In situ protocol for the detemination of dose-response effect of low-fluoride dentifrices on enamel remineralization

No in situ protocol has assessed the dose-response effects of fluoride dentifrices involving low-fluoride formulations. Objective: To assess the ability of an in situ remineralization model in determining dose-response effects of dentifrices containing low fluoride concentrations ([F]) on bovine enamel. Material and Methods: Volunteers wore palatal appliances containing demineralized enamel blocks and brushed their teeth and devices with the dentifrices supplied (double-blind, crossover protocol) separately for 3 and 7 days. Surface hardness (SH), integrated subsurface hardness (AKHN) and [F] in enamel were determined. Data were analyzed by ANOVA, Tukey's test and Pearson's correlation (p<0.05). Results: Dose-response relationships were verified between [F] in dentifrices and SH, AKHN and enamel [F]. Higher correlation coefficients between enamel [F] and SH and AKHN were obtained for the 3-day period. Significant differences in SH and AKHN were observed among all groups for the 3-day period, but not between 0-275, 275-550, and 550-1,100 mu g F/g dentifrices for the 7-day period, nor between 3- and 7-day periods for the 1,100 mu g F/g groups. Conclusions: Considering that the peak remineralization capacity of the conventional dentifrice (1,100 mu g F/g) was achieved in 3 days, this experimental period could be used in future studies assessing new dentifrice formulations, especially at low-fluoride concentrations.

In situ evaluation of low-fluoride toothpastes associated to calcium glycerophosphate on enamel remineralization

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Saliva substitutes in combination with high-fluoride gel on dentin remineralization

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

In vitro enamel remineralization capacity of composite resins containing sodium trimetaphosphate and fluoride

This study evaluated the in vitro enamel remineralization capacity of experimental composite resins containing sodium trimetaphosphate (TMP) combined or not with fluoride (F). Bovine enamel slabs were selected upon analysis of initial surface hardness (SH1) and after induction of artificial carious lesions (SH2). Experimental resins were as follows: resin C (control-no sodium fluoride (NaF) or TMP), resin F (with 1.6 % NaF), resin TMP (with 14.1 % TMP), and resin TMP/F (with NaF and TMP). Resin samples were made and attached to enamel slabs (n = 12 slabs per material). Those specimens (resin/enamel slab) were subjected to pH cycling to promote remineralization, and then final surface hardness (SH3) was measured to calculate the percentage of surface hardness recovery (%SH). The integrated recovery of subsurface hardness (ΔKHN) and F concentration in enamel were also determined. Data was analyzed by ANOVA and Student-Newman-Keuls test (p < 0.05). Resins F and TMP/F showed similar SH3 values (p = 0.478) and %SH (p = 0.336) and differed significantly from the other resins (p < 0.001). Considering ΔKHN values, resin TMP/F presented the lowest area of lesion (p < 0.001). The presence of F on enamel was different among the fluoridated resins (p = 0.042), but higher than in the other resins (p < 0.001). The addition of TMP to a fluoridated composite resin enhanced its capacity for remineralization of enamel in vitro. The combination of two agents with action on enamel favored remineralization, suggesting that composite resins containing sodium trimetaphosphate and fluoride could be indicated for clinical procedures in situations with higher cariogenic challenges.

Amorphous calcium phosphate sealants: remineralization of carious lesions in the enamel can be achieved with use of pit-and-fissure sealants containing amorphous calcium phosphate

New pit-and-fissure sealants with the capacity to release calcium and phosphate because of the presence of ACP have been introduced into the dental marketplace. With the continuous introduction of new dental materials, it is important not only to research and confirm their properties, but also to propose modifications or associations that may contribute to their improvement.

Effect of low fluoride acidic dentifrices on dental remineralization

This study evaluated the capacity of fluoride acidic dentifrices (pH 4.5) to promote enamel remineralization using a pH cycling model, comparing them with a standard dentifrice (1,100 µgF/g). Enamel blocks had their surface polished and surface hardness determined (SH). Next, they were submitted to subsurface enamel demineralization and to post-demineralization surface hardness analysis. The blocks were divided into 6 experimental groups (n=10): placebo (without F, pH 4.5, negative control), 275, 412, 550, 1,100 µgF/g and a standard dentifrice (positive control). The blocks were submitted to pH cycling for 6 days and treatment with dentifrice slurries twice a day. After pH cycling, surface and cross-sectional hardness were assessed to obtain the percentage of surface hardness recovery (%SHR) and the integrated loss of subsurface hardness (ΔKHN). The results showed that %SHR was similar among acidic dentifrices with 412, 550, 1,100 µgF/g and to the positive control (Tukey's test; p>0.05). For ΔKHN, the acidic dentifrice with 550 µg F/g showed a better performance when compared with the positive control. It can be concluded that acidic dentifrice 550 µgF/g had similar remineralization capacity to that of positive control.

