| Objective: Root surface caries are common in the elderly. The prevention of root surface caries is one of the important aspects of geriatrics. Demineralization of mineral and decomposition of organics subsurface cementum was caused under the effect of the bacterial plaque, which lead to root caries after the destroy of construction integrality of cementum. There are different ideas regarding the pathogen of root surface caries. The finding of bionomics of main pathogen have suggested that the main pathogen is streptococcus. At present the employing of antibiotics and fluorid to prevent caries still has much limitations. It need to search some new methods. Propolis is one of high-performance natural Chinese crude drug, which has much ingredient. Among the total, flavonoidsis the highest, which is the essence of propolis. It has been reported to have a variety of antioxygen activity, anti-inflammatory, anti-virus, immunological regulation; and anti-carcinogenic effects. At present the therapy of diseases of oral mucosa periodontal disease by propolis has much effect. It has no adverse reaction in devitalizing dental nucleus and sterilizing canalis radicis dentis to oral cavity soft- sclerous tissues, wich is used for departmrnt of dermatology, department of gynecology, and internal medicine as well. Therefore, this study was designed to investigate the effects and possible mechanisms of propolis on prevention of dental root caries, and to seek rationalefor better clinical application.Methods: 1 The preparation of bacterium suspension: In 37℃condition, resuscitating S.mutans for 48 hours, then inoculating on blood culture medium, cultivating for 24 hours in attemperator under 37℃constant temperature micro-needed oxygen. Choose a little bacteric gobbet, serial subcultivating for three times, observing under light microscope to confirm S.mutans and groow well. After subcultivating it to cultivation fluid for 24 hours in micro-need oxygen 37℃condition, with stroke-physiological saline solution adjust it to bacterium suspension OD=1.0 under UV spectrophotometer.2 The preparation of propolis 's solution: to dilute Beijing propolis extracts duplicately according to 1:2 gradient. 7.5g/L,3.75g/L,1.875g/L ethamolic extract of propoli was used.3 Experimentation of extraorgan bacteriostasis: agar diffusion method is applied to measure bacteriostasis cingula surrounding every agent with caliper rule。4 Forty Pathologic migration-three degree of molars in patients with severe periodontitis are selected for this studay, which with the standard that: caries-free and the surface of cementum is lubricous under stereomicroscope. Calculus dentalis and pericementum on the root surface are absolutely eliminate and all the specimen are washed in ultrasonic cleaner with 0.1mol/PBS balanced solution, then disinfected in 10% formaldehyde solution and stored in 4℃refrigeratory for use . All the teeth are splited from central fossa along bucco-glossia with carborundum. Medial sueface(distal sueface)of the specimen are used for sample plot. Each specimen is coated with acid-resistant nail varnish, leaving a rectangular window of 5mm×5mm on adaxial surface near CEJ area . Then they are randomly divided into five groups: propolis alcoholic solution group(disposed respectively with 7.5g/L, 3.75g/L, 1.875g/L propolis alcoholic solution), 20g/L NaF treated group, deionized water treated group. Each specimen is dipped in agent homologously 37℃constant temperature for 5min, after cooling for 30min in air all specimen are put artificial saliva 37℃thermostatic waterbath. All this is repeated for three times one day. Choosing five spemen from every agent in five day, ten day, fifteen day respectively, after drying under room temperature, the spemen are suspled in bacterium suspension above-mentioned, cultivating for 48 hours in 37℃constant temperature micro-needed oxygen, drying for SME and light microscope observing of Pathologic morphology of root surface. The dis-nine liquid is measured for the Ca2+ dissolution capacity; with atomic absorption spectrophotometer.5 Morphology analysis by scanning electron microscope: to cut the cementum specimen after demineralization with silicon carbide. One half is put into 2% glutaral for fixing 24 hours, then in osmic acid for 2 hours. After poaching with PBS balanced solution, the specimen are dehydrated with 50% to absolute alcohol gradely, then to plate with gold. The change of morphology was observed by scanning electron microscope in different time and photographed.6 Using polarimicroscope observe the change of morpholo- gy: put the left specimen into paraform solution for fixing. Then use 10% EDTA to routine decalcification. After connective histological section along long axis and HE staining, observe the change of morphology and photographed.Results: 1 To contrast with alcohol, concentration of propolis's solution was decreased (concentration index were 7.5g/L, 3.75g/L, respectively) and diameter of bacteriostasis cingula was shrinked (diameter index were 15.36±0.60mm,12.40±0.47mm, respectively). Comparision to the controls, The change in 1.875g/L group was more significant than in control group. 2 Each group of propolis's solution have the ability ofrestraining the demineralization of mineral, which can be measured with atomic absorption spectrotype. The cementum spemen were treated with propolis's solution at various concentrations for 5d, 10d, and 15d respectively, Comparision to the controls, the change in propolis 's solution group for 5d, 10d was more significant than in control group respectively. Concentration of propolis 's solution was increased, quantity of demineralization was decreased. To contrast with the controls and 20g/L NaF group, dissolution of Ca2+ was more significant. Time of propolis's solution was increased, quantity of demineralization was decreased.3 The biggest thickness of dental caries is 116.92±17.94um at the agent group minimum is 33.27±10.37um at the concentration of 7.5g/L. The change in agent group was more significant than in agent group. The thickness of propolis's solution at various concentrations were significantly lower than 20g/L NaF group's,except 1.875g/L group. The change of layer thickness in agent group was more significant than in control group.4 The analysis of Morphology by scanning electron microscope showed that there was a great quantity of bacterial calcium hydroxyapatite crystal groundmass, demineralization,a mass of matrix fibre ruptured in control group. The lesions of root surfaces with 20g/L NaF group is lighter than control group, with lesser matrix fiber ruptured. The propolis's solution group caries lesion is lightest hardly any matrix fibre ruptured.5 The observation of light microscope prevents that the caries lesion depth of control group is deepest, exterior layer is thinnest; the depth of NaF group is thinner than control group and exterior layer thicker; the depth of propolis's solution group caries lesion is thinnest exterior layer is deepest.Conclusion: The propolis's solution could restrain the growth of streptococcus mutans obviously, and the demineralization of cementum. Through the observation of micro and ultramicro, we found there was distinction between the spemen dealed with propolis's solution group and control group respectively, so that propolis can prevent root caries commendably.
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