What is our tooth made of?
The tooth is an amazing sensory organ. The outside of the tooth, is the enamel and is the hardest tissue in the human body. The enamel surrounds another layer of the tooth called the dentin. The pulp contains blood vessels, nerve fibres and other connective tissue. The entire tooth lies suspended in the bone by the periodontal ligament.
The nerve supply to the pulp and the periodontal ligament gives the tooth its “life“. The sensation of hot , cold and the ability to sense on biting into hard objects is because of the nerve supply to the tooth. Each tooth in the mouth gets its nerve supply from the nerve endings of the main nerve. Further, the teeth in the upper jaw and that in the lower jaw are supplied by different branches of the main nerve. The teeth in the upper jaw or the maxilla is supplied by the maxillary nerve ( a branch of the fifth cranial nerve-the trigeminal nerve ). The teeth in the lower jaw or the mandible is supplied by the mandibular nerve ( a branch of the fifth cranial nerve-the trigeminal nerve ).
Any infection in the tooth like an untreated decay or an untreated gum disease triggers a signal to the brain. This in turn causes the sensation of pain. If the tooth is not treated at this point, destruction of the soft tissues further leads to the infection spreading to the bone. The damage at this stage may be irreversible leading to the loss of the tooth
How many teeth sets do we have?
We humans, like other mammals, are diphyodont, meaning that they develop two sets of teeth. The first set (called the “baby”, “milk”, “primary”, or “deciduous” set) normally starts to appear at about six months of age, although some babies are born with one or more visible teeth, known as natal teeth.
The next set of teeth we get is called the permanent or the Adult teeth. These teeth begin to come into the mouth by 6 years of age. And continue to come in till the 18 year.
Deciduous teeth
Deciduous teeth, commonly known as Primary teeth, milk teeth, baby teeth and temporary teeth, are the first set of teeth in the growth development of humans and other diphyodont mammals. Baby teeth are like miniature adult teeth. They develop during the embryonic stage of development and erupt—that is, they become visible in the mouth during infancy. They are usually lost and replaced by permanent teeth, but in the absence of permanent replacements, they can remain functional for many years.
Primary teeth start to form during the sixth week of the embryo phase of human life.
In the primary dentition there are a total of twenty teeth: five per quadrant and ten per arch. The eruption of these teeth (“teething”) begins at the age of six months and continues until twenty-five to thirty-three months of age during the primary dentition period.
Teething age of primary teeth:
- Central incisors : 6–12 months
- Lateral incisors: 9–16 months
- First molars : 13–19 months
- Canine teeth : 16–23 months
- Second molars : 22–33 months
Milk teeth help
- In the development of the mouth.
- Maintain the arch length within the jaw.
- Provide guides for the eruption pathway of the permanent teeth.
- To maintain proper spacing for permanent teeth.
- The roots of primary teeth provide an opening for the permanent teeth to erupt. The primary teeth are important for the development of the child’s speech, for the child’s smile and play a role in chewing of food.
Permanent teeth
Permanent teeth are also called the ‘Adult teeth’. Adult teeth help in chewing, speech, maintaining your facial contours and patent airway. You can have a total of 28-32 permanent teeth. The adult teeth are very much similar in structure to their baby teeth counterparts. Your tooth is made up these parts
Enamel
Tooth enamel is the white portion of the tooth seen in your mouth. The enamel is the hardest substance in your body. It covers the “crown” of the tooth. Enamel acts as an insulator of your teeth. Hence, it protects the inner dentin from the external stimulus. The insulating properties of the enamel is due to it’s high mineral content. At 99% mineralization, enamel is considered a unique mineralised structure in your body. The highly crystallised structure of enamel makes it a strong structure. It is also this property of enamel that makes tooth whitening procedures possible.
When the calcium in enamel is replaced by fluoride, the surface of enamel becomes stronger. The new crystalline structure is then more resistant to decay. The acids of the bacteria cannot attack the tooth as easily. Therefore, brushing your teeth with a fluoridated paste or drinking water with optimised fluoride content or taking your child to your dentist for topical fluoride application plays a significant role on preventing tooth decay.
