MANAGEMENT OF ORAL TRAUMAor‘PUTTING HUMPTY TOGETHER AGAIN…’Dr WAYNE FITZGERALD, BVSC MACVSC (Vet. Dentistry)Reservoir Veterinary Clinic226 Spring Street, Reservoir, Vic. 3073In attempting to treat fractures of the Maxilla or Mandible the forces of gravity,muscles and mastication; and the function of occlusion place these fracturesinto a different category to conventional orthopaedic surgery.The innervation and vascularity of these structures is rich and as a resulthealing times are short and infection resistance is high. Vital structures suchas canals and tooth roots occupy much of the bone’s integrity and along withfunction must be taken into consideration when choosing a method of repair.Fracture of the bones of the head may result from trauma and/or pathologysuch as advanced periodontal disease. Our first priority aim is to restoreocclusive function thus allowing the animal to eat and drink.Essential to the management of these cases is a working knowledge of theanatomy and the biomechanics of the head. It is very useful to have accessto a skull of the species you are working with as a reference for makingassessments of the injuries, radiographs and assessing possible treatmentoptions.Because of the complexity and over-riding nature of the bones and otherstructures in the head, it is difficult to obtain clear diagnostic radiographs withscreen films in cassettes. Intraoral films are often required as they reduce thesuperimposition problems and improve detail.The nature of the fracture/s and the forces acting upon the mandible whichaffect the displacement of fractures, influence the placement of our fixativedevices.These forces are: gravity, mouth closing muscles (temporal, masseter andpterygoid muscles) and opening muscle (digastricus m.) and they often causeover-riding of fragments.
2As an example, a fracture of the mid-horizontal ramus might behave likethese, depending on the fracture type:The tension-band side of the mandible is the alveolar border and as long asthe ventral border is intact, interdental wiring alone is often adequate.Most fractures will be compound with vital, or devitalized, teeth complicatingthe picture. Fractures often include the dental alveoli.On the plus side, the blood supply to the head is very generous and healing isoften quite rapid.
3It is generally considered necessary to extract those teeth involved in thefracture site, especially if unstable, because of exposure of large areas ofperiodontal attachment and devitalization of the endodontic system. On theother hand, stable teeth may be very useful as ‘spacers’ in a fracture line andas points of attachment of fixative devices, so make this decision afterevaluating your treatment options. After healing, the tooth could either beextracted or root canal therapy could be performed.Except for size, the canine and feline mandibles are similar. The lower caninetooth occupies almost the entire width of the mandible and 65-75% of it lies inits alveolus.It is not acceptable practice to drill through tooth roots when placing fixationdevices.The mandibular canal is found in the ventral third of the body of the mandible.It contains the mandibular artery and vein, and the mandibular alveolar nerve.Cause it no harm!Most of the muscles of mastication insert on the vertical ramus and the caudalportion of the mandible.Exposures:Oral approach is best for fractures rostral to the last molar,Extra-oral approach for the ventral half of the body of the mandible.Principles: • Keep the method of repair as simple as possible, use the minimum number of implants, • Preserve soft tissue attachments, • Provide drainage whenever severe contamination or trauma is involved, • Remove abscessed or loose tooth, especially when in the fracture site, • Avoid tooth roots and the mandibular canal, and • Avoid the soft tissues in the space between the mandibles, this includes the tongue’s frenulum.Ancillaries: • Oxygen tent, • Steroids to reduce swelling, • Tracheostomy *, and • Pharangostomy.
