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Provisional restorations: an overview of techniques and materials.

Provisional restorations play a critical role in the successful treatment of the prosthodontic patient. An interim restoration that meets the functional and aesthetic requirements of the patient can mean the difference between success and failure of a treatment plan. Clinicians have often made the mistake of regarding the provisional as being merely "temporary" and thus do not devote adequate time and effort to this phase of treatment. This may result in the fabrication and cementation of an interim restoration, which is inadequate functionally and/or morphologically. According to Shillingburg, (1) aside from meeting the individual patient's aesthetic desires, the restorations should also meet the following requirements:

1. Provide pulpal protection.

2. Provide positional stability.

3. Provide the patient with the proper occlusal function.

4. Be easily cleanable.

5. Be strong and retentive.

6. Be aesthetically pleasing.

7. Margins should not impinge upon the gingival tissues.

Campagni and Caponigro (2) accurately describe the requirements of a successful provisional as one that mimics the planned restoration(s) in occlusal and axial morphology as well as aesthetics, while fulfilling its requirements for maintaining tooth position and protecting the tooth structure during function.

Numerous techniques and materials for fabrication of single-unit or multiple-unit provisional restorations have been described in the literature to meet these requirements. This article seeks to provide the clinician with an overview of various techniques and materials which have proven to be useful and thus have endured over the years.

The Direct Technique

This technique utilizes a prefabricated stent or matrix filled with the practitioner's choice of provisional material, which is placed directly onto the patient's prepared teeth. After initial polymerization, the material/matrix assembly is removed from the mouth, trimmed, and polished.

Kaiser and Cavazos (3) describe the following technique:

1. On the patient's diagnostic cast, wax in any missing teeth.

2. Duplicate the cast and fabricate a matrix from a material of the clinician's choosing.

3. Prepare the teeth.

4. Lubricate the teeth.

5. Place autopolymerizing resin into the matrix and seat onto the prepared teeth. Use a pumping motion to ensure that the provisional restoration will not get locked into any undercuts.

6. After initial set, remove the matrix from the mouth and allow the provisional restoration to completely polymerize.

7. Trim, contour, and polish.

Nayyar and Edwards (4) also describe a direct technique for use with a single unit using a commercially available metal crown in which the crown is relined directly on the tooth with autopolymerizing resin :

1. Measure the mesial/distal width of the tooth to be prepared.

2. Pick out a corresponding commercially available metal provisional crown.

3. Seat the crown, trim any excess material below the margin to the proposed finish line.

4. After preparation, lubricate the prepared tooth and coat with cavity varnish.

5. Pour acrylic resin into the crown, seat it and have the patient bite into the centric occlusion.

6. After initial set, lift the crown 3 mm and reseat. Repeat this action three or four times.

7. Remove, trim, and contour after the acrylic resin reaches final set.

One of the disadvantages of using a commercially available metal provisional crown is that the patient may complain about metallic taste when chewing food. Polycarbonate crowns may also be used in the preparation of an anterior tooth for a single-unit restoration. However, the aesthetic demands of patients often prevent their use in this region of the mouth.

Christensen (5) describes another method for direct fabrication of a single-unit using wax as a stent:

1. Fabricate a baseplate wax impression of the tooth to be prepared plus one to two teeth mesial and distal.

2. Prepare the tooth.

3. Place acrylic resin in the wax impression and seat it onto the lubricated prepared tooth.

4. As polymerization occurs, pump the wax matrix up and down a few times.

5. After initial polymerization, remove the wax matrix from the mouth and allow it to completely polymerize extraorally.

6. Trim and polish.

Psichogios et al (6) describe a direct technique for provisionalizing multiple single-units and three- or four-unit fixed partial dentures:

1. Fabricate a diagnostic waxing.

2. Construct a dual arch custom impression tray.

3. Take an impression using an addition silicone.

4. Trim the impression material 3-4 mm apical to the gingival margins of the diagnostic waxing and only include cusp tips or incisal edges of the opposing arch.

5. Prepare the teeth and coat with a lubricant.

6. Use a BisGMA restorative material to fill the impression.

7. Have the patient close into the custom tray.

8. Remove the tray after two minutes.

9. Bench polymerize for another two minutes.

10. Trim and polish.

Many clinicians are familiar with and readily employ these direct techniques. The matrix material used may differ from clinician to clinician, but the general techniques are similar. While the direct technique reduces chair time, it has two major disadvantages:

* Evidence exists indicating that an adverse pulpal reaction occurs caused by the free monomer and heat generated by the polymerization reaction.

