A temporary crown, or provisional restoration, is a molded cover placed over a tooth prepared for a permanent crown. Its fundamental purpose is to serve as a placeholder while the custom-made, permanent crown is fabricated in a dental laboratory. The temporary crown protects the underlying tooth structure from bacteria, temperature changes, and fracture. It also maintains the correct spacing and alignment with adjacent and opposing teeth, preventing shifting that could compromise the fit of the final restoration. This interim cap is cemented with a weak adhesive, allowing for easy removal when the definitive crown is ready.
Primary Materials Used in Temporary Crowns
Most temporary crowns are made from tooth-colored resins, primarily acrylic resins and bis-acryl composites. Acrylic resins, such as polymethyl methacrylate (PMMA), have a long history of use in dentistry due to their cost-effectiveness and ease of manipulation. Dentists can quickly mix and shape these materials directly in the patient’s mouth, providing a fast solution for temporary coverage.
Bis-acryl composite resins are increasingly popular, offering improved aesthetics and greater strength compared to traditional acrylics. These materials provide a more natural appearance, closely mimicking the translucency of natural tooth enamel. They also generate less heat during the setting process, which reduces the potential for discomfort to the prepared tooth.
In addition to custom-fabricated options, pre-formed crowns are available for specific situations, offering a rapid chairside solution. These prefabricated shells are made from materials like polycarbonate, which provides an aesthetic, tooth-colored option, or aluminum, which is a metallic choice often used for posterior teeth. The dentist selects the appropriate size and then trims or adjusts the shell to fit the prepared tooth.
Why Temporary Materials Are Chosen
Temporary materials are selected for characteristics that prioritize ease of handling over the long-term durability of permanent materials. They have a relatively quick setting time, which is necessary for efficient fabrication during a single dental appointment. This allows the dentist to rapidly contour and adjust the restoration before the patient leaves the office.
These materials are intentionally designed with lower mechanical strength, a necessary trade-off for their ease of removal. Secured with temporary cement, their weaker nature ensures the prepared tooth is not damaged when the crown is lifted off. While durable enough to withstand normal chewing forces for a few weeks, their softer composition allows for quick adjustments and polishing.
Bis-acryl is sometimes chosen over PMMA because it involves less polymerization shrinkage, resulting in a more precise fit around the tooth margins. However, both material types are engineered to be cost-effective and easily manipulated, making them ideal for the interim period. Their temporary nature means they can be easily modified or replaced if the patient’s needs change before the final crown is ready.
Care and Expectations While Wearing a Temporary Crown
A temporary crown is typically worn for two to three weeks, the time required for the dental laboratory to manufacture the permanent crown. During this period, modifications to diet and oral hygiene are necessary to prevent the temporary crown from dislodging or fracturing. Patients should avoid sticky foods like caramel or taffy, as these can pull the crown off the prepared tooth.
Hard or crunchy foods, such as nuts or ice, should also be avoided, as they can cause the relatively softer temporary material to crack or break. Patients are encouraged to chew primarily on the side of the mouth opposite the temporary restoration to minimize the stress placed upon it. Maintaining good oral hygiene is still important, but brushing near the temporary crown should be done gently with a soft-bristled brush.
When flossing around a temporary crown, a modified technique is advised to prevent lifting the crown off the tooth. Instead of pulling the floss up through the contact point, it should be carefully pulled out sideways from between the teeth after cleaning. If a temporary crown does become loose or falls off, contact the dental office immediately for re-cementation to protect the underlying tooth and prevent adjacent teeth from shifting.