Dentin hypersensitivity

              DENTIN HYPERSENSITIVITY

Dentin hypersensitivity is characterized by short, sharp pain arising from exposed dentin in response to stimuli typically thermal, evaporative, tactile, osmotic or chemical and which cannot be ascribed to any other form of dental defect or pathology. 

ETIOLOGY-

Several  predisposing factors lead to dentin hypersensitivity. Whenever there is loss of enamel or cementum leading to exposure of the underlying dentin, dentin hypersensitivity may occur. 

Etiology of dentin hypersensitivity-

ENAMEL LOSS                    CEMENTAL  LOSS

. Occulsal wear                 . Gingival recession

                                             . Periodontal disease

. Toothbrush abrasion  

                                              . Root planing

                                   

. Dietary erosion              . Periodontal surgery. 

. Abfraction

. Parafunctional habits             

DENTIN HYPERSENSITIVITY THEORIES-

Several theories have been proposed to explain this phenomenon. They include-

1) Direct innervation theory

2) Odontoblast deformation theory/transducer mechanism

3) Hydrodynamic theory. 

1) Direct innervation theory-

According to this theory, nerve fibers present within the dentinal tubules initiate impulses when they are injured and this cause dentinal hypersensitivity. However histolgic studies have shown that nerve fibers are present only in the predentin and inner dentinal zones but do not extend alll the way upto the dentinoenanel junction which is most sensitive area of dentin. Another finding that disputes  this theory is that when  pain inducing substance like pottasium chloride, acetylcholine and histamine are applied to exposed dentin, they fail to elicit a painful response. Due to these shortcomings, this theory is no longer accepted. 

2) Odontoblast deformation theory/Transducer mechanism-

This theory suggests that the odontoblast Or their processes are damaged when external stimuli are applied to exposed dentin. As a result of this they conduct impulses to the nerves in the predentin and underlying pulp from where they proceed to the central nervous system. 

This theory was also disfavoured as research has shown that the odontoblastic processes  extend only partly through the dentin and not upto the dentinoenamel junction. 

3) Hydrodynamic theory ( Brannstrom M) 

Presently, the hydrodynamic theory proposed by Brannstrom is the most accepted mechanism to explain dentinal hypersensitivity. 

The hydrodynamic theory states that whenever exposed dentin is stimulated by tactile, chemical, thermal or osmotic stimuli there is rapid movement of the dentinal fluid either towards the pulp or outward. This can cause-

. Direct stimulation of the  low threshold A-delta nerve fibers in the pulp. 

. Indirect stimulation of A- Delta nerve fibers in the pulp by displacing the odontoblastic cell bodies. 

Such rapid displacement of dentinal fluid in thousands of dentinal tubules at the same time produces a cumulative effect and this cause hypersensitivity. 

Clinical features-

1) Pain is the primary symptom of hypersensitive dentin. 

The patient usually experience a short, sharp pain in response to heat, cold, tactile stimuli, sweet or sour foods. 

This pain is considered to be an exaggerated response of the normal pulp - dentin complex  and is only felt on applications of the external stimulus.

DIAGNOSIS-

1) CASE HISTORY

2) CLINICAL EXAMINATION

1) CASE HISTORY-

  Elicit the following information:

1) The history and nature of the pain( sharp, dull etc) 

2) The number and location of sensitive teeth snd whether it is the same teeth that are always involved. 

3) The intensity of the pain( mild, moderate or severe. 

4) The stimuli which initiate the sensitivity. 

5) The frequency and duration of sensitivity. 

6) Other related events like history of recent restorative or periodontal treatment, dietary habits. 

2) CLINICAL EXAMINATION-

This should include the following tests and observation-

1) Evidence of dentin exposure ( gingival recession, loss of enamel) 

2) Sensitivity or pain on tactile examination of the suspected teeth. 

3) Evaporative stimulus- The suspected teeth is isolated using cotton rolls. If a momentary blast of air from the air/ water syringe causes sensitivity, it can confirm dentin hypersensitivity. 

4) Percussion sensitivity. 

5) Pain lingering after stimulus is removed. 

6) Vitality test to rule out pulpal involvement. 

7) Radiographic examination to check for caries, pulpal or periodontal movement. 

8) Signs of fractured, leaky or poor restoration margins. 

DIFFERENTIAL DIAGNOSIS-

The definitive diagnosis of dentinal hypersensitivity is more difficult when there are other conditions  causing reversible pulpitis present in combination with exposed dentin. Dentin hypersensitivity has to be differentiated from:

1) Fractured restoration

2) Fractured enamel exposing dentin

3) Dental caries

4) Post restoration sensitivity

5), Cracked tooth syndrome

6) Bleaching sensitivity. 

