Composite Resin vs. Amalgam: Which One to Choose?

Even with the best oral hygiene habits, tooth decay can occur. Luckily, treatment for cavities is simple—but choosing the right filling option is crucial to ensure the health of your teeth for years to come. From amalgam to mercury-free fillings, dental professionals have various materials to choose from to restore the health of your teeth.

While both types of fillings have benefits and disadvantages, one or the other may be better depending on your circumstances.

What Are Amalgam Fillings?

Amalgam fillings are durable, silver-colored dental materials made from a mixture of metals. They’re commonly used for back teeth due to the belief that these metal restorations are more long-lasting and resistant to wear.

Moreover, their lack of aesthetic appeal can be counteracted as these teeth aren’t easily visible.

Some of the metals contained in amalgam fillings include:

• Mercury (50%): Due to its stability, moldability, and capacity to fuse other metals, mercury is the main ingredient in amalgam fillings. Although mercury is toxic in its pure form, it is considered safe in dental amalgam fillings because it hardens when combined with other powdered metals.
• Silver (22–32%): Silver is added to increase the amalgam mixture's strength and durability. It improves the material's resistance to corrosion and lends the filling its distinctive silver-gray hue.
• Tin (14–30%): Tin makes the amalgam more workable and malleable, facilitating the filling's placement in the cavity. When exposed to temperature changes in the mouth, it also helps the alloy expand and contract without breaking.
• Copper (6–14%): Copper is added to improve the amalgam's strength and resistance to wear. It also lessens the possibility of corrosion, extending the filling's lifespan.
• Other Elements: Trace amounts of palladium, zinc, or other metals may be added to improve the material's qualities even further.

What Are Composite Resin Fillings?

Composite resin fillings, also known as tooth-colored fillings or mercury-free fillings, are a combination of plastic resin and powdered glass used to restore teeth’s appearance and function.

Unlike amalgam, they come in various shades of white, offering a natural look that blends in with the rest of your teeth. For that reason, composite resin can also be used in cosmetic treatments, such as dental bonding.

Comparing Composite Resin and Amalgam Fillings

There’s no definite consensus, even among the dental community, about which to choose between composite resin and amalgam. Some dentists prefer the natural look of composite resin, while others opt for amalgam due to its supposed durability.

For that reason, patients must inform themselves about the benefits and disadvantages of each procedure to make a knowledgeable decision. Some important factors to consider when comparing composite and amalgam include:

Appearance

Composite resin fillings are natural and aesthetic. These fillings match the color of the natural tooth, making them a great option for front teeth or any visible areas.

On the other hand, amalgam fillings have a noticeable silver color, so they’re not recommended for your front teeth.

Bonding and Natural Teeth Protection

Mercury-free fillings bond directly to the tooth structure, which can help support and strengthen the remaining tooth. Therefore, they also require less removal of healthy tooth structure during placement.

Mercury fillings don’t require a perfectly dry environment for bonding, which is why they’re easier to place. However, they require the removal of a more healthy tooth structure, leaving it weakened. Additionally, they can cause fractures in the tooth due to their rigidity.

Dental Sensitivity

Metals are sensitive to temperature, meaning they expand and contract with temperature changes. This can cause sensitivity, especially in fillings close to the tooth root, and may lead to cracks or leaks over time.

Composite resin is less temperature-sensitive than amalgam because it lacks metal, meaning it's less likely to expand/contract with hot/cold.

Toxicity

The biggest downside to amalgam fillings is that they contain mercury, a dangerous heavy metal that can cause tremors, memory loss, mind fog, renal failure, and even more serious issues. According to the ADA, mercury fillings are completely safe.

However, studies show that bodies with amalgam fillings have noticeably more mercury in their blood than bodies without them.

On the other hand, the materials in composite resin are completely safe for the body and don’t pose any risks over time.

Tendency to Stains

Due to its clear color, composite resin fillings may stain over time, especially from colored foods or drinks like coffee, tea, and berries.

However, amalgam fillings are a noticeable grey color, which is why stains are unnoticeable and/or irrelevant.

Durability

Even today, there’s a widespread belief that amalgam fillings are more durable than composite resin ones due to the metal’s durability. However, recent studies help dispel this misconception.

In a study, researchers assessed the longevity of posterior (back of the mouth) fillings in more than 650,000 patients. Failure was defined as having to have a composite or amalgam filling redone, having the tooth extracted, or having its roots canaled. A filling was deemed successful if it avoided these outcomes.

Data analysis revealed that less than 12% of the composite fillings failed, while 17.5% of the mercury fillings did. This could be due to a number of factors, including metals' propensity to fracture teeth and their inherent ability to expand and contract in response to temperature changes.

Nevertheless, it shows that mercury fillings aren't as durable as composite resin ones.

Restore Your Smile with Mercury-Free Fillings

Like all medical specialties, dentistry is always evolving. Although amalgam fillings were once the preferred method for repairing cavities, particularly in the back teeth, composite resin has since replaced amalgam in this capacity.

Composite restorations, instead of metal-based ones, are long-lasting, natural-looking, and free of harmful substances that could endanger your general health. For that reason, we promote the use of this material here at Dental Healing Arts. Our group is dedicated to promoting biocompatible dental procedures that safeguard not just your smile but also your general well-being.  

If you’d like to learn more about biocompatible dentistry or have a mercury filling you’d like to remove safely, contact us today to schedule an appointment!