Dentin Hypersensitivity

Author: Boban Fidanoski

Definition of Dentin Hypersensitivity

Dentin Hypersensitivity is short, sharp pain arising from exposed dentin in response to stimuli, typically thermal, evaporative, tactile, osmotic or chemical and which cannot be described to any other dental defect or pathology. It is an exaggerated response of dentin to non-noxious stimuli and satisfies all the criteria to be classified as a true pain syndrome.

Mechanism of Dentin Hypersensitivity

Mechanism of dentin hypersensitivity is most commonly explained by the Brannstrom’s Hydrodynamic Theory. It proposes that stimuli are transmitted to the pulp surface via movements of the fluid or semifluid materials in the dentinal tubules. Fluid movement acts as the transducing medium for conveying peripheral stimuli to free nerve endings of A-delta fibers near the odontoblastic layer by the pulp-dentin interface. This reaction results in a pain response.

Phases in development of hypersensitivity

Phase One: Dentin is exposed (lesion localization), through either loss of enamel or gingival recession

Phase Two: Dentinal tubules are open to both the oral cavity and the pulp (lesion initiation).

Etiology of Dentin Hypersensitivity

1. Attrition:	Pathologic tooth-to-tooth wear from opposing tooth contact. Commonly found on the incisal and occlusal surfaces. E.g.: Bruxism: medical term for the grinding of teeth (horizontal movements) or the clenching of jaws (vertical movements), especially during deep sleep or while under stress.
2. Abrasion:	Pathologic tooth wear as a result of a foreign substance. E.g.: Improper use of toothbrush coupled with force, method, frequency, duration of tooth brushing, as well as the high abrasiveness of the toothpaste.
3. Endogenous (Intrinsic) Erosion:	Pathologic loss of tooth structure as a result of internal chemical agents. E.g.: Acid regurgitation associated with GERD - Gastroesophageal reflux disease or with Bulimia nervosa. With regurgitation, the process when gastric acid comes in contact with the teeth and dissolves tooth structure is known as Perimolysis. It is most marked on the palatal surfaces of maxillary anterior teeth. The maxillary posterior teeth are affected more than the mandibular posterior teeth, particularly on the palatal surfaces. The mandibular anterior teeth are never affected as they are protected by the tongue. pH of vomitus is 3.8.
4. Exogenous (Extrinsic) Erosion:	Pathologic loss of tooth structure as a result of external chemical agents E.g.: Dietary factors that contribute to a highly acidic oral environment: frequent consumption of acidic, carbonated, fruit drinks or sugar. Any food substance with a critical pH value of less than 5.5 can becomes a corrosive and demineralizes teeth. Whitening agents: main side effect of tooth whitening is dentin hypersensitivity
5. Abfraction:	Pathologic loss of piece of the tooth structure from biomechanical forces (flexion, tension and compression) on the tooth caused by parafunctional habits. Abfraction is the microstructural loss of tooth substance in areas of stress concentration. This occurs most commonly in the cervical region of teeth, where flexure may lead to a breaking away of the thin layer of enamel rods, as well as microfracture of cementum and dentin. E.g.: Detrimental oral habits: fingernail biting, pipe smoking, tobacco chewing, hair pin opening

Common causes for most discomfort

Cold (in 35% of the cases), heat, sweet, combination of cold and sweet, acids, touching.

When dealing with hypersensitive teeth, it’s very critical to assess the status of the pulp. What are the steps one should complete during the assessment of the pulp?

By definition, dentin hypersensitivity is a diagnosis of exclusion. Therefore, before proceeding to management and treatment, conditions that present with symptoms mimicking

dentin hypersensitivity must be ruled out. Assessment steps to determine differential diagnosis with pulpal diseases (Pulpopatiae) are:

1. History of pain (chronology, nature, location, radiation, aggravating and alleviating factors)

2. Percussion and palpation tests

3. Inspection of the teeth and surrounding tissue

4. Thermal (heat and cold) and electric pulp tests (EPT)

5. Radiographic examination

Desensitizing agents. Characteristics of an ideal desensitising agent

1. Not irritate the pulp

2. Act rapidly

3. Be effective for long period

Desensitizing chemical agents

1. Potassium Nitrate (blocks neural transmission by pulpal nerves)

2. Fluorides (occludes dentinal tubules)

3. Stroncium Chloride (occludes dentinal tubules, effective on tactile hypersensitivity)

Desensitizing physical agents?

1. Protective Sealants ( Seal and Protect-Dentsply)

2. Lasers (CO2 or Nd:YAG )

3. Glass ionomer cements (hydrophilic, require etching, effective for class V)

Types of self applied desensitizing agents

1. Potassium Nitrate (KNO3) – 5% in dentifrices

2. Sodium Fluoride (NaF) – 0.5% in mouthrinse
- 1.1% in gel

3. Stannous Fluoride (SnF2) – 0.4% in gel

Patient may apply a range of these self-applied desensitizing agents in the form of dentifrices, gels or mouthrinses as part of their daily self-care regime at home.

