Dentinal hypersensitivity. Prevalence &Distribution Etiology Mechanism of dentinal hypersensitivity Dentin Innervation Differential diagnosis. Prevention. Treatment considerations.
Dentine HypersensitivityDefinition: “Dentine hypersensitivity is characterized by short, sharp pain arising from exposed dentine in response to stimuli typically thermal, evaporative, tactile, osmotic or chemical and which cannot be ascribed to any other form of dental defect or disease”.
Incidence The incidence of dentin
hypersensitivity ranges from 10 to 30 percent of the general population.Dentinal Hypersensitivity affect 20 to 40 yrs. of age group with peak incidence occuring at 25 – 30 yrs. of age and decrease during fourth and fifth decades of life . It affects females more often than males .
Most often affect canines and premolars.
Two-process need to occur for dentine hypersensitivity to arise:
Dentine has to become exposed (lesion localization),
And the dentine tubule system has to be opened and be patent to the pulp (lesion initiation).
Lesion localizationLesion localization occurs by exposure of dentin, either by loss of enamel or by gingival recession. Gingival recession is the more important of these two factors.
1) Loss of enamel:- Loss of enamel is generally considered under
heading of Attrition, Abrasion, Erosion and Abfraction.
Attrition:- due to tooth-tooth contact occlusally and proximally.( Bruxism)
Abrasion:- Due to faulty tooth brushing, occupational habits, improper flossing.
Erosion:- Due to extrinsic and intrinsic factors such as carbonated drinks, lemon sucking, gastric reflux, anorexia nervosa.
Abfraction:- Micro fractures in the cervical region due to heavy eccentric occlusal forces.
2) Gingival recession:- The most common clinical cause for exposed dentinal tubules is gingival recession When gingival recession occurs, cementum is exposed. Cementum being a very thin outer protective layer on dentin, is easily abraded or eroded away
Causes of gingival recession- Tooth brush abrasiona) In adequate attached gingiva b) Prominent rootsc) Oral habits resulting gingival lacerationd) Excessive flossinge) Crown preparation
Not all exposed dentine is sensitive. The localized dentinal hypersensitivity lesion must be initiated, this means dentine tubule system has to be opened and be patent to the pulp.
This occurs when the smear layer or tubular plugs are removed, which opens the outer ends of the dentinal tubules.
There are differences between hypersensitive and non–hypersensitive dentin in that there are more and wider open dentinal tubules in sensitive dentin .
Theories of pain transmission through dentine.
Direct neural theory
Direct Neural Theory Dentin innervated directly.
Limitations :-No evidence has been found for
nerves in the outer dentine.
Application of local anesthetic to the exposed dentine does not eliminate dentine sensitivity
Acc . to This theory odonoblasts act as a receptor cell.
No synaptic relationship between odontoblast and pulpal nerves.
The membrane potential of the odontoblsts measured in vitro is too low to permit transduction.
Hydrodynamic theory THE MOST ACCEPTED THEORY OF PAIN
TRANSMISSION IS THE HYDRODYNAMIC THEORY
THIS THEORY EXPLAIN DENTINE SENSITIVITY INVOLVES MOVEMENT OF FLUID WITHEN THE DENTINAL TUBULE WHICH ACTIVATES PULPAL RECEPTORS.
These stimuli are transmitted through the dentinal tubules to mechanoreceptors within the dentinal tubules near the pulp.
Mechanism of DH
Innervations of Dentine
The pulp of tooth is innervated richly.
Nerves enter the pulp through the apical foramen, along with afferent blood vessels, together form the neurovascular bundle.
The nerve bundles enter the pulp consists of sensory afferent nerves of trigeminal nerve and sympathetic branches from the superior cervical ganglion.
The nerve fibers form extensive plexus in the cell free zone of weil, just below the cell bodies of the odontoblasts, which is called as subodontoblastic plexus of raschkow.
Dentinal tubules contain numerous nerve endings in the inner dentin, no further than 100 to 150 micrometer from the pulp.
No organized junction or synaptic relationship has been noted between axons and the odontoblast process
It is considered that pain is the only sensation which can be elicited by any stimulus applied to the teeth (excluding the periodontal receptors).
