Dental fillings are restorative materials used to repair tooth structure damaged by decay or fracture, sealing the tooth from further bacterial invasion. While fillings are designed to be durable, they are not permanent. They eventually require replacement because the restoration or the surrounding tooth fails due to wear, breakdown, or new decay.
The Lifespan of Dental Fillings
The expected lifespan of a dental filling depends on the material chosen, the size of the restoration, and its location within the mouth. Longevity varies widely across common materials, offering different balances of durability and aesthetic appeal. Amalgam, often called silver fillings, is known for its strength and can last an average of 10 to 15 years, sometimes exceeding 16 years in posterior teeth.
Composite resin fillings, the tooth-colored option, are less durable under heavy chewing forces and typically last between five and ten years. These materials are best suited for smaller cavities or areas where aesthetics are a primary concern. Gold and ceramic materials offer superior longevity, frequently lasting 15 to 20 years or more, but they are generally more expensive and require different placement techniques.
The size of the filling is a major factor, as a restoration covering multiple surfaces of a tooth is under greater stress than a small, single-surface filling. Patient habits, such as chronic tooth grinding (bruxism) or frequent consumption of hard or sticky foods, also accelerate the rate at which any dental restoration will wear down.
Causes of Filling Deterioration
Fillings fail through specific deterioration mechanisms that compromise the integrity of the tooth-restoration interface. The most frequent reason for replacement is secondary decay, which occurs when bacteria infiltrate the space beneath or around the existing restoration. This happens because the seal between the filling material and the surrounding tooth structure weakens over time, creating a microscopic gap.
This separation is called marginal breakdown, allowing acids and bacteria to seep into the vulnerable tooth tissue. Once established, this new decay can quickly spread inward, often remaining hidden. Another cause of failure is material fracture or wear, where the mechanical forces of chewing and clenching cause the filling to chip, crack, or flatten.
Amalgam fillings are more prone to fracture failure, while composite resins are more likely to fail due to secondary decay or gradual dissolution of the resin matrix. The constant expansion and contraction of the material due to temperature changes from hot and cold foods also place strain on the restoration, contributing to the development of micro-cracks.
What Happens When a Filling Fails
A failing filling often presents with subtle signs that a patient might overlook, emphasizing the need for regular dental check-ups. One common symptom is increased sensitivity to hot and cold temperatures or sweet foods, suggesting the protective seal has been compromised and stimuli are reaching the nerve. Pain or discomfort when biting down can indicate that the filling has shifted or a fracture has occurred in the restoration or the tooth itself.
Visible changes such as darkening or discoloration around the margins of the filling can signal bacterial leakage and active decay developing underneath the material. Patients may also notice a rough edge or a jagged surface with their tongue, which can be a sign of chipping or loss of a section of the filling. If a dentist detects a failing filling through visual inspection, probing the margins, or X-rays, intervention is necessary.
Allowing a failed filling to remain in place risks the progression of decay, which can lead to more extensive and costly treatments. Early replacement can usually be managed with a new, simple filling to restore the tooth structure. However, if the decay has penetrated deeply, the necessary treatment may escalate to a crown to cover and protect the weakened tooth, or even a root canal procedure if the infection reaches the dental pulp.