Tooth Anatomy: Structure, Function, and Conditions [with Pictures]

With your teeth, you can cut, crush, and grind food to prepare it for swallowing and digestion. Also, your teeth play an important role in talk and make you look good. There are two sets of teeth. The first set is known as baby, milk, primary, or deciduous teeth. The primary teeth start to erupt at about 6 months of age. These teeth are later replaced by the permanent teeth (the 2nd set). Also, there are four types of teeth: incisors, canines, premolars, and molars. Each type has a specific function. Usually, teeth can withstand high chewing force. However, bacterial acids can damage the teeth, causing dental caries and abscess. To understand how caries and other dental problems occur, you should know the tooth anatomy. In this article we will discuss:

  • What are the types of teeth and their functions?
  • Tooth anatomy: the structure of a tooth and surrounding tissues.
  • When the primary and permanent teeth erupt?

Types of Teeth and Their Functions

The main task of teeth is to cut, crush, and grind food, making swallowing and digestion easier. Also, they help us smile and talk. Every tooth in the oral cavity has a specific function:

  • Incisors: they are in the front area of the upper and lower jaw (4 in each arch). Incisors are sharp and allow food biting and cutting.
  • Canines: they are located directly after the incisors. Canines are conical-shaped. They hold food during biting to facilitate the cutting of food.
  • Premolars and molars: they are located behind canines. They have a wide and flat surface (occlusal surface) with several cusps. They crush food between the occlusal surfaces of upper and lower premolars and molars to make food swallowing and digestion easier.
Types of Teeth and Their Functions
Types of teeth and their functions: Incisors cut food. Canines allow you to tear and grasp food. Premolars and molars crush and grind food to make swallowing and digestion easier.

Tooth Anatomy

The teeth are different in shape. However, they have the same tooth anatomy.

Tooth Anatomy: Parts of a Tooth

Each tooth consists of 3 anatomical parts: the crown, neck, and root.

  • The crown: it is the visible portion of the tooth that protrudes from the gum. The crown is covered by enamel, the hardest substance in the human body.
  • The neck: it is the area where the crown joins the root. The neck is surrounded by gingiva (gum).
  • The root: it is the lower two-thirds of the tooth. It is surrounded by the jaw bone. Incisors and canines have one root. Molars are multi-rooted (2-3 roots). The number of roots is different from a person to another.

Tooth Anatomy: Tooth Layers

The tooth is made of several layers of varying density and hardness: the enamel, dentin, cementum, and pulp.

The Enamel

The enamel is the outer layer of teeth that covers the crown. Also, it protects the tooth against external damaging forces. Tooth enamel is the most resistant and hardest tissue in the human body. It consists of 95% inorganic substance (mainly calcium and phosphate in the form of hydroxyapatite), 1% organic substance, and 4% water. The fluoride increases the hardness of tooth enamel by converting the hydroxyapatite crystals to fluorapatite. So, fluoride toothpaste can increase the strength of enamel. In contrast, acid can damage the enamel by detaching calcium and phosphate, causing dental caries. The tooth enamel is exposed to 2 processes:

  • Demineralization: when oral bacteria decompose carbohydrates in food debris and produce acid, the oral pH drops below 5.5. The bacterial acid dissolves the enamel surface, which leads to the loss of calcium and phosphate ions, causing early stage of dental caries. This is known as “demineralization”. (pH is a measure of the acidic or basic character of an aqueous solution. Solutions with a pH less than 7 are acidic and solutions with a pH greater than 7 are basic).
  • Remineralization: when the oral pH rises, the enamel restores minerals (calcium and phosphate) from saliva, reversing the early stage of dental caries.

Dentin

The dentin is the second layer of the tooth, after the enamel. It is the largest part of tooth structure, surrounding the pulp. It contains fine tubes called “dentinal tubules” which contain nerve tissues. The nerve tissues provide stimuli to the pulp. The dentin is sensitive to heat, cold, and touch, which appears as pain sensation. The dentin is softer and more susceptible to dental caries than the enamel. This is due to the slightly different composition of dentin.

Cementum

The cementum is a calcified substance that covers the root. It attaches the tooth to the alveolar bone. Cementum is softer than the dentin and enamel.

Dental Pulp

Inside the tooth, there is a chamber known as the pulp chamber. It contains nerve tissues and blood vessels that nourish the tooth. These nerve tissues and blood vessels are extending from the jaw bone to the pulp through a small hole at the root tip.

Tooth Anatomy
Tooth Anatomy: Every tooth consists of three parts: the crown, neck, and root. Also, every tooth made of several layers: the enamel, dentin, cementum, and pulp.

