Effect of Sweeteners on Root Dentine Demineralization Using a Microcosm Biofilm Model / Efecto de los Edulcorantes en la Desmineralización de la Dentina Radicular Utilizando un Modelo de Biofilm Microcosmo

ABSTRACT: The aim of the present study was to evaluate the effect of commercial sweeteners on root dentin demineralization using a microcosm biofilm model. Bovine dentin specimens with pre-determined surface hardness were randomized into six groups according to the studied sweeteners: sucralose, stevia, saccharin, aspartame. Sucrose was used as a positive control and an untreated group as a negative control. The specimens were submitted to biofilm development from one saliva donor and the cariogenic challenge occurred on subsequent five days, twice a day. At the end, the percentage of surface hardness loss (%SHL) and biomass was determined and submitted to ANOVA followed by Tukey's test. Sucrose presented the highest rate of demineralization, however, all sweeteners tested lead to a statistically higher root demineralization compared to the negative control (p <0.05). Sucrose caused greater demineralization in root dentin, however, the sweeteners were also able to induce it under this biofilm model.

RESUMEN: El objetivo del presente estudio fue evaluar el efecto de los edulcorantes comerciales en la desmineralización de la dentina radicular utilizando un modelo de biofilm microcosmo. Se asignaron al azar muestras de dentina bovina con una dureza de la superficie predeterminada de acuerdo con los edulcorantes estudiados: sucralosa, estevia, sacarina, aspartame. La sacarosa se utilizó como control positivo y un grupo no tratado como control negativo. Las muestras se enviaron al desarrollo de biopelículas de un donante de saliva y el desafío cariogénico se produjo en los siguientes cinco días, dos veces al día. Al final, se determinó el porcentaje de pérdida de dureza de la superficie (% PDS) y biomasa y se aplicó un estudio estadístico de ANOVA seguido de la prueba de Tukey. La sacarosa presentó la mayor tasa de desmineralización; sin embargo, todos los endulzantes probados condujeron a una desmineralización de la raíz estadísticamente mayor en comparación con el control negativo (p<0,05). La sacarosa causó una mayor desmineralización en la dentina de raíz, sin embargo, los edulcorantes también fueron capaces de inducirla bajo este modelo de biofilm.

In situ Effect of Arginine-Containing Dentifrice on Plaque Composition and on Enamel Demineralization under Distinct Cariogenic Conditions.

There is limited evidence that arginine-containing fluoridated dentifrices (AFD) have a better anticaries effect than regular fluoridated dentifrices (FD), especially in subjects at a higher risk for caries development. This study aimed to assess the effect of AFD on enamel demineralization and on the microbial and biochemical compositions of biofilm formed under different frequencies of sucrose exposure. It consisted of an in situ split-mouth design, where 12 adult volunteers who used FD for at least 2 months prior to the beginning of this study wore acrylic palatal appliances containing 4 bovine enamel specimens (1 pair at each side of the appliance) during 2 phases of 14 days each. FD slurry (3×/day) and 20% sucrose solution (4× and 8×/day) were dripped on the specimens during the first experimental phase. The same volunteers then used AFD during a 2-month washout period, followed by a second experimental phase where the AFD slurry and sucrose solution were applied onto a new subset of specimens. The percentage of enamel surface hardness loss (%SHL), the lesion depth (LD), the integrated mineral loss (IML), microbial counts on biofilms, the biomass, and inorganic and insoluble extracellular polysaccharide (IEPS) biofilm concentrations were determined. Higher %SHL, biomass, and IEPS and lower fluoride values were found at sucrose 8×/day exposure. Lower IEPS were found in the presence of AFD compared to FD. Similar %SHL, LD, and IML values were found between FD and AFD, irrespectively of the cariogenic challenge. The results suggest that AFD have an anticaries effect similar to that of regular FD.

