How to Assess the Periodontal and Endodontic Structures of Equine Teeth

1. Introduction

The health of equine periodontal and endodontic structures is critical to evaluating the overall health of an equine tooth. The equine periodontium, comprised of the gingiva, alveolar bone, periodontal ligament, and cementum, is directly responsible for stabilizing and holding the tooth in place within the oral cavity. Periodontal disease is the inflammation and infection of the periodontium, and if left untreated, it can lead to extensive attachment loss of the tooth from surrounding hard and soft tissue structures. Mobility may even result if the attachment loss is greater than 25% to 50% of the remaining reserve crown and root. The equine endodontic system or endodontium is located within the root canals, common pulp chamber(s), and pulp horns of the teeth, and it is comprised of blood vessels, nerves, lymphatic structures, and connective tissue commonly referred to as dental pulp. The endodontic system is responsible for nourishing the majority of the cellular components that make up the main structure of the tooth via the dentin-pulp complex. Odontoblasts make up a significant portion of the dentin-pulp complex, and odontoblasts are responsible for creating and sustaining dentin. The continual generation of secondary and tertiary dentin by the odontoblasts is what protects the endodontium from exposure during the constant slow loss of dental structure during normal mastication. 

Endodontic disease is inflammation and/or infection of the endodontium that may or may not result in pulpal injury, necrosis, and/or death. If the endodontium of a tooth is severely injured, the pulp will become necrotic and die. Without the pulp, the tooth is no longer able to develop or respond to normal attrition and abrasion (wear of the tooth from occlusal contact and feed material). If the initial injury did not already result in exposure of a pulp horn to the oral environment, then over time the normal continual wear of equine teeth will eventually expose the pulp due to non-responsive odontoblasts. Once nonvital pulp horns are exposed to the oral cavity, feed packing and bacterial invasion into the endodontic space commences. The nonvital tooth harbors infection that slowly percolates into the surrounding bone via the apical portion of the roots and channels within dead dental structures. It is important to note that endodontically nonvital teeth can still have a vital, intact periodontium due to the fact the periodontium receives nourishment from surrounding vasculature.

Disease of equine periodontal and endodontic tissue is well-documented in the literature.¹ The most commonly identified abnormality of incisors particularly in young horses (< 2 years of age) was transverse fracture with or without fracture of the surrounding bone and/or pulp exposure.² The incisor pulp horn is particularly vulnerable to exposure because of its position on the labial aspect of the tooth. Incisor primary periodontal disease and periodontal disease in relation to equine odontoclastic tooth resorption and hypercementosis is well-recognized.³ Dental fracture, pulp exposure, apical infection, primary periodontal disease, and diastemata of cheek teeth have extensive reporting in the literature.⁴ Prevalence of equine periodontal disease has been reported to be as high as 75% in some regions,⁵ and 49.9% of horses in the general population have some level of disease.⁶ Fractures commonly occur in cheek teeth especially on the maxillary teeth.⁷ Endodontic disease can result from these fractures. Some additional causes of endodontic disease are excessive/rapid dental wear, severe infundibular carious lesions, severe periodontal disease, anachoresis, dental malformation, iatrogenic damage, regional fracture/past trauma, and unknown. In order to fully assess the health of the periodontium and the endodontium of equine teeth, a thorough physical and oral examination needs to be performed. If there is any suspicion that these disease processes are present, a radiographic evaluation should be performed of the suspect region.

2. Materials and Methods

Necessary Instrumentation

• Sedation
• Medical grade BRIGHT headlight (a camping style headlight will not provide adequate light to see subtle lesions)
• Full mouth speculum
• Oral irrigation preferably under pressure
• Periodontal probe—thin (1 mm width) with mm demarcations up to 2 to 3 cm in length (the tip of periodontal probes should be BLUNT not pointed to avoid gingival injury)
• Explorer number 23 on equine handle
• Dental mirror with defogger (alcohol, warm water, light layer soap, commercial defogger, etc.)
• Dental scalers, curettes, and picks
• Cheek retractor
• Rigid oral endoscope (if available)
• Extraoral radiographic equipment
• Intraoral radiographic equipment (if available)

Pre-Oral Examination

It is important to gather a thorough patient clinical history and perform a complete physical examination. Owners can provide ample information regarding onset of clinical signs, feeding behavior, progression of condition, systemic health, performance, and response to past therapies, all of which could be significant in the determination of pathology presence, diagnostics, treatment planning, and prioritization of the dental condition relative to the overall status of the patient. Observation of mastication pre-sedation can also enhance the clinician’s ability to assess oral function and watch for signs of discomfort.

Sedated Oral Examination

A previous session in this series reported on how to perform a complete oral examination in the horse. This portion will focus solely on how to assess the endodontic and periodontal health of a tooth. Evaluation of the endodontic and periodontal health of a tooth should ALWAYS be part of a complete oral examination.

The maxillofacial region of the horse should be examined as part of a complete oral exam. If endodontic or periodontal health is compromised, extraoral examination findings might include enlarged regional lymph nodes, asymmetry of the muscles of mastication, bony or soft tissue swellings, regions of buccal feed packing, fistula formation, regions of sensitivity, and nasal discharge. Once the extraoral portion of the examination is complete, the incisor and bar region of the oral cavity is examined followed by speculum placement and examination of the oral cavity proper and cheek teeth. The following lists specific steps to performing a thorough examination of the periodontal and endodontic structures within the oral cavity. This comprises only a portion of a complete oral examination.

1. Water irrigation and dental scalers, curettes, and picks are used to completely remove debris, packed feed, and calculus from the oral environment and dental structures.
2. When inspecting intraoral periodontal and endodontic structures, ALL aspects of the tooth and surrounding structures must be examined. This includes the labial/buccal, palatal/lingual, mesial, distal, and occlusal aspects. Inspection of these structures in the rostral portion of the mouth can be performed by proper hand placement and digital manipulation of tissues. An incisor speculum is only necessary when an area of interest needs prolonged and careful inspection. A full-mouth speculum is necessary for examination of the premolar and molar teeth. The use of a dental mirror is absolutely necessary to be able to adequately examine all soft and hard tissue structures especially in the caudal portion of the oral cavity. Oral endoscopy, if available, provides even better visualization of all intraoral structures, and its use is becoming more common among practitioners with dental expertise. [...]