Human teeth are calcified structures which are rooted to the jaws. Gums cover the roots of the teeth. The primary use of teeth is to break down food for easy digestion. In mammals, teeth are some of the longest lasting features where the oldest human tooth is dated some 500,000 years ago.
Types of Teeth
In a lifetime, two types of teeth grow in humans, namely, baby teeth and permanent teeth. An infant develops baby teeth in the age between 6 to 10 months. The earliest ones are the central incisors. Then, new teeth grow on the either sides. By the age of 3 years, most of the baby teeth are already grown. At the age of 6 to 7 years, permanent teeth start to grow.
The size of human teeth is about 10mm and there are 32 teeth in an adult human mouth. There are 4 different types of teeth: incisors, canines, premolars, and molars. There are 8 incisors which are located in the front and they are sharp edged teeth. Incisors grow around the age of 7 to 8 years. Canines are located in the jaw and they are used to tear food. Canines grow around the age of 9 to 10 years. There are two sets of bicuspids which are used for chewing and there are twelve molars. The first set of premolars grows around the age of 10 to 12 years, and the second set of premolars grows around the age of 11 to 12 years. The first set of molars grows in the age between 6 to 7 years, and the second set grows in the age between 11 to 13 years. The wisdom teeth generally grow in the age between 17 to 21 years but in some cases, they never grow.
Dental Anatomy of Humans: A guide to the various types of human teeth.
3D Guide to Dental Anatomy: a 3D guide to the human mouth.
Parts of the Tooth
Tooth enamel is one of the hardest mineralized substances found in the body. It’s composed of minerals and organic material. Enamel varies in thickness and its color is mostly light yellow. It’s the hard layer which is cleaned when a person brushes. It’s more mineralized as compared to dentin which is located close to it. Dentin is a yellow color material found between the pulp chamber and the cementum. It’s composed of connective tissues made from minerals and proteins. Dentin forms the major part of the tooth. Cementum is a bone-like substance which serves as the medium to attach the ligament to the tooth, providing stability. Pulp forms the central part and it’s made up of soft connective tissues.
Anatomy & Development: The Lucile Packard Children’s Hospital offers information on the anatomy and development of teeth and mouth.
Healthy Root Canal: Information on basic tooth and root system structure.
Dental Anatomy: A good look at the anatomy of human teeth.
Supporting Structures
There are mainly three types of supporting structures in human teeth. The periodontal ligament is made up of connective tissues and it covers the root of a tooth inside a bone-like structure. It has a width of between 0.15 to 0.38 mm but its size decreases with age. It supports the tooth and helps in resorption of bone during the movements. The alveolar bone is the structure which forms around the jaw. It’s modified many times in life. If force is applied on it, osteoclasts destroy it whereas osteoblasts create it again. Gingiva refers to the tissues found around the jaws. There are three types of Gingiva, namely, junctional, gingival, and sulcular. Made up of epithelial cells, they are located deep inside so it’s not visible from the outside.
Tooth Decay
There are two major causes for tooth decay: plaque and dental cavities. Plaque is the film which covers the teeth. It contains large quantities of bacteria such as anaerobes and streptococcus. With time, the plaque mineralizes and forms tartar in the mouth. If the plaque is not removed, it may build up to form dental cavities. Plaque is formed from the remains of food items containing starch and sugars. Teeth can be destroyed if the bacteria provide lactic acid and dissolve the enamel of the teeth. Caries or cavities are infectious diseases which can permanently damage the teeth structure. They are caused by acid producing bacteria which damage the teeth structure with the help of certain carbohydrates such as sucrose, glucose, and fructose.
Tooth Disorders: The NIH provides resources on tooth decay, cavities, and other tooth problems.
Dental Caries: The CDC offers vital information on dental caries.
Dental Procedures
Dental procedures may be needed to maintain the health of teeth and gums, and to restore the functioning of teeth. Dental crown refers to the process in which the tooth structure may require a cap-like structure for protection and functioning. Dental crowns are made up of hard materials and they encase the tooth structure. Root canal is done when the cavity in a tooth reaches the innermost layers of the tooth. Root canal is done to prevent the need for expensive procedures such as dental bridges and implants. A dental bridge is required in case a tooth is missing. The missing tooth creates a gap between teeth so there’s an imbalance. The teeth on the side of the gap are “capped” and filling of the gap is done with a false tooth. The false tooth serves as a regular tooth.
Dental Crowns: The British Dental Health Foundation answers frequently asked questions about dental crowns.
Root Canal Treatment: The page explains how a tooth can be saved by using root canal treatment.
Dental Bridges: The University of Maryland provides information on dental bridges.
Additional Resources
American Dental Association: Resources for the public from the ADA.
Oral Health Resources: Information and resources from the Center for Disease Control and Prvention.
NIDCR Oral Health: Information on a variety of topics in oral health.
American Dental Hygienists’ Association: Oral heaalth information from the ADHA.
Academy of General Dentistry: Oral health resources from the AGD.
Resources for Kids
Taking Care of Your Teeth: Try these tips to keep your teeth beautiful and healthy.
Healthy Teeth: Information for elementary aged kids on a variety of oral health topics.
Brush Up on Healthy Teeth: If you want to have a big beautiful smile, follow these steps.
How to Brush: Learn the right way to brush your teeth.
Colgate Kids: Oral health information for both kids and parents.
Teaching Healthy Smiles: Activities for dental health in K-5 classrooms.
Tooth Facts: The ADHA provides a lot of information on teeth.