What is Amalgam? A Review of Its Advantages, Disadvantages, and Comparison with Composite

When was the first time you became curious about dental filling materials?

In the dental filling process, specialists use a material called amalgam, one of the oldest discoveries in dentistry. This durable material is a combination of metals such as mercury, silver, tin, and copper, and has been used for years in the field of dentistry, especially for restoring cavities in the back teeth.

Despite concerns regarding the presence of mercury in amalgam, the World Health Organization and dental research centers continue to consider amalgam safe and effective. In this article, we will scientifically explore everything you need to know about amalgam, from its benefits and drawbacks to its applications and alternatives.

According to the World Health Organization (WHO), more than 100 countries worldwide use amalgam as the main solution for restoring posterior teeth. Therefore, part of the answer to the question "What is amalgam, and how safe is it for dental restorations?" is related to global dental standards.

 

What is Dental Amalgam?

Dental amalgam is a silver or gray-colored material composed of about half powdered alloys of silver, tin, copper, and zinc, with the other half being liquid mercury. A key characteristic of this compound, which is mixed at the dental office, is its rapid moldability after mixing.

This allows it to be easily placed into the cavity and harden within a few minutes. The final strength and peak hardness of amalgam gradually develop over 24 hours.

What makes amalgam a unique and almost irreplaceable material is the chemical reaction of mercury with the powdered metals. This reaction forms a solid, homogeneous structure that is highly resistant to pressure (chewing), which has made amalgam the best option for restoring back teeth (molars) for decades.

In terms of appearance, amalgam, unlike white fillings (composites), is not tooth-colored. This has led to its lesser use for front teeth or aesthetic zones, but it remains the preferred choice for restoring posterior teeth.

 

 

Chemical Composition of Amalgam and Its Types

Earlier, we mentioned the metals that make up amalgam. Now, let's take a look at the ratio of these metals in amalgam, which is typically as follows:

• About 50% mercury
  
  
• 35% silver
  
  
• 13% tin
  
  
• 2% copper and other metals
  
  

Interestingly, amalgams are categorized into two types based on their copper content: low-copper amalgam and high-copper amalgam. The second type, high-copper amalgam, offers better durability and performance in the oral environment.

According to the standards of international organizations such as the ADA (American Dental Association), the compositions of new and improved amalgams have minimized mercury release, making them completely safe for use in healthy patients.

 

Advantages of Dental Amalgam

Due to its unique physical and clinical properties, and its ideal performance under heavy pressure, amalgam is a reliable option for dental restoration and filling. Below are the benefits of amalgam, which are generally related to its stability:

• Resistance to High Chewing Pressures
  The dense, metallic structure of amalgam makes it highly resistant to repeated pressure from chewing and friction with food. This feature is particularly important for patients who suffer from bruxism (teeth grinding) or have a habit of chewing hard substances like ice.
  
  
• High Durability in Oral Environmental Conditions
  Some restorative materials are highly vulnerable and react to changes in the mouth's pH or temperature fluctuations. Unlike these materials, amalgam has stable properties and does not get damaged even in acidic conditions or when exposed to hot or cold beverages.
  
  
• Moisture Tolerance During Placement
  One common issue with white restorative materials (such as composites) is that the oral environment must be completely dry. In situations where controlling moisture in the mouth is challenging, amalgam performs well, as the area being restored does not need to be dry for proper application.
  
  

 

• Quick Treatment Process
  The process of placing amalgam takes less time compared to many other materials. This is particularly beneficial for young children or patients with dental anxiety, as it makes the procedure less lengthy and stressful.
  
  
• Ideal for Extensive and Deep Restorations
  In cases where a large portion of the tooth crown is lost or there is extensive tooth decay, amalgam is an effective option for rebuilding the tooth structure due to its mechanical properties. It can be shaped as needed and securely fixed in place.
  
  
• Dimension Stability Over Time
  Once set, amalgam does not undergo significant contraction or expansion, maintaining a proper bond with the tooth walls over the long term. This is especially important for reducing the risk of bacterial leakage.
  
  
• Stability Without the Need for Adhesive Bonding
  Unlike restorative materials such as composites, which require a chemical bond (usually with adhesive) to stick to tooth tissue, amalgam bonds mechanically. It stays in place within the cavity, ensuring reliable performance even if the surrounding enamel is weak.

 

 

What Are the Disadvantages of Amalgam: Concerns and Drawbacks

Alongside the technical and functional advantages of amalgam, there are concerns related to its aesthetic and safety aspects. If you are one of those patients who care about all aspects of treatment, it's important to be aware of the disadvantages or, more accurately, the limitations of amalgam.

• Aesthetic Impact
  The color of amalgam is influenced by its metal components, and it does not match the color of natural teeth. This becomes visible when the mouth is opened or when smiling, which may be considered a downside for patients who prioritize the aesthetic appearance of their teeth and smile.
  
