The most common dental (and indeed oral) disorder in horses is laceration of the cheeks and rarely the tongue by sharp dental overgrowths (‘enamel points’) that develop on the lateral (buccal) edges of the maxillary and the medial (lingual) edges of the mandibular cheek teeth (CT). Dental overgrowths may also occur along with other developmental and acquired dental disorders. Severe oral pain is most commonly caused by deep periodontal food pocketing, such as occurs with diastema(ata). Oral pain may result in small boluses of masticated food falling from the mouth during chewing, a condition termed "quidding," which may be visible on the ground outside the animal’s box or beneath the forage rack. Many horses will not lose weight until dental changes are very advanced.

Painful, dental-related lesions may also cause bit (bitting) problems, including resistance to the bit, abnormal head carriage and headshaking during work. A common cause of such problems are overgrowths on the buccal (lateral) aspect of the upper CT which traumatise the buccal mucosa due to noseband or bit pressure. 

Signs of CT infection include painful facial swellings (possibly with sinus tracts), especially unilateral swellings of the mandible or the rostral aspect of the maxillary bones, the latter are almost pathognomonic for apical infections. The presence of a unilateral nasal discharge (persistent and purulent, possibly malodorous) may be due to dental sinusitis. 

this will be covered in practical classes, especially in Final Year
The equine incisors and canine teeth are readily examined. This examination should be systematically performed prior to placement of a gag (speculum) to examine the CT. With the mouth closed, the mandible should be moved sideways and the degree of sideways movement prior to separation of the incisors (as the angled occlusal CT surfaces come in contact) should be assessed. Due to a combination of factors, including the limited angle of opening of the equine mouth, the rostral positioning of the lip commisures and the great length of the CT rows, it is difficult to visually examine all the CT, particularly the caudal CT, in unsedated horses. Palpation through the cheeks may reveal food pocketing or major irregularities (such as a missing tooth or large overgrowth) of the CT particularly of the rostral 3 upper and lower CT. Even if no abnormality is palpable externally, the presence of pain during palpation may indicate the presence of sharp enamel overgrowths on the lateral aspect of the upper CT. During eating forage, horses with dental pain may not make the normal vigorous crunching sounds and/or show restricted mandibular movements that may be confined to one side of the mouth, or even quid (drop unmasticated food). 

A detailed equine oral examination can only be performed using a full mouth gag. 

Some horses can be safely using a gag in without sedation, especially if similarly examined previously. For reasons of safety and efficacy of examination and treatment, uncooperative horses should be sedated during this procedure. If it is difficult to open horse’s mouth using a gag, first check that the nose-band is loose enough. Pushing a thumb on the horse’s hard palate will usually cause the horse to open its mouth further. Food retained in the oral cavity should be removed by flushing the oral cavity with a large dental (dosing) syringe of water or dilute disinfectant. A headlight, and a long handled dental mirror ( or oral endoscope) are necessary for a complete visual oral examination. Major problems, especially of the caudal lower CT, and the adjacent periodontal membranes can readily be missed unless all the teeth and adjacent gingiva are carefully visually examined and palpated. It is also useful to smell one's gloved hand after oral examination for the presence of foul smelling odour, which as noted, usually indicates anaerobic infections, most commonly of the periodontal tissues such as with diastemata. A significant equine CT disorder, especially in the younger horse is periapical abscessation, that is usually accompanied by infection of the supporting bones. In many cases, little gross change is visible in the clinical crown, except in some maxillary CT apical infections, where fractures and gross dental caries of the exposed crown may be present, however pulpar exposure will be found in many such teeth on careful examination using a dental mirror. Radiography and other imaging techniques are therefore essential in the investigation of such disorders. 

Compared to the CT, significant disorders of the equine incisors (and of canine or “wolf teeth”) are uncommon. However as the incisors can be readily examined in comparison to the CT, even minor incisor disorders can be readily observed by both clients and veterinarians. 

Overjet and Overbite (“Parrot Mouth”) 

Very many horses have some degree of what the older textbooks term brachygnathism (“parrot mouth,” “overshot jaw”). Overjet is when upper incisors protrude rostrally in relation to the lower incisors; Overbite is when the upper incisors also lie directly in front of the lower incisors. In many of these cases, there may be an overlong maxilla, which also induces disorders of wear in the CT. Consequently, a major significance of overjet/bite is that they very commonly occur in conjunction with overgrowths of the rostral aspect of Triadan 106 & 206 and of the caudal aspects of the lower 311 & 411.

In older horses with overbite, the absence of wear on the central upper incisors may cause them to develop a convex occlusal surface, which has been termed a “smile.”Unless contact between opposing incisors is totally absent, this condition rarely causes the horse trouble in prehending food, but it is aesthetically undesirable, especially in show horses.