* Distortion can occur due to the "pumping" of the matrix on and off during polymerization of the resin. (7)

Despite these disadvantages, the direct technique continues to be a very popular and highly utilized method for provisional fabrication. When performed properly, this method can produce very aesthetic and functional provisional restorations.

Indirect Method

This method of provisional restoration fabrication, which is taught in most dental schools, has several advantages:

* The pulp is protected due to polymerization occurring on a stone cast. Shillingburg (1) states that any vital tooth that is being relined should be done so via the indirect method because of this exothermic heat increase.

* Moulding (8) found that the indirect method had significantly less marginal discrepancy than the direct technique that utilizes a pumping motion. Crispin et al (9) found that marginal fit could be improved by 70% using the indirect method to fabricate provisional restorations.

* Auxiliaries are able to fabricate the majority of the provisional restorations in the lab, leaving the practitioner free to treat other patients.

The techniques described by various authors for fabricating provisional restorations via the indirect method are very similar. Differences occur in the acrylic resin used and whether pressure pots are utilized. Chee et al (10) found that pressure curing polymethyl methacrylates reduced porosity and increased transverse strength when compared with the technique of bench curing. The indirect technique is described as follows:

1. Prior to preparing teeth, form a matrix on diagnostic casts.

2. Prepare the teeth.

3. Take an irreversible hydrocolloid impression of prepared teeth. If two retraction cords are used, make the alginate impression after placement of the first cord.

4. Pour impression up with quick-set plaster.

5. Place the matrix onto the stone cast to ensure proper fit. Lubricate the stone model with a tin foil substitute and then add acrylic resin. For optimal aesthetics, place an incisal shade of resin into the matrix and feather the resin up the facial side of the teeth. Then add the body shade of resin.

6. Rubber band the matrix to the stone cast to ensure complete seating and place in a pressure pot with hot water at 20 psi for five minutes.

7. Remove and mark the gingival margin on the provisional restoration with a sharp lead pencil.

8. Trim and contour.

9. Polish the restoration with pumice on a rag wheel, followed by a diamond stone on a rag wheel.

For provisional restoration of a fixed partial denture, it is recommended that the practitioner place a ball of completely polymerized acrylic resin into the pontic space. (The ball should fill at least 50% of the pontic space). This will help offset the significant amount of shrinkage that frequently occurs in the pontic area to due to excessive bulk of material.

Davidoff (11) describes an indirect method that uses heat-polymerizing acrylic resin. In this method, all steps are similar to those described above, except that a heat-polymerizing acrylic resin is used. The filled matrix is placed on the cast and placed in a pressure pot at 250 degrees Celsius at 30 psi for 30 minutes. If required, a chairside reline with autopolymerizing acrylic resin can be performed. Although the indirect method has been shown to produce provisional restorations of superior strength and marginal integrity, few clinicians use the strictly indirect method.

Indirect/Direct Method

This is probably the most popular method used for the provisionalization of fixed partial dentures. It combines the advantages of both the direct and indirect methods thus capturing the best of both techniques. One of the main benefits of this technique is that the clinician must reline the prefabricated shell. Barghi and Simmons (12) showed that relining of provisional restorations fabricated via the direct method substantially improved marginal adaptation. Campagni and Caponigro (2) also list the following advantages for the indirect/direct method:

* Decreased chair time.

* Auxiliaries can fabricate the shell.

* The provisional restoration can be relined intraorally with the patient in centric occlusion, thereby minimizing the amount of occlusal adjustment necessary

Several techniques for this method of provisional fabrication are presented below.

Campagni and Caponigro (2) describe the following method:

1. Add a bulk of wax to the gingival area of the teeth to be prepped on casts. This ensures an adequate amount of provisional material in the marginal area.

2. Duplicate the cast.

3. Make a clear matrix.

4. Minimally prepare the teeth included in the provisional restorations. Reductions should be half that of actual preparations.

5. Gingival extensions should be 2 mm apical to the expected gingival finish line. This results in a 2 mm gingivectomy.

6. Place a tin foil substitute on the cast.

7. Methyl methacrylate is placed in the matrix. The matrix is then seated on the cast and the whole apparatus is placed into a pressure pot at 20 psi for five minutes.

8. The shell is trimmed slightly then tried in the patient's mouth after preparations have been completed.

9. Reline is accomplished using polyethyl methacrylate and a pumping motion.

10. Trim, contour, and cement the provisional restoration.

Christensen (5) also advocates using the above method with one slight variation. He suggests removing the shell at the first detection of exothermia and cooling it under running water. The shell is then replaced and a pumping motion is used until complete polymerization has taken place.

Chiche (13) describes the following technique:

1. A preformed shell is made in the lab and tried on the patient after preparations of the abutment teeth are completed.

2. Acrylic resin is added to the shell and then seated onto the preparations under occlusal pressure at the patient's vertical dimension of occlusion.

