Dental Fillings

Dr Thomas Draper DMD
Written by Dr Thomas Draper DMD
Last updated on January 17, 2021

Have you ever put off having a dental procedure done because you were scared? If so, you are not alone. Many people avoid getting dental work done because they have a fear of the unknown.

My goal in writing this article is to help you understand exactly what happens when you go to the dentist for a filling. I’ve broken the article up into three main sections:

  1. A background on why fillings are necessary.
  2. White or Silver? Choosing the right filling material for you.
  3. A step-by-step description of what happens when you get a filling.

Why Fillings are Necessary

First of all, let’s go back to the day you were born. As a newborn baby, there were no harmful bacteria inside of your mouth. As you grew older and became a toddler, bacteria found its way into your mouth. It could have happened when your mom kissed you or when you licked the floor as a baby. In any case, those bacteria have now set up a permanent residence inside of your mouth and you will have to deal with them for the rest of your life.

These bacteria live on your teeth. Every time you eat something that they enjoy eating, such as candy, you provide food for them. Feeding these little creatures doesn’t sound like such a bad thing, but it is!

After they eat, they produce a very strong acid that eats away at your teeth. If you don’t remove this sticky layer of bacteria (commonly known as plaque) by brushing and flossing, the bacteria will keep destroying a tiny amount of your tooth structure every day until you get a hole in your tooth. These holes are known by many names, such as tooth decay, cavities, and dental caries. You can learn more about dental plaque by reading the article What Every Human Needs to Know About Plaque.

Our bodies have the amazing ability to repair injured structures. For example, when we break a bone, our body is able to heal the bone by creating new cells that glue the bone back together. Unfortunately, this isn’t true when it comes to our teeth. Although we do get two sets of teeth in our life, once a hole forms in a tooth, the body cannot repair it. Hundreds of years ago (before fillings existed), cavities eventually caused people so much pain that they would have the tooth removed.

Amazingly, modern dentistry has found a way to let you keep your decayed teeth. All that needs to be done is to have the bacteria professionally removed and then to replace the hole in the tooth with a hard, tooth-like material known as a dental filling.

White or Silver? Choose the Right Filling Material for You

There are a variety of different materials that can be used for filling teeth. In this article, I will only address the two most common filling materials, which are amalgam and composite resin.

Amalgam fillings are more commonly known as silver or mercury fillings. They are made up of silver, tin, copper, zinc, and mercury.

Composite resin fillings are more commonly known as white fillings, tooth-colored fillings, and direct veneers. They are made up of very tiny pieces of silica surrounded by a plastic resin usually composed of bis-GMA.

Amalgam Fillings

Amalgam fillings have been in use for over 180 years in the field of dentistry. When the metals in amalgam come together, they form a soft material that can be used to build your tooth back to its original form. After a few minutes, the amalgam begins to harden as the metals integrate together. Although pure mercury is toxic, the mercury found in amalgam fillings is locked inside when the filling hardens and is therefore not harmful. Many studies have shown that dental amalgam is a safe, time-tested filling material. I will talk more about amalgam fillings in the final section of this article.

Composite Fillings

Composite fillings are newer than amalgam fillings and are constantly improving. The composite resin is about the consistency of modeling clay. In order for the composite to harden, the dentist shines a bright blue light on it. Through a series of chemical reactions, the composite resin hardens into a very strong material that looks very much like a natural tooth.

Which Filling Material Should You Get?

Many people prefer to have white fillings because they are less noticeable. At my dental school we usually recommend amalgam fillings for the back teeth and composite resin fillings for the front teeth. In order to assist you in making an informed decision, here is a short list of eight factors to consider:

1. Amalgam fillings are stronger than composite fillings. We recommend amalgam fillings on the back teeth because that is where the majority of the forces are when you bite down. Since amalgam is made of various metals, it is a very strong material. Composite resin fillings wear down faster than amalgam fillings and need to be replaced more often.

