Why is my new filling sensitive?

 In Dental Care

Post Operative discomfort is extremely common following dental procedures, especially a filling. Let’s take a look at why it is there and what we can do to alleviate it!

What kind of material is used in my filling?

The most commonly used material for fillings in today’s dental society is composite. This composite is a resin composed of glass and plastic. This is a stark contrast to the silver fillings (also known as amalgam restorations) of old. Amalgam was used extensively due to its longevity and performance. Amalgam could withstand the harsh conditions of the oral cavity and was strong enough to provide adequate strength in chewing.

Although the amalgam had several positive qualities, there were a few important drawbacks. First, it contained small amounts of mercury. (Interesting fact – mercury exposure was the cause for the term “mad as a hatter” due to exposure in the hat manufacturing process!) Second, the amalgam is not completely set when the patient leaves the office. It is cured using a chemical process and will continue to harden as time goes by. The composite we use today is set with a curing light so it is completely set when you leave the office. It also does not contain any mercury allowing it to be tooth colored and possess better aesthetics. The image below shows the difference in aesthetics.

Why is my tooth sensitive after a filling?

Tooth decay is the most common cause for fillings. Bacteria eats away at the surrounding tooth structure when food and drink particles stay on tooth surfaces long-term. Removing the decay and replacing it with another material is the only way to maintain the integrity of the tooth. If left to grow, the decay will eventually lead to tooth loss. Your dentist will use a dental handpiece during the filling process to remove the existing decay and make room for the restorative materials. This process can slightly aggravate the nerve which is a very common cause of sensitivity after a filling. The nerve needs a chance to settle with the new filling material. This process can take up to a couple weeks or months to fully settle – depending on the tooth itself and the level of aggravation.

If the decay takes up a large percentage of the tooth, it is likely the dental work was near the nerve. In these cases, post operative sensitivity is almost always present to some degree.

What type of sensitivity is normal?

It is normal if you are experiencing minor sensitivity to hot and/or cold food and beverages. This is a good indicator that you are well within normal limits. If you experience pain that wakes you up at night or a dull ache that lasts all day, you need to be seen by your dentist again to evaluate the tooth. In these situations, a root canal can be the only method to completely remove the decay.

Sometimes a bite adjustment is required to correct the way the teeth come together with a new filling. This is a quick and simple procedure where we adjust the tooth structure we just filled slightly so the teeth hit in a more natural alignment. When you are numb from the filling, most patients bite a little differently than normal. It’s likely that when you are not numb we can adjust your bite and you will feel much more comfortable!

Tenderness at the injection site can also linger but typically not longer than a day or so. We recommend not having anything to eat or drink until the numbness wears off so you are not unintentionally chewing on your soft tissues like cheeks and tongue.


In conclusion, some sensitivity is normal. Your mouth, just like the rest of your body, can take a little bit of time to heal and go back to normal. When you introduce a new material to the body there is also a minor adjustment period and the same is true for fillings. If you want to take something to help with the tenderness, an over the counter pain reliever will be helpful!

Recommended Posts