Equine Odontoclastic Tooth Resorption and Hypercementosis
Chronic incisor periodontal disease of the horse was first known as hypercementosis. At the 2006 AAEP meeting, 4 cases of the disease in older
horses were described by Dr Robert Gregory from Washington. In all 4 cases, the cementum was lytic in some areas and hyperplastic in others,
as a response to inflammation, and the disease seemed to progress from the corner incisors towards the middle.
The external surface of the equine tooth is covered by cementum overlying enamel. The cementum also extends down into the infolded
infundibulum (cup) in the center of the tooth. Some live cells of the tooth called odontoclasts cause lysis, literally eating away,
of cementum both inside the infundibulum and in the cementum and tissues surrounding the tooth. Other cells respond to inflammatory
insult by creating extra cementum (hypercementosis) that eventually extrudes the tooth and root from the underlying alveolar bone.
The more severely affected teeth develop infection that may break through into the pulp leading to death of the pulp tissue.
Initial signs include gingival reaction, petechiae above the gingival attachment, or fistulae appearing above the gingival margin. X-rays are diagnostic.
Research to determine the cause of the inflammation is ongoing. Carsten Staszyk at the University of Veterinary Medicine in Hannover, Germany,
believes that as horses age the angulation of the incisor teeth puts additional stress on the periodontal ligament leading to inflammation that
triggers this syndrome that he now labels Equine Odontoclastic Tooth Resorption and Hypercementosis (EOTRH). Additionally, many different bacterial
organisms have been cultured from extracted teeth and surrounding tissue, but there is still not a clear etiology. Dr. Ed Earley, Fellow of the Academy
of Veterinary Dentistry, from Williamsport, PA, continues to gather tissues and teeth for examination and culture.
Historically, treatments have included antibiotics, pulsed antibiotics (once a month, for 5-10 days) steroids injected around the teeth when
the lesions are early and only hyperplastic, and extraction of all loosened, or badly infected teeth. Most veterinarians consider the disease
very painful when it reaches the lytic stage, especially if the teeth are loosened and mobile. (Affected horses may refuse the bit, become
head shy, or turn away from apples, carrots or treats). Splinting of remaining teeth with acrylic materials may be done to reduce mobility
and subsequent pain.
Full extraction has made some horses more comfortable and a gingival flap procedure to suture the gum tissue over the
extraction site may speed healing. We are using constant rate infusion drips of butorphanol/detomidine and infraorbital or mental
nerve blocks as well as local infusion of lidocaine/marcaine prior to extraction. The use of calcium sulfate (plaster of paris)
with crushed doxycycline as a scaffold in the alveoli after curettage and flush has been successful in speeding bony filling of the
alveolus. Twice daily flushing with diluted chlorhexidine solution and oral antibiotics and bute are used for 7 days, beginning 24
hours prior to extractions.