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Thank you for your very pertinent questions which are highly relevant. The fact is that we do not know how often to disturb the biofilm. We do not know if it alone is sufficient to influence initiation of lesions. All we know is that, if you ensure that fluoride is available in the oral cavity (from fluoride toothpastes, water, etc) whenever there are pH fluctuations in the biofilm we can influence the de- and re-mineralization dynamics. However, regular (once or twice daily) oral hygiene removes excessive amounts of what we used to call dental plaque or disturbs the biofilm so that this facilitates fluoride ion access to the interface between enamel and biofilm.
When it comes to established cavities, we have since the days of Black and later Anderson, Massler and others, known that removal of the plaque/biofilm in the cavities is sufficient to arrest further lesion progression. Again, if the fluoride ion activity is slightly elevated in the oral fluids, it helps significantly. Example: occlusal cavities should be ‘opened up’ to facilitate keeping the cavity clean – eventually by mastication – and further lesion progression is inhibited. This is ‘old’ knowledge which has been largely ignored since we had the high-speed drill entering the market almost 60 years ago. This is the case in both dentitions and, if appreciated, could prevent children from having a lot of drilling and filling.
What about interdental areas and deep fissures? If occlusal and ordinary approximal plaque removal is performed every day, there is no problem. Dental caries does not develop in the depth of the fissure, but at the entrance – and if the entrance is kept clean nothing happens in the deep microbiota, even when you apply 10% sucrose at the entrance twice daily and allow it to sieve to the bottom for 1–2 minutes – these experiments have been made in man.
Fluctuations in pH in biofilms always happen at random. However, the lower and longer a pH drop becomes, the more influence there is on the rate of lesion development. So any influence on pH drops in biofilm is likely to play a ‘protective’ role. It is interesting that pH measurements intra-orally show a distinct difference between lesions clinically characterized as active or inactive. In the inactive lesions the drop is much less and returns to normal physiological level much sooner after a controlled rinse with sucrose. But biofilms will always metabolize and even some of the sugar alcohols, when applied often enough in a ‘clean mouth’ at a tooth surface, can lead to a caries lesion development over time.
It would be interesting to examine the populations in Peshawar. We would question the level of oral hygiene, but your observation is correct, of course. If the caries load is high (and it is in some populations eating excessive amounts of sugar-containing snacks and food – also in Saudi Arabia and many other Muslim cultures) fluoride alone cannot dampen the caries attack. Here we must try to influence sugar habits.
Once more thank you for your engagement in an important issue.
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