A dental crown is a type of cap placed on top of a damaged tooth. Dentists recommend dental crowns when:
- Your tooth has a very largefillingthat is bigger than your natural tooth structure
- Your tooth hadroot canal therapy
- You have a combination of root canal therapy and a large filling
- You need a crown for cosmetic reasons
This article will discuss dental crowns, how a dentist decides you need one, and alternatives to getting a dental crown.
Numbing the Tooth
The first step of the dental crown procedure involves using alocal anestheticto numb the tooth and surrounding tissues. If you've had a root canal, your dentist will still likely choose to use anesthetic. This is because the instruments come very close to the gingival tissue.
Preliminary Impressions and Shade
The dental laboratory that makes your dental crown requires accurate models of the curved structures where your teeth grow. These structures are called the maxillary and mandibular arches. The dental lab does this to create a perfect crown for your tooth.
If you have chosen a full ceramic or porcelain fused to metal crown (PFM), your dentist will also require the exact shade of your tooth before they begin the preparation of the tooth.
The dental assistant will take impressions of both your upper and lower dental arches. For these, a material such as polyvinyl siloxane (PVS) is used to make a mold. These impressions will be poured into stone to create a stone model of your teeth. The models will be sent to the dental laboratory for use when making your crown.
The dentist makes a small impression of the teeth. It's made in the same section of the tooth that requires the crown. It also includes an impression of the opposing arch. The impression is used to make a temporary crown for you to wear until your permanent crown arrives back from the dental laboratory.
After the impressions, the dentist will use a shade guide to record the exact color of your tooth. If your crown involves a front tooth, your dentist may send you to the dental laboratory for the lab technician to take a custom shade of the surrounding teeth. If you have opted for a gold crown, there is no need to determine the shade.
Digital dentistry has changed the process of making crowns. Crown impressions can now be completely digital. A scan of the prepared tooth and arches can be used to create the permanent crown. Temporary crowns may still need to be made using traditional impressions.
There is also same-day milling of crowns where the tooth is prepared and a digital impression is made. A couple of hours later you can have your crown fabricated and cemented the same day. This is more expensive as well because of the ease and convenience of this method. No temporary crowns are needed with this procedure.
Preparing the Tooth
A dental crown mimics the entire visible portion of the tooth. It has a hollow space inside like a cap. In order for the finished crown to fit correctly, the remaining core underneath the crown needs to be reduced so the crown can fit on top. A crown is designed to securely fit the tooth. It keeps bacteria away from the vulnerable tooth structure.
Placing a Rubber Dam
Once the tooth and tissues become numb, the dentist may decide to place a rubber dam over the teeth involved. The rubber dam is used to trap old filling material, tooth structure, and water so debris can't fall into your mouth.
Filing the Tooth and Removing Decay
Preparing the tooth for a dental crown involves removing very precise amounts of the tooth and filling material from the tooth that requires the crown.
During this step, the discovery of tooth decay underneath an old filling may occur. If that is the case, all of the decay is removed and a composite core is placed on the tooth. If your tooth has gone through a recent root canal, a composite core may be placed as well during this step.
Once the core is complete, your dentist will continue to shape the tooth. This creates a fine margin around the entire core of the tooth, like a shelf. They will continue reducing the biting surface of the core until sufficient tooth and filling have been removed.
This step is extremely important and generally takes the most time to complete.
Taking the Final Impression
Accurate impressions of your prepared tooth are an important part of the dental crown procedure. Even the tiniest flaw in the impression can result in a crown that doesn't fit correctly.
Once the tooth has been prepared, your dentist may decide to use a gingival retraction cord to gently push your gum tissue away from the margins of the prepared tooth.
A gingival retraction cord is a thin piece of cord. It's similar to a piece of yarn. The dentist gently inserts it around the tooth and into the gingival sulcus. Some dentists have adopted other techniques for isolating the tissue, such as gingival curettage.
Beginning the Final Impression Process
When the tooth is ready for the impression, your dentist will then take an impression of your teeth. Your dentist will begin the impression by applying a putty-like material, made of polyvinyl siloxane, around the prepared tooth.
The dental assistant will begin filling the impression tray with corresponding impression material. Your dentist will insert the impression tray over your prepared tooth. Then the dentist will ask you to bite down.
It is very important for you to continue biting into the impression until the material is fully set. This impression takes between three and five minutes to fully set. You'll have to be patient during this step of the dental crown procedure.
Once the impression material has set, your dentist will remove the tray from your mouth and inspect the impression for any air bubbles or another void in the impression.
It may be necessary to repeat the impression several times in order to obtain a very accurate impression.
Fabricating a Temporary Crown
Placing a temporary crown over the prepared tooth may seem like a cosmetic necessity. But in reality, the temporary crown is very important for a number of reasons.
Some states and provinces allow dental assistants to make a temporary crown for your prepared tooth. In some cases, the dentist will fabricate the temporary crown.
Importance of Temporary Crowns
Temporary crowns are very important. Because your dentist has removed a large amount of tooth structure from the prepared tooth, the temporary crown acts as a barrier. This keeps the prepared tooth in its place. Without a temporary crown, the prepared tooth can begin to shift.
