Curious facts about teeth

Teeth are bony structures in the mouth, set in two rows – the upper and the lower dental arch. The number and position of the teeth on the left side of each arch match those on the right.

The four main types of teeth

• Incisors – bite into the food and cut or tear off a mouthful.
• Canines – sink into the food and hold it until it is torn off. They are most developed in predators; in herbivores they are missing or come through only in the males.
• Premolars and molars – crush the food.
• Wisdom teeth – the name for the last four molars in humans, because they come through when physical development is complete.

During embryonic development and after birth, mammals grow their milk (temporary) teeth. Between puberty and the end of physical development these fall out and are replaced by permanent ones. Humans have 20 temporary and 32 permanent teeth.

How many teeth some animals have

Animal	Milk teeth	Permanent
Horse	24	42
Cattle	20	32
Sheep	20	32
Pig	32	44
Dog	28	42
Cat	26	30

The structure of a tooth

A tooth has three distinct parts: the crown – above the gum, the neck – covered by the gum, and the roots – one or more, each in its own socket in the jawbone. It is made of enamel, dentine, dental pulp and cementum.

When teeth come through

The milk teeth start to form in the 7th week of embryonic development (the incisors), and the last to form – in the 10th week – are the molars. The first to come through are the lower incisors, between the 6th and 10th month, and the last are the molars, between the 25th and 33rd month.

The buds of the permanent teeth form between the fourth and ninth month of embryonic development, and those of the wisdom teeth most often at around 16–18 years of age; wisdom teeth may never come through at all. The permanent teeth start to come through at around 6–7 years of age, and the process ends at about 13. The last to come through are the wisdom teeth – between 16 and 21 years of age.

“I didn’t know that!”

• Everyone’s teeth are as unique as their fingerprints – even in identical twins.
• Some kinds of cheese protect the teeth from decay.
• In Mexico the Tooth Fairy is the Tooth Mouse – it takes the little teeth and leaves treasures in return.
• Left-handed people usually chew on the left side, right-handed people on the right.
• Many of the teeth lost by people under 35 are lost through sport, accidents or fights.
• George Washington’s false teeth were made from walrus, hippopotamus and cow teeth and from ivory.
• The most expensive tooth belonged to Isaac Newton – a nobleman bought it for $4,560 and had it set in a ring.
• In 200 BC the Romans cleaned their teeth with a mixture of bones, eggshells, honey and oyster shells.
• Queen Elizabeth I’s teeth were visibly discoloured. The German traveller Paul Henter suggested that the cause was eating too much sugar – the first time sugar was linked to tooth decay.
• The second most common disease in the USA is tooth decay; in first place is the common cold.

From history

• The first known dentist is Hesy-Re – he lived in Egypt more than 5,000 years ago.
• Mummies with fillings of rosin and malachite have been found in Egypt; loose teeth were bound with gold wire.
• The ancient Greeks used pumice, talc, alabaster, coral powder or rust as toothpaste.
• The first toothbrushes were twigs: the pointed end was chewed until it frayed and was then used as a brush.
• In the Middle Ages, and later too, the work of dentists was often done by… blacksmiths.
• In 1886 Lucy Beaman Hobbs became the first woman licensed as a dentist.
• In 1905 the assistant Irene Newman was trained to clean teeth – the first dental hygienist.
• In 1950 the Tooth Fairy “left” 25 cents on average, and in 1988 one dollar.

How to look after your teeth: oral hygiene tips and prevention.