Foals can have their upper incisors surgically braced to their CT (possibly with use a biteplate attached to keep the lower incisors in occlusion). This is best performed at <6 months of age when much maxillary bone growth is still occurring, but the ethics of these orthodontic procedures, especially in animals that may be used for breeding, are debatable. In adults, these incisor overgrowths (and accompanying CT overgrowths) should be initially reduced in stages with power or manual instruments. Once the incisors have been reduced satisfactorily, they should be reduced bi-annually along with the 06 and 11 overgrowths 

Underbite (“Sow Mouth”) 

Prognathism (“sow mouth,” “monkey mouth,” “undershot jaw,” “underbite”) is very uncommon in the horse (more common in donkeys and miniature horses). It is also usually clinically insignificant unless there is total lack of occlusion between the upper and lower incisors. Severely affected horses will eventually develop a concave upper incisor occlusal surface, which has been termed a “frown” and may develop lower 06 and upper 11 overgrowths.

Displacements may be developmental or due to trauma to the foal’s head prior to eruption of the permanent incisors. If protruding at very abnormal angles – they will need to be extracted –otherwise regular floating may be sufficient. 

Deciduous incisors, which normally lie on the occlusal aspect or rostral (i.e. on the labial aspect) to their permanent counterparts, are occasionally retained beyond their normal time of shedding. If retained for a prolonged period they will cause the permanent incisor to be displaced further caudally and may even cause permanent wear changes in the incisor arcade. If loose, retained incisors can be removed using dental forceps. If more firmly attached, they will need to be extracted under sedation and local anaesthesia using dental elevators to remove the rostral alveolar wall. Retained incisors must be differentiated from supernumerary incisors (see below). 

Supernumerary Incisors 

Supernumerary (i.e. permanent incisors that are additional to the normal 6 incisors on each arcade) incisors have very long (<7.0 cm long) reserve crowns, that are usually intimately related to the reserve crowns and roots of the normal permanent incisors. Additionally, as the supernumerary incisors are identical in appearance to the normal incisors (i.e. are termed supplemental teeth) they are impossible to differentiate from normal incisors. Consequently, extraction of these supernumerary teeth is both very difficult and also risks damaging the normal teeth. As most supernumerary incisor teeth cause little clinical problems unless grossly displaced, they are usually best left alone, with bi-annual rasping of unopposed teeth to prevent overgrowths. 

Fractures of the incisor teeth, and often of the supporting rostral mandibular or premaxillary bones can occur due to trauma, usually from kicks, and commonly result in exposure of the pulp cavity (termed a complicated dental fracture). All teeth of young horses contain very wide apical foraminae (root canal openings), along with a very large and vascular pulp, which can resist the inflammation and infection that will inevitably develop in exposed pulp from saliva and oral bacteria. Consequently, pulp exposure, especially in younger horses, does not necessarily lead to deep pulpar infection and subsequent ischaemia with tooth loss, as usually occurs with pulp exposure in brachydont (e.g. human or canine) teeth. However, all incisor fracture cases should receive tetanus anti-toxin and prolonged (7-10 days) antibiotic (e.g. trimethoprim/sulfadiazine) therapy. Preferably, endodontic (root canal) treatment should be performed by a specialist veterinary surgeon to save the tooth. A first aid treatment is debridement of the exposed pulp with an 18g needle and application of a hard-setting calcium hydroxide paste into the overlying pulp canal to speed up reparative dentine production – could be performed by general practitioners. However, in some young horses the exposed pulp will, without treatment, become sealed off at the site of exposure by reparative (tertiary) dentine formation, with the tooth remaining vital and continuing to erupt normally. 

Abnormalities of Incisor Wear 

On full, manual, lateral movement of the mandible with the horse’s jaws closed, the incisors should separate. Abnormalities of the occlusal surface of the incisors (or large overgrowths of the CT) will prevent this normal maneuver, usually unilaterally. These incisor disorders include “steps” due to the traumatic loss or maleruption (delayed or other abnormalities of eruption) of the opposing incisor and subsequent overgrowth of the opposite incisor, as well as the previously noted “smile” and “frown” that occur with “parrot mouth” and “sow mouth,” respectively. The abnormal wear pattern of the rostral aspect of the central and sometimes of the middle incisors in crib-biters is well known. Such cases should have overgrown areas gradually (e.g. 3mm) reduced at 3 monthly intervals.

Equine Odontoclastic Tooth Resorption and Hypercementosis (EOTRH) 

This is a recently described, painful disorder of incisor and canine teeth of older horses, variably causing periodontitis, with resorptive and/or proliferative changes of all the calcified dental tissues. EOTRH shares many features with similar dental syndromes described in humans and cats, except for the high degree of hypercementosis that occurs in many affected horses. There is no known treatment and loose and painful teeth should be extracted. 

