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Compendium

March 2010, Volume 31, Issue 2
Published by AEGIS Communications


Provisional Materials: Improving the Predictability

William C. Strupp Jr, DDS, AFAACD

A ppropriate provisional restorations can simplify the management and increase the predictability of indirect restorative dentistry from six distinct perspectives, each with specific benefits for the dentist and patient:

  • Precise Maintenance of Abutment Tooth Position. This can eliminate occlusal and proximal adjustments of the final restorations. Supraeruption and drifting of abutment teeth translates into excessive chairtime to adjust contacts and occlusion in the final case. Patients may lose confidence in their dentists when their new dentistry is being excessively ground so as to destroy the normal anatomic shape of the restoration.
  • Contamination Protection for the Substrate. This keeps the substrate—to which bonding or cementing will occur—pristine in color and free of chemical contaminants that can inhibit the setting of cements. In addition, it prevents superficial decay of the prepared tooth surface, which robs the substrate of valuable minerals required in the bonding process. Decay also opens tubules to microbial invasion and causes discomfort for the patient.1 Most postoperative sensitivity can be avoided if the dentin is protected during the provisional phase.
  • Producing Soft-Tissue Health. This will facilitate the placement of the final restoration into a dry sulcus instead of in a blood-contaminated field of treatment, thus minimizing the time required and failure potential for biologically acceptable cementation. Contamination can lead to increased microleakage and sensitivity as well as pulpal and gingival inflammation.
  • Assuring Pulp Health. This results when microbes are denied access to opened tubules from the process of tooth preparation. Statistically, more than 10% of teeth treated with crown and bridge are at risk of endodontic treatment. In the author’s experience, well-adapted and well-placed provisional restorations help contribute to pulp health and result in less than 0.1% pulpal death following crown-and-bridge treatment.
  • Improving Diagnostics in Treatment Assessment and Desired Cosmetics Outcome. When provisional restorations are made in the same form and function as the final restorations, predictable treatment is easier. Good cosmetics with provisionals drive the laboratory toward excellence in the final case and allow patients to show their friends and relatives a preview.
  • Practice Growth and Profitability. This invariably occurs when patients are happy with their provisional restorations from a cosmetic perspective, free of discomfort, and eager to send their friends and relatives to see a dentist who truly has the patient’s best interest at heart.

In the author’s personal experience, provisional restorations play a significant role in the success or failure of indirect restorative dentistry. Poor provisional restorations can lead to failures in gingival health, pulpal health, and occlusion. The gold standard for provisional restorations that meet the above criteria involves provisional restorations that are made to fit perfectly using an indirect technique, can be polished to an excellent level to avoid plaque retention, are easily cleaned, can be cemented with an antimicrobial provisional cement that is relatively insoluble and yet allows easy removal, will support occlusal loading without excessive wear, and are formed like the desired shape of the final restorations.

Materials Used for Fabricating Provisionals

Five categories of materials are used predominately for fabricating provisionals. Each of these materials has advantages and disadvantages. Detailed comparisons of physical and chemical properties for the materials used for provisional restorations are beyond this article’s scope but are available through a review of the pertinent literature and textbooks. The five categories are as follows:

Chemically Activated Bis-acryl

  • Very inflexible material and therefore not suitable for cementation with a polycarboxylate cement. (It is this author’s preferred provisional cement because of its rigidity on setting, antimicrobial properties, and lower solubility compared with other temporary cements.) Must be cemented with weak, soluble provisional cement in order to remove provisionals.
  • Brittle and prone to fracture under occlusal loads.
  • Excellent polish.
  • Difficult to create perfect fit at the margin due to fracture and chipping on thin areas.
  • Used most frequently for direct shrink-wrap technique. This is the most commonly used technique for making provisionals for veneers. A polyvinyl siloxane impression of the wax-up is used. This carrier is filled with bis-acryl, placed in the mouth over the preparations, and allowed to set.
  • Maintains occlusion due to wear resistance.
  • Excellent for long-term provisionals due to color stability.

Light-Activated Resin Composite

  • Very inflexible material and therefore not suitable for cementation with polycarboxylate cements.
  • Brittle and prone to fracture under occlusal loads.
  • Difficult to create perfect fit at the margin due to fracture and chipping on thin areas.
  • Excellent polish.
  • Maintains occlusion due to wear resistance.
  • Excellent for long-term provisionals due to color stability.

Heat-Activated Polymethyl Methacrylate (Laboratory-Processed)

  • Very inflexible material and therefore not suitable for cementation with polycarboxylate cements.
  • Easy to create perfect fit at the margin, provided they are relined using a direct or indirect technique.
  • Excellent polish.
  • Maintains occlusion due to wear resistance.
  • Excellent for long-term provisionals due to color stability.

