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WORDS BY Dr Shannon Lee
BVSc, MANZCVSc Eq Dent, DICEVO
www.advancedequinedentistry.com.au

 

Horses, and especially young ones, are curious by nature.   They can be playful and, unfortunately, that play can quickly turn into an accident which results in injury.   Injuries to the head are extremely common and I come across many, many people whose own horses have suffered previous head trauma and yet, they (the owners) have no inkling or idea there was ever an injury.   This may seem strange, but it is largely because a lot of the injuries that occur are not easily detected from a distance or from the outside, and because, in general, horses are very good at masking the pain and discomfort caused by these injuries.   There are many different types of injuries and the head is an area that is often overlooked during any immediate checks following an accident.   A significant percentage of head trauma injuries involve damage to the dental tissues.   It is important to conduct a careful examination of the head and oral cavity, including dental tissues, whenever an injury has occurred that could have involved damage to these areas.   This includes incidents such as floating accidents, paddock injuries and falls.   Although facial trauma and injuries are commonly missed, there are some signs that might alert an owner and entice them to ask their veterinarian to investigate further.   For example, any sign of blood from the mouth or nose, an unpleasant smell, lumps or bumps around the face, and any difficulty eating should certainly warrant further investigation of the mouth and dental tissues.

Nevertheless, it is also important to understand, even when you don’t notice any of the signs mentioned above, your horse could still have undiagnosed dental trauma from head injury. The definitive way to determine whether or not your horse is affected by previous head trauma, resulting in dental disease, is to have them examined by an experienced equine dental veterinarian. This may lead to the need for further diagnostic tools, such as dental X-rays or CT scans. One of the things that is probably the hardest to appreciate as an owner is the difference between that which might appear ugly and shocking when it comes to injury and disease, and that which might appear subtle, but can actually be evidence of disease, leading to serious chronic pain and suffering.

An example of this is shown in Images A and B

Despite being quite shocking in appearance, this example is easily managed. This type of fracture is probably one of the most common types of dental injury. Image courtesy Advanced Equine Dentistry.
Despite not appearing very obvious nor dramatic, this is, in fact, very serious for the horse if left untreated. This example is also a very common result of dental injury. Image courtesy Advanced Equine Dentistry.

 

 

 

 

 

 

 

 

 

Common injuries So, just how common are injuries that damage dental structures, and what are perhaps the more common types of damage and how do they occur? Injuries to dental structures are extremely common. It would be a very unusual day at the practice if we did not see several horses affected with these types of injury.

Injuries can be broken down into categories based on:

  • Where they occur in the mouth,
  • At what age or stage of development they happen,
  • Which dental tissues are affected,
  • Whether they occurred recently or are older injuries just being discovered,
  • Whether they involve acute or chronic infection,
  • Risk of exposure to infectious organisms, and
  • Injuries affecting horses who are immune-compromised, such as those with PPID.

Let’s begin by looking at age

As I mentioned, young horses are curious and prone to injury. You may already know that injuries to some other parts of the body (e.g. the joints) have an impact on development and the same is true of injuries involving dental tissues. At or close to birth, injuries to both the front teeth (incisors) and cheek teeth (pre molars) can affect not only the present deciduous, or ‘baby’, teeth, but also the developing adult teeth, which will replace them into adulthood. Tooth development, and indeed tooth eruption, are actually quite complex processes; it takes only slight interference to potentially have a big impact on the outcome.

In very young horses (horses don’t really begin to shed any deciduous teeth until approximately two years of age), injury to the teeth and surrounding bones can disrupt the position of both their baby teeth and the developing adult teeth. A consequence of injury is often malposition of the adult tooth and a failure to shed the deciduous tooth. If detected early, this can often be corrected without any ongoing or specific care being required. However, if the problem is not picked up early enough and the horse is left with issues, such as retained and crooked teeth, this may result in gum disease and, in some cases, ongoing trauma to other dental tissues, like the lips or tongue. Another potential consequence of injury at a young age is the adult tooth may develop abnormally (dysplasia) or fail to develop at all (oligodontia). Both of these situations require ongoing care, but are usually easily managed with regular dental checks by a dental veterinarian. Injury at any age can result in either ‘luxation’ or ‘avulsion’ of teeth, but what does that mean?

Luxation means tissues around the tooth or teeth have been weakened and damaged, making the tooth loose and more than likely displaced from its normal position. There is damage to the periodontal ligament, and bruising or fracture of the surrounding alveolar bone. Avulsion means the same process has occurred, but the degree of damage has actually removed the tooth from its socket. This occurs following forced fracture and/or tearing of the alveolar bone which surrounds the tooth. Because in a young horse injury affecting deciduous teeth may also affect the adult permanent teeth, there can be a lag period lasting several years between the time when the injury first occurred and its assessment, and the time when the final effects can be fully evaluated. Now… If all this talk of injury, how common it is and how long you might have to wait to find out the full extent of the damage is causing you to feel anxious… Don’t worry.

Although these injuries are common:

• Much can be done to repair them,

• Horses cope well with missing teeth,

• Your equine dental veterinarian will work to ensure normal jaw function, as well as freedom from pain or infection.

So, that’s a very brief look at dental injury affecting young horses. Now, let’s talk about injuries affecting horses at the other end of life – the older, senior horses. There are some specific changes that take place as horses age, which affect not only their teeth and bones, but, in some cases, their ability to cope with wounds and minor infections. As horses reach their late teens and enter their 20’s, several changes take place. Horse’s teeth are normally composed of three separate mineralised tissues: enamel, cementum and dentine. In older animals, however, the enamel wears away, leaving only the softer cementum and dentine. This happens at a variable rate within individual horses and also between different teeth within the same horse’s mouth. As a result, teeth may wear abnormally – becoming sharp in unusual places or ways, and possibly more prone to fracture. The next related change occurs in the surrounding bone. Just like people, as horses age, calcium begins to be lost from within bones (osteoporosis), making them weaker, and more at risk of fracture under pressure or injury.