Pain is mainly carried by A delta and C fibers. A delta are large, myelinated fibers so associated with sharp pain. While C fibers are small, unmyelinated so transmits late, dull pain.
Differential diagnosis: 1) Cracked tooth: - Pain typically occur on release of biting.2) Dental caries: - Sensitivity is experienced when dental decay passes
the dentino-enamel junction.3) Gingival recession: - Often occurs post-periodontal surgery, due to ageing,
mechanical trauma, frenum attachment pulls or occlusal trauma.
4) Toothbrush abrasion: - Caused by use of a hard toothbrush or a soft
toothbrush with abrasive toothpaste or by aggressive brushing, and generally located on the side opposite the dominant hand. It is most common cause of dentinal hypersensitivity.
5) Abfraction lesions: - Generally associated with occlusal trauma where the anatomic crown of the tooth has flexure.
6) Erosive lesions: - Associated with acid reflux, hiatus hernia, purging, bulimia (intrinsic causes), and diet (extrinsic causes).
7) Genetic sensitivity: - It is not known whether sensitivity correlates to the 10 percent of teeth that do not have cementum covering all the dentine at the DEJ, or is a factor of lower patient pain threshold values.
8) Restorative sensitivity: - Dentin sensitivity develops under restorative materials for a number of different reasons.
- Dentine removal during cavity preparation. - Dentine exposed to thermal, vibratory, evaporative insults. - Contamination of composites during placement or improper etching of the tooth. - Incorrect preparation of glass ionomer or zinc phosphate cements.
- Unpolymerized monomers which can diffuse into the pulp and cause irritation. - Class II restorations, involving proximal boxes which terminate below the CEJ. - Some patients complain of dentin sensitivity on teeth covered with a full crown restoration. The sensitivity could be on the root surface or it could be due to leakage under the crown due to the loss of luting cement.
9) Medication sensitivity: - Due to medications that dry the mouth (e.g. antihistamines, high blood pressure medication) thereby compromising the protective effects of saliva and aggravating diet related trauma or proliferating plaque.
10) Bleaching sensitivity: - Commonly associated with carbamide peroxide vital tooth bleaching and thought to be due to the by products of 10 per cent carbamide peroxide readily passing through the enamel and dentine into the pulp in a matter of minutes.
In some individuals the cementum and enamel which normally cover the dentine do not meet and result in dentine exposure as a result of a developmental anomaly. In general, it appears that dentinal hypersensitivity is rarely a result of just one of the above factors, but rather a combination of more than one factor.
Preventive recommendations for dentinal hypersensitivity:
Suggestions for patients: Avoid using large amounts of dentifrice or
reapplying it during brushing. Avoid medium- or hard-bristle toothbrushes. Avoid brushing teeth immediately after
ingesting acidic foods. Avoid overbrushing with excessive pressure
or for an extended period of time. Avoid excessive flossing or improper use of
other interproximal cleaning devices. Avoid “picking” or scratching at the gumline
or using toothpicks inappropriately. .
Suggestions for professionals:
Avoid overinstrumenting the root surfaces during scaling and root planing, particularly in the cervical area of the tooth.
Avoid overpolishing exposed dentin during stain removal.
Avoid burning the gingival tissues during in-office bleaching, and advise patients to be careful when using home bleaching products
There are two strategies in treating D. Hypersensitivity:
First: Plug (seal) the D.T preventing fluid flow:
Covering the outer end of the tubules
Occlusion of the lumen of the tubules
Second: desensitize the nerve, making it less responsive to stimulation
Treatment of dentinal hypersensitivity : home use products.
Treatment of Dentinal hypersensitivity :in office products.
Treatment consideration for Dentinal Hypersensitivity associated with lost tooth structure.
Treatment consideration for bleaching associated sensitivity.
Treatment of dh :home use products
Desensitizing toothpastes/dentifrices: - Toothpastes are the most widely used dentifrices for delivering the desensitizing agents. The first desensitizing toothpastes to appear on the market claimed either to occlude dentinal tubules (those that contained strontium salts and fluorides) or destroy vital elements within the tubules (those that contained formaldehyde). Toothpastes containing potassium salts are used widely nowdays. Potassium ions are thought to diffuse along dentinal tubules and decrease the excitability of intradental nerves by altering their membrane potential.
