Selecting the Right Temporary Cement

Selecting the appropriate temporary cement for the right situation is one of the critical steps in any crown and bridge procedure. It is the last step at the end of the preparation appointment, and an adverse outcome at this stage could mean the prosthesis loosens or comes off entirely, necessitating an emergency visit to your office. The right temporary cement helps to minimize these untoward events. Temporary cement helps to retain the prosthesis, and also allows for easy removal of the prosthesis with damaging the underlying structure. These are very difficult properties to build into any dental material.
If the temporary cement has the characteristics shown (Table), and the provisional restoration is well made with good contour and margins, then oral tissues will be protected and remain healthy while the final restoration is being fabricated.

Table. Characteristics of Temporary Cements1

Easy removal of excess cement from around the margins upon cementation
Good marginal seal to help minimize sensitivity
Good retention, yet allows easy removal of the temporary prosthesis
Low solubility in oral fluids
Compatibility with provisional resin restorations, resin core materials, bonding agents and permanent cements

FACTORS IN SELECTING TEMPORARY CEMENTS
Selecting the right temporary cement for the right clinical situation involves examining a number of factors that need to be assessed.
One must first take into account how long the prosthesis will be in place; what types of occlusal and parafunctional forces will be exerted on the prosthesis; the shape and parallelism of the preparation or if multiple abutments the parallelism of all the abutments; the materials to be used to restore the preparation and type of cement used for permanent cemen­tation; the height of the preparation; and lastly the thickness of the walls of the preparation.
Each of these factors will influence the type of retention or adhesion a temporary crown will require. For example, a temporary crown placed on a short preparation subject to off-axis occlusal loading may require very retentive temporary cement. A prosthesis that needs to be in place for a long time may also require very retentive temporary cement. A temporary crown placed on a long (tall) preparation for a short period of time may not require a retentive temporary cement. There is no one universal temporary cement so at least 2 types of temporary cements available with varying adhesive and retentive properties should be made available. One should also become very familiar with the working properties of these cements so that one can determine which cement is appropriate for each particular clinical situation.

[The previous paragraph was reprinted from the article "Temporary Cementation: A Critical Step in Successful Operative Dentistry" by Dr. Abrams published in Dentistry Today in August 2005.]

Figure 1. Maxillary left second bicuspid and first molar, previously (heavily) restored and presenting with broken restorations.

Figure 2. Preparation completed on the maxillary left second bicuspid. Note the lack of lingual wall on the preparation and undercut on the interior aspect of the buccal wall.

Figure 3. Cast post and core restorations in place on both teeth. Note the depression on the occlusal surface which may act to bind an adhesive temporary cement.

Figure 4. Dispensing Temrex CR into the temporary crown. Easy dispensing is achieved with the automix system.
Figure 5. Porcelain-bonded-to-metal crowns in place. Note the lack of irritation in the gingival tissue.

COMPOUNDS THAT CAN AFFECT PERFORMANCE
Temporary cements can contain a number of compounds which will affect their performance. There are 3 classes of components in temporary cements: (1) resin-based containing diurethane dimethacrylate, such as TNE (Temrex); (2) zinc oxide eugenol, such as TempBond (Kerr), Temrex Cement (Temrex), Temrex CR Plus (Temrex), and Embonte (DUX); and (3) zinc oxide noneugenol, such as Temrex CR (Temrex), ZONE (DUX), and TempBond NE (Kerr).
Each of these components imparts different physical properties to the cement and may interact adversely with the permanent cement.2 Studies have shown that eugenol containing temporary cements do not adversely affect the setting times of permanent cements.3 If the temporary cement is completely cleaned from the preparation surface, the eugenol will not affect the set of the permanent cement.4-7 Residual eugenol left on the preparation may affect the hardness of any underlying composite core materials,8,9 or bonding of composite to tooth structure.10 Eugenol containing temporary cements do have a number of important characteristics including antimicrobial properties11 and the ability to decrease post-preparation sensitivity. Eugenol containing temporary cements should be considered if these 2 properties are required.

MATCHING PROPERTIES TO THE CLINICAL SITUATION
The other key factors to consider when selecting the right temporary include bond strength, solubility in oral fluids, retentive strength, and flexural strength. These physical properties should be matched to the particular clinical situation. Assessing the number and draw of each preparation will allow you to select the cement with the right amount of retention but allow for easy removal. An ill-fitting temporary crown or a stock temporary crown will need a cement that can restore the marginal integrity and resist dissolution in oral fluids. So selection of the right temporary cement demands an understanding of the clinical situation and oral environment.

