Human adult teeth do not continuously grow throughout a person’s life. Once a permanent tooth fully emerges, its growth in size ceases. While human teeth do not enlarge over time, they undergo a distinct developmental process and experience various changes throughout life.
How Human Teeth Develop
Human tooth development begins even before birth. Primary, or baby, teeth start forming between the sixth and eighth week of prenatal development, with permanent teeth beginning their formation around the twentieth week. This process, known as odontogenesis, involves the interaction of embryonic cells that give rise to the tooth’s various structures.
The development proceeds through several stages, including the bud, cap, and bell stages. During these phases, specialized cells differentiate to form the hard tissues of the tooth: enamel, dentin, and pulp. Enamel, the outermost layer, is the hardest substance in the human body, while dentin forms the bulk of the tooth, and the pulp contains nerves and blood vessels. Teeth then emerge into the mouth through a process called eruption, with primary teeth appearing between 6 months and 2 years of age, and permanent teeth replacing them from around age 6 through the early twenties.
Why Human Teeth Stop Growing
Human teeth stop growing once they are fully formed and have erupted into the oral cavity. The root of a tooth completes its formation after the crown has emerged, at which point the tooth’s overall size is fixed. This cessation of growth is due to the nature of human tooth structure and the limited presence of formative tissue in adulthood.
Unlike humans, some animals, such as rodents and sharks, possess teeth that continuously grow throughout their lives. This continuous growth is supported by persistent stem cells within their jaws, which allow for constant replacement or elongation. In humans, these stem cells are active during tooth development and eruption but become inactive or disappear once adult teeth are in place, meaning new teeth cannot be regrown if lost.
What Happens to Teeth Over Time
Although human teeth do not grow, they undergo several changes over a lifetime that can alter their appearance. Natural wear and tear, including attrition from tooth-to-tooth contact and abrasion from external factors like brushing, gradually reduce the tooth’s structure. This wear can make teeth appear shorter or change their biting surfaces.
Another common change is gum recession, where the gum tissue pulls back from the teeth. This recession exposes more of the tooth’s root surface, which is typically covered by gums, making the teeth appear longer than they actually are. Teeth can also experience slight shifting or movement due to changes in the jawbone, loss of adjacent teeth, or habits like teeth grinding. Staining from food, drinks, and tobacco can also alter the color of teeth. These alterations are not forms of growth but rather modifications to the existing tooth structure or its surrounding tissues.