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Treating traumatic injuries of canine teeth in cats

Background: Cats frequently suffer dental trauma to their canine teeth, as a result of road traffic accidents, falls or fights with other animals. However, there is limited veterinary literature about the incidence and treatment options for such injuries.

Aim of the article: This article outlines how to treat traumatic injuries of canine teeth in cats by using endodontic or extraction techniques.

Matthew Oxford qualified from the University of Edinburgh in 2005.

He set up the New Forest Veterinary Dental Service in 2011, providing referral veterinary dental and oral surgery procedures. He is also a lecturer in veterinary dentistry at Surrey and Bristol universities. He holds the European certificate in small animal surgery.

KEY LEARNING OUTCOMESAfter reading this article, you should understand:

▢ The prevalence and progression of traumatic dental injuries; ▢ The link between periapical pathology and traumatic dental

injuries; ▢ How tooth resorption result from or coincides with traumatic

dental injuries; ▢ Treatment options for traumatic dental injuries; ▢ The prognosis following each treatment of traumatic dental

injuries.

doi: 10.1136/inp.m886

THE incidence and treatment options for traumatic dental injuries in domestic cats are poorly documented in the veterinary literature. There are a handful of publications concerning injuries in dogs and numerous publications regarding cases in people (Andreasen and Andreasen 1990, Menzies and others 2014). From clinical work we know that cats suffer dental trauma which may be as a result of road traffic accidents (Fig 1), falls or altercations with other animals. However, because of the lifestyle of cats, the specific cause of an injury is often unknown. Treatment options remain the same as for other species where pulp exposure is present, and include either extraction or endodontic treatment.

Pathology of pulp exposureThe prevalence of traumatic dental injuries in dogs and cats is 26.2 per cent (Soukup and others 2015). Injuries frequently affect canine teeth as these can be superficial when a cat’s mouth is closed. When the mouth is open, these teeth sit in a prominent position in the rostral part of the mouth as an isolated structure (Robinson 1976). Dental injuries are often clinically significant in cats, as the pulp sits in a superficial

position within the cusp of the canine tooth, meaning that even a relatively small loss of crown structure can result in exposure of the pulp (Fig 2).

Once exposed, pulp pathology progresses along a relatively predictable path, as outlined in other articles (Oxford 2014). Pulp exposure can lead to infection of the pulp within the pulp chamber and root canal. This pulp infection progresses to pulp necrosis and the necrotic pulp within the root canal will then stimulate an inflammatory response in the tissues around the root, resulting in periradicular bone loss (Fig 3) and/or root resorption (Oxford 2014).

Dental pathology in cats is also complicated by tooth resorption (Fig 4) (Gorrel 2015). This common pathology may be present as a result of the dental trauma through induced inflammation following endodontic disease; may have predisposed the tooth to traumatic injury through crown weakening following inflammatory resorption; or may be concurrently present simply through coincidence. It is beyond the scope of this article to fully describe tooth resorption but its effect on treatment decision making will be discussed.

TreatmentExtraction Extraction of teeth in cats affected by endodontic disease remains a good treatment option. However, complications frequently arise from dental extractions in cats and these must be fully explained to owners before treatment is carried out. As mentioned above, the progression of endodontic disease to periradicular disease is caused by the pulp within the tooth becoming necrotic. Extraction of the affected tooth will remove the diseased pulp and therefore the periradicular tissues will heal. It is beyond the scope of this article to discuss techniques for dental extractions and readers are referred to Oxford (2018).

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ComplicationsComplications of dental extractions are well documented and include:■■ Fracture of the roots and their unintentional retention; ■■ Haemorrhage; ■■ Trauma to adjacent dental and soft tissues; ■■ Sublingual oedema and salivary mucoceles; ■■ Trauma to the eye (Duke and others 2014); ■■ Reduction in alveolar bone height (Blanco and others 2011); ■■ Fracture of the jaw or alveolus; ■■ Oronasal communication; ■■ Trauma from opposing teeth following extraction; ■■ Wound dehiscence.

Trauma from opposing teeth following extraction and fracture of the jaw or alveolus are particularly relevant to canine extractions in cats and will be discussed further below.

Trauma from opposing teeth following extractionTrauma from opposing teeth following extraction of the maxillary canine tooth in cats is common. Following extraction of this tooth, and because of loss of adjacent bone and gingival tissue, the upper lip no longer has any support to maintain its position. Therefore, following extraction of the maxillary canine tooth, the lip will sag into the mouth and the lip can then be traumatised by the opposing mandibular canine tooth when

Fig 1: Complicated crown-root fracture of the left maxillary canine tooth in a cat following a road traffic accident

Fig 2: Crown fracture in a cat. Even though this is a very superficial fracture, the pulp is still exposed and the tooth requires treatment

Fig 3: (a) Complicated crown fracture of the right mandibular canine tooth. (b) Radiograph of the same tooth demonstrating a wide root canal consistent with pulp necrosis, and extensive periradicular bone loss

(a) (b)

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the cat has its mouth closed. This chronic trauma can lead to ulceration and thickening of the upper lip (Fig 5). This may require additional treatment such as extraction, or crown height reduction with endodontic treatment of the mandibular canine tooth (Reiter 2011).

