Diagnostic Methods

BEHAVIOUR AND RESTRAINT METHODS

A knowledge and understanding of the unique characteristics of the donkey is valuable when handling and examining this animal. Giving the animal a good experience will reduce the risk of the donkey becoming fearful and, as a result of a bad experience, difficult to restrain for future examinations and for dental procedures.

Where the donkey is fearful, and difficult to handle as a result, a shaping plan can be used to reduce fear and provide a positive experience.

There will be occasions when examinations and any procedures cannot be carried out and then other methods of restraint will have to be considered. These may include sedation.

SEDATION

Chemical restraint may be necessary in some donkeys in order to carry out a full examination of the oral cavity.

The common route of administration will be by intravenous injection but there will be occasions when it may be preferable to administer sedatives by the intramuscular or oral route. Examples include sedation of mules, or where there is existing knowledge of a problem in handling a donkey. It is preferable to sedate the donkey before it becomes stressed or experiences fear, improving sedation and reducing long-term issues with needle sensitisation.

Options for sedating a donkey are similar to those for nervous or fractious horses. Vets may choose to supply an owner with an oral sedative for use before the professional's arrival. The Donkey Sanctuary uses oral detomidine gel at standard equine doses.

CLINICAL EXAMINATION

A thorough examination of the oral cavity is an important part of any clinical examination, both in routine preventative health programmes and in the clinical examination of a sick or ailing donkey. Oral or dental disease may be associated with, or the cause of, many systemic conditions such as weight loss, diarrhoea and recurrent colic, although it is common to find severe dental pathology with no clinical signs. There are anatomical and functional relationships between all of the structures in the head and oral cavity and this reinforces the importance of a complete and systematic clinical examination of the head, even when the main objective is the examination and diagnosis of possible dental disorders. Any other conditions in the animal need to be identified because they may affect and impact the delivery of proper dental care, including post procedural care, or even whether treatment is contraindicated.

A good treatment plan is only possible if a correct diagnosis is achieved. If necessary, ancillary diagnostic tests may be used in order to reach a correct diagnosis.

The clinical examination can be split into stages: clinical history, observation, extra-oral examination and intra-oral examination. Each stage is equally important and shouldn’t be ignored.

It is essential to record any findings in order to:

• share information and necessary treatment or follow-up actions with the owner/handler
• share information and necessary treatment or follow-up actions with other professionals, especially if referring
• monitor dental health
• produce a dental treatment plan.

It is necessary to understand the behaviour of the donkey in order to detect clinical signs and deterioration in condition.

Clinical history

In the majority of cases the owner will only be aware of behavioural and clinical signs when more obvious signs of discomfort or pain are expressed. The common changes detected by owners are:

• slow or intermittent eating; sometimes complete reluctance/ inappetance

• head shaking

• quidding

• visible changes in shape and symmetry of the head

• halitosis

• abnormal behaviour

• protrusion of the tongue

• drooling/excessive salivation

• oral malodour

• abnormal sounds during chewing

• blood in the mouth

• nasal (and sometimes lacrimal) discharge

• weight loss.

It must be stressed that donkeys generally only tend to show signs of dental disorders once they have become severe. Professionals are therefore encouraged to engage in regular prophylactic examination and treatment, rather than to respond to cases once signs are established.

It is very important to collect information about the donkey’s temperament and behaviour, eating and management habits, possible vices, and the presence of recent changes in all these aspects, and to try to correlate the information obtained with the presence of possible oral and dental disorders.

Other important information, such as vaccination status, is necessary, especially in those countries where zoonotic diseases may be a serious health risk. All animals receiving dental examination and treatment should be covered against tetanus. Dental procedures may cause oral abrasions, so unvaccinated animals should receive tetanus toxoid during dental treatment.

Observation

Whenever possible, donkeys should be observed in their natural environment and this should include time spent eating and drinking. This will allow identification of valuable information, such as:

• any behavioural issues or changes

• signs of vices or remnants of poorly chewed food in the immediate environment and in feeders and drinkers

• remnants of food in the drinkers where animals are not usually able to re-eat the food dropped in the water, to eliminate signs of quidding

• undigested grain or more commonly increased fibre length in the manure.

Observation is not always possible because owners may bring their animals to mobile clinics away from their natural environment. In these cases the history will be very important.

