Still by far the most common reason for a filling is decay. Sugar and bacteria combine to create acid. This acid attacks the enamel, and as the enamel dissolves the bacteria progress deeper into the tooth or around the old filling. It is the result of a simple chemical reaction. The less the quantity of sugar and, just as importantly, the less frequently you take the sugar, the slower the decay will progress.
As the bacteria approach the core of the tooth (the pulp ) you will get sensitivity from hot, cold, or sweet food and drink. Initially the pain may last only a few minutes, but as the cavity gets deeper the pain lingers longer with each episode. At a certain point the nerve tissue of your tooth becomes irreversibly damaged and either root canal treatment or extraction will be required.
As a simple rule, the earlier a cavity is diagnosed, the greater your chance of saving the tooth easily. A good analogy I often discuss with patients is if you have a slate loose on the roof, do not wait until there is water in the bedroom. It will always be simpler and less costly to fix the slate and prevent more extensive and expensive damage.
Replacement of old fillings
The seal of old fillings can eventually leak and need to be replaced. Different materials have different mechanical properties, and abilities to withstand the rigours of the day to day mechanical and chemical loads that consistently batter your teeth while eating and sleeping.
It really is a remarkable achievement that these materials survive the wear and tear we give them for so long, but eventually either the bond of the filling to the tooth, the filling material itself, or the surrounding tooth structure fails from chemical attack or mechanical load. The bigger the filling compared to the tooth, the higher the risk of failure and the greater the need for a stronger alternative.
Tooth fracture and cracking
The filling is fine but the tooth around it has broken. With the forces we put on our teeth for many years, eventually something has to give. Enamel and dentine are immensely strong and able to resist biting forces, but a cavity or filling always weakens the integral crystalline structure of the tooth.
Whether a cusp (corner ) of the tooth breaks, or the fracture extends onto the root, will determine the survival and the choices of material and techniques your dentist can offer. Each time a filling has to be replaced, it is likely to increase in size. Early detection of a failing filling will reduce the size of the replacement. The stronger the replacement filling, and the better your oral hygiene and diet, the longer it will last.
Dr Paul Moore BDS