Sucrose induced dentin demineralization in a microcosm biofilm model / Desmineralización de la dentina inducida por sacarosa en un modelo de biofilm microcosmo

The aim of this in vitro study was to assess the root dentin demineralization caused by a microcosm biofilm model that has been exposed to sucrose in different ways. Materials and Methods: Saliva of two volunteers was inoculated into an artificial medium for biofilm growth and dentin blocks were immersed into these media. Dentin specimens were randomly exposed to one of the five experimental conditions: C (control group - no saliva inoculum or sucrose), 0S (saliva inoculum without sucrose, negative control), 3S (three daily one-minute immersions in 20 % sucrose), 6S (six daily one-minute immersions in 20 % sucrose), and CS (continuously immersed in 5 % sucrose). After five days, biofilm was collected to determine the concentration of intracellular and extracellular polysaccharides and the dentin surface hardness loss (SHL) was measured. The experiment was carried out in triplicate. Results: The dentin SHL was higher in groups that were exposed to sucrose (3S, 6S and CS) and there was a statistically significant difference between all groups (p<0.001). CS had higher concentrations of polysaccharides (p>0.001) and there was no statistically significant difference between the other groups (0S, 3S and 6S) (p>0.005). Conclusion: The microcosm biofilm model developed has the potential to produce root dentin demineralization at different exposures to sucrose.

El objetivo de esta investigación in vitro fue evaluar la desmineralización de la dentina radicular causada por un modelo de biofilm microcosmo que fue expuesto de diferentes maneras a la sacarosa. La saliva de dos voluntarios fue colocada en un medio artificial para crecimiento del biofilm y los bloques de dentina fueron sumergidos en estos medios. Al aza rlos bloques fueron expuestos a una de las cinco condiciones experimentales: C (grupo control ­ sin inoculación de saliva o sacarosa), 0S (inoculación de saliva sin sacarosa, control negativo), 3S (tres inmersiones diarias de un minuto en sacarosa a 20 %), 6S (seis inmersiones diarias de un minuto en sacarosa a 20 %), y CS (sumergidos continuamente en 5 % de sacarosa). Después de cinco días, el biofilm fue recogido para determinar la concentración de polisacáridos intracelulares y extracelulares y fue medida la pérdida de dureza superficial de la dentina (SHL). El experimento se repitió en tres ocasiones. La dentina SHL era mayor en los grupos que fueron expuestos a la sacarosa (3S, 6S E CS) y hubo diferencia estadísticamente significativa entre todos los grupos (P<0,001). CS presentó mayor concentración de polisacáridos (p<0,001) y no hubo diferencia estadísticamente significativa entre los demás grupos (0S, 3S E 6S) (p>0,005). El modelo del biofilm desarrollado tiene potencial para producir desmineralización de la dentina radicular en diferentes exposiciones a la sacarosa.

Effects of lactose-containing stevioside sweeteners on dental biofilm acidogenicity.

The aim of this study was to evaluate the effect of a commercial lactose-containing stevioside sweetener on biofilm acidogenicity in vivo. Nine volunteers refrained from brushing their teeth for 3 days in five phases. On the 4th day of each phase, the pH of the biofilm was measured by the "Strip method". Interproximal plaque pH was measured before and up to 60 minutes after a 10 mL mouthrinse for 1 minute with the test solutions: I - sweetener with 93% lactose and 7% stevioside; II - sweetener with 6.8% saccharin, 13.6% cyclamate, and 0.82% stevioside; III - 18% sucrose solution (positive control); IV - mineral water (negative control); and V- 93% lactose solution. The results revealed that the most pronounced pH fall was found with sucrose (positive control), followed by the 93% lactose solution, the sweetener with lactose + stevioside, the sweetener with saccharin + cyclamate + stevioside, and finally water (negative control). According to the area under the curve, the two sweeteners containing stevioside were significantly different, and the sweetener with lactose + stevioside was significantly different from water but not from sucrose. The critical pH for dentin demineralization (pH ≤ 6.5) was reached by all volunteers after rinsing with sucrose solution, lactose solution, and the stevioside + lactose sweetener. Analysis of the data suggests that lactose-containing stevioside sweeteners may be cariogenic, especially to dentin.

