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Dibdin GH. Models of Diffusion/Reaction in Dental Plaque. MICROBIAL ECOLOGY IN HEALTH AND DISEASE 2009. [DOI: 10.3109/08910609509140113] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- G. H. Dibdin
- MRC Dental Group, The Dental School, Lower Maudlin St, Bristol, BS1 2LY, UK
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Dibdin GH. Computer Modelling of Dental Plaque in Relation to Dental Caries. MICROBIAL ECOLOGY IN HEALTH AND DISEASE 2009. [DOI: 10.3109/08910609009140249] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- G. H. Dibdin
- Medical Research Council Dental Group, The Dental School, Bristol University, Lower Maudlin St, Bristol, BS1 2LY, UK
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Suci PA, Geesey GG, Tyler BJ. Integration of Raman microscopy, differential interference contrast microscopy, and attenuated total reflection Fourier transform infrared spectroscopy to investigate chlorhexidine spatial and temporal distribution in Candida albicans biofilms. J Microbiol Methods 2001; 46:193-208. [PMID: 11438184 DOI: 10.1016/s0167-7012(01)00268-8] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Two spectroscopic techniques, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and Raman microscopy (RM), were used to characterize transport of chlorhexidine digluconate (CHG) in Candida albicans (CA) biofilms. Different (volumetric) regions of the biofilm are sampled by these two vibrational spectroscopies making them complementary techniques. Simple mathematical models were developed to analyze ATR-FTIR and RM data to obtain an effective diffusion coefficient describing transport through CA biofilms. CA biofilms were composed primarily of yeast and hyphal forms, with some pseudohyphae. Upper regions of biofilms that had become confluent, (i.e., biofilms that completely covered the germanium (Ge) substratum) were composed primarily of a tangled mass of hyphae with openings between germtubes about 10 to 50 microm across. Quantitative analysis of ATR-FTIR kinetic data curves indicated that the effective diffusion coefficient for transport of CHG through confluent biofilms about 200-microm thick was reduced 0.1 to 0.3 times compared to the diffusion coefficient for CHG in water. Effective diffusion coefficients obtained from analysis of RM data were consistently higher than those indicated by ATR-FTIR data suggesting that transport is more hindered in regions near the base of the biofilm than in the outer layers. Analysis of both ATR-FTIR and RM data obtained from thicker films indicated that adsorption of CHG to biofilm components was responsible for a substantial portion of the transport limitation imposed by the biofilm. Comparison of ATR-FTIR and RM data for both types of biofilms indicated that sites of CHG adsorption were more concentrated in the interfacial region than in the bulk biofilm. Comparison of results for ATR-FTIR and RM measurements suggests that these relatively thick CA biofilms can be modeled, for purposes of predicting transport, approximately as a homogeneous thin planar sheet. Thus, these biofilms offer a relatively tractable model system for initial investigations of the relation between antimicrobial transport and kinetics of antimicrobial action.
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Affiliation(s)
- P A Suci
- Center for Biofilm Engineering and Microbiology Department, Montana State University, Bozeman, MT 59717-3980, USA
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Rose RK. Effects of an anticariogenic casein phosphopeptide on calcium diffusion in streptococcal model dental plaques. Arch Oral Biol 2000; 45:569-75. [PMID: 10785520 DOI: 10.1016/s0003-9969(00)00017-0] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Casein phosphopeptides (CPP) stabilize amorphous calcium phosphate (ACP) and may be used to localize ACP in dental plaque, maintaining a state of supersaturation with respect to tooth enamel, reducing demineralization and enhancing remineralization. The aim here was to investigate these effects by measuring the effect of CPP-ACP on calcium diffusion in plaque. Using Dibdin's effusion system, calcium diffusion was measured in streptococcal model plaques. This demonstrated that by providing a large number of possible binding sites for calcium, 0.1% CPP-ACP reduces the calcium diffusion coefficient by about 65% at pH 7 and 35% at pH 5. Hence, CPP-ACP binds well to plaque, providing a large calcium reservoir within the plaque and slowing diffusion of free calcium. This is likely to restrict mineral loss during a cariogenic episode and provide a potential source of calcium for subsequent remineralization. Overall, once in place, CPP-ACP will restrict the caries process.
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Affiliation(s)
- R K Rose
- Division of Restorative Dentistry, The Dental School, Bristol, UK.