Slope Mouth (Slant Mouth) 

Another common abnormality of incisor wear is a tilted or slanted incisor occlusal surface, i.e. “slope mouth”, “slant mouth” or “diagonal bite”. This defect is occasionally associated with a major unilateral abnormality of the CT that has caused a pronounced unilateral chewing action, which causes uneven wear of the incisors. Developmental abnormalities of the facial bones, including of the hard palate or nasal/premaxillary bones (“wry nose”) or some other craniofacial abnormality, is the usual cause of this incisor defect and its correction by floating incisors is of no value.

To remove incisor overgrowths, it is best to sedate the horse and use a plastic pipe-like gag in the inter-mandibular space (the metal Swale’s gag can cause CT fractures). Focal incisor overgrowths (e.g. opposite a broken tooth, should be removed (in stages, e.g 3-4 mm, if tall) with a solid carbide blade or a power instruments and the incisor alignment assessed again. The practice of arbitrarily reducing the height of the incisor, sometimes very extensively, to purportedly allow the CT to develop better occlusal contact (“incisor bite alignment techniques”) has no scientific or clinical merit and can cause pulpar damage and should not be performed. 

Canine Teeth (“Tushes”) 

The canine teeth (absent or rudimentary in female horses) do not anatomically oppose each other, and this reason is given to explain why calculus, often extensive, can accumulate, especially on the lower canines. Extensive calculus formation at this site may cause localised periodontal disease and ulcers of the adjacent lips. This calculus can be readily removed with strong forceps and the affected teeth can be brushed by the owners. Occasionally, displaced or grossly enlarged canine teeth will interfere with the bit and such teeth should be partly reduced or very rarely (due to the great length of unerupted crown - up to 7.5 cm long) extracted. EOTRH, as noted above, is resorptive disorder of incisor and canine teeth, similar to the feline resorptive disorder/

The sharp tip of the clinical crown of the canine teeth is rasped off by some operators, to allegedly prevent these teeth from causing lacerations of the operator’s hands during dental procedures and to allegedly prevent them interfering with the bit. This can cause pulpar exposure in some horses and there is no scientific basis for this procedure. 

Wolf teeth (Triadan 05, PM 1) are blamed for many behavioural problems in horses and for interfering with the bit, and therefore, these teeth are frequently extracted. Wolf teeth usually occur in the maxilla and lie in front of the 106/206. It is anatomically difficult to envisage how, if of normal small size, these teeth could interfere with the bit, in contrast to mandibular wolf teeth that can readily interfere with the bit. Some veterinarians use the argument that

Displaced, enlarged or partially erupted maxillary wolf teeth may cause bitting problems. They are usually small (1-2 cm long) and can be readily extracted under sedation and local anaesthesia adjacent to the tooth (or infraorbital or mental blocks if very large) utilising a variety of specialised elevators and possibly then forceps. The greater palatine artery can be lacerated during wolf tooth extraction, and oral infections and tetanus can also develop after such extractions. 

Retained Deciduous cheek  Teeth 

Retention of the remnants of the deciduous cheek teeth (CT) ("caps") can occur in horses between 2 - 5 years of age. When very loose or just partially retained by gingival attachments, they may cause oral pain, and affected horses may show quidding, playing with the bit, and occasionally, loss of appetite for a couple of days. Such signs in this age group warrant a careful examination of the rostral 3 CT for evidence of loose ‘caps’. If present, loose caps should be removed using specialised “cap” forceps or a long slim elevator.

The prolonged retention of caps has been alleged to cause delayed eruption of and the development of large “eruption cysts” (“3 y.o. or 4 y.o. bumps”) under the apices of the permanent CT. The presence of very enlarged eruption cysts, especially if unilateral, should prompt a thorough oral and if necessary, radiographic examination for the presence of retained deciduous CT. However, the practice of methodically removing “caps” at rigid set ages in horses will result in the premature removal of some deciduous CT and may damage the incompletely developed, underlying permanent tooth. 

Diastema(ta) 1. 

The occlusal surfaces of all 6 CT are normally compressed tightly together and the CT row functions as a single grinding unit. This is achieved by the action of the angled first CT (06), and the last two CT (10, 11) compressing the occlusal aspect of all 6 CT together. Even with age (the CT taper in slightly from crown to apex) the progressively smaller reserve crowns usually remain tightly compressed at the occlusal surface. However, if abnormal spaces) that are termed diastema (plural diastemata), develop between the teeth, clinical problems will occur. These are often 2-5mm wide, commonly narrower at their occlusal aspect – termed valve diastema. In some cases, the diastema is caused by lack of sufficient angulation of the CT, or the CT developing too far apart to provide enough compression of their occlusal surface. In other cases, diastemata will be due to abnormal spaces by displaced CT. 

