A dental crown, often referred to as a cap, is a custom-made, tooth-shaped covering placed completely over a damaged or compromised natural tooth. When a tooth has sustained significant harm that cannot be fixed with a simple filling, a crown provides a stable and protective solution. This restoration is widely used to repair and strengthen teeth, addressing the structural integrity and function of the tooth.
Defining the Dental Crown and Its Purpose
A dental crown is designed to cover the entire visible portion of a natural tooth, starting at the gum line. This complete coverage shields the underlying, weakened tooth structure from the forces of chewing. The primary function of this custom-fitted covering is to restore the tooth’s original shape, size, and strength. The crown also serves to improve the appearance of the tooth, matching the color and contours of the surrounding teeth.
Primary Reasons for Crown Placement
One of the most frequent reasons for crown placement is to protect a tooth that has become structurally weak. This vulnerability often occurs after extensive tooth decay has been removed, leaving insufficient natural tooth material to withstand normal chewing forces. A crown acts to bind the remaining portions of the tooth together, preventing the tooth from splitting apart under pressure.
Crowns are also necessary for restoring a tooth that has already suffered a significant break or severe wear. Teeth that are chipped, cracked due to trauma, or worn down by conditions like bruxism require the complete coverage of a crown. This restoration rebuilds the tooth structure, prevents further deterioration, and allows the tooth to regain its proper height and form for stable function.
When a tooth has a very large filling that occupies a significant portion of its width, a crown is often recommended for additional support. While fillings repair a hole, an extensive one can weaken the surrounding walls of the tooth, making it prone to fracture. The crown distributes the biting load more evenly across the tooth surface, stabilizing the remaining structure.
Teeth that have undergone root canal therapy almost always require a crown to complete the restoration. The root canal procedure removes the tooth’s internal pulp, which can make the tooth more brittle and susceptible to fracture. Placing a crown provides the necessary external reinforcement to protect the tooth from cracking, especially in the molars and premolars that bear the heaviest chewing forces.
Crowns are also essential components in replacing missing teeth, as they are used to cover a dental implant. Once the titanium implant fixture is placed into the jawbone, a custom-made crown is attached to serve as the functional and visible replacement tooth. Crowns can also be used for cosmetic modification, covering teeth with severe discoloration or misshapen features that cannot be corrected with simpler treatments.
The Process of Getting a Crown
The procedure for receiving a permanent dental crown typically requires two separate office visits. The first appointment is dedicated to preparing the tooth and gathering the necessary information for fabrication. The dentist reshapes the tooth, removing enamel to create space for the new crown to fit without appearing bulky. After shaping, an impression is taken to create a precise model, which is sent to a dental laboratory for custom fabrication. Before the patient leaves, a temporary crown is placed to protect the tooth and maintain the space.
The fabrication process usually takes one to two weeks at the dental lab. The patient returns for the second appointment once the custom crown is ready. The temporary crown is removed, and the permanent crown is checked for its fit, bite alignment, and aesthetic appearance. Once confirmed, the crown is permanently bonded to the prepared tooth using a strong dental cement.
Types of Crown Materials and Their Differences
Modern dental crowns are made from several different materials, each offering a unique balance of durability and appearance. All-porcelain or all-ceramic crowns are valued for their superior aesthetic qualities, as they closely mimic the translucent appearance of natural tooth enamel. These materials are often the preferred choice for front teeth, where visibility is the main concern, though they can be less strong than metal-based options.
Crowns made from metal alloys, such as gold or palladium, offer the highest level of strength and resistance to wear. These are typically reserved for molars in the back of the mouth, where intense chewing forces require maximum durability and the metallic color is not visible. A hybrid option is the porcelain-fused-to-metal (PFM) crown, which features a metal base for strength covered by a layer of tooth-colored porcelain.
A popular contemporary material is Zirconia, a type of ceramic known for its exceptional strength and fracture resistance. Zirconia blends the durability of metal with the natural-looking color of porcelain, making it a versatile choice for both front and back teeth. The final material selection is determined by the tooth’s location, the patient’s bite forces, and aesthetic preferences.