A temporary crown is a provisional restoration placed over a tooth prepared for a final, permanent crown. This interim covering serves several important functions during the weeks it takes for a dental laboratory to fabricate the definitive restoration. Its primary purpose is to protect the underlying, sensitive tooth structure, which has had much of its protective enamel removed. The temporary crown also maintains the correct spacing and alignment of adjacent teeth, preventing them from shifting into the open space. It also helps preserve the health of the gum tissue and offers aesthetic normalcy until the permanent solution is ready.
Primary Categories of Temporary Crown Materials
The materials used for temporary crowns fall into three primary categories, selected based on the clinical situation, desired aesthetics, and required duration of wear. Custom-made resins are the most common choice, fabricated directly on the prepared tooth using a pre-existing mold or impression. Bis-Acryl composite resins are widely utilized within this group, offering a dimethacrylate-based polymer that provides improved strength and superior aesthetics compared to older acrylic options.
Another custom material is based on acrylic resins, such as Polymethyl Methacrylate (PMMA) or Polyethyl Methacrylate (PEMA). These acrylics are easy to manipulate and cost-effective, but they may generate more heat during setting and typically have lower fracture resistance than Bis-Acryl composites.
Pre-formed crown materials offer a quick, chairside solution, particularly for posterior teeth or pediatric dentistry. These include tooth-colored polycarbonate shells, which are adapted and lined with resin to fit the prepared tooth, or metal options like stainless steel crowns. Stainless steel crowns are extremely durable but used primarily where aesthetics are less of a concern.
Material Properties Necessary for Interim Use
The selection of temporary crown materials is determined by properties that prioritize ease of use and short-term functionality over long-term durability. A primary requirement is the material’s ability to be fabricated quickly at the dental office, often using a direct technique involving a fast, chemical-cure or light-cure setting process. This chairside fabrication reduces the time the patient spends in the dental chair for temporary placement.
The materials must also possess sufficient mechanical strength to withstand normal chewing forces for a few weeks without fracturing. Temporary materials must also exhibit an acceptable aesthetic quality for the interim period, especially for front teeth, which is why tooth-colored resins are frequently chosen.
Biocompatibility is also a factor, ensuring the material does not irritate the pulp or surrounding gum tissues. A defining requirement is the material’s ease of removal; the temporary cement and crown must allow the dentist to take it off without damaging the underlying tooth preparation. This ensures a smooth transition when placing the final, permanent restoration.
How Temporary Materials Differ from Permanent Crowns
The materials chosen for temporary crowns are fundamentally different from those used for definitive, long-term restorations, reflecting their distinct functional requirements. Permanent crowns are often fabricated from durable materials like ceramics (such as Zirconia or lithium disilicate) or from metal alloys, including gold. These materials are engineered for maximum hardness, longevity, and resistance to wear over many years, unlike the few weeks a temporary crown is intended to last.
Permanent crowns are custom-milled in a laboratory to achieve a near-perfect marginal seal and a precise fit against the prepared tooth structure. This accuracy is necessary to prevent leakage, recurrent decay, and gum irritation. Conversely, temporary crowns, made from softer resins or acrylics, do not offer this level of precision or strength. Temporary materials are more prone to abrasion, staining, and wear, and their margins are not designed for the same long-term biological seal as a final ceramic or metal restoration.