Thanks to technological advances, dentists and patients today have several choices when it comes to selecting materials to fill cavities. Among the choices are natural tooth-colored materials such as resin-based composite fillings and more traditional dental fillings such as those made of metal amalgam. Keep in mind that there are still other materials for restoring teeth including porcelain, gold inlays, zirconia, CEREC, and others for larger fillings, more damaged teeth, or heavy grinders. These may be better options still, but let’s keep it (somewhat) simple for today.
What is dental amalgam?
Otherwise known as “silver fillings,” dental amalgam is made up of mercury, silver, tin, copper, and zinc, of which mercury makes up about 50%. Though the material has mercury, studies have proven this material to be safe and may sometimes be the only viable option.
What is resin composite?
Otherwise known as “white fillings,” resin composite fillings are made of ceramic and plastic compounds. When they were first developed, they weren’t strong enough to be used in back teeth. With technological advancements supported by numerous studies, these materials are strong enough to be used in back teeth and can provide many advantages.
Which material is best for me?
It really depends. Deciding which type of filling to use is best made by considering the size and location of the cavity, your oral hygiene, your cosmetic concerns, cost, and other factors. Ask your dentist to discuss all of the choices available for dental fillings and help you decide which is right for you.
What are the advantages and disadvantages of each?
- The main 3 are: strength, durability, and easy application
- Though they don’t technically require a dry site, they can be the better option where it is not possible to place a filling without contamination from saliva (though they can be affected by saliva as explained below)
- They have a long history of strength and durability which means fillings “last” in your mouth longer (though they may just be better at hiding decay and the material strength may not be very kind to your tooth as explained below)
- Because they’re easier for your dentist to place, they don’t require any extra training, extra effort, or extra material costs meaning your appointment may be about 10-20 minutes quicker and cost a bit less. (But it’s important to consider the long-term costs and disadvantages, if any, before deciding if that extra $50 is actually saving you money or not).
- Corrosion: Amalgams seal through corrosion which often means a darkened or discolored tooth. In addition, corrosion means increased porosity, loss of strength, release of metallic products into the mouth, and open margins where the tooth and filling meet leading to bacteria leaking underneath and creating cavities we can’t see. Perhaps most detrimentally, this corrosion may produce additional lateral stress on the walls of the tooth preparation because by-products of corrosion occupy a larger volume which can lead to the cracks and fractures dentists often see in teeth with old amalgam fillings.
- More aggressive: amalgam restorations need to be at least 1.5-2 mm thick uniformly meaning if decay is small or only deep in one area of the tooth, good tooth structure will need to be removed simply to make sure the metal is thick enough to withstand forces and be retained in the tooth.
- Cracks and fractures that can lead to more extensive dental treatments: amalgam restorations expand and contract considerably more than composite restorations. This cyclic dimensional change may consequently contribute to the fatigue of the tooth structure and to cusp fractures. In addition, because of creep and flow, amalgam permanently deforms under pressure. With larger amalgams, these changes can create additional lateral stress on the tooth leading to cracks and fractures. The condensation of amalgam also bends the remaining tooth cusps outwards, and the setting reaction of filling-type amalgams produces a slight expansion, which may also add additional stress and cracks. If a tooth cracks or fractures a crown is often the next step and, if this crack extends to the nerve, a root canal or extraction may be necessary.
- Harder to see recurrent decay around or underneath fillings: due to the gray staining of the tooth around older amalgam restorations, visual evaluation of decay during your dental exam is more difficult. In addition, the extremely high radiopacity of amalgam on an x-ray makes the diagnosis of secondary caries less accurate than with less-radiopaque composites which often means we can’t see cavities until your nerve tells us they’re there.
- Delayed hardening: it takes 8 hours before an amalgam filling reaches 70% of its 1 week strength so the actual hardness of the filling may be decreased if you accidentally chew on your new filling within the first week.
- Temperature effects: an amalgam filling experiences a decrease in strength by 50% when drinking something hot. Amalgam is also more likely to yield long-term sensitivity with hot or cold air, drinks, or foods than other non-metal fillings.
- Can still be contaminated: certain amalgam alloys (especially high-copper amalgams) still need to be placed in a dry environment and can experience delayed expansion if wet. This can then lead to significant expansion causing leakage and nerve pressure pain among other issues if saliva-contamination occurs during placement.
- Marginal breakdown: if not bonded, the restoration pulls away from the tooth leading to leaking, graying of tooth, recurrent decay, and other issues.
- Galvanic shock: can occur when two amalgam or any metal fillings come in contact or are placed too close together. Essentially, this sets up a “battery” in the mouth and the electrical current stimulates nerve endings in the tooth leading to an uncomfortable feeling.
In summary, the biggest disadvantage from a tooth-preservation and economical standpoint is that these fillings require more tooth structure to be removed and their properties often lead to cracks and missing tooth cusps. Because of this, you may be looking at a crown, root canal, or even an extraction in the long-run in a tooth that would have otherwise been treated kinder with a different material. In addition, because of the decay that is often missed underneath these fillings, root canals and crowns are more likely as well as the decay only become obvious when it is larger. Considering these extra costs and appointments, does it really make sense to choose an amalgam filling because it’s 10’s of minutes or 10’s of dollars less?
