Crowns or “caps” is a procedure done in dentistry that is just as routinely done as fillings. This involves cutting down a tooth anywhere between 1-2 mm around all surfaces then fabricating a protective covering that can be made of all metal (typically gold), all porcelain, or a combination of metal and porcelain. Crowns are usually recommended to be done on teeth that have large fillings that are at risk for fracture, and commonly done on teeth that have had root canals. Sometimes multiple crowns are needed that are either connected together or as single units. These types of procedures can be done to address esthetic concerns, fill in spaces where teeth are missing, or for full mouth rehabilitation. The goal of any crown is not only protect the teeth and restore function, but must adhere to the form and function of your mouth. The crowns must conform to your specific occlusion.
What is occlusion?
In simplest terms, occlusion refers to the relationship of the upper teeth to the lower teeth when they approach each other during chewing or at rest. In most cases we desire to have an ideal occlusion, however more often than not, most people present with a malocclusion, which may be due to either having poorly positioned or missing teeth. The question then becomes whether treatment is necessary. Does the patient present with a physiologic condition, where they are able to function adequately without problems; or is it pathologic, where if allowed to continue, the dentition will continue to breakdown. A physiologic occlusion may not require treatment.
A common misconception is that once the permanent teeth erupt into the mouth, their position remains fixed. Daily function results in minor wear of the teeth both on the biting surfaces as well as between the teeth. Net changes in wear is not perceived due to constant compensatory movement of the teeth. However, sometimes the rate of wear exceeds the rate of compensatory movement, which may then result in an excessively worn dentition and an overall loss of vertical facial height (vertical dimension). More recently, in the dental implant literature, there also appears to be evidence that facial skeletal growth continues well into adulthood.
Philosophies on occlusion
There are several philosophies on how to restore the dentition, however the literature shows that there is no one theory that will work for every patient. There currently is no hard evidence to suggest that any one theory on occlusion works best. That being said, there are certain fixed anatomical parameters that each individual patient presents — muscles, ligaments, skeletal anatomy, and the jaw joint — within which the teeth must fit and function. When a dentist restores your teeth (or for that matter, when the orthodontist straightens your teeth), the anatomy and position of the teeth must fit and function within these fixed factors. As dentists, we strive to accomplish this, however sometimes it becomes challenging when the patient presents with an unstable bite at the start.
As previously stated, when your dentist restores your teeth with simple fillings, caps (crowns), bridges, dentures, or even implants, they make every attempt to ensure that your restoration has the proper form and is able to function within the fixed factors of your mouth in order to maintain its long term health. Often times if the patient presents with an unstable bite, it becomes a challenge to make a restoration that will function properly. Additionally, over time, with the continuous shifting of teeth and skeletal changes, what may initially be a restoration in ideal function and occlusion, may not be the case as we become older. We must also remain cognizant that the wear rates of the restorative materials used are different from natural teeth. Undeniably, if teeth are missing, with a few exceptions, every effort should be made to replace them in order to re-establish and maintain dental health and stability.
Dr. Scott Nakamura maintains a practice at:
Exton Medical Arts Building
80 W Welsh Pool Rd, #207
Exton, PA 19341