Food becomes impacted into these abnormal interproximal (interdental) spaces and leads to progressively deeper food impaction and gingival recession followed by deeper secondary periodontal disease. Many horses show severe clinical signs (quidding, even weight loss) when fed hay/haylage and improve greatly when at grass. Secondary sinusitis (oro-maxillary fistula) can also occur. Such a disorder will be recognised by visually or digitally detecting small spaces between the CT, along with food fibres packed deep in the periodontal spaces between the teeth. In longer standing cases, this food pocketing will extend along the sides of affected teeth and can even extend deep into the mandible or into the maxillary sinuses. Diagnosis can be difficult without use of a dental mirror or endoscope. Obtaining 10-150, latero-oblique radiographs with the horse’s mouth open, can be very useful to investigate and prognosticate CT diastemata. 

Food becomes impacted into these abnormal interproximal (interdental) spaces and leads to progressively deeper food impaction and gingival recession followed by deeper secondary periodontal disease. Many horses show severe clinical signs (quidding, even weight loss) when fed hay/haylage and improve greatly when at grass. Secondary sinusitis (oro-maxillary fistula) can also occur. Such a disorder will be recognised by visually or digitally detecting small spaces between the CT, along with food fibres packed deep in the periodontal spaces between the teeth. In longer standing cases, this food pocketing will extend along the sides of affected teeth and can even extend deep into the mandible or into the maxillary sinuses. Diagnosis can be difficult without use of a dental mirror or endoscope. Obtaining 10-150, latero-oblique radiographs with the horse’s mouth open, can be very useful to investigate and prognosticate CT diastemata. 

Food becomes impacted into these abnormal interproximal (interdental) spaces and leads to progressively deeper food impaction and gingival recession followed by deeper secondary periodontal disease. Many horses show severe clinical signs (quidding, even weight loss) when fed hay/haylage and improve greatly when at grass. Secondary sinusitis (oro-maxillary fistula) can also occur. Such a disorder will be recognised by visually or digitally detecting small spaces between the CT, along with food fibres packed deep in the periodontal spaces between the teeth. In longer standing cases, this food pocketing will extend along the sides of affected teeth and can even extend deep into the mandible or into the maxillary sinuses. Diagnosis can be difficult without use of a dental mirror or endoscope. Obtaining 10-150, latero-oblique radiographs with the horse’s mouth open, can be very useful to investigate and prognosticate CT diastemata. 

Food becomes impacted into these abnormal interproximal (interdental) spaces and leads to progressively deeper food impaction and gingival recession followed by deeper secondary periodontal disease. Many horses show severe clinical signs (quidding, even weight loss) when fed hay/haylage and improve greatly when at grass. Secondary sinusitis (oro-maxillary fistula) can also occur. Such a disorder will be recognised by visually or digitally detecting small spaces between the CT, along with food fibres packed deep in the periodontal spaces between the teeth. In longer standing cases, this food pocketing will extend along the sides of affected teeth and can even extend deep into the mandible or into the maxillary sinuses. Diagnosis can be difficult without use of a dental mirror or endoscope. Obtaining 10-150, latero-oblique radiographs with the horse’s mouth open, can be very useful to investigate and prognosticate CT diastemata. 

Diastema(ta) 1. 

The occlusal surfaces of all 6 CT are normally compressed tightly together and the CT row functions as a single grinding unit. This is achieved by the action of the angled first CT (06), and the last two CT (10, 11) compressing the occlusal aspect of all 6 CT together. Even with age (the CT taper in slightly from crown to apex) the progressively smaller reserve crowns usually remain tightly compressed at the occlusal surface. However, if abnormal spaces) that are termed diastema (plural diastemata), develop between the teeth, clinical problems will occur. These are often 2-5mm wide, commonly narrower at their occlusal aspect – termed valve diastema. In some cases, the diastema is caused by lack of sufficient angulation of the CT, or the CT developing too far apart to provide enough compression of their occlusal surface. In other cases, diastemata will be due to abnormal spaces by displaced CT. 

Treatment of diastemata can be problematic. Food should always be removed from diastemata and this gives temporary clinical relief. In younger horses with mild diastemata,the abnormal spaces may close with further dental eruption, provided there is sufficient angulation of the teeth. Feeding only a finely chopped (milled) forage diet e.g. grass or alfalfa cubes often reduces or removes clinical signs also. Abnormal transverse overgrowths may develop on the teeth opposite diastemata, which may widen the diastemata and selectively force food into them. These overgrowths should always be removed. If marked diastemata are present, widening of the diastema may result in complete cessation of quidding, as food will not become trapped in a larger space. Filling the diastemata with plastic materials can be of value, especially for less severe cases. Some young horses with severe, widespread diastemata will be very difficult to treat – and if radiographs show insufficient angulation of the CT the problem will remain as the horse ages.

