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How does the Dentist Decide if I Need a Filling?

Nov 30, 2016Posted by nameless

It is important that you regularly see a dentist because not all decay and problems give rise to symptoms or pain. In fact most start silently in the early stages, and if picked up early can mean a simple treatment (sometimes even just preventive treatment) instead of a more expensive and complex procedure.

The dentist will check if you need fillings by examining the teeth and taking Xrays if necessary.

When the dentist is performing a check up they will look at each tooth individually and check everything is fine. They are looking for the reasons that teeth may need to be filled or refilled including tooth decay and any problems with existing fillings. When looking at tooth, it is necessary to dry the tooth with some air to remove the saliva that is coating it. This allows a much clearer view and more accurate diagnosis.

The dentist may poke gently around any nooks and crannies in the tops and sides of your teeth that look suspicious with the dental probe. Sometimes it is difficult to tell if something is just staining or if there is some decay happening. If a dark area is firm and scratchy to the probe, it suggests that it may just be staining and in this case the tooth should simply be watched and checked at the next recall appointment.

In some circumstances where it looks particularly vulnerable, fluoride may be applied or a sealant restoration placed. If however the probe sticks, then this suggests some decay is occurring underneath and causing the tooth to be softened.

The tooth should then be opened up and filled and not left to continue to grow out of sight. It is highly unlikely that decay in these areas can be reversed by improved oral hygiene and fluoride, as it often can at some other sites.

In my experience, in nearly all fillings discovered in this way (via ‘sticky fissure’), the decay has progressed into the dentine layer of the tooth.

Sometimes it is hard to believe just how much decay has occurred underneath, when the top tooth looks apparently normal. If undiscovered part of the tooth will eventually collapse in on itself, at which point the state of the nerve and long term success become questionable. Fluoride is largely responsible for remineralising the surface and keeping it intact and apparently normal looking, thus hiding the damage from view.


The general view for assessing decay and deciding if you need a filling is called a BITE WING radiograph. This shows the dentist a side view of all the molar teeth on the top and bottom of your mouth. The section on bitewing X-rays will show you how the dentist identifies decay and tells if you need a filling.

We take these screening X-rays routinely every two years if you have a low risk of decay to check in between the teeth for any signs of a cavity and assess your fillings for problems. If you are a high caries risk and regularly need fillings at your check up appointment or if some early decay is being monitored, then X-rays may be taken more frequently.

It is important that you have these pictures, since it can help detect problems early, thus preventing more extensive and expensive treatment at a later date.

Dentists who tell you that you need X-rays every 6 months without a good reason (which should be explained to you) however, may be exposing you to unnecessary radiation . Don’t be scared to speak up and ask why they are needed and what the current professional guidelines are for taking routine dental X-rays.

We generally don’t need to take X-rays of the front teeth because they are thinner and we can shine a light with our mirror to detect if any decay is taking place and if there are any fillings to be done.

If you are having dental pain/toothache or have dental caries that is deep into dentine, your dentist may want to take a periapical radiograph to let them see the whole root to check for any apical changes (around the tip of the root) that may suggest the nerve in the tooth has died. The history of your pain and other special investigations will help the dentist build a picture of your problem and decide on the appropriate treatment since it may not just be a filling, a root canal treatment or extraction may be required.