Dental extractions

Dental extractions are true surgical procedures which the veterinary dentist often uses to resolve some disorders of the oral cavity. It must be understood that a dental extraction is an irreversible loss of an anatomical element (amputation), however this procedure is often necessary because other techniques aimed at preserving the teeth or parts of them would involve a series of post-operative and domiciliary treatments that domestic carnivores would only rarely accept, even if their owners were prepared to put them into practice.

The patient undergoing a dental extraction should be prepared in the same way as for a normal surgical operation, and carefully evaluated. In order to determine the animal’s state of health, besides the normal general clinical examination, the patient should undergo the investigations considered necessary for general anaesthesia, thus ensuring the best probability of survival. Laboratory tests (full blood count, basic biochemical tests, a coagulation screen, etc.) should be performed, the respiratory and cardiovascular systems assessed and any other diagnostic investigations thought to be useful should be carried out.

At the time of giving the pre-anaesthesia, the patient should be administered an antibiotic intravenously (for example, cephalosporin 25 mg/kg, spiramycin 30 mg/kg or other antibiotic considered appropriate).

Once the most suitable anaesthetic procedure has been decided, a peripheral vein should be incannulated and the animal intubated in order to guarantee airway patency, even if it is decided to use an injectable anaesthesia.

Once the patient has been positioned, care should be taken to prevent excessive cooling of the body by isolating the animal from the operating table: this can be done by using surgical mattresses and by wrapping the animal with materials limiting heat dispersion (nylon, aluminium foil, reflective drapes, etc.). Appropriate X-rays are performed and the oral cavity is disinfected with suitable products (for example, chlorhexidine in aqueous solution 0.10-0.20%) before the tooth is extracted.

REASONS FOR TEETH REMOVAL

The most frequent causes of teeth extraction by a veterinary dentist are:

• Periodontal disease (Fig. 1): this is probably the most common disorder in the dog, and is also frequent in the cat.This pathological condition leads to progressive destruction of the periodontal ligament and resorption of the alveolar bone, enabling the teeth to move; the final outcome of this process is loss of a tooth or teeth (spontaneous healing). Extraction of affected teeth is necessary in advanced stages of the disease or when the animal’s owner refuses to care for the daily oral hygiene of his or her animal.

• Feline odontoclastic resorptive lesion: attempts to preserve teeth affected by feline odontoclastic resorptive lesion (FORL) with conservative techniques are destined to fail. When the FORL is beyond the first stage, extraction of the teeth involved must be considered. In the presence of ankylosis and/or root resorption, complete extraction of the tooth may be difficult or even impossible; in these cases voluntary amputation of the crown may be useful, followed by radiographic monitoring until the complete resorption of the root left in situ has been confirmed.

• Chronic feline stomatitis: if this condition cannot be controlled by medical treatment and rigorous oral hygiene, radical extraction of the whole tooth can resolve the problem. The canines (useful for prehension of food) are usually spared, although if these teeth have a strong influence in the disease, they too should be removed.

• Chronic stomatitis in the dog (ulcerative stomatitis, necrotising-ulcerative stomatitis): although these disorders seemed to be limited to some breeds (Poodle, Maltese, etc.), it is now recognized that all dogs can develop severe inflammation of soft tissues, a phenomenon related to the cytotoxicity of the catabolites of the bacterial flora of dental plaque. In this case too, if the condition cannot be controlled with medical treatment and/or rigorous oral hygiene, dental extraction is recommended.

• Caries: this is a rare condition in dogs and does not occur in cats. When conservative treatment is not possible, extraction of the affected tooth or teeth must be considered.
  
  
• Supernumerary teeth and persistent deciduous teethcause overcrowding, which facilitates the apposition of plaque and tartar or the development of malocclusions. Ectopic teeth and retained teeth can act as foreign bodies (for example, when they are present in the nasal cavities they cause chronic rhinitis).
  
  
• Fractures of the dental crownwhich involve the root creating periodontal pockets: when a crown-root fracture, complicated or not by exposure of tooth pulp, causes the formation of a periodontal pocket, it must be assessed whether it will be possible to manage the pocket with domiciliary oral hygiene. If it is considered that the defect caused by the fracture will not be manageable, extraction of the tooth is advised. Likewise, dental extraction is necessary for complicated crown fractures (with exposure of the pulp) when the animal’s owner refuses conservative methods of management.
  
  

• Malocclusions: when the animal’s owner does not want to undertake effective orthodontic corrections or these are not possible for technical reasons, malocclusions that cause damage to soft tissues can be resolved by extracting the teeth that are creating the problem.
  
