DEFINITION/OVERVIEW

Factures of the mandible, maxilla, and associated structures are classified as to location, severity (tooth involvement, soft tissue tears, and type of bone fracture), and effects of the muscles of mastication on reduction.

Effects of the Muscles of Mastication

The muscles closing the mouth typically help to reduce factures against the opposing jaws, unless they are also seriously involved. The muscles opening the mouth (primarily the digastricus) may reduce or displace a fracture (Fig. 46-1).

• Favorable: fracture reduced by muscles of mastication
  
• Nonfavorable: fracture displaced by muscles of mastication

Figure 46-1 Illustration comparing favorable (a) and nonfavorable (b) mandibular fractures.

(Courtesy of Dr. Robert Wiggs)

Classification of Symphyseal Injury

• Type I: separation, no break in soft tissue
  
• Type II: separation, break in soft tissue
  
• Type III: separation, break in soft tissues and comminution of bone; broken teeth not unusual

Teeth involved should be addressed and may be maintained during the bone healing process (i.e., endodontics or restoration), when possible. If required, they are extracted following bone healing. Occasionally, teeth may need extraction prior to fracture repair, but this may contribute to instability of the fracture line and affect attachment of splint materials.

Classification of Jaw Fractures by Location

• A: central incisors (mesial midline) to canine teeth (mandibular symphyseal separation is common secondary to trauma in young cats)
  
  
  
  • Note: mandibular symphyseal laxity is a common finding in cats and small dogs
  
  
• B: from canine to second premolar
  
• C: second premolar to first molar (carnassial tooth)
  
• D: from first molar to the angle of the mandible
  
• E: angle of the mandible
  
• F: coronoid process
  
• G: condylar process
  
• H: midline palate
  
• I: nonmidline palate
  
• J: massive or combination of fractures

ETIOLOGY/PATHOPHYSIOLOGY

• Injury, trauma, and predisposing factors
  
• Risk factors
  
  
  
  • High-risk environment or temperament (for injury)
    
  • Oral infections: may predispose to weaker jaws more prone to injury (i.e., osteomyelitis, periodontal disease)
    
  • Neoplasia: may predispose to weaker jaws more prone to injury
    
  • Metabolic diseases: certain metabolic diseases may predispose to weaker jaws more prone injury
    
  • Traumatic injury affecting the jaws or teeth
    
  • Congenital or hereditary factors resulting in weakened or deformed jaw bone

SIGNALMENT/HISTORY

• Can occur in dogs or cats
  
• No sex predilection
  
• No specific age predilection
  
• No breed predilection

CLINICAL FEATURES

• Vary greatly according to the location, type, extent (see above), cause, and underlying risk factors resulting in the injury
  
• Not uncommon to also have facial deformity, malocclusion, fractured teeth, oral or nasal bleeding, and inability to properly close the jaw

DIFFERENTIAL DIAGNOSIS

• Based on visualization, palpation, and radiographic findings
  
• Temporomandibular joint (TMJ) conditions (see Chapter 47)
  
  
  
  • Dislocations
    
  • Dysplasia
    
  • Fractures
    
  • Craniomandibular osteopathy (CMO) (see Chapter 13)
    
  • Ankylosis
    
  • Flaring of the coronoid process
  
  
• Tooth subluxation/luxation (interference with jaw closure) (see Chapter 48)
  
• Endodontic disease (tooth abscess, etc.)
  
• Foreign body lodge in or near the oral cavity
  
• Maxillary or mandibular nerve injury or disease
  
• Eosinophilic myositis
  
• Neoplasia

DIAGNOSTICS

• As required to assess and treat shock from initial injury
  
• As required to assess animal prior to surgery
  
• Oral exam
  
• Imaging
  
  
  
  • Intraoral radiographs
    
  • Extraoral radiographs (Fig. 46-2)
    
  • Computed tomography (CT) and magnetic resonance imaging (MRI)
  
  
• Neurological exam
  
• Biopsy with histopathology, if indicated
  
• A through and complete physical examination is very important in traumatic jaw injuries as many unseen or multiple injuries and complications are possible

Figure 46-2 Extraoral radiograph: good for survey films but lacks the detail of intraoral films.

