Better the understanding of the oral cavity and the structures present within it, quicker do we realize our responsibility towards their maintenance.
The 32 teeth lying embedded within the bone in the oral cavity not only help us eat, speak and smile but also contribute to our facial profile.
These structures are inherited and we should know how these structures are named, classified when they develop and what they are made up of so that they can be taken care of in the best possible way.
Table of Contents
Different Names of Teeth and Their Structure
Teeth are of four types
1) Incisors
Incisors are the front teeth. They are chisel-shaped. Incisors are 8 in number. 4 in the upper jaw and 4 in the lower jaw. These teeth help in the biting and incision of food.
2) Canines
Canines are pointed in shape and help tear food. Canine is the longest tooth. These are four in number, 2 in the upper jaw and 2 in the lower jaw. They lie beside the incisor teeth and form the cornerstones of the mouth. They are also known as the cuspids because they have a pointed tip.
3) Premolars
Premolars help in tearing and crushing food. They are 8 in number. 4 in the upper jaw and 4 in the lower jaw (2 in each quadrant). They are present behind the canine. Premolars are also known as the bicuspids since they have two cusps.
4) Molars
Molars are the largest teeth with the greatest biting ability. Molars are 8 to 12 in number. They are present behind the premolars.
Baby Teeth
When babies are born, their teeth are not visible in the mouth. During this time, these teeth lie within the jawbone. At the age of 6 months, the baby teeth start appearing in the child’s mouth. It takes 33 months for all baby teeth to emerge through the gums.
Baby teeth are also known as milk teeth or primary teeth. Baby teeth are less in number. There are a total of 20 baby teeth in children (Premolars are not present in the baby teeth)
The function of baby teeth is to enable the child to speak and to eat. These baby teeth get replaced by permanent teeth from the age of 6 years.
The difference between baby teeth and permanent teeth is in size and shape. Baby teeth are smaller in size. As a child’s age advances, the jaw increases in size. During childhood, the jaws are small. Hence the size of baby teeth is also small so that they can fit in the child’s oral cavity.
The health of baby teeth is vital. Baby teeth act as a guide for the growth of underlying permanent teeth. Baby teeth may get decayed and exfoliate at an early age. A premature exfoliation indicates an early eruption of the permanent tooth. Incorrect time of eruption can lead to crowding in the teeth. Also, the infection of baby teeth can get transmitted to the underlying permanent teeth.
When do babies start teething ?
Teething starts at the age of 6 months and completes at the age of 33 months. The underlying chart gives you an overall idea about when each tooth erupts.
Upper Teeth
Central incisor –> 8 to 12 months
Lateral incisor –> 9 to 13 months
Canine –> 16 to 22 months
First Molar –>13 to 19 months
Second Molar –> 25 to 33 months
Lower Teeth
Central incisor –> 6 to 10 months
Lateral incisor –> 10 to 16 months
Canine –> 17 to 23 months
First Molar –> 14 to 18 months
Second Molar –> 23 to 31 months
The eruption of baby teeth is completed when the baby turns 3 years old.
When do permanent teeth erupt?
Humans have two sets of teeth in their entire lifetime. The 20 baby teeth are replaced with 32 permanent teeth. This replacement starts at the age of 6 years. The underlying chart gives you an idea about when the permanent tooth erupts
Upper Teeth
Central incisor –> 7 to 8 years
Lateral incisor –> 8 to 9 years
Canine –> 11 to 12 years
First premolar –> 10 to 11 years
Second premolar –> 10 to 12 years
First molar –> 6 to 7 years
Second molar –> 12 to 13 years
Third molar –> 17 to 21 years
Lower Teeth
Central incisor –> 6 to 7 years
Lateral incisor –> 7 to 8 years
Canine –> 9 to 10 years
First premolar –> 10 to 12 years
Second Premolar –> 11 to 12 years
First molar –> 6 to 7 years
Second molar –> 11 to 13 years
Third Molar –> 17 to 21 years
Different parts of a tooth
A tooth is externally made up of two parts:
1) Crown
The upper portion of the tooth is the crown. It is the only part of the tooth which is visible in the oral cavity. It is made up of enamel, dentin and pulp. Crowns are of different shapes and sizes. The shape and size are according to the function the tooth serves.