  
• Root fractures: fractures of the middle third and the coronal third of the root usually compel extraction or canal treatment of the root left in situ. Extraction is not, however, always necessary for fractures involving the apical third of the root: in these cases, the recommended management is periodic clinical and radiological control of the tooth, without any intervention, given that these fractures usually have a benign evolution.

DENTAL EXTRACTION TECHNIQUES

The techniques used to extract teeth can be divided into non-surgical and surgical; the former involve luxation of the periodontal ligament and removal of the tooth, while the latter require a particular procedure that can be summarised as below:

• creation of a mucogengival flap enabling vision of the part of bone to be dealt with surgically;
• separation of the roots with a turbine-mounted bur (this passage is only used for teeth with multiple roots);
• alveolotomy: asportation of more than two-thirds of the vestibular part of the socket enables even flattened roots to be mobilised and extracted completely, without fracturing them;
• extraction of the tooth;
• alveoloplasty: the contour of the bony socket is remodelled, eliminating sharp points and removing debris;
• suturing: this can be complete or partial; partial sutures are reserved to those cases in which there is periodontal or apical infection.

Simple (non-surgical) dental extractions

Here we describe non-surgical extraction of deciduous teeth and permanent single-rooted teeth which can, in most cases, be extracted without requiring alveolotomy, division of the crown, etc.

Extraction of deciduous teeth
The extraction of deciduous teeth is often considered an emergency because the persistence of milk teeth can lead to the definitive, permanent teeth being incorrectly positioned. Another problem caused by persistent deciduous teeth is dental overcrowding which, over time, can lead to the anomalous deposition of plaque and tartar with consequent development of localised periodontitis (Figs. 10-15).

As for any other extraction, appropriate X-rays should be taken in order to determine the relationships between the teeth, but also to show the degree of resorption of the roots of the deciduous teeth (Figs. 16-20); unfortunately, dental overcrowding often means that several X-rays have to be taken.

Deciduous teeth must be extracted as gently as possible to avoid dental fractures; if the crown is fractured, the root of the tooth may be absorbed very slowly, such that its persistence can cause malpositioning of the permanent teeth. Besides being gentle, the manoeuvres for extracting teeth should also be as non-invasive as possible in order not to cause damage to other nearby permanent teeth.

With regards to canines, an incision is made parallel to the tooth to be extracted and then the tooth is mobilised with an appropriately sized luxator, before being easily removed; the surgical wound is sutured with absorbable 5/0 monofilament thread (Figs. 21-27).

Deciduous incisors can be extracted without cutting the soft tissues, using an adequately sized luxator (Fig. 28).

Extraction of single-rooted teeth

The canines, although single-rooted, are dealt with separately because they require surgical extraction.

The stability of the tooth to be extracted is evaluated. If the tooth is sufficiently mobile, it can be removed using a pair of extraction forceps; if, in contrast, the tooth is stable, it must be mobilised by luxating the periodontal ligament that holds it in the dental socket. Luxation of the ligament can be achieved by gently introducing a luxator between the tooth and the socket until a certain resistance is felt; at this point the instrument is rotated 30 – 40°. This operation must be repeated until the apex of the tooth is almost reached and for the whole circumference of the tooth, in order to break most of the fibres and the periodontal ligament and, thereby, mobilise the tooth which can then be easily removed with a suitable pair of forceps. Dental elevators can be used instead of luxators although they are less effective.

Piezoelectric surgery can be considered as an alternative to the above described luxation techniques: although this type of surgery has higher management costs, it makes dental extraction easier and less traumatic to the surrounding tissues.

The forceps used for an extraction must be chosen so that they best match the shape and size of the tooth to be removed. Once the tooth has been firmly grasped, gentle rotary and extractive movements are made with the forceps, without exercising excessive pressure on the crown of the tooth.

Surgical extractions

Extraction of multi-rooted teeth
The divergence of the roots of multi-rooted teeth makes it impossible for roots of these teeth to be extracted without dividing the crown into as many pieces as there are roots. This division must be performed using turbine-mounted burs starting from the root furcation and working towards the crown and never in the opposite direction. If the furcation is not directly accessible, because it is covered by other structures (bone, gum), it must be reached surgically. When the required divisions have been made, the various interproximal parts of the periodontal ligament are broken, by introducing a tooth elevator (for example, a Bein lever) into the cleft made by the turbine and rotating it gently; the other parts of the periodontal ligament are broken in the same way until all the sectioned parts of the tooth are mobilised well.

