PATIENT DETAILS

A 7-year-old, male, domestic short-haired cat.

CASE HISTORY

The upper canines had been extracted a few months earlier. Following the extractions of the upper canine teeth, the lower canines were impinging on the upper lip (in fact, the upper lip was trapped between the maxillary alveolar ridge and the lower canines bilaterally), causing ulcerated indentations. The lip lesions were causing discomfort as evidenced by reduced appetite and pawing at the mouth to free the trapped lip tissue. The case was referred to us for management of the lip ulcerations. The reason for extracting the upper canine teeth was not mentioned in the clinical records.

ORAL EXAMINATION – CONSCIOUS

The owner reported that the lip lesions had developed within a few weeks of extracting the upper canine teeth. They were not sure why the teeth had been extracted, but thought they could have been ‘broken’.

The cat allowed conscious examination of the head and mouth, which identified the following:

The cat was obviously uncomfortable, and pawed at its face and freed the trapped lip tissue several times during the examination.

ORAL EXAMINATION – UNDER GENERAL ANAESTHETIC

A thorough oral examination, including investigating periodontal parameters, was performed and all findings were noted on the dental record.

In summary, examination under general anaesthesia identified the following:

FURTHER INVESTIGATIONS

A series of full-mouth radiographs (10 films) was taken.

RADIOGRAPHIC FINDINGS

Figure 18.1 Radiograph (a) and lateral photograph (b) of the left lower premolars and molar.

(a) Note the extensive resorption of both roots of 307, with the process extending into the crown dentine. The periodontal ligament space is not apparent, and it is difficult to differentiate between tooth substance and bone.

(b) Clinically, the left premolars and molar appear healthy. The gingivae are clinically healthy and there is no evidence of disease of dental hard tissue. The resorptive process affecting the roots and crown of 307 would not have been detected without radiography.

THEORY REFRESHER

Resorption of teeth is common in domestic cats. Tooth resorption has also been shown to occur in feral and wild cats.

Odontoclastic resorptive lesions (ORLs) are a type of ‘idiopathic’ external root resorption, where the hard tissues of the root surfaces are destroyed by the activity of multinucleated cells called odontoclasts. The destroyed root surface is replaced by cementum- or bone-like tissue. The process starts in the cementum and progresses to involve the dentine, where it spreads along the dentine tubules and eventually comes to involve the dentine of the crown as well as the root. The peri-pulpal dentine is relatively resistant to resorption and the pulp therefore only becomes involved late in the disease. The process extends through the crown dentine, eventually reaching the enamel. The enamel is either resorbed or it fractures off and a cavity becomes clinically evident. In the absence of routine radiography, the lesions are first noted clinically when they become evident in the crown, often as cavities at the cemento-enamel junction (CEJ). The first clinical manifestation of ORLs is thus a late-stage lesion. In many cases, the progressive dentine destruction with ORLs weakens and undermines the crown to such an extent that minor trauma, e.g. during chewing, causes the crown to fracture off, leaving the root in the alveolar bone. The resorbing root remnants are usually covered by intact gingiva. However, in some cases the overlying gingiva may be inflamed.

Visual inspection and tactile examination with a dental explorer will only identify end-stage lesions, i.e. when the process involves the crown and has resulted in an obvious cavity. Radiography will identify lesions that are localized to the root surfaces within the alveolar bone (as in this case), which would not be detected by clinical methods. Moreover, it is only with the aid of radiography that the extent of a resorptive process can be identified. Selection of the best treatment option thus depends on radiography. In fact, a series of full-mouth radiographs (the technique is covered in Chapter 4) is recommended for all cats presented for dental therapy. If taking a series of full-mouth radiographs is not possible, e.g. financial restrictions, then take one view of each mandibular premolar/molar region. The mandibular third premolars are the most commonly affected teeth and it has been shown that, in nine out of 10 cats with resorptive lesions, the process will be identified on these two views. If radiographs show resorption of these teeth, then a full-mouth series must be taken.

It remains a matter of debate as to whether odontoclastic resorptive lesions (ORLs) cause discomfort or pain to the affected individual. Based on the fact that pulpal inflammation occurs late in the disease process, it seems likely that lesions that are limited to the root surfaces and do not communicate with the oral environment are asymptomatic. However, once dentine destruction has progressed to such an extent that the process invades the pulp and/or a communication with the oral cavity has been established (when the enamel has been resorbed or it has fractured off to reveal the dentine to the oral cavity), then discomfort and/or pain are likely. Some cats may show clinical signs indicating oral discomfort or pain, e.g. changes in food preferences (soft rather than hard diet) and reduced food intake, but many cats do not.

CLINICAL TIPS

• Resorption of teeth is common in domestic cats.

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