Dental Caries (decay)
 

Where can I get Decay?

You can get dental caries on any tooth and technically on any surface of any tooth. In reality, areas that are harder to clean (and so collect more plaque) are the ones where we most often see cavities forming.

Nowadays the majority of decay occurs in between the back teeth- this is the reason why it is important to have dental X-rays and why it is so important to floss and use inter-proximal brushes.

The second most common place to get problems is in the patterns on the top of your teeth. Some people are lucky enough to have favourable patterns for cleaning- i.e. the cusps and the fissures are shallow and easily reached with a toothbrush.

However, if we contrast this with a complex pattern of deep pits and fissures, decay is much more likely to result. Sometimes these teeth can be fissure sealed to prevent problems and make cleaning easier. High-risk individuals may get decay on what we call 'smooth surfaces' such as the fronts and sides of teeth ,but because these areas are the easiest to clean, it is not a problem for most people.

Any areas which repeatedly trap plaque and food and those which are more difficult to clean, are more likely to get a cavity.

Root surfaces are also an area that is particularly vulnerable because they don't have the strong enamel overlying the tooth- this is discussed in more detail in 'root caries'.

What are the Types of Caries?

We can split dental caries up, via the area of the mouth, that it attacks. We can also name the dental caries by their progression through the tooth layers. We name the caries according to whether it has reached the enamel, the dentine, or the precious pulp.
  • Enamel caries
This means you have caries in the outside enamel surface of your tooth only. We can go a little further describing these caries as 'early' enamel caries; meaning it has just affected the outer part or 'late' enamel caries. It is still 'just' in enamel but much closer to the ADJ.
  • Dentine caries
This means the enamel caries has progressed through the enamel to reach the dentine layer of your tooth. Again, you can have 'early' dentine caries; meaning it is just through the other side of the ADJ or 'late' caries, more commonly referred to as 'deep' because it is much closer to the nerve.
  • Pulpal caries
This means the caries has progressed through the dentine into the pulp or nerve of the tooth- it's pretty much game over. If this happens the tooth will die and require extracting or a root canal treatment. Be warned- the caries doesn't even have to reach the pulp in order to cause the nerve to die- just get close enough so the damage is irreversible. See -'Irreversiblepulpitis' verses 'reversible pulpitis'.

There are two other types of dental caries we need to mention:
  • Arrested caries
Here the conditions in your mouth that led to you getting caries in the first place have changed for the better and the balance has been tipped in favour of remineralization. The caries is no longer active or progressing. Only if it poses a cosmetic problem does it need to filled, otherwise studies have shown that these arrested lesions are actually more resistant than a normal tooth to future caries- Interesting!

Arrested enamel caries is often a dark brown stain that won't come off with polishing and is ingrained into your tooth. It has a hard scratchy feel and is much darker than the soft more yellowy leathery feel of active decay. You often see this on the easy-to-clean surfaces such as the fronts and sides of your teeth, or in-between teeth where the conditions have changed due to a tooth been extracted and food/ plaque is no-longer getting stuck.


Caries can only be stopped predictably in its tracks, or even regress in it's early stages; that generally means at the enamel caries stage. Arrested dentine caries can happen, but it is much more rare- generally this occurs on root surfaces and the easy-to-clean fronts and sides of your teeth. In-between your teeth (where cleaning is most difficult), well, it's a different story and treatment is most often commenced as soon as 'caries into dentine' is detected.

The reason is that in order to arrest the caries, plaque must regularly be removed from the surface and in between your teeth; even the cleverest and strictest of flossers only have a tiny bit of string to try and remove the plaque. That's OK if the surface is still intact and smooth, but once it cavitates and you have a protected little indent in which plaque collects- your chances of doing this are slim and a filling is best done as soon as possible.
  • Recurrent caries
This is dental caries that occurs around an existing filling, crown or other type of restoration. Unfortunately the source of the problem- plaque, diet, lack of fluoride etc. that led to you needing dental work in the first place hasn't been rectified and a new caries has appeared at the margins of the restoration.

Whenever you have a filling, the margins (where the tooth and filling meet) are susceptible to 'recurrent caries'. The filling itself cannot decay but your tooth is still vulnerable and so steps should be taken to ensure this doesn't happen. Recurrent caries happens a lot less often than normal or 'primary' caries due to the fact that it is in the areas that are most difficult to clean- the least accessible, where you get the decay! Once you have had a filling, the margins tend to lie on the part of the tooth that is easier to keep clean and so problems become less likely.

Bitewing X-rays are particularly useful in diagnosing this, as most commonly it occurs in-between your teeth, underneath the approximal box of a filling. Without X-rays, problems in this area are hard to detect unless they are of a significant size. Recurrent caries around the inside or outside part of the filling are easier to see and can be detected by the probe getting stuck next to the filling, or by the appearance of the surrounding enamel which looks like half a moon halo.

If you have ditched margins and staining around your silver amalgam filling, this generally doesn't mean there is caries but the filling needs replacing. I have taken out a few of these silver fillings which looked suspicious, only to find there was no active decay underneath. Staining around your white fillings is also common and in the same way that staining itself doesn't mean decay, neither does this.