VoedingsMagazine - nummer 4, december 2011, 24e jaargang
NutritionMagazine, No.4, 2011, Vol.24
Milk and yoghurt products have a protective effect
Acid erosion is a gradually expanding problem
‘We did not expect that milk and yoghurt products protect against acid erosion, but it proved to be the case indeed,' the dentist Dr Halima El Aidi said on the occasion of results of her doctoral research. She noted that it would be nice if these products would be protective indeed. ‘However, I'm still cautious in my statements since broader studies are needed for general advice useful for daily practice.'
Acid erosion (dental erosion, erosive tooth wear) is a new problem for the teeth of children and adolescents. Caries (tooth decay) used to be the main problem before. ‘There are indications that the problem of tooth wear is gradually expanding,' Dr Halima El Aidi said. Dr El Aidi is a dentist working in a group practice in Rosmalen. She obtained her doctoral degree in September 2011 at Radboud University Nijmegen on the basis of research of acid erosion in children aged 10—12. She followed for her studies the children for three years (see frame text). ‘It was nice to follow them in that period and to observe the changes. Initially the contacts were laid via the parents, but the children managed to give answers by themselves after some years. One sees that children become somewhat detached from their parents by then.' Across human life teeth are exposed to numerous physical and chemical influences. In her studies Halima El Aidi attempted to unravel pieces of the multifactorial aetiology of acid erosion. It is important, she told: ‘To turn the tide, it is necessary to recognize signals and to take measures as early as possible.' When acid erosion occurs at young age, it may result in pathological tissue loss over the years. Moreover, tooth wear makes teeth and molars sensitive. Up to date, such damage is hard to repair.
Considerable deterioration During her clinical investigations Halima El Aidi made an inventory of biological factors (e.g. saliva production, saliva acidity, bite force and tooth contact), behavioural factors (way of drinking such as fizz, direct swallowing or use of a straw), brushing pattern and nutritional factors (e.g. sour fruit, sour vegetables, salad dressings, alcoholic, non-alcoholic and carbonated beverages, tea and fruit juices). Dietary information was gathered every six months through a food frequency questionnaire compiled in collaboration with Wageningen University. Halima El Aidi: ‘We did not make a complete food package inventory but concentrated on products that might be related to acid erosion.' With the food frequency questionnaire specifically developed for her studies she inquired about the use of many products including beverages (e.g. fruit lemonades, ice tea, soft drinks and sports drinks), fruit juices, fruit and yoghurt products, sour vegetables, sweet sandwich spreads, ice lollies, chewing gum and red and white/yellow sauces. Many children (32.2%) already showed evidence of acid erosion at baseline; that proportion increased to 42.8% in one year and a half. Halima El Aidi: ‘Thus, wear had deteriorated in relatively short time.' Data analysed at the end of the three-year study showed that progression of acid erosion was 36.8% in 11-year olds and 29.0% in 12-year olds. The wear was seen in particular on the first, large molars in the lower jaw and the backside of the upper permanent teeth. More boys than girls, and more children from groups with a lower than from those with a higher socioeconomic status (SES), suffered from acid erosion. In children and adolescents the composition of their diet is considered to be the predominant extrinsic risk factor for acid erosion. Data collected by Halima El Aidi revealed that overall consumption of beverages declined significantly to 0.15 glass per day at increasing age. However, at higher age more carbonated beverages were drunk by boys and by children from families with a higher SES. Consumption levels were lower for fruit and dairy products. Halima El Aidi: ‘In a relatively short period of time, the use of beverages, fruit and dairy products changed in an unfavourable direction from a public health perspective. That development calls for tailored information programmes.'
The most surprising outcome The analysis of biological, behavioural and nutritional factors revealed that the aetiology of acid erosion is complex in this group of Dutch adolescents. There is more than the adverse effect of sour (soft) drinks alone. ‘Until recently, it was assumed that it is only acid that plays a role in the development of acid erosion. That appears not to be the case. In daily practice, we see various forms of tooth wear.' Not only acidity factors but also mechanical factors like gnashing (bruxism) and clenching (protracted clamping tightly the top and bottom teeth together) may play a role in its development. Many dentists attempt to find out the cause of tooth wear by looking at the pattern and form of wear. ‘My study results show, however, that there is a weak correlation between the outer appearance and the aetiology of tooth wear. This calls in daily practice, therefore, for an elaborate anamnesis which should make clear what makes the wear happen and what advice could improve the situation.' When asked for the most surprising outcome of her studies she answered: ‘We did not expect that milk and yoghurt products protect against acid erosion, but it proved to be the case indeed.' One might expect that children on a diet rich in milk and yoghurt products use less of soft drinks. ‘I corrected for soft drink use. Soft drink use being equal, the protective effect of dairy products remains. The effect might be attributable to the high calcium and phosphate levels of these food products. After consumption of sour products calcium and phosphate might exert a neutralizing effect. However, for such an effect the dairy products should be ingested immediately after consumption of a sour product, which is not a very likely situation. It has been speculated that milk proteins are responsible for protection against acid erosion. The effect of milk proteins might be that the protective layer formed on the teeth by saliva is modified such that it is even more protective.' It would be nice if that is the case indeed, Halima El Aidi noted. ‘Apparently, these products provide an environment that suffices to protect the teeth the whole day independent of the sour products consumed. However, I'm still cautious in my statements since broader studies are needed for general advice useful for daily practice.' In the past decade dentists have been paying more attention to the importance of prevention of acid erosion. ‘That is essential since my study results show that mild acid erosion in young children progresses considerably in three years' time. At the age of 23, the erosion may have become a real problem. Therefore, we must attempt to slow down the trend through prevention.' Halima El Aidi recommends dentists to be attentive to signs of wear.
H. El Aidi (2011) Development and aetiology of erosive tooth wear in adolescents. PhD thesis, Radboud University Nijmegen.
Study design Dr Halima El Aidi designed a longitudinal clinical study at Radboud University Nijmegen (department of Preventive and Curative Dentistry) with 656 children 10—12 years old at study entry. The children were clients of a clinic for youth dental health care in Oss. The study sample, with an even distribution of boys and girls, accounted for ca. 35% of the age group in Oss. The participants' teeth were examined three times on erosive tooth wear: once at study entry, once after one year and a half and once after three years.
Research into chewing sensations Scientists of Wageningen University Food & Biobases Research and Top Institute Food and Nutrition at Wageningen are engaged in research into sensations experienced during eating and drinking. The first bite tells us whether we ingest solid or liquid food. After contact of the food with teeth, molars and tongue we also register aspects like fattiness, creaminess and melting behaviour. Some features do not become manifest until we swallow the bite or gulp and aromas enter our nose. The researchers looked in particular at semi-fluid foods like custard and yoghurt. In one of the studies trained tasters were asked to eat custard or yoghurt in various ways such as direct swallowing and spreading it as an 8 on the palate. The conclusion was that the more complex the movements of our mouth the more we register. However, the most effective way of experiencing food sensations is what we use to do: take a bite and swallow it. In the Restaurant of the Future in Wageningen researchers used sensors to measure what muscles are used during ingestion of diverse custard types. Sweet custard gives rise to other mouth movements than less sweet custard. The researchers published results of their study in Journal of Physiology and Behavior. See also: ‘Oral movements and the perception of semi-solid food'.