Once a cavity in your tooth has been filled, you probably won't think about it any further. The damage has been done, but this damage was repaired by your dentist, and as far as you're concerned—that's the end of that. But while a dental filling is intended to stand the test of time, it's not going to stay intact indefinitely. It's almost simpler when a filling cracks or falls out—this is at least definitive proof that your filling must be replaced. Not all fillings are so cooperative, and signs of their impending failure could be harder to spot, especially if the filling is simply overhanging.

When a Filling Overhangs

An overhanging filling is when the filling shifts within the cavity it had previously filled. It can literally overhang the edges of the carious lesion beneath it. This may be quite conspicuous—felt as a small bump or groove, often noticed by your tongue. Other overhanging fillings may not be noted in this way, and don't become perceptible until the tooth begins to show signs of distress.

Increased Discomfort

This distress is generally felt as thermal sensitivity. Without the exhaustive barrier created by the filling, the tooth's dentin has been exposed, which is ordinarily shielded by your dental enamel, and any dental restorations present in the tooth (such as your filling). Dentin has microscopic canals leading from its surface to the dental pulp (nerve) inside the tooth. An overhanging filling can allow the tooth's nerve to register the temperature extremes of various foods and drinks, and this is not a pleasant sensation.

What Can Cause the Issue

The problem arises from what is generally just a combination of the age of the restoration, coupled with the natural wear and tear that a tooth experiences. The restoration itself is reactive (which varies depending on the material used), and can expand and contract in response to temperature and moisture, contributing to its gradual overhang. In any event, you should schedule an appointment with your dentist.

Having the Issue Corrected

Your dentist will typically just remove and replace the filling, and it's often as simple as that. Obviously, the tooth itself will be thoroughly inspected. The cavity beneath the filling may have deepened, which could have destabilised the filling's foundation, causing it to loosen. In this instance, a more extensive restoration may be needed. 

An overhanging filling isn't all that serious, but it needs to be corrected, as the filling is no longer protecting your tooth from external contaminants and corrosive agents.

For more information, contact a dentist near you.