Fracture of the jaw or alveolusFracture of the jaw or alveolus is a complication that can be seen during the extraction of a mandibular canine tooth. The alveolar bone around the mandibular canine tooth can be thin, especially between the alveolus and the mandibular symphysis. Inappropriate force applied during the extraction of this tooth can result in a fracture of the mandible. Fractures of the bone can be challenging to stabilise due to there being very little bone or dental structures to apply orthopaedic fixation to.

Endodontic treatmentEndodontic (root canal) treatment of fractured canine teeth in cats provides a good alternative to

extraction and can eliminate the complications seen with extraction. The procedure and clinical assessment of endodontic treatment in cats is poorly documented in the veterinary literature; there has only been one significant study published (Str0m and others 2018), and so further research is needed in this area.

Root canal treatment in animals with brachydont teeth broadly follows the principles of treatment of teeth in people (Oxford 2014): bacteria and pulp tissue are removed from the root canal and pulp chamber, and then these structures are filled (obturated) and the crown sealed, preventing further bacterial infection of the root canal. The process of endodontic treatment is a combination of chemical and mechanical debridement and disinfection of the root canal; chemical disinfection and dissolution of tissue with disinfectants, such as sodium hypochlorite, along with mechanical removal of infected soft and dental hard tissue. These principles also apply to endodontic treatment of teeth in cats.

There are some differences in feline endodontic anatomy that need to be considered in root canal treatment in these patients. Largely due to the size and shape of the teeth, root canal treatment is limited to canine teeth in cats.

The pulp chamber and root canal in canine teeth in cats have a shape similar to that of a conical flask, with a narrow ‘neck’ (the pulp chamber) which opens into a wide root canal. This is particularly prominent in younger cats with less mature teeth where the root canal is wider and dentine relatively thinner. This anatomical shape means that even in older cats, full mechanical contact with all of the internal surfaces of the root canal can be difficult, as only relatively thin endodontic files can be passed through the pulp chamber (Figs

Fig 4: (a) Complicated crown fracture of the right mandibular canine tooth. (b) Radiograph of the same tooth demonstrating extensive type 2 tooth resorption in response to the traumatic pathology. Owing to the extensive destruction of the root structures, this tooth was not suitable for root canal treatment and so extraction was required

(a) (b)

Fig 5: Ulcerative lesion of the right upper lip following extraction of the right maxillary canine tooth

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6, 7). Therefore, much more emphasis is placed on chemical debridement of the root canal. The reduction in mechanical debridement may affect the ability to fully debride the root canal and may affect the ability to achieve a successful outcome for root canal treatment.

Str0m and others (2018) categorised endodontic treatment success or ‘no evidence of failure’ as a resolution or lack of progression of periapical pathology or external inflammatory root resorption. In their follow-up of 37 canine teeth in cats treated over an 18-year period, treatment success was seen in 49 per cent (18 teeth); no evidence of failure in 32 per cent (12 teeth); and failure in 19 per cent (seven teeth). This is clearly a very small sample size despite a long study period which is likely to affect the statistical power of the results.

Apical anatomy in cats is very similar to that of dogs. Both species have an apical delta, in the region of 100 small canals that connect the root canal to the apical periodontal ligament (Hernández and others 2014); in contrast human teeth have a large apical foramen. In root canal treatment in people, patency is a procedure whereby an endodontic file is passed through the apical foramen to debride tissue. This is not possible in cats and so there is the potential for residual soft tissue and bacteria to be present in the apical, which could lead to failure of root canal treatment.

ComplicationsComplications of root canal treatment in cats are poorly documented, but these are likely to include:■■ Concurrent but unrelated tooth resorption subsequent to endodontic treatment (Figs 8, 9);■■ Continued external inflammatory root resorption;■■ Failure of the root canal treatment and the persistence of periapical inflammation;■■ Extrusion of disinfectants from the root apex into the periapical tissues;

■■ Extrusion of materials used for obturation from the root canal and into the periapical tissues;■■ Instrument failure within the root canal.

The incidence of these complications still needs to be fully evaluated in cats following root canal treatment.

