A concern we see often in dentistry, particularly among individuals with large previous fillings or cavities, is that when we are trying to replace most of the top of a tooth with either metal or a white fillings neither comes close to bringing the tooth back to its original strength. Do me a favor and consider an analogy for a second… picture an empty can of coke and what it feels like to squeeze the can. Despite the thinness of the aluminum walls the can stays strong when pushed in from any direction. However, if the top of the can is cut off and the can is squeezed, now when you push on the walls the can will distort and bend without hardly any resistance!
A tooth is similar, it has a thin outer layer of a hard tooth structure called enamel, but that outer layer relies on the thick and resilient tooth layer called dentin lying just below the enamel. When a large amount of the center of the tooth has been drilled away and the tooth is filled with either a white or metal filling, stress from biting will not be dissipated or supported as it would be in a healthy tooth. In all but the gentlest of chewers when teeth are hollowed out from large fillings the tooth will develop micro-cracking and stress over time and that stress will result in the edges of the tooth fracturing or cavities developing through the micro-cracks.
Fortunately there is an alternative to teeth eventually needing crowns, eventually fracturing or eventually developing cavities. When very large fillings are present in someone that has shown stress generally in their bite, large fillings can be replaced as soon as possible with porcelain! Teeth restored in our office with porcelain look like the original tooth, and most importantly chewing tests have shown that even when extensive tooth structure is missing the tooth can be brought back to its original strength! This is a treatment that is not done nearly enough in my opinion, it’s much more conservative than a crown, and the hope is it would prevent the tooth from ever needing a crown! To be successful this treatment needs to be done before a tooth is heavily strained and cracked. When we see someone that has gone too many years with a very large filling in place we will often restore the tooth with a very conservative crown so we can replace the micro-crack-filled walls surrounding the large filling. If you’d like to see pictures of what those micro-cracks look like ask Dr. Davis, he has tons! Inlays and onlays are a conservative alternative to keeping teeth even with large cavities and large existing fillings healthy for a lifetime!