The Periodontium: Tissues that Surround and Support Teeth

The periodontium anchors teeth to surrounding tissues and supports teeth during its function. The periodontium consists of:

  • Gingiva: it is a part of the oral mucosa that surrounds teeth and covers the maxilla and mandible. The beautiful smile comes from a harmonious coexistence of teeth and gingiva. Healthy strong gingiva is pink in color, has a harmonious wave profile, and doesn’t bleed. Inflamed gingiva is red, soft, and bleeding frequently during tooth brushing.
  • Cementum: it is a thin layer that covers the roots of the tooth. Also, it attaches the tooth to the bone.
  • Periodontal ligament (PDL): it is also known as periodontal fibers. It is connective tissue fibers in the small gap between the cementum and the jaw bone. The periodontal ligament provides an attachment of the tooth to the jaw bone. Also, it has a supporting, nutritive, sensory, and remodeling function.
  • Alveolar Bone: the alveolar bone supports teeth and is covered by the gingiva. It’s well supported with blood and subjected to continuous modification. The pressure during mastication is transmitted to the bone and stimulates its modification which makes the bone stronger. When there is no pressure on the bone because of tooth loss, the bone recedes. Bone loss may make it difficult to anchor a dental implant or hold a denture.
The Periodontium (Tooth Anatomy)
The periodontium anchors teeth to surrounding tissues and supports teeth during its function. Image source: Wikipedia

Tooth Eruption

The child has 20 primary teeth. In each jaw, there are 4 incisors, 2 canines, and 4 molars. These teeth are gradually replaced by permanent teeth between the ages of 6 and 12 years old (mixed dentition). Normally, the adult has 32 permanent teeth. In each jaw, there are 4 incisors, 2 canines, 4 premolars, and 4 molars.

The Eruption of Primary Teeth

Upper Primary Teeth

  • Central incisor: 6-7 months
  • Lateral incisor: 7-8 months
  • Canine: 18-20 months
  • First Molar:12-15 months
  • Second Molar: 24-36 months

Lower Primary Teeth

  • Central incisor: 6-7 months
  • Lateral incisor: 7-8 months
  • Canine:18-20 months
  • First Molar: 12-15 months
  • Second Molar: 24-36 months
Primary Teeth Eruption Chart
Primary Teeth Eruption Chart: The child has 20 primary teeth. In each jaw, there are 4 incisors, 2 canines, and 4 molars.

The Eruption of Permanent Teeth

Upper Permanent Teeth

  • Central incisor: 7-8 years
  • Lateral incisor: 8-9 years
  • Canine: 11-12 years
  • First premolar:10-11 years
  • Second premolar: 10-12 years
  • First molar: 6-7 years
  • Second molar: 12-13 years
  • Third molar (wisdom tooth): 17-21 years

Lower Permanent Teeth

  • Central incisor: 6-7 years
  • Lateral incisor: 7-8 years
  • Canine: 9-10 years
  • First premolar: 10-12 years
  • Second premolar: 11-12 years
  • First molar: 5-6 years
  • Second molar: 12-13 years
  • Third molar (wisdom tooth): 17-21 years
Permanent Teeth Eruption Chart
Permanent Teeth Eruption Chart: the adult has 32 permanent teeth. In each jaw, there are 4 incisors, 2 canines, 4 premolars, and 4 molars.

Conditions

To understand how dental problems occur, you should know the tooth anatomy. Common dental conditions include:

  • Dental caries: bacteria in the oral cavity decompose food debris and produce acids. These acids dissolve the enamel, causing the formation of dental caries. Untreated caries may extend to the dentin and pulp, causing pain and sensitivity to hot and cold. The treatment of caries includes the removal of dental caries and placement of a tooth filling to restore the shape and function.
  • Tooth abscess: when bacteria enter the pulp, it may lead to the formation of tooth abscess at the root tip. Your dentist may perform a root canal treatment to eliminate the infection or extract the tooth if it is severely damaged. A tooth abscess may also occur as a result of gum disease.
  • Gum disease: it is an inflammation of the gums caused by bacteria in the dental plaque. Symptoms of gum disease include bleeding gums, gum recession, and bad breath. If gum disease is left untreated, it may lead to the destruction of the periodontal ligament, alveolar bone loss, and eventually tooth loss. The treatment of gum disease includes scaling and root planing.
  • Teeth grinding: it involves grinding or clenching your teeth. Over time, teeth grinding can wear down the enamel, leading to toothache, tooth sensitivity, and tooth loss.

Conclusion

Teeth play an important role in digestion. Incisors help you cut the food. Canines allow you to grasp and tear food. Premolars and molars grind food to make swallowing and digestion easier. Also, our teeth help us talk and make us look good. Teeth are different in shape. However, they have the same tooth anatomy. Every tooth consists of three parts: the crown, neck, and root. Also, every tooth made of several layers: the enamel, dentin, cementum, and pulp. Knowing the tooth anatomy will help you understand how dental problems occur and how the treatment is performed.