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Mark M. Smith, VMD, Diplomate ACVS, Diplomate AVDC Professor, Laboratory for Comparative Oral Research and the Department of Small Animal Clinical Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, Virginia EXODONTICS
Exodontics is the practice of tooth extraction. The most common indication for exodontic therapy in dogs is severe periodontal disease. Endodontic therapy is recommended for teeth affected by crown fracture exposing pulp, and pulpitis. However, it is not unusual to perform exodontic therapy when there is minimal crown available for restorative techniques, or when the owner does not authorize endodontic therapy. Exodontic therapy may also be used as a component of treatment for malocclusion. Simple Exodontics The periodontal ligament attaches the tooth to the bony alveolus or socket. The goal of exodontic therapy is to disrupt the periodontal ligament allowing movement of the tooth out of the alveolus. This component of the exodontic process is performed with periodontal elevators. There are various sizes and grip configurations for periodontal elevators. In dogs, basic periodontal elevators include instrument numbers 301s, 301, and 401. 1 After the gingival attachment fibers are severed with a small scalpel blade, the periodontal elevator is inserted into the potential space between the tooth and alveolar bone. Initially, the elevator is rotated in the periodontal space to fatigue and tear the periodontal ligament. The position of the rotated periodontal elevator is maintained for 10 seconds to accomplish this goal. This maneuver is performed around the circumference of the coronal aspect of the root. As the exodontic procedure continues apically, the blade of the periodontal elevator is placed parallel to the root surface; the handle is dropped to be perpendicular to the long axis of the root; and the blade is turned 90 degrees. This allows the edge of the elevator to engage the side of the root and "elevate" the root from the alveolus. Again, after movement is maximized, the position of the periodontal elevator is maintained for 10 seconds. Progress during the exodontic procedure will be noted by increased movement of the root and crown as the periodontal space expands secondary to hemorrhage and disruption of the periodontal ligament. Controlled force and patience will allow most single-rooted teeth or tooth segments to be extracted with periodontal elevators and digital manipulation. Extraction forceps are used only after the tooth is so mobile that the clinician considers the tooth or tooth segment removable with digital manipulation. The extraction forceps should engage the tooth as far apically as possible in order to decrease leverage forces on the root which could lead to root fragmentation (Fig 1). Generally, these non-surgical techniques are effective for incisors, first premolars, and third molars regardless of the health status of the periodontium. Multi-rooted teeth with periodontal disease and secondary mobility may be extracted using similar techniques. Complicated Exodontics Non-mobile, multi-rooted or canine teeth are considered difficult or complicated teeth to extract. This fact is based on the size or complexity of the root system and sufficient periodontal attachment to prevent mobility even when there is substantial periodontal disease. Periodontally disease-free teeth with endodontic disease or malocclusion may be particularly difficult to extract based on having normal periodontal attachment. Surgical techniques are usually required for exodontic therapy of these teeth. Principles for surgical exodontic therapy include periodontal flap elevation, removal of alveolar bone to partially expose the root(s), sectioning of the crown in multi-rooted teeth, crown/root segment elevation, alveoloplasty to smooth rough bone edges, and suturing of the periodontal flap over the alveolus. These principles will be highlighted in the following paragraphs describing surgical exodontic techniques for the maxillary fourth premolar, mandibular first molar, maxillary canine, and mandibular canine teeth. Maxillary Fourth Premolar The maxillary fourth premolar is a tri-rooted tooth with a large distal root and 2 mesial roots (mesiobuccal and mesiopalatal) emanating from a common root trunk. The procedure begins by using a # 15 scalpel blade to incise a mucogingival periodontal flap. The mesial and distal incisions are made along the line angles of the tooth. Care should be taken to avoid the gingiva at the distal aspect of the maxillary third premolar and the mesial aspect of the maxillary first molar. Dorsal length of the incisions are dependent upon the size of the tooth, usually extending between 1.5 and 2.5 cm. As the mesial incision is advanced dorsally, another area to avoid is the infraorbital foramen which can be palpated through the mucosa between the maxillary third and fourth premolars. The infraorbital artery and nerve exit this foramen as they course in a rostral direction. After these vertical incisions are made, gingival fibers are incised from their attachment using either a # 15 scalpel blade or a small, sharp periosteal elevator. The gingiva is thin and easy to perforate when using a sharp instrument. The technique of placing the scalpel blade parallel to the tooth surface and below the gingiva, followed by short stab and prying motions is an effective way to elevate this tissue. As the mucogingival line is approached, a sharp periosteal elevator is used to elevate the buccal mucoperiosteum completing the flap. Alveolar bone is removed from the buccal aspect of the distal and mesiobuccal roots using a high-speed handpiece and a round or pear-shaped bur. Usually the coronal one-half to two-thirds of the root is exposed by using light hand pressure to bur away this thin bone. During the alveolectomy process, it is helpful to drill slots on the mesial and distal aspects of these roots. Such bony slots provide a location to place the periodontal elevator. An analogy for this maneuver might be a toe-hold during mountain climbing. During the alveolectomy, developing these "toe-holds" for the periodontal elevator will speed the extraction process. If a high-speed handpiece is not available, other instrumentation may be used for alveolectomy including bone file, rongeurs, curette, or a hobby drill with a sterilized round bur. Crown sectioning is performed using a tapered-fissure or crosscut bur. The critical landmarks for crown sectioning are the buccal and mesial furcation entrances. Using these landmarks ensures crown sectioning with one root per crown segment (Fig 2). An exact "hemisection" is not necessary, however the crown must be completely cut beginning at the furcation entrances indicated. If a high-speed handpiece is not available, other instrumentation may be used for crown sectioning including a hobby drill, hack saw, or large bone cutter. This latter instrument will likely shatter the crown however crown integrity is not an important factor; only separation of the crown at the furcation. The crown/root segments are elevated and removed using simple exodontic techniques described previously. Since the buccal alveolar bone has been removed, the crown/root segments are not elevated as much as luxated in a buccal direction. Therefore, this maneuver is easier with removal of increased amounts of buccal alveolar bone. Following removal of the crown/root segments and confirmation that the roots have been completely removed, sharp bony edges are reduced (alveoloplasty) using a high-speed handpiece and a round or pear-shaped bur. Other instruments may be used for alveoloplasty as described for alveolectomy. Alveoloplasty minimizes perforation of the periodontal flap by sharp bony edges. It also removes edges of bone which would quite likely require resorption during osseous healing. Dilute chlorhexidine (0.12%) may be used to lavage the wound followed by positioning of the periodontal flap over the extraction site. The flap is sutured to the buccal mucosa and mucoperiosteum of the hard palate using chromic gut or polyglactin 910 in a simple interrupted pattern. Polydioxanone is not recommended because of its prolonged resorption time which is not necessary for routine oral wounds. Space is provided