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Dentistry Mark M. Smith, VMD, DACVS, DAVDC Red Bank Veterinary Hospital Periodontal Disease and Therapy PERIODONTAL ANATOMY The tissues which surround the teeth, and provide the support necessary for normal function form the periodontium (Greek peri- "around"; odont-, "tooth"). The periodontium is comprised of the gingiva, periodontal ligament, alveolar bone, and cementum. The gingiva is anatomically divided into the marginal (unattached), attached, and interdental gingiva. The marginal gingiva forms the coronal border of the gingiva which surrounds the tooth, but is not adherent to it (Fig. 1). The cementoenamel junction (CEJ) is where the crown enamel and the root cementum meet. The marginal gingiva in normal periodontal tissues extends approximately 2-mm coronal to the CEJ. Microscopically, the gingiva is comprised of a central core of dense connective tissue and an outer surface of stratified squamous epithelium. The space between the marginal gingiva and the external tooth surface is termed the gingival sulcus. The normal depth of the gingival sulcus, and corresponding width of the marginal gingiva, is variable. In general, sulcular depths less than 2 to 3-mm in humans and animals are considered normal.1 Soft tissue attachment at the gingival sulcus is the first line of defense against periodontal disease. The sulcar epithelium is thin and semi permeable, which may be important in the pathogenesis of periodontal disease as injurious bacterial products may pass into the gingiva, and tissue fluids and humoral defense components may pass into the sulcus. The junctional epithelium forms the collar of epithelial attachment around the tooth at the base of the sulcus. Gingival connective tissue is composed of collagenous bundles of fibers with specific orientations and attachments. Their function is to provide for rigidity, structure, and attachment of the gingiva.2 The primary cellular element of the gingival connective tissue is the fibroblast. They provide for renewal and degradation of collagen and other constituents and are the primary regulators of gingival wound healing. The periodontal ligament (PDL) surrounds the normal tooth root and forms the connective tissue attachment from the root to the alveolar bone proper. In addition to maintaining the tooth's attachment to the alveolar bone, and the structure of the gingiva in relation to the tooth, the PDL acts as a shock absorber and a means of transmitting occlusal forces to bone.2 The cells of the PDL are active in ongoing remodeling of cementum and the PDL. They are active in the resorption and formation of collagen and cementum and the fibroblasts of the PDL may develop into cementoblasts and osteoblasts. Finally, the PDL provides lymphatic drainage and blood vessels necessary for the nutrition of the cementum, bone , and gingiva.2 The principal fibers of the PDL are densely collagenous and arranged in bundles, which insert into cementum and bone. Cementum is the hard tissue which covers the tooth roots. As cementum is formed, the fibers of the PDL are incorporated into it as Sharpey's fibers. Unlike bone, cementum does not remodel. The alveolar process consists of the bone forming the alveoli. The components of the alveolar bone do not differ from bone elsewhere in the body. The alveolar bone proper consists of a thin layer of dense compact bone into which the Sharpey's fibers of the PDL insert deeply. Radiographically this bone appears as a thin radiopaque line surrounding the root called the lamina dura. The supporting alveolar bone is comprised of the facial and lingual plates of compact bone and cancellous trabeculae. PERIODONTITIS - PATHOPHYSIOLOGY Periodontitis refers to inflammation and destruction of the elements of the periodontium. Diseases of periodontal tissues are most commonly the result of an accumulation of bacterial plaque and calculus, and the proliferation of pathogenic organisms subgingivally within the sulcus. This discussion will be primarily focused on chronic destructive periodontal disease. This term is defined by periodontal disease caused by local factors, such as bacterial plaque accumulation, in otherwise healthy individuals.3 Gingivitis, or Stage 1 periodontal disease, is the inflammatory condition of the gingiva in which the junctional epithelium remains attached to the tooth root at its normal CEJ anatomic level (Fig. 2). There are pathologic changes present, but no loss of periodontal attachment. Periodontitis occurs when pathologic changes progress to include destruction of the gingival sulcus and PDL with migration of the junctional epithelium apical to the CEJ.4 Periodontitis is always preceded by gingivitis, but gingivitis does not always progress to periodontitis. Periodontal pocket formation (Stage 2-4 periodontal disease) occurs as a result of loss of periodontal attachment and pathologic deepening of the gingival sulcus (Fig. 2).5 The pockets are lined by plaque covered cementum and enamel on one side, while the soft tissue walls and floor of the pocket are covered by a micro ulcerated layer of junctional epithelium, which is attached to the root at the base of the pocket.6 The process begins with inflammation of the connective tissues within the wall of the gingival sulcus.5 As the normal sulcus progresses to a diseased periodontal pocket, the proportion of pathogenic microorganisms increases.7 The microorganisms, including both aerobic and anaerobic bacteria, produce toxic products and cause inflammation, which