Effect of APF gel application time on enamel demineralization and fluoride uptake in situ

A Comparison of the Fluoride 'Paint- On' vs Tray Application Techniques for Enamel Remineralisation

BACKGROUND

Fluoride gel treatment is not recommended for children < 6 years old due to its potential toxicity. Hence the aim of this study was to compare the effect of 1.23% acidulated-phosphate fluoride (APF) gel paint-on and the conventional tray application techniques on artificial, deciduous enamel carious lesions embedded on wearable appliances.

METHODS

In a randomised crossover study, the volunteer children (n = 29) wore mandibular removable appliances containing embedded tooth specimens with artificial carious lesions. The volunteers had 3 different treatment protocols: (I) 0.4 mL non-fluoride (control) gel, (II) 0.4 mL paint-on 1.23% APF gel or (III) 5 mL 1.23% APF gel, 4 minutes tray application. After 1 hour, the appliances were removed and the specimens underwent an in vitro, 14 days of pH-cycling. The mean percentage reduction in fluorescence (ΔF, %) at baseline (ΔF0) and after the pH-cycling (ΔF1) were determined using quantitative light-induced fluorescence-digital analysis. The mean ΔΔF (ΔF1-ΔF0) was calculated to compare the differences between groups.

RESULTS

The mean ΔΔF of groups I to III were -1.42 ± 1.49, 1.06 ± 2.11, and 1.12 ± 3.57 and -1.25 ± 1.44, 1.13 ± 1.84 and 1.44 ± 3.62 for the smooth surface and proximal surface lesions, respectively. The mean ΔΔF in the 2 treatment groups were significantly greater compared with the control group (P < .001). There was no significant difference in ΔΔF between the APF gel tray and paint-on groups either in the smooth surfaces, or the proximal surfaces (P = .629 and P = .613, respectively).

CONCLUSION

Our study, for the first time, indicates that the paint-on application of APF gel or the tray application of APF had a similar enamel remineralisation effect. Clinically, this implies that, particularly in younger children, the paint-on application of fluoride is less cumbersome, and possibly more tolerable with a lesser likelihood of fluoride ingestion than the tray application technique.

TRIAL REGISTRATION

Thai Clinical Trial Registry (https://www.thaiclinicaltrials.org/show/TCTR20190724001).

Effect of fluoride gels with nano-sized sodium trimetaphosphate on the in vitro remineralization of caries lesions

OBJECTIVE

To evaluate the effects of fluoride (F) gels supplemented with micrometric or nano-sized sodium trimetaphosphate (TMPmicro and TMPnano, respectively) on the in vitro remineralization of caries-like lesions.

METHODOLOGY

Bovine enamel subsurface lesions (n=168) were selected according to their surface hardness (SH) and randomly divided into seven groups (n=24/group): Placebo (without F/TMP), 4,500 ppm F (4500F), 4500F + 2.5% TMPnano (2.5% Nano), 4500F + 5% TMPnano (5% Nano), 4500F + 5% TMPmicro (5% Micro), 9,000 ppm F (9000F), and 12,300 ppm F (Acid gel). The gels were applied in a thin layer for one minute. Half of the blocks were subjected to pH cycling for six days, whereas the remaining specimens were used for loosely- (calcium fluoride; CaF2) and firmly-bound (fluorapatite; FA) fluoride analysis. The percentage of surface hardness recovery (%SHR), area of subsurface lesion (ΔKHN), CaF2, FA, calcium (Ca), and phosphorus (P) on/in enamel were determined. Data (log10-transformed) were subjected to ANOVA and the Student-Newman-Keuls' test (p<0.05).

RESULTS

We observed a dose-response relation between F concentrations in the gels without TMP for %SHR and ΔKHN. The 2.5% Nano and 5% Micro reached similar %SHR when compared with 9000F and Acid gels. For ΔKHN, Placebo and 5% Nano gels had the highest values, and 5% Micro, 2.5% Nano, 9000F, and Acid gels, the lowest. All groups had similar retained CaF2 values, except for Placebo and Acid gel. We verified observed an increase in Ca concentrations in nano-sized TMP groups. Regarding P, TMP groups showed similar formation and retention to 9000F and Acid.

CONCLUSION

Adding 2.5% nano-sized or 5% micrometric TMP to low-fluoride gels lead to enhanced in vitro remineralization of artificial caries lesions.

Anticaries potential of a fluoride foam

Foam has been used worldwide as a vehicle for the professional application of fluoride and hypothetically should have the same anticaries potential as conventional fluoride gel (F-gel) in terms of the formation of reaction products with enamel. Thus, the ability of Flúor Care® foam (FGM, Joinville, SC, Brazil, 12,300 ppm F, acidulated) to react with enamel was evaluated in comparison with Flúor gel® (DFL, