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Crown and Bridge Temporization Part 2: Provisional Cements
Gregori M. Kurtzman, DDS
The temporization of crown-and-bridge prosthetics requires both a material to fabricate the provisional restora- tions, and a material to lute the provisional restorations to the teeth or implants temporarily. Part 1 of this article addressed the materials available for fabrication of provisional restorations, the benefits and deficiencies of the different groups of provisional materials, and the indications when one may be selected over another. Part 2 of this article addresses the different provisional luting cements. It discusses when one cement may be a better choice over the others with respect to the length of time the provisional will be worn and the retentive demands of a particular preparation.
Selection of Provisional Cement
Several questions need to be asked when deciding which provisional cement should be selected, including:
- Does the cement contain eugenol, which may affect bonding a permanent restoration?
- Is the preparation retentive by design or will it require retention from the luting cement?
- How long will the provisional need to remain intraorally?
- Can the provisional restoration be removed and the remaining cement cleaned from the preparations surface easily?
- How is the provisional cement dispensed?
Frequently, fixed restorations are bonded to the prepared tooth and selection of the provisional cement can influence the quality and durability of the bond with the permanent restoration. The early provisional cements were manufactured from zinc oxide and eugenol. The benefit of these eugenol-containing cements was that eugenol acts as an obtundent to the pulp, “settling down” the tooth after preparation.1,2
Eugenol has been known to affect bonding quality, and numerous provisional cements exist that contain this oily substance. Inhibition of the setting reaction through the free-radical polymerization of the dental resins by eugenol has been reported.3-5 Additionally, the bond is affected as the eugenol penetrates the dentinal tubules and prevents resin penetration from the dentinal adhesive or luting material. Because eugenol is a water-insoluble oil it is not readily removed through rinsing or etching the tooth. Eugenol has not been reported to affect permanent cementation when a glass ionomer cement is used to lute the final restoration, and it does not affect zinc phosphate or polycarboxylate (eg, Durelon™, 3M ESPE, St. Paul, MN) retention. Another consideration is that an acrylic provisional may soften over time because of the eugenol in the provisional cement, leading to the possibility of early failure of the provisional.6 Manufacturers have recognized these problems and offer noneugenol-containing versions of their provisional cements; therefore, practitioners should check which version they are using.7,8
It is important for the provisional cement to provide good retention to the prepared tooth or implant and permit removal when required to place the permanent restoration or render soft/hard-tissue treatment to the area surrounding the prepared teeth. Preparations that are short occlusogingivally or have walls with significant convergence require a more retentive provisional cement to prevent premature dislodgement of the provisional. The rigidity of the provisional cement influences its retentive capabilities, with stiff-setting cements being more retentive then soft-setting cements. Splinted units will be more retentive then single units, and using a very rigid provisional cement may make removal of the provisional difficult and lead to fracture of the provisional on removal.
If the provisional is fabricated intraorally, it will have a tighter fit than a final prosthesis that was fabricated extraorally. Because intraoral fabrication is not usually done with a spacer present, no space is available to accommodate the cement between the preparation and the provisional. This can prove to be an issue during cementation of a provisional restoration. The author recommends painting the internal margins with the provisional cement, which then will spread over the axial walls as the provisional is seated. Care should be taken not to fill the provisional with cement because this may prevent full seating of the provisional and subsequent occlusal adjustments.
In many cases, the provisional is present intraorally for only a few weeks while the permanent restoration is fabricated. But, there are instances when the provisional needs to remain intraorally for extended periods of time, such as periodontal surgery for crown-lengthening or esthetic gingival correction, segmental provisionalization as part of full-mouth rehabilitation, and immediate implant provisionalization. A provisional cement that may be suitable for a 3-week period may not functional well when the provisional needs to be in function for months. Some permanent cements that do not chemically bond to tooth structure (ie, zinc phosphate or polycarboxlate cements) may be suitable for long-term provisional cementation or when more retention is required during the period that the provisional will need to be in function. For example, Durelon can be mixed using more liquid than powder, which will provide a weaker cement that is more retentive than conventional provisional cements but weaker than when mixed in the appropriate ratio for permanent cementation.
