A dental crown, often called a cap, is a custom restoration that completely covers the entire visible portion of a damaged tooth down to the gum line. Its purpose is to restore the tooth’s original shape, size, and strength while improving its appearance. Unlike a filling, a crown provides full coverage, acting as a protective shell to prevent further breakdown. This restoration is used when damage is too extensive to be repaired by less invasive means, safeguarding the remaining natural tooth.
When Extensive Damage Requires Protection
A crown becomes necessary when the remaining tooth structure is too weak to withstand normal biting and chewing forces. This often occurs when a tooth has a very large filling covering more than two-thirds of its width, leaving the surrounding walls fragile and prone to fracture. Reinforcing the entire structure with a crown is safer than relying on the compromised tooth integrity.
Fractured or cracked teeth also frequently require a crown to prevent the damage from spreading, especially when a crack extends below the gum line or compromises the cusps (biting points). A crown holds the compromised tooth together, preventing the crack from propagating and potentially leading to infection or tooth loss. Additionally, a crown is the final, visible component placed on top of a dental implant, restoring the appearance and function of a missing tooth.
Crowns Following Root Canal Therapy
Teeth that have undergone endodontic treatment (a root canal) often require a crown, even if they appear structurally sound immediately after the procedure. The root canal process involves creating an access opening and removing the inner pulp tissue, which significantly reduces the tooth’s internal strength. This procedure, combined with the initial decay or trauma, leaves the tooth more vulnerable to fracture.
Root canal treated teeth are sometimes described as brittle because they lose natural moisture and flexibility after pulp removal. Placing a crown over the treated tooth provides a complete seal and acts as a barrier, dispersing chewing forces and preventing the tooth from cracking. This protection is important for back teeth, such as molars, which absorb the greatest biting force.
Addressing Chronic Wear and Enamel Loss
Crowns are also used to address issues arising from slow, long-term degradation rather than sudden trauma or decay. Severe tooth wear, often caused by bruxism (chronic grinding or clenching), can erode the enamel and flatten the biting surfaces of the teeth. This excessive wear can lead to sensitivity, an altered bite, and a significant loss of the tooth’s vertical dimension.
In cases of advanced wear or acid erosion from dietary habits or severe acid reflux, crowns are necessary to rebuild the tooth’s structure and restore the proper function of the bite. By capping the worn teeth, the crown provides a new, durable surface that protects the remaining natural tooth from further abrasion. This approach is often part of a larger treatment plan aimed at restoring the entire bite, especially when multiple teeth have been affected by years of grinding.
Factors Influencing Crown Material Selection
Once the need for a crown is confirmed, the selection of the restorative material depends on a balance between strength, aesthetics, and the tooth’s location in the mouth. For front teeth, aesthetics are generally the main priority, leading to the frequent use of all-ceramic or porcelain crowns, which closely mimic the color and light-reflecting properties of natural enamel. However, all-porcelain materials are typically more prone to chipping than metal options, making them less suitable for individuals with a heavy bite or bruxism.
Teeth in the back of the mouth, such as molars, require materials that can withstand tremendous chewing forces; for these teeth, strength is the primary concern. Options like gold or metal alloys offer superior durability and minimal wear on the opposing natural teeth. Zirconia, a highly durable ceramic material, has become a popular choice for back teeth, providing both significant strength and a tooth-colored appearance. Porcelain-fused-to-metal (PFM) crowns offer a compromise, using a metal core for strength and a porcelain layer for aesthetics, making them a versatile choice for various locations in the mouth.