Cariogenicity of different commercially available bovine milk types in a biofilm caries model.

PURPOSE: This study's purpose was to assess the cariogenicity of commercial bovine milk types in an experimental biofilm/caries model. METHODS: Enamel and dentin slabs were used to grow biofilms of Streptococcus mutans UA159. Slabs/biofilms were exposed three times per day to commercial skim, semi-skim, whole, whole lactose-free, and whole with 10 percent sucrose-added bovine milk and to 10 percent sucrose and 0.9 percent sodium chloride as positive and negative caries-control, respectively. Biofilms were analyzed for bacterial counts, biomass, proteins, and polysaccharide production. Slab's demineralization was assessed by loss of surface microhardness and the biofilm acidogenicity by medium pH. RESULTS: Only whole and whole lactose-free milk kept pH above the demineralization threshold, inducing the lowest demineralization in both enamel and dentin (P<.05). Skim and semi-skim milk induced similar demineralization to the sucrose control, albeit slightly lower for semi-skim milk (P<.05). Whole and whole lactose-free milk produced lower biomass and less insoluble polysaccharides than the other treatments in enamel and dentin (P<.05). Adding 10 percent sucrose to whole milk turned it as cariogenic as 10 percent sucrose solution. CONCLUSION: Bovine whole milk seemed less cariogenic than sucrose and the other commercial milk types, but not anticariogenic. Fat content in milk seemed to reduce cariogenicity of the fluid.

Effect of cariogenic challenge on the stability of dentin bonds.

OBJECTIVE: The oral environment is subject to biofilm accumulation and cariogenic challenge, and few studies exist on the effect of these factors on the bond strength of adhesive systems. The aim of this study was to test if the exposure of adhesive interfaces to cariogenic challenge under biofilm accumulation could promote higher degradation than the exposure to biofilm accumulation alone. MATERIAL AND METHODS: Five molars were ground until exposure of medium dentin and then restored (Single Bond 2 and Z250 3M ESPE). The tooth/resin sets were cut to obtain beam-shaped specimens, which were distributed according to the aging conditions (n=20): water for 24 h (control); biofilm under cariogenic challenge for 3, 5 or 10 days; biofilm without cariogenic challenge for 10 days; and water for 3 months. Microcosm biofilms were formed from human saliva and grown in a saliva analogue medium, supplemented or not with sucrose to promote cariogenic challenge. Specimens were tested for microtensile bond strength, and failure modes were classified using light microscopy. Bond strength data were analyzed using ANOVA and failure modes were analyzed using ANOVA on ranks (α=0.05). RESULTS: No significant differences in bond strength were detected among the aging methods (P=0.248). The aging period was associated with an increase in the frequency of adhesive failures for the groups aged for 10 days or longer (P<0.001). CONCLUSION: Aging leads to a higher prevalence of interfacial adhesive failures, although this effect is not associated with cariogenic challenge or reduction in bond strengths.

Sucrose substitutes affect the cariogenic potential of Streptococcus mutans biofilms.

Streptococcus mutans is considered the primary etiologic agent of dental caries and contributes significantly to the virulence of dental plaque, especially in the presence of sucrose. To avoid the role of sucrose on the virulence factors of S. mutans, sugar substitutes are commonly consumed because they lead to lower or no production of acids and interfere with biofilm formation. This study aimed to investigate the contribution of sugar substitutes in the cariogenic potential of S. mutans biofilms. Thus, in the presence of sucrose, glucose, sucralose and sorbitol, the biofilm mass was quantified up to 96 h, the pH of the spent culture media was measured, the expression of biofilm-related genes was determined, and demineralization challenge experiments were conduct in enamel fragments. The presence of sugars or sugar substitutes profoundly affected the expression of spaP, gtfB, gtfC, gbpB, ftf, vicR and vicX in either biofilm or planktonic cells. The substitution of sucrose induced a down-regulation of most genes involved in sucrose-dependent colonization in biofilm cells. When the ratio between the expression of biofilm and planktonic cells was considered, most of those genes were down-regulated in biofilm cells in the presence of sugars and up-regulated in the presence of sugar substitutes. However, sucralose but not sorbitol fulfilled the purpose of reducing the cariogenic potential of the diet since it induced the biofilm formation with the lowest biomass, did not change the pH of the medium and led to the lowest lesion depth in the cariogenic challenge.

