Signs of Oral Discomfort
Oral discomfort in the equine can arise due to a number of different factors such as genetics, diet/nutrition, habitat and physical or mechanical factors (bits and bridles).
In turn these factors give rise to the improper position and contact between teeth, a term known as a malocclusion (or malocclusions).
Malocclusions will have adverse effects to not only proper mastication but also to surrounding soft tissues in the oral cavity and optimum ridden performance.
These malocclusions may - and certainly if left unaddressed - manifest as any of the following outward signs of oral discomfort;
Loss of condition
Dropping hard feed
Dunking hay in water
Quidding (balling up and spitting out of partially chewed hay)
Packing grass or hay into the cheeks
Unsteadiness in the rein contact
Bad behaviour when ridden
The Equine Skull
In order to identify, understand why they occur and address such problems, it is essential to understand the equine skull.
Composed of a set of 12 deciduous incisors that erupt between 1 week and 6 months of age and are replaced between the ages of 2.5 years and 4.5 years with 12 permanent incisors, the equine incisor arcades are used for the biting and tearing of food.
In its natural habitat, the equine may spend upto 16 hours a day grazing, however the domestic and stabled equine may not. This results in a decreased rate of natural incisor wear, whereby malocclusions may occur due to a constant rate of tooth eruption.
Characterised by the lower corner incisors becoming dominant relative to the upper corner incisors, a ventral curve or 'smile' may occur due to either retained deciduous caps on the upper corner incisors or abnormal mastication as a result of pre molar and molar malocclusions.
The upper and lower incisors will cam, forcing the pre molars and molars apart too early in the mastication cycle and steep table angles of the pre molars and molars often result. Reduction of the lower corner incisors and central upper incisors will address this problem and allow correct lateral excursion to separation of the mandible relative to the maxilla.
The opposite of a ventral curvature, a dorsal curvature or 'frown' occurs in a similar but opposite fashion. Again, lateral excursion problems and pre molar and molar malocclusions will result. The dorsal curvature is corrected in a smilier way to the ventral curvature though incisor reduction and realignment.
Seen due to the upper corner incisors in one quadrant being dominant (or overlong) and the lower corner incisors in the opposite and adjacent quadrant being dominant (or overlong), the result of which is a meeting of the incisors on a diagonal or 'slant' that may occur in either direction.
A diagonal bit can occur over time due to mastication being favoured on one side of the mouth or by cribbing. It may also occur secondary to pre molar and molar malocclusions or missing or damaged incisors, whereby the opposing incisors become dominant.
A diagonal bite will also cause both excessive pre molar and molar wear to one side of the mouth and overlong pre molars and molars with a steep table angle (shear mouth) to the other. Furthermore this will result pain and discomfort to the temporomandibular joint and surrounding tissues.
This type of incisor malocclusion may be addressed over a series of staged corrections involving again, incisors reductions and realignments, with corresponding pre molar and molar corrections.
Pertaining only to permanent incisors, it is the opposing teeth to missing or damaged incisors that will result in this type of incisor malocclusion.
Incisor 'locking' will occur as the opposing healthy tooth continues to erupts, with a decreased rate of wear, into the 'gap' and subsequently blocks any lateral excursion of the mandible relative to the maxilla. Furthermore a greater degree of vertical mastication and subsequent quidding will arise, but can however be addressed by regular single incisor reductions.
Commonly referred to as 'Parrot Mouth' or Brachygnathism, an overbite is seen as the upper incisors (or Premaxilla) protrude in front of the lower incisors (mandible).
A common problem, an overbite can be a hereditary and developmental condition that can either be caused by or give rise large rostral and caudal hooks and ramps. This in turn creates misalignment between the mandible and maxilla, induces stress upon the temporomandibular joint as the anterior - posterior movement of the mandible is restricted and over time can accentuate rostral and caudal hooks, excessive transverse ridges, wave complexes and steep table angles or the pre molars and molars.
