BEVA Dentistry CD - Legends
Slides 2- 4: The evolution of the horse began in Central / South America some 55 million years ago. The precursor of the modern horse was a rabbit-sized animal called Hyracotherium or Dawn Horse. It lived on soft leaves that were high in nutritional content and contained minimal abrasive silicates and thus caused little dental wear. Hyracotherium had brachydont (i.e. short crowned teeth) similar to human or canine teeth which were adequate at that stage because of the low levels of dietary wear on its teeth.
Due to great climatic changes in the Americas, much vegetation changed to coarse, cellulose-containing, tundra-type grasses and Hyracotherium gradually evolved to live on this new diet. These evolutionary changes included the development of a large caecum and colon which contained microbes which broke down cellulose (one of the major foodstuffs worldwide, which no mammalian enzyme can digest). This evolutionary development occurred well in advance of ruminant evolution.
Eating this new diet required increased periods of eating because of its lower nutritive content and also because grasses are high in abrasive silicate, great wear occurred on these primitive horses' teeth. Consequently the Dawn horse's teeth evolved to compensate for this high level of wear by becoming long crowned (i.e. hypsodont) with slow eruption over 20-25 years.
Slide 5:
A number of migrations of the horse from the Americas to Asia occurred because at that time Alaska was attached to Russia by the Greenland Bridge. The horse evolved through many stages into breeds such as Zebra and Tapir and also into the modern horse including the Asian wild horse i.e. the Przewalski (pronounced Sha-val-ski). Two major migrations of the modern domesticated horse included one to northwest Europe where they evolved into the Northern European heavy horse, i.e. Coldbloods such as the modern draught horse and native pony breeds. Anther major migration led to the development of a line of lighter horses in the Arabian Peninsula that includes the Arabian ponies and Thoroughbreds, i.e. the Warmbloods.
Slide 6:
The first record of human contact with horses come from cave paintings in Spain and France such as the Lascaux caves, circa 15,000 BC where horses that resemble Asian wild horse were hunted for food. Some of the horses in these cave paintings have spears sticking out of them!
Slide 7:
The first evidence of domestication of the horses was about 6,000 years ago and comes from finding skulls that have abnormal bit wear on their first cheek teeth. The oldest of these skulls have been found around the Black and Caspian Seas.
Slide 8:
When discussing signs of dental disease in the horse - it must be emphasised that many horses will silently suffer severe and painful dental disease without showing any outward signs and consequently dental examination should be performed regularly on all horses.
Slide 9:
Quidding is the dropping out of partially chewed food - that normally occurs just before the oral phase of swallowing. Quidding can be due to lesions such as very sharp overgrowths causing ulceration of the soft tissues (cheeks and tongue) and also in particular to diastema, where food is progressively pushed between abnormal spaces between teeth and then into the sensitive periodontal membranes.
Slide 10:
A useful test to check for the presence of dental disease (including at pre-purchase examinations), is to offer a horse some hay or haylage and to listen to and observe its masticatory behaviour. Normal horses make a vigorous crunching sound when chewing forage (hay, haylage & grass). In contrast, some horses with painful dental disease make minimal or “slurping” sounds when eating. In pre-purchase examinations it is also useful to discreetly look within the horse's box to see if there is any evidence of quidding beneath its hay rack/bag.
Slide 11:
Some horses with painful ulceration of their cheeks have hamster-like pouches of food in their cheeks. Horses may deliberately pack this food here to try to reduce oral pain, by pushing food between the ulcerated cheeks and the sharp teeth.
Slide 12:
If a horse does not chew its food properly it will not break the tough, lignin-like husk on grains. Therefore, their own digestive enzymes and those of micro-flora of their large colon and caecum cannot reach the starch within the grains to digest it and no nourishment is obtained from these whole grains. Likewise, if cellulose in forage (grass, hay or haylage) is not broken down into fine particles there will not be a large enough surface area for the microbes to act on it during the limited time this food is in transit through the large intestine and so dietary nutrients will again be lost.
Slide 13:
Weight loss is just the final stage of severe and chronic dental disease and consequently the absence of weight loss does not preclude the presence of very significant painful dental disease.
Slide 14:
Bitting and head carriage disorders have been largely associated with disorders around the contact area of the bit, bridle and noseband, such as ulcers of the cheeks, or lips, damage to the “bars of the mouth” (dorsal aspect of the mandibular bone), displaced, protruding or fractured wolf teeth or sharp edges on the rostral and rostro-lateral aspects of the upper cheek teeth.
If horses have large dental overgrowths (“steps” or “beaks”) that limit rostro-caudal mandibular movement relative to the upper jaw, they may develop head carriage problems and possibly referred pain to their temporo-mandibular joint, or possibly even signs of neck or back pain (by mechanisms described later - under cheek teeth disorders).
Slide 15:
Examination of teeth: Despite what some of the older text books state, it is not possible to even superficially examine equine cheek teeth without the use of a full mouth gag (speculum). Even with the use of a full mouth gag it is necessary to use a light source and a mirror to detect some abnormalities. Some horses will need sedation to allow a proper dental examination but once they get used to having a gag fitted (e.g. every 6 to 12 months), it is often possible to later perform oral examination and minor dental treatments without sedation.
Slide 16:
The deciduous incisors in the foal erupt at 1 week, 6weeks and at 6-9 months - rule of thumb - 6days, 6 weeks and 6 months.
Slide 17
Ageing horses by examination of their teeth has been shown to be inaccurate, particularly for older horses. Nevertheless a relatively accurate guideline is to assess the eruption of the permanent incisors, with the 01s erupting at 2 years, 02s erupting at 3 years and the 03s erupting at 4 years of age, being in full wear by 6-12 months after those times.
Slide 18:
Examination of the occlusal surface of the erupted incisors is also used to assess age; however it is much less accurate than previously believed. In the recently erupted incisor the infundibulum (a cup-like infolding of enamel) is present and is deep, the tooth is oval on cross-section and there is no secondary dentine (dental star). With time the cups will wear out. The tooth will get worn to where the pulp cavity formerly was - the body seals off the occlusal aspect of the pulp-cavity constantly with secondary dentine and this darker area, i.e. the “dental star” is the site of the previous pulp-cavity. With age the shape of the tooth also changes from oval to round to triangular.
Slide 19:
The incisor features used to age horses can vary between individual horses, for example if the pulp cavity is very close beneath the surface of the recently erupted tooth a dental star will be present for 1 - 2 years prior to the “standard” time. Less commonly the pulp cavity lies deep down the tooth and thus secondary dentine may not appear until a year or so after the expected time.