Chemically Activated Polyethyl Methacrylate

  • Very flexible material and therefore suitable for cementation with polycarboxylate cements.
  • Easy to create perfect fit at the margin.
  • Excellent polish.
  • Supports occlusion fairly well.
  • Fair for long-term provisionals due to color stability.

Chemically Activated Polymethyl Methacrylate

  • Very flexible material and therefore suitable for cementation with polycarboxylate cements.
  • Easy to create perfect fit at the margin.
  • Excellent polish.
  • Supports occlusion fairly well.
  • Fair for long-term provisionals due to color stability.

The choice for clinical use of these materials is influenced by the dentist’s need or perceived need for flexibility, strength, color stability, marginal accuracy, ease of use, patient comfort/satisfaction, cost, and surface finish. Regardless of the material chosen, the reason for choosing one of these products, or the technique used to fabricate the provisional, a high-quality provisional restoration is essential for fabricating a successful definitive restoration.2 The importance of provisionals in achieving success with the final restoration in cosmetic dentistry cannot be understated.3

Many long-term problems are created by providing patients with provisional restorations that microleak profusely. These restorations result when a direct, noncemented (shrink-wrapped) provisional is used. They also occur with directly or indirectly fabricated provisional restorations that are cemented with acid-soluble cements that wash out in a few days. ZOE-containing provisional cements compromise the bond strength of resin composite cement.4 Tissue and pulpal infections; demineralization and contamination/darkening of the substrate caused by the products of microleakage; microbial activity; and oral fluid under such restorations invariably leads to blood contamination of cement, postoperative sensitivity, endodontic issues, debonding problems, discoloration under the final restoration, and most importantly angry patients who do not pay their bills or do not actively refer their friends and relatives to the practice.

In 1987, Farhad Vahidi stated the case quite succinctly, “The utilization of properly fabricated provisional prosthodontic appliances will permit a higher rate of success of the definitive treatment. This phase of restorative treatment should not be merely considered a temporary treatment but as a template for the ensuing prosthesis. The information that is obtained in this phase of treatment will reduce the problems that may be encountered in the definitive treatment.”5

The most important requirement for an interim crown is suitable marginal adaptation.6 If an indirect technique is used to fabricate provisionals by making a vinyl polysiloxane impression immediately after the master impression is removed from the mouth, then multiple pours can be made so that several models can be used to create precise marginal fit. Making the provisional in the laboratory takes less out of a patient and improves the experience. Less stress for the patient, less damage to intraoral tissues, and better marginal accuracy mandates the use of an indirect technique when fabricating provisionals. The indirect method has been found to be the most accurate and the least time consuming.7

Likewise, placement with antimicrobial polycarboxylate cement protects the substrate and prevents lost provisionals that might allow immediate drifting and substrate contamination issues to occur.

Direct shrink-wrap techniques often allow microbial growth under provisionals that smell like “dirty socks” when they are removed. Microbial growth, byproducts of such growth, and the immune response promulgated often cause degradation of interdental papillae, growth of granulation tissue, infusion of microbes into patently open dentinal tubules, and substrate contamination that compromises both color and bonding. Such conditions result in postoperative sensitivity, more difficulty in anesthetizing the patient, and the entire host of other problems related to microbial contamination of the substrate.

The provisional restoration is extremely important to the success of the restorative case. In the author’s opinion, the most predictable provisional that can be made with the least effort and cost while fulfilling the need for cosmetics, flexibility to microfracture cement for easy removal, and occlusal support is chemically activated polymethyl methacrylate fabricated using an indirect technique from a vinyl polysiloxane impression and cemented with polycarboxylate. Although this material has a negative color shift in the long term, it is color stable and esthetically pleasing to virtually every patient for the short term.

References

1. Brännström M. Reducing the risk of sensitivity and pulpal complications after the placement of crowns and fixed partial dentures. Quintessence Int. 1996;27(10):673-678.

2. Hammond BD, Cooper JR 3rd, Lazarchik DA. Predictable repair of provisional restorations. J Esthet Restor Dent. 2009;21(1): 19-24.

3. Rossein K. Provisionalization: the key to cosmetic and restorative success. Compend Contin Educ Dent. 1995;16(7):684-688.

4. Carvalho CN, de Oliveira Bauer JR, Loguercio AD, et al. Effect of ZOE temporary restoration on resin-dentin bond strength using different adhesive strategies. J Esthet Restor Dent. 2007;19(3):144-153.

5. Vahidi F. The provisional restoration. Dent Clin North Am. 1987;31(3):363-381.

6. Tjan AH, Castelnuovo J, Shiotsu G. Marginal fidelity of crowns fabricated from six proprietary provisional materials. J Prosthet Dent. 1997;77(5): 482-485.

7. Small BW. Indirect provisional restorations. Gen Dent. 1999;47(2): 140-142.

About the Author

William C. Strupp Jr, DDS, AFAACD
Founder
William C. Strupp Postgraduate School of Dentistry
Clearwater, Florida

Private Practice
Clearwater, Florida


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