Effect of cariogenic challenge on the stability of dentin bonds

Objective: The oral environment is subject to biofilm accumulation and cariogenic challenge, and few studies exist on the effect of these factors on the bond strength of adhesive systems. The aim of this study was to test if the exposure of adhesive interfaces to cariogenic challenge under biofilm accumulation could promote higher degradation than the exposure to biofilm accumulation alone. Material And Methods: Five molars were ground until exposure of medium dentin and then restored (Single Bond 2 and Z250 3M ESPE). The tooth/resin sets were cut to obtain beam-shaped specimens, which were distributed according to the aging conditions (n=20): water for 24 h (control); biofilm under cariogenic challenge for 3, 5 or 10 days; biofilm without cariogenic challenge for 10 days; and water for 3 months. Microcosm biofilms were formed from human saliva and grown in a saliva analogue medium, supplemented or not with sucrose to promote cariogenic challenge. Specimens were tested for microtensile bond strength, and failure modes were classified using light microscopy. Bond strength data were analyzed using ANOVA and failure modes were analyzed using ANOVA on ranks (α=0.05). Results: No significant differences in bond strength were detected among the aging methods (P=0.248). The aging period was associated with an increase in the frequency of adhesive failures for the groups aged for 10 days or longer (P<0.001). Conclusion: Aging leads to a higher prevalence of interfacial adhesive failures, although this effect is not associated with cariogenic challenge or reduction in bond strengths. .

Different protocols to produce artificial dentine carious lesions in vitro and in situ: hardness and mineral content correlation.

This study compared dentine demineralization induced by in vitro and in situ models, and correlated dentine surface hardness (SH), cross-sectional hardness (CSH) and mineral content by transverse microradiography (TMR). Bovine dentine specimens (n = 15/group) were demineralized in vitro with the following: MC gel (6% carboxymethylcellulose gel and 0.1 M lactic acid, pH 5.0, 14 days); buffer I (0.05 M acetic acid solution with calcium, phosphate and fluoride, pH 4.5, 7 days); buffer II (0.05 M acetic acid solution with calcium and phosphate, pH 5.0, 7 days), and TEMDP (0.05 M lactic acid with calcium, phosphate and tetraethyl methyl diphosphonate, pH 5.0, 7 days). In an in situ study, 11 volunteers wore palatal appliances containing 2 bovine dentine specimens, protected with a plastic mesh to allow biofilm development. The volunteers dripped a 20% sucrose solution on each specimen 4 times a day for 14 days. In vitro and in situ lesions were analyzed using TMR and statistically compared by ANOVA. TMR and CSH/SH were submitted to regression and correlation analysis (p < 0.05). The in situ model produced a deep lesion with a high R value, but with a thin surface layer. Regarding the in vitro models, MC gel produced only a shallow lesion, while buffers I and II as well as TEMDP induced a pronounced subsurface lesion with deep demineralization. The relationship between CSH and TMR was weak and not linear. The artificial dentine carious lesions induced by the different models differed significantly, which in turn might influence further de- and remineralization processes. Hardness analysis should not be interpreted with respect to dentine mineral loss.

Effect of fluoridated milk on enamel and root dentin demineralization evaluated by a biofilm caries model.