2. Composite fillings are more expensive than amalgam fillings. If you’re on a tight budget, amalgam may be your best choice.

3. Amalgam fillings last longer than composite fillings. I’m sure that with future technological advancements, composite fillings will probably last as long as amalgam fillings someday. There are newer types of composite resin filling materials that can help white fillings last longer than they had previously. Some bioactive filling materials, such as Activa, can exchange calcium and fluoride ions with the tooth structure to help strengthen and protect the tooth-filling interface. To learn more about the duration of each type of filling you can read this post on my blog: Which Type of Filling Lasts Longer, White or Silver?

4. Composite fillings are less noticeable than silver amalgam fillings. If you get an amalgam filling on a back tooth, most likely only you and your dentist will notice it. But if you don’t like seeing silver in your mouth at all, then a composite filling is probably the way to go.

5. Amalgam fillings contain mercury. As I mentioned above, the mercury in the amalgam fillings gets incorporated into the filling. However, amalgam fillings do release extremely small amounts of mercury. The amount of mercury released is less than the amount of mercury you’d get from eating fish, but this does pose a problem for people with a mercury allergy.

At a news conference on July 29, 2009, a dentist, Dr. Susan Runner of the FDA’s Division of Anesthesiology, General Hospital, Infection Control and Dental Devices stated the following about dental amalgam:

“Patients are not at risk for long-term, mercury-related adverse health events.” She went on to add, “We’re not contraindicating dental amalgam in any patient group [other than those who have allergies].”

To summarize, amalgam has been used for over 180 years without any major problems. The only absolute contraindication for an amalgam filling would be a mercury allergy.

UK and Europe: The European Parliament agreed on 14 March 2017 to the final version of its Regulation on Mercury. The Regulation is the EU’s instrument to ratify the Minamata Treaty of 2013. The Minamata Treaty is a global environmental treaty aimed at reducing the release of mercury into the environment. The EU’s Mercury Regulation has the same aim for the territory of the European Union. Both documents prescribe a phase-down of the use of dental amalgam for environmental reasons. The Regulation does introduce a restriction, from 1 July 2018, on the use of amalgam in children under 15 years of age, and in pregnant and breastfeeding women, unless deemed strictly necessary by the practitioner on the grounds of medical needs of the patient.

6. Composite fillings may leak out Bisphenol-A. Bisphenol-A is a chemical that can be toxic in large enough doses. Discussion of this issue is outside the scope of this article, but I will say that based on current evidence, the amount of bisphenol-A released from a filling is unlikely to cause any harm.

7. Amalgam fillings require the dentist to remove healthy tooth structure. Since amalgam fillings don’t bond to the tooth like composite fillings, the dentist has to make the filling wider at the bottom than it is at the top so that the tooth will hold the filling in place. In order to do this, the dentist usually has to cut away healthy tooth structure. With composite fillings, the dentist can simply remove the decay and then place the filling without cutting away healthy tooth structure to retain the filling.

8. Composite fillings shrink when they harden. Most composite fillings get somewhere between 2-5% smaller when they harden. Sometimes this can lead to gaps between the filling and the tooth which allow bacteria to enter and start a new cavity. Other times, when a large composite filling shrinks as it hardens, it can put stress on the tooth which results in increased sensitivity of the affected tooth. The effect of the shrinkage can be minimized if the dentist adds the composite in small, incremental layers.

9. Composite fillings are more technique-sensitive. This means that the dentist has to pay close attention to detail when placing a composite filling.  As you’ll find out below, there are more steps that your dentist must follow precisely when filling your tooth with a white filling.  For example, if your dentist doesn’t properly prepare the tooth with an etching solution for a specific amount of time, or if they do, but some of your saliva gets onto the tooth after it is etched, the filling may not attach to the tooth tightly and could end up leaking and ultimately needing to be replaced after only a year or two.  Most dentists have lots of experience doing white fillings and will do a good job. As long as they are following the steps mentioned below for the composite filling procedure, the filling should last you a long time.