Rostral positioning of the maxillary CT row 

Rostral positioning of the maxillary CT relative to their mandibular counterparts, invariably occurs in conjunction with incisor overjet and eventually leads to the development of focal overgrowths on the rostral aspect of 106& 206 that may cut the cheeks and interfere with the bit. If small ( eg <5mm high), they can be rasped level at one treatment, but if large reduction should be performed in stages of say 3-4 mm, a few months apart

Similar overgrowths on the caudal aspect of 311 & 411 frequently go undetected and such overgrowths can lacerate the adjacent oral mucosa and are best reduced with power instruments. “Molar cutters” and percussion guillotines (that encircle this caudal hook) to remove large 311/411 overgrowths risks fracturing the teeth – leading to pulpar infection and should never be used. Such dental fracture and pulp exposure can lead to widespread cellulitis. 

Cheek Teeth Displacements 

Two different causes of CT displacements can occur in horses. In the most severe cases, medial (lingual/palatal) or lateral (buccal) displacements is developmental, possibly due to overcrowding of the dental rows during eruption – or to displaced dental buds, and this type of displacement is often bilateral. Rotation of the displaced tooth can also be present. Gross dental overgrowths then develop on areas of the displaced tooth and their occlusal counterparts, which are not in contact. Displaced CT usually have diastemata between them and adjacent CT that will cause periodontal disease and possibly quidding. Abnormally protruding areas of displaced CT and secondary overgrowths can lacerate the oral soft tissues and cause oral pain. Acquired CT displacements (usually of the caudal mandibular CT) can develop in older horses and are usually associated with lesser degrees of CT displacement and have limited overgrowths (the latter indicates that the displacements were recent). Smaller abnormal (lateral or medial) protrusions of teeth or overgrowths can be removed with a rasp but larger areas will require a motorised tool for removal. Because food pocketing is invariably present, the diastemata will need to be widened or eventually, the displaced tooth may have to be extracted. 

Supernumerary CT 

Supernumerary CT (i.e. presence of more than 6 CT in a row) most commonly develop at the caudal aspect of the CT rows (especially maxillary). Because of their irregular shape and overcrowding, periodontal food pocketing occurs between them and the normal caudal cheek tooth (upper 11s), with resultant pain. Additionally, if unopposed supernumerary teeth will later form large overgrowths. In some cases, supernumerary CT should be extracted (per os always if possible), in others removal of overgrowths is all that is required. Developmentally reduced numbers of CT (ologiodontia) is rare in horses and may be associated with enamel defects. 

Maleruption of CT 

Some cases of “stepmouth” and “wavemouth” are caused by delayed eruption of the permanent CT in either the maxillary or mandibular rows. This can then cause an overgrowth of the opposite cheek tooth that may remain for life and even initiate further abnormalities of wear such as “wavemouth and “stepmouth”. Recognising and removing such overgrowths at an early stage is the key to their treatment. 

Because of their prolonged eruption (for circa 20-25 years), any areas of equine teeth that are not in full occlusion with the opposing teeth will continue to erupt and eventually develop overgrowths. The horse has evolved over 55 million years to eat a coarse forage diet, spending up to 18 hours per day intermittently grazing coarse forage such as grass or hay, during which it moves it mandible maximally in both lateral directions. Domestication has greatly altered the equine diet with many horses being fed large quantities of concentrates and consequently eating much less forage. Feeding concentrates also greatly alters the masticatory action of horses, causing them to chew with a more vertical than lateral mandibular action. This restricted lateral movement predisposes horses to develop enamel overgrowths of the CT. 

The equine maxillary CT rows are about 23% further apart than their mandibular counterparts (termed anisognathia) with both upper and lower occlusal surfaces sloping ventrally at circa 10-30 degrees in the buccal direction (laterally). This absence of complete occlusal contact between the upper and lower CT, is a further predisposition to the development of enamel growths or “enamel points” which develop laterally (bucally) on the maxillary, and medially (lingually) on the mandibular CT. A major role in equine dental care is to prevent these overgrowths from developing by their early detection by routine oral examinations and effective teeth rasping. If these painful enamel overgrowths are neglected, the sharp enamel points will eventually merge into a steeply angulated (e.g >45o) occlusal surface termed “shearmouth” or “scissor mouth”. A mechanical obstruction may now additionally obstruct the normal side-to-side jaw movements, and mastication will be even less effective. Some cases develop an uneven or undulating occlusal surface, termed "wavemouth. Deep periodontal disease (or other disorders) can lead to tooth loss, especially in older horses with short reserve crowns. Following tooth loss, the opposing tooth will erupt more rapidly, leading to the dental irregularity termed "stepmouth". In many horses, a combination of enamel overgrowths, “shearmouth,” “wavemouth” and “stepmouth” will occur together. 