Although some studies suggest an anticaries effect of fluoridated bovine milk (F-milk) on enamel, evidence is still considered weak. Even more uncertain, the effect of F-milk on root caries remains largely unknown. This study evaluated the effect of F-milk on enamel and on root dentin demineralization using a validated Streptococcus mutans biofilm model, simulating a high cariogenic challenge. S. mutans (UA159) biofilms were formed on bovine enamel and root dentin saliva-coated slabs after measuring initial surface microhardness (SH). Biofilms were exposed to 10% sucrose 8×/day and treated 2×/day with either: (1) 0.9% NaCl (negative control), (2) bovine milk, (3) F-milk (5.0 ppm F as NaF) or (4) NaF 0.05% (anticaries-positive control). Medium pH was monitored twice/day, as a biofilm acidogenicity indicator. After 5 days for enamel and 4 days for dentin, biofilms were recovered to analyze: biomass, soluble proteins, viable microorganisms, and extra- and intracellular polysaccharides. Enamel and dentin demineralization were estimated by percentage of SH loss. Results were compared by ANOVA and Tukey's test. Neither acidogenicity nor biofilm composition differed among treatment groups in biofilms formed on enamel or dentin (p > 0.05). F-milk, however, significantly reduced enamel and dentin demineralization when compared with the negative control (p < 0.05). Also, F-milk was as efficient as 0.05% NaF to reduce enamel (p > 0.05), but not dentin demineralization (p < 0.05). These findings suggest that milk containing 5.0 ppm of fluoride is effective to control enamel caries and that it may be effective on root dentin caries prevention.

Effect of hydrogen peroxide at 35% on the morphology of enamel and interference in the de-remineralization process: an in situ study.

This study evaluated the microhardness and histomorphology of bovine enamel when 35% hydrogen peroxide is used. A total of 44 specimens were adapted to removable devices used by 11 individuals subjected to dental caries challenge. A decrease in microhardness was observed for all groups after the cariogenic challenge. Microscopic analysis revealed that fragments subjected to cariogenic challenge associated with bleaching had more intense superficial histologic changes, but the depth of the lesions remained unchanged. It was concluded that 35% hydrogen peroxide enhanced the reduction in hardness and histomorphologic changes in the enamel surface exposed to cariogenic challenge.

Effect of cariogenic biofilm challenge on the surface hardness of direct restorative materials in situ.

OBJECTIVES: The presence of cariogenic biofilm could result in surface degradation of composite and ionomeric restorative materials. Thus, this study evaluated in situ the alterations in the surface microhardness of these materials under biofilm accumulation and cariogenic challenge. METHODS: In a split-mouth, double-blind, cross-over study, 10 volunteers wore palatal intra-oral devices containing bovine enamel slabs restored with composite resin (CR - Z250) or resin-modified glass ionomer (RMGI - Vitremer). Two phases of 14 days were carried out, one for each restorative material. In one side of the device, biofilm was allowed to accumulate under a plastic mesh, whereas in the opposing side, regular brushing was carried out 3 times/day with a dentifrice containing 1100 µg F/g as NaF. A 20% sucrose solution was applied extra-orally 10×/day on each restored dental slab. Knoop microhardness was used to calculate the percentage of surface hardness loss (%SHL). RESULTS: All materials showed a decrease in surface hardness after the in situ period. The restorative materials presented the following average for %SHL: RMGI without biofilm accumulation=8.9 and with biofilm accumulation=25.6, CR without biofilm accumulation=14.7 and with biofilm accumulation=17.0. CONCLUSION: Biofilm accumulation and the presence of cariogenic challenge promoted faster degradation of ionomeric materials, but this was not observed for composite resin. CLINICAL SIGNIFICANCE: The oral environment affects the surface hardness of aesthetic restorative materials. Biofilm accumulation and cariogenic challenge promote surface degradation for ionomeric materials, but not for composite resin.

Effect of acidulated phosphate fluoride gel application time on enamel demineralization of deciduous and permanent teeth.

