33rd Annual Scientific Meeting proceedings

Maxillofacial surgery has evolved in the last 20 years along with surgery on other body systems to recognise that minimally invasive techniques once mastered have reduced morbidity and complications, with reduced convalescent times.  Reports in the literature have indicated that uncomplicated extraction of dentition per os has a greater success rate than other more invasive techniques such as dental repulsion and extraction via alveolar buccotomy ^1-6.  Despite more dental extraction being performed by more individuals to a higher level recent large number publications are scant and those papers reporting comparative techniques involve limited numbers and have an intrinsic bias in case selection. The majority of cases selected for surgical extractions are complex extractions involving teeth with complex dental fractures, pathological disease or dysplasia.  Therefore the clinician treating complex extractions should be aware of and be proficient at all techniques in addition to uncomplicated extraction per os in order to optimise technique selection. The evolution of minimally invasive techniques ⁷ that preserve the integrity of the dental alveolus, and the development of instrumentation to support these have dramatically reduced the need for open or retrograde surgical extractions.

Nevertheless, there are occasions when the minimally invasive extraction techniques do not offer a practical solution.    For incompletely erupted teeth, dysplastic teeth or ankylosed teeth exposure of the dental alveolus is sometime necessary. Traditional dental repulsion via a trephined osteotomy without prior luxation is largely obsolete in modern dental extraction.   Minimally invasive repulsion (MIR) is nowadays aided by radiography, after prior luxation and creates a precise osteotomy in the alveolus. This can often be performed in sedated conscious animals with regional analgesia and should not be directly compared with the more traditional method. Traditional repulsion⁸, that involves traumatic damage to the alveolar bone, and inefficient percussion to separate the periodontal ligament both of which cause unacceptable collateral trauma and side effects including chronic fistulae, even though it is sometimes performed in sedated horses⁹.

In teeth that have yet to erupt or those with obstruction by adjacent teeth preventing eruption, access to the clinical crown is limited.  Extraction of the whole tooth along the eruption pathway is physically impeded. The development of some instrumentation used with oroscopic guidance to section such teeth, or reconstruct has provided a solution for some cases ^{10, 11}. The preservation of the alveolus using orthograde dental sectioning makes it an attractive possibility, although a high skill level is required and currently available instrumentation for sectioning a 9cm long tooth is not universally effective.  Exposure of the reserve crown of the tooth is sometimes necessary to facilitate sectioning accurately order to luxate the tooth and remove dental sections via the surgical site or per os. Extraction of teeth via a lateral buccotomy is traditionally performed in anaesthetised horses and has been used for removal of the first four mandibular teeth, and the first three maxillary teeth ^{12, 13}.  This is an effective controlled way of exposing and sectioning such teeth, and is necessary for unerupted or impacted teeth. The main drawbacks are the risk of damage to overlying soft tissue anatomy, the limited exposure of some teeth and the high likelihood of incisional dehiscence due to the challenge of sealing an incomplete alveolus from oral contamination.  Despite acceptable long-term outcomes, this technique has been superceded in many cases by using minimally invasive per os extraction (MTE) that involves using a trans-buccal cannula to luxate the tooth or by using dental sectioning techniques per os. The last two mandibular teeth (-10’s,-11’s) can be removed using a “vertical” buccotomy with a skin incision parallel with the long axis of the tooth and then dissecting through the masseter. This is followed by a buccal alveolar osteotomy to enable sectioning and elevation of the tooth. Retrograde surgical techniques such as these remain valid for non-erupted caudal mandibular molars or those fractured subgingivally where there is no clinical crown visible ^12-14. However, radiographically-guided MIR techniques can be preferable for some of these cases. Alveolar healing after a buccotomy/alveolar ostectomy is problematic due to instability of any implant and saliva and food contamination. Healing can be improved by using a modification of the traditional technique whereby the osteotomy over the apex preserves the bone of the alveolar crest, This facilitates alveolar sealing, preserves soft tissues and reduces incisional dehiscence.

Extraction of dentition via a sinus flap or trephined osteotomy, as historically practiced is rarely performed nowadays. The majority of sinus surgery is performed via keyhole osteotomies under endoscopic guidance, and has superceded the need for sinus flap osteotomies in many clinics ^19-23. Techniques for performing sinus flaps are well-described elsewhere ^22-24 and minimally invasive sinoscopic techniques are widely utilised and portal location can be guided using three dimensional imaging such as CT or endoscopically. Nevertheless in very chronic cases where there is dysplastic dentition, orosinus fistulation resulting paranasal sinuses being filled with inspissated material or food a sinus flap osteotomy is needed to physically excavate the exudates and enable visualisation of the sinuses.   Wherever possible, if there is a dental cause the exodontia is performed first and the sinus surgery done as a subsequent staged procedure. Severely dysplastic teeth may need a combination approach involving a sinus flap osteotomy to expose and section a tooth followed by removal of the apex of the tooth via the surgical site and the crown per os²⁵. These cases take careful planning, often involve multiple procedures, commonly necessitate the horse to be anaesthetised, have a high incidence of complications and can lead to disappointment for all involved. Dental extraction has historically been associated with unacceptable complications and by using high quality diagnostic imaging, careful planning and appropriate technique selection and execution such complications can be minimised.

References

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