affected animals may not be able to fully clear their mouth of food. Semi-permanent “hamster-like” cheek swellings may occur due to the accumulation of fibrous food wedges between the lateral aspects of the CT and the cheeks. In the presence of oral pain, some horses may also chew very slowly, make soft slurping sounds when chewing forage (rather than the normal vigorous crunching sounds). Some affected horses may permanently use one side of their mouth for chewing rather than using alternative sides, or they may hold their head in an abnormal position during chewing. 

Affected horses may readily eat grass or mashes but are reluctant to eat hay. Decreased food intake and possibly inefficient food digestion and utilisation may eventually occur, sometimes leading to weight loss. Long strands of forage and undigested whole cereal grains may be visible in the faeces. Halitosis may be present if widespread periodontal disease or advanced caries (infection of the mineralised components of teeth) are present. Painful dental-related lesions may also cause bit (bitting) problems, including abnormal head carriage and headshaking during work, because the enamel overgrowths on the upper CT cut the inside of the cheeks due to noseband pressure and the overgrowths on the lower CT may be forced against the tongue by the bit and also cause pain 

Treatment of these abnormalities includes removal of major overgrowths (in stages) using manual or power tools, followed by rasping of treated teeth to smooth out any sharp edges. As unopposed CT may erupt abnormally fast, there is a likelihood that if a large cheek tooth overgrowth (e.g. a 20mm long “stepmouth”) is reduced to the level of the remaining CT, the pulp will be exposed. This is because sufficient secondary dentine may not have developed at that level to occlude the pulp cavity. Very loose teeth can be extracted orally using CT extractors in standing sedated horses. However, all loose teeth do not have to be extracted, especially in older horses, because they may re-attach when overgrowths are reduced. The aim should be to prevent the development of such-end stage disorders by regular (annual or bi-annual) dental inspections and removal of any detected overgrowths, thereby encouraging normal masticatory activity and allowing the free movement of food and saliva around the oral cavity. 

have a (concave – cupped out) occlusal surface termed “senile excavation.” Such abnormal wear is caused by absence of the enamel folds, due to wearing out of the infundibular enamel (in upper CT) and of the peripheral enamel infolding (in both upper and lower CT) that normally prevents such excessive wear of the dentine. Smooth mouth, i.e. absence of enamel on the occlusal surface of CT is common in older horses, however many others lose their CT from secondary periodontal disease prior to this stage. Teeth without enamel are ineffective at grinding forage. Later, the individual roots will become exposed and will display the characteristic hypercementosis of aged equine teeth. 

Unlike brachydont animals (e.g. humans and dogs), primary periodontal disease is not a significant problem in the horse. During eruption of the permanent dentition, a transient inflammation of the periodontal membrane occurs in many horses. Due to the prolonged eruption and continuous development of new periodontal fibres in the horse, equine periodontal disease is not necessarily irreversible, as is usually the case with brachydont dentition. Many horses will have some periodontal disease of their canine teeth due to calculus. Most clinically significant periodontal disease in the horse occurs secondary to diastema or malocclusions as described above. 

A long straight handled rasp is initially used on the caudal CT. As noted, solid carbide blades in these handles should be fitted to cut in a rostral direction (“on the pull”). Care should be taken not to traumatise the vertical ramus of the mandible or the soft tissue protrusion that normally lies caudal to 311 or 411. One hand (the right hand in a right-handed operator) should be on the rasp handle to move it in a caudo-rostral direction (lightly at first), whilst the fingers of the other hand should be placed on, or close to the back of the blade, both to control the exact position and angle of the blade and also to apply additional lateral pressure on the blade. The blade should initially be at an angle of approximately 450 degrees to the medial aspect of the occlusal surface of the tooth to remove any enamel overgrowths. However this 450 angulation should not be rigidly maintained throughout the rasping procedure, the fingers within the oral cavity should intermittently be used to check the progress of the rasping procedure. The occlusal surface of the tooth should not be rasped, for the previously noted reasons.

The rostral mandibular CT can then be rasped, using the long-handled straight rasp if necessary, but more readily using a short-handled straight rasp. If a solid carbide blade is used, it should be fitted to cut in a caudal direction (“on the push”). Having removed all enamel overgrowths, some operators now like to lightly re-float the entire border of the lingual (medial) border of the mandibular CT with a fine gritted “S” float.

