Temporary Crowns and Restorations in Dentistry

Temporary restorations play a crucial role in the field of dentistry. They offer several advantages during the preparation and application process of permanent restorations. Here are the benefits of temporary crowns and restorations, and the essential characteristics a good temporary restoration must possess: Advantages of Temporary Crowns: Protection of the...
Dental image of a stainless steel crown a silver cap used for restoring children's teeth affected by
Temporary Crowns and Restorations in Dentistry
Share This Post:

Temporary restorations play a crucial role in the field of dentistry. They offer several advantages during the preparation and application process of permanent restorations. Here are the benefits of temporary crowns and restorations, and the essential characteristics a good temporary restoration must possess:

Advantages of Temporary Crowns:

  • Protection of the Pulp: They shield the pulp from mechanical, chemical, thermal, and bacterial effects, ensuring pulpal protection.
  • Restoration of Lost Functions: They restore the functions, phonation, and tissue continuity lost due to tooth preparation.
  • Positional Stability: They maintain the cut tooth in its normal position, providing positional stability.
  • Periodontal Health: They prevent positional changes in surrounding periodontal tissues, thus preserving periodontal health.
  • Assessment of Problematic Teeth: They aid in determining the prognosis of problematic teeth.
  • Motivation for Prosthetic Treatment: They increase patient motivation for prosthetic treatment.
  • Preliminary Information: They provide preliminary information about the dimensions and shape of the planned permanent crown prosthesis.

Characteristics of a Good Temporary Restoration:

  • Pulp Protection: Temporary restorations should be made from materials that do not transmit extreme temperature changes. The edges of the restoration should prevent saliva and food leakage.
  • Positional Stability: They should not allow elongation or tilting of the prepared tooth and maintain such stability until the restoration is complete.
  • Occlusal Function: Temporary restorations should aid in maintaining chewing function. They should also ensure patient comfort, prevent orthodontic movement of the tooth, and help in avoiding Temporomandibular Joint (TMJ) disorders.
  • Ease of Cleaning: The contours and material of the restoration should allow for easy cleaning. This is important to maintain the health of the gingival tissues.
  • Non-Overlapping Crown-Gingiva Junction: Temporary restorations should not impinge on the gingiva, causing inflammation or trauma in this area. This prevents bleeding during impression taking and cementation.
  • Strength and Retention: Temporary restorations should be resilient enough to withstand forces without dislodging or breaking, and they should provide good retention.
  • Aesthetics: Particularly for front teeth, temporary restorations should provide a pleasing aesthetic, enhancing the patient’s appearance.

 

Temporary Restoration Materials and Fabrication Techniques: Temporary restorations are often made from resin-based materials that polymerize chemically. These materials include:

Methacrylate-Based Materials:

  • Polymethyl methacrylate (PMMA)
  • Polyethyl methacrylate (PEMA)
  • Polyvinylethyl methacrylate (PVEMA)

Resin-Based Materials:

  • Bis-acryl composite resin
  • Urethane dimethacrylate

The fabrication techniques of these materials vary depending on the properties of the material used and the conditions of fabrication. There are three different fabrication techniques:

Direct Technique:

  • Before tooth preparation, a silicone impression is taken.
  • After tooth preparation, temporary crown material is filled into the impression tray and placed in the mouth.
  • The material is removed from the mouth before complete hardening, excess is trimmed, and then reinserted.
  • Removed before complete polymerization and allowed to reach final hardness in warm water.
  • Smoothing and polishing are performed.
  • In the direct method, the material should not be in excessive contact with the tooth; the pulp should be protected from heat and monomers as much as possible.
  • Materials that do not produce exothermic heat should be used.

Indirect Technique:

  • Impressions of the prepared teeth and opposing arch are taken to create a model.
  • Temporary restorations are prepared in the laboratory on this model.
  • In this method, there is no monomer contact with the tooth and gingiva.
  • The tooth is not exposed to the heat of the resin.
  • Better marginal adaptation is achieved.
  • Shrinkage and distortion are controlled.

Direct-Indirect Technique:

  • In this method, the external form of the temporary crown is obtained indirectly, while the internal form is created using the direct technique.
  • An alginate impression is taken before tooth preparation and a model is obtained.
  • Transparent propylene or cellulose acetate sheets are adapted to this model with heat and pressure, and the edges are trimmed and fitted in the mouth.
  • The temporary material is filled into this mold and applied over the teeth in the mouth.
  • After hardening, smoothing and polishing are done.

Temporary Crowns and Restoration Methods: A good temporary restoration should possess characteristics such as pulp protection, positional stability, occlusal function, ease of cleaning, non-overflowing crown-gingival junction, durability and retention, and aesthetics. These qualities can vary depending on the method and materials used.

Prefabricated Temporary Crowns: Prefabricated crowns provide a quick solution after tooth preparation, saving time though they may not precisely replicate the original tooth’s appearance. Some types include:

  • Polycarbonate Crowns: These are the most natural-looking prefabricated crowns available in a single shade. They are selected for the appropriate size, placed over the tooth, and resin is poured inside to secure them to the tooth.
  • Cellulose Acetate Crowns: Thin and transparent, available in different sizes for each tooth. After tooth preparation, the suitable size crown is placed on the tooth, resin material is poured inside, and after the resin hardens, the acetate crown is removed with a scalpel.
  • Aluminum Crowns: Typically used for posterior (back) teeth. The appropriate size crown is selected, adapted to fit the tooth’s collar, bitten down to ensure occlusal compatibility, and resin is poured inside to apply it to the tooth.

The use of CAD/CAM (Computer-Aided Design and Computer-Aided Manufacturing) technology has further simplified the preparation of temporary restorations. This technology eliminates traditional impression methods, achieves more compatible restorative materials in less time, and reduces error potential. CAD/CAM systems are used in various ways:

  • Direct In-Clinic Systems: The tooth preparation is scanned intraorally, and the restoration is fabricated in the clinic. Examples include the CEREC and E4D Dentist systems.
  • Lab-Based Systems: Scanning is done from a plaster model or impression. The substructure is produced, and the technician adds porcelain to characterize the restoration. Systems in this category include CEREC inLab, DCS Preci-fit, Cercon, and Everest.
  • Production Center-Based CAD/CAM Systems: After the model is scanned in the lab, data is sent to a central production center via the internet. The fabricated substructure is sent back to the lab for porcelain application. Examples of these systems are Procera and Lava.

Additionally, polymer blocks for long-term temporary restorations are available for use with CAD/CAM systems. These blocks are used for special applications such as investment castings and surgical splints that do not leave monomers.

The cementation of temporary crowns is done using tissue-friendly and easily removable cement. Calcium hydroxide or zinc oxide eugenol pastes can be used for this purpose. Eugenol-containing ones have a sedative effect on the pulp, while non-eugenol ones usually contain calcium hydroxide and help heal the pulp. The choice of cement depends on the properties of the restoration and the patient’s condition.

RELATED POST

Delve deeper into insights and perspectives on our latest topic.”