Dental crowns and bridges are fundamental components of restorative dentistry used to repair and replace damaged or missing teeth. These custom-made prosthetic devices restore the function, appearance, and structural integrity of the mouth. They are common solutions when a tooth has extensive decay, fracture, or when a gap exists due to tooth loss.
The Purpose and Function of a Dental Crown
A dental crown is a custom-made, tooth-shaped “cap” designed to cover the entire visible portion of a tooth above the gum line. Its primary purpose is to encase a damaged tooth, restoring its original shape, size, and strength, and improving its appearance. Crowns protect weak teeth from breaking, such as those weakened by a large filling or fracture.
The restoration is also commonly placed over a tooth that has received root canal therapy, which can leave the tooth brittle and susceptible to fracture. Crowns can be fabricated from a variety of materials.
Crown Materials
The materials used include:
- Metal alloys (such as gold or palladium)
- All-ceramic
- Porcelain fused to metal (PFM)
- Zirconia
The choice of material depends on the tooth’s location, aesthetic goals, and the biting force the restoration must withstand. Metal crowns are highly durable and wear-resistant, making them a good option for molars.
Understanding the Dental Bridge
A dental bridge is a fixed prosthetic device used to replace one or more missing teeth by bridging the gap between existing teeth. This restoration helps prevent the remaining natural teeth from shifting into the empty space, which can lead to bite problems.
Bridge Structure
The structure of a traditional bridge involves three main components. The abutment teeth are the natural teeth or dental implants located on either side of the gap. These teeth are prepared to receive crowns, which serve as anchors. The pontic is the artificial tooth suspended between the abutment crowns.
Traditional bridges require healthy teeth on both sides of the gap for support. Other designs exist, such as a cantilever bridge, which uses an abutment on only one side. A Maryland bridge uses a framework bonded to the back surfaces of adjacent teeth instead of full crowns. The bridge’s function is to restore chewing ability and maintain the proper alignment of the dental arch.
The Preparation and Placement Process
The process for receiving a crown or a bridge typically requires a minimum of two appointments, though same-day options are available with advanced technology. During the first visit, the dentist prepares the tooth or teeth that will support the restoration. This involves reshaping the existing tooth structure by removing a small amount of enamel so the prosthetic fits without appearing bulky.
After preparation, the dentist takes a precise impression of the prepared area, using either putty or digital scanning technology. This impression, along with details about the desired shade and bite alignment, is sent to a dental laboratory where skilled technicians custom-fabricate the final crown or bridge. A temporary restoration, usually acrylic, is then placed over the prepared tooth or teeth to protect them while the permanent prosthetic is being made.
The second appointment involves the placement of the permanent restoration, which usually occurs a few weeks later. The temporary device is removed, and the dentist checks the fit, color, and bite of the new crown or bridge. After any necessary minor adjustments are made, the restoration is permanently bonded or cemented onto the prepared teeth using a strong dental adhesive.
Longevity and Care for Restorations
Dental crowns and bridges are designed to be durable, but they are not permanent and generally have an expected lifespan ranging from 5 to 15 years, with many lasting longer with proper maintenance. Longevity is influenced by the quality of oral hygiene, the material used, and patient habits, such as grinding or chewing on hard objects. Regular dental check-ups and professional cleanings are essential for monitoring the restoration and the health of the underlying tooth and gums.
Meticulous daily care is required to extend the life of both crowns and bridges. This includes brushing twice daily with fluoride toothpaste and flossing every day to prevent decay and gum disease around the edges of the restoration. For bridges, special tools like floss threaders or interdental brushes are necessary to clean beneath the pontic, where a standard piece of floss cannot reach. Patients should avoid biting down on hard foods, which can cause the porcelain material to chip or crack.