Likewise if a horse has very shallow infundibula in its incisors - they may wear out within one year of eruption, whereas if it has very deep infundibula, they may still be present for a couple of years after they should have worn away.
Ageing horses by examination of the teeth is inaccurate in horses of 6 or 7 years of age and older. Information gained from such examinations should be regarded as a predictor of age rather than definite evidence of the age of the horse and veterinarians should not definitively age horses on their dentition beyond 6-7 years of age.
Slide 20:
The incisors of a 43 year old pony, show minimal clinical crown, are round in cross section, protrude horizontally and contain large areas of secondary dentine (dental stars).
Slide 21:
The cheek teeth of the horse have a number of other features that differ from the teeth of brachydont species such as humans and dogs - in addition to being long-crowned. Note that the upper (maxillary) rows of cheek teeth are further apart than the lower (mandibular) rows and that the occlusal surface angle is circa 15o - 25o, instead of being horizontal - as are the occlusal surfaces of human teeth.
Slide 22:
Because the upper and lower cheek teeth are not in full contact and because their occlusal surface is angled, if the upper and lower incisors are pushed together and the bottom jaw is slid sideways, eventually the upper and lower cheek teeth occlusal surfaces will come into contact and will then force the incisors to separate.
This incisor examination determines the angulation of the cheek teeth occlusal surface. In some horses the teeth may totally lock and be unable to move sideways on this manoeuvre due to large overgrown teeth.
Slide 23
Overjet means that the upper incisors are protruding in front of (more rostrally than) the lower incisors and this is a common developmental problem in horses. It seldom causes a grazing or ingestion problems. There is evidence that it is an inherited defect.
Slide 24
Overbite indicates that the upper incisors are rostral to and also overly (overlap) the lower incisors and so this disorder is more appropriately termed `Parrot mouth'. Surprisingly these horses are also usually able to ingest properly, being able to use their lips to prehend food.
Slide 25:
The main clinical problems associated with overjet and overbite is that these incisor disorders are caused by a generalised imbalance between the growth of the upper and lower jaws and therefore all the teeth on the upper jaw (incisors and cheek teeth) lie rostral to the opposite teeth on the lower jaw. Therefore in addition to developing poor occlusion of the incisors, there will also be overgrowths on the rostral aspect of the upper 06 cheek teeth and on the caudal aspect of the lower 11 cheek teeth -although the latter overgrowths may not develop until the horse is at least 6-7 years of age.
Slide 26:
Overjet can be corrected by wiring the upper incisors to the first or second cheek teeth. This brace will retard growth of the premaxillary and maxillary bones and allow the bottom jaw to catch up in growth with the upper jaw, so allowing the upper and lower incisors to come into occlusion. A hole is drilled through the cheeks and then a hole is drilled between the first and second deciduous cheek teeth to anchor the wires caudally.
Slide 27:
The wires attached to the upper cheek teeth are wrapped in front of the incisors (with some loops of wire interwoven between incisors) and this tension band retards the growth of the upper jaw.
Slide 28:
If a foal has marked overbite, putting on a tension band prosthesis may just bend the incisors further ventrally and make the overbite worse. In these cases as well as fitting a tension band between the upper incisors and cheek teeth, a “bite plate” composed of aluminium and acrylic is fitted to the hard palate so that the foal can have occlusal contact of its lower incisors on this plate and keep pressure on the upper jaw (and incisors) and help straighten it.
Slide 29:
This shows a foal with overjet before and after having an orthodontic brace fitted and it shows that overjet is almost fully corrected. The cheek teeth overgrowths are also prevented or reduced following orthodontic treatment in some of these foals.
Slide 30:
An overjet present in this foal has been totally corrected by fitting an orthodontic wire brace. It must be noted that some United States breed societies do not allow bracing of parrot mouthed horses - and will not register surgically corrected cases because of the hereditary risks.
Slide 31:
Underjet is the opposite to overjet and indicates that the lower incisors are protruding more rostrally than the upper incisors. This is much less common than overbite and, affected animals can usually ingest their food normally and so weight loss or prehension problems are rare. Cheek teeth overgrowths will also commonly occur
on upper 11s and on lower 6s.
Slide 32:
Deciduous incisors (milk teeth) are normally shed when the permanent incisors erupt at 2 , 3 , 4 years of age, but occasionally they may not be shed normally. For the Triadan system add 4 to the first Triadan number - i.e. tooth 501 is replaced by 101. Deciduous incisors may be retained beyond the normal times of shedding because the permanent tooth erupted behind them (caudally) and so do not help to push the deciduous teeth up to be shed. Such additional incisors must be positively identified to be deciduous remnants (and not supernumerary permanent incisors) and then removed with forceps or if they have deep reserve crown root - by elevating the embedded crown and root fully with dental elevators.
Slide 33 -34:
Removing retained incisors is not always a simple straightforward procedure. These slides show the extraction of a very long, retained deciduous incisor which needed a local nerve block and sedation before the rostral alveolar wall was removed. Following loosening, the 2-inch long retained deciduous incisor was finally extracted.
Slide 35:
Supernumerary incisors are said to occur when there are more than six adult incisors present in any incisor arcade. This disorder must be must be differentiated from the situation when 6 permanent incisors and some retained deciduous incisors are present. Some horses can have up to 6 supernumerary incisors along with six normal incisors i.e. up to 12 permanent incisors in one arcade. Surprisingly, supernumerary incisors do not usually cause much clinical problems. As supernumerary incisors are usually diagnosed in younger horses where very long reserve crowns and roots are present on all incisors, it is difficult to surgically extract them without causing much damage to the remaining incisors and also to the supporting bones. Consequently many veterinarians do not attempt to surgically remove supernumerary incisors - unless one or two are protruding rostrally and can be more readily removed.
Slide 36:
This shows a young horse which has a single supernumerary incisor on the right upper incisor row. The supernumerary incisor has caused overcrowding of the upper incisor arcade and secondary caudal displacement of incisors 101 and 201. It has also caused abnormal spaces, i.e. diastemata (plural of diastema) to develop between 101 and 201 and the adjacent teeth - leading to food packing into these diastemata. In this case extraction of the supernumery tooth is indicated, in addition to cleaning out of the diastemata to try and encourage normal realignment of the two displaced central incisors. The sides of the two displaced teeth could even be trimmed to more readily allow them back into place.
Slide 37:
This image shows a young horse that has been kicked in the incisors and has suffered a fracture of three permanent incisors with pulpar exposure i.e. termed complicated dental fractures. In brachydont species such as humans or dogs, such pulpar exposure will lead to inflammation of the pulp and inevitable loss of the tooth, however this does not necessarily occur in horses, especially younger horses.
