33rd Annual Scientific Meeting proceedings

Introduction
Oral dental extraction is usually the fastest and least invasive method of tooth removal with a lower complication rate than other techniques^1,2. For this reason, this technique should always be the surgical method of choice, even if the initial situation is complicated. Even if the oral forceps extraction is finally not successful, loosening of the tooth will facilitate any further surgery.

Difficult situations for oral extraction (1)
When the clinical crown is missing completely, whether caused by the underlying disease or a previous surgery, this excludes the option of oral forceps extraction. In this case, other methods that are performed under endoscopic guidance need to be considered:

Intraoral tooth sectioning
Intraoral sectioning is a newer surgical method with the aim of dissecting a multi-rooted tooth to a single-rooted entity³. This creates space in the alveolus so that the individual isolated fragments can be detached and removed from the alveolus one after the other. Dental handpieces with water flushing are required, in which burrs of different lengths could be inserted. Additional suction is essential for the intraoral segmentation of mandibular cheek teeth in order to free the alveolus of water and blood to enable working under visual control. Additional radiographic guidance is critical to ensure that the cut is aligned properly.

A mandibular cheek tooth is divided with one transverse cut between the mesial and distal root. The maxillary tooth with its three roots is first dissected sagittally along the infundibula, usually followed by a transverse second cut.

It is important to loosen the tooth as much as possible prior to segmentation. The technique of sectioning itself and the coordination of burr, endoscope and suction must be carefully trained before first applied to living horses, in order to cause little to no damage to the alveolus during the procedure. Otherwise dry sockets and sequestration are common complications after tooth sectioning.

In horses that shake their heads, chew and move their tongues during the procedure despite the best possible sedation and analgesia, intraoral sectioning is difficult or even impossible, depending on which cheek tooth is affected.

Screw extraction via minimally invasive buccotomy⁴
With this technique, the tooth is accessed from the outside of the mouth via the cheek. Depending on the position of the tooth in the row and with good planning, the buccotomy is performed directly at the level of the tooth that is to be removed. The surgical instruments have improved significantly in recent years. If the screw can be placed in the tooth without damaging the alveolus and if the thread does not strip during the extraction, this method is as minimally invasive as oral forceps extraction.

If the thread strips during the attempt of extraction, either a threaded rod with a larger diameter can be used, or the tooth can be removed using elevators, which are also inserted through the buccotomy.

The buccal access to the non-sterile oral cavity can lead to surgical site infection in the area of the buccotomy. The Incisura vasorum facialium and the branches of the facial nerve must be meticulously avoided to prevent bleeding, salivary duct fistula and facial paresis. The optimal access to the most frequently extracted tooth Triadan 09 is often exactly at the level of the Incisura vasorum. Access to the teeth Triadan 10 and 11 is technically challenging and more prone to complications than teeth located more mesially. Thermal damage to the surrounding tissue during drilling is possible if cooling is not adequate.

Intraoral screw extraction
If a root fragment remains in the socket after oral tooth extraction that cannot be reached with forceps but is too large to be removed with elevators, the fragment can be removed using “atypical” intraoral screw extraction. For this purpose, a hole is drilled in the centre of the remaining root with a diastema burr, and a (Spax-) screw is inserted and tightened by hand. The root can then be pulled out of the socket with this screw. This method only works if the fragment has been well loosened prior to the extraction attempt.

Difficult situations for oral extraction (2)
Complicated partial crown fractures with significant loss of the clinical crown can complicate the positioning of the extraction forceps, usually leading to further damage of the crown with a subsequent fracture during the attempt of extraction. Therefore, in such cases, the crown should be "prepared" as best as possible before applying the forceps. The shape of a fractured crown can be modified by floating to get a better angle or plain for the forceps. Another option is the application of a thin layer of polymethyl-methacrylate (PMMA) to stabilize the crown in order to avoid further chipping of tooth material due to local pressure or movement of the forceps.

Teeth with deep defects of the clinical crown should also be stabilized for extraction. For this purpose, the chewed food is removed from the defect of the weakened tooth and this is filled with PMMA. Maxillary teeth fractured sagittally through the infundibula in older horses often have so-called splay roots. In these cases, the central stabilization of the tooth with PMMA tends not to help with extraction and should mostly be avoided.

A reverse hypomochleon should be used when the roots (especially in the mandible) slope distally. In these cases, a normal hypomochleon can lead to root fractures due to the wrong pull-out angle.

With such angled teeth, a mesial and distal partial coronectomy⁵ in the interproximal spaces can help loosen the tooth carefully. Dental material should be removed to the level of the crestal bone, but only from the tooth being extracted. By gaining 3-4 mm of space, crown interlock is reduced and extraction is often possible without resistance and thus without a fracture.

Conclusion
On the one hand, it is important to investigate how the initial situation of a diseased tooth can be improved so that oral extraction may be successful. On the other hand, one should reveal issues that make oral extraction fail. This can be a missing clinical crown or an abnormal tooth shape that makes it difficult to extract the tooth, or severe damage to the crown that makes dental substance unstable.

The surgeon should have all potential methods for tooth removal in mind and combine them as best as possible, which also means switching back and forth between the individual methods if necessary.

The aim must always be to work as minimally invasive as possible on the alveolus and surrounding tissues.

References

1. Dixon PM, Dacre I, Dacre K, Tremaine WH, McCann J, Barakzai S. Standing oral extraction of cheek teeth in 100 horses (1998-2003). Equine Vet J 2005; 37(2): 105-112.
2. Caramello V, Zarucco L, Foster D, Boston R, Stefanovski D, Orsini JA. Equine cheek tooth extraction: Comparison of outcomes for five extraction methods. Equine Vet J 2020; 52(2): 181-186.
3. Henry T, Stoll M, Rice M. Equine Exodontia – Intraoral Tooth Sectioning. In: Equine Dentistry and Maxillofacial Surgery. Easley J, Dixon P, du Toit N eds. Cambridge Scholars Publishing. 2022: 545-547.
4. Langeneckert F, Witte T, Schellenberger F, Czech C, Aebischer D, Vidondo B, Koch C. Cheek Tooth Extraction Via a Minimally Invasive Transbuccal Approach and Intradental Screw Placement in 54 Equids. Vet Surg 2015; 44(8): 1012-1020.
5. Rice MK, Henry TJ. Standing intraoral extractions of cheek teeth aided by partial crown removal in 165 horses (2010-2016). Equine Vet J 2017; 50(1): 48-53.