In the early stages of rabies it is common that suspicions may only become aroused during the oral examination, hence the importance of appropriate Personal Protective Equipment (PPE) in all extra- and intra-oral examinations. Any animal that prehends or accepts food intake but fails to complete deglutition should be investigated thoroughly before continuation of dental assessment.

Observe the behaviour of the donkey, especially in relation to the owner or handler. Restraint of the donkey is especially important for the examination of the oral cavity and it may be beneficial to use an experienced handler if the donkey appears to be agitated or stressed in the presence of the owner.

The behaviour of the donkey should be considered, based on the observations, when deciding on the best method of restraint.

Extra-oral examination

A general clinical examination should always be completed. Dental conditions may often be associated with systemic conditions and obvious clinical signs may be absent. The examination of the donkey should include body condition scoring.

A visual, olfactory and tactile examination of the head should be carried out, checking both hard and soft head tissues for evidence of pathological changes, with special emphasis on those structures related with the oral cavity. This is especially important because the head of the donkey can often be very hairy and any external alterations may remain undiagnosed. Any deviations from normal conformation or asymmetry of the exterior of the head must be investigated and oro-dental pathology ruled out and/or referred to a specialist.

The examination should be performed standing directly in front of the donkey’s head and should include:

• evaluation of the conformation and symmetry of all anatomical structures, using both hands simultaneously to check deformations or enlargements in all hard and soft tissues, including the salivary glands and regional lymph nodes

• a check for muscular tonus/atrophy/inflammation (mainly the key masticatory muscles, masseter and temporal)

• a check for the presence of nasal and ocular discharge

• a check for lesions of any tissues including mucocutaneous borders and fistulas, which may indicate the presence of oro-dental disorders.

Professionals should be comfortable with age-related dental anatomy for instances where an owner has no history or knowledge of the animal’s age, or where there are discrepancies between the estimated age and the pathologies noted. It is useful to know the age of the donkey under examination, in order to place possible dental disorders in the context of age-related alterations such as the presence of eruption cysts in the central aspect of the mandible.

A lateral examination should also be performed.

If possible, before the extra-oral examination, the donkey should be observed while eating in order to evaluate the chewing movement and identify any abnormal sound or abnormal chewing pattern that may restrict free jaw excursion. This allows correlation with any clinical signs such as quidding or drooling. If observation is not possible, lateral excursion of the mandible should be performed to look for possible mechanical impingement (unilateral or bilateral) or painful reactions; pathology is often noted at the affected/restricted side. Rostrocaudal movement may also be assessed, extending and raising the head, followed by assisted flexion.

The close contact with the facial region also allows the professional to create a bond with the animal, facilitating further clinical procedures. Donkeys will often react to the way in which the professional is introduced and this can form the basis of their interaction for the duration. A calm, confident and quiet approach will reassure the animal that compliance is safe. A situation where the animal is overwhelmed by manual assistance or is physically crushed between inanimate objects should always be avoided.

Nociceptive tests

Behavioural indicators of pain may be less obvious in donkeys, mainly because of their greater stoicism, which means that behavioural changes are very subtle and hard to interpret.

Manual nociceptive tests (pressure tests) evaluate the donkey’s behavioural response in order to assess pain. When a nociceptive test causes severe and/or acute pain, donkeys will show the same positive response shown
by horses.

These tests should be part of any clinical examination because they are an effective way to obtain reliable information about oral pain and discomfort.

Tests include:

• Cheek pressure can be tested by exerting pressure bilaterally and simultaneously on the cheeks at the level of the maxillary cheek teeth by pressing the cheek against the entire cheek teeth row, starting from the level of the medial canthus of the eye and progressing rostrally over the masseter muscle to the level of the nasal notch. If the animal shows signs of discomfort by evasion, it is most likely the result of pain from sharp cheek teeth that can press against the buccal mucosa. This clinical procedure may also detect any other abnormalities of the upper cheek teeth (eg displaced teeth and focal overgrowths) and may result in a similar reaction.