Slide 38:
This young horse has a complicated fracture of 103 (right upper corner incisor) and is a good candidate for endodontic (root canal) treatment. Briefly, this consists of progressive removal of the dead pulp until healthy (bleeding) pulp is reached; sealing off the healthy underlying pulp with a calcium salt (calcium hydroxide) and then application of a modern restorative material (filling) on top. Hopefully the restored tooth will continue to erupt and will come into wear eventually.
Slide 39:
A horse with fractured incisors receiving endodontic treatment at Edinburgh University.
Slide 40:
On the left hand side - the pulp on the fractured tooth is still vital -because it is bleeding as the pulp canal is undercut above it. On the right, the healthy pulp has been covered with calcium hydroxide paste and a modern composite restorative filling has been applied.
Slide 41:
This horse has suffered traumatic damage to its upper left incisors in the past. Due to absence of wear, the two opposing (lower) incisors are now developing overgrowths which if ignored, will eventually prevent the upper and lower incisors sliding evenly over each other during chewing and therefore will push the cheek teeth apart and thus affect the horse's ability to masticate its food.
Slide 42:
This horse has long-term, neglected fractures of the incisors with large overgrowths now present on the upper left and the lower right incisors. These large overgrowths prevent the horse from masticating with the left side of its mandible and secondary cheek teeth disorders have occurred as a consequence of this. These very long incisor overgrowths need to be reduced in stages in order to prevent pulpar exposure. The secondary cheek teeth overgrowths will also need to be corrected. (Fig courtesy of Graham Duncanson).
Slide 43:
This horse has small incisor fractures (not complicated - as they do not involve the pulp cavity) associated with crib biting using the side of its mouth.
Slide 44:
This is a more typical incisor disorder (occlusal wear of the 01s and 02s) caused by crib-biting. This horse also has additional wear on the rostral aspect of the incisors due to also rubbing its incisors on fixed objects such as doors and posts.
Slide 45:
This young horse has caries of incisor 201. In general, caries is uncommon in equine teeth, as compared to other species that consume high levels of soluble carbohydrates i.e. children eating a lot of sweets. Occasionally severe (peripheral cemental) caries can occur in horses - sometimes in animals consuming high levels of molasses in their diet. Most caries in equine teeth occurs within the infundibula (cup-like infoldings) of their upper cheek teeth.
Slide 46:
The treatment of a case of incisor caries;
CLOCKWISE :
Removing the diseased enamel using a high speed burr
Acid etching the underlying enamel in order to obtain a good bond with a restorative material
Applying a bonding agent onto the etched enamel
A modern composite filling material has been used to fill the defect.
Slide 47:
“Slope mouth” or “slant mouth”. This wear pattern indicates that the horse has been chewing in just one direction (with one lower jaw) that has caused incisor wear in just one plane. Horses will chew in one direction because of an underlying serious problem (painful or mechanical) with their cheek teeth - consequently such cases should have very careful evaluation and treatment of their cheek teeth before correcting the slant mouth.
Slide 48:
Shows a horse with slant mouth having the incisor overgrowths corrected. If they are very pronounced the overgrowths should be removed in stages in order to prevent the exposure of pulp that would cause great discomfort to the horse and even possible pulpar and apical (root) infection with later loss of the treated incisors.
Slide 49:
In this slide a motorised dental burr and a manual carbide blade are being used to reduce focal incisor overgrowths.
Slide 50:
A rare cause of slant mouth is the presence of wry nose, i.e. where the upper jaw is slightly deviated to one side (congenital disorder) and subsequently there is not full contact between all of the upper and lower incisors and cheek teeth.
Slide 51:
If wry-nose is detected early enough in foals it can be surgically corrected. Some foals also have severe nasal obstruction due to marked deviation of their nasal septum and would also need extensive nasal surgery, including controlled fracturing of bones and insertion of bone grafts in order to have a relatively normal life. If foals are severely affected, surgery may not be fully successful and so it may not be ethical to attempt surgical correction.
Slide 52:
Normally there are no spaces between the occlusal surfaces of the adjacent incisors and all six incisors act a single unit. With age - because the incisors taper inwards towards their apices, some incisors will develop slight gaps between each other on the occlusal surface. These spaces can lead to the trapping of food lower down between the teeth and also into the gingival and periodontal spaces. Eventually some horses will develop a large mat of fibrous food in front of and behind the incisors. The owners may get bitten when trying to remove the fibrous mass behind the incisors - within the oral cavity.
Slide 53:
Incisor diastema can be treated by either using a diamond wheel - which can be dangerous to veterinarian, client and horse - thus a high level of health and safety guidelines are required for its use. Simply using a hardened saw blade to open up the space on the occlusal surface is a simpler and safer alternative. Note on the figure on the left that the chronic food impaction (caused by the incisor diastema) has caused gingivitis with irregularities of the gum margins and retraction of the gums.
Slide 54:
Shows the normal canine teeth present in a male horse. Vestigial canine teeth are sometimes present in female horses.
Slide 55:
The most common disorder of canine teeth is the development of calculus (tartar) on the lower canine teeth - for reasons that are not fully clear. The upper and lower canines do not normally contact each other and perhaps the absence of masticatory movement of food around these teeth allows a soft plaque, and later calculus to develop. This calculus can be broken off with forceps and the teeth smoothed down (buffed) with a fine file to help prevent further deposition of calculus on the tooth. Some competition horses have their canine teeth filed down (reduced) somewhat and rounded off - some operators suggest that this allows a better examination of the oral cavity without risk of damaging their hand.
Slide 56:
Canine teeth will occasionally become damaged and need to be extracted. This image shows a horse with short and darkened upper and lower canine teeth that were believed to be have been damaged by trauma. The reserve crowns and roots of canine teeth are up to 7.5 cm long - running vertically for about 2-3 cm and then horizontally into the jaws for the remainder. Consequently, great care must be taken when removing canine teeth and extraction should only be performed following radiography, to outline the size and precise site of the unerupted part of the canine tooth.
Slide 57:
Wolf teeth i.e. the vestigial first pre-molar (Triadan 05s) are present in a proportion of adults. It is believed that many (most) wolf teeth are lost when the first permanent cheek teeth erupt. There is much debate whether wolf teeth cause bitting problems - but some people adapt the attitude that “they never do any good and so they should always be removed”!
It is of relief however to note that “Wolf Teeth (105) are not a cause of blindness (Merrilat 1906)”
Slide 58:
Lower wolf teeth are uncommon, but are likely to cause a bitting problem as they lie where the bit normally sits on the bars of the mouth. Ulceration of the bars of mouth can occur in front and behind such wolf teeth. It is generally accepted that lower wolf teeth should always be extracted.
