When a filling breaks

When a filling breaks, do I need to get it fixed right away?

There are three layers of tooth structure on the part of the tooth that is normally visible above the gums (the crown of the tooth). From the outside working in, they are: enamel, dentin, and pulp (nerve). Since tooth decay is caused from acid produced by bacteria in dental plaque (the soft white stuff that forms on the OUTSIDE of teeth), cavities always start on the outside of the tooth and work their way in. The enamel is damaged by the acid in plaque first, then the dentin, and finally, the pulp (nerve). Decay in each of the layers of a tooth is treated in very different ways.

Decay that has just started its course of damage to a tooth is found in the outer layer only--the enamel. In the beginning, the decayed area of tooth structure looks like a white or brownish line or patch where plaque is routinely left on the surface of the tooth. Typically the area is along the gum line of the tooth or between teeth. At this stage, careful removal of plaque several times a day will actually make the damage to the tooth reverse. Fluoride in fairly large concentrations (like in toothpaste or other preparations) will speed this reversal (also called remineralization) of decay. Reversal of decay in enamel is slow. The process will take months or even years. Some people get areas of enamel decay (also called demineralization) filled so they will not have to think about them any more. At a dental checkup, the dentist may say he or she wants to "watch" certain areas. Areas of enamel decay are typically the spots he wants to "watch" since the patient may be diligent enough with brushing and flossing to allow the damage in the area to disappear. If the patient seems uninterested in redoubling his efforts at plaque removal, the dentist may advise the patient to get the area filled since at this point, without a change in home care habits, decay in the enamel will certainly progress into the dentin.

After decay has dissolved all of the enamel on an area of a tooth, it will enter the dentin. Dentin is softer than enamel, so when tooth decay enters this layer of tooth structure, it gets much larger. The decay process progresses faster than it did in the enamel. Enamel on the surface of the tooth above decayed dentin will now begin to come off in chips. Tooth decay in dentin is not reversible. Because of this fact, delay is not a beneficial step since it will result in a deeper filling. Decay in the dentin is treated by its removal in the dentin and the enamel and replacement of the tooth structure with something else. There are many choices of materials to place in the hole caused by decay into the dentin: silver alloy, composite (plastic), porcelain, gold, etc. Each has its advantages and disadvantages, and the size and position of the hole left by removal of decay may make one material choice much better or worse than the others. You should talk with your dentist about materials to fill cavities if that interests you. Since enamel decay is rarely filled, nearly all fillings are placed due to decay that has passed through enamel and into the dentin. If a filling falls out, it is either because the filling has broken, or because the hole the filling was placed into has become larger. A hole where a filling is placed gets larger either because some of the surrounding tooth structure has broken off or because there is new tooth decay under or around the old filling. This makes it important to get the site where the filling fell out looked after without delay to avoid decay reaching deeper into the tooth. The deeper decay gets in a tooth, the closer it gets to the pulp (nerve).

Decay that reaches the pulp (nerve) of a tooth has already progressed through the enamel and the dentin. Most teeth with decay into the pulp are painful since the action of bacteria in dental plaque causes the pulp to abscess (become infected). A filling will not solve the problem of decay entering the pulp. In a case like this, the pulp must be removed. To remove the pulp, the tooth either must be extracted or a root canal must be done. Decay left untreated when it has entered the dentin will always end up entering the pulp. Without earlier treatment, the outcome is certain. Treatment when decay has entered the pulp is drastic. It is far better to get the tooth looked after before decay has progressed this far. Sometimes a filling that is very deep in the dentin can cause the pulp underneath the dentin to become so inflamed that the tooth becomes abscessed even though decay never entered the pulp space. As you can see, when a filling falls out, the tooth should be looked after without delay to avoid further damage.


This article was written by Dr. Mike Christensen and published in the Daily Miner and News, and Enterprise. Local Kenora News Publicatons (1998-2006)