Addressing this type of incisor malocclusion involves upper incisor arcade reductions and pre molar and molar malocclusion correction.
A malocclusion/condition similar - but opposite - to an overbite, an underbite is also known as Prognathism or commonly referred to as 'Sow Mouth'.
This type malocclusion is rare and occurs due to [mainly] hereditary but also developmental factors. The condition will also be caused by or give rise to large lower pre molar ramps and lead to similar problems as seen with Overbites. Again, lower incisor arcade reduction and pre molar and molar malocclusion corrections are performed to address this type of malocclusion.
Although not involved in mastication or implicated in a ridden or working context with a bit or bridle, the canines or 'tushes' are over time susceptible to becoming overlong and sharp. With undue care this leaves them liable cause soft tissue trauma to surrounding tissues.
Furthermore the lower canines are a common site for the build up of supra gingival calculus due their proximity to the sub lingual salivary gland.
If deposits are not removed regularly, this makes them susceptible to peripheral caries.
Pre-Molar and Molar Problems
Composed of a set of 12 deciduous premolars present at birth that are replaced with a set of 12 permanent premolars between the ages of 2.5 years and 4 years and 12 permanent molars that erupt between 1 and 4.5 years, the equine pre molar and molar arcades are used for the chewing and grinding (mastication) of food.
In its natural habitat, the equine may spend upto 16 hours a day grazing, however the domestic and stabled equine may not. This results in a decreased rate of natural pre molar and molar wear, whereby malocclusions may occur due to a constant rate of tooth eruption.
Mainly found in the maxilla, wolf teeth are vestigial teeth often found in close proximity to the pre molar and molar arcades.
Sometimes referred to as the true first pre molar, it is due to this proximity that they often interfere with the action of the bit or become sensitive to the action of the bit and, with exceptions (age, size, formation, etc.), are commonly extracted - unerupted (blind) wolf teeth more so. Interestingly, it has recently been discovered that Wolf Teeth extractions - and other equine dentistry techniques employed to improve horse health and comfort - have been carried out on ridden horses in Mongolia as far back as 1300BC!
Deciduous teeth (also known as milk teeth or caps) of the pre molar arcades are shed between the ages of 2.5 - 4 years in the transition from deciduous to permanent teeth.
These deciduous teeth (or caps) may experience trouble being pushed clear [shed] by the underlying erupting permanent pre-molar. This may cause the cap to become retained and possibly infected causing foul odour. Dental cysts (or eruption bumps) of the mandible and the maxilla may then also be observed, but gradually disappear over time.
Retained caps may become a painful , often causing quidding impeded mastication and head tossing but may be remedied by removal during a routine dental examination.
Defined as the dominant overhang of the upper or lower first premolar or last molar, Hooks develop due to the misalignment of the mandible relative to the maxilla and are often seen in conjunction with an overbite or underbite (due to Hereditary reasons but can form due to developmental reasons such as secondary to pre molar and molar malocclusions). Being unopposed, hooks are liable to become more and more pronounced over time that will inevitably lead to bit/ridden discomfort, temporomandibular joint stress, decreased anterior- posterior movement of the mandible relative to the maxilla, quidding and possibly choke/colic.
Regular preventative maintenance can be performed to prevent reoccurrence by reduction of this [what is also termed as] focal overgrowth to a more regular clinical crown height compared to adjacent teeth.
Similar to hooks but having a more gradual slope to the tooth of less than 45°, ramps may be found on upper or lower first pre molars or last molars and may form over time due to opposing retained caps or if opposing tooth reduction is too great. Like hooks, ramps may lead to bit/ridden discomfort, decreased anterior- posterior movement of the mandible relative to the maxilla, temporomandibular joint stress and formation of overbite or underbite. Again, regular dominant tooth reductions will correct this malocclusion over time.