Slide 59:
Upper wolf teeth that are very large or displaced and that contact the cheeks or the lips may cause bitting problems and are also commonly removed. Wolf teeth that are unerupted (“blind”) and have inflammation of the surrounding gingiva can also
rationally be extracted. This image shows a rostro-laterally displaced, large, sharp wolf tooth. Note the normal canine tooth is just erupting in this young horse.
Slide 60:
In this figure the wolf teeth seen above is outlined through the cheeks - at this site the cheeks can be pressed on to the sharp displaced wolf tooth by the bridle.
Slide 61:
Shows two alternative techniques for desensitising wolf teeth prior to their extraction in sedated horses - local anaesthetic injected around the tooth and into periodontal space or alternatively, an infra-orbital nerve block
Slide 62:
Shows a Burgess wolf tooth extractor being used to cut the gingiva around a large, rostrally displaced wolf tooth.
Slide 63:
A Musgrave-type extractor is being used to fully extract two smaller wolf teeth in another horse.
Slide 64:
Shows a fractured wolf tooth that is protruding above the alveolar level - with inflamed gingiva surrounding it. An unqualified person previously tried to extract this wolf tooth and has fractured it. Such fractured wolf teeth often cause more problems than were present (if present at all) prior to the attempted “botched” extraction. The bottom right hand image shows the empty alveolus following elevation and complete removal of the fractured tooth.
Slide 65:
A number of serious cheek disorders can occur during the development and eruption of the cheek teeth - which erupt at circa 2 , 3, 4,1, 2 and 3 years of age respectively, for the first to the sixth cheek teeth (Triadan 06s to Triadan 11s).
Slide 66:
The deciduous cheek teeth remnants (termed “caps”) are normally shed at 2 , 3 and 4 years of age for the 06s, 07s and 08s, cheek teeth respectively. In some horses, “caps” may be shed many months prior to or after the above “standard times”. If loose and especially if partially attached by gingiva, a cap can cause great discomfort to the horse, inducing sudden onset, usually short term, bitting and quidding problems. If a cap is loose or if there is a very clear demarcation between the cap and the underlying permanent tooth - it should then be removed.
Slide 67:
Cap extraction is performed using specialised cap extractors (left image) .The image on the right shows a thin cap that has been extracted. This cap has a large spike-like root that was mobile deep in the gingiva and was causing great discomfort to the horse.
Slide 68:
Elephants normally have just one large cheek tooth in wear on each side of their jaw. Each tooth lasts for about 10 years and these teeth are replaced on about 7 occasions. This figure shows two cheek tooth (ventrally on figure) which are coming to the end of their life and are being replaced by erupting new cheek teeth above it. There are no spaces in these big, single, solid teeth to trap food - hence the title slide, “Elephants don't get diastema”.
Slide 69:
In the normal horse - the six cheek teeth in any one row should act together like a single elephant tooth. The first cheek tooth is slightly angled caudally while the fifth and sixth are angled rostrally and so as they grow, they compress the six cheek teeth between them to act as a single functioning unit, with no spaces present between them on the occlusal surface that could allow food entrapment.
Slide 70:
If spaces occur between the cheek teeth, the constant (up to 18 hours a day) high pressure grinding of fibrous food will eventually trap some food fibres lengthways between the teeth. Food will eventually get pushed down into periodontal spaces and may even get pushed 5cm or more down the side of the tooth. As it is pushed into the periodontal space it will irritate and damage the very sensitive periodontal membrane causing great pain. Diastema between cheek teeth is a common, very painful but under-diagnosed dental disorder of horses - the teeth must be examined carefully to detect this disorder.
Slide 71:
Diastemata can be diagnosed by special radiographic projections with the mouth open. These x-rays can demonstrate the presence of, the size and shape of any diastemata that are present. It can also show the angles of the cheek teeth and so help predict the long term chances of resolution (or not) of this problem.
Slide 72:
A diastema is present between two upper cheek teeth (106 & 107). This is an uncommon site for diastemata - most CT diastemata occur between the lower cheek teeth, particularly between the caudal lower cheek teeth (9s - 11s).
Slide 73:
An x-ray of a mandible of a young horse which has very wide diastemata between every cheek tooth. There are reasonable angles on these teeth and so it appears that the dental buds developed too far apart. This disorder was also present in other cheek teeth. Because of very severe and constant pain from periodontal disease and a poor prognosis, this horse was subsequently destroyed on humane grounds. The post mortem photograph shows extensive food packing between all of the cheek teeth.
Slide 74:
As well as causing pain during mastication, on some occasions food can migrate deeply down the periodontal space within the teeth. In this older horse, food has migrated between two cheek teeth and entered the sinus (oro-maxillary fistula) causing a very serious sinus infection. In the smaller photograph a metal probe has been inserted into the sinus whilst the clinician looks into the oral cavity to try and find the diastema that caused this serious problem.
Slide 75:
Treatment of diastema(ta). In the short term, putting horses on short grass will help greatly - as the softer, smaller grass fibres are not so easily trapped in the periodontal space. Horses can also be fed alfalfa or grass cubes or very fine geriatric horse diets (chopped hay or haylage) - the fibres are so short in these foodstuffs that very little food trapping occurs. However these diets are expensive and as horses do not chew properly when on such diets (see later slides) they will need to have their teeth rasped every 3-4 months when fed high levels of such chopped diets.
The area of a tooth opposite a larger diastema will not be worn normally and will progressively develop an overgrowth - very often like a transverse ridge. These overgrowths can now further widen a diastema and also selectively push food into it - causing greater pain. Overgrowths opposite diastemata should always be reduced.
Slide 76:
Food can be temporarily removed from between the teeth and the periodontal space using water picks or modern high pressure compressed air dental picks. However, unless the underlying cheek teeth problem is addressed, food will soon become entrapped in these spaces again and the painful disease will recur.
Slide 77:
Currently the best treatment for cheek teeth diastemata is to use specialised burrs to widen the diastema on the occlusal surface to circa 6-8mm wide. This procedure must be performed with great care in younger horses as the pulp cavity is very close to the side of the tooth, especially the caudal aspect of the tooth. Damage to the pulp (pulpar exposure or thermal insult - from overheating with a burr) can cause an apical infection leading to mandibular and maxillary abscesses and sinusitis.
Slide 78:
This image shows a widened diastema with still some food trapped deeper between the teeth and the gingiva - indicating that deeper widening of the diastema is needed. There is also an x-ray of mandibular cheek teeth that have had diastemata widened to prevent food trapping. At the bottom right is a photograph of the oral cavity of a horse using a dental mirror showing a diastema that has been widened using a dental burr.
