When a patient has a cavity (caries), the dentist must consider whether a composite restoration (filling) or a crown is the best option to repair the tooth. If the cavity is large, biting forces exerted on the tooth must be considered.
Filling or Crown?
When a person chews, tremendous forces are exerted on the teeth. Up to 573 pounds can be exerted on the molar teeth! This is why it is so important for dental restorations to be strong enough to withstand those forces. Once a filling becomes too wide or too deep, the integrity of the tooth is compromised.
Large fillings destabilize teeth and, over time, biting forces from the opposing teeth can cause cracks, breakage, inflamed roots and pain.
Biting forces can cause the tooth to crack at the base. Decay can occur causing tooth to fracture.
Complete crowns are restorations that cover the entire tooth. They offer a better option by providing more stability than a large filling.
A crown is clearly a better option than a filling. As a person who grinds my teeth at night, I was often in severe pain when I had a cavity. The force of my bite would eventually cause breakage, and thinking I was doing the right thing both economically and time-wise, I opted for another filling. Eventually, the tooth would break and there would be the necessity for a root canal or in the worst case, tooth extraction.
Once again, a crown would have saved me money, time (in the long run) and most importantly, my tooth.
The choice between a crown or a filling is not always clear cut. Sometimes the best choice is a partial crown. A crown or partial crown will not only replace the missing tooth structure but also strengthen the tooth against fracturing. Tooth fractures are unpredictable and often result in the tooth needing a root canal or worse yet, extraction. Another factor to consider is how prone are you to decay and to tooth fracture. Some patients are more likely to get cavities than other and some have a heavy bite and are hard on their teeth. A crown would be a better and more predictable option for them.
Hi, thanks for a great article on how biting forces effect teeth with large fillings. I have recently broken a lower molar tooth with an amalgam filling. The tooth is now root canaled and I’m going to have a crown. So that tooth should be OK, but I am concerned about my other molars which all have fillings that to my eyes are similar size as the one in the broken tooth. These fillings are from my teenage years, eating a lot of sweets back then, but no new cavities for a longer period and this is my first broken tooth. You mention that large fillings are the problems – but what is a large filling? Does the filling material (amalgam vs composite) make any difference? What is a partial crown that you mention in an older answer?
I usually consider a large filling one that is larger than the remaining tooth structure. If the cusps of the tooth are thin and undermined, they are susceptible to fracture. It is impossible to predict how long they will last or when they may fracture, but preventative measures are more predictable in saving than trying to restore one after it fractures. Composite bonding is believed to be a stronger restoration than amalgam restorations. But a tooth is weaker than a crowned tooth. An onlay (3/4 crown is a partial crown) is a partial crown type restoration.
Thanks a lot for your comments /answers. If a large filling is one that is larger than the remaining tooth structure, then I will self-assess that I have only one large filling, while my other filling are “medium”, but typically on two tooth-sides (upper chewing surface and between the teeth). Thereby these teeth might have thin tooth walls and cusps and therefore be susceptible to fracture. So I will certainly have a talk with my dentist and have him to evaluate my fillings thoroughly and assess the risk of fractures and hoping that I will not be in need of too many crowns, which I can’t afford. New fillings will hopefully be OK not be too large.