A dental crown is a common and effective treatment in restorative dentistry. When a tooth suffers significant damage, decay, or structural compromise, a crown provides a way to save the tooth structure rather than resorting to extraction. This treatment completely covers the entire visible portion of the affected tooth, acting as a new, durable outer surface.
Defining the Dental Crown
A dental crown is a fixed, custom-made restoration shaped like a natural tooth. Often called a “cap,” it fits precisely over the entire prepared tooth surface above the gum line. This prosthetic device is cemented into place, making it a permanent fixture. The primary function of a crown is to restore the tooth’s original size, shape, and strength. It also improves the appearance of the tooth and acts as a protective shield against further breakdown.
When is a Crown Necessary?
Dentists recommend a crown when the natural tooth structure is too compromised for a standard filling or less extensive restoration. Crowns are necessary in several situations:
- To protect a tooth weakened by a very large filling, where the remaining material is susceptible to fracture.
- To restore a tooth that is severely worn down or has significant fractures.
- To prevent cracking in teeth that have undergone root canal therapy, which often become brittle.
- To cover a dental implant, serving as the functional and aesthetic replacement for a missing tooth.
- In cases of extensive decay where a large portion of the tooth must be removed, providing necessary support and structural integrity.
The Crown Procedure: Step-by-Step
The traditional process for receiving a permanent crown typically involves two appointments. The first visit focuses on preparing the affected tooth to ensure the new restoration fits correctly. The dentist administers a local anesthetic and then reshapes the tooth by filing down the sides and chewing surface. This preparation creates space for the crown material to fit without feeling bulky.
Impression and Temporary Crown
Once the tooth is shaped, an impression is taken using either putty material or a digital scanner. This captures the exact dimensions of the prepared tooth and surrounding teeth, ensuring the laboratory fabricates a precise fit. A temporary crown, usually made of acrylic resin, is then placed over the prepared tooth to protect it while the permanent restoration is being made.
Placement (Second Appointment)
The temporary crown is held in place with a weaker, temporary cement. At the second appointment, the temporary crown is removed. The permanent crown is carefully checked for fit, bite alignment, and color match before being bonded to the prepared tooth structure using a strong dental cement.
Materials Used in Dental Crowns
The material chosen for a crown balances the need for strength with aesthetic requirements.
All-Ceramic
All-porcelain or all-ceramic crowns mimic the natural translucency and color of tooth enamel, making them a preferred choice for front teeth. However, these materials can be more prone to chipping compared to metal options.
Metal Alloys
Metal alloys, such as gold or base-metal alloys, offer exceptional durability and strength, enduring heavy chewing forces without fracture. Due to their metallic appearance, these are typically reserved for molars in the back of the mouth where visibility is low.
Porcelain-Fused-to-Metal (PFM)
The Porcelain-Fused-to-Metal (PFM) crown is a hybrid option. It consists of a metal substructure covered by a layer of porcelain, providing both strength and a tooth-colored appearance.
Zirconia
Zirconia is an increasingly popular modern material, offering the strength of metal with the aesthetic qualities of ceramic. This material is a very hard, highly biocompatible ceramic oxide that can be color-matched to the adjacent teeth. The final choice depends on the tooth’s location, the patient’s bite forces, and aesthetic goals.