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What you can’t see won’t hurt!

by
01 June 2014, at 1:00am

Bob Partridge stresses the importance of a thorough clinical examination and discusses how to tackle problems when there is nothing visible – and the need to remember to count the teeth

AS veterinary surgeons we are used to performing a clinical examination and then making decisions as to presumptive diagnoses based on our findings. The list of possible differential diagnoses then dictates the options that we present to clients regarding possible further investigations and ultimately to the treatments that we could provide.

We observe a degree of gingival recessional changes with inflammation around some incisor teeth. We recommend a COHAT procedure – a Complete Oral Health Assessment and Treatment. This examination confirms the loss of periodontal attachment. Increased mobility is noted on examination and ideally radiographs con rm the loss of periodontal bone support. The owner is contacted and a decision is made to extract the tooth.

But what if there is nothing to see? I can almost hear the response, “If there is nothing to see, then there is nothing to worry about.” Usually I’d agree – but sometimes “there is nothing to see” means that there is something absent.

Counting is a much underrated skill in veterinary practice. Many of us will have experienced the double-take when you lift a cat, which was quietly sitting in its basket, out and onto the examination table. Only then do you realise that it is actually an amputee... On a less extreme level, counting is essential to assess normality in veterinary dentistry.

“Extras” are fairly easy to spot – when they are whole teeth. But nature has a habit of playing games with veterinary dentists.

The left upper premolar in appears pretty normal but close examination of the occlusal surface might alert you to a possible problem should the tooth need to be extracted. Only radiographs truly demonstrate the extra root that you would have to contend with. Sometimes, however, the extra roots are completely non-identifiable clinically – but much more obvious radiographically.

So these are cases where there is nothing (or at least very little) to see. Fortunately, nature sometimes smiles on us poor dentists and gives us resounding clues as to hidden problems by producing changes to the shapes of the crowns. This can result from fusion of teeth – or incomplete splitting of teeth during development.

Do these extra roots matter? Well they certainly do if you are trying to extract the tooth. We normally rely on splitting the tooth into its separate rooted components – then extracting each one individually.

If you simply rely on the textbooks to tell you how many roots and where they are, then you will come across problems in 10% or more of cases. 

Should you be extracting the teeth due to infection, then the retained root is likely to act as a continuing repository of bacteria and inflammation. This may cause a continuing discharge from the area and pain – an unhappy pet and a dissatisfied client.

Having considered extra teeth and extra roots, we now have to think about the situation when our counting comes up with less than the expected number of teeth.

This may be due to previous extractions; hopefully these will be meticulously documented so that it is clear from the records that the tooth was completely extracted 18 months ago, in which case things are clear.

Especially common in felines are the “missing teeth” that have not been recorded as being extracted. These are frequently as a result of tooth resorptive (TR) lesions.

Figures 10 and 11 show the left mandible of a cat. The clinical photo shows an obvious TR lesion to the last molar (red arrows) – then extent of the destruction can also be seen on the radiograph.

However, 307 (turquoise arrow) is apparently missing – simply a slight bulge to the gingiva; but the radiograph shows resorbing roots. Technically this is a Stage 5 lesion. Another example (this time a feline canine tooth) is shown in Figure 12.

As the gums are quiescent and there are no radiographic signs of apical infection or endodontic disease, it is safe to simply monitor these teeth as they continue to resorb.

The next case (Figures 13 and 14) is one of true oligodontia – or fewer than normal teeth.

These missing premolars have simply failed to develop. Often the temporary deciduous tooth is in place but the permanent replacement fails to appear. This causes no significant problems; however, it is an hereditary condition and will be picked up by alert judges (especially in the USA). Ideally, affected animals should not be bred from.

In Figure 15 the dog demonstrated a missing canine tooth – this had never been extracted or had erupted. He was also suffering from an enamel hypoplasia, a defect in the development of the enamel. However, the question is: where is the right lower canine?

The combined radiographs make it much easier to appreciate that a distorted canine tooth is actually trapped in the mandible. The incident that caused this may well have been responsible for the damage to the developing incisor enamel as well.

Although these cases are a technical challenge and fun to deal with surgically, sometimes our counting simply reveals teeth that are genuinely missing.

Another interesting group of “missing teeth” patients suffer from dentigerous cysts. These cysts are usually associated with an unerupted, often abnormal, tooth. The pathogenesis is uncertain; trauma may be involved – however, the relatively high prevalence in Boxers and some other brachycephalics could well indicate a genetic link.

They are not uncommon – when you start to look for them. A cystic structure develops from proliferation of remnants of the developmental enamel organ or the reduced tissue epithelium.

Initially (apart from the missing tooth) they are asymptomatic, but as the cyst enlarges it can lead to destruction of the local bone, sometimes displacing adjacent teeth (which may also suffer root resorption).

The cyst can become visible under the gingiva as a fluid-filled structure, which occasionally may rupture and become infected.

The lesions are often bilateral (although sometimes to different degrees of development). 

The cyst expansion can compromise blood supplies to other teeth – resulting in pulpal damage.

The goal of treatment is to remove any severely compromised teeth, or perform suitable endodontic therapy if appropriate. It is also essential, however, to completely remove the epithelial lining of the cyst wall – otherwise recurrence is likely. More severe cases can require more complex surgery and may even result in pathologic fractures of the jaw.

Conclusion

Don’t forget to count the teeth when you are examining your patients.