Equine Soft tissue Flashcards
What is parrot mouth in horses?
Overjet/overbite - brachygnathism. Overjet is when the 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 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 is aesthetically undesirable. Foals can have their upper in cisors surgically braced to their CT. This is best performed at <6months of age when much maxillary bone growth is still occuring, but ethics are debatable. In adults, these incisor 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.
What are the clinical signs of equine dental disease?
Most common oral disorder in horses is laceration of the cheeks and rarely the tongue by sharp dental overgrowths that develop on the lateral buccal edges of the maxillary and medial lingual edges of the mandibular cheek teeth. Severe oral pain is most commonly caused by deep periodontal food pocketing such as occurs with diastema. Oral pain may result in small boluses of masticated food falling from the mouth during chewing. Painful dental related lesions may also cause bitting problems, such as resistance to the bit, abnormal head carriage and head shaking during work. A common cause of such problems are overgrowths on the buccal aspect of the upper CT which traumatise the buccal mucosa due to noseband or bit pressure. Signs of CT infection include painful facial swellings, especially unilateral swellings of the mandible or the rostral aspect of the maxillary bones, the latter are almost pathogomonic for apical infections. The presence of a unilateral nasal discharge may be due to dental sinusitis. Foul smelling odour, usually indicates anaerobic infections most commonly of the periodontal tissues as with diastemata.
What is sow mouth in the horse?
Underbite - prognathism. Very uncommon in the horse. 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.
How may incisors be displaced?
May be developmental or due to trauma to the foals head prior to eruption of the permanent incisors. If protruding at very abnormal angles they will need to be extracted other wise regular floating may be sufficient.
What will happen if the horse has retained deciduous incisors?
deciduous incisors normally lie on the occlusal aspect to their permanent couterparts, and 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 sedatin and local anaesthesia using dental elevators too remove the rostral alveolar wall.
What are supernumerary incisors?
Permanent incisors that are additional to the normal 6 incisors o each arcade. they have very long reserve crowns that are usually intimately relate 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. Extraction of these teeth is 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.
How may fractures of the incisors occur? how should these be treated?
Fractures of the incisor teeth and often the supporting rostral mandibular or premaxillary bones can occur due to trauma, usually from kicks and commonly result in exposure of the pulp cavity. All teeth of young horses contain very wide apical foramina along with a very large and vascular pulp, which can resist the inflammation ad infection that will inevitably develop in exposed pulp from saliva and oral bacteria. Consequently, pulp exposure in young horses does not necessarily lead to deep pulpar infection and subsequent ischaemia with tooth loss as usually occurs in canine teeth. However all incisor fracture cases should receive tetanus antitoxin and prolonged antibiotic therapy. Preferably, endodontic treatment should be performed by a specialised 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. In some young horses the exposed pulp will without treatment become sealed off at the site of exposure by reparative dentine formation with the tooth remaining vital and continuing to erupt normally.
How do abnormalities of incisor wear present? how may this occur?
On full manual lateral movement of the mandible with the horses jaws closed, the incisors should separate. Abnormalities of the occlusal surface of the incisors will prevent this normal manoeuvre, usually unilaterally. These incisor disorders include steps due to the traumatic loss or mal eruption of the opposing incisor and subsequent overgrowht, as well as smile and frown that occur with parrot mouth and sow mouth.
What may be the clinical signs of horses with retained deciduous cheek teeth?
Retention of the remnants of the deciduous cheek teeth (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 the loose caps should be removed using a specialised cap forceps or a long slim elevator. The prolonged retention of caps has been alleged to cause delayed eruption of the development of large eruption cysts under the apices of the permanent CT. the presence of very enlarged eruption cysts, especially if unilateral, should prompt a thorough oral and radiographic examination for the presence of retained deciduous CT teeth. The practice of 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.
What are diastema?
