Brenda L. Mulherin, DVM, DAVDC
Iowa State University College of Veterinary Medicine
One of the most common procedures performed by general practitioners in the oral cavity is surgical tooth extraction. The procedure is either a closed extraction, in which the tooth is extracted without a mucoperiosteal flap, or an open extraction, in which a mucoperiosteal flap is created to expose and remove alveolar bone and allow a tension-free closure.
To a client, tooth extractions may seem routine and commonplace. However, those who have experience with oral surgery are aware that even theoretically simple extractions can be difficult. This article presents some factors to consider to make surgical extractions as safe and easy as possible for both surgeon and patient.
EXTRACTION INDICATIONS AND COMPLICATIONS
The decision to extract a tooth stems from a variety of reasons, including1,2:
- Complicated crown fracture
- Endodontic disease
- Periodontal disease
- Tooth resorption
- Tooth nonvitality
The difficulty of an extraction can be affected by the health of the periodontium surrounding the tooth. If the periodontium is healthy, but the pulp is diseased, the tooth may be difficult to extract. Examples of teeth with healthy periodontium include those extracted to treat a malocclusion, which are healthy teeth in the wrong place. This is common in immature patients with persistent deciduous teeth, or when interceptive orthodontic procedures are performed. Other examples are recently fractured teeth with pulp exposure (Figure 1) for which endodontic therapy is not an option.1
Planning ahead can help avoid complications relating to surgical tooth extraction. This includes taking intraoral dental radiographs and having the ability to interpret the radiographic findings. Knowledge of dental radiographic interpretation can help avoid some major pitfalls when surgically extracting teeth. This knowledge includes understanding what constitutes normal and abnormal anatomy as well as a general knowledge of the surrounding hard and soft tissue structures.
Avoid complications associated with surgical tooth extractions by planning carefully and having a general knowledge of canine and feline dentition and tooth root numbers.
NORMAL DENTITION AND TOOTH ROOTS
Canine Dental Formulas
The deciduous (primary) dentition of the canine oral cavity comprises 28 teeth (Table 1). The dentition is multiplied by 2 to include both right and left arcades. There are 3 incisors (i), 1 canine (c) tooth, and 3 premolars (pm) in each of the maxillary and mandibular arcades: 2 × (i 3/3, c 1/1, pm 3/3) = 28 teeth.3
The permanent (secondary) dentition of the canine oral cavity comprises 42 teeth (Table 1 and Figure 2). There are 3 incisors (I), 1 canine (C) tooth, and 4 premolars (PM) in each of the maxillary and mandibular arcades. Each maxillary arcade has 2 molars (M), and each mandibular arcade has 3 molars: 2 × (I 3/3, C 1/1, PM 4/4, M 2/3) = 42 teeth.3
|Table 1 Canine and Feline Dental Formulas|
|DENTITION||TOTAL TEETH||TEETH IN EACH
|TEETH IN EACH
|Deciduous (primary)||28||i3, c1, pm3||i3, c1, pm3|
|Permanent (secondary)||42||I3, C1, PM4, M2||I3, C1, PM4, M3|
|Deciduous (primary)||26||i3, c1, pm3||i3, c1, pm2|
|Permanent (secondary)||30||I3, C1, PM3, M1||I3, C1, PM2, M1|
Feline Dental Formulas
The deciduous dentition of the feline oral cavity comprises 26 teeth (Table 1). There are 3 incisors, 1 canine, and 3 premolars in each maxillary arcade. Each mandibular arcade has 3 incisors, 1 canine, and 2 premolars: 2 × (i 3/3, c 1/1, pm 3/2) = 26.3,4
The permanent dentition of the feline oral cavity comprises 30 teeth (Table 1 and Figure 3). There are 3 incisors, 1 canine, 3 premolars, and 1 molar on the right and left maxillary arcades. Each mandibular arcade has 3 incisors, 1 canine, 2 premolars, and 1 molar: 2 × (I 3/3, C 1/1, PM 3/2, M 1/1) = 30.3,4
Tooth Root Structure
A standard number of roots are associated with each tooth (Table 2). The number of roots helps determine the type of extraction necessary; therefore, it is important to know the root structure of the tooth or teeth being treated. However, abnormal tooth and root structures do occur, making presurgical radiographs essential (see Tooth Root Abnormalities). For example, canine maxillary second and third premolars and mandibular second, third, and fourth premolars each have 2 roots within the normal structure; however, many of these teeth have an accessory root.5
