Dental Education Lecture: How to Get a Good Permanent Filling?

Sometimes our old filling comes out and we have to redo it. How can we avoid the hassle, i.e., to get a good hopefully permanent filling in the first place?  The longevity or quality of filling is mainly dependent of dentist ability.  But as patients, we can make it easy for the doctor to do it right.  First of all, we need to see a dentist on a regular basis to find out the earliest cavity.  The smaller the cavity, the easier for the doctor to fill it.  Fig.1 shows two fillings (F).  The one of the left is moderately large, whereas the one on the right is extremely large.   The filling on the left is fairly well done with smooth transition from the filling to our root (arrow).  By contrast, the filling on the right is relatively poor done with an obvious step between the filling (red line) and our tooth structure ((blue lines; X-ray showing the surface (instead of the line) of this portion of root so that two lines are depicted).  The step causes food entrapment between two neighboring teeth.  Your gums are irritated and easily bleed.  Floss may be caught and torn.  This patient needs these two fillings because of lack of using floss.  

Sometimes the doctor wants to be conservative, removing the cavity and placing a filling from the side. It creates a serious problem.  Let us use Fig.2 to demonstrate the point.  A filling is done on the tooth on the right side. A red curved line represents the outline of the filling.  Due to poor angulation, the cavity (blue curved line) appears to have not been completely removed.  The filling is done when the neighboring tooth is prepared for a crown (C).   Incompletely removed cavity may enlarge and cause nerve infection in near future (black arrowhead), since the cavity is pretty close to the nerve (green outline) and the tooth may also need root canal (therapy) like its neighbor (green arrowhead).  If you are interested, you can read the lecture Sensitivity after Filling to understand how the residual cavity affects our tooth.  The crown on the left of Fig.2 is not done properly.  We draw red lines to represent its edges against the tooth surfaces (blue lines).  The uneven edges causes food entrapment as well.  In all, as patients, we should have good daily oral hygiene habit, such as flossing, see a dentist regularly and get filling done as soon as possible to avoid annoying consequences.

Xin Wei, DDS, PhD, MS 1st edition 02/11/2009, last revision 01/04/2011