The occlusal surfaces of all 6 CT are normally compressed tightly together an the CT row functions as a single grinding unit. This is achieved by the action of the angled first CT and the last two CT, compressing the occlusal aspect of all the 6 CT together. Even with age, the progressively smaller reserve crowns usually remain tightly compressed at the occlusal surface. If abnormal spaces in these - diastema- develop, 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 spaces and leads to progressively deeper food impactio and gingival recession, followed by deeper secondary periodontal disease. May horses show severe clinical signs (quidding, even weight loss) when fed hay/haylage and improve greatly when at grass. Secondary sinusitis can also occur. Such a disorder will be recognised by visually or digitally detecting the 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 the affected teeth and can even extend deep into the mandible or into the maxillary sinuses. Diagnosis can be difficult without the use of a dental mirror or endoscope. 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 fine chopped forage diet e.g grass or alfafa cubes often reduces or removes clinical signs also. Abnormal transverse overgrowths may develop on the teeth opposite to the 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 of 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.
How does rostral positioning of the maxillary CT row occur?
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. Similar overgrowths on the caudal aspect of 311&411 frequently go undetected and such overgrowths can lacerate the adjacent oral mucosa ad are best reduced with power instrumets. Molar cutters and percussion guillotines to remove large 311/411 overgrowths risks fracturing the teeth.
How may cheek teeth displacements occur?
Two different causes of CT displacements can occur in horses. in the most severe cases, medial or lateral 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 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 quiding. Abnormally protruding areas of displaced CT and secondary overgrowths can lacerate the oral soft tissues and cause pain. Acquired CT displacements can develop in older horses and are usually associated with lesser degrees of CT displacement.
What are supernumerary cheek teeth and where do they most commonly develop?
Supernumerary CT moot commonly develop at the caudal aspect of the CT rows. because of their irregular shape and overcrowding, periodontal food pocketing occurs between them and the normal caudal cheek tooth, 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 poossible), in others removal of overgrowths is all that is required. Developmentally reduced numbers of CT is rare in horses and may be associated with enamel defects.
Why may periodontal disease occur in horses?
Unlike in brachyodont animals, 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 proloonged eruption and continuous development of new periodontal fibres in the horse, equine periodontal disease is not necessarily irreversible as is usually the case with brachyodont 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.
What may cause traumatic disorders of the cheek teeth?
Swellings of the maxillary a madibular bones can also be caused by external trauma due to kicks and less coommonly due to tumours in addition to swellings caused by developing permanent Ct. 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 d develop, it is worthwhile persevering with conservative therapy until radiographic changes confirm the presence of definitive dental infectio. Extraction should be delayed for some months to minimise the chances of causing a displaced fracture of the mandible. Bit induced injuries to the mandibular interdental space and of lips and gingiva ca occur due to 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.
Describe where idiopathic fractures of the CT occur and what occurs after the fracture
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 cavities. 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 fractures of the maxillary CT are also common and usually secondary to advanced infundibular caries. Deep seated infections of the alveolus and sinus frequently accompany these fractures in a younger horse. 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.
Which oral tumours can occur in the horse?
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 or cement or combinations of all three dental compoonents. 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.
What is the cause of periapical infections of the CT?
Apical infections in the CT are often caused by blood or lymphatic borne infections 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 the cemental defects in the two infundibulum leading to infection of the pulp or saggital 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. In the early stages, the infection usually remains confine to the apex, adjacent to the sinus tract and all the pulp cavities remain vital. At this early stage antibiotic treatment eg 2-3 weeks of trimethoprim /sulphonamide may suffice. Later endodontic therapy or more usually dental extraction will be required.
What are the clinical signs of periapical infections of the CT?