2) Root
The lower portion of the tooth is the root. It is that part of the tooth which is present inside the alveolar bone. It is made up of enamel, dentin, pulp and cementum. The number, shape and size of the dental root are different for each tooth.
- An incisor has one root
- A canine has one root
- A premolar can have 1 or 2 roots
- A molar can have a maximum of three roots
A tooth is internally made up of three parts:
1) Enamel
It is the outermost layer of a tooth. The color ranges from white to light yellow. The enamel is mainly made up of calcium. It is the hardest part of the tooth. It protects the inner layers from trauma or infection. Inability to maintain good oral hygiene can cause a bacterial attack on the enamel. This can lead to the spreading of infection to the underlying layers of a tooth.
2) Dentin
This layer lies within the enamel. It is dark yellow in color. When dentin gets exposed, there is sensitivity experienced. This sensitivity is due to the exposure of nerves traversing the dentinal layer of the tooth. Its function is to protect the underlying pulpal tissue.
3) Pulp
This is the innermost layer of the tooth. It is made up of nerves, vessels and connective tissue. Any infection involving the pulpal tissue requires root canal treatment.
4) Cementum
This layer is present surrounding the tooth root. It helps attach the tooth to the bone and also avoids the tooth from getting resorbed.
Teeth Numbers
The oral cavity is divided into four quadrants (upper right, upper left, lower right and lower left).
Each tooth is given a specific number which makes it easier for the dentist to refer to each tooth.
FDI world dental federation numbering system is one of the preferred methods for numbering teeth which is as follows:
Permanent teeth: There are eight permanent teeth present in each quadrant
First Quadrant
11 – Central incisor
12 – Lateral incisor
13 – Canine
14 – First premolar
15 – Second premolar
16 – First molar
17 – Second molar
18 – Third molar
Second Quadrant
21 – Central incisor
22 – Lateral incisor
23 – Canine
24 – First premolar
25 – Second premolar
26 – First molar
27 – Second molar
28 – Third molar
Third Quadrant
31 – Central incisor
32 – Lateral incisor
33 – Canine
34 – First premolar
35 – Second premolar
36 – First molar
37 – Second molar
38 – Third molar
Fourth Quadrant
41 – Central incisor
42 – Lateral incisor
43 – Canine
44 – First premolar
45 – Second premolar
46 – First molar
47 – Second molar
48 – Third molar
Baby teeth: There are 5 baby teeth present in each quadrant
First Quadrant
51 – Central incisor
52 – Lateral incisor
53 – Canine
54 – First molar
55 – Second molar
Second Quadrant
61 – Central incisor
62 – Lateral incisor
63 – Canine
64 – First molar
65 – Second molar
Third Quadrant
71 – Central incisor
72 – Lateral incisor
73 – Canine
74 – First molar
75 – Second molar
Fourth Quadrant
81 – Central incisor
82 – Lateral incisor
83 – Canine
84 – First molar
85 – Second molar
Summary
The set of teeth in humans comprise of incisors, canines, premolars and molars. Children get all their 20 primary teeth by the age of 3 years. By the age of 21 years, most people will get their wisdom teeth and have all their 32 permanent teeth.
Teeth are vital for chewing and speaking. Maintenance of good oral hygiene is essential to keep the teeth healthy and to function throughout life.
A good and healthy oral hygiene can be maintained by:
- Brushing teeth twice a day, daily.
- Flossing once a day
- Rinsing after every meal
- Avoiding excess sugar in food
- Visiting your dentist every 6 months