What does a filling involve? An inside look
by Dr Aaron McMurtrie
Very rarely is a filling just a filling. It a common misconception that people think we scrape out the gunge, whack in some putty and wander off in search of a cup of coffee. This could not be further from the truth. A more accurate term is “restoration”. We use the word filling because it has less syllables.
On the rare occasion that the task begins to resemble the above, the challenge is in the detail. Firstly, the decay must be removed with care and precision to minimise loss of remaining tooth structure, avoid the important bits and maintain the vitality of tooth. This is often done upside down, in the dark, under water, on a moving target, while looking through a mirror with water running across it. Surprisingly, with practice, we have become very good at this. And not surprisingly, I have met many dentists who drive cars in the rain, without using the windscreen wipers. It drives their partners crazy.
Next, the cavity must be dried and remain dry for the restoration. Did I mention the underwater bit? Those cotton logs aren’t just there to see how many we can fit in. You could pack some brands of the old silver amalgams wet, but that stopped in about 1995. A restoration must seal out the wet, the air and the bacteria swimming around looking for somewhere to play. It must insulate against that next hot cup of tea or coffee that somehow managed exceed the boiling point of water as well as accompany you on your next sub-zero adventure into an ice cream Sunday. The same construction must go into battle with that piece of bone that you inadvertently left in the chicken sandwich and the acidic dry wine you used to washed it down. In fact, anything within the range of the bite means the opposing teeth want to beat the living daylights out of your beautiful new restoration and tooth surrounding it. Often that remaining tooth has been weakened by the decay.
Then the sides fall off and that’s when the real engineering starts. The restoration must be designed with load bearing footings, retention interlocks, a cross sectional thickness and some means of defending and protecting the remaining tooth structure, all achieved with a flick of a drill, underwater, in the dark, in a mirror. Like the old children’s show “Mr Squiggle” where a few lines are presented and the character must draw a picture incorporating the lines, the dentist assesses the remaining tooth and formulates a design that will survive it, all on the fly. This is where the dentist brings something to the party. Often by identifying the reason the tooth has failed, the design improvements of the new restoration give you the best opportunity to not have to come back with the same tooth broken again in four, five or six years down the track. It is a source of enormous satisfaction for a dentist to find their old restorations going strong up to 30 years after they have been placed. But that can only be achieved with good oral hygiene and care.
Then there are the occasional teeth that will exceed the capabilities of the restorative material itself. That is when a crown becomes the only viable solution and a whole new story begins.
So, as you can see, fillings are often a busy little construction site. That is why your dentist is always trying to put themselves out of business harping on about brushing twice a day, flossing at least once a day and watching what you put in your mouth. They would rather be off looking for that cup of coffee.