Cats appear to have more variations in normal root structures than dogs. The feline mandibular third and fourth premolars and the mandibular first molar teeth all should have 2 roots.5 One study found that the feline maxillary second premolar is absent in 7.9% of cats, has a single root in 27.7% of cats, has partially fused roots in 55.1% of cats, and has 2 fully formed roots in 9.2% of cats.6 This study also found that the feline maxillary first molar is absent in 2.3% of cats, has a single root in 35% of cats, has partially fused roots in 34.7% of cats, and has 2 fully formed roots in 28% of cats.6
|Table 2 Standard Number of Tooth Roots of Canine and Feline Permanent Teeth|
|ARCADE||ARCADEINCISOR TEETH||CANINE TEETH||PREMOLAR TEETH||MOLAR TEETH|
|Maxillary||1 root each||1 root each||1st: 1 root
2nd: 2 roots
3rd: 2 roots
4th: 3 roots (2 mesial, 1 distal)
|1st: 3 roots (2 buccal, 1 palatal)
2nd: 3 roots (2 buccal, 1 palatal)
|Mandibular||1 root each||1 root each||1st: 1 root
2nd: 2 roots
3rd: 2 roots
4th: 2 roots
|1st: 2 roots
2nd: 2 roots
3rd: 1 root
|Maxillary||1 root each||1 root each||2nd: 1 or 2 roots
3rd: 2 roots
4th: 3 roots (2 mesial, 1 distal)
|1st: 1 or 2 roots|
|Mandibular||1 root each||1 root each||3rd: 2 roots
4th: 2 roots
|1st: 2 roots|
TOOTH ROOT ABNORMALITIES
Dental radiography is necessary to assess whether there are root abnormalities that can affect an extraction.
A supernumerary (extra) root can make a seemingly straightforward extraction more difficult, especially if not identified on dental radiography. The feline maxillary second premolar and first molar can have 1 to 3 roots.6 Dogs can also have supernumerary roots (Figure 4). One study reported that 15.2% of large mesaticephalic-breed dogs have at least 1 supernumerary root within the oral cavity.7
Some abnormalities can make an extraction easier. These usually involve teeth that normally have 2 roots, but have developed only a single root. These teeth may be affected by fusion, gemination, or concrescence. Identification of these teeth on dental radiographs allows the surgeon to eliminate sectioning during extraction.
Fusion is when 2 tooth buds have joined, resulting in a single-rooted tooth with 2 root canals.7,8 Gemination is the incomplete development of 2 teeth from 1 tooth bud, which usually results in a tooth with 2 crowns but only a single root.7,8 Concrescence is the joining of adjacent teeth by the cementum only.7,8
Often, these developmental abnormalities cannot be differentiated without the aid of histopathology (Figures 5 and 6). In many instances, these teeth can remain in the mouth if crowding, periodontal disease associated with the tooth, or radiographic evidence of disease is not present. Regardless of which developmental condition has occurred, if the tooth needs to be extracted, knowing how many roots need to be removed is the most important consideration.
Dilacerated roots are roots that bend at sharp angles, which can make extracting them in their entirety difficult (Figures 7 and 8). Dilacerated roots can curve toward the caudal or rostral aspect of the mouth. In one study, 34.4% of dogs had evidence of tooth root dilacerations.8
Again, presurgical dental radiographs are necessary to identify dilacerated roots and their direction. Without the knowledge of whether dilaceration is present, surgical extraction can fracture dilacerated roots. Of even greater concern is when the dilacerated root is positioned close to the ventral mandibular cortex. If the surgeon is not careful, extraction technique or fractured root tip retrieval can result in a mandibular jaw fracture.
PLANNING FOR TOOTH EXTRACTIONS
Schedule Adequate Time
Scheduling the appropriate amount of procedure time alleviates additional stress, allows ideal surgical technique, and permits the procedure to be performed without time constraints. The most important aspect of tooth extraction is patience. When applying pressure to the tooth root, using slow, gentle, consistent pressure to extract the root is better than forceful, jerky, sudden movements. Rushing through an extraction procedure often leads to an audible crack that signifies the fracture of the tooth root or, more seriously, of the surrounding bone.
Gently controlling the elevation of the gingiva and mucosa of the tooth to be extracted allows exposure of the underlying alveolar bone and encourages adequate postoperative healing of the extraction site. Traumatic and rapid elevation of the mucoperiosteal flap can tear tissue, delay healing, and, if severe enough, reduce flap size.10
Adequate bone removal over the tooth roots allows root exposure and visualization of the structures to be extracted and helps reduce the time needed for the extraction. Gentle, consistent pressure applied to the roots during elevation weakens the periodontal ligament. This allows for increased mobility of the root to eventually facilitate removal.