Potassium ion may depolarize the nerve and prevent it from repolarizing, thereby, preventing it from sending pain signals to the brain .
Dentifrices should be applied by toothbrushing. There is no evidence to suggest that finger application of the paste increases effectiveness.
Mouthwashes and chewing gums. Mouthwashes containing potassium nitrate and sodium fluoride, potassium citrate can reduce DH. Also chewing gum containing potassium chloride significantly reduced DH.
Treatment of Dh :in office products
1. Treatment agents that do not polymerize
2. Treatment agents that undergo setting or polymerization reactions
3. Use of mouthguards
Varnishes/precipitants a) 5% sodium fluoride varnish b) 1% NaF, 0.4% SnF2, 0.14% HF solutions c) 3% mono potassium –monohydrogen
oxalate d) 6% acidic ferric oxalate e) Calcium phosphate preparations f) Calcium hydroxide
1)Treatment agents that do not polymerize
FLUORIDES: Fluorides such as sodium fluoride and stannous fluoride can reduce dentin sensitivity. Fluorides decrease the permeability of dentin, possibly by precipitation of insoluble calcium fluoride within the tubules OXALATE :The reduction in dentine permeability for 2% potassium oxalate was recorded at 95.71 % . This desensitizing agent combines the tubule-occluding properties, with the inhibitory effect of potassium onnerve activity.
2)Treatment agents that undergo setting or polymerization reactions Conventional GIC cements: - Reports suggests that there is complete loss of hypersensitivity in 89.7% patients.
Resin re-inforced glass ionomer / compomers: -
Adhesive resin primers: - Occludes open dentinal tubules and reduces DH effectively. disadvantages- Resins in thin films reacts with atmospheric oxygen that interferes with free radicle of polymerisation reactions causing unpolymerised layer of 20µm thick which would lost quickly. Inability of resin tags to to bond the walls of dentinal tubules. Adhesive bonding systems: -
3)Use of mouthguards: - The mouth guard type appliance is used to deliver potassium nitrate desensitising agent in gel form. But studies showed only partial success in reduction of hypersensitivity.
4)Iontophoresis: -This procedure uses low voltage current to enhance diffusion of ions into the tissues.Dental iontophoresis is used most often in conjunction with fluoride pastes or solutions and reportedly reduces DH.
Laser treatment of Dentin Hypersensitivity Nd:YAG laser CO2 laser Diode Laser could cause melting of dentin and
closure of exposed dentinal tubules without dentin surface cracking
The sealing depth of Nd:YAG laser on human dentinal tubules was 4 μm
Best combined with sodium fluoride or stannous fluoride varnish
Treatment consideration for DH associated with lost tooth structure.
The patient with lost tooth structure at the cervical area and presents with dentin sensitivity, the best treatment is the use of restorative materials.
Eg.Glass ionomer cements.Resin modified GICComposites. Etc.
Treatment consideration for bleaching associated sensitivity:
Tooth sensitivity during bleaching is common, yet unpredictable.
Often the sensitivity experienced is ‘mild’ and required no alteration in the treatment protocol.
In cases where it cannot be ignored, the dentist may have to instruct the patient to decrease the frequency (typically, to every other day) and duration of treatments.
When this protocol fails, advocate use of topical fluorides in conjunction with the beaching treatments or recommend using desensitizing toothpaste for 2-3 weeks during bleaching.
Persons experiencing nighttime sensitivity may switch to daytime wear and reduce contact time of the peroxide to 2-4 hours.
In severe cases patients may have to stop bleaching for a few weeks or even altogether.
Conclusion: - In cases of slight to mild sensitivity, educational advice, including the role of desensitizing dentifrices containing either strontium salts (chloride or acetate) or potassium salts (chloride or nitrate) will be of valuable help. In moderately sever cases, varnishes containing highly concentrated fluorides can be used successfully. Follow –up care, accompanied by re instruction and continued home-use of desensitizing toothpastes. In cases of severe hypersensitivity, the treatment should be invasive including the use of agents that set (e.g. glass ionomers, composites.) to occlude the dentinal tubules are used.