3. The shell is lifted 1-2 mm to prevent it from being locked into any undercuts below the margins.

4. Spray the abutment teeth with water to retard the heat generated during polymerization.

5. Reseat the shell.

6. When the bulk of material is at the doughy stage, remove the shell and lightly adapt a fresh mix of acrylic resin over the margins.

7. Quickly reseat the shell and have the patient gently close into centric occlusion.

8. Again lift the shell 1-2 mm so water can be sprayed onto the abutment teeth.

9. Reseat the shell. 10. Repeat this procedure three times until the acrylic resin is set.

11. Mark outer edge of margins with a pencil.

12. Trim, contour, and polish the provisional restoration.

Vahidi (14) advocates an indirect/direct method utilizing light cured composite resins for the shell and then relining on the tooth preparation with autopolymerizing acrylic resin:

1. Prepare the teeth on the cast.

2. Apply a thin coat of die isolation material to the cast (Visio-Gem die isolation material, ESPE Premier Dental Products, Norristown, PA).

3. Build up a core of body shade resin and then follow with a layer of incisal shade resin.

4. Light cure for 90 seconds.

5. Remove cured restoration, trim excess, and add to deficient areas.

6. Polish using pumice and composite polishing paste.

7. Complete intraoral tooth preparation and reline the provisional shell with autopolymerizing resin.

It is the clinician's responsibility to determine which of the three described techniques works best in his/her hands. Success by the standards established by Shillingburg (1) can be achieved by using any of the above techniques with proper training and adequate practice. If this high standard is met, the final prosthesis will have a greater chance of success. The dentist will know better how the patient will tolerate the final prosthesis. The provisional restoration is also used as an important diagnostic tool to determine the patient's aesthetic expectations.

Provisional Materials

Equally important as technique in provisional fabrication is the material the clinician employs in the technique. A clinician may choose from numerous materials. Oftentimes the choice depends on what works best in the clinician's hands. This is perhaps the most important characteristic when deciding upon the material to use, however, research has shown some materials to be superior to others. The remainder of this article focuses on a simple overview of some of today's most popular materials in use for provisional restoration fabrication. It should be noted that any brand names of material are listed for example purposes only.

Jet polymer comes in many different shades, which allows the clinician to obtain excellent aesthetic results. Wang et al (15) conducted a study that measured certain characteristics of the following provisional materials: PEMA, PMMA, Bis-GMA, light-cured composites, and polyvinyl methyl methacrylate. The authors found that Jet (PMMA) had the worst wear resistance of the materials, but had one of the highest transverse strength values. Due to its high exothermic heat, the authors of this article agree with others that PMMA should be used only in the indirect method, or in the fabrication of the shell for the indirect/direct method.

In their study, Wang et al (15) found that Snap was significantly less hard at one week than the PMMAs, but marginal fit was similar to Jet. The authors also found that Snap was not as color stable as the composite resins, but significantly more color stable than the PMMAs. Krug (16) stated that the PEMAs provided the clinician with more working time and induced less chemical and exothermic irritation to the pulp. He also stated that the PEMAs were less color stable than the PMMAs, but heat processing the resin at 135 degrees Fahrenheit for five minutes at 20-25 psi will alleviate the problem of hardness and color stability. Christensen (5) states that PEMA has a low cost and relatively good fit, however, the material should not be used for long span provisional restorations (insufficient strength) or left in the mouth for over 2 weeks (color instability). Tjan et al (17) found that Splintline[TM] (Lang Dental Mfg. Co. Inc, Wheeling IL.) had better marginal adaptation than that of PEMA.

Christensen (5) also lists cost as a disadvantage of the bisacryl composites. Wang et al (15) found in their study of six different materials that Protemp exhibited the least amount of temperature increase upon curing and, along with Alike[TM] (Coe Laboratories, Inc., Chicago) had the best marginal adaptation. Another advantage of this material is that light-cured composite can be added to correct any deficiencies and this can reduce potentially marginal porosity that is sometimes found with the use of autopolymerizing resins.(18)

The microfill resins are highly useful for inlays and onlays. Christensen (19) also promotes their use for certain veneer cases, but did not specify which cases are better suited for the microfill resins.

Summary

Three types of provisional restoration materials and techniques were described in this article. Many other methods and materials are available to the clinician. The material and technique of choice should be based not only on scientific evidence, but also by what works best in the hands of the individual clinician. The ultimate goal is to fabricate a provisional restoration that is aesthetic, functional, and similar in contour to what is desired in the final prosthesis. If the clinician is able to achieve this in the provisional stage, achieving success in the final prosthesis will be that much easier.

