Introduction
The goal of surgical correction for oral trauma cases is the re-establishment of function with a minimum of discomfort. This will often involve the restoration of a normal (before trauma) occlusion. Maxillary and mandibular fractures are different to fractures involving the appendicular skeleton, because jaw fractures will heal in the presence of fracture gaps and some mobility, so long as vascularity is protected and there is no infection present. Rigid fixation is not necessary, because the mandible is not a weight bearing bone. If the occlusion is restored and measures are taken to prevent infection, any mandibular or maxillary fracture will heal. Perfect alignment of the fracture is not always practical or necessary. However, the fractured mandible must still function for eating and drinking during the healing process and this will cause some movement at the fracture site. Monitoring of the fracture healing phase is imperative.

Anatomy
Most fractures of the head involve the mandible. An understanding of the anatomy of the mandible is important when considering mandibular fracture repair.

The mandible is really two mandibles joined by a fibrous joint (mandibular symphysis). The mandible consists of a horizontal portion (body) supporting the teeth and the vertical portion (ramus) providing surfaces for muscle attachment and articulation with the skull. Major neuro-vascular structures, including the mandibular artery and vein, and the inferior alveolar nerve enter the mandible on the caudo-medial aspect through the mandibular foramen. These structures provide the neurovascular supply to the mandibular teeth and the mandible. They occupy the ventral third of the horizontal ramus and run in the mandibular canal. Ventral to the mandibular canal is a single layer of cortical bone. The neurovascular bundle exits the mandible on the lateral surface from the mental foramina. These structures as well as tooth roots preclude the use of conventional plates or IM pins in the mandible.

Mandibular fracture biomechanics indicates the tension side of the mandible is the tooth side. Techniques that engage the teeth secure the tension surface allowing natural compression of the ventral surface.

Oblique fractures of the mandibular body can be classified as favourable or unfavourable.

Fracture lines that run in a caudo-dorsal direction are considered favourable because the muscular attachments to the mandible have a primarily ventral insertion causing compression of the fracture.

Fracture lines which run in a caudo-ventral direction are considered unfavourable because muscle forces lead to distraction of the rostral segment.

Causes of oral trauma
Damage to the face and oral cavity including the teeth results from:

• Motor car accidents
• Falls
• Fights with other animals
• Gunshots, kicks
• Blunt trauma
• Iatrogenic: poor extraction technique, pathological fractures - advanced periodontitis in old small dogs
• Misc. including bone and rock chewing 

Maxilla versus mandible

• Mandibular fractures are more common than maxillary fractures
• Mandibular fractures are often compound, and are usually seen in the horizontal ramus
• Maxillary fractures are often comminuted
• Cats: more often see mandibular symphyseal luxations or TMJ luxations
• Cats: High rise syndrome and road trauma commonest causes of fractures

For jaw fractures:
Following stabilisation of the patients vital signs a detailed examination including:

• Neurological exam
• Radiographic survey films plus dental radiographs. Standard dorsoventral and lateral views are difficult to interpret because of superimposition. Oblique views may be more useful as well as intraoral views.
• Gentle palpation and manipulation of the jaws to assess occlusion. Palpation of the ventral border of the mandible to feel for steps in the bone or asymmetry.
• Signs of open or compound fractures, epistaxis, airway obstruction etc.
• Assessment of teeth in the fracture line. Teeth in the fracture line may be left in place if there is no periodontal (no bone loss) or endodontic disease associated with these teeth. Loose teeth may need to be extracted. These teeth, however, may show signs of pulpal necrosis at a later date and root canal therapy or extraction may be required. If non union or delayed union occurs-consider extraction of compromised teeth in the fracture line. Teeth in the fracture line should always be monitored during bone healing for any adverse complications such as delayed healing.
• Anaesthesia may involve intubation via pharyngostomy to allow manipulation of the jaw fracture and assessment of occlusal alignment.

