The choice of material for restoring a tooth damaged by decay centers on two primary types of dental fillings: amalgam and composite resin. Amalgam, often called a “silver filling,” is a mixture of metals that has been used by dentists for over a century. Composite resin is a newer, tooth-colored option. Both materials seal a cavity to prevent further decay and restore the tooth’s function, and understanding their differences is necessary for determining the most suitable material.
Material Composition and Health Implications
Amalgam fillings are composed of a metallic alloy powder mixed with liquid elemental mercury, which typically makes up about 50% of the final material by weight. The alloy powder consists primarily of silver, tin, and copper, which bond with the mercury to form a strong, durable restoration. The presence of elemental mercury has generated debate due to its ability to release minute amounts of mercury vapor during chewing or brushing.
The U.S. Food and Drug Administration (FDA) states that mercury exposure from amalgam is generally low and does not lead to negative health effects in the general population. However, the FDA recommends that certain high-risk groups should use non-mercury alternatives like composite resin. These groups include pregnant women, nursing women, children, and people with neurological disease or impaired kidney function. Composite resin is made from an acrylic resin matrix containing tiny glass or quartz filler particles, and it is entirely mercury-free.
Some composite resins utilize derivatives of Bisphenol A (BPA), such as Bis-GMA, which has raised concerns because BPA is an endocrine-disrupting compound. Research suggests that exposure to BPA from these fillings is minimal and occurs mainly during the initial placement process. Many manufacturers now offer BPA-free materials to address patient concerns, and major health organizations consider the amount released to be negligible.
Placement Procedure and Aesthetic Outcomes
The method of preparing the tooth and placing the filling differs significantly between the two materials. Amalgam preparation is mechanical, requiring the dentist to remove a larger amount of healthy tooth structure to create undercuts that physically hold the filling in place. The amalgam is packed into the prepared cavity, where it then hardens quickly. The noticeable silver or dark gray color of amalgam fillings is their most significant aesthetic drawback, making them highly visible in the mouth.
The procedure for a composite resin filling is more technique-sensitive and requires a completely dry field to ensure success. The tooth is first etched with an acid gel to create microscopic pores, and then a bonding agent is applied to establish a chemical link with the natural tooth structure. The composite paste is layered into the cavity and cured using a specialized blue light. This bonding process allows for a more conservative approach, preserving more healthy tooth structure by only removing the decayed portion. Composite fillings offer superior aesthetic outcomes because the resin can be precisely shade-matched, rendering the restoration nearly invisible.
Durability, Wear Resistance, and Longevity
Amalgam is known for its high strength and resilience, making it an excellent material for bearing heavy chewing forces in the posterior teeth. Its robust nature and resistance to wear allow amalgam fillings to last typically between 10 to 15 years, often longer. Amalgam is also less sensitive to moisture during placement, contributing to its reliability in challenging oral environments. However, amalgam does not bond to the tooth and can expand and contract with temperature changes, which may lead to micro-fractures in the surrounding tooth structure over many years.
Composite resin fillings have a more moderate lifespan, generally lasting between five and ten years, though newer formulations have improved performance. They are more susceptible to wear than amalgam, especially in large restorations on molars that experience high chewing pressure. The longevity of composite restorations depends highly on the skill of the dentist and the patient’s oral hygiene habits. The primary reason for failure is often secondary decay forming around the edges (marginal leakage) or the material wearing down over time.
Comparative Cost and Insurance Coverage
Composite resin fillings are consistently more expensive than amalgam fillings. This difference is attributed to the higher material cost and the increased time and precision needed for the placement procedure. On average, an amalgam filling costs between $50 and $150 per tooth, while a composite filling typically ranges from $90 to $250 per tooth, though costs vary widely by location and complexity. Dental insurance policies often influence the financial aspect, as they traditionally consider amalgam the standard, basic restoration. Many plans provide full coverage for amalgam but may only cover a portion of the cost for composite fillings.
For restorations on posterior teeth, some insurers cover the cost only up to the price of an amalgam filling, leaving the patient responsible for the difference for composite. Patients often prioritize the budget-friendly, durable option of amalgam for unseen back teeth, while opting for the aesthetic composite for visible teeth. The overall value should also consider amalgam’s longer lifespan in high-stress areas, which may lead to fewer replacements and lower long-term costs.