Dental Hygiene: No Closing Credits For Biofilm

20. December 2012
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Dentists have developed a new understanding of caries prevention. The magic word is biofilm management. The toothbrush has not yet had its day, but researchers are working on new ideas. Their strategies: antibodies or transgenic bacteria.

With poor dental cleaning together with epithelial remnants there develops the pellicle. Finally, bacteria such as Streptococcus mutans settle in, where they adhere within the biofilm, well protected. These are small worlds of their own: the matrix contains carbohydrates, especially dextrans, and proteins as a food reserve; in addition scientists have evidence of small signaling molecules. By way of quorum sensing an optimal population density of bacteria results – with high metabolic rates. Products such as organic carboxylic acids have caries as a consequence.

Researchers with the brush

From the cradle to the grave patients hear for this reason from their dentist always the same old line: brush the teeth. Now, scientists have picked up the theme. In order to investigate the question of what modern dental care really can accomplish, Dutch colleagues combed through 2,119 articles and finally identified 59 papers of high quality. One conclusion was that patients who brushed their teeth regularly were able to reduce plaque layering by 42%. Proven to be comparatively effective were angled brush hairs, the effect was particularly bad with flattened bristles. On average, after one minute brushing time plaques decreased by 27% and after two minutes by 41%. Since few publications dealt with cleaning by following instructions, no statistically significant statements were possible on this. Some individual studies reveal, however, quite interesting aspects.

Patients at the school desk

Dentists and biologists from Cologne took on this difficult issue together and compared different methods of patient education in adolescents. They ordered 157 students randomly into three different groups:

  • Training by a dentist
  • Instruction by peers
  • A team event with dentists, teachers and patients as equals

As part of follow-ups, it was examined whether subjects switched from childhood dental care to normal technique used by adults. After one hour of instruction, 90% of all participants reproduced the desired methodology. One week later, the adherence in group one was only 28.5%, in group two it was 39% and at least 95% for group three. Even at points in time three months and nine months later, the third group was still significantly showing better results: a clear endorsement of the so-called “adherence triangle concept”.

How to brush your teeth

So much for children – at the Institute of Medical Psychology at the University of Giessen adults were the focus. The question posed was how easily students learn common cleaning techniques. A computer presentation, which took 30 to 45 minutes, developed together with dentists served as a manual. Subjects who were to learn the simpler “Fones technique” cut it better than their counterparts in the “bass” group. Both groups, however, were far from optimal. For the dental practice this means that not every patient with poor dental hygiene is necessarily from the one and the same mould, it’s often a case of getting technique wrong. Now teaching materials should be developed for home use – such instructions are not possible in such detail during regular check-ups. Also patients often ask which toothbrush is to be recommended.

Brush 2.0

A few years ago the Cochrane Collaboration only made a comparison of manual toothbrushes with electrical counterparts. At the time, the bottom line was that electric toothbrushes may already over a short period more effectively remove plaque and reduce gingivitis than the manual version. Longer observation periods of three months or more improved gingivitis even more clearly. Now, British researchers at the Frenchay Hospital have devoted themselves to the question of which electric toothbrush brings the best benefits. They took a total of 15 trials involving 1,015 subjects in their systematic review, but found no significant differences.

Effective and harmless

A Cochrane meta-analysis of 17 studies and 1,369 participants provided evidence that devices with oscillating-rotating brushes clean better than variants that rely only on lateral movements. The authors, however, speak of an “unclear or high risk of bias”. Therefore, no definitive conclusion could be drawn as to their superiority. Dentists at the University of Sheffield studied the safety of spinning brush heads. Their conclusion from 35 studies: electric toothbrushes would affect neither hard nor soft tissue.

Battle against the germ

Biofilm management does not, however, stop at brushing your teeth. First and foremost points of tooth-crowding or fissures are difficult to reach with the brush, true biotopes develop here. Meanwhile, dentists have introduced additional strategies: antibacterial agents such as Chlorhexidine or Triclosan with regular use reduce caries germs. Chlorhexidine is present in medicinal preparations as a cation and preferentially binds to negatively charged bacterial components in biofilms. Tin fluorides also have antibacterial effects, but the effect is markedly more weakly pronounced. And sweeteners or sugar substitutes not only help patients who reach for their brush irregularly. Xylitol has weak bacteriostatic properties. Subjects who consumed gum consistently for 30 days or more had in their saliva significantly less Streptococcus mutans cells than before.

News from genetic technology

It is precisely on this germ that researchers are working in the lab. Antibodies against Streptococcus mutans packaged in a lacquer could prevent the colonization of surfaces. Glycosyltransferases or adhesins serve as the Achilles’ heel in the picture, since they bind the bacteria and pellicle. Researchers at Oragenics as part of their “SMaRTReplacementTherapy”, in contrast, are making genetically altered, “attenuated” Streptococcus mutans strains. These express instead of the enzyme lactate dehydrogenase only alcohol dehydrogenase – and thus the more aggressive synthesis of carboxylic acids becomes a thing of the past.

An additional gene leads to the formation of antibiotic mutacin. Transgenic bacteria in the mouth should displace the actual caries creaters – with years of protection built in. This concept is promising, especially for use during the first months of life, it is said at Oragenics. The “SMaRT” Project is now in a second clinical phase I trial. Dental preventive measures are, despite that, still not going to become obsolete.

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Dentistry, Medicine

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