results in tissue destruction and deepening of the sulcus.5 With inflammation, the junctional The battleground for periodontal disease is in the gingival sulcus…a location the clinician cannot visualize. epithelium lining the floor of the pocket is infiltrated with polymorphonuclear cells. Cellular enzymes degrade cellular junctions and the epithelium detaches from the tooth, causing further recession of the pocket.5 Bony destruction is caused by microorganisms and their products, as well as the destructive effects of the immunodefense, such as prostaglandins and complement of the host, and substances from inflamed gingiva. Histologic evidence indicates that bone loss in chronic destructive periodontal disease occurs perivascularly. That is, the pattern of resorption roughly parallels the vascular tree of alveolar bone.6 Osteoclastic resorption of alveolar bone results in the loss of attachment of the fibers of the (PDL). Chronic inflammation will result in alveolar bone loss at a rate of 0.2 to 0.3 mm per year.8 PERIODONTAL THERAPY The cornerstones of periodontal therapy include a thorough oral and periodontal examination followed by meticulous supra- and subgingival cleaning of the teeth.9,10 A calibrated periodontal probe should be used to probe multiple locations around the tooth within the gingival sulcus. It is important to critically evaluate the gingival sulcus since disruption of its integrity signifies periodontal disease Bleeding upon gentle probing indicates inflammation, but not necessarily irreversible periodontal disease. Normally, the distance from the gingival margin to the base of the sulcus is 2 to 3-mm in the dog and < 1-mm in the cat. Attachment loss and pathologic deepening of the sulcus forming a periodontal pocket should be noted and measured to not only determine severity, but the success of future treatment. Although the depth of attachment loss is measured in mm, it is most useful to consider the degree of attachment loss as a % length from the cementoenamel junction to the apex of the tooth. Early periodontal disease (Stage 2) and < 25 % attachment loss is associated with probable depths of 3 to 5-mm in the dog. The prognosis for improvement following nonsurgical periodontal therapy is good/guarded. Moderate (Stage 3) periodontal disease has attachment loss measuring 5 to 7-mm reflecting 25 to 50 % attachment loss and a guarded prognosis. Severe (Stage 4) periodontal disease has > 50 % attachment loss with pocket depths measuring > 7-mm warranting a guarded/poor prognosis.11 Teeth having attachment loss > 70 % of the tooth length require extraction (Fig. 2). Supra- and subgingival teeth cleaning begins with removal of gross debris and calculus using old bone rongeurs or extraction forceps. Power scalers are then utilized to clean broad surfaces of the crown. Ultrasonic scalers are the preferred power cleaning instrument since they are more efficient and vibrate more rapidly (25,000 - 42,000 cycles per second) compared with sonic (20,000 cycles per second) scalers. The heat generated by the increase in cycles per second using ultrasonic scalers can potentially cause damage to the tooth. Therefore, recommendations for ultrasonic scaling include light application of the tip in an oblique orientation with a maximum contact time of 15-seconds for each tooth. The water spray provided with ultrasonic scalers combined with returning to the same tooth after a 30-second period of cooling will minimize thermal injury to the tooth. The ultrasonic scaler and hand held curettes are used to clean the subgingival area within the gingival sulcus. Again, the ultrasonic scaler removes gross debris in this location. The fine-tuning and requisite subgingival cleaning requires use of dental curettes to insure cleaning of the "hidden" crown and tooth structure exposed secondary to periodontal disease. The end of the working surface of the curette is rounded and must be sharp. The round end will prevent trauma to the soft tissues, which would be unavoidable with a pointed dental scaler. The dental curette must be sharp in order to properly remove, not smooth, calculus. Periodontal pockets should also receive superficial debridement of the junctional epithelium that has migrated the length of the pocket. This debridement, performed with a dental curette, may promote some soft tissue reattachment and pocket reduction. The amount of reattachment, if any, is dependent upon thorough cleaning of the root surface and the "race" between tissue reattachment and the migration of junctional epithelium to resurface the pocket. Periodontal pockets up to 5-mm deep may be treated effectively in this manner without surgical exposure. After hand scaling, the gingival sulcus should be lavaged with dilute chlorhexidine using an air-water syringe. Dental hand scalers are used to clean coronal pits and fissures. The professional teeth cleaning procedure is completed by polishing the enamel surfaces using fine-grit pumice in a rubber polishing cup attached to a slow-speed handpiece. Polishing removes microscopic irregularities and scratches that resulted from the cleaning procedure. A smooth enamel surface will delay bacterial plaque adherence to the tooth, allowing more effective initial home care treatments. ADJUNCTIVE THERAPY Bacteremia occurs during professional teeth cleaning procedures.12 Generally, antimicrobial therapy is not administered in otherwise healthy patients since the bacteremia is transient and would not be expected to cause systemic disease or complications. However, preoperative intravenous antimicrobial therapy using a broad-spectrum bactericidal agent, such as sodium ampicillin, is recommended in high risk patients. This prophylactic administration of an antimicrobial is warranted for patients with advanced periodontitis, immunosuppression secondary to metabolic disease, primary immunopathies, artificial implants, or cardiac disease. 