Human Dentition

Man has two sets of teeth, the deciduous (temporary) teeth, and the succedaneous (permanent) teeth.

The temporary teeth in man are twenty in number: ten in the upper jaw and ten in the lower jaw, placed symmetrically on each side of the mesial line. Those teeth composing the deciduous set are four central incisors, four lateral incisors, four cuspids (canines), four first molar and four second molars.

The eruption of the primary teeth begins at about 6 months of age with the mandibular incisors. All primary teeth have usually erupted by the age of 2 years, although there is considerable individual variation, with some children not exhibiting their first teeth until they are over 1 year old. There do not appear to be any ethnic differences in the dates of eruption, but severe malnutrition may cause delayed eruption as well as seriously affecting other aspects of the child's growth.

The usual order of appearance of the primary teeth in the mouth is central incisors, lateral incisors, first molars, canines, second molars.

Mandibular teeth usually erupt before maxillary teeth. As the child approaches the age of 5 years, spacing will appear between the primary teeth as a result of the jaw growth required to accommodate the developing permanent teeth.

Eruption of the mandibular permanent teeth tends to occur slightly ahead of the maxillary, by a few months. Only the permanent molars erupt without displacing a primary predecessor, and the first permanent molar appears at the age of 6 years.

There are normally thirty-two permanent teeth in the adult. In the permanent denture are four central incisors, four lateral incisors, four cuspids (canines), four first premolars (bicuspids), four second premolars, four first molars, four second molars and four third molars.

The teeth having each one root are the permanent upper centrals, laterals, cuspids and second premolars. The first premolar has two roots; the molar teeth have each three roots. The lower centrals, laterals, cuspids, first and second premolars have each one root. The lower molars usually have two roots. The permanent centrals, laterals and cuspids have each one root. The upper molars have each three roots, while each of the lower molars has but two roots. The central and lateral incisors are used to incise or cut food. The teeth helping to pierce and shear food are the cuspids. The function of the premolars is intermediate between the cuspids and molars. The molars are used to crush or grind food.

The teeth have received their names according to their form or their office, thus, incisors - cutters, cuspidate - pointed, molars - grinders.

to pierce протыкать, прокалывать

to shear резать

intermediate промежуточный

to crush дробить, размельчать

to grind молоть, разжёвывать

to receive получать

office функция, место, предназначение

pointed острый, заострённый

6. Answer the questions:

1. When does the eruption of the primary teeth begin?

2. Which is the usual order of appearance of the primary teeth in the mouth?

3. How many temporary teeth does a child have?

4. How many permanent teeth does an adult have?

5. What teeth compose the deciduous set?

6. What teeth compose the permanent teeth?

7. What teeth have one root?

8. What teeth have two or three roots?

9. What is the function of the teeth?