Temporary restoration: The unsung hero

The temporary is probably the most undervalued element in the prosthodontic procedure. Rather than just serving as a space filler, it is a tool enabling dental practitioners to provide optimal conditions for subsequent steps such as impression taking and cementation and the necessary predictability for a successful final restoration. In addition, it is used as a mock-up of the final restoration, which allows for an esthetic and functional evaluation as well as – in some cases – a therapeutic clinical test drive. When done with too little care, an inadequate temporary can lead to unhealthy soft tissue, post-op sensitivities or, especially in anterior implant cases, unsatisfying pink/white esthetics.

For the production of a high-quality temporary restoration, several factors need to be respected. These include the selection of a high-performance material offering proven properties such as a high flexural strength and dimensional stability, and the use of an appropriate production technique.

Available materials
Essentially, there are four different types of temporization materials to choose from:

• Methacrylate resins
• Bis-acrylic (composite) resins
• Pre-formed composite crowns
• PMMA discs for CAD/CAM production.

The range of indications is limited for the latter two: The pre-formed composite crown is only available for single units in the posterior region. The production of temporaries from PMMA discs involves a lot of time, effort and cost. Consequently, this option is only interesting for particularly complex rehabilitations. For most indications, the choice is thus between methacrylate and bis-acrylic resins.

Bis-acrylic or methacrylate resins?
The are many reasons for choosing bis-acrylic resins over traditional methacrylate resins: The former materials offer better mechanical properties like a higher flexural strength and hardness, superior dimensional stability, a higher esthetic potential, a low polymerization shrinkage and setting temperature for higher patient comfort, and better mixing quality as they usually come in an automix syringe. Moreover, they stand out due to their ease of use. The only arguments in favor of methacrylate resins are their high fracture resistance (at the expense of dimensional stability) and low cost.^1,2

Methacrylate resin versus bis-acrylic resin: Overview of beneficial material properties

Hence, it comes as no surprise that bis-acrylic resins are preferable for the majority of temporization procedures. The materials work well for temporization on teeth and implants, are indicated for the production of single-unit and multi-unit restorations and are suitable for short-term and long-term temporization. They may be processed chairside or in the dental laboratory, depending on the existence of a tooth anatomy at the beginning of the procedure.

Production of a bis-acrylic temporary
No matter how a provisional crown or bridge is produced, it needs to be designed for optimal conditioning of the soft tissues. This is a relevant aspect for implant- and tooth-based restorations with subgingival margins. In this case, the soft tissue usually needs time to recover from tooth preparation, and ideal tissue management with the aid of the temporary will ensure easier exposure of the margins during impression taking and the desired dry, clean working field during cementation of the final prosthetic work.

Whenever teeth with a pre-existing anatomy need to be restored, chairside matrix production is usually possible. A preliminary impression is taken, filled with bis-acrylic resin and placed in the patient’s mouth to obtain the desired shape of the temporary. The process is completed with careful adjustments especially in the area of the restoration margin. With some materials like 3M™ Protemp™ 4 Temporization Material, the restorations’ surfaces become glossy just by wiping with ethanol.

In implant cases or other situations without pre-existing tooth anatomy, the matrix is usually manufactured in the dental laboratory. Here, the tooth anatomy is built up on a model and the matrix is produced e.g. by thermoforming. The subsequent procedure steps are the same as for the chairside procedure.

Alternatives
For temporary restoration of single teeth or implants in the posterior region, the use of a pre-formed composite crown (3M™ Protemp™ Crown Temporization Material) is a suitable option. The crown is malleable and available in a number of different sizes. Following size measurement and selection of the appropriate crown, it is trimmed at the gingival margin, adapted to the oral environment, light cured and polished. For placement, any temporary cement may be used.

For all situations requiring a thorough clinical test drive (as is the case for most complex rehabilitations), PMMA temporaries produced in the laboratory using CAD/CAM technology are recommended. As these temporaries are designed with the same software used for production of the final restorations, modifications performed during the test drive are easily transferred to the next steps in the procedure without any loss of information. The high strength and esthetic appearance of the materials used allows for a long wear time and a realistic forecast of the final treatment outcome.

Tips & tricks
Simplifying and standardizing material selection can help to ensure temporaries are made with consistent and sufficient quality. Important factors to be taken into account for material selection are the substrate (teeth or implants), the type of restoration (crown, veneer, or bridge), the number of units to be restored, and the duration of the temporization period.

Conclusion
The quality of the temporary has a huge impact on gingival health and the long-term success of the final restoration. Conditioning the gingival tissues in an optimal way, it has the potential to make life easier during impression taking and cementation, where a dry and clean working field is needed. In addition, temporization may be used as a tool for evaluation of functional and esthetic aspects – making it possible to create realistic expectations and thus provide the conditions needed for happy patients. By choosing the right material and technique, it is possible to accomplish these tasks reliably and with reduced effort.

¹ Kurtzman, G.M. 2008. Crown and Bridge Temporization Part 1: Provisional Materials. Inside Dentistry. Volume 4, Issue 8. Aegis Communications.
² Sarrett, D.C. (2011). Provisional Crown & Bridge Materials. ADA Professional Product View, 6(1), 8.