Oral Examination of the Horse
- Feb 1, 2007
Horse owners must understand how such an exam is performed and when to have one done. A substandard oral examination might overlook major abnormalities, leading to health and performance problems. Would you be able to tell if your dental professional is performing a skilled oral exam? You should!
This article is intended to give the reader an understanding of basic dental anatomy and function, when to schedule an oral exam, the tools necessary to perform the oral exam, and the execution of a sound oral examination. With this knowledge horse owners can help ensure their dental care providers are accurately assessing their horses' oral health and making proper treatment recommendations.
Anatomy and Function
Knowledge of oral anatomy and the function of these structures is required to understand the oral exam. Normal adult horses have 36-44 teeth. The range in number is due to the presence or absence of canines (04s) and wolf teeth (first premolars/05s). Adult horses can have from zero to four canines and from zero to four wolf teeth. Mares tend not to have any canines, or they have very small ones, unlike geldings and stallions that usually have well-developed canines.
There are 12 incisors (six upper and six lower) and 24 cheek teeth (12 upper and 12 lower).
Teeth are separated into four quadrants for numbering purposes. Adult upper right teeth are called 100 series, upper left are 200 series, lower left are 300 series, and lower right are 400 series. Similarly, deciduous teeth (baby teeth) are numbered from 500 to 800 series following the same pattern.
As the horse ages, the normal shape and alignment of the teeth change. The angle of eruption into the mouth, type of food ingested, and forces of mastication (chewing) all play a role in this gradual shift.
The primary regions making up a tooth are the crown and the root. The crown is that portion of the tooth containing enamel. The root has no enamel. The crown is divided into sections including:
Clinical crown Exposed crown from the occlusal (grinding) surface to the gum line;
Gingival crown Crown that is below the gum, but not in the tooth socket;
Reserve crown Crown that is remaining in the tooth socket. The root lies within the socket until all the crown has worn completely away or there is a disease process exposing it.
The periodontal ligament, shape of the tooth, and corresponding shape of the alveolus (tooth socket) all help to maintain the tooth securely in place. The gingiva (gum) forms a seal with the crown or the root, depending on the stage of eruption into the oral cavity. This "seal" helps to prevent access of bacteria and other substances (such as food) to the periodontal space (area around the tooth).
Function of the teeth varies from shearing or cutting of forages by the incisors (front teeth), to defensive measures within the herd or against a predator by the canines, and finally to mastication (grinding) of food for proper presentation to the digestive tract by the cheek teeth. In a natural environment all of these are vital to the horse's survival.
The chewing cycle is well-documented in the horse and is comprised of multiple phases; the opening stroke, closing stroke, power stroke, and recovery stroke. We generally think of chewing and swallowing as simple events, but in reality they are extremely complex. Salivary glands, ducts, the tongue, nerves, muscles, tooth shape, lips, and cheeks all play an important role in chewing and preparing the ingesta for swallowing.
When your horse eats, shearing (side- to-side) forces tend to be greater when eating hay or grasses, and compression (crushing) forces tend to be greater when fed grains. A loss of any of the components involved can have serious consequences. Take the time to watch your horse eat. Discover problems early and avoid potentially serious repercussions.
When to Schedule an Exam
Horses that appear normal in every way should be examined at six- to 12-month intervals, starting at their newborn exam. Congenital (present at birth) problems should be detected as early as possible so that appropriate treatment and monitoring will have the greatest positive effect. Young horses' (less than six years) dentition and surrounding tissues are going through dramatic changes, so it is important to evaluate them frequently. Six-month intervals are appropriate if findings are normal at each successive exam. Normal adult horses (greater than seven years) might only need annual exams provided no pathologies (abnormalities) are found. Any horse showing clinical signs that might be related to dental issues should be examined as soon as possible.
The list of possible clinical signs is extensive and varies based on patient and management factors such as age and how horses are stabled. If your horse is thin even with good management, tosses his head, grabs the bit, eats slow, drops feed or hay, quids (wads up forage and spits it back out), has a belligerent or depressed attitude, has had colic or any unexplained illness (especially if it is recurring), and/or has a fetid odor to his breath, then he needs a comprehensive oral exam.