between individual sutures so that drainage may occur from the extraction site. Mandibular First Molar Similar exodontic techniques are used for the mandibular first molar as the maxillary fourth premolar. The periodontal flap, lateral alveolectomy, and alveoloplasty are performed as described previously (Fig 3). It should be noted that when compared with alveolectomy of the maxillary fourth premolar, the thickness of bone on the buccal aspect of the mandibular first molar is substantially greater. Crown sectioning is also recommended for this tooth with the shortest path being through the crown from the furcation in a distal direction. Lateral alveolectomy, visualization of the mesial and distal roots, and controlled root elevation decrease the incidence of iatrogenic mandibular fracture. Maxillary Canine The maxillary canine is a large, single-rooted tooth which is difficult to extract using non-surgical techniques. Canine teeth affected by severe periodontal disease may be extracted using non-surgical methods, however if the tooth has a healthy periodontium, it is essential to implore surgical exodontic techniques. It is important to note that the root of the maxillary canine courses in a dorsal and distal direction with its apex directly above the mesial root of the maxillary second premolar. The periodontal flap incision begins in the buccal mucosa over the maxillary second premolar and is directed mesially, sloping towards the gingiva at the distal line angle of the canine tooth. The gingival attachment fibers are incised along the canine tooth in a manner described previously. The flap incision is completed with a vertical relief incision from the gingiva along the mesial line angle approximately 3/4 the length of the canine tooth root (Fig 4). Following gingival elevation, the buccal mucosa is relatively easy to mobilize from the buccal alveolar bone. An alternate flap design includes a peninsula-shape flap with mesial and distal incisions over the tooth's line angles (Fig 4). Generally, regardless of flap design, the flap is sutured over bone. Therefore, the alveolectomy should be offset when compared with the periodontal flap. Lateral alveolectomy is performed using methods described previously. The alveolectomy begins near the cementoenamel junction and continues apically along the canine root (Fig 4). The cementum has a tan color and is readily identified compared with the hemorrhagic alveolar bone on the mesial and distal sides of the tooth. During the alveolectomy process, it is helpful to purposely make gauges or slots in the alveolar bone on both the mesial and distal aspects. These focal areas of bone loss provide locations for application of the periodontal elevator (Fig 4). The canine root is elevated with the tooth being displaced in a lateral or buccal direction. If the angle of buccal displacement is acute, the root apex may fracture through the thin alveolar plate of bone separating the alveolus from the nasal cavity. If fracture leading to perforation occurs, hemorrhage may be noted from the ipsilateral nares. This problem is treated by primary wound closure of the periodontal flap over the alveolus. Incising the periosteum at the base of the periodontal flap improves flap mobility and decreases wound tension during primary closure (Fig 5). Mandibular Canine A buccal (lateral) approach has been recommended for surgical extraction of the mandibular canine tooth.2-5 This approach requires consideration of anatomic structures including the prominent soft tissue attachment (frenulum) of the lip, the neurovascular structures exiting the mental foramen, and the roots of the first and second premolar. Considering the orientation of the root of the mandibular canine tooth is in a lingual (medial) direction, it would seem appropriate to consider an approach that could be performed directly over the root. Such an approach would avoid disruption of lip frenulum, potential hemorrhage from the mandibular artery and vein at the mental foramen, and iatrogenic trauma to adjacent tooth roots. A lingual approach for surgical extraction of the mandibular canine tooth has been developed based on anatomic observations of tissues and structures of the rostral mandible and lingual orientation of the mandibular canine tooth root. 6 The initial component of the procedure is elevation of a lingually based, full-thickness, mucoperiosteal flap. The flap is based on the symphyseal surface near the mandibular symphysis (Fig 6). The flap apex includes the gingiva of the lingual aspect of the mandibular canine tooth. Generally, the flap base is approximately twice the width of the flap apex. A nitrogen-powered dental unit with a high-speed handpiece and round bur are used to perform lingual alveolectomy (Fig 6). Length of alveolectomy ranges from 10-20 mm in dogs. Periodontal elevators and extraction forceps are used to complete the extraction. The remaining alveolus is lavaged with 0.12% chlorhexidine and the flap is apposed to the buccal gingiva using 3-0 polyglactin 910 in a simple interrupted pattern (Fig 6). Multiple Extractions Extraction of multiple teeth in sequence is often required. It is important to consider which of the involved teeth would likely be the most difficult to extract and use adjoining teeth to aid extraction of the most secure, difficult tooth in the sequence. For example, if the maxillary fourth premolar, first, and second molars require extraction; the second molar will be easiest and the fourth premolar most difficult to extract. Therefore, since the first molar is being extracted, it may serve as a lever fulcrum for the periodontal elevator in extraction of the fourth premolar (Fig 7). Likewise, the crown of the second molar may be used as a lever fulcrum to aid extraction of the first molar. It would be a mistake to extract the molars first, and lose any mechanical advantage they could provide to aid extraction of the fourth premolar. However, the clinician should keep in mind that when removing a single tooth, crowns of adjoining teeth are not used as fulcrums to avoid crown damage. Retained Deciduous Canine Teeth There should be no doubt which canine tooth is retained and which is permanent. The retained maxillary canine tooth will always be distal to the permanent canine, while the retained mandibular canine tooth will be buccal or lateral to the permanent canine (Fig 8). Exodontic treatment of the retained deciduous canine tooth should be performed whenever the deciduous and permanent teeth are present at the same time. This recommendation is based on the fact that both teeth are in competition for the same dental space. If deciduous canine extraction is not performed in a timely manner, malocclusion of the permanent canine teeth is likely. Generally, instruments and techniques for exodontic therapy of deciduous canine teeth are the same as those described previously. The principal differences involve the care and atraumatic emphasis used when extracting these teeth to avoid damage to the successional permanent tooth. Although damage which may affect crown/root development is less likely since the permanent tooth has erupted, the operator should perform exodontic manipulations and surgical techniques as far away from the permanent tooth as possible. Postoperative Care Postoperative care includes feeding soft food for 7-10 days. Additional pain relief may be gained by administration of analgesic therapy. This may be particularly indicated for patients having had multiple or surgical exodontic treatment. A broad-spectrum antimicrobial may be administered for 10-14 days especially in patients with concurrent gingivitis/stomatitis or local osteomyelitis at the extraction site. Complications Associated with Exodontic Therapy