Regional differences in modelled net production and shallow remineralization in the North Atlantic subtropical gyre

[EN] We used 5-yr concomitant data of tracer distribution from the BATS (Bermuda Time-series Study) and ESTOC (European Station for Time-Series in the Ocean, Canary Islands) sites to build a 1-D tracer model conservation including horizontal advection, and then compute net production and shallow remineralization rates for both sites. Our main goal was to verify if differences in these rates are consistent with the lower export rates of particulate organic carbon observed at ESTOC. Net production rates computed below the mixed layer to 110m from April to December for oxygen, dissolved inorganic carbon and nitrate at BATS (1.34±0.79 molO2 m?2, ?1.73±0.52 molCm?2 and ?125±36 mmolNm?2) were slightly higher for oxygen and carbon compared to ESTOC (1.03±0.62 molO2 m?2, ?1.42±0.30 molCm?2 and ?213±56 mmolNm?2), although the differences were not statistically significant. Shallow remineralization rates between 110 and 250m computed at ESTOC (?3.9±1.0 molO2 m?2, 1.53±0.43 molCm?2 and 38±155 mmolNm?2) were statistically higher for oxygen compared to BATS (?1.81±0.37 molO2 m?2, 1.52± 0.30 molCm?2 and 147±43 mmolNm?2). The lateral advective flux divergence of tracers, which was more significant at ESTOC, was responsible for the differences in estimated oxygen remineralization rates between both stations. According to these results, the differences in net production and shallow remineralization cannot fully explain the differences in the flux of sinking organic matter observed between both stations, suggesting an additional consumption of nonsinking organic matter at ESTOC.

Remineralization of initial carious lesions in deciduous enamel after application of dentifrices of different fluoride concentrations

The aim of the present study was to evaluate the remineralization potential of five dentifrices with different fluoride concentrations. Initial caries lesions were created in 72 cylindrical enamel blocks from deciduous teeth. The specimens were randomly distributed among six experimental groups corresponding to six experimental periods. Each of the six volunteers carried two deciduous enamel specimens fixed in an intraoral appliance for a period of 4 weeks. They brushed their teeth and the enamel blocks at least two times a day with dentifrices containing 0 ppm (period 1), 250 ppm (period 2), and 500 ppm fluoride (period 3), respectively. A second group of volunteers (n = 6) used dentifrices with a fluoride content of 0 ppm (period 4), 1,000 ppm (period 5), or 1,500 ppm (period 6). At the end of the respective period, the mineral content was determined by transversal microradiography (TMR). The use of dentifrices containing 500 ppm fluoride (38% MR), 1,000 ppm fluoride (42% MR), and 1,500 ppm fluoride (42% MR) resulted in a statistically significant higher mineral recovery compared to the control group (0 ppm fluoride). Mineral recovery was similar after use of dentifrices containing 0 and 250 ppm fluoride (24%; 25%). It is concluded that it is possible to remineralize initial carious lesions in deciduous enamel in a similar way as it has been described for enamel of permanent teeth.

In situ fluoride retention and remineralization of incipient carious lesions after the application of different concentrations of fluoride

Limited information is available on the time-dependent or dosage-dependent cariostatic efficacy of highly concentrated fluoride compounds. This good clinical practice-conforming, double-blind, placebo-controlled, crossover in situ study tested the hypothesis that a 1.0% amine fluoride fluid is superior to a 0.5% amine fluoride fluid regarding fluoride retention and mineral change in initial caries enamel lesions over a period of 28 d. Fluoride retention was significantly higher after application of the two fluoride fluids compared with placebo but had decreased in both groups to similar levels after only 1 wk. Mineral gain was significantly higher for both verum groups compared with placebo. The use of 1% fluoride fluid resulted in significantly higher remineralization compared with the use of 0.5% fluoride fluid. For both fluoride fluids mineral gain followed a linear relationship with time during the experimental period, indicating a possible further uptake of mineral, even after 4 wk.

Effectiveness of fluorescence-based methods to detect in situ demineralization and remineralization on smooth surfaces.

This study aimed to evaluate the effectiveness of fluorescence-based methods (DIAGNOdent, LF; DIAGNOdent pen, LFpen, and VistaProof fluorescence camera, FC) in detecting demineralization and remineralization on smooth surfaces in situ. Ten volunteers wore acrylic palatal appliances, each containing 6 enamel blocks that were demineralized for 14 days by exposure to a 20% sucrose solution and 3 of them were remineralized for 7 days with fluoride dentifrice. Sixty enamel blocks were evaluated at baseline, after demineralization and 30 blocks after remineralization by two examiners using LF, LFpen and FC. They were submitted to surface microhardness (SMH) and cross-sectional microhardness analysis. The integrated loss of surface hardness (ΔKHN) was calculated. The intraclass correlation coefficient for interexaminer reproducibility ranged from 0.21 (FC) to 0.86 (LFpen). SMH, LF and LFpen values presented significant differences among the three phases. However, FC fluorescence values showed no significant differences between the demineralization and remineralization phases. Fluorescence values for baseline, demineralized and remineralized enamel were, respectively, 5.4 ± 1.0, 9.2 ± 2.2 and 7.0 ± 1.5 for LF; 10.5 ± 2.0, 15.0 ± 3.2 and 12.5 ± 2.9 for LFpen, and 1.0 ± 0.0, 1.0 ± 0.1 and 1.0 ± 0.1 for FC. SMH and ΔKHN showed significant differences between demineralization and remineralization phases. There was a negative and significant correlation between SMH and LF and LFpen in the remineralization phase. In conclusion, LF and LFpen devices were effective in detecting demineralization and remineralization on smooth surfaces provoked in situ.