Any movement from the prepared tooth will prevent the permanent crown from fitting properly. In some cases, the prepared tooth can move so much that the permanent crown simply won't fit over the prepared tooth. If this happens, the final impression will be taken again. Then the crown will be sent back to the laboratory to be remade.
Temporary Crowns Protect Teeth
Temporary crowns also keep a vital tooth protected. If you had a root canal, there will be no feeling in the tooth. Vital teeth are a different case. Most of the enamel is removed from the tooth during the preparation stage, leaving exposed dentin.
Without a temporary crown, your tooth would be extremely hypersensitive to temperature and pressure. A temporary cement that contains eugenol is generally used because of its calming effects on the nerve.
Preparation for the Temporary Crown
Using the small impression taken prior to preparing the tooth for the crown, the dentist or assistant will fill the impression tray with an acrylic resin material that fits the color of your natural teeth. Then the dentist places it over the prepared tooth.
Once the material has set, generally after one to two minutes, the impression is removed from your mouth. The dentist shapes the temporary crown so that it fits your tooth and removes any rough edges.
Once it's ready, a temporary cement is used to secure the temporary crown onto your prepared tooth. The dentist will check to make sure your teeth bite together correctly. They will also make sure there are no rough or sharp edges around the temporary crown.
It is extremely important that you follow the postoperative instructions given to you for wearing a temporary crown. If the temporary crown comes off your tooth, call your dentist immediately. Then book an appointment to have it re-cemented.
Preparing to Cement the Permanent Crown
It generally takes the dental laboratory roughly seven to 10 business days to make your permanent crown. Your dentist will ensure you have your cementation appointment scheduled before you leave the office after your tooth preparation appointment.
When you return to the dental office to have your permanent crown cemented, the dentist will begin the appointment by numbing the prepared tooth and surrounding tissues with a local anesthetic.
Even though the tooth is already prepared, the dentist needs to thoroughly clean the tooth before cementing the permanent crown. If you had a root canal performed on the prepared tooth, you probably won't need any local anesthetic.
Permanent Crown Process
Once the prepared tooth is completely numb, your dentist will remove the temporary crown from the tooth. All of the temporary cement is removed from the tooth, and the tooth is completely dried. Your dentist will then try the permanent crown on the tooth.
Using a piece of dental floss, your dentist will also check the contacts in between the crown and nearby teeth to ensure there is an ideal contact between the teeth. Contacts that are too tight or no contact at all pose a problem for you in the long run.
A contact that is too tight will cause problems for you when you floss your teeth. No contact in between the teeth will allow food to become lodged in between the teeth. This causes the potential for tooth decay.
If the contact is too tight, your dentist will reduce a small amount from the nearby tooth, not the crown. In cases where there is no contact, it may be necessary for the crown to be sent back to the laboratory to be remade.
Final Cementation Process
When your dentist is satisfied with the fit of the crown, the final cementation process begins. This process involves keeping your tooth completely isolated from any saliva or water in your mouth.
Cotton rolls may be placed on both sides of the tooth to keep the area dry. When the tooth is isolated and dry, a desensitizing agent may be applied to the tooth. The desensitizing agent will help with any postoperative tooth sensitivity.
Your dentist will then place a bonding material onto the prepared tooth. Some bonding agents require a curing light to set the material. Once the bonding agent has been set:
- The dental assistant will fill your permanent crown with cement and carefully pass the crown over to your dentist
- Your dentist will place the crown on your tooth and remove some of the excess cement that squeezes out from underneath the crown
- A curing light may be used again to set the cement completely, depending on the cement chosen
The dentist uses dental floss to remove the excess cement from in between the teeth. And a dental scaler is used to remove excess cement from around the tooth and below the gumline.
Checking the Bite
The dental laboratory made your dental crown according to your dentist's exact instructions. But there will be small adjustments that need to be made. This will ensure your new crown functions correctly.
Your dentist will wait approximately 10 minutes for the permanent cement to set. When ready, your dentist will then check how your teeth bite together.
Any high spots on the crown will be reduced on the opposing tooth. It is very important to have the bite correct. This is because a high bite can lead to tooth sensitivity and tooth pain.
Your new crown was made to withstand the normal forces from:
However, it is very important to understand that crowns are not indestructible.
Once the bite is accurate and your tooth has been cleaned from any excess cement, your dentist will give you very specific postoperative instructions for your new crown. It is important for you to follow these instructions to the letter.
Most specifically, what you eat with your new crown is the biggest change you will make due to your new crown. For example, candy and nuts are very destructive to crowns. You should try to avoid them.
If after a few days you notice anything unusual with your new dental crown, call your dentist immediately to have the crown examined.
It is also extremely important that you continue following a strict oral hygiene regimen that includes brushing, flossing, and professional cleanings for your crowns.
A dental crown is a kind of cap a dentist puts on your damaged tooth. It may be used after a root canal or if your filling is larger than your natural tooth structure. You may also need a crown if you have a combination of root canal therapy and a large filling. At times, your dentist may recommend a crown for cosmetic reasons.
If your dentist performs a dental crown procedure, it's important to follow their postoperative instructions. Practicing good oral hygiene habits and following your dentist's instructions will help you protect your new crown as well as your natural teeth for many years to come.