4 • Temporary tracheostomy is often useful to clear the oral cavity during the treatment and also permits free movement of the mandible to check occlusion.Treatment Options:Tape muzzles can be used for temporary fixation and prevent drying of themucus membranes of the oral cavity. They can also be used to supportinternal fixation and sometimes for stable, non-displaced fractures.Fractures rostral to the molars tend to heal rapidly and a tape muzzle alonemay be satisfactory. The likelihood of a malocclusion is greater with thismethod than with the other fixative devices.However, they are difficult to place and maintain on cats and thebrachycephalic dog breeds where stay sutures may be useful.Wires, pins, plates & screws.With or without an acrylic bond assistance, orthopaedic stainless steel wiresof 24, 22 and 20g sizes are the most useful materials in oral fracture repair.Interarcade or mandibular-maxillary fixation is a useful technique in dogsand cats with unstable fractures of the mandible or TM joint. Aim to maintainthe alignment of the ‘canine interlocks’. If the jaws are wired or bonded fullyclosed, fluid and nutrition must be given by pharangostomy tube; however if agap is left between the incisors (mouth partly open) they will learn to adaptand can satisfactorily lap.Direct bonding of teeth. Is used with alveolar segment fractures and withsubluxated or avulsed teeth. It requires minimal material to fix the teethmaking for better oral hygiene. A disadvantage is the lack of strength and thelikelihood of materials fracturing because of poor anchorage from loosenedteeth. Incorporating reinforcing wire improves the strength.Orthodontic appliances. Brackets, for instance have some applications infracture patients, however, generally wiring techniques are more useful.Mandibulectomy in full or partial form may in some cases be indicated and isconsidered to be a salvage technique.Materials:Orthopaedic wire is still probably the most useful and practical implantmaterial used in dental orthopaedics. It is very inexpensive and does notrequire costly ancillary equipment to use. Wire can be placed directly in bone,around fragments or around teeth
5Interdental wiring: it may be necessary to ‘notch’ the teeth or even bond thewire to the teeth. 22 to 20-gauge wire is generally satisfactory.Transfurcational interdental wiring: the wire passes between the roots of theadjacent teeth.Interfragmentary wiring: used in the repair of oblique and some multiplefractures. Wires are placed at right angles to the fracture line.Bone defects can make wiring techniques difficult because of the need toplace wires on the tension side of the fracture, which can cause collapse andmalocclusion.The Ivy and Stout methods of interdigital wiring are applicable to the dog andcat, but application depends on the health and integrity of the teeth adjacentto the fracture. The application of plastics to the wire can improve the stabilityof the wiring method, especially if there are bone fragments and does notfurther disrupt soft tissues.The principles here are to include two or three teeth on either side of thefracture.Ivy wiring method: Stout wiring method:Wiring techniques.Eyelet Technique (Oliver, Eby, Ivy). A versatile and easy to apply eyeletwiring technique. A 50mm length of wire is twisted around an instrument tomake a small loop. The ends are passed through the interproximal space fromthe buccal side, one end is then passed around the mesial tooth and backthrough the next interproximal space. The other end likewise around thedistal tooth. One end of the wire is then passed through or medial to theeyelet and the two ends are twisted to form a ‘button’. This produces a loop
6and a button to be used for supporting other wires, elastic loops, ligaturesetc. After sufficient numbers have been made, the teeth are brought intoocclusion and ligatures or elastics are placed between the uppers and lowers.This technique is especially useful when fractures are simple and ‘favourable’.It is less useful with grossly displaced fractures of tooth-bearing areasbecause of lack of arch rigidity.Continuous Loop Wiring Technique (Stout). A series of eyelets on a singlestrand of wire is produced as follows: A wooden handle of a cotton-tippedapplicator (spacer) is placed against the teeth to aid in forming the wire loops.A wire is placed around the most distal molar with both ends projectingtowards the buccal side. The distal end becomes a horizontal buccal wire; themesial wire end is the active passing wire to form the loops and should belonger than the other end. The ‘active wire’ is passed over the horizontalbuccal wire and the spacer then back through the same interproximal spacefrom which it emerged. It is drawn taught, finishing the first loop. It is thenpassed around the lingual surface to the next interproximal space …theprocedure is repeated to form a quadrant of wire loops. The spacer isremoved and the loops are twisted two or three times to form an anchor legwhich is then turned apically.The disadvantages are the extensive manipulative technique, the restrictionsimposed by dental anatomy or disease and the need to replace the entiresection if a wire breaks.Physical properties of wire management: because many fixationtechniques require the use of wire, it is important to consider some of itsphysical properties. In the early days, gold, copper and silver wires wereused and more recently, soft alloys. Today these have limited applications.Currently stainless steel wires of 0.016 to 0.20 inches diameter are usedpredominately. Its ductility and flexibility make it very strong as well as bio-compatible and corrosion resistant.Prestretching and ‘working’ the wire increases its hardness and increases itslikelihood of breaking. Also, repeated heating makes it more brittle and likelyto break, so leaving the spool intact and re-autoclaving it over and over againwill weaken it. Air cooling instead of water cooling also adds to this problem.It is recommended to precut small amounts of wire and pre-autoclave these atmost, twice and discard small amounts left over after use. This may seemwasteful, but it is better than the frustration of repeatedly breaking wires andhaving to replace them.For uniformity of technique the wires are twisted in a clockwise direction.When tightening a constant outward pull will stop the tendency for the wire totwist upon itself and ‘work harden’ which is a frequent cause of breakage.Intramedullary and Trans-mandibular pins:The mandible is difficult to pin because of its curvature plus the otheranatomical features previously described. The mandibular canine toothobstructs direct rostral entry into the medulla. Caudal access is difficultwithout causing more soft tissue trauma. The method is less than useful withcomminuted fractures.