Although the effect of acidulated phosphate fluoride gel (APF gel) on caries reduction in permanent teeth is based on evidence, the relevance of the clinical application time is still under debate. Also, the effect of 4- versus 1-min application has not been evaluated in deciduous enamel. In a blind, crossover, in situ study of 14 days, 16 adult volunteers wore palatal appliances containing slabs of human permanent and deciduous enamel. At the beginning of each phase, the slabs were submitted to one of the following treatments: no APF application (negative control); APF gel (1.23% F) application for 1 or 4 min. Biofilm accumulation on the slab surface was allowed and the slabs were subjected eight times a day to 20% sucrose, simulating a high cariogenic challenge condition. On the 15th day of each phase, fluoride retained as CaF(2) and fluorapatite (FAp) was determined on the enamel of the slabs and demineralization was assessed by cross-sectional microhardness. Fluoride as CaF(2) and FAp, formed by APF gel application on the enamel slabs not subjected to the cariogenic challenge, was also determined. APF gel reduced demineralization in both enamel types (p < 0.05), but the difference between 1 and 4 min was not statistically significant (p > 0.05). CaF(2) and FAp formed and retained on deciduous and permanent enamel was significantly higher in APF gel groups (p < 0.05), but no significant difference was found between 1 and 4 min (p > 0.05). The findings suggest that 1 min of APF gel application provides a similar effect on inhibition of demineralization as 4 min, for both permanent and deciduous enamel.

Effect of a glass ionomer cement and a fluoride varnish on cross-sectional microhardness values of artificial occlusal caries: in vitro study.

CONTEXT: Active white spot lesions (WSLs) are a great concern to clinicians. AIMS: This in vitro experiment analyzed cross-sectional microhardness (CSMH) values of occlusal artificially induced active WSLs (control groups D/A, D/B and D/C) along with experimental groups where these lesions were: Exposed to an artificial high risk cariogenic challenge (HRCC) using pH cycling; treated with a glass ionomer cement (GIC) and then exposed to artificial HRCC; or a fluoride varnish (FV) and afterwards submitted to the same artificial HRCC. MATERIALS AND METHODS: Sixty unerupted human third molars were sectioned buccolingually on the occlusal surface and demineralized for 42 days. One half of each tooth was allocated to control groups (D/A, D/B, and D/C) and the other were used as test groups: A (pH cycling); B (GIC + pH cycling); and C (FV + pH cycling). CSMH test was performed for sound, demineralized, and treated specimens. STATISTICAL ANALYSIS USED: Different depths for CSMH values did not have a normal distribution (Kolmogrov-Smirnov test) and for that matter Wilcoxon and T Test were applied (significance level of 5%). RESULTS: Mean depth of the lesion was 120 µm. A number of samples both in the test groups (n = 37) as in control groups (n = 47) had a lower Knoo p value (softening) or surface erosion. Comparisons between control and test groups only showed statistical difference at a depth 140 µm (P = 0.010) in control group D/A and for test group B at 20 µm (P = 0.004) and at 40 µm (P = 0.007). CONCLUSIONS: This in vitro study demonstrated that the use of GIC over an artificial active WSLs and exposed to an artificially HRCC setting tend to express some effect in increased surface KHN values.

Microcosm biofilms originating from children with different caries experience have similar cariogenicity under successive sucrose challenges.

OBJECTIVES: The source of saliva inocula and the individual characteristics of saliva donors could affect the cariogenic activity of in vitro biofilms, but this could also be modulated by environmental determinants, such as the frequency of sugar consumption. Therefore, the aim of this study was to compare the cariogenicity of microcosm biofilm growths from the saliva of caries-free (CF) children, children with early childhood caries (ECC) and with severe ECC (S-ECC), under regular sucrose exposure. METHODS: Microcosm plaque biofilms were initiated from the saliva of CF, ECC and S-ECC children. Biofilms were grown in 24-well microplates on bovine enamel discs for up to 10 days in artificial saliva, which was replaced daily. Growth conditions comprised cariogenic challenge (artificial saliva supplemented with 1% sucrose 6 h/day) or no cariogenic challenge. Daily pH was obtained from the artificial saliva, and after the experimental period, the biofilm formed on the enamel discs was collected for microbiological analyses. Mineral loss in enamel discs was estimated by percentage of surface hardness change. RESULTS: Overall, no statistically significant differences were found among saliva sources (p > 0.05). Streptococcus mutans and lactobacilli counts increased in the biofilms grown under cariogenic challenge (p < 0.05), while a substantial decrease in the artificial saliva pH was detected under the same condition (p < 0.001). Higher demineralization (p < 0.001) was observed under sucrose exposure regardless of caries experience of children. CONCLUSIONS: While the sucrose exposure determined the cariogenicity of the biofilms, the caries experience of children who provided the inocula did not affect mineral loss associated with these biofilms.