PREVENTION-

For patients who are suffering from dentinal hypersensitivity dentists can provide valuable advice to prevent or reduce the clinical symptoms. This includes the following measures-

1) Diet counselling especially regarding the consumption of acidic fruits and beverages. 

2) Correction of brushing techniques in order to prevent damage to the cervical enamel and supporting tissues. 

3) Care during operative procedures and while restoring teeth to avoid iatrogenic damage to tooth structure. 

4) Care during periodontal procedure like scaling and root planning. 

MANAGEMENT OF DENTIN HYPERSENSITIVITY-

There are two basic mechanism by which dentin hypersensitivity can be manager

1) Desensitization by occluding the dentinal tubules

2) Desensitization by blocking the pulpal sensory nerves. 

1) Desensitization by occluding the dentinal tubules-

A) Formation of smear layer over exposed dentin

This can be achieved by isolating the affected tooth and burnishing the dentin dry for a few minutes with a orangewood stick. This results in the formation of smear layer which partially occludes the dentinal tubules. 

B) Use of topical agents to occlude the exposed tubules

This method employs various agents like-

1) CALCIUM HYDROXIDE-

Calcium hydroxide powder can be mixed with distilled water to form a thick paste. This is then applied to exposed dentin for few minutes. But this method is not very successful as it only causes temporary occlusion of the tubules. 

2) CALCIUM PHOSPHATE Paste

Application of a paste of amorphous calcium phosphate (ACP) over exposed dentin has been reported to reduce dentin hypersensitivity. A commercially available product (GC Tooth Mousse) containing ACP and caesin phosphopeptide (CPP) is being recommended for treatment of dentin hypersensitivity as well as remineralization of incipient enamel caries. 

3) SILVER NITRATE-

Application of silver nitrate solution over the exposed dentin reduce fluid movement by precipitating  protein or silver chloride within the dentinal tubules. However, this agent is not popularly used  nowadays as it stains dentin and is also damaging to the pulp and gingiva. 

4) STRONTIUM CHLORIDE-

It acts by Penetrating the  tubules and forming strontium apatite which occludes the exposed dentinal tubules. 

5) FLOURIDES-

Agents such as sodium flouride, stannous fluoride or acidulated phosphate flouride may be used for a few minutes as mouthrinses, tooth pastes or as topical application over exposed dentin. 

6) FLUORIDE IONTOPHORESIS-

Iontophoresis is a procedure in which ions of a chosen medicament are driven into specific tisssues by means of therapeutic purposes. 

7) POTTASIUM OXALATE-

Application of pottasium oxalate solution over exposed dentin also reduce dentin hypersensitivity. 

8) VARNISHES-

Varnished act by forming a barrier over the exposed dentin. 

9) DENTIN ADHESIVES-

Recently the use of dentin bonding agents to treat dentin hypersensitivity has become popular. 

C) Placement of restoration

 Whenever a considerable amount of dentin is lost, it becomes necessary to replace the missing tooth structure. In such situation, a glass ionomer or a composite resin restoration may be placed to replace the lost tooth structure and seal the exposed dentin. This treatment provides a long lasting relief from hypersensitivity especially in patients exhibiting abrasion and erosion lesions. 

D) Use of Lasers

Recently lasers like co2, Nd:YAG, Er:YAG, diode and He:Ne lasers have been employed to treat hypersensitive dentin. However, lasers are expensive and not available for routine use. 

2) Desensitization by blocking pulpal sensory nerves

This mechanism of treating dentin hypersensitivity works by reducing the excitability of the sensory nerves in the pulp in response to various stimuli. Desensitizing toothpaste containing pottasium are used to block the pulpal sensory nerves from transmitting pain impulses. 

a) Pottasium nitrate toothpastes. 

Pottasium ions from pottasium nitrate toothpaste can easily pass through the dentin to the pulp. Here they block the depolarization of the sensory nerve endings present close to the odontoblast this preventing the transmission of impulses to the brain. The desensitizing effect of pottasium nitrate toothpaste generally requires two application a day for a minimum of two weeks. 

RECOMMENDED TREATMENT APPROACHES FOR DENTIN HYPERSENSITIVITY-

It depends on the extent and severity of the problem. At first conservative options should be employed. For isolated cases involving few teeth, first topical agents should be employed to occlude the dentinal tubules. 

Agents like calcium phosphate, pottasium ocalate, flourides, varnished and dentin adhesive must be used. 

If considerable dentin exposure is present as in abrasion, glass ionomer cement or composite resin restoration may be placed. 

In generalized hypersensitivity, desensitizing toothpaste containing pottasium nitrate, fluoride or strontium chloride must be employed for a few weeks. 

In cases of severe hypersensitivity not responding to any of these methods of treatment, endodontic therapy may be necessary as the final option.