Hopefully, the above section will help you figure out which type of filling will work best for you. Even if you are still uncertain, at least now you know what issues or concerns to further discuss with your dentist.

The Steps Involved in Getting a Dental Filling

Getting a Dental Filling Step 1

The first step when getting a filling is to make sure that you are comfortable throughout the procedure. Dentists usually do this by using an anesthetic. I’ve always found it interesting that dentists give an anesthetic to eliminate pain, yet getting “the shot” is usually a patient’s biggest fear. A local anesthetic temporarily interrupts communication between the tooth and the brain. We call it “sleepy juice” when dealing with kids because it puts the nerve “to sleep”. That way, if the tooth sends a pain signal, the anesthetic prevents the pain signal from reaching the brain – and you feel no pain as a result.

Injections have a reputation for being painful, but the truth is that the amount of pain you experience during an injection will largely depend on the skills of your dentist. Dr. Stanley Malamed, author of Handbook of Local Anesthesia has stated, “Local anesthetic administration should not be painful. Every one of the local anesthetic techniques…may be done atraumatically…Several skills and attitudes are required of the drug administrator, the most important of which is probably empathy. If the administrator truly believes that local anesthetic injections do not have to be painful, then through a conscious or subconscious effort it is possible to make minor changes in technique that will lead to making formerly traumatic procedures less painful for the patient.”

That statement echoes the Needle Phobia page here on Dental Fear Central. It says “You will need to find a dentist who truly believes that injections do not have to be painful.” That page also has many good tips for managing the fear of getting an injection.

The first thing I do when numbing a patient for a filling is to dry the area where the injection will be given. I do this by lightly spraying air inside their mouth. Then, I put numbing gel (topical anesthetic) over the area. We dry the area first so that the numbing gel will soak in faster and deeper.

After the numbing gel has had a minute or two to work, I then give the patient the local anesthetic. If the numbing gel has soaked in fairly well, the patient barely notices the injection.

To recap, we give the patient numbing gel to make the injection a comfortable experience, and we give the injection to make removing the tooth decay a comfortable experience.

Getting a Dental Filling Step 2: Getting Your Mouth Ready

Once your mouth is numb, your dentist may use a couple of different materials to help make the filling procedure easier and more efficient.

The first of these materials is known as a rubber dam. A rubber dam is simply a thin piece of rubber that goes over your mouth and around the teeth where the dentist will be working.

Some patients like having the rubber dam on because it provides a barrier between the dental procedure and the person. When working with children, we call the rubber dam a tooth raincoat because it helps keep the mouth nice and dry while the tooth gets wet.

Another tool your dentist might offer you is a bite block, which is a soft rubber triangle that can be inserted between your upper and lower teeth to prop your jaw open. During longer dental procedures, it may be difficult to continuously use your jaw muscles to hold open your mouth. A bite block props your mouth open, which keeps you from having to use your jaw muscles to keep your mouth open, thus relaxing them. A bite block can also keep you from closing your mouth during the procedure, which allows your dentist to work efficiently and get your filling finished as quickly as possible. If you prefer not to use a bite block, let your dentist know.

Depending on where your filling is and on which material is used, your dentist may not elect to use a rubber dam or a bite block. For tooth-coloured fillings, it is especially important to keep the area dry so that the composite resin can properly bond to the tooth. This can be achieved in several ways: using a rubber dam, cheek retractors, placing cotton rolls, and using other disposable moisture absorbers. Be sure to ask your dentist questions so you are aware of what will go in your mouth. Some ways of controlling moisture are more gag-inducing than others!

If you are getting a tooth-colored filling, this is usually the time when your dentist will hold many different colors of teeth next to yours to figure out which shade of filling material will be used.

Once you’re numb and your mouth is ready, the dentist will begin to remove the portion of your tooth that was damaged due to tooth decay.

Getting a Dental Filling Step 3: Removing the Tooth Decay

Now that you’re ready for the procedure, the dentist will begin to remove the tooth decay. There are a number of tools that are used to clean out the decayed portion of the tooth.