Slide 79:
As previously noted in the incisor section, horses that have disparity between the lengths of their maxillary and mandibular bones have parrot mouth and also rostral and caudal cheek teeth overgrowths.
Slide 80:
This figure shows a horse with long-term, neglected overgrowths of the upper 1st cheek teeth (06s). The cheek teeth normally erupt at about 1 inch (2 cm) every ten years and therefore these 4 cm long overgrowths would indicate neglected dental care for over ten years. These large 06 overgrowths should be reduced in stages in order to prevent pulp exposure.
Whilst these rostral overgrowths are very obvious it is essential that the caudal aspect of the lower cheek teeth rows are also examined as overgrowths are also likely to be found at that site.
Slide 81:
Shows large rostral 06 overgrowths being reduced using motorised instrument. These large overgrowths should be reduced in 2- 3 stages, removing circa 1cm of overgrowth at a time and so stimulating the underlying pulp to seal itself off with secondary dentine.
Slide 82:
Shows a horse with a focal very sharp “beak-like” overgrowth of its upper 06s. The shallow overgrowth on 206 (not involving any pulps) has been removed and 106 is about to be reduced.
Not surprisingly horses with these types of overgrowths often have very severe bitting and behavioural problems. When a horse flexes its neck, such as when it is ridden in collection, the mandible normally slides forward along the upper jaw. However, if large overgrowths are present on the first upper cheek teeth this will physically prevent the mandible from moving rostrally. Consequently horses may open their mouth when their head is pulled into collection in order to allow their mandible to come forward. This response (opening mouth during competitions - possibly losing points) is then counteracted by strapping the mouth closed and forcing the horse to ride in collection with a mandible trapped against the upper 06 overgrowths. This abnormal mandible- maxilla confirmation can potentially induce pain in the temporo-mandibular joints and possibly also cause referred neck and back pain.
Slide 83:
These are two examples of caudal lower 11 overgrowths - which commonly occur along with upper 06 overgrowths - but because of their inaccessibility they are often not diagnosed or not treated properly. Caudal lower 11 overgrowths are usually not as tall as 06 overgrowths and often develop later. These lower 11 overgrowths should be reduced - bearing in mind the normal curve of Spee (upward curvature of the caudal cheek teeth occlusal surfaces - especially in small light pony breeds). The normal angulation of the mandibular cheek teeth occlusal surface should be maintained when reducing these teeth.
Slide 84:
Cheek teeth displacements can occur during the eruption of cheek teeth and these developmental displacements are usually the more severe types of dental displacement. Older horses that previously had normal alignment of the teeth can sometimes develop acquired displacement of the teeth - that are usually less severe.
Slide 85:
Shows a mandible with very severe developmental displacements of the 310 and 409 teeth - that developed during the eruption of these two CT, at two years and one year of age, respectively.
Slide 86:
A close up of a displaced cheek tooth showing deep ulceration into the cheeks. This horse had a history of being “difficult to ride” for many years having a “hard mouth” and was eventually “managed” with a very severe bit. This horse had regular “dental treatment” by an unqualified lay dental technician. The fact that such a painful disorder was never detected and the horse was subsequently controlled using a severe bitting technique represents a very serious welfare issue.
Slide 87:
This shows a common developmental cheek teeth displacement in mature horses -with a slight medial displacement of the lower 10s and 11s. The displacement has created a space between the displaced and normally aligned teeth with a diastema developing at this site (between 309 and 310).
Slide 88:
Shows a long-term neglected mouth with displaced teeth, including one that is almost lying sideways across the hard palate. In addition to the sharp overgrowths causing ulcers of the cheek and tongue, the usual development of diastemata beside the displaced teeth also causes pain.
Slide 89:
Problems caused by and treatment of cheek teeth displacements.
Slide 90:
Shows a mandible with supernumerary cheek teeth. Seven cheek teeth are present in each mandible. The extra teeth overcrowd the normal teeth, leading to abnormal spacing between the supernumerary and the adjacent teeth and thus painful periodontal food pocketing.
Slide 91:
X-ray of a hemimandible of a horse with 8 permanent cheek teeth. Secondary diastemata and periodontal disease was present.
Slide 92:
Outlines the problems supernumery cheek teeth can cause if they have no opposing tooth, i.e. they will develop an overgrowth. Because supernumerary CT are often overcrowded and misaligned, periodontal disease will also usually occur. Initial treatment should be the removal of overgrowths but if severe periodontal disease develops affected, the supernumerary or adjacent CT may need to be extracted. This can be a very difficult procedure as they usually lie at the caudal aspect of the oral cavity.
Due to the irregularly shaped spaces between these teeth the use of a diastema burr is usually not feasible to treat the periodontal disease present.
Slide 93:
Oligiodonta means absence of normal teeth. With old age horses will inevitably lose some of the cheek teeth - but this is not a true oligodontia - see teeth in old maxilla in figure. If teeth are missing their opposing counterparts will develop large overgrowths - possibly later restricting mandibular movement. Treatment consists of removal of such overgrowths.
Slide 94:
Shows a 3-year-old horse which has had a temporary 708 (3rd CT) “cap” remaining but no permanent CT has developed beneath it. When this “cap” is shed the opposite (upper) tooth will overgrow and form a “step mouth” and the teeth on each side of the vacant alveolus will tend to drift into its space.
Slide 95:
This skull has major overgrowth of two teeth which is termed a “step mouth”, although many such overgrowths are not rectangular in shape. This neglected mouth also has “wavemouth”, diastemata and sharp buccal edges. Because of long term dental neglect this horse would have suffered severe pain when masticating food for many years.
Slide 96:
Repeat of previous slide showing that the equine upper cheek teeth are spaced further apart than the bottom rows and also showing the angulated occlusal surface.
Slide 97:
A transverse section of the skull of a young horse showing the very long, still unerupted permanent cheek teeth that have very large pulp cavities and contain very little dentine. At this stage the teeth are largely enamel shells and are both very brittle and easy to rasp.
Slide 98:
Shows a range of degrees of cheek teeth occlusal surfaces believed to be within the normal range of 10 -35 degrees (the previous accepted “normal” occlusal angle values of 10-15 degrees are too low). Limited scientific work has been performed in this area and the caudal lower cheek teeth often have a higher angle than the remaining lower cheek teeth. Additionally, the lower cheek teeth often have higher occlusal angles than the upper cheek teeth.
Slide 99:
Shows the initial mandibular movement during mastication
The mandible drops down
Moves laterally
Moves dorsally to contact with cheek teeth. During this crushing movement whole grains are crushed and the grinding of forage is started.