Dental issues might be the cause of problems at sites distant from the mouth. Periodontal disease (disease of the structures surrounding the teeth), for instance, can cause bacterial infections at locations such as the heart valves. The caregiver might notice exercise intolerance (tiring quickly), depression, and fever. If the underlying dental disease is not found and treated, the heart valve infection or other conditions are likely to recur, even if these conditions are treated.
Horse owners need to realize there are enormous benefits in having a dental care provider who is a veterinarian as opposed to a lay dental provider. The veterinarian has extensive training necessary to properly evaluate patients for concurrent disease processes. Some of these conditions include sinus infections, Cushing's disease, diabetes-like syndrome, kidney disease, liver disease, and heart disease. There is much more to dentistry than just teeth!
A practitioner needs the following instruments to perform a quality oral exam: head lamp, full mouth speculum, large-dose syringe, dental probe, dental explorer, lingual and buccal retractors, intraoral mirror, and dental halter or head stand.
Additional items that might be necessary to fully evaluate the oral cavity and related structures include intraoral and extraoral radiographic equipment, sinuscopy equipment, and intraoral cameras.
Remember, just having a lot of tools does not mean that the examiner knows how to use them. Ask lots of questions regarding the equipment and its use (get complete answers, including which instruments are being used and why).
If you don't get satisfactory answers, I recommend you look for another clinician. Keep in mind, not all clinicians will have access to some of the more expensive high-tech equipment such as digital radiography. They should know when a referral is appropriate and where the equine dental referral facilities are in your area, so ask them.
Being a large referral hospital does not qualify a facility as a dental referral facility. Make sure the facility has a competent dental surgeon.
Execution of the Examination
The execution of a proper oral exam starts with a complete history. Important components of a horse's history include age, breed, sex, the horse's use, housing, nutrition, if it has to compete for food or if it is fed as an individual, date of deworming, if the horse cribs or wind sucks, his appetite, past dental problems, date of last dental, frequency of dental exams, and who performed the dental exams.
An overall physical exam of the entire horse should be performed. What is the horse's body condition? Is his chewing cycle correct?
Look for evidence of pain. Does he chew hay correctly, but not grain, or vice versa? Is he quidding hay or grass? Does he refuse treats? Is his head level when eating? Is there excessive drooling before or after eating? Is halitosis present? Does anything about the horse's appearance indicate a condition that might be caused by abnormal dentition?
Facial symmetry should be evaluated both externally and intraorally. Pathology can be subtle, such as a deformed maxilla (upper jaw) or mandible (lower jaw).
Subtle abnormalities must be considered to ensure proper treatment. When evaluating facial symmetry, the patient's head should be in its natural position.
The examiner should evaluate external symmetry without sedation so that he/she can accurately assess muscle mass and head carriage. The eyes should be level and set in a natural position, not protruding from or retracting into the eye sockets. There should be no abnormal swellings or indentations on the head.
Facial swellings and ophthalmic asymmetries might indicate tooth root problems, sinus pathologies, or cancers. Unilateral nasal discharge (out of one nostril) can also indicate tooth root problems within a particular sinus. Other possibilities include sinus cysts and bacterial or fungal sinus infections. Sinuscopy (entrance into the sinus and visualization of the contents with a fiberoptic scope) and/or X rays might be indicated. Conditions such as droopy eyelids, chronic tearing, and nasal and lip deviations might also indicate tooth pathologies due to close proximity of ducts and nerves to the teeth.
Based on the history and external exam, the practitioner might need to gather more information from additional tests--such as complete blood counts and chemistry profiles--before proceeding to the internal oral exam. Provided the patient is healthy, the practitioner performs an intraoral exam on the horse while it is under standing anesthesia. The examination consists of a thorough review of all structures within the mouth, including symmetry and function.
Incisor symmetry, lateral excursion (see below), drawer (see below), evidence of trauma, caries (cavities), and periodontal disease are all evaluated and recorded. Lateral excursion is the distance the lower jaw moves to the side before the incisors begin to separate due to molar contact. It is measured to the left and the right. This measurement helps estimate the amount of molar occlusion (contact). It is also used to calculate the molar surface angles.
