Dentin is a part of our teeth, positioned beneath the hard outer layers of enamel on the crown and cementum on the root. This specialized tissue provides structure and support for the tooth’s outer shell. It also encases the soft pulp, which houses the tooth’s nerves and blood vessels.
Understanding Dentin’s Structure
Dentin forms the majority of the tooth’s structure, giving it shape and rigidity. It is a yellowish, porous material that is harder than bone but not as hard as enamel. It is composed mainly of inorganic materials, organic materials, and water. This composition provides dentin with both hardness and a degree of elasticity.
A distinguishing characteristic of dentin is its microscopic network of tiny channels called dentinal tubules. These tubules extend outwards from the pulp chamber, where the odontoblast cells reside, towards the outer surface of the dentin, reaching the enamel-dentin junction in the crown or the cemento-dentinal junction in the root. The tubules are larger near the pulp and become narrower towards the outer surface, often branching as they approach the enamel or cementum.
Each dentinal tubule contains fluid and a cellular extension from an odontoblast, which are specialized cells that produce dentin. These tubules also contain nerve fibers, particularly near the pulp. The fluid within these tubules plays a role in transmitting sensations from the tooth surface inward, making dentin important for perceiving stimuli.
Why Teeth Become Sensitive
Dentinal hypersensitivity, commonly known as tooth sensitivity, occurs when the protective layers of enamel or cementum are lost, exposing the underlying dentin and its network of dentinal tubules. This exposure allows external stimuli to directly affect the fluid within these tubules, leading to a sharp, transient pain. The hydrodynamic theory explains this pain: when stimuli like hot, cold, sweet, acidic substances, or even touch, cause the fluid inside the exposed tubules to move, this movement stimulates nerve endings located near the pulp, triggering a pain response.
Several factors can lead to the exposure of dentinal tubules. Gum recession, where the gum tissue pulls away from the tooth, is a common cause, often resulting from aggressive brushing, periodontal disease, or even thin bone structure. Enamel erosion, which involves the gradual wearing away of the enamel, can be caused by frequent consumption of highly acidic foods and drinks, such as sodas or citrus fruits. Tooth grinding, or bruxism, also contributes by causing excessive wear on the enamel, exposing the dentin.
Other contributors to exposed dentin and sensitivity include cracked teeth, fractured teeth, or worn-out fillings that no longer provide adequate coverage. Dental procedures like professional teeth whitening, which can open occluded tubules, or scaling and root planing, which might remove cervical cementum, can also temporarily increase sensitivity.
Strategies for Managing Dentinal Sensitivity
Managing dentinal sensitivity involves both at-home care and professional dental interventions, aiming to either block the exposed dentinal tubules or reduce nerve excitability. A primary at-home strategy is using desensitizing toothpastes, which contain active ingredients like potassium nitrate or strontium chloride. Potassium nitrate blocks pain signals, while strontium chloride helps to block the dentinal tubules, preventing external stimuli from reaching the nerves. These toothpastes require consistent use over a few weeks for relief.
Adopting proper oral hygiene techniques is beneficial. Using a soft-bristled toothbrush with gentle strokes helps prevent further gum recession and enamel abrasion, which can otherwise worsen sensitivity. Limiting the intake of highly acidic foods and drinks, such as carbonated sodas or fruit juices, can also reduce enamel erosion and protect the dentin. For individuals who grind their teeth, wearing a custom-fitted nightguard can protect the enamel from excessive wear and alleviate sensitivity caused by bruxism.
When at-home methods are insufficient, dental professionals offer various in-office treatments. Fluoride varnish applications are used; this varnish forms a protective layer over the dentin, strengthening enamel and reducing fluid flow within the tubules. Dentin bonding agents can also be applied to cover the exposed dentin surface with a thin plastic material, sealing the tubules. For severe gum recession, a gum graft may be considered to cover the exposed root surfaces. For severe and persistent sensitivity, if other treatments fail, root canal therapy might be recommended to remove the affected nerve and eliminate pain.