A dental crown is a custom-made cap placed over a damaged tooth to restore its shape, size, and strength. While crowns provide a protective shield, they are not indestructible and can develop a hole or crack. Whether the crown can be repaired or requires replacement depends heavily on the size and location of the defect, and the material it is made from.
Common Causes of Crown Damage
A hole or defect in a crown often results from mechanical forces or structural compromise over time. One common cause is physical wear, which includes teeth grinding, known as bruxism, or biting on exceptionally hard objects. This constant, excessive force can lead to chipping or fracturing, particularly on the chewing surface of the crown.
Another, less common cause of a hole is an iatrogenic perforation, which occurs accidentally during a subsequent dental procedure. For example, a dentist may need to drill an access hole through the crown to perform a root canal on the tooth underneath. If this access hole is not sealed properly afterward, it can act as a defect. The integrity of the crown can also be compromised by marginal failure, where the seal between the crown and the natural tooth weakens, allowing bacteria to cause decay in the underlying tooth structure.
Repairing the Crown: Feasibility and Methods
Repairing a crown instead of replacing it is possible for small, isolated defects, though it is often considered a temporary solution. The viability of a repair depends significantly on the crown’s material and the extent of the damage. Porcelain or all-ceramic crowns are the most amenable to repair, as bonding agents adhere more effectively to these surfaces than to metal or zirconia.
For minor chips or small perforations, the repair involves using specialized dental materials to patch the defect. Dentists frequently use composite resin, a tooth-colored material that can be color-matched to the crown for an aesthetic fix. The resin is applied to the damaged area, shaped, and then hardened using a specialized curing light.
Glass ionomer cement is another material used for crown repair, particularly in non-load-bearing areas. This material chemically bonds to the tooth structure and releases fluoride, which offers a localized preventative benefit against further decay. While composite resin generally offers superior strength and aesthetics, glass ionomer is sometimes preferred for its protective properties in certain clinical situations. Regardless of the material, a repair is only successful if the hole is small and does not compromise the overall structural stability of the restoration.
When Replacement is the Only Option
A complete crown replacement becomes necessary when the damage is too extensive to be reliably repaired or when the underlying tooth is compromised. Large fractures or holes that significantly compromise the structural integrity of the crown require replacement because a simple patch will not withstand the forces of chewing. Replacement is also the only viable option if significant recurrent decay is found beneath the existing crown, as the crown must be removed to treat the underlying tooth structure.
A poor fit or seal between the crown and the tooth margin also necessitates replacement, as this gap allows for the ingress of bacteria and fluids. Since the average lifespan of a crown is ten to fifteen years, older crowns prone to failure often require replacement rather than repair. The replacement process involves removing the damaged crown, preparing the tooth surface, taking a new impression, and placing a temporary crown until the custom-made restoration is ready.