INTODUCTION

Hypersensitivity following tooth preparation is a common problem faced by many clinicians.

Hypersensitivity can be present even after meticulous care by the clinician during and after the procedure following tooth preparation and definitive cementation of the restoration. This can lead to great mental stress for both the patient and the dentist.

However much of the hypersensitivity is preventable if the clinician takes few steps to address to this problem.

Methods to reduce Hypersensitivity following tooth preparation can be considered as:

1. DIAGNOSTIC AND PRETREATMENT PROCEDURES

2. CLINICAL PROCEDURES

3. POST TREATMENT PROCEDURES

DIAGNOSTIC AND PRE-TREATMENT PROCEDURE

The most important part of any restorative procedure is the appropriate diagnosis and its importance can never be overemphasized.

Thorough clinical, periodontal, occlusal and radiographic evaluations are necessary to properly evaluate the condition of the teeth. This is an important step to avoid unforeseen complication that can result in hypersensitivity.

 Following are the factors that can affect the ability of the teeth to recover from the trauma of tooth preparation and thus contribute to hypersensitivity:

1.DEEP CARIES

Deep caries can have a negative influence on the ability of the pulp to recover from the trauma of tooth preparation. This is seen in form of postoperative pulpal hyperemia, which can extend to longer durations and is perceived as thermal and percussive Hypersensitivity. If the caries is quite deep and prognosis is questionable it is better to delay the treatment. Often Endodontic intervention is required for a favorable result

2.HISTORY OF PERIODONTAL DISEASE

History of periodontal disease in time can cause gingival recession, which can be present as dentin hypersensitivity on the exposed root ends. Exposed root ends can be quite sensitive.

It is very important to halt the progression of any Gingival or Periodontal disease before any tooth preparation and impression procedures are attempted.

Nowadays some clinicians prefer to give long term Provisional crowns in cases of gingival inflammation to improve the condition of the gingiva before any definitive treatment is performed.

 3.History of parafunctional habits

It is of great importance to determine the presence of Bruxism or clenching before beginning any restorative treatment. Abnormal forces generated during Para function habit generated high stress, which can impair the ability of pulp to recover from trauma of tooth preparation. This can lead to hypersensitivity of the teeth.

4.OCCLUSAL DISTURBANCES

Premature contacts and occlusal interferences are one of the primary causes for hypersensitivity. Occlusal harmony should be restored before beginning of any restorative treatment. According to Garone Filho the most common etiological factor related to clinical manifestations of dentine hypersensitivity is the abfraction caused by occlusal overload. The premolars are the more affected teeth and, in almost all of the cases of dentine hypersensitivity, there is an occlusal component. Thus, occlusal adjustment should be associated to any kind of desensitizing agent selected for the treatment of hypersensitivity

5. History of trauma

Any trauma caused by injuries can have a long-term impact on the pulpal health of the effected teeth. Traumatized teeth show high incidence of root resorption. This makes them highly susceptible to hypersensitivity.

Every effort should be made by the clinician to properly evaluate these conditions and ascertain the prognosis of the teeth to be restored. If needed Endodontic and Periodontal treatment should be initiated before any tooth preparation begins.

It has shown to be beneficial to place the patient on 0.12 percent chlorhexidine gluconate rinses for a period of two weeks prior to tooth preparation. Sorenson et al. has shown it reduces gingival inflammation around the teeth to be prepared and provide a health-working environment.

CLINICAL PROCEDURES

TOOTH PREPARATION

Tooth preparation although overlooked many a times remains one of the integral part of reducing post cementation and post operative hypersensitivity.

Tooth perceives any preparation, as trauma and clinician should always evaluate the ability of the pulp to recover from this trauma. Following steps ensure in reducing hypersensitivity:

1. Adequate chair side time is required for producing fundamentally sound preparation designs. Unhurried preparation will cause minimum overheating of the pulp which is one the main cause of postoperative hypersensitivity.

2. Use of copious amount of water is required throughout the preparation. A soft touch by the clinician and avoiding any bur drag during the procedure minimizes the heating of dentin and pulp.

3. New burs are a great aid to the clinician as they ensure a cleaner cut and minimum amount of pressure during the preparation. Generation of heat is also minimal when new burs are used.

4. Repeated drying can have a adverse effect on teeth resulting in hypersensitivity. Teeth should only be dried when evaluating Margin finish lines, impressions and cementation. One should always avoid desiccation of the dentin.

5. Over reduction of the tooth can result in post cementation hypersensitivity and it should be avoided.

6. The margin of the preparation should be smooth and all unsupported enamel should be removed to avoid post- operative hypersensitivity.

7. Good finishing of the prepared surface of the crown will ensure proper seating of the crown onto the die and on the tooth thus ensuring properly sealed margins.

8. Furcation areas should be flooted during the preparation.

OCCLUDING THE EXPOSED DENTIN

Pulp protection is extremely important in the successful management of crown and bridge cases. Sealing the tooth immediately after preparation prevents many problems associated with pulp pathology caused by microbes invading the pulp through dentinal tubules exposed during tooth preparation."

There are Dentin sealers available, which occlude the exposed dentinal tubules and decrease the permeability of the dentin. This can significantly reduce postoperative hypersensitivity.

SUPERSEAL

  Super Seal is an oxalic acid potassium salt with a 3-way action.

*It forms oxalate crystals on the dentine surface.
*It blocks the dentinal tubules.
*Potassium ions penetrate pulp to deactivate dental nerves.

