Seven per cent of pet dogs – mostly small, “toy” breeds – have doubled-up teeth, reminiscent of sharks’ mouths. The condition, known as persistent deciduous teeth, occurs when the dog’s baby teeth remain fixed in the jaw, close to the adult teeth, instead of falling out, creating rows of teeth similar to those seen in sharks.
To investigate these “shark teeth”, at Waltham Petcare Science Institute in Leicestershire, UK, and her colleagues examined the records of 2.8 million purebred dogs in the US from veterinary visits occurring between January 2010 and December 2014. The team divided the 60 analysed breeds into six size categories, from extra-small (less than 6.5 kilograms) to extra-large (greater than 40 kg).
They found that 15 per cent of extra-small dogs had shark teeth, as opposed to less than 1 per cent of all dogs in categories heavier than 15 kilograms. Among these toy breeds, Yorkshire terriers, toy poodles, Malteses and chihuahuas ranked the highest in prevalence.
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Across all breeds, greyhounds had the lowest incidence, at 0.1 per cent, whereas Yorkshire terriers, at 25 per cent, had the highest, the team found.
The fact that smaller breeds are more likely to have shark teeth could simply be down to them having smaller mouths, says at the Royal Veterinary College in London. In 2020, he found that as those with nose lengths closer to the average.
“[Persistent deciduous teeth] is a disorder that’s heavily related to breed, and that’s key, because that means we can change that if we wish,” he says.
Wallis and her colleagues also found a link between obesity and shark teeth, which were 11 per cent more common in overweight dogs. It is less clear why this should be the case, says O’Neill, but Wallis has previously found links between oral health and weight for the same group of dogs, showing that . Plus, some studies in humans have shown that .
Even so, more research in dogs is needed to understand this new finding, says O’Neill. In particular, dogs develop persistent deciduous teeth when they are young puppies, which is generally well before they become overweight.
The findings highlight the importance of seeking regular veterinary care to check dogs’ mouths for persistent deciduous teeth – especially for dogs at higher risk of the condition – and to have them removed as soon as possible to prevent complications, report Wallis and her colleagues.
Research in Veterinary Science