Microhardness and SEM after CO(2) laser irradiation or fluoride treatment in human and bovine enamel.

BACKGROUND: It remains uncertain as to whether or not CO(2) laser is able to hinder demineralization of enamel. The possibility to use bovine instead of human teeth on anticariogenic studies with laser has not yet been determined. PURPOSE: To compare the ability of CO(2) laser and fluoride to inhibit caries-like lesions in human enamel and to test whether a similar pattern of response would hold for bovine enamel. STUDY DESIGN: Ninety-six enamel slabs (2 × 2 × 4 mm) (48 from bovine and 48 from human teeth) were randomly distributed according to surface treatment (n = 12): CO(2) laser, 5% sodium fluoride varnish (FV), 1.23% acidulated phosphate fluoride (APF) gel, or no treatment (control). Specimens were subjected to a 14-day in vitro cariogenic challenge. Microhardness (SMH) was measured at 30 µm from the surface. For ultrastructural analysis, additional 20 slabs of each substrate (n = 5) received the same treatment described earlier and were analyzed by SEM. RESULTS: ANOVA and Tukey test ascertained that CO(2) laser promoted the least mineral loss (SMH = 252(a)). Treatment with FV resulted in the second highest values (207(b)), which was followed by APF (172(c)). Untreated specimens performed the worst (154(d)). SEM showed no qualitative difference between human and bovine teeth. APF and control groups exhibited surfaces covered by the smear layer. A granulate precipitate were verified on FV group and fusion of enamel crystals were observed on lased-specimens. CONCLUSIONS: CO(2) laser may control caries progression more efficiently than fluoride sources and bovine teeth may be a suitable substitute for human teeth in studies of this nature.

Effect of a calcium glycerophosphate fluoride dentifrice formulation on enamel demineralization in situ.

PURPOSE: To evaluate in situ the effect and mechanisms involved in the anticariogenic effect of a calcium glycerophosphate fluoride dentifrice. METHODS: In a double-blind, crossover design, a non-F dentifrice (negative control), a F dentifrice and a F dentifrice containing 0.13% CaGP were compared regarding the inhibition of enamel demineralization. Both F dentifrices contained 1500 microg F/g (w/w) as sodium monofluorophosphate (MFP). Bovine enamel blocks were mounted in contact with a S. mutans test plaque, in palatal appliances worn by 10 volunteers. 30 minutes after treatment with the dentifrices, a sucrose rinse was performed and enamel demineralization was assessed after an additional 45 minutes. RESULTS: No significant difference was observed among groups in the calcium and inorganic phosphate concentrations in the fluid phase of the test plaque 30 minutes after the dentifrice use (P > 0.05), but F concentration was significantly higher for both F dentifrices (P < 0.05). Also, the dentifrices did not differ regarding the pH before or 5 minutes after the sugar challenge (P > 0.05). A higher mineral loss was observed for the non-F dentifrice group (P < 0.05), but no significant difference was observed between the F dentifrices containing CaGP or not (P > 0.05). Using this in situ model, the findings suggested that CaGP at the concentration tested did not enhance the inhibition of enamel demineralization promoted by F dentifrice.

Effects of sucrose on the extracellular matrix of plaque-like biofilm formed in vivo, studied by proteomic analysis.