  
• Potential for Cracking in the Tooth
  The physical properties of amalgam, along with its lack of chemical bonding to the tooth structure, may cause expansion pressures over time that result in microscopic cracks in the remaining tooth walls. If the dental professional does not design the restoration properly, this risk may increase.
  
  
• Concerns About Mercury's Harm
  Although the amount of mercury in amalgam is controlled and its release is considered safe and within permissible limits, some patients and sensitive groups remain concerned about the presence of mercury, even in small amounts.
  
  
• Legal Restrictions or Bans in Some Countries
  Countries such as Sweden, Norway, Germany, and some other European nations have restricted or banned the use of amalgam, either entirely or for specific groups such as pregnant women and children. These decisions have sometimes been precautionary and, in some cases, driven by environmental concerns.
  
  
• Conflicting Opinions in Clinical Studies
  While reputable organizations like the ADA and WHO have confirmed the safety of amalgam, some independent studies regarding its long-term effects on the nervous system or the body's immune response to mercury vapor have presented conflicting opinions. These differing views have led some patients to be cautious about using amalgam for dental restorations, and they may refuse its use.
  
  
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Amalgam vs. Composite: A Comparison of Two Dental Restorative Materials

The choice between amalgam and composite depends on various factors, and the preferred option may vary for each patient. The location of the tooth, the patient's oral conditions, budget, aesthetic priorities, and medical restrictions all play a role in this decision.

In fact, aside from the price difference between amalgam and composite and their color differences, each material has other important characteristics, and one cannot be considered absolutely better than the other.

Below is a comparison of the main differences between these two restorative materials:

Comparison Criteria	Amalgam	Composite
Color and Appearance	Silver or gray, visible in the mouth	Tooth-colored, blends with natural teeth
Durability (for posterior teeth)	Very high (10–15 years or more) – suitable for high-movement teeth	Relatively lower (5–7 years) – especially in posterior teeth under pressure, prone to wear
Need for a Dry Oral Environment	Highly resistant to moisture during placement	Very sensitive to moisture; requires complete isolation and drying of the restoration area
Type of Bonding to Tooth	Mechanical bond (requires more healthy tissue removal)	Chemical bond (better preserves tooth structure but requires an additional bonding material)
Execution Time	Faster and simpler	Time-consuming, requires multiple steps (etching, bonding, layering, and curing)
Treatment Cost	Cost-effective	More expensive than amalgam (due to more time and complex technique)

According to the Cochrane Review studies, amalgam restorations in posterior teeth have shown lower failure rates over the long term compared to composite restorations. However, composites have the advantage in terms of aesthetics and maintaining the natural tooth structure (Chisini et al., 2020).

 

 

The Price Difference Between Amalgam and Composite

When choosing a dental filling material, one of the important criteria for patients is the cost of treatment. The price difference between amalgam and composite, as the two main materials for dental restorations, is also related to the technique of application, treatment time, and the dentist's skill, aside from the material type itself.

In general, the cost of filling a tooth with composite is usually higher than with amalgam. This price difference has scientific and clinical reasons, which are explained below:

• More Complex Application Process for Composite: The restoration process with composite involves several steps, including etching, the use of bonding materials, layering, and curing with light, all of which require more precision and time.
  
  
• Aesthetic Properties of Composite: Composite is designed to match the natural color of teeth, which is an advantage when restoring front teeth.
  
  

Finally, in government centers and clinics, the cost of filling a tooth with amalgam or composite varies based on the type of center and insurance policies. For an accurate estimate of the prices for amalgam and composite, it is recommended to consult with a specialized dentist before proceeding.

 

Is There a Difference Between White and Black Amalgam?

In dental terminology, the term "white amalgam" is incorrect and non-specialized. In fact, the term "white amalgam," commonly used among patients, refers to "dental composite" or tooth-colored restorative materials.

True amalgam has a color influenced by the metals used in it (silver or dark gray), whereas white composites are entirely metal-free, with a distinct chemical structure and separate usage. Therefore, the difference between white and black amalgam essentially refers to the difference between two materials: composite and amalgam.

 

Conclusion

If you ask ordinary people what amalgam is, they will likely consider it a common dental filling. However, dentists view it as more than just a filling and regard it as an essential part of treatment and maintaining oral health. Understanding the advantages and disadvantages of amalgam is necessary for choosing the best method for dental restoration and filling.

However, this decision also depends on a thorough assessment of the teeth, the patient's expectations, and the dentist's diagnosis. Despite its long history, amalgam still maintains its position and, alongside newer alternative materials, continues to meet many patients' needs.

For personalized advice on selecting the right option for your oral condition, consult with Dr. Abadian’s dental clinic and ensure a comfortable and ideal experience for yourself.