Fragmented Roots Fragmented roots may occur secondary to crown or maxillofacial trauma. However, the most common etiology of root fragmentation is iatrogenic during exodontic therapy. The diagnosis is made following evaluation of skull or dental radiographs for patients having received trauma (Fig 9). Radiographs may also aid diagnosis of root fragmentation during exodontic therapy, however other indicators are obvious during the procedure. Often the clinician will hear an audible crack. Upon inspection of the extracted tooth, an apical root defect will be apparent with the remaining root having a jagged edge (Fig 10). Normally, the root apex has a rounded appearance. Using suction or a cotton applicator to visualize the fragmented root within the alveolus, the remaining root fragment will appear tan in color with a centrally located root canal. Alveoli without root fragments well-up with hemorrhage similar to ink wells. Alveoli with root fragments tend to have less hemorrhage due to presence of the root. Treatment of fragmented roots require continuation of exodontic techniques to remove the root fragment. Periodontal elevators with a narrow working blade surface or special root fragment elevators may be used to facilitate root fragment elevation. If a high-speed handpiece is available, further alveolar bone may be removed with a round or pear-shaped bur to outline the root fragment making elevation easier (Fig 10). Another treatment option includes using the same instrumentation to obliterate the root fragment. The root fragment is harder than the surrounding alveolar bone, therefore tactile perception is necessary to determine when the root fragment has been obliterated. A radiograph may be taken of the extraction site to confirm removal of root fragments (Fig 10). The only situation in which root fragments may not be removed is when there is an overriding concern that harm may be inflicted on the patient by pursuing root fragment removal. Root fragments which are not removed are less likely to be associated with chronic infection if the blood supply from the apex is intact and the root fragment is not affected by disease. If a root fragment(s) is not removed, the owner should be informed that the extraction was complicated necessitating root fragment retention, and that diligent monitoring for clinical signs associated with infection is required. A draining tract or swelling secondary to abscessation are likely clinical signs related to retention of root fragments. Whether secondary to crown or maxillofacial trauma (Fig 11), or complications of exodontic therapy, root fragments should be removed using similar techniques as described previously. However, a specific surgical procedure may be required to access the root fragment(s) similar to surgical procedures for exodontic therapy. All too often "wait and watch" is advised to the owner with regards to treatment of retained, fragmented roots following trauma. Relative early treatment is advised since the exposed root pulp would be expected to be quite painful. Pulpitis is inevitable secondary to pulp contamination by oral bacterial flora with periapical abscessation a possible sequelae. If the patient requires general anesthesia for oral fracture or soft tissue repair, retained roots should be removed during the same anesthetic episode. The procedure may also be scheduled as a component of a professional teeth cleaning procedure at an appropriate time following patient stabilization. In summary, a "wait and watch" attitude should only be at the request of the owner and not recommended by the veterinarian. Iatrogenic Mandibular Fracture Iatrogenic mandibular fracture may occur when performing exodontics of any tooth of the mandibular dental arcade, however it is most commonly associated with the mandibular first molar or the mandibular canine (Fig 12). Fracture associated with extraction of the mandibular first molar usually occurs when simple exodontic techniques are used when there is apparent severe periodontal disease with deep periodontal pockets. The clinical signs of periodontal disease may mislead the clinician into believing the tooth is mobile and easy to extract. Even when the destructive periodontitis is severe, the tooth is usually not mobile relating to the large root surface area which may continue to have substantial periodontal attachment. Destructive periodontitis may also result in such severe periodontal bone lysis that the ventral mandible is thin and prone to fracture during relatively routine exodontic maneuvers. Finally, older patients requiring extraction of the mandibular first molar may have age-related osteopenia which may also contribute to the incidence of fracture. Similar underlying periodontal or age related changes contribute to iatrogenic fracture of the rostral mandible during mandibular canine extraction. Pre-procedure intraoral or standard radiographs will show bone lysis secondary to periodontal disease (Fig 13). Information gained from radiographic assessment of teeth to be extracted aid the clinician in being able to warn the owner about potential complications during exodontic therapy. Surgical techniques as described previously decrease the incidence of fracture regardless of the amount of bone lysis. This is related to the controlled force and emphasis on buccal or lingual luxation recommended during surgical exodontics. If the clinician is concerned about fracture during normal alimentation following extraction, bone alloplastic materials may be placed in the alveoli prior to wound closure. I have not used these materials following exodontic therapy and have not had patients have subsequent mandibular fracture despite relatively aggressive bone removal to aid extraction. Pre-procedure radiographs and owner consultation allow easier explanation of the complication of iatrogenic mandibular fracture. Owner compliance and permission for fracture treatment is enhanced when the fracture is perceived as a complication and not a "mistake". As with other fractures, treatment options for iatrogenic mandibular fracture are limited to repair or salvage techniques. Repair techniques may be associated with delayed or non-union based on the factors mentioned previously: geriatric patient, osteopenic bone, destructive periodontitis. In fact, fibrous union is not an unusual outcome. Therefore, the clinician must weigh the likelihood of a positive clinical outcome from successful repair as a result of bony union with that from a salvage, resective procedure. It has been documented that canine patients receiving rostral mandibulectomy or rostral hemimandibulectomy for treatment of neoplasia have a good clinical outcome with respect to prehension and mastication of food. 7 These resective surgical procedures may be appropriate for treatment of iatrogenic mandibular fracture based on expectation of a positive outcome, inexpensive cost, low complication rate, and the provision of immediate, definitive therapy for the complication. Ocular Trauma Iatrogenic trauma to ocular structures may occur during extraction of the maxillary fourth premolar, first molar or second molar (Fig 14). The cause of such trauma is related to the thin alveolar bone and ventral floor of the orbit (Fig 15). These structures are adjacent to the caudal maxillary teeth and may be perforated by a pointed instrument such as a periodontal elevator especially in patients with destructive periodontal disease. This complication is preventable by using controlled force and a palm grip on the periodontal elevator with fingers placed near the working end or tip of the instrument. This grip limits accidental penetration of the instrument to the distance between fingers and the tip of the instrument. Panophthalmitis may result from perforation of the globe by the periodontal elevator. If antimicrobial and anti-inflammatory treatment fail, enucleation is an unfortunate result. Infection Infection of the extraction site following exodontic therapy is an unusual complication. The localized osteitis is related to the trauma of the extraction, disruption of blood supply, and bacterial contamination of exposed bone. Lavage of the extraction site with 0.12% chlorhexidine followed by primary wound closure as described previously will minimize the incidence of infection. An extraction site which appears non-healing within 7 days or more following surgery is abnormal and not necessarily related to infection. The non-healing area should be considered for biopsy to rule-out the possibility of neoplasia such as squamous cell carcinoma. Localized osteomyelitis may be secondary to severe periodontitis (Fig 16). The affected tooth and periodontium are the focus of the infection with the maxilla or mandible showing clinical signs of osteomyelitis. Exodontic therapy of the tooth alone is not sufficient to treat this problem. Additional procedures which are required include elevation of a periodontal flap and removal of necrotic bone with bone rongeurs or a round bur on a high-speed handpiece (Fig 16). The bone may be submitted for bacterial culture however the result will be polymicrobic and difficult to interpret. Thorough debridement of necrotic bone followed by administration of a broad spectrum antimicrobial is usually sufficient treatment (Fig 16). References