Previous studies have shown that sucrose promotes changes in the composition of the extracellular matrix (ECM) of plaque-like biofilm (PLB), but its effect on protein expression has not been studied in vivo. Therefore, the protein compositions of ECM of PLB formed with and without sucrose exposure were analyzed by two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). For this purpose, a crossover study was conducted during two phases of 14 days each, during which a volunteer wore a palatal appliance containing eight enamel blocks for PLB accumulation. In each phase, a 20% sucrose solution or distilled and deionized water (control) were extraorally dripped onto the blocks 8x/day. On the 14th day, the PLB were collected, the ECM proteins were extracted, separated by two-dimensional gel electrophoresis, digested by in-gel trypsin and MALDI-TOF MS analyzed. In the ECM of PLB formed under sucrose exposure, the following changes compared with the control PLB were observed: (1) the presence of upregulated proteins that may be involved in bacterial response to environmental changes induced by sucrose and (2) the absence of calcium-binding proteins that may partly explain the low inorganic concentration found in ECM of PLB formed under sucrose exposure. The findings showing that sucrose affected the ECM protein composition of PLB in vivo provide further insight into the unique cariogenic properties of this dietary carbohydrate.

Effect of starch and sucrose on dental biofilm formation and on root dentine demineralization.

The cariogenicity of starch alone or in combination with sucrose is controversial and the effect on dentine demineralization and on the dental biofilm formed has not been explored under controlled conditions. A crossover, single-blind study was conducted in four steps of 14 days each, during which 11 volunteers wore palatal appliance containing 10 slabs of root dentine to which the following treatments were applied extraorally: 2% starch gel-like solution (starch group); 10% sucrose solution (sucrose group); a solution containing 2% starch and 10% sucrose (starch + sucrose group), or 2% starch solution followed by 10% sucrose solution (starch --> sucrose group). On the 14th day of each phase the biofilms were collected for biochemical and microbiological analyses, and dentine demineralization was assessed by hardness. A higher demineralization was found in dentine exposed to sucrose and starch sucrose combinations than to starch alone (p < 0.01), but the sucrose-containing groups did not differ significantly from each other (p > 0.05). The concentrations of soluble and insoluble extracellular polysaccharides (EPS), and the proportion of insoluble EPS, were lower in the biofilm formed in presence of starch (p < 0.01) than in those formed in the presence of sucrose or sucrose/starch combinations; however, no significant difference was observed among the groups containing sucrose (p > 0.05). RNA was successfully isolated and purified from in situ biofilms and only biofilms formed in response to sucrose and starch/sucrose combinations showed detectable levels of gtfB and gtfC mRNA. The findings suggest that the combination of starch with sucrose may not be more cariogenic to dentine than sucrose alone.

Effect of microleakage and fluoride on enamel-dentine demineralization around restorations.

There is no consensus about an association between microleakage and secondary caries, especially considering the presence of fluoride (F) at the tooth/restoration interface. Thus, a randomized, double-blind, crossover study was carried out to evaluate in situ the effect of microleakage on caries around enamel-dentine restorations in the presence of F from dental materials or dentifrice, either alone or in combination. In 4 phases of 14 days each, 14 volunteers wore palatal devices containing dental slabs restored with composite resin (CR) or resin-modified glass ionomer cement (GI). Restorations were made without leakage (L-), following the recommended adhesive procedures, or with leakage (L+), in the absence of adhesive procedures. Plaque-like biofilm (PLB) was left to accumulate on the restored slabs, which were exposed extraorally to a 20% sucrose solution 10x/day. The volunteers used a non-F (NF) or an F (FD) dentifrice 3x/day, depending on the experimental phase. No differences were found between L+ or L- restorations (p > 0.05). Higher demineralization in both enamel and dentine around CR restorations was observed under NF (p < 0.05). F concentration was higher in the fluid of PLB exposed to FD or formed onto GI restoration (p < 0.05). These results suggest that while microleakage does not affect caries development, GI or FD may maintain increased F levels in the PLB, thereby decreasing caries progression.