A dental filling is a restorative treatment used to repair tooth structure damaged by decay, known as a cavity. The primary function of a filling is to seal the area, preventing bacteria from entering and causing further deterioration of the tooth’s interior layers. The appearance of a filled cavity varies widely depending on the material used and its location within the mouth.
The Appearance of Standard Filling Materials
The two most common materials used for dental restorations have distinct visual characteristics. Amalgam fillings are composed of a blend of metals, including silver, tin, copper, and mercury, giving them a noticeable metallic appearance. Often called “silver fillings,” they present as a dark gray or silver color that stands out against the natural white of the tooth. Because of their visibility, amalgam is reserved for molars and premolars in the back of the mouth where chewing forces are highest.
Composite resin fillings, also known as “tooth-colored” or “white” fillings, are made from a mixture of acrylic and ceramic or glass-like particles. These materials are designed to be shade-matched precisely to the surrounding enamel, allowing the restoration to blend seamlessly and become nearly invisible. Due to this aesthetic advantage, composite resins are the preferred choice for front teeth and other highly visible areas. The surface of a new composite filling is smooth and uniform, mimicking the texture of natural tooth enamel.
Distinguishing a Filling From Decay or Staining
Distinguishing between an existing restoration, a new stain, or developing decay requires careful observation. Dental stains from coffee, tea, or tobacco usually present as superficial discoloration or uniform changes in color across the tooth surface. These stains do not compromise the tooth’s underlying structure and lack the sharp, defined borders of a filling. A filling, by contrast, occupies a specific, carved-out space where decayed tissue was removed, creating a distinct, firm margin where the material meets the natural tooth.
New decay, which is a structural breach in the enamel, appears as a localized dark spot, pit, or hole. While a stain may be surface-level discoloration, active decay often looks dark and dull, and may feel rough or sticky to a dental probe. A common sign of a new problem is a dark shadow or line forming directly around the border of an existing filling, suggesting bacteria have begun to penetrate the margin. A healthy filling should maintain a firm, continuous surface where it meets the tooth.
Recognizing When a Filling Needs Attention
A filling that is failing or deteriorating will show specific visual cues that signal the need for professional assessment. Chips or cracks within the filling material itself can occur from wear and tear, especially on biting surfaces. Visible wear, where the material appears flattened or eroded, is another sign that the filling is no longer providing adequate protection.
A more serious sign is marginal breakdown, where a dark line or gap forms at the junction between the filling and the natural tooth structure. This gap indicates that the seal has been compromised, allowing moisture and bacteria to leak underneath the filling, potentially causing secondary decay. This secondary decay can sometimes present as a dark halo around the perimeter of the existing restoration. These visual signs of failure are often accompanied by symptoms such as increased sensitivity to hot or cold temperatures, or pain when biting down, requiring immediate dental consultation.