It is clear that due to the inadequate teaching of veterinary dentistry in our universities (which is the subject of a separate future article) that many veterinary surgeons find dental extractions a significant challenge. Nothing can replace practical hands-on training on cadaver specimens. In the UK, we are lucky to have CPD organisations ethically sourcing specimens that can be used for postgraduate training. The aim of this article is to act as a theoretical supplement to this practical training.
Having identified a tooth which requires extraction, the tooth needs to be cleaned. You may ask why a tooth that is to be extracted needs to be scaled, but the consequences of irretrievably dropping a lump of infected calculus deep into an alveolar socket are pretty clear. A non-healing sinus tract can be easily avoided by a few seconds with an ultrasonic scaler. Whilst we cannot make the mouth a sterile operating environment, a 2 percent chlorhexidine gluconate wash to the gingiva surrounding the planned extraction site will reduce the bacterial burden considerably.
What keeps teeth in place?
The junctional epithelium (JE) represents the soft tissue attachment of the tooth to the surrounding gingival tissues. The JE lies at the base of the gingival sulcus or pocket and is fairly unique in having two basal laminae. The external basal lamina lies adjacent to the gingival connective tissue; from this “normal” basal lamina mitotic divisions (with a high cell turnover of only four to six days) create new epithelial cells which are desquamated into the sulcus. The constant shedding of these cells helps remove surface bacteria, plaque and debris from the periodontal tissues. The JE’s other basal lamina (the internal basal lamina) lies adjacent to the tooth itself. The internal basal lamina is itself split into two layers: a lamina densa, which has organic fibril attachments onto the enamel or the cementum of the tooth, and the lamina lucida, which has hemi-desmosome binding onto the epithelial cells.
Authors vary, but it is likely that the JE is responsible for 10 to 15 percent of the strength of the attachment of a tooth. There are many of us that will have recognised that attachment strength when extracting the last maxillary molar in dogs and a large flap of gingiva is created when the extracted tooth is pulled forwards.
Accordingly, taking a sharp scalpel (a 15c blade is my preferred option) and running it circumferentially around the tooth deep in the periodontal pocket to sever the JE (Figure 1) will reduce your workload in extracting the tooth considerably.
You may wish to consider using a circular or octagonal scalpel handle – it is surprising how this facilitates the operative ease compared to using a standard handle.
We do this structure a disservice by thinking of it as THE periodontal ligament. The reality is that there are a number of different fibre groups running in different alignments, each providing resilience against various directional forces. The majority of the fibres run from the alveolar bone to the cementum; however, some run between teeth, some from the tooth to the gingiva or to the outer periosteum and others encircle the tooth pulling the periodontal pocket tightly closed. The fibres deeply embed into the alveolar bone and then into the cementum (indeed some of the cementum is formed from the fibre cells).
The role of the periodontal ligament is to act as a shock absorber during normal biting. Without this shock absorber (and the incorporated sensory nerve endings providing bite force feedback) any hard bite would result in either a tooth or an alveolar fracture. This shock absorber quality is important during extractions. If a tooth is simply “waggled” in the socket, the periodontal ligament simply performs its normal function and no damage is incurred. To extract the tooth, the periodontal ligament fibres must either be cut, or be so damaged and fatigued that they rupture.
In my practical classes, I encourage participants to choose a song that (however fast they sing it) will take 20 to 30 seconds to deliver. This can then act as a timer to ensure that forces are applied to the ligament for at least that timespan in order to weaken and break the periodontal ligament fibres. Songs have included the Romanian national anthem to a very politically incorrect modern version of “The Grand Old Duke of York”.
As many that know me will testify, I am one of the least patient people you could meet. However, I know that rupturing the periodontal ligament is a time when I have to be patient. Steady force is applied to a tooth and that force is then maintained for 20 to 30 seconds. Force is then applied in a different direction and the process is repeated. Initially nothing seems to be happening – but as the fibres break down, suddenly significant movement is achieved and the tooth progresses towards luxation and extraction. Rushing this process is when tooth root fractures will occur; being patient will have the reward of a much faster overall procedure.
Different types of forces can be applied to teeth to strain the periodontal ligament, such as ramping (Figure 2), rotation (Figure 3) and fulcrum leverage (Figure 4).
Elevators versus luxator-type instruments
Elevators (Figure 5A) are the traditional instrument seen in veterinary practice. They are based on the Coupland bone chisel and typically have a 45-degree working angle at the working tip (Figure 5B). They are robust instruments and may have been lurking in the dental kit since the 1970s.
The profile of elevators means that they can’t enter the periodontal space without causing disruption of the alveolar bone. However, once inserted they can be used to provide the forces required to fatigue the periodontal ligament.
Luxator-type instruments (Figure 6A) in comparison are made from softer steel, with a much finer working tip (Figure 6B). As such, they are more susceptible to damage and should not be used as elevators.
Their profile, however, means that the instrument can be inserted into the periodontal space. The instruments are inserted vertically and used to cut the periodontal fibres. Ideally the instrument is then withdrawn, rotated slightly and reinserted to cut a fresh section of fibres. Far less force is required when using these instruments.
The ideal sequence is severing the junctional epithelium, followed by the luxator cutting some of the periodontal fibres. The elevator is then inserted, and rotation and other forces used to fatigue, weaken and rupture the periodontal fibres. As more access into the periodontal space is gained, the luxator can be used again to cut further fibres, followed by further application of the elevator until tooth luxation.
As the instruments are designed to enter the periodontal space, it is essential to have a full range of curvatures to match the different profiles of the roots that will be encountered (Figure 7).
A surgical gingival flap is used to ease access and visibility and to allow alveolar bone removal if required. Whilst much of the gingiva derives its blood supply from the underlying alveolar bone, care should be taken in flap design to preserve its vascularity.
See step-by-step guide below.
These are performed without creating a gingival flap. All sutures used should be without any tension, to avoid the almost inevitable breakdown of closing with tension.
Taking a logical approach to dental extractions, using the correct equipment (and keeping it sharp and well maintained), using controlled forces – with an awareness of dental anatomy and biomechanics – will make extractions a lot easier. Most importantly be patient – and sing your extraction song!