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EMERGENCY MANAGEMENT OF CROWN TRAUMA
Crown fracture in dogs and cats is a relatively common problem secondary to blunt trauma to the oral cavity. An uncomplicated crown fracture involves the enamel and dentin but does not cause pulpal exposure. A complicated crown fracture involves enamel and dentin, and exposes the pulp. Trauma which does not cause crown fracture may deleterious affect the tooth. Concussive and luxation injuries may disrupt the vascular supply to the tooth causing pulpitis and devitalization of the tooth. Anatomy and Pulpal Pathophysiology The inner part of the crown is referred to as the pulp chamber. The root canal extends from the pulp chamber apically in each root. The pulp occupies the pulp chamber and root canal (s). The pulp is composed of soft connective, vascular, and nerve tissue. Cell types within the pulp include odontoblasts, fibroblasts, fibrocytes, collagen fibers, elastic fibers, blood vessels, and nerves. Odontoblasts are the cells responsible for the formation of dentin, which comprises the majority of the mature tooth structure. Pulpitis is the inflammation of the pulp which causes clinical signs of pain. Pulpitis may be reversible, however in veterinary medicine pulpitis is most commonly diagnosed after it has caused pulp death and a nonvital tooth. The sequelae associated with pulpitis is dependent upon the type of trauma or inciting cause, whether the crown is fractured exposing the pulp, and the maturity of the tooth. Regardless of etiology, the pulp undergoes inflammation resulting in pulp edema and an inflammatory cellular response. A negative inflammatory cycle may occur with continued small artery perfusion, edema, and venule obstruction related to the pulp's location in a confined space. Increased vascular pressures within the tooth stimulate pain receptors. A large pulp chamber and canal(s) of the immature tooth enable a greater incidence of reversible pulpitis, especially if the apex is open. This more favorable prognosis is based on greater space to accommodate edema and elevated pressures. Pulp cavities in the older dog and cat are constricted and narrow diminishing the tooth's ability to favorably respond to inflammation. Crown fracture which causes pulp exposure not only incites pulpal inflammation, but also exposes the pulp to the oral environment. Healing does not occur spontaneously. Pulp necrosis results with bacterial infection playing a dominant role. Similar to inflammation in any wound, hemorrhage and an appropriate inflammatory response is followed by fibrin formation. Pulpal hyperplasia (pulp polyp) similar to granulation tissue may form or necrosis and pulpal abscessation may occur within days of the injury. Pulp hyperplasia is indicative of maintained vascular supply and an appropriate inflammatory response associated with a more recent injury. Complicated Crown Fracture Treatments for a complicated crown fracture include root canal therapy or vital pulpotomy (pulp capping). Each procedure would be followed by crown restoration. However, the procedures themselves are different and dependent upon the patient's history and oral examination. Vital pulpotomy is performed when the crown fracture and subsequent pulp exposure are recent. The two primary prognosticating factors associated with recommending this procedure are maintained vascular supply to the pulp via the root apex or apices, and minimal bacterial contamination along the pulp canal (s). Therefore, recent injuries in teeth of relatively young dogs are the best candidates for vital pulpotomy. Older patients with constricted pulp cavities may be best treated with root canal therapy even if the injury is recent since functional vascular supply is so critical for this procedure to be successful. If vital pulpotomy fails, the tooth then becomes a candidate for root canal therapy or extraction. Therefore, if the owner is aware of the complications and possibility of a second procedure, vital pulpotomy is a viable treatment option even in the older patient. Obviously, since bacterial contamination is likely based on duration of pulp exposure, the procedure should be performed as soon as possible. A set time frame is not advised since a young patient with prolonged exposure (days) of the pulp and moderate to severe contamination may respond as well as an older patient seen within hours with a minimally contaminated pulp. Experimental studies have shown that exposed pulp remains viable up to 7 days following pulp exposure secondary to fracture. Pulp inflammation generally extends approximately 2 mm from the fracture site. Bacterial contamination and pulp necrosis occurs when food and debris are plugged into the pulp preventing the self-cleaning effects of saliva. Although each case will be unique and must be evaluated independently, many patients with complicated crown fracture will be candidates for vital pulpotomy if the fracture orientation allows self-cleaning and the pulp appears "healthy". Unfortunately, in veterinary medicine the actual time of the trauma is not known with patients often presented with evidence of chronic pulp exposure. These patients are not candidates for vital pulpotomy. Treatment (root canal therapy or extraction) is still necessary, but not urgent. Vital pulpotomy is a procedure whereby the coronal aspect of the pulp is removed. It is hoped that the most contaminated area of the pulp is included in the resected pulp. The remaining pulp is treated to maintain its vascular supply and tooth viability. The remaining vascular supply will be responsible for healing of the pulp at the resection site and for continued maturation of the tooth, including dentin development if necessary. A thorough periodontal examination should be performed to determine the presence of moderate to severe periodontal disease which may jeopardize tooth maintenance. Radiographs of the tooth should be taken to verify no evidence of substantial periodontitis, periapical infection, or root fracture which would change the treatment plan. Supporting bone should be evaluated for alveolar fracture which may require treatment. The procedure begins by rinsing the fractured crown and surrounding periodontal tissues with 0.2% chlorhexidine. Sterile instruments and dental burs are used for the remainder of the procedure. A sterile glove may be placed over the fractured crown. A small incision in the glove will expose the crown while providing a relatively aseptic surgical field. A sterile round or pear-shaped diamond bur similar to the size of the root canal is placed in a high-speed handpiece using aseptic technique. The pulp is removed using the bur under water irrigation for a distance of approximately 7 mm. The result should be removal of the pulp and hemorrhage from the crown fracture site. Hemostasis may be achieved with a moistened sterile paper point placed in the pulp canal/chamber or a sterile paper point with calcium hydroxide applied to its pointed end and place directly on the pulp. If the pulp fails to hemorrhage, the tooth is nonvital and should be extracted or receive root canal therapy. If hemorrhage persists after 5 minutes, further pulpotomy may be required to remove additional inflamed pulp; or, pulp filaments remain at the bur site and require removal using a spoon excavator. The viable pulp is treated with a 2 -3 mm layer of calcium hydroxide after hemostasis is achieved. A cement base is applied after the calcium hydroxide has hardened followed by crown restoration with a composite material. Radiographs of the tooth should be performed semiannually for 2-3 years postoperatively, and then annually for the remainder of the patient's life. During the follow-up period, the crown should not become painful or discolored. Radiographs should show an area