Sharp Enamel Points
Naturally forming over time due to the tooth structure and the mechanics of mastication, sharp enamel points are normally found on the outside (buccal) edge of the upper pre molars and molars and the inner (lingual) age of the lower pre molars and molars. Sharp email points are easily removed during a routine float, but however if left unaddressed are liable to cause lacerations and ulcerations to nearby soft tissues in the oral cavity - and are certainly accentuated when the action of an applied bit and bridle brings nearby soft tissues into closer proximity to this type of malocclusion.
Excessive Transverse Ridges
Excessive transverse ridges often form when a shift in mandible alignment occurs and the normal transverse ridges that run across the occlusal surface of the teeth become enlarged. This happens due to the higher density structures of one tooth now causing excessive wear to the lower density structures of the opposing tooth during the mastication cycle.
If left untreated anterior - posterior mandibular movement becomes impeded, affecting the temporomandibular joint and diastema and periodontal pockets may eventually form - but the condition is however remedied by regular routine dental floating and reductions.
The term wave mouth describes the uneven wavelike appearance of the pre molar and molar arcades that forms over time secondary due to malocclusions such as retained caps, missing teeth, hooks, ramps, dominant lower last premolars, dominant upper second molars and general lack of dental attention during early ages.
If left untreated, the wave mouth may cause decreased lateral excursion to separation of the mandible relative to the maxilla, gradual excessive wear to many pre molars and molars, periodontal pocketing (see below) and the early decay and premature loss of teeth.
The wave mouth can be difficult to correct in older age, however with regular 6 monthly treatments of preventative maintenance (by reductions of dominant teeth) the condition may be greatly improved and remedied in younger ages.
A step mouth occurs when the clinical crown of one cheek tooth is greater than those in the rest of the arcade usually from missing a tooth, or is opposed to a damaged or impacted tooth. The resultant "step" in the molar arcade restricts both the lateral excursion to separation and the anterior/ posterior movement of the mandible relative to the maxilla.
Regular maintenance through clinical crown height reductions of the dominant tooth will correct this type of malocclusion.
Occurring due to mastication being favoured on one side of the mouth and lack of lateral excursion of the mandible relative to the maxilla, shear mouth is seen as extreme angulation of the occlusal surface of the pre molar and molar arcades on one side of the mouth. the condition is also seen in conjunction with a diagonal bite.
This is quite a rare condition but can be treated over time by means of table angle realignment in conjunction with incisor reductions and realignments.
Caries describes decay and disease or infection of teeth that occur due to excessive or poor nutrition, trauma or abnormal wear over a long period of time.
The types main types of caries seen in equines are infundibular and peripheral.
Infundibular caries, most commonly seen in the upper first pre molars and first molars can be treated via restorative treatment to preserve tooth integrity.
Peripheral caries - affecting the periphery of the tooth - may be treated by more preventative means and regular maintenance.
Displaced and Rotated Teeth
Pertaining to mainly the pre molar and molars, displacement or rotation of teeth may occur due overcrowding of the teeth arcades where individual teeth are short of space.
Periodontal pocket formation and ulceration to the tongue or cheeks around these teeth are both common and painful.
While severely displaced cheek teeth may require extraction, routine removal of sharp edges will prevent ulceration and soft tissue damage.
A diastema is the gap that occurs between two adjacent teeth and often results as opposing malocclusions force two adjacent teeth apart in a rostral/caudal direction.
Food and grass impaction into the diastema persistently occurs, eventually leading to progressive and severe periodontal disease and gum recession where quidding and foul odour will often be observed.
Early identification and correction of malocclusions is key to preventing diastema formation, but should diastema form, regular picking and flushing of diastema with possible widening or filling may successfully treat the condition.
Supernumerary or ‘extra’ teeth are rare but if present are usually unopposed. Regular reductions of the clinical crown height of these unopposed supernumerary teeth is vital to preserve the integrity of opposing and adjacent soft tissues in the oral cavity.