Useful equipment/materials for fracture repair include:

• Dental acrylics (polymethyl methacrylate) e.g. jet acrylic mixed in a 2:1 ratio powder to liquid monomer. Does produce an exothermic reaction.
• 24/26 gauge orthopaedic wire, wire cutters, old needle drivers, acrylic bur
• Composite resin cements/ orthodontic brackets
• 37% phosphoric acid etch, bonding agents
• Cold curing temporary crown and bridge resins
• Dental intraoral film
• Burs including acrylic burs
• Bandages

Fracture repair of mandible/maxilla involves:

• Realignment to pre-fracture occlusion. A malocclusion post healing should be avoided, because this may lead to increased tooth wear, periodontal disease, pain during mastication, and possible TMJ problems.
• Stable but not rigid fixation
• Avoidance of vital structures including tooth roots, nerves
• Gentle tissue handling, maintenance of vascularity at fracture site
• Extraction of diseased teeth within the fracture line
• Minimal invasiveness and early return to self feeding  and normal jaw function
• Pain and infection management

The use of intra oral and extra oral acrylics (polymethyl methacrylate) is a simple but efficient method of fracture repair

• This technique doesn’t address the bone fracture per se, but utilises the splinting and stabilisation of the occlusion to aid in bone healing
• Teeth up to level of the 4th. maxillary premolar and mandibular 1st. molar can be incorporated in the acrylic splint.  

Mandibular fracture:

• Mandibular fractures represent 3-6% of all fractures seen in the dog
• 15% of all fractures seen in the cat affect the mandibular symphysis
• Most common location for mandibular fracture in the dog is between PM1 and M2
• Pathological fractures may occur due to advanced PD, neoplasia and metabolic diseases.
• Mandibular fractures will heal in the presence of a fracture gap and some mobility, so long as vascularity is maintained and there is no infection present.

Methods of mandibular fracture repair

• Coaptation “tape” muzzle: often successful, but doesn’t work for all head types. A 10 mm opening is left for taking in of a liquid diet. Alternatively, the jaws can be firmly bandaged after the placement of a pharyngostomy feeding tube or nasogastric tube. Care needs to be taken re aspiration of food, hyperthermia, bandage dermatitis and post fracture malocclusion, which may not be ideal. Tape muzzles may also interfere with facial growth in young animals. Usually kept on for 2-8 weeks, depending on the nature of the fracture. They can be used as a temporary measure, prior to a more definitive repair. Tape muzzles will need constant monitoring for possible adverse side effects.
• External fixation: good but iatrogenic trauma- tooth roots, mandibular canal, thermal necrosis of bone/soft tissue. Loosening of pins, pin-tract infection and self mutilation/furniture injury of concern.
• Internal fixation with conventional plates, IM pins and screws: is not justified due to iatrogenic damage to tooth roots and vital structures. Uni-cortical screws and mini-plates are used extensively in human maxillofacial surgery, but at present their use in veterinary maxillofacial surgery is rare.
• Interosseous wiring between the fracture ends on its own or combined with interdental wiring is an inexpensive and simple method of repairing mandibular fractures (especially vertical fractures of the mandibular body).   
• Interdental fixation: Good, inexpensive, minimum disruption to fracture blood supply and restores occlusion to pre trauma status. Interdental fixation may include inter-arch fixation especially in cats with comminuted fractures of maxilla/mandible.
• Cerclage wiring around the whole mandibular body (circumferential wiring), incorporated with interdental wiring/acrylic is a good technique when dealing with oblique fractures of the body of the mandible.
• Acrylic +/- wire is a very effective, yet non-invasive way of stabilising mandibular fractures. The teeth are cleaned and then polished with non-fluoride pumice. The teeth are placed into the pre-fracture occlusion, and then they are acid etched and cold curing acrylic applied directly to the teeth via an extruder gun. Generally, acrylic is applied to the buccal and lingual sides of the mandibular premolar teeth, but at the level of the first mandibular molar, acrylic is only applied to the lingual surface, so as not to interfere with the opposing maxillary arcade. 

Maxillary fracture repair
Non-displaced fractures of the maxilla may not require any stabilisation at all. If stabilisation is required the use of a tape muzzle or wire/acrylics as in mandibular fracture repair is recommended.

