Have you ever wondered how and when your teeth formed? Odontogenesis is the medical term used to describe the formation and eruption of teeth — a process that begins even before birth, as an article in the book Reference Module in Biomedical Sciences outlines.
This process occurs in several stages to form the different parts of a tooth. We have two sets of teeth: deciduous teeth, which are sometimes referred to as primary or baby teeth, and permanent teeth, often known as secondary or adult teeth. Both sets undergo the same developmental process to form, although permanent teeth are formed later than deciduous teeth, since they eventually replace them. Here are the different stages of odontogenesis.
This first stage happens at the eighth week in utero. At this time, cells known as dental epithelium bud from a thick band of cells called the dental lamina, which forms inside the upper and lower jaws. These cells will eventually evolve to form the tooth germ, which is made up of all the soft tissues necessary to grow a tooth.
During this stage, cells begin to shape the outside layer of the tooth, forming a cap that sits on the rest of the tooth bud. This cap is called the enamel organ because it will later form the cells that produce enamel. The rest of the tooth bud, known as the dental papilla, will make the two interior layers of the tooth: the dentin and the pulp.
Another sac of cells, called the dental follicle, surrounds both the enamel organ and the dental papilla. This sac contains blood vessels and nerves. By the cap stage, three different structures make up the tooth germ: the enamel organ, the dental papilla and the dental follicle.
At this point, the enamel organ grows into a bell shape, and two events take place. First, cells of the enamel organ differentiate, meaning they change functions. Depending on their new function, they will fall into one of four cell groups:
- Inner enamel epithelium
- Outer enamel epithelium
- Stratum intermedium
- Stellate reticulum
Together, these cell groups work to develop the enamel layer of the tooth. During the second event in this stage, the enamel epithelium folds into the future shape of the tooth crown, and the dental lamina starts to break down.
The outer two layers of your teeth, enamel and dentin, form during the crown stage. Ameloblast cells are responsible for creating enamel, while odontoblast cells create dentin. These cells come from the enamel epithelium and the dental papilla.
The tooth root, made of root dentin and root canals (where dental pulp lives), forms from a combination of three structures: the dental papilla, the dental follicle and another important group of cells known as Hertwig's epithelial root sheath.
Once the crown of the tooth has formed and the root has begun to develop, the tooth moves vertically toward the oral cavity so it can erupt into the correct position. Some of the jawbone above the tooth will resorb and other connective tissues will break down to help the tooth move. Depending on the type and position of the tooth, each will erupt at different ages. Primary teeth will erupt first, starting around 6 months of age, according to the American Dental Association.
The permanent teeth will develop in the same manner as the primary teeth, beginning at 20 weeks in utero and continuing 10 months after birth. The third molars, or wisdom teeth, are not completely formed until an individual is approximately 5 years old, explains the Reference Module in Biomedical Sciences article.
Odontogenesis is a complex process that can occasionally go off track. If teeth do not develop properly, individuals might experience one or more of these dental issues:
- Missing teeth, also known as hypodontia
- Excess teeth, which are called supernumerary teeth or hyperdontia
- Misshaped teeth
Odontogenesis is an amazing process that gives you the tools you need to eat, speak and smile. But if you or a loved one experience one of these very rare developmental anomalies, talk to your dentist. They will advise you on your treatment options and help you achieve a healthy smile.