First, your dentist will probably use what is called a high-speed handpiece. You may be more familiar with its more common name, the dental drill. The high-speed handpiece sprays out a jet of water while the dentist works. It also emits a high-pitched whistling sound, which is where it gets the name of “Mr. Whistle” when we work with kids. Since you are already numb when the dentist uses the high-speed handpiece, you shouldn’t feel anything. It moves so fast that it glides through the tooth decay and whisks away the damaged tooth structure.

While the dentist is using the high-speed handpiece, the dental assistant will be holding the high-volume suction in your mouth. The high-volume suction quickly removes the water from the high-speed handpiece and any debris from your tooth. You can think of it as a little vacuum cleaner, helping the dentist to remove the tooth decay from your mouth. Another suction you may encounter is the low-volume suction or saliva ejector. If you get some extra water in your mouth and don’t want to swallow it, the dentist or assistant can allow you to close your mouth around this smaller suction to remove any extra water that may be in your mouth.

After the dentist has mostly finished removing the tooth decay, he or she will switch to the slow-speed handpiece to refine the preparation and help remove any remaining portions of decayed tooth. This handpiece is slower than the high-speed handpiece and does not emit a whistling sound. Because it is slower, you may feel a vibrating sensation in your tooth. This vibration is why we call the slow-speed handpiece “Mr. Bumpy” when working with kids.

Finally, the dentist may choose to finish removing decay with some hand instruments. These are simply small, metal tools that the dentist can use to refine the area where the filling will be placed or to remove any remaining tooth decay.

During the procedure of removing the tooth decay, the dentist will most likely use an air/water unit. This is a small attachment that can spray either air or water into your mouth. It is useful to rinse away any debris that is obstructing the dentist’s view of your tooth.

Now that the damaged portion of your tooth is gone, the dentist will replace the missing tooth structure with a filling.

Getting a Dental Filling Step 4: Replacing the Decayed Tooth with a Filling

Next, the dentist will fill the tooth and make it look like a real tooth again so that you can use it to chew food and speak. Since the procedures for restoring a tooth with amalgam and composite differ somewhat, I have separated this portion into two separate sections. First I’ll talk about what happens when you get an amalgam filling; then I’ll talk about what happens when you get a composite filling.

Getting an Amalgam Filling

If your cavity is on the center of the biting surface of your tooth, then you can skip this paragraph! If your cavity is between two teeth, the dentist will place a metal band (called a matrix band) tightly around the tooth to help build the wall of the tooth back up. Your dentist will also place a wedge between the two teeth so that when the filling is completed the neighboring tooth and the new filling will touch together and prevent food from getting caught between the two teeth when you chew. Newer alternatives to the matrix band and wedge are now being used that involve placing a small separator between the teeth with a spring-loaded ring that pushes the teeth apart to ensure that you don’t get food caught between the teeth when your filling is completed. Your dentist can explain the system they use to help you understand what is going on.

Many times dentists place what are called bases or liners onto the exposed internal part of the tooth to help prevent the tooth from hurting after the filling is completed.

Liners are placed to seal up the passageways that go to the nerve of the pulp. Once those are sealed, you shouldn’t have any sensitivity after the procedure. The liner that we use at my dental school is called copalite cavity varnish. We dip a tiny brush into the varnish and paint it into the tooth. Then we spray some air on it to dry it. It does smell similar to the varnish that is often used on wood.

Bases are used when the tooth decay is very close to the nerve of the tooth. The procedure is similar to applying a liner, but the base is a little bit thicker. Some bases can be air-dried and others need a dental curing light to be shined on them to harden.

After the base or liner is placed, the dental assistant will mix up the amalgam. We use a machine that rotates a capsule of unmixed amalgam very fast. It does make a loud vibration noise. I’ve found that many patients turn around to see what’s going on when we mix the amalgam. It needs to go fast because the mercury is sealed in a plastic pouch and the machine has to break the mercury out of the pouch and mix it up with the other metals.