• Compression of the maxilla is repaired with expansion of the maxillary bone (sometimes approached through the nasal cavity) to its original position and stabilisation with figure of eight wiring of the teeth and reinforcement with acrylic. Be aware that the acrylic will need to be built up on the buccal side of the teeth as one goes further caudally. This is so that there is no interference with the occluding mandibular teeth.
• The use of the contralateral maxilla may aid in stability and wire can be run across the hard palate to incorporate teeth of the other side. Again, reinforcement of the wire with acrylic is an option.
• Inter-arcade fixation can be used when dealing with multiple fractures of both jaws. This involves temporarily bonding the jaws partially closed, whilst maintaining the occlusal alignment. Light cured composite resin cements work well for this procedure. The occlusion is reduced enough (usually one third overlap of the canine teeth) to provide stability and yet allow ingestion of a liquid diet. As a rule, usually the canines only are used for bonding, but occasionally the carnassial teeth (Maxillary 4th Premolar and Mandibular 1st molar) are used also to provide added stabilisation. 

  
Analgesia and antimicrobial therapy
The use of pain relief is imperative when dealing with soft and hard tissue injury in the oral cavity.
Opioids, local analgesia, and NSAIDs can be used for peri and post operative pain relief in oral trauma cases. Butorphanol can be used IV, IM or SC for analgesia. Duration of analgesia is fairly short; about 1-2 hours for moderate pain and 2-4 hours for mild pain.

Local anaesthetic agents such as lignocaine hydrochloride (4-6 mg/Kg) and bupivacaine (2mg/Kg) can be infiltrated locally close to the site of the trauma or given as a nerve block to give from 1 hour (lignocaine) up to 8 hours (bupivacaine) analgesia.

NSAIDs, such as carprofen (Rimadyl, Pfizer Animal Health), have been shown to produce      little toxicity with parenteral or oral use and has been used peri/postoperatively for the relief of pain. The added anti-inflammatory effect will aid in swelling and pyrexia associated with the release of inflammatory mediators. Caution should be exercised in dehydrated, hypovolemic or hypotensive animals due to the risk of increased renal toxicity. Where bleeding is, or may be, of concern, carprofen or meloxicam may have minimal to no effect on coagulation due to lack of anti-thromboxane activity. Ketoprofen should not be used in these cases due to potential for anti-thromboxane activity.

Remember to always stay ahead of pain and discomfort by the regular dosing of analgesics in the early post operative phase.

Antibiotic usage in oral trauma cases is warranted when dealing with severe soft tissue injury or compound fractures.

Clindamycin hydrochloride ( Antirobe, Pfizer Animal Health-. Dose 11mg/Kg BID) is particularly useful when dealing with compound jaw fractures due to its good penetration into bone and its activity against anaerobic bacteria commonly found in the mouth.

Summary for jaw fractures
The use of dental materials and orthopaedic wire offers a simple, inexpensive alternative to more traditional methods of fracture repair. The re-establishment of the occlusion is the most important consideration when treatment planning for maxillary or mandibular fractures.

Injury to the tooth
The general practitioner is often presented with pets that have suffered some form of traumatic injury.
Traumatic injuries to the head region are often the sequelae of motor car accidents, falls, fights, and the odd cricket/baseball bat injury.

Broken teeth can also be due to bone or rock chewing, resorptive lesions or tooth wear and eventual fracture of the crown.

Clinicians, in examining the injured animal, should include as a part of their thorough clinical examination, an examination/palpation of the bones of the head for fractures, the temporomandibular joints for luxations and intracapsular fractures, and the oral cavity for broken teeth, displaced teeth or soft tissue injuries to the tongue, hard palate and oral mucosa.

Broken teeth are classified as having:

1. An uncomplicated crown fracture not involving the pulp.
2. A Complicated crown fracture involving the pulp
3. A crown/root fracture which is uncomplicated and not involving the pulp.
4. A crown/root fracture that is complicated and involves the pulp.

When the pulp is not exposed, simple smoothing of the roughened enamel/dentine should suffice.