7Transmandibular pinning with or without wiring can be useful inunilateral and rostral (to the molars) fractures. Must be rostral to avoidentrapment of the tongue and its frenulum.Percutaneous pins:External fixators can be used in conjunction with percutaneously inserted pinsor screws to provide stabilization of fragments of both mandible and maxilla.An advantage of this type of fixation is that little iatrogenic soft tissue damageis required, it is also useful with unstable and/or bilateral fractures and whenbone has been lost.Threaded pins are less likely to loosen, and pre-drilling with a slightly smallerdrill or pin will make placement easier and more accurate. Place the pins withthe mouth closed and the teeth occluded. Care with heat production whendrilling bone as (heat) necrosis will allow the pins to loosen.Make sure the fixator pin ends have been blunted.Acrylic fixators are easier to use than the conventional Kirschner apparatusbecause the pins do not have to be all the same length or perfectly aligned.The difficulties encountered with this type of fixation is the displeasingappearance, the risk of them catching on furniture etc and that the owners willhave to keep them clean.Plates, Wire mesh and Screws:In theory these should provide rigid fixation; however their application requiressubstantial iatrogenic soft tissue damage and are difficult and time consumingto place. Contouring and molding to shape may be difficult.The cost of materials is high, as is the ancillary equipment list.In practice it is difficult to place these appliances because of the anatomy andcontouring the plates to attain good occlusion is often required. Plates mustbe placed ventrally in the mandibular body to avoid tooth roots. It is notalways possible to avoid the mandibular canal with screw placement but itmight be argued that the contents of the canal are already damaged by theinitial ‘insult’.In the repair of these fractures, the method of choice will always be theone that achieves the best stabilization with the least amount of soft(and hard) tissue disruption.Fractured teethExposed dentine is sensitive and porous, it is recommended to restoreenamel deficits with a composite material.If the enamel bulge is lost, for instance from the upper carnassial tooth, theresult is chronic insult to the gingival sulcus and this results in periodontaldisease. Restoration with a composite is possible but normal chewing forces
8can undo this work. A dog’s chewing forces, which are 8 times that of man,can even dislodge a crown.Endodontic exposure is, at least initially, painful. We often see our patientspresented with a fresh pulp exposure and the owners have to be convincedthat it is painful. Relating it to them personally sometimes works! Our patientsare very adept at masking painful conditions, this being part of their survivalinstinct.We have only two choices with the treatment of fractured teeth: extraction orendodontics.Fracture of the alveolus …teeth avulsionFracture of the lateral wall of the maxillary canine tooth alveolus is a commonpresentation resulting in lateral displacement (avulsion) of the tooth. Theseare often stable when reduced and interdental wiring with some composite tokeep in place is usually satisfactory.If ‘caught short’ in an acute canine tooth avulsion, it may be possible totemporarily hold it in place with a rubber band in a figure of 8 and a fewsutures.Endodontic treatment of the tooth can be done at the time, or left to a timemore appropriate to the patient.Fracture of the maxillaThese are often not as obvious as mandibular fractures and may be quite‘stable’. Few require fixation especially if displacement is minimal, they alsoheal rapidly.If malocclusion, marked deformity or obstruction of the nasal passages ispresent, intervention is necessary.The soft tissues surrounding these bones provide good support and nutrition.Problems occur when this relationship is compromised. Postponing surgeryuntil the soft tissue swelling has resolved is helpful.Sometimes a blunt probe inserted through the nose or small percutaneous K-wires will help elevate depressed fragments.Acrylic splints or palatine plates, interdental wiring alone, or to an intraoralsplint, can be used to stabilize some maxillary fractures.Use finer gauge wires (22-24 gauge) if using interfragmentary wires becauseof the ease of placement and adjustment.Be aware that leaving small detached, non-vital bone fragments may lead tochronic rhinitis or sinusitis.Transverse fractures of the rostral maxilla will be unstable and interdentalwiring will often be fixative.Fractures of the mandible