Slide 100:
Having made firm contact with the upper cheek teeth the lower jaw then moves in a medial (towards the middle) direction this is termed the power stroke of mastication -when food is ground into small particles between the protruding enamel ridges on the occlusal surface of the upper and lower cheek teeth:
Slide 101:
The image on the left schematically shows the movement of the lower jaw in relation to the upper jaw when eating forage. This is a full lateral movement of the cheek teeth across each other which will prevent sharp dental overgrowths from developing. On the right is the much shorter lateral mandibular movement in a horse that is eating concentrate food, i.e. has a more vertical, chopping action.
In addition to having more restricted mandibular movement when eating concentrates, because concentrates contain so much calories, the horse will only eat for a fraction of the time that it would eat if it had to obtain all of its energy from (lower energy) hay or grass and this restricted time spent masticating also promotes the development of dental overgrowths in a horse that is fed a high concentrate diet
Slide 102:
Enamel overgrowths (“enamel points”) normally develop on the lateral aspects (outside) of the upper cheek teeth and on the medial aspect (inside) of the lower cheek teeth. Most enamel overgrowth damage is caused by the sharp vertical ridges on the outside of the upper cheek teeth injuring the cheeks.
Slide 103:
Shows a horse to the left with sharp enamel overgrowths (and a steep occlusal angle) that could traumatise the tongue. On the right is a tongue with ulceration due to sharp (but not large) enamel points - the bit can compress the tongue down onto such sharp areas on the 1st and 2nd lower CT (lower 6s and 7s).
Slide 104:
This specimen shows the normal vertical ridges the lateral aspect of the upper cheek teeth. The ventral aspect of these lateral ridges are the site of most sharp dental overgrowths in horses. These ridges can vary greatly in depth between normal horses and horses with deep ridges will be more prone to develop enamel overgrowths.
Slide 105:
A deep ulcer is present in the cheeks opposite a maxillary cheek tooth lateral ridge that does not appear to be very sharp in this particular case - it may well be that a nose band or some other piece of tack has pulled the cheeks onto this sharp area of tooth causing or exacerbating this buccal ulceration.
Slide 106:
This image shows a horse which also does not have particularly sharp enamel ridges but has developed very extensive ulceration of the cheeks opposite the lateral aspect of the upper cheek teeth. The vertical ridges on 107 (2nd CT) can be seen to enter an ulcer. This horse would be very painful when wearing a bridle and so could not respond properly to rider signals.
Slide 107:
When enamel growths are neglected, the whole tooth can become abnormally angulated - even developing angles of over 45 degrees. With such abnormal angles, the upper and lowers teeth cannot cross over each other during masticating and the horse now mechanically cannot masticate food properly (can just vertically chop it).
Slide 108:
Multiple dental problems can occur together due to neglect. In this image, the left hemimandible has no overgrowths and has a reasonable occlusal surface angle of 15 - 20 degrees. In contrast the right hemimandible has wave formation with very sharp overgrowths on 407 and 408 (2nd and 3rd CT). Additionally, the occlusal angle is very steep (over 45 degrees) on some of the right mandibular CT. Due to pain and to mechanical obstruction, this right sided problem can only get worse and the horse can increasingly only masticate with the left side of its mouth only.
Slide 109:
The upper left cheek teeth of this aged horse still has some peripheral enamel and some infundibular enamel in the first three cheek teeth - that could still grind reasonably effectively. However the more caudal cheek teeth have lost much of their enamel (“smooth mouth”) and have indeed been worn down to the roots in parts - hence the increased number of dental fragments back here (these are not supernumerary CT!). These smooth caudal cheek teeth are ineffective at masticating food. If fed short grass, or chopped forage such as alfalfa or grass cubes, this horse could maintain an adequate calorie intake but could not do so if just fed hay/haylage without concentrates.
Slide110:
The frequency of routine dental examination and rasping should vary with the age and the work of the horse. At 2-5 years of age, horses are shedding teeth and gaining many new teeth - many clinicians suggest that they should have 6-monthly treatment at this stage.
Likewise, elite dressage horses, show-jumpers and driving horses that need to optimally respond to subtle messages through tack will need special attention. Some of these elite horses will have dental examination and treatment (if necessary) 2-3 times a year in order to prevent any sharp overgrowths or other problems developing. In contrast a brood mare or a retired pony with relatively normal dental occlusion could satisfactorily have a dental examination every 12 months.
Slide 111:
However if horses have some predisposing abnormality such as displaced tooth or some large overgrowths from previous neglect there will be CT malocclusions and overgrowths and such teeth should be examined and treated every 6 months. It is better to treat a little and often, rather than waiting for further more major problem to develop. As some elite horses including international standard horses in many disciplines have inherent dental problems - these defects may be passed on to offspring. No one is going to castrate a Derby winner because it has parrot mouth (as a many top Thoroughbreds do). It is therefore likely that hereditary dental defects will increase in some types of horses in the future.
The level of concentrate feeding can also influence the frequency of prophylactic dental treatment. Horses with normal teeth alignment that largely live outside with minimal concentrate feeding develop less overgrowths than horses that are kept inside particularly if being fed from a height (restricts normal rostro-caudal mandibular movement) and if they are receiving a lot of concentrates.
In summary - The domestication of horses
With use of various tack
Lack of natural selection for good dental traits
High levels of concentrate feeding
Have greatly increased the need for prophylactic dental care of domestic horses.
Slide 112 -113:
Because of the different shapes of the upper and lower cheek teeth rows, a variety of shapes and lengths of rasps (floats) are required to perform a proper floating (rasping) procedure. This figure shows long rasps with solid carbide blades that cut “on the pull” which are used for floating the caudal lower cheek teeth and also shows that angulated rasps are necessary to treat the upper 06s and 07s (1st and 2nd upper CT). Low profile long rasps with obtuse angles are required to remove overgrowths on the upper 10s and 11s.
Slide 114:
A wide variety of motorised dental equipment is now available and these instruments are particularly effective if large overgrowths have to be removed. For safety to the horse and the operator, most horses need sedation when motorised dental equipment is being used.
Slide 115:
The purpose of dental rasping is to remove sharp edges that may irritate the soft tissues but not to flatten the occlusal surfaces. Some enamel must protrude onto the occlusal surface - otherwise the horse cannot grind forage effectively. If the occlusal surfaces are excessively rasped and made smooth, the horse will not be able to masticate properly and thus unable to obtain full nutrients from its food for another 4-6 weeks until the surrounding softer cement and dentine are worn away and some new enamel ridges then protrude. The quality of equine dental care should not be judged by how smooth the occlusal surface is left - despite what some US trained operators claim!