Provisional restorations may need to be removed and re-luted during treatment to permit ongoing treatment or impression-making. Thus, the cement must permit removal of the provisional restoration without damage to the restoration, and it needs to be easily removable from both the restoration’s interior and the preparation. Use of an intraoral sandblaster is an easy method for removing the remaining provisional cement from the preparation or the interior of the restoration before re-luting the provisional or cementing the final prosthesis. Use of an ultrasonic scaling instrument makes a good adjunct to removing the gross provisional cement from the preparation or abutment head and has been shown to aid in cleaning the interior of the provisional restoration before re-luting. If an intraoral sandblaster is not available, a pumice slurry and a prophylactic cup can be used to clean any remnants of provisional cement from the prepared tooth or abutment head.9-11
With regard to implant restorations, the final crowns may be luted with provisional cements to aid in the removal of the crown to allow accessing the fixation screw retaining the abutment head. This procedure may be necessary to treat screw loosening that may occur during function. Use of permanent cement to lute a crown onto an implant abutment results in a non-retrievable unit that will require sectioning of the crown to access the abutment head’s fixation screw. Typically, the gap between the crown and abutment head on implant restorations is smaller than what is found in crowns on natural teeth. Combined with a less convergent (less tapered) abutment head, this gap size yields a retentive crown that requires minimal retention from the luting material.12 Studies have reported on the properties of provisional cements when used to cement implant restorations. Retrievability of cemented implant fixed prosthetics using different provisional cements have been evaluated.13-16 It was found that provisional cements permit retrievability of the implant restoration, but it was reported that different cements have varying degrees of retrievability and retentive ability.17,18 Several implant-specific resin cements have been introduced to provide long-term luting, while permitting retrievability: Premier Implant Cement™ (Premier Products Co, Plymouth Meeting, PA), ImProv™ (Nobel Biocare USA LLC, Yorba Linda, CA), SensiTemp® Resin (Sultan Healthcare, Englewood, NJ), and Mizzy Resin Cement (Keystone Industries, Cherry Hill, NJ). It has been suggested by the manufacturers and supported in the literature that application of a thin coat of petroleum jelly to the interior of the crown before cementation with an implant-specific resin cements can improve retrievability.19
Classification of Provisional Cements
Provisional cements can be divided into two categories: eugenol-containing (Table 1) and non-eugenol–containing (also called eugenol-free) (Table 2). Additionally, as previously mentioned, there are non-traditional materials that can be used for provisional cementation (Table 3). These include calcium hydroxide cavity liners, such as Life Base Paste (Kerr Corp, Orange, CA), Dycal® and Prisma® VLC Dycal® (DENTSPLY Caulk, Milford, DE), Hydrox™ (Henry J. Bosworth Co, Skokie, IL), and Pulpdent® calcium hydroxide powder (Pulpdent Corp, Watertown, MA). These cavity liners, except for Prisma VLC Dycal, are self-curing materials that can be used when retention of the provisional does not need to be aided by the provisional cement and the provisional will be short-term (2 to 3 weeks). They are weak materials and can suffer from marginal washout, so they should be used with caution. Prisma VLC Dycal is a light-curable cavity liner that may not set fully if the provisional material is thick or dark in color. Similarly, it is contraindicated for temporary cementation of permanent restorations because setting of the material cannot be accomplished. IRM, although not intended for cementation of crowns, often is used by endodontists when the crown, be it provisional or permanent, dislodges during endodontic treatment and the patient is referred back to the restoring dentist for re-luting the restoration. Because IRM contains eugenol, if a resin cement will be used for permanent cementation the preparation needs to be cleaned thoroughly to prevent the eugenol from interfering with the cement’s adhesion.
Durelon typically is used as a permanent cement, but when the liquid-to-powder ratio is altered in favor of a greater amount of liquid it can be used as a provisional cement. This product works well when additional retention is needed from the cement to retain the restoration or the restoration will need to be used for extended periods of time.
The early provisional cements were supplied as power-liquid preparations and could be messy to mix. Additionally, wide variations in mixtures resulted because clinicians did not always incorporate the amount of liquid into the powder exactly as directed. These materials still are available but have been replaced by paste-paste formulations. These materials are easier to mix and measure, providing more consistency from batch to batch. They, as with the powder-liquid materials, often result in excess material being mixed, and waste can be significant. The newest generation of materials have taken the paste-paste formulations from tubes into automix syringes. The main benefits to these syringable materials is the consistency of the mix each time and the reduction of waste.
Tips to Provisional Cementation
As discussed, the biggest issue to cementation of a provisional restoration is failure to seat the restoration fully because of excessive cement. This result often requires further occlusal adjustment of the provisional restoration because it is sitting higher than when it was adjusted with no cement present. This result is more common with posterior restorations because of the geometry of the preparations and the flat occlusal surfaces in that area of the mouth. The easiest method to avoid this dilemma is to use a minimal amount of provisional cement and to place it only on the interior margins. As the restoration is seated, the cement is carried toward the occlusal surface, the axial walls are coated, and excess cement is not trapped on the occlusal surface and does not prevent full seating because of the hydraulic pressure.
Clean-up of the provisional cement may be expedited by lightly painting the exterior marginal surface and tissue side of the pontic areas with a water-soluble material, such as K-Y® jelly (McNeill PPC Inc, Titusville, NJ) or glycerine. The clinician should avoid using petroleum jelly because this water-insoluble product may be difficult to get off the surface of the provisional or become incorporated into the provisional cement, weakening its retention. When removing the excess cement, it is easier if the cement is allowed to set fully. After setting, it can be flaked off with a scaler or other appropriate instrument.
While no provisional cement is ideal for all situations, the clinician should base material choice on how much retention is needed for the provisional, how long the provisional will need to be in the mouth, and if the permanent restoration will be luted with an adhesive material. With the broad range of treatment offered in today’s average practice the clinician should have several provisional cements in the practice. These cements should include a cement that contains eugenol or a eugenol-free provisional cement with desensitizing agents. The clinician also should have a provisional cement with increased retentive properties for those situations where more retention is needed. Additionally, a resin provisional cement for luting implant-cemented restorations should be in the armamentarium.
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About the Author
Gregori M. Kurtzman, DDS
Silver Spring, Maryland