of calcification (dentin bridge) at the pulp-restoration interface and no evidence of periapical pathosis demarcated by osteolysis at the tooth apex. Dentin development should be the same as the contralateral, matching tooth. A prosthetic crown may be manufactured and applied after clinical and radiographic evidence of pulpal healing. Chronic crown fractures do not require immediate treatment. Chronic crown fractures may have gross food and debris within the fracture site. Odor from the tooth may be fetid. Dental radiographs may show evidence of periapical pathosis indicative of a nonvital tooth. Periodontally disease-free, nonvital teeth are candidates for root canal therapy or extraction. Tooth Luxation Extrusive luxation is the peripheral displacement or partial avulsion of the tooth. The canine teeth are most commonly affected. The apex of the tooth is displaced and alveolar bone is often fractured. The force and direction of impact determines the direction of the luxation. Radiographs of the tooth should be performed to determine if there is root fracture, and to assess the amount of fractured alveolar bone. Radiographs will show an increased width of the periodontal space at the apical aspect of the tooth in cases of extrusive luxation. This type of injury often results in pulp necrosis in the mature tooth. The immature tooth may develop partial pulp necrosis limited to the coronal aspect due to an open apex and greater vascular supply apically. If revascularization of the pulp occurs, or if the pulp survives, there is a high incidence of negative pulp changes. These changes are secondary to a revascularization process which may contribute to internal root resorption followed by deposition of cacified tissue (dentin) which causes partial or complete pulp canal obliteration. Therefore, owners should be advised that the first step of treatment is to reduce the luxation, with a subsequent treatment plan usually including root canal therapy. If the owner declines the possibility of root canal therapy, tooth extraction should be offered. Treatment of the mature tooth begins with reduction using digital pressure as soon as possible. A splinting procedure is performed following tooth reduction in order to prevent further pulp damage and to stabilize the tooth during the initial healing period. Splint application should: be immediate and directly applied; atraumatic; restore normal tooth position; provide adequate fixation; not interfere with occlusion; not damage soft tissues; and, not interfere with endodontic therapy. Acrylic splints fulfill the aforementioned requirements. The procedure begins by thorough cleansing of the crown after the tooth has been reduced. Anchorage teeth (usually the opposite canine tooth) are also cleaned. The tooth surface which will receive the acrylic is acid etched with 40% phosphoric acid gel for 1 minute followed by rinsing with water. This procedure results in 30-50 micron porosities in the enamel which will aid adherence of the acrylic to the enamel. Effective acid etching results in a tooth surface which has a "chalky" appearance. The tooth is dried and the acrylic is applied. Acrylic is applied to the affected tooth and the anchorage tooth with a bridge formed across the mandibular symphyseal mucosa or hard palate mucosa. Orthopedic wire (22g) between the teeth may be applied first to support the acrylic. A cold-curing acrylic (Pro-temp Garant-ESPE) is recommended to reduce injury which may be related to acrylics which produce an exothermic reaction. The owner should be instructed in oral hygiene since warm water lavage around the splint will minimize food accumulation and subsequent gingivitis. The splint should be maintained for 2-3 weeks; 3-4 weeks if there is associated alveolar fracture. The tooth should be monitored for signs of pulp necrosis which should be evident 2 weeks following injury. Root canal therapy is recommended as soon as color changes indicative of pulp necrosis are confirmed and the tooth has been stabilized (2 weeks). Exarticulation or complete luxation is diagnosed when the tooth is totally displaced out of the socket or is attached only by gingiva. The periodontal ligament is usually split with part remaining with the tooth and part attached to the alveolus. Preservation of the cells of the periodontal ligament is critical for successful replantation. Cell viability is greatly reduced after 2 hrs of exposure to air. Therefore, dogs and cats with complete tooth avulsion should be examined immediately. The owner should be instructed not to wash the tooth in any way; simply place it in milk, which serves as an excellent emergency transport medium. Rinsing the tooth with tap water is detrimental to periodontal cells. The clinician should remove gross debris by rinsing the tooth with saline. The tooth and alveolus should not be debrided. The clot should not be removed from the alveolus. It will be displaced once the tooth is replanted. The maneuver is performed digitally with the patient heavily sedated. A splint is applied as described previously and maintained for 10 days-2 weeks. The vascular supply to the tooth is severed secondary to the injury necessitating root canal therapy 2 weeks following replantation in order to prevent the development of inflammatory root resorption. Concussive Injury Pulpitis independent of crown fracture is usually secondary to blunt trauma directly to the tooth. A thorough oral examination and radiographs should be performed to document that the tooth is in normal position and has not undergone intrusive trauma. This type of trauma forces the tooth in an apical direction, driving the tooth into the bone and is a form of tooth luxation. Perceptible tooth movement is not present. Pulp injury is diagnosed based on color changes within the visible crown. These color changes occur within hours of the trauma indicating to the clinician that the viability of the pulp is in jeopardy. Initially, hemoglobin break-down products enter the dentin tubules and enamel. As the hemocomponents degenerate, the initial pinkish color appears grey-blue through the enamel. This color change to grey-blue occurs approximately 2-weeks after pulp injury and indicates pulp necrosis. Tooth sensitivity to percussion, if present earlier, usually is absent by this time due to necrosis of nervous tissues. Radiographic evidence of periapical pathosis supports the diagnosis of pulp necrosis. A periapical osteolytic area may be noted as early as 2-3 weeks post-trauma. Generally, discolored teeth which have pulp necrosis will have evidence of periapical pathosis within 1-2 months of the injury. Client education is important when examining the polytrauma patient with concussive injury to the crown. The incidence of pulp necrosis following this type of trauma is high and the owner should have the tooth monitored several times during the first 4-6 weeks post-trauma. Root canal therapy or extraction are treatment options for pulpitis and pulp necrosis without crown fracture. Uncomplicated Fracture Uncomplicated crown fractures should receive radiographs to confirm the absence of concomitant root fracture. This injury may be treated by simply smoothing the fractured crown surface with a diamond finishing bur. Application of a fluoride gel may be applied to decrease pain which may be associated with acute dentin exposure. Recommended Reading
ADVANCED ORAL FRACTURE REPAIR
