When fluoride was introduced into the Australian water supplies in the 1960's it was intended that such fluoride would be ingested by children and incorporated into their tooth enamel and confer on them the life time benefits of reduced rates of decay. This has happened and it has been a major success in preventive dentistry — 60% overall reduction in decay, but a 90% decrease in the front teeth!

However there have been some unintended consequences of the introduction of fluoride into the water. The one of relevance to this document refers to the way in which decay operates within a tooth. Fluoride causes a tremendous increase in the hardness of the enamel (a decrease in the solubility of the enamel in response to an acid attack caused by plaque). Decay does not become so evident to the dentist as it did previously. Instead of the decay forming an open cavity which was easily visualised and easily felt by a sharp metal probe. Decay now tends to start inside a tooth. This is because the bacteria and saliva can get through at the very fine crack on the surface (we call this the fissure) and commence decaying at the softer portion of the tooth inside called the dentine. As a result of this the decay can go undetected for many, many years and ends up in what dentists refer to now as a 'fluoride bomb'. The inside of the tooth is completely decayed and the outside looks fairly normal — sometimes there is a slight discolouration evident through the enamel, but often the decay can not even be felt with a sharp metal probe — this is scary stuff to dentists because for decades we have relied on diagnosis of decay by feeling the softening of the enamel with a metal probe.We can no longer do this.

To overcome these problems two treatments have been devised. The first is called a fissure sealant . This was traditionally done about 5-20 years ago and was tested and proven in America to make a significant difference to the progress of decay. The fissure sealant is a clear plastic resin, or sometimes a white resin which is put onto the surface of the tooth and bonded on there by a means of enamel bonding. Although this tended to work reasonably well the fissure sealants fell out at a pretty high rate and gradually, with time, fissure sealants fell into disrepute, which culminated in the World Health Organisation recommending that they not be done because of the high incident of recurrent caries (new decay) around the edge of fissure sealants that were stuck at one end and not the other.

A preventive resin restoration is a more definitive treatment for sealing out decay on teeth. These involve cleaning out the groove (fissure) of the tooth rather than just burying it under plastic. The groove can either be cleaned out by an air abrasion device or (as is more commonly used) just a conventional drill. There are advantages and disadvantages to each cleaning device. The air abrasion device has no vibration and very little noise, other than a hiss. However it dose make a fair amount of mess in the mouth from the particles of aluminium oxide which are used to create the abrasive effect. The drill is quick and clean, but somewhat noisy. Neither technique causes any significant amount of pain at all. (Really!)

Once the groove has been cleaned out a proper assessment can be made as to whether there is any decay underneath the groove. If there is decay there (and decay is found in a surprising number of cases) then the decay is removed with either of the devices mentioned above. Quite often the decay can be completely removed without any pain at all , or without the need for injections. This is particularly true in cases of very shallow decay. If however, the decay gets deeper into the tooth (as happens in about 5% of cases) a local anaesthetic may be required to numb the tooth so that the decay can be removed properly without causing undue discomfort. Once the decay has been removed the tooth can then be filled up using conventional filling techniques. Usually a tooth coloured white filling is used, which is bonded into the tooth.

If no decay is discovered after cleaning out the fissure, the tooth is bonded and filled with identical white filling materials. The tooth is treated with a mild acid gel in order to promote excellent adhesion, a bonding resin is applied, followed by a putty of white plastic material or a semi liquid (flowable) composite resin. It is injected into the grooves and then light cured to harden it. This makes a beautiful, durable white filling in the groove which is sealed very effectively to the enamel. This fills the groove up and stops food becoming caught there and thus stops the decay establishing itself under the enamel of these molars or premolars.

This is truly a remarkable advance in preventive dentistry — and children and adults treated like this can expect 10-20 years of service from these small restorations. This treatment is so effective, we consider it essential, not optional, that all children have their first and second molars treated as soon as is practical, after their complete emergence from the gum. This happens at ages 6-7 and 12-13.

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