Some horses tend to develop relative overgrowths of the first mandibular CT (306, 406) with inexplicable excessive wear of their (larger) occlusal maxillary counterparts (106, 206). It is worthwhile in such cases to reduce the height and slightly round off the rostral aspect of 306 and 406. This can be performed during routine floating using carbide chip blades (with difficulty) or solid carbide blades more readily. However, these teeth can most effectively be reduced using a power instruments. 

Because the lateral aspect of the maxillary CT row is convex, especially rostrally, it is difficult if not impossible to rasp lateral (buccal) overgrowths of these teeth using straight handled rasps. Consequently, a rasp with an angled head or alternatively one with an offset head is required to rasp the 06s and 07s, which is an important area because it is a potential site of contact with the cheeks due to pressure from a nose band. The rasp blade is again initially maintained at an angle of approximately 45 degrees during the maxillary CT rasping, with this angle varied latterly to round off the buccal edges of the teeth.

The 08s-10s can readily be floated using straight handled rasp, but alternatively, a long handled, angled or offset rasp can be used to rasp these teeth. Because of the marked dorsal curvature of the caudal maxillary occlusal surface (“Curve of Spee”) in some horses and the convex nature of the upper CT rows, it is not possible to rasp the caudal maxillary CT using a straight handled rasp. Consequently, a long handled rasp with an obtusely angled head is required. Alternatively, a long handled “S” float can be used to rasp these areas.

Following completion of floating of the maxillary CT, the maxillary CT are carefully palpated and visually examined to assess if any further sharp areas remain. Remaining focal overgrowths if present, can be rasped with the gag still in situ and the teeth palpated again, to ensure that all sharp areas have been removed. At this stage, some operators like to lightly re- float the entire lateral surface of the maxillary CT with an S float.

Additional dental procedures in horses that are ridden and particularly in performance horses, such as dressage horses or show jumpers can include slightly rounding off the rostral aspects of the crown of the 1st upper and lower CT - termed creating “bit seats”. 

In addition to the more common swellings caused by the developing permanent CT (eruption cysts, “3 and 4 y.o. bumps”) or apical infections, swellings of the maxillary and more so of the mandibular bones can also be caused by external trauma (usually due to kicks) and less commonly by tumours. In the young horse traumatic mandibular fractures will inevitably cause some damage to the CT reserve crowns which occupy much of this bone. In most cases conservative therapy (1-2 weeks antibiotics and feeding a soft diet) will be adequate, with the undamaged hemimandible acting as an effective splint. Even if external sinus tracts do develop, it is worthwhile persevering with conservative therapy, until radiographic changes (using a metallic probe in any sinus tract) confirm the presence of definitive dental infection. Extraction should be delayed for some months to minimise the chances of causing a displaced fracture of the mandible. 

to the mandibular interdental space (bars of mouth) and of lips and gingiva can occur due to very excessive bit pressure. A superficial periostitis or sequestration of the mandibular cortex may occur but pathological fractures of the mandible and also widespread bone infection can also occur. 

IDIOPATHIC FRACTURES OF THE CT 

Most CT fractures occur in the absence of known trauma. These usually affect the maxillary CT and the most common pattern is a lateral slab fracture through the two lateral (pulp chambers 1 and 2) pulp cavities (07s-10s CT have 5 pulps). The fracture space becomes filled with food, thus laterally displacing the smaller portion which may cause buccal lacerations. Removal of the smaller loose fragment with forceps will usually resolve the problem in the short term but infection of the apex will later occur in a minority of CT. Midline (sagittal) fractures of the maxillary CT are also common and usually secondary to advanced infundibular caries (hence should not be termed idiopathic fractures!). Deep- seated infections of the alveolus and sinus frequently accompany these fractures in younger horses. Complete extraction of the affected tooth and sinus lavage are required if sinusitis is present. Extraction of loose or very displaced fracture fragments is usually sufficient if apical infection is not evident. Other fracture patterns through pulp horns less commonly occur. 

ORAL TUMOURS 

Dental tumours can include non-calcified epithelial tumours (which are derived from the epithelium that forms enamel) which are termed ameloblastomas. Dental tumours also include a wide variety of calcified tumours from dentinal tissues (odontoma) or cement (cementoma) or combinations of all three dental components (compound odontoma or ameloblastic odontoma.) Squamous cell carcinomas and other soft tissue oral tumours can also occur and usually present as slowly growing, hard focal mandibular or maxillary masses that are usually very radiodense. The prognosis depends on their size and how well defined they are to allow surgical excision. 

Tetanus prophylaxis 

During many equine dental procedures, soft tissue trauma and subsequent oral bleeding may occur - tetanus prophylaxis is indicated with all dental treatments. 