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 6s ad 7s will cause focal swellings of the rostral maxilla. Infections of the caudal 4 maxillary CT generally results in a secondary sinusitis, with the presence of a chronic, malodorous unilateral nasal discharge. In older horses, apical infections may just drain through the periodontal membrane or open pulp hoorns into the mouth and infection of the supporting jaws may not occur. apical infections that arise as an extension of deep periodontal disease from abnormal spaces surrounding the CT iincluding, supernumerary teeth, diastemata, developmental and acquired dental displacement will obviously drain into the mouth via this periodontal rooute.
When should extraction of the CT in the horse be undertaken?
Extraction of the long crowned 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 r not, conservative treatment and not extraction should be undertaken, including antibiotic therapy for suspect mandibular or rostral maxillary apical infections and maxillary sinus lavage and antibiotic therapy for suspect caudal maxillary CT apical infections. only when definite evidence of dental infection is resent should dental extraction be performed.
What may cause oral dysphagia in the horse?
The prehension and mastication of food are distinct from the initial i.e oral phase of swallowing. Dropping partially masticated food is usually caused by pain during mastication e.g with cheek teeth diastemata and is dysmastication rather than an inability to swallow. Less commonly fractures, in particular mandibular and premaxillary fractures e.g due to kicks, can cause oral dysphagia. Fractures of one hemi mandible in the horse usually do not need to be surgically supported as the normal hemi mandible will effectively act as a splint. Disorders of the tongue can be due to paralysis of the 12th cranial nerve, rarely by inappropriately restraining a horse by the tongue, but most commonly as part of general neurological disorders such as botulis. Occasionally acute onset oral dysphagia can be caused by sharp wooden or metallic foreign bodies lodging in the tongue or oropharyx. Such cases preset with anorexia and excessive salivation. Careful examination of the oral cavity and of the oropharynx in larger horses using a mouth gag will commonly reveal these foreign bodies which can be manually removed. Tumours of the oral cavity such as squamous cell carcinoma are another rare cause of oral dysphagia.
What are the potential causes of pharyngeal dysphagia?
In contrast to the signs of oral dysphagia, the main clinical signs in horses with pharyngeal dysphagia and oesophageal dysphagia are the presence of masticated food flowing down both nasal cavities after eating and frequently the presence of coughing due to aspiration of food material and saliva. Causes; congenital neonatal neuromuscular pharyngeal dysfunction, cleft palate, guttoral pouch mycosis, strangles infectio, botulism, heavy metal poisoning, nasopharyngeal foreign bodies, naso pharyngeal tumours, guttoral pouch disease.
Dysphagia in neonates cause milk to come own the foals nose and coughing soon after suckling. some cases develop inhalation pneumonia. Endoscopy is required to differentiate cleft palate from neuromuscular dysfunction. The prognosis is very guarded with a severe cleft palate, surgery being very difficult and invariably unsuccessful in restoring normal function, as horses are obligate nasal breathers and the soft palate - epiglottis relationship is crucial during exercise. Many cases of neuromuscular dysphagia in foals can improve over a week or so and such cases need feeding by G tube during this period.
What is guttoral pouch mycosis?
Aspergillus fumigatus is an opportunist pathogen present in the URT of many indoor horses in temperate climates. For unknown reasons it can invade the roof of the guttoral pouch causing very destructive changes and secondary bacterial infection. Endoscopically blood or mucopurulent material may be seen flowing from the diseased ostium. Within the guttoral pouch, grey black or white fungal and possibly fibrinous plaques can be visualised on the mucosa overlying vital nerves and blood vessels. The clinical signs of GPM largely depend on which of the many vital underlying nerves or blood vessels are damaged.
Cranial sympathetic nerve - horners
7th cranial nerve - facial paralysis
9th, 10th 11th - pharyngeal paralysis (dysphagia)
12th - tongue paralysis
Internal carotid artery, internal maxillary vein, internal maxillary artery, external maxillary artery - massive haemorrhage.
What is guttoral pouch empyema?