The third and final change that occurs commonly in older horses is the development of Cushings disease – more accurately termed Pituitary Pars Intermedia Dysfunction (PPID) – where the pituitary gland, also known as the ‘master’ or ‘control’ gland, becomes enlarged or is affected by a benign tumour (one that does not spread to other body parts). The effects of PPID include, but are not limited to, a decreased ability of the immune system to cope with wounds or infection. Therefore, three most common dental injuries in older horses are:

  • Fractured teeth associated with loss of enamel or pre-existing infection,
    Whenever there is facial trauma or injury, it is crucial your horse receives a thorough examination by an experienced equine dental veterinarian.
  • Bone fractures associated with osteoporosis, and
  • Non-healing, chronic wounds associated with PPID.

Obviously, it is very important to identify and rectify all three to ensure the comfort, health and longevity of our older, senior horses. In regards to PPID horses, their wounds will only heal if, as well as addressing the cause of the injury, medication is used appropriately to manage the effects of their PPID condition.

Healing

Injury involving dental tissues should be treated just like any other kind of potentially serious trauma. The seriousness of the injury, its treatment, management and the prognosis following facial trauma, will depend on which tissues are affected, how long the injury has been present before being identified, and whether there is infection or ‘sequestrae’ present. Sequestrum is an area of bone which has lost its blood supply and is no longer recognised as part of the body, but rather as a foreign agent. Sequestrum has a negative effect on the body’s ability to heal wounds and injuries, and are a frequent cause of ongoing infection after an injury. All teeth contain both sensitive nerves and blood vessels so, whenever a horse suffers dental trauma, both these structures can be damaged.

When an injury is detected early, one of the key first aid steps your dental veterinarian should take is to check for any evidence of damage to, or exposure of these tissues to the mouth and the bacteria it contains. If there is exposure of nerves or blood vessels, there is also a likelihood of swelling or infection, so in much the same way your regular veterinarian helps you manage other injuries, part of the first aid process is likely to involve the use of anti-inflammatories and antibiotics. Each case and situation is unique, and your dental veterinarian should discuss the specifics of your horse’s injuries, along with any other considerations that relate to other injuries, health conditions or the administration of medications.

Pulp caps

Where there is acute damage (very recent damage) and where live nerves within broken teeth are now exposed within the mouth, a procedure called ‘vital pulpotomy’ is often performed.

Vital pulpotomy (‘pulp cap’ or ‘pulp dressing’) relates to the tooth’s ability for repair. The aim of this procedure is to stimulate the tooth to lay down a protective layer over the remaining nerve tissue, and to prevent bacteria from entering and killing the tooth. Pulp capping can be thought of as a kind of emergency filling, but horse owners need to bear in mind that it must be performed very close to the time of the original injury to be effective. In other words, it is not suitable for injuries more than one or two days old. Its effectiveness also varies depending on the type of tooth that is affected (incisor, canine or cheek tooth).

Bone fractures

Lastly, let’s talk briefly about injuries to bones around teeth, because fractures to different parts of the skull following injury are relatively common. It may sound surprising, but skull fractures can be hard to detect and diagnose, even with X-rays, and sometimes require CT scans.

Management, treatment and prognosis will vary enormously depending on where they occur in the skull, whether they are found early (acute) or later (chronic), whether there is infection or sequestrum, and the type of fracture. Remember, most horses with bone fractures of the skull, including jaw fractures, will still appear to eat normally. Often, dental trauma will involve fractures to both bone and teeth simultaneously. As a broad rule of thumb, initial treatment will involve assessment of any bone fractures. First, partially to assess the safety or suitability of using specific dental equipment to assess the dental structures in more detail. Then, any teeth or fragments that cannot be stabilised will be removed, any vital pulp (nerves) in recent injuries will be protected with pulp capping and rough surfaces will be smoothed to prevent soft tissue trauma. Following bone fracture repair, teeth that are compromised will be removed. This is done later because several of the tissues within teeth do have some ability for repair (just like bone) and, therefore, deserve a chance to heal, and because, where possible, we want any bone fracture to be repaired and stable before tooth removal occurs.

Types of fractures

Pulp capping can be thought of as an emergency filling to cover a painful, exposed nerve. However, it must be performed very close to the time of the original injury to be effective.

As mentioned above, fractures of bone and teeth can occur in many types. Think of snapping a twig in the middle versus breaking the same twig into lots and lots of pieces. These two types of fractures are described as ‘greenstick’ (the snapped twig) and ‘comminuted’ (where the end result is lots of pieces of twig). One of the other assessments of fractures is whether they are stable or unstable. An example of this would be when one half of the lower jaw (the mandible) is fractured, but the fracture has some stability and support from the other half of the jaw, and the surrounding muscles. In contrast, if the fracture affects both halves of the jaw, the fractured area moves without support and is considered unstable. Comminuted fractures will feature small parts that become sequestrum and will have problems with infection. Unstable fractures require, where possible, stabilisation and support to allow osteogenesis (bone production) and knitting together of bone at the site of the fracture.

Dental trauma takes many forms. Here you see a stick has become lodged in the top palate.

 

Summary

Dental injuries are very common – even more than you can imagine – which is why detecting problems following any other type of accident or injury should never be overlooked. It is not just the obvious cases of head trauma that requires a thorough head and oral cavity examination. It is also important to get the right help and advice when it comes to dental injuries, so you are best to seek out equine dental veterinarians experienced in this area.

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