Use Proper Equipment
Proper equipment ensures smoother surgical extractions. Important items include:
- Sharp, appropriately sized elevators for reflecting the soft tissues (Figure 9) and winged elevators or luxators for elevation of the roots in question
- Root tip picks, if needed
- Extraction forceps (Figure 10)
- New, appropriately sized dental burs for tooth sectioning, removing alveolar bone, and smoothing the bone following tooth removal (Figure 11)
Having clean and sterile surgical packs made specifically for dental extractions can ensure all of the hand instruments are ready for use, if needed. Sharpen hand instruments after each use to help maintain their shape, sharpness, and tactile sensitivity (Figure 12).
Proper equipment also includes dental radiography. Regardless of whether the dental radiographs are film or digital, radiographic assessment of teeth is the most important diagnostic information needed to make the surgery as straightforward as possible.
Expose the Tooth Extraction Site
For a successful extraction, make sure to expose the alveolar bone and tooth root(s). When removing alveolar bone over selected roots, a rule of thumb is to remove one-half to two-thirds of the bone covering the root surface.
Ultimately, the goal is to remove as much bone as necessary to remove the tooth roots without being overly aggressive. Removing too much bone can compromise the surrounding hard and soft tissue structures associated with the tooth.
Surgical extraction of the selected tooth can be facilitated by:
- Creating a mucoperiosteal flap
- Removing an adequate amount of bone
- Ensuring appropriate sectioning of the tooth over individual roots, when necessary
Consider an appropriate mucoperiosteal flap design with either a single releasing incision or a double releasing incision. The releasing incisions should be divergent to allow exposure of the alveolar bone, but the incision should not be created directly over the area where the bone is removed. This design also helps allow for tension-free closure over the extraction site.
An extraction attempted with limited exposure of bone can damage surrounding soft tissue structures, the mucoperiosteal flap, and the bone adjacent to the selected tooth.10 Limited exposure also increases the risk of root fracture during elevation.
Avoid complications associated with surgical tooth extractions by planning carefully and having a general knowledge of canine and feline dentition and tooth root numbers. Using dental radiographs to assess the root structure and surrounding bone is vital to planning an appropriate approach to tooth extraction.
With enough time scheduled for the procedure and proper equipment, including sharp instruments and new burs, the surgeon can surgically extract teeth as safely as possible. Carefully preparing the mucoperiosteal flap over the selected tooth provides the visibility needed to remove an appropriate amount of alveolar bone, elevate the tooth roots, extract the roots from the oral cavity, and create a tension-free closure.
- Holmstrom SE, Fitch PF, Eisner ER. Exodontics. In: Holmstrom SE, Fitch PF, Eisner ER, eds. Veterinary Dental Techniques for the Small Animal Practitioner. 3rd ed. Philadelphia: Saunders; 2004:291-338.
- Wiggs RB, Lobprise HB. Oral surgery. In: Wiggs RB, Lobprise HB, eds. Veterinary Dentistry Principles and Practice. Philadelphia: Lippincott-Raven; 1997:232-258.
- Wiggs RB, Lobprise HB. Oral anatomy and physiology. In: Wiggs RB, Lobprise HB, eds. Veterinary Dentistry Principles and Practice. Philadelphia: Lippincott-Raven; 1997:55-86.
- Lewis JR, Reiter AM. Anatomy and physiology. In: Niemiec BA, ed. Small Animal Dental, Oral & Maxillofacial Disease. Boca Raton: Manson; 2013:9-38.
- Wiggs RB, Lobprise HB. Oral examination and diagnosis. In: Wiggs RB, Lobprise HB, eds. Veterinary Dentistry Principles and Practice. Philadelphia: Lippincott-Raven; 1997:87-103.
- Verstraete FJ, Terpak CH. Anatomic variations in the dentition of the domestic cat. J Vet Dent 1997;14:137-140.
- Pavlica Z, Erjavec V, et al. Teeth abnormalities in the dog. Acta Vet Brno 2001;70:65-72.
- Wiggs RB, Lobprise HB. Dental and oral radiology. In: Wiggs RB, Lobprise HB, eds. Veterinary Dentistry Principles and Practice. Philadelphia: Lippincott-Raven; 1997:140-166.
- Evans HE. Systemic arteries, aortic arch. In: Evans HE, ed. Miller’s Anatomy of the Dog. 3rd ed. Philadelphia: Saunders; 1993:602-645.
- Peterson LJ. Prevention and management of surgical complications. In: Peterson LJ, Ellis III E, Hupp HR, Tucker MR, eds. Contemporary Oral and Maxillofacial Surgery. 4th ed. St. Louis: Mosby; 2003:221-235.