The Fundamental Role of Cementum
Cementum is a specialized, calcified tissue that covers and protects the root surface of a tooth. It is a critical component of the periodontium, the system that supports teeth in the jaw. Its main function is to provide an attachment surface for the periodontal ligament (PDL), a network of fibers that anchors the tooth root to the alveolar bone. Without cementum, the periodontal ligament would have nothing to secure the tooth, leading to instability.
Chemically similar to bone, cementum differs by being avascular—it lacks a blood supply. Instead, its nutrition is diffused from the vascular periodontal ligament. While it is a hard tissue, it is less mineralized than both enamel and dentin, making it softer and more susceptible to abrasion if exposed.
The Continuous Thickening of Cementum with Age
The most notable change to cementum over a person's lifespan is its continuous deposition, leading to an increase in thickness. This is a physiological response, not necessarily a sign of disease. Researchers have observed this phenomenon in both human and animal studies. While the exact molecular mechanisms behind this relentless apposition are not fully understood, it serves several important biological functions.
Why does cementum thicken?
- Protective Adaptation: The thickening of cementum is believed to be a protective adaptation to the years of mechanical stress from chewing and mastication. It provides additional anchorage and helps reduce tooth mobility, which naturally occurs as a person ages and experiences some bone resorption.
- Compensating for Wear: As the crowns of teeth wear down over a lifetime, the continuous eruption of the tooth from its socket helps maintain a constant occlusal surface. The addition of new cementum at the root end helps compensate for this slow, passive eruption, preserving the length of the tooth's root within the bone.
- Maintaining Attachment: Since the surface layer of cementum can age or become compromised, continuous deposition of new cementum ensures the attachment point for the periodontal ligament remains intact and functional.
The two types of cementum
Cementum is primarily categorized into two types based on the presence of cells and the origin of its fibers. Both types are deposited throughout life, but at different rates and locations.
Acellular (primary) cementum
This type is deposited first during tooth development and is found mainly on the coronal half of the root. It is relatively thin and does not contain any entrapped cells (cementocytes). Its primary function is providing anchorage for the tooth via extrinsic collagen fibers that run perpendicular to the root surface.
Cellular (secondary) cementum
Located more apically (towards the root tip), cellular cementum contains living cells (cementocytes) within its mineralized matrix. It is generally thicker and forms after the tooth has fully erupted and come into function. This type of cementum is responsible for much of the age-related thickening, especially around the root apex. It incorporates both extrinsic fibers from the PDL and intrinsic fibers created by the cementoblasts themselves.
Comparison of Acellular vs. Cellular Cementum
| Feature | Acellular (Primary) Cementum | Cellular (Secondary) Cementum |
|---|---|---|
| Location | Coronal (neck) and middle of root | Apical (tip) of root |
| Formation Time | Formed during tooth development | Formed after tooth is in function |
| Cell Content | No cells (acellular) | Contains cells (cementocytes) |
| Thickness | Relatively thin | Thicker, especially apically |
| Fiber Type | Primarily extrinsic fibers | Extrinsic and intrinsic fibers |
| Primary Function | Initial tooth anchorage | Long-term anchorage, compensation |
Implications for Senior Dental Care
The age-related changes in cementum have several important implications for oral health, particularly for seniors.
Increased root sensitivity and decay
As individuals age, gingival recession—the pulling back of the gums—is common. When the gums recede, they can expose the root surface, which is covered by the relatively thin layer of cementum. Since cementum is less mineralized and lacks enamel's protective strength, it is more vulnerable to abrasion and decay. If the cementum is worn away, the underlying dentin, which contains tiny tubules connected to the pulp, is exposed, leading to increased tooth sensitivity to hot, cold, or sweets. This can increase the risk of root caries, a significant concern in older adults.
Impacts on dental treatments
The continuous deposition of cementum is so reliable that it is used in forensic age estimation. For dental professionals, the changes associated with an aging tooth affect treatment strategies. In cases of advanced periodontal disease, new cementum must be regenerated for the periodontal ligament fibers to reattach, highlighting the importance of specialized periodontal therapies. Additionally, the stiffer response of older teeth due to thicker cementum can influence orthodontic treatments or restorative procedures. Understanding these age-related biological shifts is crucial for providing effective and appropriate care.
Conclusion: A Natural Part of Aging
The answer to the question "Does cementum increase with age?" is a definitive yes. This continuous thickening is a natural, physiological process that helps maintain the stability and function of teeth over a lifetime. While it is a protective adaptation, it also brings specific challenges in later life, particularly related to the exposure of the root surface. Regular dental check-ups become even more critical for seniors to monitor these changes and address any issues, such as root decay or sensitivity, that may arise from a lifetime of wear and tear. Recognizing that this process is a normal part of aging is a key step toward maintaining excellent oral hygiene throughout one's golden years. For more information on aging and dental tissues, you can refer to the National Institutes of Health(https://pmc.ncbi.nlm.nih.gov/articles/PMC7734349/).