References

(1.) Shillingburg H Jr. Fundamentals of Fixed Prosthodontics Third Edition. Berlin, Germany: Quintessence Publishing Co. Inc.; 1997.

(2.) Campagni W, Caponigro C. Provisional restorations. CDA J. April 1988.

(3.) Kaiser D, Cavazos E. Temporization techniques in fixed prosthodontics. Dent Clin North Am. 1985;29 (2):403-412.

(4.) Nayyar A, Edwards W. Fabrication of a single posterior intermediate restoration. Dent Tech. 1978;39(6):688-691.

(5.) Christensen G. Provisional restorations for fixed prosthodontics. J Am Dent. 1996;127:249-252.

(6.) Psichogios P, Monaco E. Expedient direct approach for esthetic and functional provisional restorations. J Prosthet Dent. 2003;89:319-322.

(7.) Fisher D, Shillingburg H Jr, Dewhirst R. Indirect temporary restorations. J Am Dent. 1971;82:160-163.

(8.) Moulding M, Loney R. Marginal accuracy of provisional restorations fabricated by different techniques. Int J Prosthodon. 1994;7(5):468-472.

(9.) Crispin BS, Watson JF, Caputo AA. The marginal accuracy of treatment restorations: a comparative analysis. J Prosthet Dent. 1980;44:283-290.

(10.) Chee W, Donovan TE, Daftary F, Siu TM. The effect of vacuum-mixed autopolymerizing acrylic resins on porosity and transverse strength. J Prosthet Dent. 1988;60(4):517-519.

(11.) Davidoff R. Heat-processed acrylic resin provisional restorations: an in-office procedure. J Prosthet Dent. 1982;48(6):673-675.

(12.) Barghi N, Simmons EW. The marginal integrity of temporary resin crowns. J Prosthet Dent. 1976;36:274-277.

(13.) Chiche G. Improving marginal adaptation of provisional restorations. Quintessence Int. 1990;21 (4):325-329.

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

(15.) Wang R, Moore K, Goodacre C, Swartz M, Andres C. A comparison of resins for fabricating provisional fixed restorations. Int J Prosthodont. 1989;2(2):173-184.

(16.) Krug R. Temporary resin crowns and bridges. Dent Clin North Am. 1975;19(2):313-320.

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

(18.) Wood M, Halpern B, Lamb M. Visible light-cured composite resins: an alternative for anterior provisional restorations. J Prosthet Dent. 1984;51 (2):192-194.

(19.) Christensen G. The fastest and best provisional restorations. JADA 2003;134:637-639.

Polymethyl Methacrylate (PMMA)--Jet[R] (Lang Dental Mfg. Co. Inc.)

Advantages

* Good marginal fit, especially if the indirect technique is used.

* Polishes to a high shine.

* Very durable.

* Can achieve a high transverse strength, especially with use of a pressure pot during polymerization.

Disadvantages:

* High exothermic heat that can stress the pulp.

* PMMA exhibits low abrasion resistance.

* Acrylic resin monomer is toxic to the pulp.

* PMMA experiences a high volume of shrinkage (about 8%).

(Source: Shillingburg (1))

Polyethylmethacrylate--Snap[TM] (Parkell, Farmingdale, NY), Trim[R] II (Harry J. Bosworth Co., Skokie, IL)

Advantages

* Polishes to a good shine.

* Minimal exothermic heat increase.

* Good stain resistance.

* Low percentage shrinkage compared with PMMAs.

Disadvantages:

* PEMA exhibits low transverse strength compared to the PMMAs.

* Poor fracture toughness.

* Durability is less than that of the PMMAs.

(Source: Shillingburg (1))

Microfill Resin--Durafill VS[TM] (Heraeus Kulzer, Armonk, NY)

Advantages

* Light cured.

* Excellent polish results.

* Putty-like consistency makes them user friendly.

* Only a slight exothermic reaction.

Disadvantages:

* High cost.

* Brittleness limits use to single tooth restorations or to veneers.

(Source: Christensen (5,19))

CPT Thunberg graduated from the 1-Year Advanced Education in General Dentistry Program at Fort Carson, CO in 2003. He is presently serving his second tour in Iraq, assigned as the Regimental Dental Surgeon for the 3rd Armored Cavalry Regiment.

COL Schmitt is the prosthodontic mentor of the 1-Year Advanced Education in General Dentistry Program, Fort Carson, CO.

CPT Matthew S. Thunberg, DC, USA COL James K. Schmitt, DC, USA
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Author:Thunberg, Matthew S.; Schmitt, James K.
Publication:U.S. Army Medical Department Journal
Date:Jan 1, 2006
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