Dentistry

Before undertaking any discussion of equine dentistry, you must understand the nomenclature used to identify teeth. The chart below shows the numbers assigned to each tooth in the Traidan system.  

It is also useful to be able to approximate age of a horse by examining its teeth. The eruption table below as well as the following video explaining changes in incisor wear over time will help you learn to do this.  You will be expected to utilize these tables to determine the ages on every patient we see. This is something we will talk about more during the clinic. For now, we will focus on anatomy and basics of equine dentistry in the remainder of this article.

You must have a basic understanding of development, form, and function of the masticatory system in order to develop an understanding of equine dentistry. Horses are meant to spend a large portion of their time eating low quality feed. The long periods of time spent grinding food causes a great deal of wear on their teeth. For this reason the horse’s teeth are very long, with a great deal of tooth below the gum line early in life.  The tooth erupts at a constant rate until there is no tooth left to erupt. On average horses lose about 2-3 mm of tooth annually to the grinding forces that occur when they chew.  This is referred to as attrition. Factors that affect attrition include:

1. The complex chewing cycle – varies from horse to horse.
2. Feed type and amount of time spent chewing.
3. Confirmation of the dental arcades.

 

Anatomy of the tooth

The tooth consists of the following layers:

• Cementum is a living tissue and is the most adaptable of the tooth layers. It is found in the infundibulum and covering the entire crown.  It is worn from the occlusal surface after the tooth erupts. It is deposited to the crown below the gum line for the life of the tooth.  It adds to the size and strength of the tooth and protects the enamel.  The deciduous incisors appear whiter due to the relative lack of cementum compared to the permanent incisors.
• Enamel is the hardest component of the tooth but it is brittle. It is 98% mineral, essentially dead and has no ability to repair itself.  
• Dentin consists of 70% minerals an makes up the majority of the tooth.  It is produced by odontoblasts and pulp.  The process occurs as the tooth erupts, preventing the pulp from becoming exposed.  There is primary and secondary dentin.  Secondary dentin can be regular or irregular.
• Pulp maintains a relatively large blood supply. It lays down secondary dentin to close the pulp cavity as the tooth erupts.  This narrows the pulp cavity and strengthens the tooth as it ages. The blood supply and ability to lay down secondary dentin allow younger horses to fight pulp infections and repair themselves.  Horses younger than 7 or  8 have more brittle teeth due to the lower ratio of secondary dentin.  Older horses, with a higher ratio of dentin, have much stronger teeth.  Root formation is completed by the age of 2, however separate pulp channels may not be completely formed in the mandibular cheek teeth until the age of 5-6 years.
• In addition to the cementum, enamel, pulp, and dentin, incisors and cheek teeth (premolars and molars) have a structures called infundibulum.  This is an infolding of the peripheral enamel in the center of the tooth, which is filled by varying amounts of cementum.  The infundibulum of the incisors is colloquially called the “cup.” The cheek teeth each have 2 infundibula.

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Common Malocclusions    

All of the following malocclusions if untreated will eventually prevent the patient from closing their mouth, leaving them unable to chew.  These malocclusions normally occur bilaterally.

Performing Dental Work

Performing a complete oral exam requires a full mouth speculum. Power equipment is required to address many dental abnormalities, however, routine dental work can often be performed with hand floats and without a speculum. You must allow your patient to rest their jaw periodically when wearing a mouth speculum. Speculums should be closed after a maximum of 15 minutes.

Equipment needed:

• Bucket of water with small amount of chlorhexidine solution
• Dose syringe to rinse mouth
• Good head lamp
• Full mouth or wedge speculum 
• Floats – hand or power
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• Note: never set the equipment down on the ground.  Always place floats and syringe back into the bucket, on a table, or in the float case.
  

As an equine practitioner, performing an oral exam will be a routine part of your job.  You may as well develop a system for this now.  A thorough exam involves more than looking into the oral cavity. Not all patients will allow you to touch their mouths without sedation, but as you develop some skill, you should be able to examine most patients without it.

Before looking into the patient’s mouth:

• Look for/ask about signs of quidding (dropped feed).
• Check manure for feed that has not been well chewed.
• Smell the patient’s breath.
• Check both nostrils for even air flow.

• problems chewing
• problems swallowing
• dropping feed

Look at/feel the patients head. Look for asymmetry in the jaw, the sinuses and the sides of the face. Palpate the temporomandibular joint (TMJ). Feel the face over the upper molars and premolars for: