The third most frequent complaint in dentistry in the world is tooth sensitivity, which is also referred to as dentin hypersensitivity. The pain will be seen as acute and sharp when the dentin or cementum in the teeth are exposed to heat, pressure, osmosis or exposure to the chemicals or to hot beverages, cold air or acidic food. Yet, as frequent as it is, there are not so many individuals aware of the physiological aspects behind whatever makes some teeth feel that way. Sensitivity of a tooth is not an illness but a symptom of some alterations in the structure of the tooth or a living tooth itself. The study of these processes will lead us into the study of the anatomy of the teeth, the dentin and its tubes, the nerve channels, and the hydrodynamic theory of pain sensation.
In this review, we address the physiology of tooth sensitivity, determinants of the same, and management. As a clinical review of the disease and methods of its treatment, comprehensive guide on tooth sensitivity.
The Anatomy of Tooth Sensitivity
What Causes Sensitive Teeth? To get to know what makes the teeth sensitive, it is necessary to realize that there are some layers in the teeth. A tooth consists of three components.
- Enamel: The push like hard tissue on the top of the tooth crown which envelops the entire surface of the tooth which is mineralized and protective.
- Dentin The layer just under the enamel is yellow and is porous with microscopic islets called dentinal tubules
- PULP: This is the inner layer of a tooth that has blood vessels, connective tissues and contains nerve fibers that transfer sensations.
The enamel on the crown protects the dentin and a layer of root cementum (as opposed to enamel) protects the root. When these natural barriers are lost, by erosion of the dental substance, or by recession of the mucous membrane of the gums, or by abrasion of a tooth-brush, the dentin is exposed. The source of sensitivity is in this uncovered dentin.
Dentinal Tubules: Pathways of Sensation
Dentin is not homogenous, but it is composed of many tiny canals, called dentinal tubules, that extend to the pulp over the outermost surface of the dentin. The tubules have a diameter of approximately 0.8-2.5 micrometers and a fluid (mostly a plasma-like fluid) and processes of odontoblast cells, which cover the pulp.
When the stimuli of cold wind/boiling coffee/acid food get in contact with the exposed dentine, the flow of fluid in these tubules is temporarily stopped. The nerve endings in the pulpal terminus of the tubules are stimulated by such fluid movements, and are perceived as the short-lived severe pain experienced by dentin hypersensitivity.
As has been shown, the most sensitive teeth are the ones that have these two characteristics (high density of tubules and big diameter of tubules). This is also the reason teeth eroded or worn down by abrasion are more sensitive because the tubules are mostly exposed when the protective smear layer that covers the tubules is removed, which makes the tubules in all ways open to whatever stimulus passes by.
The Hydrodynamic Theory: The Most Popular Theory
Among the numerous theories to account for tooth sensitivity, the direct innervation theory, the odontoblastic transduction theory and the hydrodynamic theory, the latter is the most general one.
According to the works of the brannstrom in the 1960s, the hydrodynamic theory tells that tooth pain is caused by the displacement of fluid in the dentinal tubules that mechanically excite pulpal nerve endings.
Exposed dentin, when subjected to stimuli:
- The cold stimuli cause shrinkage of the dentinal fluid which causes inward flow.
- Expansion is caused by heat, and this leads to outflow.
- Sweet or acidic compounds cause changes in osmosis and enhance the flow of the fluid.
This movement causes mechanoreceptors present at pulp-dentin junctions. A-delta fibers-thinly myelinated nerve fibers, which carry sharp and fast pain impulses, compose a large part of these receptors. The resultant is a sharp, acute pain which stops when the stimulus is removed.
This model is not new to clinical results: desensitizing agents which hinder or delay the flow of fluids through tubules (e.g. potassium nitrate or fluoride varnish) are often efficient to reduce the symptoms, which once again conforms to the hydrodynamic mechanism.
Neural Pathways and Signal Transmission to the Sensory
Nerves that add to sensitivity of teeth are largely branches of the trigeminal nerve (cranial nerve V)- the largest of sensory nerves of the face. The tooth has two large types of sensory fibrous which are involved in the conduction of pain:
- A-delta fibers: These are myelinated and conducting fibers which transmit pain in a sharp and well localized pain when irritation is caused on the dentin. They are the major mediators of cold and tactile sensitivity.
- C fibers: C fibers are low speed, unmyelinated and contain dull and throbbing pain that is usually associated with inflammation or pulpitis.
The A-delta nerve fibers are stimulated when advective flow in dentinal tubules occurs, and the signal is spread out of dentin through the pulp to trigeminal ganglion then through the brainstem it is perceived as pain. This rapid recruitment and turn-off of these A-delta fibers is the cause of the short and sharp feeling of tooth hypersensitivity.
5. Common Causes of Sensitive Teeth
There are multiple tooth sensitivity causes due to exposure or damage of the dentin, including:
a. Erosion of Enamel
With time, acidic foods and drinks such as citrus fruits, soda, and vinegar can erode enamel. The vitreous enamel is worn away and dentine is left bare.
b. Receding Gums
Your gums can recede due to improper brushing or gum disease, and when the gum pulls back it reveals the cover of the tooth root known as the cementum and the dentin beneath it making it much easier for sensitivity to take hold.
c. Abrasion and Dentin Tenuity
Brushing too hard with a stiff toothbrush or using abrasive toothpaste can wear down enamel and expose dentin.
d. Dental Procedures
Whitening, cleaning or reconstructive treatments might increase sensitivity for a while on account of alteration of the dentin surface or the elimination of the protective smear layer.
e. Cracked or broken teeth
Fractures and microcracks allow stimuli to enter the interior of dentin, leading to the formation of sensitivity or pitting inflammation.
6. Role of Saliva and Oral Environment
Saliva contributes to the regulation of sensitivity acting as a natural buffer and lubricant. It neutralizes the acid, provides the calcium and phosphate ions needed for remineralization and contributes to an ideal pH. Hyposalivation, called xerostomia, is a predisposing factor for enamel wear and dentin exposure, resulting in increased sensitivity.
In addition, a healthy oral microbiome promotes enamel strength and prevents remineralization. Long-standing plaque retention may also produce acids that dissolve enamel and open dentinal tubules, making daily oral hygiene an indispensable preventive measure.
7. Prevention and Treatment Options
Tooth sensitivity can be frightening, but it can be controlled with professional treatment or at home.
a. Desensitizing Toothpastes
These have ingredients like:
- Potassium nitrate, which suppresses nerve activity by depolarizing nerve endings in the mouth.
- Stannous fluoride or strontium chloride, which block dentinal tubules.
Consistent use may see a significant reduction in symptoms within a few weeks.
b. Fluoride Treatments
Professional application of fluoride gels or varnishes can also promote the remineralization of the enamel and seal the exposed dentinal tubules, thus reducing their permeability.
c. Resin Sealants and Bonding Agents
Resins or bonding agents also can be applied by dentists to form a protective layer over the exposed dentin, shielding it from the sensations of heat and cold.
d. Lifestyle and Dietary Modifications
Limiting acidic drinks, sipping them through a straw and waiting a minimum of 30 minutes before brushing after eating are all tips on reducing enamel wear.
e. Gentle Oral Hygiene
A soft-bristled toothbrush and mild abrasive toothpaste can help to minimize additional mechanical wear. Proper Brushing Technique – Brush Tepe at the 45° angle to the gum line to prevent gum festival.
f. Treating the Underlying Cause
When sensitivity is the result of gum disease, bruxism (teeth grinding), or tooth decay, addressing the underlying problem is crucial to achieving lasting relief.
8.Recent Progress in Treating Dental Hypersensitivity/Tooth Sensitivity
Contemporary dental practice is continually advancing in the development of bioactive and regenerative treatments to treat dentin hypersensitivity. New products are:
- Formulations are nanohydroxyapatite which is very similar to the natural mineral component of a tooth and window enamel to integrate with and occlude tubules.
- Bioglass technology, which facilitates calcium and phosphate ions release to remineralize the dentin surface.
- Laser treatment, which closes dentinal tubules and changes nerve conduction to reduce pain perception.
- Oxalate-containing compounds which result in the formation of crystalline deposits inside the tubules and which diminish fluid flow.
These new therapies are exciting in that they may provide longer-lasting desensitization along with improved patient comfort.
9. When to Seek Dental Care
In many cases, mild sensitivity or pain can be treated at home but if pain is severe or lasts more than a couple days it may be symptomatic of more serious problems such as tooth decay, inflammation of the pulp, or cracked enamel. A dentist can determine the cause and suggest the right treatment. It is the irreversible pulp damage that results from an under-treated/dismissed sensitivity that carries the risk of more aggressive treatment such as root canal therapy.
10. Conclusion
The biological basis of tooth sensitivity is a physiological response at a molecular, cellular and tissue level due to dentinal tubules exposure and stimulation of pulpal nerves according to fluid mechanics. The hydrodynamic theory is the most complete explanation correlating the external stimulation with nerve activation through movement of dentinal fluid.
While the discomforting pain of sensitive teeth can be unbearable, knowing the biological process behind what causes it can help in how to prevent and treat it. Protect the enamel, stay on top of your oral hygiene and try desensitizing products to help get comfortable and protect your teeth. In short, tooth sensitivity is a reminder of the delicate interplay between dental structure, physiology and care — a balance that, when achieved, permits a lifetime of smile-based delights.