Anatomy The mandible is composed of two halves with the horizontal portion (body) supporting teeth and the vertical portion (ramus) providing surfaces for muscle attachment and articulation with the skull. Each half of the mandible joins at rostral midline to form the mandibular symphysis. Major neurovascular structures including the mandibular artery and vein, and the inferior alveolar nerve enter the mandible on the caudomedial aspect through the mandibular foramen. These structures provide the major neurovascular input to the mandible and sole neurovascular supply to mandibular teeth. The mandibular canal opens mesially to form 2-3 mental foramina. The mandibular contribution to the temporomandibular joint (TMJ) consists of a transversely elongated condyle. The temporal bone contribution to the joint is tubular and closely surrounds the condyle. The TMJ also has a disc or meniscus providing an interface between bony components. Biomechanics Mandibular fracture biomechanics indicates that the tension side of the mandible is the alveolar border, or tooth side of the mandible. Techniques which engage teeth secure the tension surface allowing natural compression of the ventral surface. Intraoral splints, interdental acrylic, interdental wire, and combinations of interdental wire and acrylic can be applied to the tension band surface. Oblique mandibular body fractures can be classified as advantageous or disadvantageous. Fracture lines which are oriented from dorsocaudal to ventromesial are considered advantageous since muscular attachments to the mandible have a primarily ventral insertion causing compression of the fracture line. Fracture lines which are oriented from dorsomesial to ventrocaudal are considered disadvantageous since similar muscle forces lead to distraction of the mesial fragment. Knowledge of the inherent biomechanical nature of the fracture may effect decision making concerning the technique for fracture fixation. Fixation Techniques Mandibular fractures in the dog occur secondary to vehicular trauma, falls, kicks, gunshots, and fights with other animals. Mandibular fractures represent 3-6% of all fractures seen in the dog while 15% of all fractures in the cat affect primarily the mandibular symphysis. The most common location for fracture in dogs is between the PM 1 and M 2. Pathologic mandibular fracture may occur secondary to periodontal disease, neoplasia, and metabolic diseases. The primary objective for repair of mandibular fractures in small animals is return to normal function. Caudal malalignment of 2-3 mm may prevent closure of the mesial portion of the mouth by a full centimeter. Therefore it is necessary to maintain occlusive alignment while providing adequate stability for bony union. Basic principles of mandibular fracture repair include anatomic reduction and restoration of occlusion, application of a stable fixation to neutralize negative forces on the fracture line, gentle handling of soft tissues, avoidance of iatrogenic dental trauma, extraction of diseased teeth within the fracture line, minimizing excessive soft tissue elevation, and application of techniques which restore a rapid return to function. Fractures of the mandible in dogs present several unique challenges to the veterinarian since it withstands different forces compared with weight-bearing bones. Mandibular fractures will heal in the presence of fracture gaps and some mobility, as long as vascularity is protected, revascularization encouraged, and infection prevented. The fixation method should allow immediate restoration of function; be light and not cumbersome, economical, and readily available; and require only a reasonable amount of time, expertise, and ancillary equipment for application. Trauma to tooth roots and neurovascular structures may not result in clinical signs; however, endodontic and periodontal complications including alveolar bone resorption, tooth root involvement, pulpitis, and tooth loss may occur. The inferior alveolar artery and its branches provide the sole blood supply to alveolar bone, periodontal ligament, and teeth. Its importance in the healing of mandibular fractures and tooth structures after injury and any subsequent clinical effects is unknown. Likewise, the clinical occurrences of painful neuroma after damage to the inferior alveolar nerve during fracture has not been documented in the dog. Temporary muzzle coaptation may be applied during the preoperative period to support mandibular fracture. If used, the patient should be monitored to insure the muzzle does not interfere with breathing status or cause unnecessary, potentially detrimental excitement. Muzzle coaptation is also the most common definitive stabilization technique for mandibular fracture in dogs. Its common use indicates that it is successful in providing bony union most of the time. Post-treatment occlusion may not be optimal, however patients tend to do well clinically. Complications and problems associated with muzzle application include malocclusion, aspiration of food contents secondary to vomiting, hyperthermia from decreased ventilatory function (negative effect on panting), and moist dermatitis. This fixation method is inexpensive and does not negatively affect fracture fragment vascular supply or tooth roots and neurovascular structures of the mandibular canal. Although often successful in providing fracture fragment stability sufficient to promote secondary bony healing, mandibular healing as a result of muzzle application may be associated with permanent malocclusion. Other potential complications which may occur during the treatment period include patient noncompliance, and delayed return to function related to restriction of normal mastication. External fixation methods using intrafragmentary pins and acrylic side bars may provide adequate mandibular fracture stabilization; however, iatrogenic trauma of structures of the mandibular canal is possible based on recommendations for location of pin placement and mandibular anatomy. Loosening and infection are the two most frequent problems associated with the use of larger external skeletal fixation pins and are primarily a result of thermal necrosis of bone and soft tissue. Other potential complications associated with the use of external fixation methods are pin-tract infections, patient intolerance of the appliance, and disruption of the fixator bar on household furnishings. Internal fixation methods such as intramedullary pinning and plates and screws may also be associated with iatrogenic trauma of tooth roots and neurovascular structures. Disruption of fracture fragment vascular supply during implant application may complicate healing. Drawbacks to plating are the expense of the equipment, substantial time investment required to learn technical principles, and the penetration through or interference with the blood supply to the roots of the mandibular teeth resulting in endodontic disease. Methods using interdental fixation (IF) are an important component of temporary or primary mandibular fracture stabilization in humans. Clinical reports have recommended IF for stabilization of mandibular fractures in dogs. Advantages of interdental fixation for stabilization of mandibular fractures include avoidance of iatrogenic trauma to tooth roots and neurovascular structures of the mandibular canal, minimal disruption of fracture fragment vascular supply, restoration of occlusion, and early return to function. In summary, several fixation methods may be used for mandibular fracture repair which are quick to perform and provide sufficient stabilization for healing. Techniques which have these attributes may be used for emergency management of mandibular fractures. Interdental Fixation Interdental fixation methods for human mandibular fracture stabilization include Ivy loop, Stout loop, modified Stout loop, acrylic splints, and Erich arch bar. The ability of IF methods to provide mandibular fracture stabilization while avoiding iatrogenic complications inherent with other more conventional fixation methods makes these techniques particularly desirable. The low cost of materials, relative ease of application, and frequency of mandibular fracture in dogs contribute to their potential uses in veterinary medicine. Although acrylic does not adhere well to metal, it conforms to crown shape and interdigitates with gross metal architecture (metal cleats of the arch bar) and deformation (wire twists). Enamel adherence properties are propagated by formation of microporosities within prism cores or around rod peripheries of enamel using phosphoric acid gel etching of the enamel surface. Microporosity depth has been reported to range from 20 to 50 microns. Dental acrylic materials have been shown to penetrate these microporosities forming finger-like projections, resulting in a strong bond between the acrylic material and enamel. A technique utilizing 24 gauge stainless steel orthopedic wire and poly(methyl)methacrylate has been developed. The wire is place around the teeth in Stout loop fashion, the teeth are prepared by acid etching, and dental acrylic is bonded to the teeth to create the interdental fixation.
