Perhaps one of the most frustrating situations in the dental office is to craft an aesthetic restoration and have the patient call the office the following day to complain that the tooth is sensitive. To the patient, it does not matter how beautiful the restoration looks if he or she cannot chew on it. What causes postoperative sensitivity and what can be done to reduce its likelihood?
There are many theories as to the causes of postoperative sensitivity. The most widely accepted theory is the hydrodynamic theory,1 which states that fluid flow within the dentinal tubules can elicit a painful stimulus. Open dentinal tubules created during the bonding procedure that are left unsealed following restorative procedures can cause sensitivity.2 Desiccated dentin has long been suggested as a cause for pulpal damage.3 The bacterial invasion theory attributes dentinal pain to the introduction of bacteria within the dentinal tubules.4 Microleakage can allow bacteria from the oral environment to enter the tooth.5 Excessive heat during the preparation and restoration of the tooth can cause pulpal irritation.6 Polymerization shrinkage stress, especially in class I posterior composite restorations with a low exposed surface-to-restoration volume ratio, can result in debonding between the dentin pulpal floor and the restoration, resulting in a fluid-filled gap.7,8 Inadequate polymerization of the composite resin restoration can contribute to problematic teeth.9 Restorations left high in occlusal contact with the opposing teeth following restorative procedures can create sensitive teeth.10
|Figure 1a. Magnification optics in use.|
|Figure 1b. Perspective view without magnification optics.|
|Figure 1c. Perspective view with magnification optics.|
With the technique sensitivity of today’s aesthetic techniques, proper visualization during the dental procedure is imperative. The level of treatment provided is dependent upon the ability to see the treatment area. Attention to detail is paramount. With the use of magnified optical systems decay, margins and voids within a restoration are more easily viewed, allowing for improved treatment and increased confidence (Figures 1a to 1c).
(2) Glass Ionomer
The placement of a glass ionomer liner in a deeper-than-ideal preparation prior to the bonding procedure will dramatically reduce postoperative sensitivity. The dentinal tubules have not been opened when an etchant is not used, reducing the risk of incomplete sealing. Published studies have demonstrated decreased occurrence of postoperative sensitivity with posterior composite restorations lined with resin-modified glass ionomer materials.11 With all the complexities of dentin bonding techniques and the variability of deep dentin, this will predictably reduce sensitivity.
|Figure 2a. Tooth preparation deeper than ideal depth.||Figure 2b. Placement of resin-modified glass ionomer liner to cover deep dentin.|
|Figure 3a. Placement of convenient, capsule-dispensed, resin-modified glass ionomer base in deep preparation.|
|Figure 3b. Over-filled resin-modified glass ionomer base following light polymerization.|
|Figure 3c. Reprepared tooth to ideal depth.|
When placing a liner (eg, Vitrabond, 3M ESPE) under moderately deep composite restorations, rinse the preparation thoroughly and remove excess moisture prior to application (Figures 2a and 2b). In deeper and very extensive composite restorations, a resin-modified glass ionomer base (eg, Fuji II LC, GC America) is a simple and easy method to build the tooth to ideal depth prior to placement of the composite restoration. Place the material into the tooth in one layer, light-cure, and then re-prepare the tooth to ideal size prior to bonding procedures and placement of the composite (Figures 3a to 3c).
|Figure 4. Photomicrograph of occluded dentinal tubules using GLUMA.|
The use of a gluteraldehyde- and-HEMA-containing desensitizer occludes dentinal tubules, disinfects the tooth surface, and enhances the dentinal bond strength to many dentinal adhesives12 (Figure 4). If using the total-etch technique, place the desensitizer (eg, Gluma, Heraeus Kulzer) inside the restoration after application and rinsing of the etchant but prior to placement of the bonding agent and composite material.
(4) Self-Etching Dentin Primer
|Figure 5a. Exposing cross-section of enamel rods.||Figure 5b. Preparation of enamel rods.|
This type of dentinal adhesive seems to be the trend of the future due to decreased technique sensitivity and reportedly decreased postoperative sensitivity.13 There is no more question as to how wet is moist? The acidic monomer penetrates the dentin, never leaving the tubules open, and is self-limiting, preventing excess demineralization. Care is needed to ensure adequate enamel etching. Be certain to prepare the enamel margins with a diamond bur to ensure proper bond strengths at the vulnerable marginal area (Figures 5a and 5b).
(5) Separate Air Syringe
|Figure 6a. Use of tooth dryer to provide warm, moisture-free air.||Figure 6b. Separate air-only syringe with additional air/water syringe.|
Combination air/water syringes often leak water when the air button is depressed, contaminating the bond and reducing effective bonding. This often-overlooked source of problems can be easily remedied by installing a separate, air-only syringe (eg, A-dec) or air dryer (eg, A-dec) (Figures 6a and 6b). Another method to prevent moisture contamination is to first depress the air button on the syringe away from the tooth and leave the button depressed as the syringe is brought to the mouth. The water content of the spray seems to be highest when the button is first depressed.