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Affiliation(s)
- G Dibdin
- Department of Oral and Dental Science, University of Bristol, United Kingdom
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Stewart PS. A review of experimental measurements of effective diffusive permeabilities and effective diffusion coefficients in biofilms. Biotechnol Bioeng 1998; 59:261-72. [PMID: 10099336 DOI: 10.1002/(sici)1097-0290(19980805)59:3<261::aid-bit1>3.0.co;2-9] [Citation(s) in RCA: 192] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Experimental measurements of effective diffusive permeabilities and effective diffusion coefficients in biofilms are reviewed. Effective diffusive permeabilities, the parameter appropriate to the analysis of reaction-diffusion interactions, depend on solute type and biofilm density. Three categories of solute physical chemistry with distinct diffusive properties were distinguished by the present analysis. In order of descending mean relative effective diffusive permeability (De/Daq) these were inorganic anions or cations (0.56), nonpolar solutes with molecular weights of 44 or less (0.43), and organic solutes of molecular weight greater than 44 (0.29). Effective diffusive permeabilities decrease sharply with increasing biomass volume fraction suggesting a serial resistance model of diffusion in biofilms as proposed by Hinson and Kocher (1996). A conceptual model of biofilm structure is proposed in which each cell is surrounded by a restricted permeability envelope. Effective diffusion coefficients, which are appropriate to the analysis of transient penetration of nonreactive solutes, are generally similar to effective diffusive permeabilities in biofilms of similar composition. In three studies that examine diffusion of very large molecular weight solutes (>5000) in biofilms, the average ratio of the relative effective diffusion coefficient of the large solute to the relative effective diffusion coefficient of either sucrose or fluorescein was 0.64, 0.61, and 0.36. It is proposed that large solutes are effectively excluded from microbial cells, that small solutes partition into and diffuse within cells, and that ionic solutes are excluded from cells but exhibit increased diffusive permeability (but decreased effective diffusion coefficients) due to sorption to the biofilm matrix.
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Affiliation(s)
- P S Stewart
- Center for Biofilm Engineering and Department of Chemical Engineering, Montana State University, Bozeman, Montana 59717, USA.
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Rose RK, Turner SJ, Dibdin GH. Effect of pH and calcium concentration on calcium diffusion in streptococcal model-plaque biofilms. Arch Oral Biol 1997; 42:795-800. [PMID: 9460532 DOI: 10.1016/s0003-9969(97)00082-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Demineralization during a cariogenic episode is affected by storage and transport in dental plaque of ions released from enamel, and by the effect on both of plaque fluid pH and ion concentrations. To investigate this, 45Ca effusion from a condensed film of streptococci was measured at pH 7, 6 and 5, and 0-20 mmol/l calcium. Cells were loaded into effusion chambers and the appearance of 45Ca and [3H]-inulin in carrier-containing but initially tracer-free buffer was measured. Ratios of 45Ca and [3H]-inulin activity in the initial suspending solution and at equilibrium in the clearance solution, permitted calculation of extracellular volume and bound calcium. The rate of Ca appearance was proportional to the retarded diffusion coefficient (rDe), which was related to the effective diffusion coefficient (De) by: rDe = De/(1 + R) in which R is the ratio of bound to free Ca2+. The rate of Ca2+ effusion increased with calcium concentration, converging on a value of 2.8 x 10(-10) m2/sec. At low pH it reached convergence at a lower [Ca]. This demonstrates that calcium effusion is dependent on binding, so a high proportion of binding sites in plaque will reduce mineral loss in vivo. Loss of binding sites at low pH will increase mineral loss.
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Affiliation(s)
- R K Rose
- MRC Dental Group, Dental School, Bristol, U.K
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Abstract
A set of mathematical equations constitutes a mathematical model if it aims to represent a real system and is based on some theory of that system's operation. On this definition, mathematical models, some very simple, are everywhere in science. A complex system like a biofilm requires modeling by numerical methods and, because of inevitable uncertainties in its theoretical basis, may not be able to make precise predictions. Nevertheless, such models almost always give new insight into the mechanisms involved, and stimulate further investigation. The way in which diffusion coefficients are measured for use in a model, particularly whether they include effects of reversible reaction, is a key element in the modeling. Reasons are given for separating diffusion from reversible reaction effects and dealing with them in a separate subroutine of the model.