CASE REPORT
In this patient (Figure 1), we were fabricating cast-post cores and porcelain-bonded-to-gold crowns to restore the maxillary left second bicuspid and first molar. At each step in the process, we needed to carefully assess the clinical situation and the performance requirements of the temporary cement before cementation of the prosthesis. 
In the first stage, we needed to secure temporary crowns to preparations which had very minimal tooth structure (Figure 2) because both of these teeth were heavily restored previously. The occlusal loading was normal and evenly spread across the teeth in the arch. As a result, aberrant occlusal forces would not adversely affect the bond of the cement, or overload the crowns. An 856-016 diamond bur (Pirhana [SS White] was used to remove the old restorations and prepare the remaining tooth structure. Careful use of these diamond burs allowed the re­moval of the old restorations and the preparation of the cavity walls, without inducing stress which could have fractured these thin walls of tooth. Expasyl (Kerr) was used to retract the soft tissue from the crown margins and also to minimize soft-tissue bleeding. 
Once the teeth were prepared for cast post cores, there was very minimal tooth structure left. We needed to find a temporary cement that could help retain the temporary crown and post without affecting the set of the resin cement used to bond in the final cast post and core. A eugenol-containing temporary cement might affect the set of the permanent cement within the root canal system since we could not ensure that it would be removed in its entirety. A temporary cement with moderate retentive properties that would not bind to the remaining buccal wall of tooth upon removal was needed for this clinical situation. Temrex CR (a noneugenol-containing cement) was selected since it had moderate compressive strength and would retain the crowns in this situation. The cast posts were cemented permanently with Cement-It (Pentron Clinical Technologies), a resin-based cement that provided support and good bond strength between the gold alloy posts and the dentinal walls of the root canal system. 
Once the cast posts were permanently cemented (Figure 3), we again assessed the clinical situation. The preparations were of moderate height with relatively parallel walls. We also had placed depressions in the occlusal aspect of the posts using an 801-018 diamond bur (Pirhana) to help prevent rotation once the permanent crowns were placed. If we used temporary cement with strong adhesive properties, we were concerned that the temporary crowns would bind to the posts. Our laboratory had fabricated good-fitting custom temporary crowns, so we did not need to look for an adhesive temporary cement. In this situation we again selected Temrex CR. The temporary cement was designed to retain the crowns to preparations that were moderate in height with parallel walls, so bond strength was not an issue. 
Temrex CR was dispensed from an automix syringe (Figure 4), and clean-up around the crown margins was eas­ily done. The automix system always helps to produce a uniform mix with optimal physical properties. The ce­ment had minimal microleakage and low solubility in oral fluids so, with a good-fitting crown, we were not concerned about caries or demineralization of the underlying tooth structure. Temrex CR had a bond strength that allowed for the easy removal of the temporary crowns when needed. 
The final crowns were cemented a few weeks later (Figure 5) with a resin-based temporary cement (Cement-It) The temporary cement not only retained the crowns during this period, but did not irritate the gingival tissues. The post surfaces were cleaned and checked so that they were free of debris and cement residue before cementation.

SUMMARY: IMPORTANCE OF PROPER PROVISIONALIZATION
The construction of a temporary prosthesis and temporary cementation are key steps in achieving a successful treatment outcome. A well-designed prosthesis that replicates ideal tooth anatomy will ensure the health of the oral tissues. Temporary cementation is a critical part of the provision of any final prosthesis. Selecting the right temporary cement to match the clinical situation is a key factor in this step.
An assessment of the clinical situation in which you are placing the temporary prosthesis will allow you to select the right cement. Preparation height and draw, occlusal loading, presence of undercuts, type of final cements are key factors in the selection of the temporary cement. No one temporary cement can perform well in every clinical situation.
Practitioners should have at least 2 temporary cements available with different properties to ensure the prosthesis is firmly anchored yet easily removed. Care and understanding of the objectives of your temporary prosthesis will help you find the right temporary cement thus ensuring a predictable and successful outcome for the procedure.


References

  1. Farah JW, Powers JM. Temporary resin cements. The Dental Advisor. 1995;12:8.
  2. Paul SJ, Schärer P. Effect of provisional cements on the bond strength of various adhesive bonding systems on dentine. J Oral Rehabil. 1997;24:8-14.
  3. Schwartz R, Davis R, Hilton TJ. Effect of temporary cements on the bond strength of a resin cement. Am J Dent. 1992;5:147-150.
  4. Worley JL, Hamm RC, von Fraunhofer JA. Effects of cement on crown retention. J Prosthet Dent. 1982;48:289-291.
  5. Ganss C, Jung M. Effect of eugenol-containing temporary cements on bond strength of composite to dentin. Oper Dent. 1998;23:55-62.
  6. Schwartz R, Davis R, Mayhew R. The effect of a ZOE temporary cement on the bond strength of a resin luting cement. Am J Dent. 1990;3:28-30.
  7. Leirskar J, Nordbø H. The effect of zinc oxide-eugenol on the shear bond strength of a commonly used bonding system. Endod Dent Traumatol. 2000;16:265-268.
  8. Millstein PL, Nathanson D. Effects of temporary cementation on permanent cement retention to composite resin cores. J Prosthet Dent. 1992;67:856-859.
  9. al-Wazzan KA, al-Harbi AA, Hammad IA. The effect of eugenol-containing temporary cement on the bond strength of two resin composite core materials to dentin. J Prosthodont. 1997;6:37-42.
  10. Paige H, Hirsch SM, Gelb MN. Effects of temporary cements on crown-to-composite resin core bond strength. J Prosthet Dent. 1986;55:49-52.
  11. Markowitz K, Moynihan M, Liu M, et al. Biologic properties of eugenol and zinc-oxide eugenol. A clinically oriented review. Oral Surg Oral Med Oral Pathol. 1992;73:729-737.

Dr. Abrams is the founder of Four Cell Consulting, Toronto, ON, which provides consulting services to dental companies in the area of new product development and promotions. Over the last 6 years, he has been involved in the research and development of a The Canary Dental Caries Detection System (thecanarysystem.com), a laser based system for the early diagnosis of caries. He currently holds a patent on this new technology. Dr. Abrams is a partner in a group practice in Scarborough, ON. He is a Fellow of the Pierre Fauchard Academy and the Academy of Dentistry International and a member of the Canadian Academy of Esthetic Dentistry, European Organization for Caries Research, and the Canadian Association for Public Health Dentistry. Dr. Abrams has published over 90 articles in various international publications, and was awarded the Barnabus Day Award from the Ontario Dental Association for 20 years of distinguished service to the dental profession. He can be contacted at (416) 265-1400 or vial e-mail at dr.abrams4cell@sympatico.ca.

Disclosure: Dr. Abrams is chief clinical consultant for Temrex Corporation.



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