• Tongue/hyoid pressure causes animals presenting ulcers or lacerations of the tongue because of dental trauma at the back of the mouth to demonstrate signs of evasion due to discomfort, including moving the head away from the source of pain. Even without soft tissue lesions, equids may show a positive response to pressure tests if the mandibular cheek teeth are sharp or if lingually displaced cheek teeth are present. Pressure is exerted bilaterally on the intermandibular space, pushing the body of tongue dorsally, leading to close contact between mandibular cheek teeth and the lateral aspect of the tongue. This is primarily aided by the transversal fungiform shape of the equid’s tongue.
  
  These reactions to pain may allow the operator to visually demonstrate to owners that the enamel points need to be conservatively reduced, which is useful in cases where treatment necessity is contentious. Of course, the prophylactic nature of dental treatment would aim to limit the occurrence of oral pain from sharp teeth in the first instance.

Prior knowledge of the presence of abnormal sharp dental structures should determine the way the mouth is opened during the intra-oral exam; if the mouth is fully opened with the speculum in place, the cheeks will be pushed tightly against the cheek teeth row, causing oral discomfort and potentially leading to soft tissue damage in extreme cases.

• Temporomandibular joint (TMJ) pressure will identify clinical signs of disease affecting the temporomandibular joint, including signs of pain/ evasion during palpation of the joint (positive response to pressure tests), or rostrocaudal and lateral manipulation of the mandible, or both when evaluating the range of mandible motion. This test is somewhat contentious in terms of the ability to definitively diagnose dentally related pathology, given the limited amount of the joint accessible for palpation, but it may be useful to indicate responses that may correlate to dental disease or influence treatment. A positive response to this test may indicate the presence of more chronic and severe oral disorders, but it also dictates that the professional must be even more conservative about the time the speculum will remain open during intra-oral examination and treatment.

The Donkey Sanctuary ensures frequent rest periods whereby the speculum is fully closed in order to avoid iatrogenic damage of the temporomandibular joint.

Intra-oral examination

In order to perform a correct intra-oral examination, it is important to flush the oral cavity (using a dosing syringe or irrigation unit with a blunt ending), eliminating all food debris that may interfere with it.

Consideration must be given to the rinsing product to be used for a successful intra-oral examination, routine treatment and dental equilibration. For example this would be distinct from endodontic irrigation.

Unsedated donkeys may severely object to oral rinsing. The presence of water under pressure in the oral cavity stimulates the soft palate to contract, causing a rostral displacement of the palatopharyngeal arch, leading to a blockage of the entrance of the trachea. Therefore, a donkey’s mouth should not be flushed with the gag on and the mouth open. Animals will rapidly calm down and start breathing normally following rinsing. If necessary, the throat region should be stimulated and donkeys will swallow, relaxing all the adjacent structures.

To allow a complete intra-oral examination, animals should be properly restrained, ensuring the security of the professional, animal and equipment. However, any restraint applied to the head (ie head collar) should be adjusted (ie removed or the noseband undone) to ensure that the soft tissues are not pushed against the cheek teeth during examination or treatment.

The majority of donkeys allow the intra-oral examination and non-painful procedures without the need to be sedated and they rarely show the violent response sometimes seen in horses. If sedation is preferred, use similar doses per kg as those used for horses and note that there is a shorter period of action in donkeys.

When working with an unsedated donkey, best practice is to keep the head elevated without generating a negative behavioural response. A hanging halter with a quick release safety system will allow for rapid response to a changing situation. Such ancillary equipment will be useful in many clinic (including mobile) situations, including those with limited resources where professionals may use the animal’s own head collar (although it’s beneficial for this to be oversized) with a long length of rope or cord and a clam/ fender cleat. Elevation of the head will reduce the donkey’s attempts to escape, by counteracting its natural way of escape: head to the floor while trying to move away. A similar system could be replicated using a headstand, although the professional should be mindful of the possibility of additional risk. In order to avoid accidents, unsedated animals should never be left unattended with the mouth open while supported from the halter. With sedated animals the head should be at the same level as the back and neck and no higher, to ensure stability of the hind limbs.

Horses, ponies and most mules will naturally hold their heads much higher during routine dental procedures without sedation, whereas donkeys will not. This means that the professional will need to have a means of supporting the donkey’s head during the examination or will need to bend/sit down where safe to do so, to enable a full view of the oral cavity.

