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What happens when you get a filling?

Want to know what is happening when you get a filling? Learning time!

Emax porcelain onlay on lower right first molar with articulating paper marks

Why do you need a filling?

For simplicity, let's presume you need a filling because of tooth decay. Other reasons are you chipped a tooth or it is worn out from grinding or brushing too hard. These are pretty easy to understand.

Tooth decay is a hole in your tooth. This develops when the bacteria on your teeth turn sugar and carbohydrates into acid. As tooth is mostly made up of mineral, acid will dissolve the enamel. This makes it soft and mushy, which breaks and becomes a cavity. When there is a cavity, it is the perfect home for germs and sugar to stay in; It is impossible to rinse or clean the hole. With such a happy place to live in, they can be more active and increase the speed of decay.

If left untreated, the decay will reach the nerve of the tooth and eventually the entire tooth will be destroyed.

What is the point of a filling?

The purpose of a filling is to stop the progression of decay and restore the tooth to become strong, useful, comfortable and make you socially acceptable.

What is the procedure?

Usually the tooth is anesthetised so you don't feel any pain. I prefer numbing the tooth so that I don't have to worry about hurting you.

Once the tooth is numb, the decay is removed. The fastest way is to use the drill to remove the mushy parts, so that there is no more paradise for the germs. The dentist will then poke around the tooth to ensure only healthy tooth is remaining. Attention to detail to ensure that all the decay has been removed is critical.

Next is the preparation of the tooth for the filling. For a white filling, the tooth needs to develop a surface for the filling to stick to. This will involve etching the surface and using a special liquid, called bond. Etching achieves different results on the two layers of teeth. On enamel. it microscopically roughens the surface. On dentine (the inner layer), it exposes collagen fibres to the surface. The time that the etch is in contact with the tooth is very important, and enamel and dentine require different durations. Too long or too short will result in a weak filling.

Bond will flow into the roughness of the enamel and chemically attach to the collagen fibres. Importantly, moisture must be kept away for a strong filling. It is then cured by a strong blue light. This is the beeping machine that gets put in your mouth.

The filling material, called composite resin, will now be placed. It is normally placed in small sections and cured, because it will shrink when cured. When uncured, it is soft and mouldable. The blue light is shone onto the tooth and it hardens by polymerisation (There's a lot of HSC chemistry principles!). We must make sure the resin is fully polymerised for a strong filling.

Once the filling is fully filled, it is adjusted to fit your bite, then polished. To check the bite, the dentist gets you to bite on a thin paper that marks where the teeth touch. Polishing ensures that it feels comfortable and looks good.

With all the steps above, each one is very important in achieving a long lasting filling. If one step is not done well, it all falls apart. There are also different qualities of bond and composite resin.

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