Most of the columns I write are based on the questions that I am asked routinely by my own patients. One of the most frequently posed questions is, “How long should a filling last?”
The question is a very good one, because it is relevant to anyone who has ever had dental work done. It is also a hard question to answer, because the answer varies greatly from one patient to another, and it is dependent on so many factors. If you were to ask an auto mechanic how long brakes or tires should last, you might get an answer based on statistical averages. But you would also be told that lifespan varies greatly, depending on factors such as driving habits, climate, road conditions, whether the tires are kept at the proper inflation, whether the tires are rotated regularly, and many others.
The same is true of fillings, and of all types of dental work, for that matter. The statistical industry average lifespan of a filling is 10-12 years. However, we routinely see patients with fillings that have been in place for 30-40 years, and unfortunately, those whose fillings last only a few short years as well. Why, then, is there such a vast difference from one mouth to another?
First, we have to consider the factors that are non-modifiable – the factors that patients have no control over.
Most important is the pH (acidity) of the saliva. Those people who have more acidic saliva are high risk for new cavities, and very high risk for recurrent cavities at the edges of their fillings. Hyper-acidity in the mouth will shorten the lifespan of fillings severely.
Then there is the strength of the jaw muscles. Those people with a heavy set jaw or strong jaw musculature place far more force on their teeth and fillings when they chew, resulting in higher risk for premature breakage or wear of fillings. In fact, heavy jaw muscles can generate more than 1,000 psi (pounds per square inch) of force on back teeth! That’s a huge amount of force, when you consider that the average automobile tire is inflated to 35 psi. As well, patients with straight teeth and an ideal bite have less wear and tear on their teeth, since the chewing weight is borne equally by all teeth (this factor is somewhat modifiable, when you consider that orthodontic treatment can idealize the arrangement and alignment of teeth).
There are also a number of factors that are modifiable by the patient.
First and foremost, regular brushing and flossing is crucial to increasing the lifespan of fillings. In particular, flossing can literally double the longevity of a filling in between teeth.
Regular check-up and cleaning appointments similarly add to the longevity of fillings, since removal of plaque and tartar from the edges of fillings reduces the risk of cavities at the edge of fillings.
Diet is also very important. Diets that are high in sugar and acidity (for example, citrus fruits, candy and snacks) often result in premature failure of fillings. There are also some obvious chewing and biting habits to avoid – chewing on ice, opening shells of nuts, biting of fingernails, opening packaging with teeth and holding pens or pencils between the teeth are just a few of the many examples we hear about. Of course, there are also the inadvertent dental ‘mishaps’, such as accidental biting on an olive pit, popcorn kernel or peppercorn.
As you might imagine, those patients who clench or grind their teeth need much more frequent replacement of their fillings. Although we cannot teach a ‘grinder’ not to grind, we can reduce this risk by fabricating a night guard. Dental appliances worn during sleep do not stop grinding or clenching, but they completely eliminate undue wear on the teeth during the night, when the majority of grinding and clenching takes place.
You can see how all of these factors would influence heavily the lifespan of a filling. The same factors apply to crowns, veneers, bridges and even dental implants. If you have concerns about frequent replacement of dental work, talk to your dentist about how you can get more mileage from your dentistry.