During the sedation the headstand must be high enough to offer the animal complete support. For example, if the headstand is too low, horses in particular will raise their heads above the stand, rendering it an obsolete and unnecessary obstacle. Should the horse change its head position rapidly in a dorso-ventral plane and repeatedly (ie nodding) above the headstand, this is often an indication that more sedation is required, that the speculum might be fitted too tightly at the poll strap, and/or that the headstand is too low. If the animal is not reacting in a desirable or expected manner, it is usually because it is in discomfort, pain and/or fear (potentially that it requires additional sedation); it is important that the professional pays attention to these behavioural indicators and takes action to resolve issues throughout all stages of examination and treatment.

Before fitting the full mouth speculum there should be a detailed examination of the rostral structures of the oral cavity, including incisors and canines (when present). Alterations to the normal number and position of the teeth, symmetry and occlusal surface, the presence of craniofacial abnormalities, or diseased incisors may lead the professional to slightly change the order of priorities and approach these teeth first. It is better to use ground-out incisor plates, even in donkeys with a few stable incisors or even no incisors at all, than to make use of the traditional ‘gum’ bars, which may inflict marked trauma to the interdental space, even when padded. In cases with a total absence of maxillary and/or mandibular incisor rows, professionals are encouraged to use periodontal dressing material to make a tailored protective cushion applied to the seat of the bite plates. These soft tissue guards can remain in the care of the owner and reused at subsequent appointments.

A recent study which focused on donkeys in the UK suggested that ventral curvature of the incisors is a normal feature in standard donkeys, while, another recent study focused on endangered donkey species in Portugal suggested that ventral curvature is an acquired disorder. In either instance, if necessary, phased correction is advised, with the aim of restoring normal incisor occlusion. Care must be taken to avoid a loss of incisor occlusion, which is highly undesirable. While ventral and dorsal curvature of the incisors is commonly considered pathological in horses, ponies and mules, treatment should only be considered in the donkey if the degree of deviation from the normal bite plane is sufficient to impinge upon normal, balanced lateral excursion.

The minimum equipment for a thorough oral examination is:

• a full mouth speculum

• a bright headlight

• an angled dental mirror (or dental endoscope/oroscope)

• a complete periodontal instrument set.

This will allow the professional to correctly examine:

• the number and position of teeth

• interproximal spaces

• periodontal tissues

• individual occlusal surface of CT (pulp horns and maxillary infundibula)

• possible variations to the normal occlusal surface of CT rows

• the integrity, tonus and functionality of the cheeks and tongue, not only the dorsal surface but also lateral and ventral surfaces

• the hard and soft palates

• the interdental space.

The tongue should be left completely free in the mouth in order to avoid serious lesions. If it is necessary to improve visualisation, a basket retractor may be used, keeping the tongue and oral mucosa away from the CT, allowing a correct dental evaluation.

The presence of wolf teeth should also be recorded. In donkeys it is normal to find up to four wolf teeth (one per arcade). In their normal position maxillary wolf teeth should not interfere with the bit and therefore their routine removal may not be required. Donkeys present a more rostral lip commissure than horses and ponies, so if the bit is properly used there should be no contact during bitting. Careful examination of donkeys with mandibular wolf teeth should include discussions on occupation and bitting to facilitate informed decision making about the requirement for extraction.

USE OF A DENTAL CHART

All identified oral and dental disorders should be recorded in a systematic way, and updated records should be kept, allowing a correct follow-up of the cases. Correct clinical language should be used at all times and the modified equine Triadan system should be used, ensuring correct collection of clinical data.

Pictures may prove to be a useful additional means of keeping records or monitoring progress, and also an excellent educational tool for owners.

Dental charting may be undertaken using traditional paper charts, typically with a carbon copy left with the owner. More recently, efforts have been made to develop electronic dental charting, using either pdf files that can be modified or dedicated device applications. Electronic charting offers the added benefits of cloud storage, sharing via email and appointment scheduling, in addition to being able to add images to the animal’s record. There are various commercial dental charting apps available on the market.

Recording of the dental examination should be considered obligatory in professional dentistry. Dental charting documents the status of health and disease of the teeth and oral cavity, and should also include the treatment performed and the plan for future assessments. It is the ideal place to record discussions with owners, provide recommendations for treatment, referral and further investigations (including non-dental), and make note of other advice given (such as feeding, faecal worm egg count (FWEC), vaccination).