Wearing out of enamel causes tooth sensitivity. Faulty toothbrushing, consumption of highly acidic food, tooth decay are some of the reasons for loss of enamel.
Dentin
Dentin is the yellow inner part of the tooth and makes up the bulk of the tooth. This layer is less mineralised than the enamel. That makes dentin much softer than the enamel and more decay prone. Your tooth decay progresses much faster in the dentin. Structurally, also the dentin is very different from your tooth enamel. In that, the dentin has very unique structures called the ‘Dentinal tubules’. These very fine tube like structures run throughout the dentin from the pulp till the enamel. This is the reason you can feel tooth sensitivity.
Unlike your tooth enamel that cannot grow, dentin is deposited most of your life. Dentin also forms to protect the tooth in a tooth decay. These form so dentin is called ‘Secondary’ and ‘Tertiary’ dentin. Generally, your tooth takes 5-6 weeks to deposit a layer of dentin. Your tooth can look yellow because of the colour of dentin.
Dental Pulp
The dental pulp is the innermost part of the tooth. The pulp is a soft tissue with nerves and blood vessels. In a way the pulp is the residual tissue of the tooth bud. All the other parts o the tooth develops from the pulp. Since it contains the nerves, any infection of the tooth is reported to the brain through the pulp. Your tooth is a living structure because of the pulp. When a tooth infection sets in your dentist/ endodontist will do an RCT. Here your dentist will remove the diseased pulp tissue and pack the space with a root filling material.
A newer development with research is to use your pulp tissue to regenerate other tissues like bone. Pulp tissue from the milk tooth or extracted wisdom tooth is used for this. MSCs (Mesenchymal Stem Cells) extracted from Dental Pulp have the ability to differentiate into Bone, Dental Tissue, Cartilage, Muscle, Neural and other cell types.
Periodontal Ligament
Your tooth is held to the surrounding bone by a ligament called the ‘Periodontal Ligament’. This is like a shock absorber of your tooth. All the chewing pressure of the teeth is taken by this ligament.
Why are teeth not considered bones?
Teeth and bones are both hard, white and heavy with calcium, but that doesn’t make them one and the same. From the way they look to how they heal, teeth are quite different from the body’s bones.
Minerals in bone and teeth
Teeth are composed of calcium, phosphorus, and other minerals. Bones contain calcium, phosphorus, sodium and other minerals, but mostly consist of the protein collagen. Collagen is a living, growing tissue that gives bones their a flexible framework that allows them to withstand pressure. Calcium fills in the space around that framework and makes the bone strong enough to support the body’s weight.
But bones are still not as strong as teeth. The hardest part of the human body , teeth mostly consist of a calcified tissue called enamel. The enamel covers the bulk of the tooth which is the dentin. The enamel, is that hard, shiny layer that is visible.
The outer layer of bone and teeth
The exterior of bones consists of periosteum, a dense, smooth, slippery membrane that lines the outer surface of most bones, except at the joints of long bones, which instead consist of slimy hyaline cartilage. Periosteum contains osteoblasts, or cells that can manufacture new bone growth and repair.
Tooth enamel, unfortunately, doesn’t have the same regenerative powers. Unlike bones, teeth cannot heal themselves or grow back together if they are broken. When a bone fractures, new bone cells rush in to fill the gap and repair the break, but a cracked or a broken tooth may require a root canal or even total extraction.
The marrow tissue in bone and teeth
Another difference between teeth and bones is that bone marrow produces red and white blood cells, while teeth do not. Bones receive their blood supply from a number of arteries that pass through the bone’s periosteum to the inner bone marrow.
Although the core of a tooth that’s been knocked out might look like marrow, it’s actually something called the dental pulp, the living portion of each tooth that contains nerves, arteries and veins and runs through to the jaw bone. These nerves are what cause us to feel toothaches caused by cavities or experience pain when eating something hot or cold.
And one last difference is that our teeth are bare and on display, while bones are safety tucked away under our skin.
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