Porcelain-fused-to-metal (PFM) crowns combine the strength of a metal alloy base with the natural appearance of porcelain. The design uses a thin metal coping to cover the prepared tooth structure, with a layer of tooth-colored porcelain baked onto the exterior surface. PFM crowns restore a damaged tooth’s original shape, size, and strength. Understanding the long-term viability of this restoration is important for patients considering this treatment option.
The Typical Lifespan of PFM Crowns
PFM crowns are recognized for their balance of durability and aesthetics. The expected average lifespan generally falls within a range of 10 to 15 years, though many crowns can last longer than 20 years with exceptional care. PFM crowns are reliable because the metal substructure provides high fracture resistance, allowing the restoration to withstand significant biting forces. The porcelain layer achieves a desirable tooth-like appearance.
What Determines Longevity
The duration of a PFM crown is highly dependent on variables that influence wear and tear. One significant factor is the patient’s habits, particularly chronic teeth grinding or clenching (bruxism). This intense pressure accelerates the wear of the porcelain layer and compromises the crown’s integrity. Habits such as chewing on ice or using teeth as tools can also cause premature chipping or fracturing of the porcelain surface.
The crown’s position within the mouth also dictates its longevity, as crowns on back molars experience significantly more chewing force than those on front teeth. The quality of the underlying dental work, including the preparation of the tooth and the precision of the crown’s fit, is also crucial.
A crown with an ill-fitting margin can create a small gap where bacteria accumulate, potentially leading to decay near the edge of the restoration. Overall oral hygiene levels are a major determinant. If plaque is not consistently removed, the underlying tooth structure can develop secondary decay, which weakens the tooth and necessitates replacement. Gum recession surrounding the crown can also expose the margin and compromise the restoration’s seal.
Recognizing When a Crown Needs Replacement
Patients should be aware of physical signs and symptoms that signal a PFM crown is failing and requires professional evaluation. One common issue is the chipping or fracturing of the porcelain layer, which exposes the underlying metal framework. Even a small crack compromises the crown’s protective seal, leading to sensitivity and decay.
A noticeable dark line visible at the gum line often occurs due to gum recession that exposes the metal margin. This indicates the seal between the crown and the tooth may no longer be intact. Chronic sensitivity or pain in the crowned tooth, especially when biting down or reacting to hot or cold temperatures, suggests decay has formed underneath or the nerve is irritated.
A crown that feels loose or unstable indicates that the bonding material has degraded. Looseness allows bacteria to enter and thrive, increasing the risk of infection. If food frequently gets caught around the base of the crown, it suggests an ill-fitting margin has developed that needs to be addressed.
Daily Care to Extend Crown Life
Several preventative actions can be taken daily to help ensure a PFM crown lasts as long as possible. Maintaining meticulous oral hygiene is crucial, involving brushing at least twice daily using a soft-bristled brush and fluoride toothpaste. Attention should be given to gently cleaning the area where the crown meets the gum line to prevent decay at the margin.
Flossing around the crown once per day is equally important, often requiring aids like floss threaders or a water flosser to clean beneath the crown’s edges. Individuals who clench or grind their teeth (bruxism) should obtain a custom-fitted night guard from their dentist. This appliance protects the porcelain surface from intense, damaging forces.
Regular dental checkups and professional cleanings are necessary for monitoring the restoration’s condition. The dentist can assess the crown margins for signs of leakage, decay, or wear that may not be apparent to the patient. Avoiding hard or sticky foods, such as caramel or ice, also prevents the crown from chipping or being pulled out of place.