9Unilateral fractures are common and can usually be fixed with wire alone orin conjunction with acrylics. The wire may be placed interdentally or via stabincisions, through the bone (missing the tooth roots) and tightened over themucosa. Screws with a figure of eight wire would, if placed correctly, besatisfactory.Comminuted fractures are more difficult, are usually open and contaminatedand caused by more high-energy trauma. A tape muzzle may be satisfactoryif relatively stable and well aligned. Three to 5 weeks should be satisfactory.External fixators may also be suitable, with the rostral pin also beingtransmedullary.Fractures caudal to the teeth are less often diagnosed and are more difficultto manage because of inaccessibility. Fractures of the vertical ramus rarelycause malocclusion and often don’t need more than a tape muzzle ormandibular-maxillary wire for 2-3 weeks. This reduces pain and approximatesthe fragments.Fractures at or ventral to the condylar process may be treated likewise butinter-arcade wiring may assist. The ventral border is thicker and easilyexposed and internal fixation may be suitable. Avoid the mandibular artery.Bilateral fractures of the caudal mandible are not uncommon and because ofthe marked displacement, are more difficult to manage. Emergency care is atape muzzle. Pharyngeal entubation is helpful with treatment andvisualization. Unilateral fracture techniques can be adapted and sometimes aplate in the non-comminuted side converts a bilateral into a ‘unilateral’fracture.Pathological fractures occur more frequently in the mandible than in any otherbone. Periodontal disease in the aged, smaller breed dogs is largelyresponsible for this statistic.Iatrogenic fractures are usually unilateral as a result of dental extractionattempts in diseased bone.Dogfights may also place undue stress on disease compromised tissues.Avoid placing implants into adjacent diseased bone. Tape muzzles may besatisfactory.Nonunion of mandibular fractures is rare but more common in association withperiodontal disease where a fibrous union may form. In the older, toy breedsthat are only eating soft foods, veterinary interference may not be indicated.Soft tissue disruption may also contribute to this problem and infection and/orsequestration may be present.Leaving periodontally or peripically diseased teeth in the fracture site mayalso lead to infection.Separation of the mandibular symphysis
10This is the most common oral injury in cats (Harvey & Emily). Most can bewell stabilized with an encircling wire of 22-20 gauge placed with a 20-18gneedle as a wire-passer. If the fracture is comminuted, collapse of thesymphysis with distortion of the angle of the canine teeth may occur. Wireplus an acrylic splint could be useful or a more complex wiring technique withthe addition of a figure of 8 wire around the canines. If instability is a problem,then good occlusion can be attained by bonding the upper and lower canineteeth together for 2-4 weeks.In large dogs, further stabilization can be achieved by inserting a smalltransmedullary pin ventral to the second premolar.Fracture/luxation of the Temporomandibular Joint (TMJ)Fractures can be difficult to define clearly on radiographs and to treat in thedog and cat because of relative inaccessibility and the small size of the boneinto which implants can be placed.If there is little or no malocclusion or if highly comminuted, try a tape muzzlefor 4-5 weeks.If pain is severe or persists on opening the mouth, consider excision (excisionarthroplasty) of the mandibular condyle or the fragments.Often the soft tissues are severely disrupted and stability is poor so someform of alignment-fixation is recommended to maintain alignment. Interarcadewiring for 4 weeks may be considered.Luxation is seen more commonly in the cat than the dog and is frequentlybilateral. Adjacent bone may be fractured as the joints are well protected.If the luxation is rostro-dorsal, correction is aided by placing a wood dowel orpencil between the caudal teeth.
11Further reading:A Colour Atlas of Veterinary Dentistry & Oral Surgery. Kertesz P. 1993. WolfePublishing.Manual of Small Animal Dentistry. Crossley D.A. & Penman S. 2nd edn 1995.British Small Animal Association.Maxillofacial Trauma. Alling, C & Osbon, C. Chapter 5: Maxillofacial FractureFixation Prostheses, Methods & Devices. Brindley, P.Small Animal Dentistry. Harvey C.E. & Emily P.P. 1993. Mosby.Small Animal Oral Medicine & Surgery. Bojrab, M.J. & Tholen, M. 1990.Pliladelphia.Veterinary Dental Techniques. Holstrom S.E., Frost P. & Eisner E.R. 1992.W.B.Saunders