Extraction of the first maxillary molar
X-ray evaluation of this tooth is often complicated because its anatomical site leads to overlapping of the roots on the radiograph and it is often necessary to take various X-rays in different projections in order to obtain a complete picture of the situation. The first maxillary molar is located very distally in the oral cavity: in the dog it usually has three roots, whereas in the cat it is usually a single-rooted tooth. Consequently extraction of this tooth in cats is usually simple, whereas various technical difficulties can arise in dogs. In order to section the roots with a turbine-mounted bur, the furcation must be identified, which is not easy for this tooth because of its position; however, based on the shape of the crown, some important landmarks can be established. The furcations correspond to the dips between the cusps: starting from these the cuts are made in the crown to separate the roots. Once the most mesial root has been identified, its periodontal ligament is stretched using a dental luxator in order to allow the tooth to be extracted; when this root has been removed, the second section is made, again with a turbine-mounted bur, to separate the remaining two roots which are then extracted in the same way as the first.

Forceps with a 90° bend are preferentially used for the extraction of this tooth because this facilitates the extractive and rotary movements applied. The rotary movement is particular effective because these roots usually have a round cross-section; in contrast, rotary manoeuvres for teeth or roots with an oval cross-section are ineffective and may even fracture the root within the socket or damage the bony socket itself.

The anatomical defect left by the extraction can be corrected with a mucosal flap taken from the cheek and sutured with separate knotted stitches with absorbable 4/0 or 5/0 monofilament mounted on a triangular reverse cutting needle. In this area of the oral cavity, the mucosa is particularly mobile and lends itself well to this operation.

Extraction of the fourth maxillary premolar (Figs. 29-35)
The fourth maxillary premolar is often affected by disorders necessitating its extraction: fractures caused by masticating hard objects,  accumulation of plaque and tartar responsible for periodontitis, etc.

After having anaesthetised the animals, the necessary X-rays are taken: since this tooth normally has three roots, it is possible that the images of the two most rostral roots (mesial and palatal roots) will overlap. In this case other X-rays must be taken, directing the X-ray beam meso-distally or disto-mesially, in order to obtain a good radiographic picture of the two roots: the technique that best identifies the two rostral roots is S.L.O.B. (same [direction], lingual route, opposite [direction], buccal route).

The standard technique for tooth extraction is modified on the basis of the radiographic pictures: in fact, the presence of anomalies (supernumerary roots, bone resorption, root resorption, particularly curved roots, ankylosed roots, etc.) will steer the veterinarian towards alternative techniques.

After having removed the tartar and prepared the operating field with chlorhexidine or another appropriate product, the furcation between the distal and rostral roots is identified. If the furcation is not visible, a flap must be created and a small amount of bone removed in order to reveal it. The crown is then separated into two parts, in this way rendering it independent from the distal root; the crown must be separated with a bur (ISO 700 series) starting from the furcation. Next, with the help of an elevator introduced into the cut made, the crown is rotated gently: this action separates the two parts of the teeth, dislocating the interproximal part of the periodontal ligament. The action of the elevator mobilises the distal root which can be extracted with the help of appropriate forceps. The same procedure is applied to the rostral part of the tooth, to separate the mesial root from the palatal one, rendering them independent. Then, in the usual way, an appropriately sized elevator is introduced to sever the interproximal part of the periodontal ligament and thus mobilise the stumps which can then be extracted. It is important, also in this case, to leave a part of the crown that can be grasped by the extraction forceps.

The bone is then levelled with appropriate tools (rongeur, turbine-mounted bur, piezoelectrical instruments, etc.) and the area sutured with interrupted knot stitches in resorbable 4/0 or 5/0 monofilament mounted on a triangular, reverse cutting needle; often the mucosa must be detached to obtain a flap large enough to prevent tension on the suture.

Extraction of canines
The canines are teeth with only one root (monoradicular) and are large, being about double the volume of the crown; extraction of these teeth usually involves surgical demolition of a part of the dental socket.

Extraction of the maxillary canine  (Figs. 36-41; Figs. 42, 43, 44, 45, 46, 47, 48, 49, and 50)
With the patient under general anaesthesia, the necessary X-rays are taken and the area is disinfected. A deep incision is made in the mucosa (down to the bone plate), from the apex of the canine to the free gingiva; the incision can be made mesially or distally to the canine itself. The mucoperiosteal flaps are turned back with the help of a periosteal elevator or piezoeletrical surgery and are handled with extreme care since the good outcome of the final sutures is dependent on the integrity of these flaps. Bleeding is staunched and the bone is visualised; the vestibular part of the bony socket of the canine is removed with appropriate instruments (turbine-mounted rose-head bur or pear-shaped bur or, if available, with the help of piezoelectrical surgery). Once an adequate amount of socket bone has been removed, the canine can be dislocated with a dental elevator. The mucoperiosteal flap is sutured with interrupted knot stitches in absorbable 4/0 or 5/0 monofilament mounted on a triangular, reverse cutting needle. Rapidly absorbed thread (poliglecaprone) is better tolerated in the oral cavity of domestic carnivores than more slowly absorbed threads (polydioxanone, etc.).