A dental chart is usually required for insurance claims, and can be used for legal documentation. It is advisable to record all observations, conversations and treatments and to store them for the relevant number of years as required by local regulations.

Dental charts are generally completed using a set of common abbreviations. It is prudent to include a key to these abbreviations on the chart itself, for reference and explanation.

Additionally, it is usual to refer to equine teeth using a modified Triadan system, whereby each tooth is assigned a three digit number: the first digit refers to the quadrant and also indicates if the tooth is deciduous or permanent, and the remaining digits reference location within the quadrant.

ANCILLARY DIAGNOSTICS

Ancillary diagnostic tests may be used to achieve a definitive diagnosis, when clinical findings observed during the extra and intraoral examinations require further investigation. These further tests offer great improvements to the clinical capacity for visualising those parts of the head that cannot be sufficiently examined using conventional methods.

The demand for detailed, accurate and complete oro-dental examination to enable better understanding of pathological aetiology and achieve the gold standard of treatment/prophylaxis has increased exponentially in recent times. The development of technology and the availability of equipment has considerably eased the challenge of oral examination and owner compliance.

Even with contemporary specula, bright headlight and high degree of dexterity, the oral cavity still offers limited manoeuvrability coupled with restrictions to complete visualisation of all surfaces in many tissues and structures.

Dental endoscopy or oroscopy is gaining in popularity amongst veterinary and non-veterinary service professionals alike.

Oroscopy

As with many ancillary diagnostic aids, oroscopy may not provide complete information on its own and is best used in conjunction with standardised techniques of inspection in addition to other modalities such as radiography. Oroscopy offers an increase of around 88% in terms of the number of pathological conditions recognised with the exception of dental overgrowths, highlighting the use of this instrument as part of a complete assessment.

In many instances this will replace the use of mirrors for examination and to aid instrument positioning for treatment. Contemporary instruments are well guarded from chewing, wireless and may have independent batteries; with the ability to link to electronic devices such as smart phones and tablets in addition to laptops. The oroscope can be very portable for use in most field settings and allow for supplementary photographs to be added to case files.

Highly detailed imagery of the oral cavity may be achieved with oroscopy, affording the opportunity to record and review both images and videos with magnification. These images may then be stored on the animal’s records or are easily forwarded for referral/consultation.

Many professionals make oroscopy part of their routine dental examination in addition to performing guided techniques during treatment. Although an absolutely essential aid in the absence of oroscopy, a dental mirror is a poorer yet currently acceptable second. Either aid should form part of all routine dental examinations.

More recently, the improved affordability for high quality yet rugged mobile devices has meant that oroscopic examinations may be offered by a good proportion of well trained, competent Equine Dental Technicians. This welcomed increase in observational capability in turn sees an increase in veterinary referrals and early diagnosis even in mostly unsedated patients.

There are a vast array of scopes available for use in equine dentistry, but essentially they are made up of a camera and light mounted to a long rigid shaft with or without capture facility on the handle. The presence of the capture facility is highly recommended. The camera will usually be set at an angle of no less than 60°–70°, with some set at around 90°. The hand piece may communicate via direct attachment or via wired or wireless connection with either a camera (DSLR), laptop, processor and screen or in very mobile settings, may be paired wired or wirelessly to a tablet or smart phone (with casting to a bigger screen/monitor available in most cases).

Interpretation of oroscopic findings is usually straightforward, but does depends on explicit familiarity of dental anatomy and function.

It is becoming increasingly more common for service providers to offer oroscopic guided techniques for treatment; minimally invasive transbuccal screw techniques for dental extractions for example, rely on symbiotic relationship between the surgeon and the scope operative. Other techniques would include dental restorations.

Rhinoscopy

Where nasal discharge is seen, and especially unilateral discharge, rhinoscopy may be valuable. It will identify the presence of discharge in the lateral wall of the common/medium meatus and determine that the discharge is coming from the nasomaxillary opening. This will confirm the presence of sinus disease. Although, it is very important to mention that in donkeys and some mules, nasal passages are smaller than equal sized horses, so a correct choice of the diameter of the endoscope is very important, as well as lubrication of the equipment.