PERIAPICAL INFECTIONS OF THE CT 

Apical infections in CT are often caused by blood or lymphatic borne infections (anachoresis) and inflammation of the pulp due to dental impaction may predispose to such infections. In upper CT infection may be due to food accumulation and fermentation deep in cemental defects in the two infundibulum (infundibular caries) leading to infection of the pulp (or sagittal fractures as noted earlier). Infection can also occur due to deep periodontal disease or hairline or idiopathic fractures.

Periapical abscessation of the lower CT commonly involves the rostral CT within 1-2 years of eruption and may occur when there are eruption cysts (“3 and 4 year old bumps”). In the early stages (<3 months), the infection usually remains confined to the apex, adjacent to the sinus tract and all the pulp cavities remain vital. At this early stage antibiotic treatment (e.g. 2 -3 weeks of trimethoprim/sulphonmide) may suffice. Later endodontic (root canal) therapy or more usually dental extraction will be required. 

Because many apical infections occur in younger horses which have long reserve crowns, the infection cannot drain into the oral cavity, but will affect the supporting bones and commonly drain from the apical aspect of the tooth. Mandibular apical infections are inevitably accompanied by unilateral mandibular swellings that will often develop external draining tracts. Infections of the upper 06s and 07s (occasionally the 08s) will cause focal swellings of the rostral maxilla, which are almost pathognomonic for dental infections. In some cases, an external sinus tract will develop; less commonly a tract will drain into the nasal cavity. Infections of the caudal 4 maxillary CT generally results in a secondary sinusitis, with the presence of a chronic, malodorous unilateral nasal discharge.

A thorough clinical (including intra-oral examination with a mouth gag, including for the presence of fractures or pulpar exposure) and radiographic evaluation of the dental apices (latero-oblique projections) should always be undertaken first to absolutely confirm that a tooth needs to be extracted and then to confirm which tooth is diseased. The interpretation of equine dental radiographs is often difficult. In some cases, scintigraphy or Computed Tomography may provide conclusive evidence of apical infection. If an external sinus track is present, e.g. as occurs with many mandibular or rostral (1st – 3rd) maxillary CT infections, it is essential to obtain radiographs with a metallic probe in situ, to define the infected area of the tooth. This procedure will also provide surgical landmarks, if the infected tooth is to be extracted by repulsion. 

Extraction of the long crowned (hypsodont) equine CT is a major surgical procedure with many possible immediate and delayed sequel. If any doubt remains concerning whether a cheek tooth is infected or not, conservative treatment and not extraction should be undertaken, including antibiotic therapy for suspect mandibular or rostral (06-08) maxillary apical infections and maxillary sinus lavage and antibiotic therapy for suspect caudal (09-11) maxillary CT apical infections. Failure to respond to the above conservative therapy should prompt a further clinical and radiographic evaluation for dental infection. Only when definite evidence of dental infection is present should dental extraction be performed. 

Repulsion 

The traditional method for extracting equine CT has been by repulsion of the diseased tooth under general anaesthesia. This procedure carries all of the inherent expense and risks of general anaesthesia in the horse and additionally is associated with a high level of postoperative complications because much damage occurs to the alveolar and supporting mandibular or maxillary bones during the repulsion. Some studies have shown that more than 50% of cases of equine dental repulsion will require a second surgery, usually to curette dental fragments or alveolar sequestrae from non-healing alveoli. 

Lateral Buccotomy Technique 

In this technique, a lateral surgical approach is made directly through the skin and subcutaneous tissues into the alveolus, with horse under general anaesthesia. This technique requires GA and carries risks of much haemorrhage, facial paralysis and parotid fistulation.

Oral Extraction of CT

This technique has the great advantage of being performed in the standing horse, removing the expense and risk of general anaesthesia. Additionally it does not require surgery of the supporting bones and consequently, post-operative complications are relatively rare. The current availability of safe and effective sedatives and analgesics has been a major reason for the revival of the oral extraction technique. Additionally, local anaesthesia of the mandibular, maxillary or infraorbital nerves can also be used and the horse should be restrained in stocks. 

A number of workers have also attempted to treat infected CT by use of endodontics (root canal therapy). A major advantage of endodontics, if this treatment is successful, is that the infected tooth is preserved and thus will then continue to erupt normally (at circa 2- 3mm/year). This prevents the development of overgrowths (“stepmouth”) of the opposing cheek tooth and also “drifting” of the adjacent CT into the site of the extracted tooth. This latter “drifting” will eventually cause overgrowths (“hooks”) on the caudal and rostral aspect of the opposing CT row.

Endodontic treatment can be performed through the apex of the tooth, i.e. via surgical approaches through the mandibular or maxillary bones or via the occlusal aspects of the pulps – but has shown poor success, whilst approaches through the occlusal surface is more encouraging..