It's remarkably easy to forget that a tooth was ever affected by a cavity. The composite resin your dentist used to repair the decayed portion of the tooth is the same colour as the surrounding tooth surface. As such, the filling blends right into the tooth, becoming invisible. There are a few signals that your tooth will soon remind you of its former cavity, meaning it's time to make an appointment with your dentist.

The Life of a Filling

A composite filling lasts (on average) seven years. This is a very rough guideline, since there are many factors that can either shorten or extend the life of your dental restoration. Being less conscientious about brushing your teeth, grinding your teeth and eating a sugar-rich diet can all cause damage to the tooth structure that surrounds the filling, shortening the lifespan of the resin restoration. Conversely, those who take great care of their teeth can keep the filling functional for much longer. 

Covering the Hole

The functionality of a filling relates to its effectiveness of covering the hole in the tooth—a hole that was initially caused by decay, which was then expanded (drilled) by a dentist to remove all traces of this decay (thus preventing it from worsening) before the resulting cavity was filled with resin. As resin reaches the tail end of its usefulness, it may retract from the edges of the tooth. Some degree of micro-shrinkage is common in dental resin, which isn't surprising if you think about it.


Dental resin is consistently exposed to moisture (saliva) and may dry out when your mouth dries out. It also experiences significant pressure (occlusal bite force), as well as extreme temperature fluctuations depending on the temperatures of the food and drinks you consume. All of this can cause the resin to expand and then retract. The progression of micro-shrinkage can cause the resin to pull away from the very edges of the tooth, allowing leakage into the inner reaches of the tooth. This allows bacteria inside your tooth, and this can lead to some sensitivity and irritation.


Bacteria may be irritating the tooth's nerve, which is no longer adequately protected by the resin filling. This isn't a major issue, but failure to seek treatment can allow the nerve to become infected, which is a major issue that often requires root canal treatment. You may not be able to see the retraction of a resin filling, but in some cases, you'll notice a small dark line around the filling—meaning it's no longer invisible.

If you notice any suspicious sensitivity (or any changes whatsoever) to a tooth with a composite resin filling, it's time to see your dentist. Replacing a resin filling is an extremely small task, but it's an extremely important one.

Contact your dentist to learn more.