(6) Don’t Over-Etch the Dentin
When using systems with conventional etchants and dentin bonding agents (often referred to as the total-etch dentin bonding technique), do not leave the etchant on the dentin for more than 5 seconds. Etchant should be applied first to the enamel for 15 seconds (Figure 7), then applied to the remaining dentin tooth structure for 5 seconds. In this way, the enamel has been in contact with the 37% phosphoric acid for a total of 20 seconds, and the dentin has been in contact with the etchant for 5 seconds. Increased exposure to etchant results in a deeper layer of demineralization and more difficulty in obtaining an adequately intact hybrid layer.14 Be certain to wash the etchant off the tooth thoroughly for at least 5 to 10 seconds. Do not overly dry or desiccate the dentin.
(7) Check Light Output Regularly
|Figure 7. Etching of enamel only for 15 seconds prior to total etching of remaining tooth preparation for additional 5 seconds.|
|Figure 8a. Measurement of curing light output.||Figure 8b. Light output log.|
Proper curing-light output is critical for thorough polymerization.15 Bulb degradation cannot be evaluated without the use of a light meter. Light outputs of more than 400 mW/cm2 are necessary for composite to polymerize adequately within the tooth in the recommended exposure times. Ideally, light outputs of 800 to 1,200 mW/cm2 ensure proper polymerization. Use a high-output curing light (Demetron 501, Kerr). Have your staff keep a log with the light outputs recorded (Figures 8a and 8b). Always have a replacement bulb available for each type of unit in the office.
(8) Don’t Over Heat or Over Dry the Tooth During Preparation and Restoration
|Figure 9a. Use of LED light.||Figure 9b. Focused LED curing light spectral output.|
Use adequate water cooling during tooth preparation. In deeper preparations, carefully remove all the decay using light pressure. Be careful about producing excess heat when curing deep liners with PAC lights. LED curing lights produce light outputs without extraneous longer wavelengths of light that produce heat energy (eg, LEDemetron, Dem-etron) (Figures 9a and 9b).
(9) Use Appropriate Techniques to Reduce Polymerization Shrinkage Stress
Use a low-shrinkage composite. Composites are being introduced that shrink less upon polymerization (eg, Filtek Supreme, 3M ESPE; Premise, Kerr; Aelite LS, Bisco), and others have been available for years (eg, Heliomolar, Ivoclar Vivadent).
|Figure 10a. Reducing polymerization shrinkage stress using combined techniques, placing flowable composite resin and curing thoroughly. Figure 10b. Placement of first incremental cured through tooth structure. Figure 10c. Placement of final incremental cured through tooth structure with 2 simultaneous lights. Figure 10d. Final light-curing from occlusal.|
Learn how to direct composite placement and light polymerization properly to minimize the effects of shrinkage stress. The most accepted and practiced method of controlling stress is incremental buildup.16 Bulk placement of composite utilizing multiple curing lights curing through tooth structure to direct the polymerization has been advocated.17 Preliminary curing of the composite to a stage prior to the gel state and allowing for slow formation of the polymer chains prior to final curing has been demonstrated to reduce stress.18-20 Incremental buildup, curing through tooth structure, and using multiple lights utilize advantages of several of the techniques (Figures 10a to 10d).
|Figure 11. Excursive movements marked with articulating paper.|
Patients who have had their mouths open wide for procedures may close differently when checking the occlusion due to muscular and TMJ involvement. Check occlusion carefully, including all excursive movements, with the patient fully upright before dismissing them, and encourage them to call your office immediately if the bite feels improper after the duration of anesthesia (Figure 11).
When given the choice, most patients select aesthetic restorations in their mouths. Yet, there has been a significant increase in postoperative sensitivity with the placement of direct posterior composites. There is not a single simple solution to the problem, but with attention to detail and the use of the proper materials, the occurrence of sensitivity can be significantly reduced.
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13. Denehy G, Cob D, Bouschlicher M, et al. Two-year clinical evaluation of a self-etching primer/adhesive in posterior composite. J Dent Res. 2002;81:A-80. Abstract 434.
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17. Belvedere PC. Controlling shrinkage using TEP: trans-enamel polymerization. Dent Today. 1995;14:92-97.
18. Lim BS, Ferracane JL, Sakaguchi RI, et al. Reduction of polymerization contraction stress for dental composites by two-step light activation. Dent Mater. 2002;18:436-444.
19. Bouschlicher MR, Rueggeberg FA. Effect of ramped light intensity on polymerization force and conversion in a photoactivated composite. J Esthet Dent. 2000;12:328-339.
20. Ernst CP, Brand N, Frommator U, et al. Reduction of polymerization shrinkage stress and marginal microleakage using soft-start polymerization. J Esthet Restor Dent. 2003;15:93-103.
Dr. Ward maintains a private practice in Columbus, Ohio, and is a clinical instructor in the department of restorative and prosthetic dentistry at The Ohio State University College of Dentistry. He is a diplomate of the American Board of Aesthetics, a member of the American Society for Dental Aesthetics, and serves as editor of the ASDA Journal. He has served as examiner of the postgraduate programs in aesthetic dentistry (continuing dental education) at the University of Minnesota, SUNY Buffalo, and the University of Florida. He has lectured internationally and can be reached at (614) 430-8990 or email@example.com.