A unique book written by the dentist to King George III, detailing the art of dentistry, fetched over six times its expected price at auction recently. The book, A treatise on the disorders and deformities of the teeth and gums and the most rational methods of treating them, was written in 1770 and is still bound in its original calfskin.

In it, royal dentist and author Thomas Berdmore reveals painful methods used on patients to cure tooth problems, such as 'breaking the teeth into order by means of a strong pair of crooked pliers', and points out that 'the boyish custom of carrying a table or chair in their mouth is as dangerous as it is absurd'.

Berdmore died in 1785 aged 45 and is buried in Nottingham. The book was auctioned in Derby in 26 November by Hansons Auctioneers and fetched £2,000, £1,700 more than the original guide price.