Radiography

This is perhaps one of the most commonly used diagnostic tools, especially with the advent of portable digital systems and the enhancement of radiographic techniques for the equid’s head. It enables good visibility of the unerupted crown.

It is important to remember that obtaining a 2D image of a 3D structure may cause difficulties in interpretation of results, especially if superimposition occurs, so good quality, well-positioned images are vital to aid diagnosis.

The most consistent radiographic signs indicating advanced apical infection include:

• periapical sclerosis
• periapical halo formation
• clubbing of one or two roots and the degree of clubbing • cementum deposition around the reserve crown
• cementoma formation
• reserve crown fragmentation
• reserve crown lucency
• dental dysplasia.

However, these signs often have a high specificity but low sensitivity so may generate few false positives but a high proportion of false negatives, and should be interpreted with care.

With the advent of digital radiography, professionals tend to take radiographs using a standard setting and manipulate the image (if required) on the viewing screen, avoiding the need to retake owing to under/over exposure.

Commonly used settings and projections are between 72 and 74 kV and 1.2 and 1.4 mAs, with adjustments made on the screen for digital radiography.

Different machines will require settings to be adjusted as necessary. We recommend keeping records of settings used and their success, so that these may be replicated in the future.

Adjustments for non-digital systems (Crawford, 2015).

There are several standard radiographic projections:

• Intra-oral: These are most commonly used for incisors and canines. The angle of projection will vary from 60 to 80° due to changes in the incisor angle as the animal ages.

Place the radiographic plate between the incisors, as far back as possible. A radiolucent speculum may be used to open the mouth, or sedation may be necessary to prevent chewing. Turning the cassette so the corner can be advanced will maximise space to capture the image.

• Intra-oral dorsoventral projections are commonly used for premaxillary incisors and intra-oral ventrodorsal views for mandibular incisors. The beam should be positioned bisecting the head. However, in some cases oblique views from each side may need to be obtained to avoid superimposition of the incisor apices. Lateral views may also be useful in some cases.

• Latero-lateral: Most commonly used to image the sinuses, because this view will cause superimposition of the cheek teeth apices. Centre the beam on the rostral aspect of the facial crest with minimal rostrocaudal angulation and the head unsupported, muzzle towards the ground. This will aid in the diagnosis of fluid within the sinuses.

• Dorsolateral-30–35°-ventrolateral oblique: Most commonly used to image the maxillary cheek teeth apices. Position the cassette vertically and adjacent to the side to be imaged. The beam should be between 30–35° dependant on the age of the animal and length of the reserve crowns and centred and collimated to include all six cheek teeth. It may be permissible to introduce a very slight rostrocaudal angulation to avoid superimposition of the three roots, but this is often personal preference.

• Ventrolateral 45° dorsolateral oblique: Most commonly used to image the mandibular cheek teeth apices. Note the steeper angle due to the decreased width between the mandibles. Again, collimation should ensure that all six cheek teeth are included within the image. Probes may be inserted into any draining tracts and taped in during exposure to give an indication of the affected crown.

Ventrolateral 45° dorsolateral oblique. 9 year old donkey with severely displaced 410 and surrounding periodontal disease grade 2. Note the presence of a halo around the apex of 410.

• Open mouth oblique views: Most commonly used to image the erupted crowns of the cheek teeth and often useful in assessing clinical consequences of diastemata. For maxillary crowns the projection is a ventrolateral 10–15° dorsolateral view and for mandibular crowns a dorsolateral 10–15° ventrolateral view.

• Dorsoventral views: Most commonly used to view radio-opacities differing from one side to the other, particularly in the ventral conchal sinus and soft tissue masses that may deviate the nasal septum. Obtained best with a sedated head placed on a low support so the cassette can rest directly under the mandible. The generator should be bisecting the head, causing superimposition of the mandibular and maxillary cheek teeth. An offset view to view the arcades in separation can be obtained by using a sliding speculum, or ropes around the mandible and pre-maxilla to draw them in opposite directions.

Other methods

Other imaging modalities such as ultrasonography, computed tomography (CT), magnetic resonance imaging (MRI) and nuclear scintigraphy may be extremely helpful in order to make a more definitive diagnosis, but the vast majority of this technology is only available in equine referral centres and university hospitals.