9 Patients at risk with severe periodontitis and patients with refractory periodontal disease may benefit from the administration of systemic antimicrobials immediately following a professional teeth cleaning procedure.9,10 Human studies have shown that both amoxicillin-clavulanic acid (Clavamox, Pfizer Animal Health, Exton, PA) and clindamycin (Antirobe, Pharmacia & Upjohn, Kalamazoo, MI) are associated with improved periodontal attachment when administered for 7 to 14-days immediately following a professional teeth cleaning procedure, compared with attachment gains following the cleaning procedure only.13,14 These two systemically delivered antimicrobials are approved by the US Food and Drug Administration (FDA) for veterinary dental use. They have also been shown to be particularly effective against the anaerobic microbial flora associated with periodontal disease in dogs and cats.15-17 A potential side-effect of the systemic administration of antimicrobials is the development of resistant bacterial strains in the mouth, gastrointestinal tract, and other body locations. Local, direct administration of antimicrobial agents avoids the complications associated with their systemic administration. Local application provides higher concentrations of the antimicrobial at the area of disease, where it is most needed, compared with systemic administration.18 Other parameters for successful local administration of antimicrobials include its efficacy for an extended duration and biocompatibility without the risk of inactivation secondary to local factors or influences. Local delivery of an effective periodontal antimicrobial agent has been developed in veterinary medicine. Doxycycline (Doxirobe, Pharmacia & Upjohn, Kalamazoo, MI) has been approved for veterinary use by the FDA as a gel for the local treatment of periodontal disease. The local administration of doxycycline not only avoids the complications of systemic antimicrobial therapy, but it also inhibits the collagenase enzyme. Production of this enzyme during the immunodefense "battle" within the periodontal tissues contributes to attachment loss by destroying the connective tissue basis for the attached gingiva and the PDL. Doxycycline gel is recommended for periodontal pockets that measure > 3 to 4-mm.9,10 It is imperative to thoroughly treat the pocket using ultrasonic and hand scaling, and soft tissue curettage before placing the gel. Blunt-ended cannulas are provided by the manufacturer for placement of the doxycycline gel at the deepest aspect of the pocket (Fig. 3). The gel hardens after applying a few drops of water. A blunt hand instrument is used to pack the gel into the pocket so that it is below the gingival margin. The hardened gel remains in place for 3 to 6-weeks, releasing doxycycline into the adjacent periodontal tissues. Clients are advised to resume home care after 10 to 14-days to avoid disruption of the material. Doxycycline gel does not stimulate bone formation, but does provide an environment conducive to soft tissue attachment. Complete periodontal regeneration including bone is preferred. However, it is difficult to attain in dogs and cats because oral hygiene, to the degree necessary for success of an advanced regenerative procedure, may be difficult or impossible to deliver by the owner. Doxycycline gel may also be used as a preparative treatment before initiating more advanced periodontal regenerative techniques. Regardless of the stage of periodontal disease, home care performed by the owner is a critical component of oral health maintenance for their pet. Pastes, gels, rinses, chew toys, chew aids, and diets are among the home care products available. Whenever a new (or old) product is recommended for clinical home care application, consider whether it has the Veterinary Oral Health Council (VOHC) seal of approval and if the accompanying research shows that the product has high compliance, safety, and efficacy (reduced plaque, calculus, and gingivitis scores). SUMMARY AND RECOMMENDATIONS Periodontal disease is usually a life-long disease for dogs and cats, requiring the veterinary clinician's attention and expertise. As with any other common disease in clinical practice, it is important to be comfortable with treatment plans that you can recommend to insure the best possible oral health care . The recommended plan should be based on a thorough oral and periodontal examination to determine the stage of periodontal disease (Table 1). Treatment plans should also be flexible to allow the clinician to modify treatment based on the patient's response. Knowledge of periodontal anatomy and pathophysiology combined with rational therapeutic modalities provides confidence for the clinician to communicate effective treatment plans with pet owners. AUTHOR INFORMATION Dr. Smith is a Diplomate of the American Veterinary Dental College, and the American College of Veterinary Surgeons. He is Editor of the Journal of Veterinary Dentistry and Professor of Surgery and Dentistry, VA-MD Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, 24061. Table 1. Periodontal staging and associated treatment options.