Drawer is the distance the lower jaw moves from the front to the back in relation to the upper jaw. It is measured as the distance the front or labial side of the lower central incisors moves in comparison to the same point on the upper incisors, as the head is raised and lowered. The lower jaw should move back as the head is extended or raised. These measurements help to evaluate functional efficiency of the mouth.
After positioning a full mouth speculum, the mouth is rinsed and all surfaces of the canine teeth, tongue, cheeks, and palate are examined for abnormalities. The examiner notes hyperemia (an increase of blood flow to the tissues in an area, causing reddening), ulcers, lacerations, scarring, swelling, and the presence of any masses. Chronic contact with sharp enamel points can result in ulcers and scarring of the soft tissues involved. Masses might include cancers (such as melanomas and squamous cell carcinomas), fungal granulomas, and reactions to foreign bodies.
Periodontal disease might be obvious on gross physical exam of the oral cavity, or it can be more elusive. It might be found relative to any tooth in the mouth.
The examiner will notice evidence of one or more of the following: halitosis, bleeding at the gingival margins of the teeth, pocketing and necrosis of tissues around the teeth, loose teeth, and teeth that might be compressed into the dental alveoli. The examiner should measure pocket depth with periodontal probes. To confirm and grade severity of abscesses and widening of periodontal spaces (evidence of tooth attachment loss), most cases will require intraoral and extraoral radiology.
Periodontal disease is progressive and can be very painful. The chewing cycle might be affected as the horse attempts to change how it chews to decrease pain.
The practitioner must keep in mind the age of the horse and correlate this with tooth structures. Retained deciduous teeth can result in damage to permanent teeth and/or the surrounding tissues. Failure to remove these teeth or their fragments can result in pain or problems with permanent dentition. Wolf teeth might be absent naturally, present and erupted in one or more cheek teeth arcades (rows of teeth), or blind (incompletely erupted) in one or more arcades. They also might be malpositioned within the arcades. I have seen many instances where the abnormalities have been missed for years. Examiners must look carefully for these problems.
Under ideal circumstances the opposing teeth would wear out simultaneously, because the composition of opposing teeth would be equal. On successive exams the examiner would see the crown disappear due to attrition (wearing away with friction), and eventually the root would do the same. With quality dental care and good genetics, some horses reach this point. These horses can do well if their diets require little or no mastication; watered- down complete nutrition pellets are an example of a feed that would work for such a horse.
The physical structure of each cheek tooth must be examined in detail. Head lamps, dental explorers, probes, and mirrors are used to assess each tooth. The examiner searches for extra, missing, malpositioned, and traumatized teeth. Structural malformations include excessive dentin, cementum, or enamel (all considered hyperplasias). The lack of these structures (hypoplasias) are also evaluated.
If left undiagnosed, these conditions can affect the overall health and well-being of the horse. Regular exams and proper diagnoses can allow for early treatment protocols. This will improve the patient's quality of life and decrease treatment expense.
All horse owners need to know what constitutes a thorough oral examination so that they can recognize whether their dentist has done an efficient job. A skilled exam helps ensure that the equilibration to follow will resolve as many problems as possible. Horses can and will suffer in silence. All horses need dental care on a regular basis, regardless of whether or not they are exhibiting problems. With the many recent advances in equine dentistry, it is now possible to correct conditions that previously were left unattended. Armed with the knowledge presented here, horse owners can now be more confident that their horses are receiving the best possible dental care, resulting in better health, greater well-being, and optimal performance.
About the Author
Jon M. Gieche, DVM, owns Kettle Moraine Equine Hospital and Regional Equine Dental Center in Whitewater, Wis. Gieche is an AAEP member and serves on the AAEP's Committee on Equine Dentistry. He has been a speaker at the AAEP's annual veterinary dental wet labs and the Wisconsin Veterinary Medical Association's Annual Convention. Gieche is a member and two-term past president of the Wisconsin Equine Practitioners Association. For more information on Kettle Moraine Equine Hospital and Regional Equine Dental Center visit www.kmeh.com.
POLL: Enriching Your Horse's Environment