How Do Crowns Work?
You may have heard some people refer to a crown as a “cap.” While overly simplified, that is a good basic description of what a crown is. We remove the defective or damaged parts of the tooth and then “cap” it with a replacement that mimics the original tooth structure. However, that description is a gross over-simplification of what actually happens. Let me explain a little more about the process and precision involved in making sure that your crown and underlying tooth structure function as well or possibly better than your original tooth did. Before I start describing the process, let me first assure you that the initial step will be an evaluation of your specific situation to determine the best method of making you comfortable throughout the procedures involved in getting a crown. Some patients take advantage of our sedation dentistry services when getting a crown.
Reduction, Reshaping, and Stabilization
Crowns are used when a tooth has been damaged in a way that makes other forms of repair, such as a filling, impossible or unreliable. Broken teeth, severely cracked teeth, or teeth with underlying inflammation may warrant treatment with a crown. We begin by reducing, reshaping, and otherwise preparing what remains of the tooth to accept the crown (cap). One guide in determining how to reshape or reduce the tooth is the removal of the damaged or diseased portions of the tooth, so that further damage doesn’t continue to occur underneath the crown once it has been placed. Teeth with underlying inflammation get a root canal before they have a crown placed over them. A root canal involves removing the tooth’s pulp (the core of the tooth that contains the nerves and runs down through canals into the roots) and replacing it with a rubbery filler.
A second guide in reduction and reshaping is removing enough of the tooth to allow the crown to be thick enough to be strong and durable as well as cosmetically pleasing. Usually, a crown needs to be about a sixteenth of an inch thick, although our measurements in preparing and designing crowns are far more precise than that. A third guide is to create a certain tapered shape that permits the crown to easily but snugly slip over the top of the remaining tooth. The more of your tooth we can leave, the more stable the finished product will be. Sometimes, we apply special materials to “build-up” what remains of a severely damaged tooth in order to increase the strength and durability of the end result. This overall reduction and health restoration results in the tooth being properly stabilized to receive a crown.
Off to the Lab
Once we have created a stable base to work on, it’s time to begin the “design” of the crown (cap). We place a putty-like substance into your mouth and create an impression of the prepared base, the surrounding tissue and adjacent teeth. This impression is sent off to the lab where a stone-like mold is created that allows the lab to precisely model a crown to fit into your mouth as naturally as possible.
The lab will return the custom-designed crown to us within one or two weeks. Meanwhile, we select and place a temporary crown over the prepared tooth to protect it and allow you to chew with relative ease until the precisely fitted crown is ready.
Perfecting the Fit
While the lab delivers a precisely crafted crown back to us, we will always perform our own quality checks and minor, but exceedingly precise and important adjustments to the crown. To give you a great fit and appearance, we will:
• Verify that the overall shape and coloration of the tooth is as close to natural as possible
• Confirm that there is a precise marginal seal between the prepared tooth base and the inner surface of the crown (This preserves the health of the live tooth base.)
• Verify and adjust as needed the contacts between the crown and adjacent teeth
• Check the way your bite fits with the opposing teeth, adjusting as needed to ensure a good balance
Just as with your natural teeth, you need to exercise care to keep the crown intact. Avoid chewing ice and other hard substances like popcorn kernels that could cause the crown to develop cracks. Even with good care, your crown may not last a lifetime. For this reason, many dental insurance companies will permit replacement of crowns – usually after five to eight years, depending on the policy. Our staff can help you verify your benefits should you ever need a replacement.