For centuries, various metals have played a foundational role in dentistry, serving as reliable materials for a wide array of procedures. The practice of using metals for dental purposes dates back at least 300 years B.C., with gold being employed in ancient Rome for fixing artificial teeth. Over time, the application of metallurgical knowledge has expanded the range and sophistication of metal-based dental solutions in restorative and orthodontic applications.
Common Metals in Dental Restorations and Appliances
Dental amalgam, often called “silver fillings,” is a mixture of liquid mercury and a powdered alloy of silver, tin, and copper, with mercury making up about 50% of its weight. It is primarily used for filling cavities caused by tooth decay, particularly in posterior teeth. The mercury helps the alloy particles bind, forming a pliable material that hardens into a durable filling.
Gold alloys are combinations of pure gold with other metals like silver, platinum, and copper. They are commonly employed for indirect restorations such as crowns, inlays, and onlays, which are fabricated outside the mouth and then cemented onto the tooth.
Stainless steel is widely used in pediatric dentistry for prefabricated crowns on primary (baby) teeth. These tooth-shaped caps are placed over extensively decayed or damaged baby teeth to protect them until they naturally fall out. Stainless steel is also a common material for orthodontic appliances like braces.
Titanium and its alloys are a primary choice for dental implants, which are surgically placed into the jawbone to support prosthetic teeth. Commercially pure titanium (cpTi) is often used, but alloys offer enhanced strength. Titanium is also utilized for frameworks in fixed dental prostheses.
Nickel-titanium (NiTi) alloys are frequently used for orthodontic archwires. These wires are composed of roughly equal parts nickel and titanium. NiTi alloys exhibit properties suitable for orthodontic tooth movement.
Why Metal is a Dental Option
Metals are chosen for dental procedures due to their exceptional durability and strength. Metal crowns, for instance, are engineered to withstand significant chewing forces and bruxism, often lasting 20 years or longer with proper care. This resistance to physical stress means fewer chips, cracks, or breakages compared to some alternative materials.
The longevity of metal restorations contributes to their cost-effectiveness over time. The extended lifespan and reduced need for repairs or replacements can result in lower overall costs for patients. This makes metal a practical choice for long-term solutions, particularly in high-stress areas of the mouth like molars.
Titanium’s unique property of osseointegration, where bone cells directly attach and grow onto the implant surface, provides a strong and stable foundation for dental implants. This direct connection ensures long-term stability and success.
Nickel-titanium alloys offer specific functional benefits in orthodontics due to their shape memory and superelasticity. These properties allow NiTi wires to exert light, continuous forces over a broad range of deflection. The wire can be deformed to fit misaligned teeth and then gradually return to its original arch shape as it warms in the mouth.
Concerns About Metal in Your Mouth
One common concern relates to the mercury content in dental amalgam fillings. Small amounts of mercury vapor can be released during placement, removal, or even during chewing. While the U.S. Food and Drug Administration (FDA) considers dental amalgam fillings safe for most, certain populations, such as pregnant women, nursing mothers, and young children, may be at greater risk for adverse health effects from mercury exposure.
Allergic reactions to specific metal components are another consideration. Nickel, a common allergen, is present in many dental alloys. While allergic reactions to dental materials are generally rare, individuals with a known sensitivity to nickel may experience symptoms such as itching, swelling, redness, or a persistent metallic taste in the mouth.
The phenomenon of galvanic currents can occur when two or more different metals are present in the mouth, acting like a battery within the saliva. This can happen between dissimilar metals in fillings, crowns, or orthodontic appliances. An electric current can flow, which some individuals may perceive as a sharp pain or a metallic taste. This current can also accelerate the corrosion of metal restorations.
Non-Metallic Choices for Dental Care
Composite resins, often called “tooth-colored fillings” or “white fillings,” are polymer-based materials reinforced with fine glass and plastic particles. These materials are used to fill cavities and restore tooth decay, offering a natural appearance that blends with existing tooth color. Composite resins are suitable for small to medium restorations and can be applied directly to the tooth, often in a single visit.
Ceramic materials, such as porcelain, are widely used for crowns and veneers due to their ability to mimic the light-reflecting properties and translucency of natural teeth. Traditional porcelain and stronger lithium disilicate are common types. These materials are highly customizable in color and can create a seamless appearance.
Zirconia, composed of zirconium dioxide, is a newer ceramic material gaining popularity for crowns and bridges. It offers exceptional strength and durability. Zirconia is highly resistant to wear, chipping, and cracking, making it a robust choice for posterior teeth and for patients who experience heavy biting forces. This material is also biocompatible and can be a suitable option for individuals with metal allergies.