* Preoperative intravenous antimicrobial therapy using a broad-spectrum bactericidal agent, such as sodium ampicillin, is recommended in high risk patients with advanced periodontitis, immunosuppression secondary to metabolic disease, primary immunopathies, artificial implants, or cardiac disease. REFERENCES
Figure Legends Figure 1: Diagram showing the periodontal structures supporting the tooth. With permission, from Mark A. Tholen, Concepts in veterinary dentistry, 1983, p. 16. Figure 2: Oral photographs and illustrations showing the stages of periodontal disease. Figure 3: Illustration showing placement of doxycycline gel in a periodontal pocket. 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
Exodontic Therapy 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). Complications Associated with Tooth Extraction INTRODUCTION Tooth extraction is a routine and commonly performed procedure in small animal practice. However, complications may occur and include root fragmentation, iatrogenic mandibular fracture, ocular trauma, and infection. FRAGMENTED ROOTS Diagnosis: Fragmented roots may occur secondary to crown or maxillofacial trauma. However, the most common etiology of root fragmentation is iatrogenic during tooth extraction. The diagnosis is made following evaluation of skull or dental radiographs for patients having received trauma. Radiographs may also aid diagnosis of root fragmentation during tooth extraction, 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. 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 the presence of the root. Prevention: Patience during the extraction procedure is the best method to prevent this complication. Extraction forceps should not be used until the tooth is so mobile that it could be removed using finger pressure. Excessive force with the periodontal elevator or premature use of the extraction forceps causes root fragmentation. Treatment: Removal of fragmented roots requires continuation of extraction 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. Although not recommended, 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. Complications associated with this technique include incomplete removal of the root fragment, relocation of the root fragment into the mandibular canal or nasal cavity, and hemorrhage from trauma to the infraorbital or mandibular alveolar arteries. A radiograph should be taken of the extraction site to confirm removal of root fragments. 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 that 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, or complications of tooth extraction, 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 tooth extraction. All too often "wait and watch" is advised to the owner with regards to treatment of retained, fragmented roots following trauma. 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" treatment plan should only be implemented at the request of the owner and not recommended by the veterinarian. IATROGENIC MANDIBULAR FRACTURE Diagnosis: 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. 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 related to the large root surface area that 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 spontaneously or during relatively routine exodontic maneuvers. Finally, older patients requiring extraction of the mandibular first molar may have age-related osteopenia that 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. Prevention: Pre-procedure intraoral or standard radiographs will show bone lysis secondary to periodontal disease. Information gained from radiographic assessment of teeth to be extracted aid the clinician in being able to warn the owner about potential complications during tooth extraction. Controlled force and an emphasis on buccal or lingual luxation of tooth roots are recommended to prevent iatrogenic fracture. 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.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: 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. 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. Alternatively, intraoral splints may be applied to the edentulous mandible to provide stability and eventual bony union. OCULAR TRAUMA Diagnosis: Iatrogenic trauma to ocular structures may occur during extraction of the maxillary fourth premolar, first molar, or second molar. The cause of such trauma is related to the thin alveolar bone and proximity of the ventral floor of the orbit. 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. Panophthalmitis may result from perforation of the globe by the periodontal elevator. If antimicrobial and anti-inflammatory treatment fails, enucleation is an unfortunate result. Prevention: 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. INFECTION Diagnosis: Infection of the extraction site following tooth extraction 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. Treatment: 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, that 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. The affected tooth and periodontium are the focus of the infection with the maxilla or mandible showing clinical signs of osteomyelitis. Tooth extraction of the tooth alone is not sufficient to treat this problem. Additional procedures that 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. 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. RECOMMENDED READING
