subgingivally. Sulcular epithelium is necrotic, with purulent discharge. Tooth mobility may be severe. Radiographic changes will show loss of alveolar bone, blunting of apices and lytic changes in the subgingival crown and roots. This advanced periodontal disease is exhibited by greater than 50 percent attachment loss or bone loss greater than 50 percent.