Once the amalgam is mixed, the dentist uses an instrument called an amalgam carrier to place the amalgam inside of your tooth. Next, your dentist will push the amalgam down into the tooth to make sure it is tightly compacted and that there aren’t any empty spaces. This can make a funny noise that sounds similar to stepping on top of freshly-fallen snow.

After the amalgam is compacted, the dentist will carve the amalgam to make it look like a tooth. When that is finished, your dentist will have you bite down on a thin sheet of carbon paper. This helps us to see if the filling is too high. The carbon paper rubs off onto the filling and shows the dentist where he or she needs to lower the filling.

Once that’s done, I usually ask my patient if the filling feels alright. The only problem is they’re still numb, so it’s hard to tell.

Getting a Composite Resin Filling

There are several similarities between the process of receiving a composite resin filling and an amalgam filling. Just like when you get an amalgam filling that is on the edge of one tooth that touches another, the dentist will need to place a band around the tooth and a wedge between the two teeth. The main difference in this part is that the band is a clear band instead of metal. This allows the curing light (mentioned below) to shine through the band since the light can’t pass through metal.

When placing a composite resin filling, the dentist will first put some acid, usually in the form of a blue gel, on the prepared tooth. This acid creates very tiny holes in the tooth which allow the composite resin to bond to the tooth. This also ensures that the filling doesn’t fall out.

The dentist will then rinse the acid away. After that, your dentist will dry the tooth and place a tiny amount of priming and bonding agent to the tooth with a tiny brush. The priming and bonding agent helps form a strong bond between the tooth and the eventual filling.

Next, the dentist will use the previously selected shade of composite resin filling material and put it inside of your tooth. Depending on the technique your dentist prefers, he or she will either squirt it directly into your tooth or put it on a small metal instrument used to place it in your tooth. After this, the dentist will make sure that the composite is evenly spread out in your tooth and that there are no air bubbles.

A curing light for hardening composite fillings

Then the dentist will shine a bright blue light (similar to the one in the photo) on the composite which will harden it and make it very strong. This process is known as curing the composite. Since the light doesn’t penetrate the composite very deeply, your dentist may have to apply and cure multiple layers of composite if you had a deep cavity. You can learn more about curing lights here.

After your dentist finishes filling the tooth he or she will have you bite on carbon paper to make sure the filling isn’t too high. If it is, then your dentist will lower the filling with a high-speed handpiece.

Finally, if there are any rough spots on the filling, the dentist can use some mild abrasives to smooth the filling and to make it feel smooth to your tongue.

What will your filling look like?

If you’d like to see what an amalgam or composite filling looks like, take a look at the following article: What do Silver and White Fillings Look Like?

How Do You Know If Your Filling is Too High?

After the filling is finished, you may feel some sensitivity in your tooth for a few days. If the tooth starts feeling sensitive only when you bite down, you should go back and see your dentist as this could be a sign that your filling is too high. Your dentist will be able to check your bite again and then smooth down the filling using some specialized attachments to the high-speed handpiece. Since your dentist should only need to smooth down the filling and not your tooth, you won’t need to be numb for this.

Congratulations — You’re Done!

That’s all there is to getting a filling. Hopefully the procedure goes well and you’ll be as happy as the patient pictured below.

Dentist with a happy patient

In conclusion, I want to mention something that many dentists fail to discuss with their patients: There is a reason that you needed a filling!

You need to determine why you got a cavity in the first place, and decide how to fix it. There’s probably something you can do to prevent future cavities. Making changes to your diet and oral hygiene habits now can prevent the need for future fillings. Many people do not realize that it is the frequency of sugar intake, rather than the quantity, which can cause cavities. You can read more about this on Dental Fear Central’s How to prevent tooth decay (or stop it from getting worse) page.

Hopefully this article has helped to ease some of the fears you may have about getting a filling. Many people find that the actual experience is much better than they had anticipated.

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