Oronasal Fistula Repair Acquired palate defects secondary to tooth extraction are either acute or chronic. Acute oronasal fistula following tooth extraction is diagnosed by direct visualization of the nasal cavity or observing nasal hemorrhage at the nares. This usually occurs following canine tooth extraction or extraction of teeth with severe periodontal disease leading to direct communication with the nasal cavity. Acute oronasal fistula is treated by elevating a buccal mucosal flap using a #15 scalpel blade or a periosteal elevator. Flap mobility and working length is enhanced by incising the periosteum at the flap base. Care is taken not to incise mucosa. The flap is sutured to hard palate mucosa using 3-0 or 4-0 synthetic absorbable material. Single-layer, primary intention healing is usually sufficient to prevent recurrence and chronic oronasal fistula. A two-layer flap may be required to repair chronic oronasal fistula. There are three anatomic locations for flap development: 1) the mucosa of the periphery of the fistula; 2) buccal mucosa, and 3) hard palate mucoperiosteum. Therefore, two of these locations should be utilized. The clinician may decide which flaps to use in which position. However, the first flap must provide an epithelial surface for the nasal cavity. The submucosal surface of the first flap lies in the oral cavity. The second flap is designed to cover the submucosal surface of the first flap and also provide an epithelial surface for the oral cavity. Suture is placed in a simple interrupted pattern using 3-0 or 4-0 synthetic absorbable material. HARD PALATE ELEVATION TO AUGMENT ORONASAL FISTULA REPAIR Indications: Mucoperiosteum elevation for oronasal fistula repair Description of the Procedure: The patient is positioned in dorsal recumbency with the neck extended. The neck is positioned over an elevated, padded area (rolled towel) and stabilized by taping the maxilla to the operating table. The mandible is suspended to open the mouth maximally. The mucoperiosteum is incised along the palatal aspect of the rostral dental arcade. A sharp periosteal elevator is used to undermine and elevate the hard palate mucoperiosteum. The caudal limit of dissection is marked by the exit of the major palatine arteries from the major palatine foramen. Hard palate mucoperiosteum may be used as a component of chronic oronasal fistula repair. Lateral and medial flaps are developed from healed perifistula tissue. The width of each flap is 1/2 the diameter of the fistula. The flaps are inverted to provide a nasal mucosal surface. The hard palate mucoperiosteal flap is placed over the submucosal surface of the newly positioned nasal mucosa. 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 Reconstruction in Dogs and Cats 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. Mandibulectomy and Maxillectomy Techniques ROSTRAL MANDIBULECTOMY Indications: Unilateral or bilateral mandibulectomy for neoplasms of the rostral mandible, non-union, or chronic osteomyelitis Description of the Procedure: The patient is positioned in dorsal recumbency. The patient's neck is extended over an elevated padded area (rolled towel) and the maxilla is secured to the operating table using adhesive tape. Thumb forceps are used to retract skin of the ventral mandible to expose oral mucosa. The oral and labial mucosa should be incised a minimum of 1 cm from the periphery of the neoplasm. Sharp dissection is performed using scalpel or periosteal elevator to incise soft tissues including oral mucosa, and mentalis, obicularis oris, mylohyoideus, and geniohyoideus muscles from the rostral mandible. Dissection extends to the level of mandibulectomy. Mandibulectomy is usually performed rostral to the frenulum of the tongue at the level of the mandibular 3rd premolar. Ostectomy sites are contoured with bone rongeurs to facilitate closure and remove sharp bone edges which may traumatize mucosa. 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:
Indications: Resective surgery for neoplasia or for reconstruction of oronasal fistula. Description of the Procedure: The patient is positioned in lateral recumbency. The buccal mucosa is incised at least 1 cm from the lesion. A periosteal elevator is used to elevate mucosa from its attachment on the maxilla and incisive bones. The infraorbital artery, vein, and nerve exit the infraorbital canal of the maxilla and should be avoided unless wide resection requires their division and ligation. The palatal mucosa is incised similarly and the mucoperiosteum is elevated. The major palatine artery is divided and ligated if the resection approaches the major palatine foramen. Resection of the premaxilla and/or maxilla exposes the nasal cavity. 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: The patient is positioned in dorsal recumbency. The lateral and rostral buccal mucosa, and hard palate mucoperiosteum are incised at least 1 cm from the lesion. A periosteal elevator is used to elevate mucosa from its attachment on the hard palate, maxilla, and incisive bones.The cartilaginous nasal fossae and septum are incised and soft tissues are elevated caudally to the osteotomy site. Rostral maxillectomy is performed using an oscillating bone saw or osteotome and mallet after scoring the osteotomy lines with small perforating holes. Maxilloturbinates are transected along the plane of maxillectomy. Hemorrhage is controlled by electrocautery, direct pressure, and vessel ligation. 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:
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