Fig 7: Root canal treatment of a less mature canine tooth than seen in Fig 6. With a wider root canal, mechanical debridement may not be possible

Fig 6: Root canal treatment of a mature canine tooth where mechanical debridement was possible given the root canal anatomy

Fig 8: (a) Root canal treatment of the right mandibular canine tooth to treat a complicated crown fracture. (b) the same tooth a few years later showing extensive type 2 tooth resorption. The left mandibular canine tooth is also affected by type 2 tooth resorption

(a) (b)

(a) (b) (c)

Fig 9: Paired images from the same cat with four year-intervals between left- and right-hand images. Left-hand images show root canal treatment of the maxillary canine teeth (a, b) with clinically normal mandibular canine teeth (c). Right-hand images show tooth resorption in the treated maxillary canine teeth (a, b) and also resorption affecting the mandibular canine teeth (c)

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SummaryCanine teeth in cats are frequently affected by dental trauma, which results in pulp exposure. Such trauma can be treated with either extraction or root canal treatment. While extraction should result in elimination of endodontic and periapical disease, there are significant complications associated with this procedure. Root canal treatment is an alternative to extraction of canine teeth in cats where pulp exposure is present, but further research needs to be completed to understand the incidence of complications that can result from this treatment.

ReferencesANDREASEN, J. O. & ANDREASEN, F. M. (1990) Essentials of Traumatic Injuries to the Teeth. MunksguaardBLANCO, J., MARAQUE, S., LINARES, A. & MUNOZ, F. (2011) Vertical and horizontal ridge alterations after tooth extraction in the dog: flap versus flapless surgery. Clinical Oral Implants Research 22, 1255-1258DUKE, F. D., SNYDER, C. J., BENTLEY, E. & DUBIELZIG, R. R. (2014) Ocular trauma originating from within the oral cavity; clinical relevance and histologic findings in 10 cases (2003-2013). Journal of Veterinary Dentistry 31, 245-248GORREL, E. C. (2015) Tooth resorption in cats: pathophysiology and treatment options. Journal of Feline Medicine and Surgery 17, 37-43HERNÁNDEZ, S. Z., NEGRO, V. B., DE PUCH, G. & TORIGGIA, P. G. (2014) Scanning electron microscopic evaluation of tooth root apicies in the dog. Journal of Veterinary Dentistry 31, 148-152MENZIES, R. A., REITER, A. M. & LEWIS, J. R. (2014) Assessment of apical periodontitis in dogs and humans: a review. Journal of Veterinary Dentistry 31, 8-21OXFORD, M. (2014) Tooth trauma: pathology and the treatment options. In Practice 36, 2-14OXFORD, M. (2018) Dental extraction techniques in dogs and cats. Companion Animal 23 doi: 10.12968/coan.2018.23.6.336REITER, A. M. (2011) Dental and oral diseases. In The Cat: Clinical Medicine and Management. 1st edn. Ed S. E. Little. Saunders. p 329-370ROBINSON, G. W. (1976) The high rise trauma syndrome in cats. Feline Practice 6, 40-43STRØM, P. C., ARZI, B., LOMMER, M. J., KUNTSI, H., FULTON SCANLAN, A. J., KASS, P. H. & VERSTRAETE, F. J. M. (2018) Radiographic outcome of root canal treatment of canine teeth in cats: 32 cases (1998-2016). Journal of the American Veterinary Medical Association 252, 572-580SOUKUP, J. W., HETZEL, S. & PAUL, A. (2015) Classification and epidemiology of traumatic dentoalveolar injuries in dogs and cats: 959 injuries in 660 patient visits (2004-2012). Journal of Veterinary Dentistry 32, 6-14

Further readingHENNET, P. R. & HARVEY, C. E. (1996) Apical root canal anatomy of canine teeth in cats. American Journal of Veterinary Research 57, 1545-1548KUNTSI-VAATOVAARA, H., VERSTRAETE, F. J. M. & KASS, P. H. (2002) Results of root canal treatment in dogs: 127 cases (1995-2000). Journal of the American Veterinary Medical Association 220, 775-780SOUKUP, J. W., MULHERIN, B. L. & SNYDER, C. J. (2013) Prevalence and nature of dentoalveolar injuries among patients with maxillofacial fractures. Journal of Small Animal Practice 54, 9-14

SELF-ASSESSMENT: TREATING TRAUMATIC INJURIES OF CANINE TEETH IN CATSIn Practice partners with BMJ OnExamination to host self-assessment quizzes for each clinical article. These can be completed online at inpractice.bmj.com

1. Which of these statements regarding fractured teeth are correct?a) Fractured teeth are initially painful because of pulp exposure and pulpitisb) Fractured teeth can be painful because of periapical pathologyc) Fractured teeth can result in inflammatory root resorptiond) Fractured teeth are only considered painful if the animal stops eatinge) Fractured teeth are not a painful condition

2. Which of these statements about the treatment of fractured teeth are correct?a) Fractured teeth are not painful and so do not require treatmentb) Fractured teeth need to be treated and this can be with extractionc) Fractured teeth in cats can be resolved by prosthetic crown placementd) Fractured teeth need to be treated and this can be with root canal treatmente) Fractured teeth should be monitored before deciding if they need to be

treated

3. Complications of extracting canine teeth in cats include:a) Perforation of the eyeb) Fracture of the jawc) Wound dehiscenced) Upper lip entrapmente) All of the above

Answers: (1) a, b,c (2) b, d (3) e

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