Dental Caries (decay)
 

How does Decay Progress?

In order to understand this we need to know some basic tooth anatomy:

  • Enamel is the hard outside layer of the tooth, it is whiter in colour. It has no nerve endings and is made of crystals called 'hydroxyapetiate'. It is the hardest substance in the body which explains why the teeth are used to identify bodies when little else remains e.g. due to fire. Enamel can demineralise and remineralise as we have seen but you can't grow it once it has been lost.
  • ADJ.This is the border where enamel meets dentine. It stands for 'amelo- dentinal junction'. 'Amelo' means enamel and comes from the word 'ameloblast' which is the cell that makes enamel when your tooth is developing.
  • Dentine is the second layer. It is much yellower in colour than enamel and much softer. It is made of thousands of tiny tubes that connect the outside enamel to the inside pulp. These tubes contain a liquid called 'dentinal fluid' which helps to supply nutrients to the tooth. This is a living layer that helps protect the nerve inside the tooth. If something threatens the nerve more dentine will be laid down by specialist cells called, 'dentinoblasts' to try and protect it- the increased thickness of dentine will mean dental caries will take longer to reach the nerve. This is called, 'secondary dentine'.
  • Pulp. This is the life and soul of the tooth. It contains the all important dental nerves but also blood vessels that allow the teeth to live, bringing in nutrients and taking away waste. It is the heart of the tooth that we try to protect at all costs. It is the source of pain and sensitivy and when treating teeth; all efforts are made to preserve a living pulp. A root canal treatment removes all of this and fills in the space with a filling material, once it has been suitably cleaned. It is like preserving a body in formaldehyde- the soul has gone and the person is no longer living, but the body remains.
This is the basic process for untreated dental decay:

Let's say you have a small hole in your tooth. If you didn't see a dentist and continued doing exactly the same things as you are now- that's no change in diet, no extra fluoride or improved cleaning- then the process of dental decay is set to progress:

Enamel caries---> Dentine caries---> Pulpal caries---> Pulp death---> Abcess formation.



(Unless caries is on the root of your tooth = root caries; in which case no enamel exists).

What exactly happens in Dental Caries?

Let me walk you through it:


Demineralisation is occurring more than remineralisation and caries (bacteria) is making in-roads on your tooth.

Dental caries progresses slowly through your enamel, (enamel caries) due to its strength and the protection of saliva, until it hits the border with the dentine (ADJ) where it is sent off on a bit of a wild goose chase in an attempt by your tooth to protect the nerve. The caries spreads out along the border for a while, before eventually overcoming this barrier and making its way through and into the dentine.

Dentine is not as hard as enamel and because it is made of tubes, the caries progresses quicker than before (dentine caries). Whilst being weaker, dentine is a living a tissue and reacts by laying down more and more tubes, shrinking the nerve away from the harmful caries. This is called 'secondary dentine' or 'reactionary dentine' and occurs in response to a deep attack.

Once in dentine, it is likely that you will begin to experience some symptoms, as the nerve in your tooth begins to be affected and the nerve inside swells slightly (pulpitis). This small amount of inflammation is known as 'reversible pulpitis'. The caries will continue towards the nerve- unless stopped with a filling- and the closer it gets the more irreversible the swelling of the nerve will become, 'irreversible pulpitis'.

Soon the swelling will be so great, that the blood vessels supplying the tooth through the small entrance at the base of the root called the 'apical foramina', are strangled, causing the nerve to die off. We call this 'pulpal necrosis' and so ends the life of your tooth.

Important. The sooner we catch the caries, the easier it is to stop and reverse it- yet another reason for frequent dental visits! The deeper it progresses, the more extensive and expensive your treatment will become.

Eventually the bacteria will infect the root canal system causing 'periapical periodontitis'. 'Peri', meaning around, 'apical' meaning the end of your tooth. Also 'perio' short for 'periodonitum' (or the supporting structure of your teeth; the bone/ligaments etc.) and 'itis' meaning inflammation. Put it all together and you have an 'inflammation in the periodontal tissues around the end of your tooth'. Not to be confused with Periodontal disease which is something completely separate.

This can be an acute inflammation accompanied by pain and swelling, redness and heat, or a chronic inflammation, where a longer-term balance between your body and the bacteria is set up. Acute periodontitis is painful. The tooth more often than not is very sore to bite on and some times even sensitive to touch. Chronic periodontitis isn't painful and often discovered incidentally on an X-ray. However, just to make it extra confusing for you, 'chronic' can quite easily become 'acute' and vice versa- it just depends on the virilant (how nasty) the bacteria are and of course, your immune system's ability to keep them at bay.

Acute or chronic periodontitis can lead to a dental abcess (collection of pus) which you will surely know about. The tooth at this point will definitely become very painful, because there are so many nerve endings in the ligament surrounding the tooth. That is, unless the infection has a place to drain- a 'sinus'. This is where the infection from the end of the tooth makes it way out onto your gum somewhere near the offending tooth. A little boil or blip, through which pus and infection can escape is often seen, felt and commonly tasted (not very nice). As long as this tract remains open, pain is unlikely as there is no build up of pressure. If it gets blocked- Boom = Pain.

An abcess can be so small and hardly noticeable but very painful, often just pushing the tooth up in its socket only a millimetre, or your face can swell to the size of a football and make you look as if you'd gone 5 rounds with Mike Tyson.

Spreading infection is a serious consequence that is quite rare, but it can occur. This 'dental cellulitis' means the infection is no-longer confined to the tissues around the problem tooth and begins spreading through your facisal planes entering other tissues. It requires immediate antibiotics and sometimes even hospitalization.