Dental Education Lecture: Sensitivity after Filling

Sensitivity is fairly common after filling.  We are going to use illustrations to explain why.  Fig.1 shows two upper front teeth.  Two cavities develop on the side of these two teeth (black, Fig.2) due to the fact that we do not floss.  We have to fix them by filling (gray, Fig.3). 

As discussed in Tooth Structure, there is pulp (so-called nerve) in the middle of our tooth (single arrow, Fig.4.  As we get older, the pulp becomes receding (double arrows) and narrower.  If a cavity is small and the pulp is receded as shown in the tooth on your right of Fig.5, you may not experience any discomfort after filling (right side of Fig.6).  By contrast, if you have a large cavity with some discomfort and your pulp is huge, the pulp may be not so healthy before filling (gray in Fig.5).  Your pulp suffers more stress (dark gray Fig.6) when the doctor uses high-speed bur to remove cavity and places a filling material.  This is one of possible reasons that you experience sensitivity after filling.  Sensitivity is defined as temporary pain after drinking cold water or sour food.  After the irritant is removed, your tooth is apparently free of pain.

The stressed pulp may recover to normal or get worse in time (red in Fig.7).  The infection may spread to the whole pulp (Fig.8).  By that time, your pain is more severe.  You have pain even in absence of an irritant and you have difficulty lying down for rest.  We need root canal (therapy) for pain alleviation.  We have briefly discussed root canal in last lecture.

Some people have no discomfort after filling.  But several years later, they have pain.  Let us use Fig.9 and 10 to explain two reasons.  The first one is shown in the tooth on your left side. The doctor does not remove all of sugar bugs before filling.  The residual cavity inside the tooth (black in Fig.9) gradually enlarges and invades the pulp (Fig.10).  The second reason is demonstrated on your right side of Fig.9 and 10.  The doctor does a good job, but the patient does not use floss after filling.  A new cavity starts on the surface of the tooth (Fig.9) and becomes large and encroaches the pulp in a few years.  The new large cavity may cause the old filling to come out (arrow in Fig.10).

To avoid pain and discomfort mentioned above, we should practice the best oral hygiene by brushing right and flossing daily.  We need to see dentist before we think that we have any problem.  Meticulous clinical and X-ray exam can detect early small cavities.  Try to get filling done as soon as possible.  All of these measures can reduce possibility of  post-operative tooth sensitivity.  After filling, you have to learn flossing and keep doing so all of your life.

Xin Wei, DDS, PhD, MS 1st edition 01/27/2009, last revision 04/18/2012