THERAPEUTICS

Based on type of fracture, available equipment, supplies, and the doctor’s knowledge, comfort level, and experience. Treatment selection is based also on four major points:

Typical Types of Treatments for Classes of Fractures

• Interarch stabilization (typically for classes D, E, F, G, and J)
  
  
  
  • Tape muzzle
    
  • Cross-arch wiring
    
  • Composite fixation of cross-arch teeth (sometimes used in combination with dental pins)
  
  
• Intra-arch stabilization (typically for classes H and I)
  
  
  
  • Pin and wire combination
    
  • Dental wiring
    
  • Acrylic or composite splint
  
  
• Intraoral stabilization with splint: composite or acrylic splint (typically for classes A, B, C, H, I, and J)
  
• Intraoral stabilization with wire (typically for classes A, B, C, H, I, and J)
  
  
  
  • Interdental wiring: ivy loop, Stout’s multiple loop, Essig technique, and Risdon wiring technique
    
  • Dental wiring: circumdental used for anchorage for composite and acrylic splints (pigtails, cerclage, or twists)
    
  • Osseous wiring: circumferential, transosseous, transcircumferential
  
  
• Internal fixation (for most classes of fractures, but must be used selectively with consideration of teeth and roots): orthopedic wire, plates, screws
  
• External fixation (for most classes of fractures, but must be used selectively with consideration of teeth and roots): intramedulary (IM) pins with bars (stainless steel or carbon) or tubing (Penrose or other tubing) reinforced with composite or acrylic
  
• Combination of fixations (most classes of fractures)
  
• Salvage surgery condition (typically for class J fractures)
  
  
  
  • Condylectomy: nonrepairable factures of the TMJ
    
  • Cheiloplasty: salvage procedure to maintain reasonable mandible support in certain nonunion conditions
    
  • Rostral (or other) mandibulectomy: used in certain nonunion or massive injury conditions

Drugs

• Pain management (see Chapter 9)
  
  
  
  • Local anesthesia
    
    
    
    • Intraoral local blocks
      
    • Regional nerve blocks: mental nerve, mandibular nerve, infraorbital nerve, maxillary nerve
    
    
  • Injectables: butorphanol tartrate, buprenorphine, nalbuphine
    
  • Patches: fentanyl
    
  • Oral: carprofen, butorphanol tartrate, hydrocodone, and so on
  
  
• Antibiotics: broad spectrum based on history, health, and chemistry profile if deemed appropriate

Procedures

A few basic treatments are presented. However, many treatments are beyond the scope of this material and can be explored in the reading list. As with all fractures, the objectives of fracture reduction, reestablishment of normal occlusion and appropriate stabilization for the fracture, should be paramount. Any teeth that are or that became nonvital will need eventual endodontics (root canal therapy) or extraction once the fracture and jaw are stable.

• Warning: Acrylics give vapors that can be hazardous and should be used in well ventilated areas. In addition, acrylics generate heat during the thermochemical reaction during setting. Therefore, acrylics with a low thermal rating should be used when applied directly to the teeth. Otherwise, thermal injury to teeth may result in pulpitis that may be reversible or occasionally nonreversible resulting in the teeth becoming nonvital.
  
  
  
  • If acrylics are used, place the powder and liquid in a salt-and-pepper fashion in small increments to avoid hyperthermic reactions, until the desired shape and density of splint is attained.
    
  • Finish and smooth with acrylic bur on high-speed handpiece.
  
  
• Acrylic or composite splint: The use of acrylic is inexpensive, easy to obtain, and requires less expensive additional equipment in most cases. However, composites (i.e., Protemp™ Garant™, 3M ESPE, Pomona, CA) are generally easier to work with, have little exothermal reaction, have less odor hazards, and is this author’s preference and is the procedure described here.
  
  
  
  • The animal must be intubated. It may be preferred to place a pharyngostomy tube.
    
  • Cleanse the oral cavity with an oral chlorhexidine solution.
    
  • Inject local anesthesia appropriately.
    
  • Assess the fracture by visual, palpation, and radiographic means.
    
  • Soft tissue laceration of injuries should be appropriately cleansed and sutured.
    
  • Reduce the fracture in proper occlusion.
    
  • Bony voids or defects should be filled with osseoconductive, osseopromotive, or osseoinductive bone matrix materials.
    
  • Address any injured teeth. It is generally best to maintain injured teeth during the healing stage, when possible, as they provide additional anchorage for the splint. In addition, extracted teeth near the fracture line may cause bone void problems that may impede healing (Fig. 46-3).
    
  • Clean the teeth to which the splint is to be applied.
    
  • Polish the surface with flour of pumice and then rinse. It is best not to use standard prophy pastes for these as they contain oils, waxes, and fluorides that may inhibit conditioning of the enamel and dentin surfaces.
    
  • Intraoral wiring may be used in combination with the composite to establish an improved anchorage between the jaw and splint, and is generally recommended. Ivy loop, Stout’s loop, or simple pigtail wires may be used for anchorage to teeth in addition to the bonding agent. Pigtail wires are simply a loop of wire placed around the neck of a tooth just below the buccal bulge, and are a simple and highly effective means of placing wire anchorage. Some teeth have shapes that do not lend themselves to holding a wire near the gingival margin by natural retention. In these cases, a #2 or #4 round ball bur may be used to create a small retentive groove in the enamel. This groove should be kept shallow and in the enamel, if possible. This can be repaired by odontoplasty, bonding agents, and composites once the appliance is removed following jaw fracture healing.
    