Slide 116:
With the advent of very effective (but aggressive) solid carbide blades and many types of motorised equipment there is increased potential by untrained operators to do great damage to teeth during floating. This figure shows a horse which has had gross over-rasping by a mechanical instrument. The operator has totally flattened the occlusal surfaces and no protruding enamel ridges now remain. There is also evidence of soft tissue damage - with oral bleeding present. Following such (“treatments”) horses will have the sensitive nerve-like, dentinal processes exposed on the occlusal surface of the over-rasped teeth and may not eat properly for up to six weeks following such poor quality treatment.
Slide 117:
Normal cheek teeth rows have 11-13 transverse ridges running laterally across the occlusal surfaces. These have evolved to give a greater surface area to the grinding surface of the teeth. Recently, some operators using pseudoscience claim that these ridges prevent normal rostro-caudal movement of the mandible and so totally remove all of these ridges. This procedure will greatly decrease the dental life of the horse, affect mastication and can also cause great pain if sensitive dentine is reached. This “procedure” flies in the face of the fact that these ridges have evolved over 55 million years for a positive benefit to the horse.
Slide 118:
In this image, two of the transverse ridges (arrows) are slightly tall and the sharp tips of these could rationally be reduced to the level of the other smaller transverse ridges.
Slide 119:
Horses can develop fractures of their cheek teeth and supporting bones from a number of causes including external trauma from kicks and iatrogenic trauma - from operators using dental equipment inappropriately and from rough use of a bit or chiffney. Spontaneous (“idiopathic”) fractures of the cheek teeth are also common, particularly of the upper cheek teeth- especially the 09s (4th CT).
Slide 120:
Shows a young horse with a mandibular fracture. In younger horses that have long reserve crowns of their cheek teeth within the mandibles, these mandibular fractures will invariably involve the cheek teeth. These fractures are normally treated conservatively - with extraction of fractured or infected teeth delayed for many months to assess if they will heal with medical therapy. This period will also allow the mandible to heal more completely prior to any necessary dental extraction - as dental extraction can potentially greatly displace the pre-existing fractures.
Slide 121:
A well recognised problem is caused by untrained operators using dental shears to cut tall teeth if they mistake the sloping nature of the caudal lower cheek teeth as dental overgrowths. They then cut obliquely across the tooth and even sometimes cut the mandible. This figure shows a horse where such an accident has happened, causing massive infection of the mandible and adjacent structures. The mandibular (masseter and pterygoid) muscles are grossly infected and filled with pus - see pus draining from needles and a surgical drainage site along the ventral mandible. Some horses have died from pharyngeal infections following such mistreatment.
Slide 122:
Damage can also occur to the oral cavity by rough use of bit or use of an inappropriate bit. The horse on the left has suffered chronic bit damage to the bars of its mouth and now has mucosal inflammation and thickening of this area and a large periodontal pocket is present in front of 306 (1st CT). This infection may yet cause the loss of this tooth. On the right there is a more typical deep, bit-induced ulcer on the medial aspect of the right bar of the mouth.
Slide 123:
On the left is a further bitting injury involving the left commissures of the lip. On the right - a mandibular x-ray shows evidence of severe and chronic bitting damage with sequestration of the dorsal cortex of this area now present. In other cases fractures of the bars of the mouth may even occur due to this chronic pressure necrosis. This type of severe damage is unfortunately found predominantly in polo ponies and is sometimes termed “polo pony mouth”.
Slide 124:
Fractures to the upper and lower incisors are not uncommon following trauma. Many such fractures occur when horses play with bolts or drop down handles when they trap their upper and lower jaw and then become frightened - and in true equine fashion - pull away vigorously (the behaviour that causes severe wire wounds of equine limbs). Complete jaw fractures are usually treated very effectively by realigning the bones and wiring the incisors to the canine tooth in the adult male horse or to the cheek teeth in the young male or female horse or wiring through or around the mandible (“bars”).
Slide 125:
Spontaneous or idiopathic fractures of the cheek teeth are commonly recognised. They mainly occur in the upper cheek teeth, particularly the upper 09s (4th CT). The most common pattern of fracture involves the two lateral pulp cavities of the cheek tooth and is often termed a “slab fracture”. In many cases the slab fracture will remain attached by the gum and food will become packed between the fracture and the main part of the tooth - pushing the slab fracture into the cheeks, causing discomfort to the horse.
The top right image shows a slab fracture with food pushed into the fracture site and lateral displacement of the fracture fragment into the cheeks (and some medial displacement of the medial fragment).
The lower left image shows a horse with loss of this slab fracture. This result in sharp corners being exposed on the tooth in front of, and behind the fractured tooth, that can cause buccal ulceration.
On the lower right is a typical slab fracture - ventrally the sites of the two pulp cavities are visible.
Most of these slab fracture cases will have deeper infection of the tooth - that may respond to conservative treatment- but some will need extraction later.
Slide 126:
Shows the other main type of spontaneous fracture which occurs through the middle of the upper cheek teeth. This type of fracture is usually preceded by caries of the two infundibula which may then join together to form a large single carious defect in the middle of the tooth. This large hollow now makes the tooth structurally unsound - image on left. Following fracture, the defect becomes packed with food and again part of the tooth moves towards the hard palate as seen in the figure on the right with the lateral aspect being displaced into the cheeks.
Slide 127
Many of these midline sagittal fractures are accompanied by severe infection and sinusitis and the fractured tooth may need to be removed -see image. On some occasions surgeons will leave the more stable part of fractured tooth in place to act as a “spacer” to prevent drifting in of the adjacent teeth, provided that sinusitis is not present.
Slide 128:
If horses develop deep caries on their upper cheek teeth it is possible to remove the carious material by using a high-pressure spray of abrasive micro-refined aluminium powder and then to fill the defects with composite material. This can mechanically strengthen the tooth but no large scientific studies have totally validated the success of this technique to date.
Slide 129:
As many apical infections occur before the true roots develops - the term “apical infection” is more preferable to “tooth root” infection - although in the adult horse these terms both mean the same thing. Because of the very long crown reserve crown of young equine cheek teeth, infections of the apex will also cause infection of the supporting bones. Most of the clinical signs with equine apical infections are related to this infection of the supporting bones.
Slide 130:
The actual cause of apical infections in many horses is not known. In some horses it appears be an imbalance between normal dental wear and deposition of secondary dentine on the occlusal surface - leading to pulpar exposure and apical infections. On the left, a metal probe can be seen entering a darkened, open pulp cavity. In the tooth on the right that was extracted because of an apical infection, hypodermic needles have been placed down the open pulp cavities (there are five pulp cavities in most cheek teeth, 6 pulps in the 06s and 6 or 7 pulps in the 11s)
Slide 131:
The clinical signs of apical infection depend on which tooth is involved. Most mandibular infections occur in very young horses where the apex of the tooth touches the ventral aspect of the mandible and infections of mandibular cheek teeth in this age group will cause swelling and inevitably later, a discharging tract from the ventral mandible.