Organic carbon flux and remineralization in surface sediments

Organic carbon fluxes through the sediment/water interface in the high-latitude North Atlantic were calculated from oxygen microprofiles. A wire-operated in situ oxygen bottom profiler was deployed, and oxygen profiles were also measured onboard (ex situ). Diffusive oxygen fluxes, obtained by fitting exponential functions to the oxygen profiles, were translated into organic carbon fluxes and organic carbon degradation rates. The mean Corg input to the abyssal plain sediments of the Norwegian and Greenland Seas was found to be 1.9 mg C/m**2/d. Typical values at the seasonally ice-covered East Greenland continental margin are between 1.3 and 10.9 mg C/m**2/d (mean 3.7 mg C/m**2/d), whereas fluxes on the East Greenland shelf are considerably higher, 9.1-22.5 mg C/m**2/d. On the Norwegian continental slope Corg fluxes of 3.3-13.9 mg C/m**2/d (mean 6.5 mg C/m**2/d) were found. Fluxes are considerably higher here compared to stations on the East Greenland slope at similar water depths. By repeated occupation of three sites off southern Norway in 1997 the temporal variability of diffusive O2 fluxes was found to be quite low. The seasonal signal of primary and export production from the upper water column appears to be strongly damped at the seafloor. Degradation rates of 0.004-1.1 mg C/cm**3/a at the sediment surface were calculated from the oxygen profiles. First-order degradation constants, obtained from Corg degradation rates and sediment organic carbon content, are in the range 0.03-0.6/a. Thus, the corresponding mean lifetime of organic carbon lies between 1.7 and 33.2 years, which also suggests that seasonal variations in Corg flux are small. The data presented here characterize the Norwegian and Greenland Seas as oligotrophic and relatively low organic carbon deep-sea environments.

Dentin Bond Strength Of A Fluoride-releasing Adhesive System Submitted To Ph-cycling.

To evaluate the microtensile bond strength (µTBS) of a fluoride-containing adhesive system submitted to a pH-cycling and storage time regimen for primary outcomes. As secondary outcomes the fluoride released amount was evaluated. Twelve dentin surfaces from sound third molar were divided into 2 groups according to adhesive systems: Clearfil SE Protect (PB) and Clearfil SE Bond (SE). Sticks obtained (1.0 mm2) from teeth were randomly divided into 3 subgroups according to storage regimen model: immediate (24h); 5-month deionized water (W); and pH-cycling model (C). All sticks were tested for µTBS in a universal testing machine. Fluoride concentration was obtained from 1-4 days and 30-day in W and 1-4 days in demineralization (DE)/remineralization (RE) solutions from C, using a fluoride-specific electrode. µTBS and fluoride released data were, respectively, submitted to ANOVA in a split plot design and Tukey, and Friedman' tests (a=0.05). There was no significant interaction between adhesive system and storage regimen for µTBS. W showed the lowest µTBS values. There was no significant difference between 24 h and C models for µTBS. There was no significant difference between adhesive systems. Failure mode was predominantly cohesive within composite for the 24 h and W, for the C group it was mixed for SE and cohesive within composite for PB adhesive system. Fluoride concentrations in the DE/RE solutions were less than 0.03125 ppm and not detected in W. In conclusion, the fluoride-containing adhesive system performed similarly to the regular one. Hydrolytic degradation is the main problem with both adhesive systems, regardless of fluoride contents.

Insights into preventive measures for dental erosion

Dental erosion is defined as the loss of tooth substance by acid exposure not involving bacteria. The etiology of erosion is related to different behavioral, biological and chemical factors. Based on an overview of the current literature, this paper presents a summary of the preventive strategies relevant for patients suffering from dental erosion. Behavioral factors, such as special drinking habits, unhealthy lifestyle factors or occupational acid exposure, might modify the extent of dental erosion. Thus, preventive strategies have to include measures to reduce the frequency and duration of acid exposure as well as adequate oral hygiene measures, as it is known that eroded surfaces are more susceptible to abrasion. Biological factors, such as saliva or acquired pellicle, act protectively against erosive demineralization. Therefore, the production of saliva should be enhanced, especially in patients with hyposalivation or xerostomia. With regard to chemical factors, the modification of acidic solutions with ions, especially calcium, was shown to reduce the demineralization, but the efficacy depends on the other chemical factors, such as the type of acid. To enhance the remineralization of eroded surfaces and to prevent further progression of dental wear, high-concentrated fluoride applications are recommended. Currently, little information is available about the efficacy of other preventive strategies, such as calcium and laser application, as well as the use of matrix metalloproteinase inhibitors. Further studies considering these factors are required. In conclusion, preventive strategies for patients suffering from erosion are mainly obtained from in vitro and in situ studies and include dietary counseling, stimulation of salivary flow, optimization of fluoride regimens, modification of erosive beverages and adequate oral hygiene measures.