Recent studies compared the strength of various types of interdental fixation including wire, wire and arch bar, acrylic, acrylic and wire, and acrylic with wire and arch bar. Results indicated that acrylic interdental fixation reinforced with metal is the strongest fixation when tested in bending. The strongest interdental device of those tested was acrylic with wire and arch bar. Similar to the technique described, wire and arch bar may be applied using 24 g wire and orthodontic arch bar. The arch bar is applied to the lingual aspect of the mandibular arcade by using individual loops of 24 g wire around the neck of each tooth and under the cleat of the arch bar adjacent to the tooth. The wire is twisted on the lingual aspect of the mandibular arcade, in effect cerclage wiring the arch bar to individual teeth. Acrylic is applied in the same manner as described previously. In summary, the order of lesser to greater strength was wire < wire and arch bar < acrylic < acrylic and wire < acrylic with wire and arch bar. PARTIAL MANDIBULECTOMY AND PARTIAL MAXILLECTOMY
Rostral Mandibulectomy
Indications Unilateral or bilateral mandibulectomy for neoplasms of the rostral mandible, non-union, or chronic osteomyelitis Description of the Procedure
CLOSURE
The wound is closed in one layer since the oral mucosa is thin. The oral and labial mucosa are apposed in a simple continuous or interrupted pattern using synthetic or natural absorbable suture. Provision for ventral drainage is usually not necessary. COMMENTS
LATERAL PREMAXILLECTOMY
Indications Resective surgery for neoplasia or for reconstruction of oronasal fistula. Description of the Procedure
CLOSURE
The buccal mucosa is undermined to allow tension-free apposition to palatal mucosa. A two-layer closure is performed using synthetic absorbable suture in simple interrupted patterns for the submucosa and mucosa. COMMENTS
ROSTRAL MAXILLECTOMY
Indications Resective surgery for neoplasia Description of the Procedure
CLOSURE
The premaxillary defect may be reconstructed using buccal mucosal flaps to provide nasal and oral mucosal surfaces. The two-layer closure is performed using synthetic absorbable suture in simple interrupted patterns. Alternatively, the buccal mucosa may be apposed to hard palate mucoperiosteum in a primary two-layer closure using synthetic absorbable suture in simple interrupted patterns for the submucosa and mucosa. COMMENTS
REFERENCES
HARD PALATE ELEVATION TO AUGMENT ORONASAL FISTULA REPAIR
Indications Mucoperiosteum elevation for oronasal fistula repair, and to aid maxillectomy closure Description of the Procedure
CLOSURE
The small perifistula flaps and hard palate mucoperiosteal flap are sutured in place using synthetic absorbable suture in simple interrupted patterns. The soft tissue defect over the hard palate heals by epithelialization. COMMENTS
A buccal mucosal flap may be elevated and positioned to provide a nasal mucosal surface as the first layer for repair of acute oronasal fistula. The hard palate mucoperiosteal flap is used as described to provide the second, oral mucosal surface. ORAL AND MAXILLOFACIAL APPROACH TO THE LATERAL MAXILLA - FELINE
Based on a Procedure of Salisbury SK et al 3 Indications Resective surgery for neoplasia or limited premaxillectomy for oronasal fistula Description of the Procedure
CLOSURE
The buccal mucosa is undermined to allow tension-free apposition to palatal mucosa. A two-layer closure is performed using synthetic absorbable suture in simple interrupted patterns for the submucosa and mucosa. COMMENTS
Maxillectomy may be performed with an oscillating bone saw or osteotome and mallet after scoring the osteotomy lines with small perforating holes. Nasal turbinectomy should be performed if the neoplasm invades the nasal cavity. Maxillectomy is limited by the surgeons ability to reconstruct the oronasal defect. Patients with lesions which cross midline are usually not considered candidates for maxillectomy. Tension-free closure is imperative to avoid wound dehiscence and subsequent oronasal fistula. If wound dehiscence occurs second intention healing is usually successful. Failure of second intention healing requires utilization of oronasal fistula repair techniques. Food should be liquid in consistency during the first postoperative week. Cosmesis is generally good following surgery. Surgical results including facial concavity and an elevated lip do not effect function and are usually accepted by the owner. ORAL AND MAXILLOFACIAL APPROACH TO THE LATERAL MAXILLA - CANINE
Based on a Procedure of Salisbury SK et al 3 Indications Resective surgery for neoplasia Description of the Procedure
CLOSURE
The buccal mucosa is undermined to allow tension-free apposition to palatal mucosa. A two-layer closure is performed using synthetic absorbable suture in simple interrupted patterns for the submucosa and mucosa. COMMENTS
Maxillectomy may be performed with an oscillating bone saw or osteotome and mallet after scoring the osteotomy lines with small perforating holes. Nasal turbinectomy should be performed if the neoplasm invades the nasal cavity. Maxillectomy is limited by the surgeons ability to reconstruct the oronasal defect. Patients with lesions which cross midline are usually not considered candidates for partial maxillectomy. Tension-free closure is imperative to avoid wound dehiscence and subsequent oronasal fistula. If wound dehiscence occurs second intention healing is usually successful. Failure of second intention healing requires utilization of oronasal fistula repair techniques. Full-thickness incision of the lip commisure may be performed to gain exposure of the caudal operative field and would require closure of oral mucosa, muscle, and skin in individual layers. Food should be liquid in consistency during the first postoperative week. Cosmesis is generally good following surgery. Surgical results including facial concavity and an elevated lip do not effect function and are accepted by the owner.