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Affiliation(s)
- G H Dibdin
- MRC Dental Group, University of Bristol Dental Hospital, United Kingdom
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Abstract
The suggestion that loss of labile components from dental plaque into contacting aqueous buffer during some diffusion measurements might change the plaque's diffusion behaviour, and therefore invalidate the results, has been tested using tracer clearance. (a) Diffusion of [14C]-acetate and 3H2O was determined before and after a 3-4 h equilibration with neutral buffer. No differences or trends were found. (b) Mean normalized [14C]-acetate clearance curves from live plaque for measurements before and after such equilibration were identical in shape and showed no change in diffusion coefficient during clearance, as evidenced by their fits to the theoretical clearance curve. No significant difference was found between coefficients for the two periods (paired sample test). In addition, [14C]-lactate and 3H2O were found to permeate plaque in a miniature diaphragm diffusion cell at rates independent of whether the plaque was bathed either in saliva supernatant, plaque fluid or neutral buffer. This lent some further support to the main findings. It is concluded that diffusion through dental plaque is little affected by the bathing fluid.
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Affiliation(s)
- G H Dibdin
- MRC Dental Group, Dental School, Bristol, U.K
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Libicki SB, Salmon PM, Robertson CR. The effective diffusive permeability of a nonreacting solute in microbial cell aggregates. Biotechnol Bioeng 1988; 32:68-85. [DOI: 10.1002/bit.260320111] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Dibdin GH. Problems with fitting data to a saturating exponential: a simple solution which takes account of transformation and measurement errors. Med Biol Eng Comput 1988; 26:217-21. [PMID: 3226179 DOI: 10.1007/bf02442268] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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Main C, Geddes DA, McNee SG, Collins WJ, Smith DC, Weetman DA. Instrumentation for measurement of dental plaque thickness in situ. JOURNAL OF BIOMEDICAL ENGINEERING 1984; 6:151-4. [PMID: 6708489 DOI: 10.1016/0141-5425(84)90059-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
A commercial digital micrometer has been modified mechanically and electronically to allow the measurement, in situ, of the thickness of dental plaque. The device detects initial contact between a moving probe and the plaque, and measures subsequent probe displacement through to the tooth surface. Instrument accuracy is +/- 5 micron over a displacement range of 0-5 mm, with 1 micron resolution. In practice, after a short 'learning' phase, reliable clinical results can be obtained.
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Abstract
Using a clearance technique, diffusion coefficients, D, were measured in plaque samples in which metabolic activity was eliminated by fixation with glutaraldehyde. Diffusion coefficients for sucrose, sodium acetate and sodium lactate at 37 degrees C were 3.0, 5.0 and 4.8 x 10(-6) cm2 s-1, respectively. Diffusion rate in plaque was between 2- and 5-fold slower than in water with uncharged species retarded less than charged species. However, diffusion in thin layers of plaque (100 microns) was rapid with clearance-halving times. T1/2, of about 6 s for acetate and lactate and 9 s for sucrose. Acetic and lactic acids diffuse faster than sucrose in plaque. Thus, the prolonged lowering of plaque pH following exposure to dietary carbohydrate is due to continued acid production in the plaque rather than to a restriction of diffusion of acid.
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McNee SG, Geddes DA, Weetman DA, Sweeney D, Beeley JA. Effect of extracellular polysaccharides on diffusion of NaF and [14C]-sucrose in human dental plaque and in sediments of the bacterium Streptococcus sanguis 804 (NCTC 10904). Arch Oral Biol 1982; 27:981-6. [PMID: 6961914 DOI: 10.1016/0003-9969(82)90107-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
It has been postulated that extracellular polysaccharides form a barrier to diffusion in dental plaque. Diffusion coefficients, D, were measured for NaF and [14C]-sucrose in glucan-free and glucan-containing sediments of Strep. sanguis 804 at 37 degrees C. There was a tendency for NaF and [14C]-sucrose to diffuse faster as the carbohydrate concentration in the sediments increased. NaF diffused only 38 per cent more slowly in cell-free glucan sediment than in water, suggesting that glucan per se does not form a barrier to diffusion. The diffusion coefficient for NaF was positively correlated with carbohydrate concentration in individual plaque samples from 15 subjects and incubation of 3 plaque samples with sucrose resulted in both an increase in carbohydrate concentration in the plaque and an increase in D for NaF. Thus the presence of extracellular polysaccharides in plaque leads to slightly faster rates of diffusion. Nevertheless, the total time for diffusion through plaque may be increased if the presence of extracellular polysaccharides results in thicker layers of plaque.
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McNee SG, Geddes DA, Main C, Gillespie FC. Measurements of the diffusion coefficient of NaF in human dental plaque in vitro. Arch Oral Biol 1980; 25:819-23. [PMID: 6944004 DOI: 10.1016/0003-9969(80)90140-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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