  • Apply a 37% phosphoric acid to etch the teeth that the splint is to be applied. This will improve the attachment of the composite and allow for the use of a bonding agent if preferred.
    
  • Remove the acid after 30–60 seconds with a water rinse.
    
  • Dry the teeth with the air of the three-way air-water syringe. Well-etched enamel of teeth will appear to have a chalky appearance when the air is blown across them.
    
  • A dentinal or enamel bonding agent can now be applied to the acid-etched teeth. Although not always required, the bonding agent provides additional holding power for the splint to the teeth and is generally recommended. Follow the manufacturer’s instructions concerning application, as some are self-curing, while others require a curing light for setting of the bonding agent. Typically, the bonding agent is applied with a disposable applicator brush.
    
  • Apply a separator agent (boxing or rope wax, petroleum jelly, OraVet™, Merial, Duluth, GA) to the teeth of the opposite arcade or any teeth you do not wish the composite to adhere to. This is done to prevent the composite from bonding to these teeth during the occlusal stage and bonding the mouth shut during the setting stage.
    
  • Place composite cartridge (Protemp 3 Garant) in syringe gun.
    
  • Remove cartridge tip seal or old mixing tip.
    
  • Place new mixing tip. Each product has different mixing tips, and how they are properly attached. Always check the instructions for the product you purchase to know how to properly attach the tip. Some screw on, others twist on. Some have a notch on one side of the attachment base that must be properly aligned for the unit to work properly and not contaminate the remaining material within the tube resulting in the entire cartridge setting up in a short period of time.
    
  • Pull the dispensing trigger of syringe gun to begin expressing the catalyst and base in the composite cartridge through the mixing tip.
    
  • If a “new” tube is being used, the first few millimeters of material coming from the mixing tip should be thrown away as it may not have a proper mixture.
    
  • Rapidly apply the composite as it comes from the mixing tube tip directly to the area decided upon for the splint.
    
  • Once the full thickness of composite desired has been applied, the teeth should be quickly placed into articulation with the opposing teeth in order to assure that there will be no occlusal interferences once the splint hardens. The tip should be left on the cartridge for storage. The material in this tip will harden, protecting the remainder in the cartridge.
    
  • Excess or rough areas of splint can be removed with a white stone or fluted bur on a high-speed handpiece or an acrylic bur on a straight handpiece, or with a bone file if a dental unit is not available.
    
  • To further smooth the surface of the splint, a layer of unfilled resin can be applied to the surface of the composite of the splint (self- or light-cure; cure as required).
  
  
• Circumferential osseous wiring or suturing (wiring around the bone; used most commonly for symphysis separations) (Fig. 46-4)
  
  
  
  • 20- or 18-gauge needle used as wire passer
    
  • 24–28-gauge wire, in small breeds or cats, absorbable (long acting) or nonabsorbable 1 to 2-0 suture material can sometimes be substituted for wire
    
  • Run wire from stab incision (ventral midline intermandibular space) to vestibule; pass behind canines, down through vestibule on opposite side, and back down through the ventral incision
    
  • Tighten wire to reduce fracture, but do not overtighten the wire ends or the teeth may be pulled too far medially (base-narrow) and hit the palate
    
  • If teeth go base-narrow, either loosen the wire ends or place a second figure-8-shaped wire lopped around the canine teeth and subgingivally under the mandible
    
  • Finishing twist can be extra or intraoral (intraoral finishing twists may need a protective coating of acrylic or other material to prevent wire ends from irritating the oral tissues)
  
  
• Additional treatment considerations
  
  
  
  • Bone graft: use for any class of fracture for areas of bone loss to reestablish structural stability
    
    
    
    • Autograft: bone graft from same individual
      
    • Allograft: bone graft from same species (Osteoallograft, Veterinary Transplant Services, Kent, WA)
      
    • Alloplast: artificial graft material (e.g., Consil, Nutramax Labs, Edgewood, MD, or Osteoallograft)
      
    • Xenograft: graft material from another species
    
    
  • Teeth in the fracture line should be maintained by appropriate treatment until the fracture heals, if possible, as removal may result in additional fracture stabilization problems and reduced splint anchorage
    
  • Awareness of occlusion, tooth roots, and anatomy during treatment is critical
    
  • Treatment with composite/acrylic splints in association with wiring is generally very effective; may allow for improved occlusal reestablishment and less dental trauma
    
  • Pharyngostomy tube aids in occlusal checks intraoperatively

Figure 46-3 While the first molar on the left mandible of this young dog will eventually need extraction, for stabilization of the jaw fracture initially, it should be maintained for additional anchorage for any fixation method, including splints.

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