Erosion and abrasion: wait 20-30 minutes before cleaning your teeth after eating acidic foods!

Professor Thomas Attin is Director of the Department of Restorative Dentistry, University of Göttingen

This article was previously published in a Wrigley publication in Germany.

Of late, dental surgeries have been seeing an increasing number of enamel and dentine defects that are not caries-related. Professor Thomas Attin, from the University of Göttingen, drew attention some time ago to the complex relationship between erosion due to abrasion and acid attacks. Now he and his team have been awarded the Wrigley Prevention Prize 2003 (2nd prize, Academic category) for their new findings on this subject.

Professor Attin, please give us a brief explanation of what your award-winning work focuses on and what insights you obtained.

Prof. Attin : The aim of our in-situ study was to determine the remineralisation time needed to restore the original resistance to toothbrush abrasion after an erosive attack on the dentine. The study showed that teeth are not remineralised until at least 30-60 minutes after eating acidic foods and should not be cleaned until after this period in order to protect exposed dentine surfaces.

How do you explain these results?

Prof. Attin : Our main explanation for these results is natural remineralisation by saliva in the mouth. Also, the collagen in the dentine seems to be exposed by the acid, creating a structure that stands proud of the dentine, in a similar way to the effect of acid on dentine adhesives. This layer acts as a buffer and increases resistance to brushing abrasion as well. It probably also supports remineralisation in some way. It's conceivable that this layer makes it easier for crystallisation to occur on the collagen.

Chewing gum has been proven to stimulate saliva production and thus has a preventative effect. Can this have a positive impact on remineralisation times?

Prof. Attin : Yes, there's no doubt that it can reduce the remineralisation time. You have a flow of fresh saliva into the mouth that provides a continuous supply of fresh calcium and phosphate ions to aid remineralisation (fig.1). In particular, patients with a low level of saliva in the mouth need to have the flow rate increased to protect against enamel and dentine defects.

Previous studies have shown that the resistance to abrasion of demineralised enamel is not restored until after about an hour. What is your recommendation on cleaning, based on these new results?

Prof. Attin : I wouldn't want to be that dogmatic. I see the time period as being the same as for enamel, i.e. between 30 minutes and an hour should elapse before the teeth are cleaned. After all, you will never just have enamel or just dentine exposed. It's always a combination. So what applies for enamel also applies for dentine.

Do these oral hygiene rules apply to all types of patient and is the old rule about remembering to clean your teeth after every meal no longer valid?

Prof. Attin : That's a very important question. The rule about waiting only applies to patients who often suffer from erosive damage, of course. That's not the case with the majority of the population. Interestingly, there are very few studies about the best time to clean your teeth, but many different opinions. One intriguing view is that if plaque has been removed very thoroughly before eating, an acid attack afterwards due to bacteria is no longer a danger - it's a well known fact that it takes up to 24 hours or even longer for plaque with active caries to build up.

I would therefore recommend patients who suffer from erosion to clean their teeth before a meal. It's something that I've been doing myself for more than 10 years. After the meal, additional steps to stimulate saliva production, like chewing sugarfree gum, can help prevent acid attacks and speed up remineralisation.

References:

1. Zero DT et al: (1999) Data on file

2. Zero DT: J Dent Res 71 (1992).