Teeth often appear longer as a person ages, leading to questions about continued tooth growth. This visual change is not due to the teeth actively lengthening. Instead, the perception of an elongated tooth is a biological illusion created by changes in the surrounding soft tissues of the mouth. This phenomenon is a sign of a shift in the relationship between the tooth surface and the gingival margin.
The Biology of Mature Teeth
Once a permanent tooth erupts and root formation is complete, typically by the late teenage years, the hard structure of the tooth cannot grow further. The crown’s outer covering is enamel, the hardest substance in the human body, which is completely mineralized and lacks living cells for structural elongation. The tooth is divided into the crown, the visible portion covered in enamel, and the root, which is embedded in the jawbone and covered in cementum.
The tooth’s maximum length is fixed upon completion of root development. Over decades of use, the crown often experiences slight shortening due to normal wear and tear, a process known as attrition. This wear occurs as enamel surfaces grind against opposing teeth during chewing. The fact that teeth appear longer later in life, despite this mechanical shortening, confirms that the visual change is caused by something external to the crown itself.
Gum Recession and Apparent Tooth Length
The illusion of a longer tooth is primarily created by gingival recession, where the margin of the gum tissue shifts away from the crown. This displacement is an apical movement, meaning the gum line moves toward the tooth root. As the gum tissue retreats, it uncovers a portion of the tooth that was previously hidden.
The newly exposed surface is the root, which is covered by a thinner, softer layer called cementum. The boundary between the crown’s enamel and the root’s cementum is the cementoenamel junction (CEJ). When the gum margin moves past the CEJ, the tooth appears longer because more structure is visible. Since this exposed root structure lacks protective enamel, it often looks slightly yellower or darker than the crown, enhancing the perception of elongation.
The exposure of the root surface frequently leads to dentinal hypersensitivity, felt as sharp pain when consuming cold or hot foods. This occurs because the underlying dentin contains microscopic tubules that lead directly to the tooth’s nerve. The loss of the gum and cementum shield leaves these tubules open to external stimuli, allowing temperature changes to irritate the dental pulp.
Common Causes and Prevention
Gingival recession results from a combination of biological and behavioral factors. One primary contributor is periodontal disease, an infection caused by the long-term buildup of bacterial plaque and hardened tartar below the gum line. This chronic inflammation destroys the supporting gum tissue and underlying bone structure, causing the gums to detach and migrate down the root surface.
Another common factor is mechanical trauma, often resulting from overly aggressive or improper tooth brushing techniques. Habitually scrubbing the teeth horizontally with a hard-bristled toothbrush can physically wear away the delicate gum tissue over time. This abrasion often results in V-shaped defects at the neck of the tooth and is a direct physical cause of tissue loss.
Genetic predisposition also plays a role, as some individuals naturally have thinner gum tissue or less robust alveolar bone surrounding their teeth. For prevention, it is recommended to replace firm toothbrushes with soft-bristled models and to use a gentle, circular brushing motion. Regular dental checkups and professional cleanings are important for monitoring gum health. These cleanings remove hardened plaque that cannot be eliminated at home, controlling the inflammatory component that drives recession.