- The color matches your natural tooth, so they are esthetic and natural-looking
- They are bonded to your tooth which means that they can restore at least some of your tooth’s original fracture resistance once placed in the tooth (which non-bonded fillings can’t do)
- They are more conservative than amalgam meaning you can preserve more of your natural tooth leading to less issues in the long-run with fractures, sensitivity, and total dental work
- They are completely cured before you leave the office so there’s no risk of fracture during a typical amalgam’s setting time
- Being plastic, they are worse conductors than metal fillings meaning less sensitivity to hot or cold over time
- Act more like your natural tooth leading to less cracks and fractures (which often mean more aggressive dental work like a crown or root canal)
- Stain with time: in front teeth, this will be more obvious, especially if you eat or drink things that stain teeth more quickly. Often, these extrinsic stains are shallow and can be polished away at your dental appointments. The best esthetic material that doesn’t stain will be a porcelain or other indirect and highly polished material.
- Require a dry site: the material does not work well in areas of the mouth where it is difficult to keep the tooth dry such as in patients with physiological limitations (can’t open wide) or some children. However, advances in isolation systems and rubber dams have led to this being a very infrequent problem.
- Require the right technique and take more time: because they are bonded, they require a few more steps, but often this added time is negligible considering they are cured immediately by the light meaning you don’t have to wait at the end of an appointment to check the bite like you do with amalgam.
- Post-operative sensitivity: you may experience some brief tooth sensitivity following the procedure. Though this is possible with all materials as drilling on the tooth is often the primary issue, this can sometimes be avoided by using lots of water during drilling, a liner for sensitivity, and proper placement techniques.
- Not as resistant to decay as silver fillings: due to the lack of acid-buffering abilities in the mouth. Because, unlike amalgam, they lack the ability to increase the local pH, this can lead to the outgrowth of more acidogenic/aciduric bacteria in patients who are not diligent about their oral hygiene routine. In short, this means that patients with poor oral hygiene might be better served with an amalgam filling in certain situations if they have no desire to improve their oral hygiene (keeping in mind that the disadvantages of amalgams must still be accounted for).
- Wear sooner than metal fillings: especially if you have heavy wear from grinding and chewing because they are not as strong. However, if you are clenching or grinding, amalgam may not be a good option also as these forces on the amalgam can cause fractures in your tooth (as explained above). A zirconia or porcelain filling or crown might be best for someone who is that hard on his or her teeth.
- They’re more expensive than silver fillings: because the material costs more and it takes more time. A Mercedes costs more than a Hyundai for a reason.
- Your dental plan may not cover them: this is never a good reason to choose one option over another. Your dental plan covers only what your employer asks it to cover, not what is in your best interest. Do your research and decide with your dentist what is best for you and, if money is a factor, realize that the cost difference is not massive and talk about a payment plan if possible.
It’s interesting to note that many the “disadvantages” of composites often have nothing to do with the material itself but with the practitioner or placement. “Time consuming, technique-sensitive, difficult to polish, and expensive” are often what is read when looking for disadvantages. If you have a doctor skilled in composite placement, these disadvantages become negligible.
And, like anything in life, you get what you pay for. The difference in cost between amalgam and composite is typically $50-100 which, considering the advantages and decreased likelihood of future more expensive procedures, should be well worth it. Because they take a little longer and are more technique-sensitive sometimes dentists, used to doing things how they’ve always done them, don’t want to learn the new techniques, take the extra time, or spend money on materials needed to avoid contamination while placing fillings. This should not be the reason you choose a different material that may not be best for you.
So…should I replace my amalgam fillings?
The short answer: no. Many amalgam fillings are better off left alone if there are no signs of issues or if they don’t bother you esthetically. Whenever you replace a filling, you typically have to remove some additional tooth structure, especially if there is decay discovered underneath (though you would want that cleaned out anyway). The more tooth structure you remove, the more likely sensitivity is to occur. However, this sensitivity is often short-term and if signs indicate the amalgam is harming the tooth, this may be the right way to go. Only replace amalgam fillings that your dentist suggests replacing due to reasons listed above or below:
- Signs of decay or soreness in the tooth or beneath the filling
- A “void” or margin breakdown between the filling and the tooth
- The filling can no longer be supported due to a crack in the body of the tooth
- Recurrent decay under or around the filling
- You have concerns about the mercury in the filling (though, as mentioned before, are statistically negligible)
- You have concerns over esthetics and simply desire a more natural looking filling
Always ask your dentist for their recommendation. Every case is different, so you’ll want a personalized assessment. When it comes to removing old fillings and replacing them with new ones, it is best to be aware of all the options available to you, many of which aren’t reviewed in detail in today’s blog post.
Okay, you’ve said a lot. What’s the final verdict?
In summary, when access is limited in the mouth, a procedure needs to be completed as quickly as possible, or dryness is not possible, an amalgam filling may be your best choice. However, new advancements have taken many of these issues completely off of the table.
Weighing the advantages and disadvantages, composites and other stronger and cemented materials (such as Emax, Ceramic, Porcelain, and Zirconia) are often better in the long-run than amalgam. Amalgam’s biggest benefit is it’s strength in a large filling; but with other strong materials are available, these kinder and more esthetic options might be just what you need. With time, things are always improving and advancing. As of now, they are working on how to replace decayed tooth with natural-growing tooth material, so stay tuned for the changes that are inevitable in any field of study that is always improving!
Hope that wasn’t too confusing! There’s a lot to talk about and we’ve just barely skimmed the surface. As always, ask your dentist to explain what they think is best for you and come to a decision together. Dr. Stephan would be happy to discuss your specific case with you.