Slide 132:
An unusually widespread soft tissue infection (cellulitis) associated with a dental abscess is seen on the left. On the right is a horse with an unusually large bony swelling around the infected apex - caused by the body trying to seal off the infected tooth.
Slide 133:
Diagnosis of CT apical infection is normally confirmed by radiographs, including by inserting a probe into sinus tracts if present. This image shows clockwise: the angle at which the x-ray is taken, a badly infected 07 with a sinus tract containing a probe confirming that this tooth is infected, (bottom right) a tooth that has been grossly destroyed by apical infection with a sinus tract in the underlying mandible and a paper clip attached to the soft tissue swelling below it. Bottom left image shows a horse with a chronic apical infection with thickening and sclerosis of the mandible and with a sinus tract present beneath the infected tooth
Slide 134:
Shows the position of the first two and occasionally the 3rd upper cheek teeth - with their reserve crowns and apices embedded in the maxillary bones. Infection of these teeth will cause a facial swelling in front of and dorsal to the facial crest. In many such cases, a sinus tract will later develop - see image top right. A small percentage of these infections will however discharge into the nasal cavity - on the bottom right is a chronic nasal infection (infectious granuloma) caused by an infected 207.
Slide 135:
The last 3-4 maxillary cheek teeth lie within the paranasal sinuses and consequently apical infection of these teeth will cause sinusitis. An example of severe sinusitis is present in the right image.
Slide 136:
There are many other causes of sinusitis other than dental infections and all cases of sinusitis need careful investigation. In this image an intra-oral dental examination is being performed on a horse with a chronic right sided sinusitis. However, many cases are of dental sinusitis will have a normal appearance of the erupted (intra-oral) aspect of the infected tooth.
Slide 137:
In order to confirm the diagnosis of sinusitis and to determine the specific cause of that sinusitis -ancillary techniques are used
including CLOCKWISE:
Nasal endoscopy to see pus coming from the sinus drainage angle,
Lateral x-rays to see pus (fluid lines) within the sinuses,
Direct sinoscopy i.e. where a small opening is made into the sinuses and a flexible Endoscope is pushed inside to directly visualise the interior of the sinus
Scintigraphy, as seen on the bottom left where a hot spot (increased radionucleotide uptake) is shown around a single tooth - indicating that an apical infection is present in this case.
Slide 138:
Treatment of apical infection of CT can be problematic, often requiring extensive, long-term treatments. Post-operative problems are common and repeat treatments are often necessary even when cases receive optimal specialist veterinary care.
Some very early cases of apical infection may respond to prolonged antibiotic courses such as oral potentiated sulphonamides and Metronidazole or alternatively 2-3 weeks of Enrofloxacin (Baytril ®) therapy. Most cases will not respond to antibiotics because of the presence of infected, especially dead calcified tissue, and so dental extraction is required. Extraction can be performed by oral extraction, repulsion or buccotomy.
Endodontic treatment and root canal treatment can potentially save the tooth and thus prevent later drifting of other teeth into the vacant alveolus and the development of overgrowths in the opposite tooth. Unfortunately endodontic treatment of equine CT apical infection has had a poor success to date.
Slide 139:
Repulsion i.e. punching out of the tooth into the mouth under general anaesthesia has been the standard cheek teeth extraction treatment for over 100 years and normally requires general anaesthesia. Great force is required to punch the teeth into the oral cavity.
In this figure a horse that is having a mandibular cheek tooth repulsed under general anaesthesia is having x-rays obtained of the surgical site. The metal punch can be seen entering the ventral mandible but the surgeon must ensure that it is facing in exactly the right direction - otherwise damage can be caused to adjacent teeth.
Slide 140:
On the left, the surgeon can be seen striking the punch with a steel mallet in order to punch the tooth into the oral cavity. On the right, the mandibular wound is being partially sutured (allow some drainage) following repulsion of the complete tooth.
Slide 141:
These are examples of cheek teeth that have been repulsed - which has resulted in them being fractured into many fragments. For this reason, surgeons take further x-rays after repulsion to ensure that no fragments of the tooth have been left behind in the alveolus.
Slide 142:
After repulsion of a cheek tooth in a young horse (deep alveolus) the empty alveolus can be filled with either a dental wax plug (Left) or bone cement (right images) which can last in place longer than dental wax.
Slide 143:
Many problems can occur after repulsing a tooth. In this particular case, food is coming out through the mandibular sinus tract indicating that that a connection remains between the oral cavity and the repulsion wound. Many other cases develop chronic infection of the repulsion site or a chronic sinusitis, necessitating further surgery, alveolar curettage, wound or sinus flushing and/or prolonged antibiotic courses.
Slide 144:
An alternative technique to extract cheek teeth via an opening in the side of the mouth - along the red line over the cheeks. This technique can cause less trauma to the alveolar bones - but as can be seen in image, the facial nerve and parotid duct are very close to this surgical site. Some horses have developed nasal paralysis or saliva leakage from the wound following this buccotomy extraction technique and so many surgeons do not use this technique.
Slide 145:
Because of the problems with other extraction techniques, some surgeons have reverted to the old fashioned technique of oral extraction - using large dental extractors in heavily sedated horses. This involves gradually loosening the tooth over an hour or more using a range of different shaped extractors. High skills and excellent patience are necessary to perform this technique in younger horses with firmly attached cheek teeth.
Slide 146:
Cheek teeth separators are also pushed between the infected and adjacent teeth - to spread the teeth apart and so weaken the attaching periodontal ligaments - as shown in this image.
Slide 147:
When the tooth is eventually loose - as also indicated by the presence of frothy bleeding around the tooth and “squelching” sounds when moving the tooth, the tooth is elevated into the oral cavity using a fulcrum.
Slide 148:
As shown in this figure - even very young teeth can be extracted using the oral extraction technique with the great advantage is that minimal post operative problems occur.
Slide 149:
Endodontic i.e. root canal filling has been used in a limited number of cases to treat apical infection. This is potentially the ideal technique as it retains the tooth in place. This prevents later dental overgrowths on opposite tooth and also prevents dental drifting. Probably because there so much extensive damage and necrosis of the affected area - this technique is often not successful.
Slide 150:
The British Equine Veterinary Association makes extensive efforts to run postgraduate courses on equine dentistry, including at advanced level, and also runs specialised workshops for its dentistry tutors to allow its members to bring their knowledge and skills up to date in this most important and rapidly developing equine veterinary area.
My thanks to Peter Ramzan and Rob Pascoe for reviewing this CD.