HARD PALATE ELEVATION TO AUGMENT ORONASAL FISTULA REPAIR
Indications Mucoperiosteum elevation for oronasal fistula repair, and to aid maxillectomy closure Description of the Procedure
CLOSURE
The small perifistula flaps and hard palate mucoperiosteal flap are sutured in place using synthetic absorbable suture in simple interrupted patterns. The soft tissue defect over the hard palate heals by epithelialization. COMMENTS
A buccal mucosal flap may be elevated and positioned to provide a nasal mucosal surface as the first layer for repair of acute oronasal fistula. The hard palate mucoperiosteal flap is used as described to provide the second, oral mucosal surface. AXIAL PATTERN FLAPS FOR MAXILLOFACIAL RECONSTRUCTION
Head and neck squamous cell carcinoma (SCC) is the fourth most common neoplasm in felines. The oral cavity, aural pinna, and nares are commonly affected locations. Feline SCC is biologically similar to human head and neck SCC: both are locally invasive, and metastases to regional lymph nodes and lungs occur late in the course of disease. As in human medicine, treatment of disease limited to small primary SCC (stage I or II) is surgery or radiotherapy. Unfortunately, felines with SCC are often presented by their owner for advanced, large primary tumors (stage III or IV), which are not amenable to local resective surgery or radiotherapy as single modalities for treatment. In veterinary medicine, the type of surgical treatment is based on neoplasm location, surgeon's skill, and owner preference. Owners of affected felines may not desire or comply with adjunctive therapy recommendations often making surgical cure the operative goal for stage III and IV SCC. Fulfillment of this goal requires aggressive en bloc resection to optimize tumor-free margins. The concept of complete local excision of all visible tumor followed by, or concurrent with, chemotherapy or radiation therapy for treatment of presumed micrometastasis has achieved marked acceptance in human oncologic therapy and is being applied in veterinary medicine. This multimodality treatment plan includes surgery as an integral component especially for large, aggressive neoplasms. The goal of the operative plan for neoplasms of the head and neck in cats and dogs is most commonly curative resection or palliation. A surgical procedure which offers the greatest possibility of cure, restores or maintains function, and has an acceptable cosmetic result is often required in veterinary medicine. Regional axial pattern flaps may serve as a compromise between local and free flaps by providing durable tumor-free tissue for wound reconstruction. The availability of cervical and frontal cutaneous flaps with direct cutaneous blood supply for head and neck reconstruction may allow radical resective surgery avoiding functional disturbances while providing a cosmetic result. Caudal Auricular (Lateral Neck) Flap The lateral neck flap has been shown to be a useful reconstructive surgical technique following resection of head and neck neoplasms in humans. The skin-muscle composite has versatility for multiple head and neck lesions allowing generous margins, less tissue bulk compared with other regional flaps, adaptable length, and vascular reliability. The feline and canine platysma muscle is intimately associated with subcutaneous tissues. Cutaneous vascular supply from multiple vessels, including cutaneous branches of the caudal auricular artery and vein are observed coursing in the lateral cervical region of the platysma muscle. As in humans, the observed vascular supply to the feline and canine lateral neck flap is consistent in location and emphasizes a cranial basis and horizontal orientation. The flap is versatile based on surgical studies in which intraoperative manipulation was performed prior to orthotopic replacement, and clinical application in two feline patients. There seems to be no deleterious results related to flap thinness or gravitational effects based on application in clinical patients. Results of cadaver and vascular studies in the feline and canine show one cutaneous branch of the caudal auricular artery and vein contributing blood supply to the cranial aspect of the cervical skin and platysma muscle while angiography reveals dorsal and caudal vessel orientation which parallels the central cervical region. The cutaneous branch of the caudal auricular artery observed during surgery is intimately associated with the platysma muscle and divides near its origin located in the area between the lateral aspect of the wing of the atlas and the vertical ear canal. Guidelines for flap location have been based on results of cadaver and vascular studies. The flap is centered over the lateral aspect of the wing of the atlas. The flap is positioned in the center of the neck within ventral and dorsal lines paralleling the measured flap base and the same width measurement centered on the spine of the scapula. Flap length may vary and does not necessarily extend to the spine of the scapula. The platysma muscle is intimately associated with the subcutis of the flap. In surgical studies, the mean survival length in cats (7.7 + 2.2 cm) and dogs (15.4 + 2.1 cm) of flaps incorporating vascular supply from the caudal auricular artery and vein indicates that the lateral neck flap may be most useful for caudal head and neck defects compared with more rostral defects which occur following resection of neoplasms affecting the nares, premaxilla, or mandibular symphysis. The reconstructive surgical technique described here may allow elective neck dissection with preservation of the caudal auricular artery depending on the size of the operative field. This approach provides access for excisional biopsy of mandibular and/or cervical lymph nodes to aid staging and augment surgical extirpation of metastatic disease. Metastatic routes which may be considered during dissection include perineural, vascular and microvascular, lymphatic, and transcapsular. Extended dissection from the primary site may improve the incidence of free margins related to surgical resection of direct metastatic pathways. This may be of particular importance for neoplasms of the floor of the mouth and caudal head and neck region. The cranial cervical area was easily observed in conjunction with lateral neck flap elevation in surgical studies and clinical patients. Direct observation of regional lymph nodes allows assessment of gross transcapsular spread of the tumor which may warrant wider margins for adhered lymph nodes. Superficial Temporal (Forehead) Flap Skin of the canine and feline maxillofacial region is relatively immobile, making cutaneous wounds often not amenable to primary repair or second-intention wound management without resultant functional and cosmetic deficiencies. Human patients with maxillofacial defects have been successfully surgically managed using "forehead flaps" since as early as 700 BC. The scalping "forehead flap", with the flap base at the level of the zygomatic arch, is similar to the flap described here. Guidelines for flap location were based on results of cadaver and vascular studies performed in dogs and cats. The landmarks for the base of the forehead flap were the caudal aspect of the zygomatic arch caudally and the lateral orbital rim rostrally. Flap dimensions were based on the feasibility of primary wound closure of the donor site and required length to transfer the flap to the maxillofacial area, including the nasal planum as the rostral extent. The width of the flap was equivalent to the width of the zygomatic arch. Based on the necrosis of the distal tip of the extended 4:1 length:width ratio flaps, we recommend use of a 3:1 length:width ratio forehead flap which provides adequate tissue for rostral rotation to the nasal planum. On the basis of the results of our research, the forehead flap based on the superficial temporal artery had a greater surviving length compared with flaps dependent solely on the subdermal plexus. The forehead flap may have application for maxillofacial reconstruction of traumatic wounds, or wounds resulting after excisional surgery or radiation therapy. Clinical case - Surgery was done on a l-year-old border terrier for reconstruction of a traumatic maxillofacial defect. A premaxillectomy was performed, removing the incisors but maintaining the palatal incisive papilla, to provide a mucosal surface for reconstruction of the nares. A 4.0 x 12.0 cm (3:1 length:width ratio) forehead flap based on the left superficial temporal artery and vein was created. A bridge incision was made beginning in the frontal region and bisecting the nasal region. The flap was rotated rostrally, and the distal tip was sutured to the palatal mucosa in the region of the nares. Primary closure of the donor site and the periphery of the flap was performed using a simple continuous suture pattern. |