This is a sequel to starngles, with Abscessation and drainage of the retropharyngeal lymph nodes into the Guttoral pouches, which have poor natural drainage. Extensive swellings of the guttoral pouches can interfere with upper airway or swallowing, occasionally leading to stridor or dysphagia. with more chronic cases chronically draining lymph nodes, empyema or chondroid formation can occur. The signs may just be a chronic low grade purulent nasal discharge which is unilateral. These cases are significant, long term carriers of strangles.
What is guttoral pouch tympany?
In this congenital condition, a neuromuscular valve defect or rarely a abnormal tissue fold at the nasopharyngeal ostium acts as a one way valve, allowing air into but not freely out of one or both guttoral pouches. radiography will show an enlarged, air filled pouch ad a ventral fluid line is commo. in cases of unilateral GP tympany, a Foley catheter can be placed into the GP for a few weeks and may distort the ostium into an open position. Alternatively a window is created in the thin midline septum between the two pouches with a transendoscopic laser, allowing air to exit via the normal ostium. With bilateral cases, surgical enlargement of one of the ostia and GP septal perforation can be attempted or a fistula created between the roof of the nasopharynx and GP.
How can strangles cause dysphagia?
This upper respiratory tract infection often involves groups of horses. it can cause retropharyngeal abscessation or accumulatio of pus in the guttoral pouches which compresses the asopharynx and causes dysphagia. Other associated signs include purulent bilateral nasal discharge and abscessed submandibular lymph nodes. Treatment involves isolation of cases and drainage of guttoral pouches by feeding off ground, lavage or rarely GP surgery.
How does botulism initially present in the horse?
Botulism and heavy metal poisoning will cause weakness of all skeletal muscles, however pharyngeal dysphagia can be an initial presenting sign. Endoscopy will confirm the presence of pharyngeal dysphagia without any detectable underlying lesion. Closer examination of such cases may also reveal weakness of the hindlimbs and a flaccid tail.
What is choke?
Choke is a very common condition due to obstruction of the lumen of the oesophagus with impacted food resulting in sudden onset of distress, salivation and dysphagia -thus causing a nasal discharge containing food. if uncorrected, dehydration and hypochloraemia will occur after a day or so. In the UK, obstruction is most commonly due to sugar beet pulp or pelleted food which for unclear reasons blocks the oesophagus and obstructs a variable distance of its lumen. diagnosis is by a history of sudden access to large amounts of sugar beet pulp or to dry unsoaked sugar beet pulp w hen previously fed wet pulp and an inability to fully pass a nasogastric tube. A diagnosis may also be confirmed endoscopically and by ultrasound. Palpation of the cervical oesophagus may reveal a swelling in fine skinned horses with rostral oesophageal obstruction.
What is an oesophageal stricture?
This is the result of scarring following circumferential ulceration of the mucosa resulting in circumferential fibrosis and decreased luminal diameter, resulting in recurent obstruction. it is most common following choke that has not been cleared by 36-48 hours. Diffuse but non circumferential focal ulcers and scarring can usually be managed by feeding of soft soaked food, however circumferential strictures are extremely difficult to manage and although resection or boughinage can be attempted, new strictures may reform.
What is an oesophageal diverticulum?
A developmental defect or rupture of the muscular layers results in an out pouching or diverticulum of the mucosa or scarring and adhesions of the layers of the lumen together. Traction diverticula carry a better prognosis and may heal by second intention. surgical treatment of pulsion diverticula by inversion of the lumen and overlying with a mesh may be attempted. There is a risk of recurrent laryngeal nerve damage with this surgery.
How may oesophageal perforation occur?
This is very rare in horses cf dogs, may result from trauma such as a kick to the ventral aspect of the neck with the oesophagus compressed between the hoof and the ventral aspect of the vertebral body. it may also be caused by an oesophageal foreign body or occasionally iatrogenic damage with a sharp nasogastric tube. It may be difficult to identify and is potentially very serious leading to widespread empysema, cellulitis, mediastinitis. Oesophagoscopy and contrast enable a diagnosis.
