Teeth are the bony, hard structures found in the mouths of animals and humans. Their primary function is to chew food but they are also used for other purposes like hunting, fighting, gnawing, digging, etc. In our body, teeth are the hardest and most durable organ. Teeth have to be very strong to tolerate all the chewing and crunching of food materials. Teeth are made of calcium, phosphorus, and other mineral salts which give it its incredible strength. Teeth from humans and other animals that lived thousands of years ago can still be found well preserved in archaeological finds.
We use our teeth in masticating food. Mastication is the process by which we tear, cut, and grind food in preparation for swallowing. Chewing allows enzymes and lubricants released in the mouth to further digest, or break down, food. As we chew, salivary glands in the walls and floor of the mouth secrete saliva, which softens the food and helps break it down even more. Saliva makes it easier to chew and swallow foods, and it contains enzymes that aid in the digestion of carbohydrates.This is the first step in digestion of food. Teeth also play an important role in speech. Teeth also provide structural support to the face and gives appearance.
Most animals use their teeth to chew food. Many animals have evolved teeth to perform specialized tasks. Carnivorous animals like tigers have long, sharp tearing teeth for biting and killing prey. A tiger’s canine tooth is 10 times larger than human tooth. The canine tooth’s job is to stab, wound, and skin the tiger’s prey. The carnassial teeth in the backs of their mouths come together like the blades of scissors. Using its big canine teeth and its broad, powerful jaws, a tiger can kill its prey in one quick bite. On the other hand, herbivorous animals like cows and horses have large flat teeth for grinding grass and other vegetation.
Teeth are important to us in many ways. They help us in eating so that we can stay healthy. They also give us a good voice. Teeth also give a good appearance. They are the secret behind a beautiful smile! It is very important to take care of them. If you take care of them, they will take care of you.
What are the parts of a tooth?
There are four distinct types of tissue that make up our teeth. The four tissues are:
- Enamel
- Dentin
- Pulp
- Cementum
Enamel is the clear outermost layer above the gum line. It is the hardest substance in the human body and it gives protection to the inner layers of the teeth from harmful bacteria and changes in temperature from hot or cold food. In human beings, the thickness of the enamel layer is about 0.16 cm.
Dentin, Pulp and Cementum
Directly beneath the enamel is dentin, a hard, mineral material that is similar to human bone, only stronger. Dentin surrounds and protects the pulp, or core of the tooth. Pulp contains blood vessels, which carry oxygen and nutrients to the tooth, and nerves, which transmit pain and temperature sensations to the brain. The outer layer of the tooth that lies below the gum line is cementum, a bonelike substance that anchors the tooth to the jawbone.
Crown
The visible portion of the tooth is called the crown. Projections on the top of each crown, used primarily for chewing and grinding, are called cusps. The portion of the tooth that lies beneath the gum line is the root. The periodontal ligament anchors the tooth in place with small elastic fibers that connect the cementum in the root to a special socket in the jawbone called the alveolus.
Types of teeth
Adult humans typically have 32 teeth: 16 in the upper jaw and 16 in the lower jaw, that fit together and work in concert to chew food. Teeth on the right side of each jaw are usually identical to the teeth on the left side and matching teeth on opposite sides are referred to as sets, or pairs.
Humans are heterodonts, that is, they have teeth of different sizes and shapes that serve different functions, such as tearing and grinding. In contrast, the homodont teeth found in many animals are all the same size and shape, and perform the same function.
Incisors, Canines, Premolars and Molars
Humans have four types of teeth, each with a specific size, shape, and function. Adult humans have eight incisors, located at the front of the mouth—four in the upper jaw and four in the lower jaw. Incisors have a sharp edge that is used to cut food. On either side of the incisors are the canines. The upper canines are sometimes called eyeteeth. There are two canines in each jaw, and their primary role is to tear food.
Behind the canines are the bicuspids, or premolars, flat teeth with pronounced cusps that grind and mash food. There are two sets, or four bicuspids, in each jaw. Behind the bicuspids are the molars, where the most vigorous chewing occurs. There are twelve molars—three sets in each jaw—referred to as the first, second, and third molars.
Third molars are often called wisdom teeth; they developed thousands of years ago when human diets consisted of mostly raw and unprocessed foods that required the extra chewing and grinding power of a third set of molars. Today wisdom teeth are not needed for chewing and, because they can crowd other teeth, are often removed.
Tooth Development
Humans are diphyodont—that is, they develop two sets of teeth during their lives. The first set of teeth are the deciduous teeth, 20 small teeth also known as baby teeth or milk teeth. Deciduous teeth start developing about two months after conception and typically begin to erupt above the gumline when a baby is six or seven months old.
Occasionally a baby may be born with one or more deciduous teeth at birth, known as natal teeth. By the time a child is six years old, a second set of 32 larger teeth, called permanent teeth, start to erupt, or push out of the gums, eventually replacing the deciduous teeth.
Stages of tooth development
Human tooth development occurs in stages. The hard tissue of the deciduous teeth, or the dentin, forms while the fetus is in the womb. After the child is born, tooth enamel develops in stages. Front tooth enamel, for example, is usually complete around one month after birth, while the enamel on the second molars is not completely developed until a child is about a year and a half old. When the enamel is fully developed the tooth erupts. Front teeth usually erupt when a child is from 6 to 12 months of age, second molars between 13 and 19 months old, and canines usually erupt at 19 months or older. The final stage of tooth development is root completion, a slow process that continues until the child is more than three years old.
Permanent Teeth
Around the age of six, the roots of deciduous teeth slowly dissolve as the developing permanent teeth start to push them out. Deciduous teeth eventually fall out and are replaced by the erupting permanent teeth. This begins a transitional phase of tooth development that takes place over the next 15 years. As baby teeth are pushed out by permanent teeth, the entire mouth and jaw transform from their childhood shape to a more pronounced, adult like structure.
Permanent Incisors, Canines and Molars
From age six to age nine, a child’s permanent incisors, canines, and first molars erupt. The bicuspids erupt from age 10 to age 12, and the second molars come in by age 13. The third molars, or wisdom teeth, usually erupt by the age of 21. When human teeth grow to a certain size, the root essentially closes and the teeth stop growing. Closed-rooted teeth have narrow root openings that are only big enough for the periodontal ligament, blood vessels, and a nerve.