Super Seal is a unique formula that removes the smear layer, seals the tubules and desensitizes in one step. Super Seal reacts with the calcium hydroxyl apatite to form a fine granular calcium oxalate precipitate within seconds both within the dentinal tubules and on the surfaces of the vital dentin, enamel and cementum.

Nowadays one step self etching adhesives are available and they have been used for sealing the exposed dentine. Some studies have not found them effective in decreasing permeability of the dentine and they should not be used.

Impressions

-The use of retraction agents before impression procedures is almost always needed. Most of these agents have a low ph and can have a caustic effect on the surface of the prepared teeth and may result in hypersensitivity. Following points should be remembered when using them:

1. Retraction agents should be used in minimum quantity required for an effective retraction.

2.They should not be in contact with the tooth for a long time.

3.Thorough clean up of these agents is highly essential to avoid postoperative hypersensitivity.

-It is advisable to thoroughly evaluate the finish line. Any Debris and unsupported margin should be removed as they are potential cause of leaking margins.

- If there are slight tears, a small bubble, or an incorporation of a foreign particle in the impression, it is very easy to make a second single tooth impression of that particular preparation. This can be done with a copper band or modified stock tray technique (fig. 3). This second impression will then give the laboratory technician a perfect margin for the fabrication of that particular crown or retainer.

Provisional crown

Provisional crowns are an important treatment modality in helping the tooth from recovering from the trauma of tooth preparation.

-Provisional crown should have good marginal adaptation and fit thus preventing any hypersensitivity from micro-leakage.

-Provisional crowns should be highly polished and smooth to ensure that they remain plaque free. Retained plaque on the provisional restorations lead to marginal gingivitis and gingival recession that can result in post-operative hypersensitivity.

MARGINS

Some authors have concluded that relining the provisional crown can have a long term effect on its stability in the mouth thus reducing hypersensitivity.

Most of the provisional crown materials show some amount of polymerizing shrinkage upon setting. This can lead to open margins.  It is advisable to apply a second mix of the provisional material on the margin of the crown and reseat it over the die or the prepared tooth depending on the type of material used.

All occlusal contacts should be thoroughly evaluated and occlusal interference should be removed.

Eugenol free Zinc oxide cements for provisional cementation shows high resistance to dissolution around the margins by oral fluids then conventional Zinc oxide- Eugenol cements. 

TRY IN AND CEMENTATION OF THE CROWN

Seating of the crown

The final crown should be perfectly fitting on the tooth with perfectly sealed margins.

The fit of the crown should be evaluated over the die and the tooth. The fitting surfaces are coated with liquid disclosing agents and marked areas should be grinded and adjusted to achieve complete seating of the crown.

Air abrading

Thorough cleaning of the inside surface of the crown and air abrading the fitting surface of the crown should be done with 50-micron silica. This ensures better retention of the crown thus help in eliminating hypersensitivity.

This also removes the glaze from the margin of the porcelain crown, which now can be better adhered to the luting agent.

Occlusion

Occlusion should be thoroughly evaluated and adjusted.

Removing provisional cement

Remnants of provisional cement should be thoroughly removed with the help of pumice slurry. The teeth should be rinsed and left in moist state avoiding any salivary contamination. Teeth at this stage should never be desiccated and should be only light dried before cementation.

Final Cementation

Currently the clinician can choose between Adhesive and Frictive, conventional cements. Some of the all-ceramic systems require the use of Resin-luting agents bonded to the dentin and the enamel. There has been reported hypersensitivity after their use. This is due to the fact that Dentin has to etched with acid prior to the final cementation of the crown.

Post operative hypersensitivity has been associated with Glass Ionomer cements. However clinical trials by Rossential have not supported this view. Post cementation hypersensitivity with Glass Ionomer cements has been found to be due to improper manipulation of the material. Early contamination with saliva and moisture is associated with microleakage of the margins and bacterial contamination and this may result in Hypersensitivity.

It is highly essential to follow the manufacturer’s instruction properly and this can significantly reduce any post operative complications.

POST OPERATIVE PROCEDURES

Procedures for reducing post operative hypersensitivity can be considered as follows:

Desensitizing the nerve: With help of Potassium nitrate Hypersensitivity

Covering the dentinal tubules:

A.                       Periodontal surgery grafting

B.                       Composite/ Glass Ionomer restoration

C.                       Crown placement

D.                       Plug (scleroses) the dentinal tubules:

1.                         With Ions/salts:

a.                        Stannous fluoride

b.                        Sodium fluoride/ Stannous fluoride combination

c.                        Potassium oxalate

d.                        Ferrous oxide

e.                        Strontium chloride

f.                         In combination with an adhesive

2.                         Precipitates- Proteins/amino acids

               a. Gluteraldehyde

3.                         Resins

a.                                                       Dentin sealers

b.                                                       Methyl methacrylate

 E. Lasers:     Lasers have been found to be quite effective in treating  hypersensitivity. Both Red and Infrared lasers have been quite effective.

Conclusion

It is impossible to prevent all hypersensitivity when teeth are prepared to receive some type of full or partial coverage restorations. If attention has been paid to each of the steps involved from diagnosis to definitive cementation of the crown, hypersensitivity can be greatly minimized.

It is important to remember that even though we as clinicians are meticulous in our preparation, impression, provisional and placement procedures, these are traumatic events to the tooth

~DR SUMIT DUBEY~ New Delhi