Merck Manual

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Professional Version

Overview of Diseases of the Mouth in Small Animals


Alexander M. Reiter

, Dipl. Tzt., DEVDC, DAVDC, Department of Clinical Sciences & Advanced Medicine, School of Veterinary Medicine, University of Pennsylvania

Reviewed/Revised May 2014 | Modified Oct 2022

The primary function of the mouth is to introduce food into the digestive tract. Additional functions include communication and social interaction, grooming, protection, heat regulation (particularly in dogs), and grasping objects. The latter is very important for performance animals (eg, retrievers, military and police dogs). Similar to other areas of the alimentary tract, the mouth in the normal, healthy state supports a large and diverse population of bacteria that lives primarily in biofilm communities. Unlike other areas of the body, the mouth also contains nonvital surfaces (enamel of teeth) that have neither local immune system defenses nor the ability to regenerate through cellular replacement. The oral mucosal tissues have an excellent vascular supply, and the tightly adherent gingiva protects the underlying alveolar bone from trauma, thermal injury, and bacterial invasion.

Food prehension requires a complex interaction of the muscles of mastication, the teeth, the tongue, and the pharyngeal muscles. When any of these become compromised through disease or trauma, malnutrition and dehydration may result.

A complete oral examination should be included in every physical examination, because oral diseases are most effectively treated when diagnosed early. Unfortunately, many problems remain hidden in the mouth until they have progressed to an advanced stage.

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