Dental fillings are common restorations used to repair teeth damaged by decay or minor fractures, restoring their function and appearance. While durable, these materials are not permanent and can crack over time. Understanding these factors helps maintain oral health and prolong the life of dental restorations.
Filling Material Types
The specific material used for a dental filling significantly influences its susceptibility to cracking. Amalgam fillings, often called “silver fillings,” are a blend of metals known for strength and durability, especially against chewing forces. Amalgam does not bond directly to the tooth, requiring more tooth material removal for retention.
Composite resin fillings are tooth-colored, made from an acrylic and ceramic mixture, and bond directly to the tooth. While aesthetic, they are less rigid than amalgam and more susceptible to wear and chipping under heavy biting forces. Gold fillings, made from a gold alloy, are highly durable and biocompatible, often lasting for decades. Gold’s ductility allows it to withstand chewing forces without fracturing, though it is more expensive. Porcelain or ceramic fillings are custom-made and bonded to the tooth, offering good aesthetics and stain resistance. These materials are hard but can be brittle, prone to cracking under sudden impacts.
Chewing Forces and Habits
Direct mechanical stress from daily chewing activities is a primary reason dental fillings crack. Biting on hard foods, such as ice, nuts, or hard candies, exerts concentrated force on fillings, potentially leading to immediate fractures or micro-fractures that worsen over time. These items can cause fillings to break or dislodge.
Parafunctional habits like teeth grinding (bruxism) and clenching place continuous, excessive stress on dental restorations. Bruxism, which often occurs unconsciously during sleep, involves repetitive clenching or grinding of the teeth, leading to significant wear and tear on both natural teeth and fillings. This constant, high-pressure activity can cause microscopic cracks to form and propagate within the filling material, ultimately resulting in larger cracks or even complete failure. The sustained force from these habits can compromise the structural integrity of the filling, making it more vulnerable to damage.
Age and Wear of Fillings
Dental fillings have a finite lifespan and are subject to natural degradation over time. The constant exposure to the oral environment, including chewing forces, temperature fluctuations, and chemical interactions, contributes to the gradual wear and breakdown of filling materials. Over years of use, materials can lose their original properties, becoming less resilient and more brittle.
For example, amalgam fillings can experience marginal breakdown or “creep,” a slow deformation under continuous stress, which can lead to gaps and weakening over time. Composite resins can wear down from chewing and may lose their bond with the tooth, creating pathways for bacteria. This natural aging process makes older fillings more susceptible to cracking, even under normal chewing forces that a newer, intact filling would easily withstand. Regular dental check-ups are important to monitor the condition of aging fillings and identify potential issues before they escalate.
Tooth Structure Issues
Problems with the underlying tooth structure itself can significantly contribute to filling cracks. New tooth decay forming beneath or around an existing filling, known as recurrent decay, weakens the surrounding tooth material. This decay removes the necessary support for the filling, making both the tooth and the restoration prone to fracture. When the seal between the filling and the tooth breaks down, bacteria can infiltrate, causing further decay and undermining the filling’s stability.
Existing cracks within the tooth can also extend into or around a filling, leading to its failure. These cracks can originate from trauma, excessive chewing forces, or even large fillings themselves which can weaken the tooth’s natural structure. If a substantial portion of the tooth was removed during the initial filling procedure, the remaining tooth walls might be too thin to adequately support the filling, leaving it vulnerable to cracking under pressure. This compromised foundation makes the entire restored tooth unit unstable, increasing the risk of the filling cracking.
Temperature Changes
The mouth experiences frequent and sometimes rapid temperature fluctuations, such as when consuming hot coffee followed by cold water. This can cause dental materials to expand and contract, a phenomenon known as thermal expansion and contraction. Different materials, including the tooth and the filling, have varying rates of expansion and contraction.
When a filling and the surrounding tooth expand and contract at different rates, it creates internal stresses within the tooth-filling complex. Over time, these repeated stresses can lead to the formation of microscopic cracks, particularly at the interface between the filling and the tooth. While this is less often the sole cause of a major crack, it contributes to the overall fatigue of the filling and tooth structure, making them more vulnerable to cracking from other forces. Amalgam fillings, being metallic, are particularly susceptible to these thermal changes due to their higher thermal conductivity compared to natural tooth structure.