Restorative dentistry focuses on repairing and replacing damaged or lost teeth, aiming to restore function and a natural appearance. Dental crowns and dental bridges are two common fixed solutions used in this field. These prosthetics provide a durable way to rebuild a smile and improve the ability to chew and speak.
Defining Dental Crowns
A dental crown is a custom-made, tooth-shaped cap designed to completely cover a single tooth or a dental implant above the gum line. This restoration is cemented into place, fully encasing the visible portion of the tooth. Crowns are used when a natural tooth structure is compromised but the root remains healthy enough to provide support.
The primary function of a crown is to provide protection and strength to a weakened tooth. Dentists often recommend a crown when a tooth has a large filling, is cracked, severely decayed, or has been treated with a root canal procedure, as these conditions leave the remaining tooth vulnerable to fracturing. The crown acts like a protective helmet, holding the tooth together and absorbing the forces of chewing.
Beyond protection, a crown restores a tooth’s original shape, size, and appearance. This allows the tooth to fit properly within the patient’s bite and blend with adjacent natural teeth. To place a crown, the underlying tooth must be reduced in size by removing enamel and dentin, ensuring the cap fits without appearing bulky.
Defining Dental Bridges
A dental bridge is a fixed prosthetic device used to replace one or more missing teeth by spanning or “bridging” the gap in the dental arch. Unlike a crown, which restores a single damaged tooth, a bridge replaces lost teeth, preventing surrounding teeth from shifting into the empty space. This shifting can lead to bite problems, jaw pain, and difficulty maintaining proper oral hygiene.
The traditional bridge design is composed of three main parts that form a single unit. The core component is the artificial tooth, known as a pontic, which fills the space of the missing tooth. This pontic is anchored and held in place by crowns, called abutments, which are cemented onto the natural teeth located on either side of the gap.
The natural teeth that receive the abutment crowns must be healthy and strong enough to support the entire bridge structure and handle the additional biting forces. The preparation of these support teeth is similar to preparing a tooth for a single crown, requiring the removal of enamel to make room for the abutment crowns. When natural teeth are not available for support, the bridge can be anchored using dental implants, which are surgically placed into the jawbone to serve as abutments.
The Preparation and Placement Process
Receiving a dental crown or bridge generally requires two appointments spaced a few weeks apart. The first appointment involves preparing the mouth and taking precise measurements for the custom restoration. Preparation involves shaping the tooth or abutment teeth by reducing the structure to accommodate the thickness of the final prosthetic.
Once the preparation is complete, the dentist takes an impression of the prepared area and the surrounding teeth. This impression, which may be a physical mold using a putty-like material or a digital scan, is sent to a dental laboratory. The lab uses this model to custom-fabricate the permanent crown or bridge, ensuring it matches the patient’s bite, color, and shape.
A temporary crown or bridge is placed over the prepared teeth to protect them from sensitivity and damage while the permanent restoration is being made. This interim restoration maintains space and aesthetics until the final appointment, typically two to three weeks later. At the second appointment, the temporary prosthetic is removed, the permanent restoration is fitted and checked for proper bite alignment, and then permanently cemented into place.
Material Options and Longevity
Dental crowns and bridges are fabricated from several materials, offering a balance of durability and aesthetic appeal. Common choices include all-porcelain or ceramic, porcelain fused to metal (PFM), and metal alloys, often containing gold. All-ceramic options, such as zirconia or lithium disilicate, provide the most natural appearance and are chosen for front teeth due to their color-matching capabilities.
Metal alloys, including gold, are strong and resistant to fracture, making them a preferred option for restorations on back molars where chewing forces are highest. Porcelain fused to metal restorations offer a blend of both, with a metal substructure for strength and a porcelain layer on the outside for a more natural look.
The lifespan of these restorations varies depending on the material, location in the mouth, and the patient’s oral hygiene habits. Crowns and bridges can last anywhere from 5 to 15 years, often longer with proper care. To maximize longevity, patients must maintain meticulous brushing and flossing, use specialized floss threaders to clean underneath a dental bridge, and attend routine dental check-ups.