A temporary crown is a provisional restoration placed over a tooth prepared for a permanent cap. This short-term covering shields the remaining tooth structure while the final crown is fabricated in a dental laboratory. These devices are typically constructed from materials like acrylic or composite resin, which are not designed for long-term wear or the intense forces of chewing. Its primary function is to protect the sensitive, reduced tooth and maintain correct spacing for a limited period, usually two to three weeks.
Structural Degradation and Loss of Protection
Provisional restorations possess lower inherent strength compared to the ceramics or metals of a permanent crown. Extended exposure causes the softer acrylic or resin to experience significant wear and abrasion. This gradual flattening and thinning compromises the bite alignment and reduces the physical barrier protecting the underlying tooth.
The temporary cement used is intentionally weak, allowing for easy removal when the permanent crown is ready. Over a prolonged period, this cement naturally dissolves and washes out due to saliva, temperature fluctuations, and chewing forces. As the seal degrades, the crown may loosen or fracture entirely, leading to a complete loss of protection for the prepared tooth.
When the temporary crown is compromised, the prepared tooth margin loses its tight bacterial seal. The resulting microleakage creates pathways for oral bacteria and food debris to infiltrate the space between the tooth and the restoration. This allows acids and plaque to accumulate directly against the dentin, the underlying layer of the tooth structure.
Risks to the Underlying Tooth and Gums
The most significant danger of extended temporary crown use is increased susceptibility to secondary decay on the prepared tooth. Once the temporary cement seal washes out, bacteria begin to demineralize the exposed tooth structure. This decay progresses rapidly because the dentin is much softer than the outer enamel, potentially undermining the structural integrity of the preparation.
The prepared tooth loses its protective enamel layer, making it highly susceptible to thermal and chemical changes without insulation. Patients frequently experience heightened sensitivity to hot and cold temperatures or air exposure if the temporary crown’s fit is poor or has deteriorated. This sensitivity signals that the underlying dentinal tubules, which lead to the nerve, are exposed.
Temporary crowns are inherently less polished and their margins are often rougher than those of a lab-fabricated permanent restoration. The imperfect fit near the gum line acts as a niche for plaque accumulation that is difficult to clean. This chronic irritation of the gingival tissues leads to localized inflammation, known as gingivitis, characterized by redness and bleeding.
If decay is left untreated, the bacterial infection can eventually penetrate the pulp chamber, which houses the tooth’s nerve and blood vessels. This progression leads to pulpitis, often necessitating an emergency root canal procedure to save the tooth. In severe cases, the decay may be so substantial that the tooth is no longer restorable, requiring extraction.
Complications for the Permanent Crown Procedure
Prolonged use of a temporary crown can negatively alter the precise spatial relationship between the teeth, jeopardizing the fit of the final restoration. If the temporary crown wears down or is lost, adjacent teeth can drift or tilt into the space. Simultaneously, the opposing tooth may supra-erupt, meaning it grows slightly longer in an attempt to meet the space.
This dimensional change means the permanent crown, fabricated based on the original impression, will no longer seat correctly. The crown may be too large to fit between the shifted teeth or too short to meet the opposing tooth, causing bite discrepancies. Addressing this fit issue often requires the dentist to spend extra time adjusting the permanent crown, which can weaken the restoration.
If tooth movement is substantial or secondary decay has occurred, the dentist may be forced to take a new impression or re-prepare the tooth entirely. This procedural delay extends the treatment timeline and incurs additional laboratory and clinical costs, negating the original plan. Gum inflammation or underlying infection also requires resolution before the permanent crown can be successfully cemented, complicating the final placement appointment.