Dental fillings, known professionally as dental restorations, are a common treatment used to repair teeth damaged by decay or trauma. They restore the tooth’s form, function, and integrity after compromised material has been removed. While durable, these restorations are not permanent fixtures. Over time, all fillings will eventually wear down, become compromised, or fail, making replacement a normal part of long-term dental care.
Factors Influencing Filling Lifespan
The expected longevity of a dental filling depends heavily on the material used. Gold fillings often exhibit the longest lifespan, frequently lasting 20 years or more due to their strength, durability, and resistance to corrosion and fracture. Amalgam, or silver fillings, are also highly durable, typically lasting between 10 and 15 years, as they withstand heavy chewing forces well.
Composite resin fillings are tooth-colored and popular for aesthetic reasons, but they have a shorter average lifespan, usually lasting between 5 and 10 years. This material is less durable than metal options and is more susceptible to wear in areas experiencing significant biting pressure. Glass ionomer fillings are used for smaller restorations because they release fluoride, but they are the least durable, lasting around five to seven years.
Beyond the material, the location of the filling significantly impacts its longevity. Fillings in molars bear the brunt of chewing forces and are subjected to much higher stress than those on front teeth. Patient habits, such as teeth grinding (bruxism) or clenching, introduce excessive pressure that accelerates wear and eventual failure. Poor oral hygiene can shorten a filling’s lifespan by allowing bacteria to accumulate around its edges.
Physical Signs a Filling Needs Replacement
A failing dental filling often gives physical signals indicating the need for professional evaluation. One common sign is increased sensitivity or pain in the filled tooth, especially when exposed to hot or cold temperatures or when biting down. This discomfort indicates the filling is no longer providing an intact seal, allowing stimuli to reach the nerve tissue.
Visible damage to the filling material itself is another clear indicator of failure. Patients may notice a crack, chip, or fracture in the filling, sometimes feeling a piece break off while eating. Fillings that develop a rough texture or sharp edges signal that the material is wearing down or that the seal between the filling and the tooth has been compromised.
Discoloration around the edges of the restoration, appearing as a dark line or shadow, can suggest recurrent decay underneath the filling. A compromised or loose filling may also lead to food frequently getting trapped, or a feeling of movement or looseness. Floss that repeatedly shreds or catches next to a filled tooth can also be a subtle sign of a rough or chipped margin.
Mechanisms of Filling Failure
Fillings ultimately fail due to mechanical stress and biological processes that break down the integrity of the restoration-to-tooth interface. The most common mechanism is secondary, or recurrent, decay, which develops beneath or around the margins of the existing filling. This occurs when microleakage, tiny gaps between the filling and the tooth structure, allows oral bacteria and their acidic byproducts to seep into the tooth.
Marginal breakdown refers to the deterioration of the seal where the filling meets the natural tooth. Over time, the materials can shrink, corrode, or simply wash out. Once this seal is broken, the filling can no longer effectively prevent bacteria from colonizing the prepared cavity beneath it.
General wear and tear from chewing forces and abrasion contribute significantly to failure, especially in composite resin. Excessive forces, such as those generated by bruxism, can cause micro-fractures to propagate through the filling or surrounding tooth structure. This can result in a chipped restoration or a fracture of a cusp. Larger fillings are inherently more susceptible to failure than smaller ones.
What Happens During a Filling Replacement
Replacing a failed filling begins with a thorough examination, often including dental X-rays to assess the extent of decay beneath the existing restoration. Once replacement is confirmed, the dentist administers a local anesthetic to numb the area, ensuring the patient remains comfortable.
Using a dental drill, the old filling material is carefully removed, along with any secondary decay that has formed beneath it. The dentist ensures all diseased tissue is excavated to create a clean, healthy surface for the new restoration. The cavity preparation is then cleaned and shaped to optimize the retention and stability of the new filling material.
The new material, which may be a different type than the original, is placed into the prepared cavity and molded to match the natural contours of the tooth. For composite fillings, a curing light hardens the resin material. The final steps involve polishing the new restoration and adjusting the bite. If the underlying decay is too extensive, a larger restoration, such as an inlay, onlay, or a full crown, may be necessary.