Types of professionally applied desensitizing agents and how to apply them

1. Duraphat (Colgate Oral) - 5% Sodium Fluoride Varnish

Application procedure:
1. Select varnish product for application
2. Gather equipment for procedure
3. Provide client with informations about the procedure
4. Have client clean teeth with a toothbrush, unless oral prophylaxis has been scheduled for the same appointment
5. Recline patient in proper ergonomic position
6. Dry out application area
7. Inset saliva ejector
8. Using a cotton-tip or a syringe-style applicator, apply 0.3-0.5 ml of varnish to teeth
9. Dental floss may be used to draw the varnish interproximally
10. Allow client to rinse upon completition of procedure
11. Remind client to avoid eating 2-4 hours after application and avoid brushing teeth the night of the application.

2. Gel-Kam Dentin Block (Colgate Oral Pharmaceuticals)
1.09% Sodium Fluoride
0.4%Stannous Fluoride
0.14%Hydrogen Fluoride

Tray technique application procedure for Gel-Kam:
1. Assemble equipment

2. Seat client in upright position (Prevents gagging and accidental ingestion of fluoride gel/foam)

3. Provide client with informations about the procedure and obtain consent

4. Try tray of appropriate size

5. Load fluoride gel/foam into trays: 2ml maximum for children, 2.5ml maximum for adults

6. Isolate teeth with cotton rolls. Dry with air syringe.

7. Insert mandibular tray. (Ensures coverage into interproximal spaces).

8. Press tray against teeth.

9. Air dry maxillary arch and insert maxillary tray.

10. Press tray against teeth and ask client to close mouth and bite gently on trays or cotton rolls

11. Place saliva ejector over mandibular tray. Set timer for 4 minutes. Never leave client unattended. (Maximum fluoride exposure requires 4 minutes)

12. Tilt chin down to remove trays

13. Ask client to expectorate; suction excess fluoride with saliva ejector

14. Instruct client not to eat, drink, or rinse for 30 minutes

15. Record service and type of fluoride used in the client’s chart

3. Seal and Protect –Dentsply
Tri-methaacrylate resin
Application procedure:
To apply the product, the area to be treated is isolated, rinsed, and blot dried. Seal & Protect is then applied in sufficient amounts to keep the area wet for 20 seconds. A gentle stream of compressed air is used to volatilize the acetone solvent and the material is light cured for 10 seconds. A second coat is then applied, dried, and light activated. Dentsply/Caulk claims the product provides symptomatic relief for up to 6 months.

Potassium Nitrate: active ingredient in desensitizing toothpaste

5% Potassium Nitrate (chemical formula: KNO3) is the active ingredient in desensitizing toothpaste. Potassium Nitrate in conjunction with Sodium Fluoride in the toothpaste significantly reduces symptoms within two weeks.

Mechanism of action: Potassium ions penetrate into the dentinal tubules and block repolarization of the sensory receptors of neuron’s dendrites of the pulp those usually carry out the pain impulse to the Central Nervous System.

After initial depolarization and transmittion of the impulse to the brain, a repolarization is expected to occur, where ions of Potassium leave the neuron’s membrane into the surrounding tubular fluid due to a lower concentration gradient. If we apply additional Potassium into the dentinal tubules, concentration gradient of Potassium in the tubules will be higher than the one in the neuron’s membrane and in that way potassium from the membrane won’t be able to exit the membrane and allow repolarization. If repolarization is blocked, nerve can’t conduct another action potential (impulse), and CNS will stop receiving pain impulses. If elevated levels of potassium nitrate are maintained, the depolarized state decreases the perception of pain. It can almost be described as a numbing effect on dentin hypersensitivity.

__________________________________________________________________________

Bibliography:

¨ John O. Grippo at al. Attrition, abrasion, corrosion and abfraction revisited; A new perspective on tooth

surface lesions- JADA, Vol. 135, August 2004

¨ Kielbassa A. Dentine Hypersensitivity: Simple steps foreveryday diagnosis and management. International Dental Journal

¨ Canadian Advisory Board on Dentin Hypersensitivity •Consensus-Based Recommendations for the Diagnosis and Management of Dentin Hypersensitivity

¨ Dentin Hypersensitivity in 21-st Century;Complex causes and successful treatment options – Dani Botbyl, RDH

¨ Eshter M. Wilkins – Clinical Practice of the Dental Hygienist 8-th edition

¨ Darby and Walsh – Dental Hygiene Theory and Practice 2-nd edition

author: Boban Fidanoski

© December 20-th, 2006 Copyright - Text, diagrams, figures and photographs
by B.Fidanoski- Port Credit, ON - Canada