Introduction

• Cause: dental pain, primary dental pathology (fracture Teeth: fracture, ‘cap/deciduous’ expulsion, apical infection Teeth: apical infection, dysplasia [Link], loss of teeth, supernumerary , maleruption Teeth: maleruption, periodontal disease Teeth: periodontal disease/diastema, wear abnormalities Teeth: abnormal wear and large overgrowths), soft tissue trauma, foreign body Trachea: foreign body, oral neoplasia, lower and upper jaw fractures Mandible/maxilla: fracture, severe stomatitis Mouth: ulcers, temporomandibular Temporomandibular joint: fracture and temporohyoid joint Temporohyoid joint osteoarthropathy (THO) pathology.
• Signs: mild/moderate: slow eating, abnormal jaw movements/short swing phase, halitosis. Moderate/severe quidding (expulsion of partly masticated forage material), halitosis, weight loss, muscle atrophy (muscles of mastication), reduced feed intake.
• Diagnosis: observation of mastication, reduced feed intake, long fiber in feces, quidding on stable floor, halitosis, thorough dental examination, radiography.
• Treatment: treat specific pathology, diet adjustment - reduce long stem fiber.
• Prognosis: poor/guarded to good depending on specific pathology.

Pathogenesis

Etiology

• Depends on the specific pathology causing the dysmastication.

Predisposing factors

General

• Mastication of feed involves a 3-phase cyclical motion of the jaw to facilitate the grinding of feed materials. Any inhibition of this process through physical or painful stimuli can result in quidding.
• Young horses can experience acute deciduous cheek teeth loss and resultant quidding.
• Dental overcrowding due to retained, malerupted or additional cheek teeth Teeth: maleruption, can predispose to periodontal disease Teeth: periodontal disease, diastemata and quidding.
• Poor/infrequent routine dental treatment resulting in soft tissue ulceration.
• Wear abnormalities Teeth: abnormal wear of the cheek teeth leading to soft tissue damage.
• Oral pain from mouth lacerations, foreign bodies Trachea: foreign body, stomatitis Mouth: ulcers, dental fractures Teeth: fracture or oral neoplasia.
• Some types of mandibular Mandible/maxilla: fracture and incisor fractures Teeth: fracture can present in the chronic state with difficulty in chewing properly.
• Both temporomandibular Temporomandibular joint: fracture and temporohyoid joint Temporohyoid joint osteoarthropathy (THO) pathology can lead to dysmastication.

Specific

• Dental disease has a 10% occurrence in the adult horse population.
• The maxillary 09s are the most common cheek teeth with pathology.

Pathophysiology

• Sharp enamel overgrowths → Soft tissue ulceration → shortened swing phase of mastication → pain on mastication → dysmastication.
• Poor equilibration → inadequate grinding of feed → accumulation of feed → dysmastication.
• Dental pain (diastema/fracture/periodontal disease, etc) → discomfort during mastication → dysmastication.
• Displaced cheek teeth → mechanical ‘blockage’ → periodontal disease → dysmastication.

Timecourse

• May occur acutely or more typically are chronic and progressive over time.

Diagnosis

Treatment

Prevention

Outcomes