When the pulp is exposed and the exposure is recent (within 2 days); a vital pulpotomy can be performed. This procedure works best in younger dogs (< one year of age), but can be performed on many dogs with a recent pulpal exposure. This procedure removes the inflamed coronal pulp and then medication is placed over the pulp and the fractured tooth restored with a filling. Vital pulpotomies can be performed on any tooth with a fresh pulpal exposure (evidence of haemorrhage from pulpal stump), but the success rate of the procedure diminishes as the time between the exposure and the treatment lengthens, and success rate decreases with increasing age of the dog.

When the pulpal exposure has been long standing (evidenced by a black hole in the centre of the damaged tooth), the clinician has three choices in managing the broken tooth. The tooth should either be extracted, a root canal treatment performed, or in the case of geriatric patients where general anaesthesia may impose an unacceptable risk- a wait and see approach and monitoring for symptoms/signs of infection (not an ideal option).

This is because when the pulp becomes necrotic bacteria enter the root canal system and bacterial toxins resorb periapical bone and the tooth will eventual show signs of periapical pathology, with either a draining fistula to the skin or mucosa, or pus draining from the necrotic pulp or adjacent periodontal tissues.

Summary

The management of tooth injuries should be a part of the overall treatment plan when
examining pets that have suffered trauma.

Clinicians should be aware of the options available in managing a broken tooth. The pet owning public are more dentally aware these days, and expect their veterinarian to be able to diagnose and manage a broken tooth, or refer them to a veterinarian who can treat fractured teeth. Too many times, broken teeth are diagnosed well after the original accident, or worse still, not picked up at all.  A phone call to a veterinary dentist or even your local dentist may assist the clinician when faced with the dilemma of what to do with that broken tooth?

Injury to the tooth’s supporting structures- Luxation/avulsion injury:

Avulsion (when the word is used correctly) is the term applied when teeth are completely out of the alveolus.
Luxation is when the tooth is still within part or all of the alveolus and can be intrusive (pushed into the alveolus), extrusive (partly out of the alveolus) or lateral (which will have an associated alveolar fracture).

The term avulsion is often used in veterinary contexts to include all of the above conditions.
In dogs and cats, the canine teeth are the most frequently affected by luxation and avulsion injuries, with lateral luxation being the commonest.   

Treatment
Time is the most critical component in the treatment of these displacement conditions.  The sooner they are corrected, the better the prognosis.  This is especially true of teeth that are avulsed out of the mouth.
           
Avulsion
The tooth should be stored in milk until it can be replaced in the mouth.  If very contaminated, it can be washed under tap water for about 10 seconds and then placed in the milk.  Under no circumstances should the tooth be “scrubbed” clean as this will damage the periodontal ligament fibres and reduce the chance of success.

Once at the surgery, the tooth can be gently washed with saline before being replaced.  The alveolus should be flushed liberally with saline to remove the clot (again do not curette the alveolus) before replacing the tooth.

Once replaced firmly into the alveolus, the tooth should have rigid splinting for 6 to 8 weeks.  This is easily done for the canines by using a figure of eight wiring to the other canine. The wires need to be firmly attached to the tooth using composite resin bonding techniques (methyl-methacrylate can suffice if this is not available) The tooth is radiographed and the animal is placed on antibiotics post-operatively.

Endodontic therapy is essential in these teeth. The outcome in humans is greatly improved if the root is filled with calcium hydroxide for 6 months prior to conventional endodontics.  This leads to a thicker cementum repair and less root resorption. 

Lateral luxation

These teeth need to be repositioned as soon as possible and soft tissues sutured, followed by rigid splinting for 6 weeks (there will also be an alveolar fracture).  The animal is placed on antibiotics and a post-op radiograph taken.                                    

Teeth with lateral luxation may have an adequate blood supply and need to be monitored to ascertain if endodontics is necessary (approximately 50% will need endodontics). 

Intrusive and extrusive luxations

These are rare injuries to the teeth of domestic pets.  The affected tooth should be repositioned as soon as possible, antibiotics commenced and the tooth splinted for 6 weeks.  Endodontics will be required as for avulsion.

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Dr Tony Caiafa