| Background:Caries is one of the most common and frequent oral diseases. The prevention of caries has always been the focus of dental surgeons. Research has already proved the anti-caries effects of fluoride. With the increasing use of fluoride-containing preparations, the problems associated with excess fluorides are coming to people's attention; such as fluorosis, dental fluorosis and fluoride-resistant strains causing caries. The initial factor in the formation of caries is the plaque bio film, which, when accompanied by floating bacteria, become more virulent, drug resistant and anti-immune. As a result, bacteria associated with the plaque bio film are more likely to lead to caries than the same kind of bacteria in the floating state. Therefore, the search for a safe and effective anti-caries preparation is one of the most sought after'hot spots'of caries prevention researches. Propolis is well known as"the most perfect and natural board-spectrum antibiotic", with advantages of it being safe, effective and non-drug resistant with no side effects. Both national and international researches have indicated that propolis has an inhibitory action towards the formation of caries bacteria and single-bacterium bio film. This research focuses on the ability of domestic water-soluble propolis (WSP) against the formation of plaque bio films and acid production, and explores its future in caries prevention.AIM:Based on both national and international researches, the author explores the ability of domestic water-soluble propolis (WSP) against the formation of plaque biofilms and acid production; providing theoretical basis for long-term usage of propolis as a natural anti-caries preparation in the future.Materials and Methods:1. The in vitro inhibiting ability of propolis against L.acidophilus, A.viscosus, S.sobrinus, S.mutans. were tested. In this test, the method of liquid dilution was used to determine the MIC of these four kinds of bacteriae. 24 test tubes were divided into two groups. In the first group, 100g/L propolis of 1.0ml was put into the first tube and BHI was used for double dilution. Then this was distributed equally among the other 11 tubes. In the second group, 10g/L NaF of 1.0ml was put into the first tube. BHI was used for double dilution, as in the first group. Another BHI tube without any medical fluid was used as the comparison tube. Then A.viscosus bacterial suspension of 1.0ml was added into each tube. The turbidity of the culture medium was observed after anaerobic cultivation at 37℃. The same method was used to determine the ability of propolis against the other three bacterial strains.2. To test the effect of propolis on the plaque bio film structure of common caries bacteriae, four kinds of bacteriae - S.mutans, S.sobrinus, L.acidophilus, A.viscosus, were diluted in aseptic normal saline and were fully mixed. A spectrophotometer was used to adjust the bacterial concentration to OD540nm=1. This fluid was used as a mixed bacterium fluid.(1)24 sterilized cover glasses of 15mm diameter each were placed on a culture medium containing 24 cell holes. Mixed bacterium fluid of 200μl and BHI culture medium of 1800μl were added into each hole, then cultivated anaerobically at 37℃for 48h. The holes were replaced with fresh medium of 1500μl every 12hrs to form a plaque bio film.(2)a second batch of 24 bacteria bio film cover glasses were prepared as in step (1), and PBS was used to wash away floating bacteria from the surface. Then the 48 cover glasses were put into fresh culture medium; one glass in each hole. Meanwhile, they were divided evenly into 6 groups with 8 holes in each group; therefore, there were four test groups, a positive comparison group and a negative comparison group. For the four test groups, 2000μl of BHI culture medium was added along with 6.25g/L, 3.13g/L, 1.56g/L and 0.78g/L of propolis respectively. For the positive comparison group, 2000μl of BHI culture medium was added along with 0.31g/L of NaF. For the negative comparison group, 2000μl of BHI culture medium was added without any medicine. The six groups were cultivated anaerobically at 37℃for 24hrs. The groups were replaced with fresh medium of 1500μl every 12hrs. After 24hrs, the cover glasses were taken out and were viewed under scanning electron microscope.3. To research the effect of propolis on the plaque biofilm structure of common caries bacteriae, the cover glasses were taken out as in step (2), the culture medium was extracted from each hole (four test groups, and the positive and negative comparison groups) and placed into 48 centrifugation tubes. After centrifugation, the supernatant was extracted and the pH value of the fluid on the culture medium was determined.Results:1. The MIC of L.acidophilus, A.viscosus, S.sobrinus, S.mutans are 0.78g/L, 0.78g/L, 0.2g/L and 0.39g/L respectively; and the MIC of NaF to L.acidophilus, A.viscosus, S.sobrinus, S.mutans are, 0.16g/L, 0.31g/L, 0.16g/L and 0.16g/L respectively.2. The structure of the bacterial bio film became loose and the base material excretion diminished with the increase of propolis concentration.3. The final pH value of fluid in the culture medium rose with the increase of propolis concentration (P<0.01), and was higher when compared to the negative group. The difference was statistically significant (P<0.05). The pH values of the Propolis groups of 6.25g/L and 3.13g/L were higher than the positive comparison group. The difference was statistically significant (P<0.05). When the concentration of propolis was higher than 3.13g/L, the final pH value of the fluid in the culture medium reached a critical level of pH 5.5.Conclusion:1. A propolis concentration of larger than 0.78g/L obtains inhibiting ability towards L.acidophilus, A.viscosus, S.sobrinus, S.mutans; meanwhile NaF concentration of larger than 0.31g/L obtains inhibiting ability towards these four strains of bacteriae.2. The domestic water-soluble propolis (WSP) has a negative effect on the formation of plaque biofilms and caries bacteriae; and such an effect grows with the concentration of propolis.3. The domestic water-soluble propolis (WSP) has an inhibiting ability on the acid production of plaque biofilms; and the ability grows with the concentration of propolis. When the concentration of propolis was higher than 3.125g/L, the final pH value reached a critical level of pH 5.5. Therefore, there was more inhibiting ability towards acid production4. The ability of domestic water-soluble propolis (WSP) to prevent caries possesses deep research value. |
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