Extraction of the inferior canine
The inferior canines are teeth with a large root, implanted in the mandibular bone which is relatively thin. These teeth must be extracted with particularly delicate and non-destructive manoeuvres in order not to fracture the mandible. When there is radiological evidence of periodontal attachment loss (PAL), an attempt can be made to extract the inferior canine using dental luxators (as described for the extraction of single-rooted teeth); if, on the other hand, the tooth is stable, the extraction can only be performed after an alveolotomy, preferably removing bone from the mesial face of the mandible, until the tooth is sufficiently mobilised to enable its extraction.

Extraction of the first inferior molar (Figs. 51-58)
Extraction of this tooth is complicated by various anatomical factors:

• it is a very large tooth implanted in the mandible: overly destructive manoeuvres could snap the bone, creating a difficult-to-manage fracture;
• the slight divergence of the two roots and their latero-lateral flattening means that these roots must be separated in order to be able to extract the tooth;
• the rostral root of the tooth has a deep groove on the interproximal face that, together with the flattened face, limits the rotary movements that are normally used to extract teeth;
• the fact that the apices are extremely close to the mandibular canal means that manoeuvres must be very delicate in order not to damage the tissuse contained.

After having anaesthetised the animal and taken the necessary X-rays and disinfected the area, the gingiva and the mucosa are widely detached in order to create a flap that allows access to the furcation; if this cannot be identified, a small part of bone is demolished in order to identify it. A cut is made with a bur (for example, a tungsten ISO 700 fissure bur) from the furcation in a coronal direction to separate the crown in two parts, thus rendering the distal root independent from the rostral one. The mucoperiosteal flaps are turned back with the help of a periosteal elevator or piezoeletrical surgery and are handled with extreme care since the good outcome of the final sutures is dependent on the integrity of these flaps. Bleeding is staunched and the bone is visualised; the vestibular part of the bony socket is removed with appropriate instruments (turbine-mounted rose-head bur or pear-shaped bur or, if available, with the help of piezoelectrical surgery). If an adequate amount of socket bone has been removed, it will be possible to dislocate the two dental stumps by introducing an elevator into the cut made in the crown. The wound is sutured, as usual, with interrupted knot stitches in absorbable 4/0 or 5/0 monofilament mounted on a triangular, reverse cutting needle; the size of the flap created should not be cause of concern. Indeed, the larger the flap, the less tension the suture will be subjected to.

Extraction of ankylosed teeth
Dental ankylosis is the fusion of a root to the bony tooth socket: this can occur for various reasons and be more or less extensive. Independently of this, the loss of part of the periodontal ligament, replaced by hard tissue, often leads to fracture of the ankylotic tooth by limiting or preventing the movement normally allowed by the ligament.

The normal techniques used for dental extraction, which involve severing the periodontal ligament, cannot be used in these cases. It is, therefore, necessary that, after careful radiographic assessment, the bone is exposed by the creation of a mucoperiosteal flap and then destroyed – using appropriate instruments (turbine-mounted rose-head or pear-shaped bur or, if available, with the help of piezoeletrical surgery) – until the tooth to be extracted has been freed.

Pulverisation of the ankylotic root with burs (ISO 329-330-331) is a technique to avoid because it is very difficult to evaluate to what depth to push the bur without causing damage to nearby anatomical structures (mandibular canal, etc.).

Extraction of roots
The presence of retained roots must be determined by radiography; even though fistulae may raise the suspicion of retained roots, only radiography can confirm the diagnostic suspicion. The surgical technique to use varies depending on the root to be extracted and its anatomical position: sometimes it is sufficient to use elevators and root forceps, while in other cases sophisticated surgical techniques are necessary in order to limit damage to surrounding tissues.

It is, however, necessary to compare the anatomical specimen extracted with the X-ray images; at any rate, it is always a good idea to carry out a post-operative X-rays to check the good outcome of the surgery.

COMPLICATIONS

Besides events related to the anaesthesia, it should be remembered that some dental extractions can be complicated by the site of the teeth (ectopic or malpositioned); the roots may be anomalous (curved, supernumerary or ankylotic), etc. These and other situations must be evaluated in advance through precise radiographs before starting surgery. Other complications that occur frequently are fracture of the crown and/or of the root of the tooth to be extracted and difficult-to-manage bleeding. Finally, dental luxators and elevators must be used with prudence in order not to cause wounds or damage.

POST-OPERATIVE MANAGEMENT

Animals that have undergone dental extractions should be managed in the same way as post-operative patients: they should be kept in a comfortable environment and be given sufficient analgesia to match the surgical procedures carried out. The return to spontaneous feeding should be encouraged. Antibiotics can be administered, if necessary.

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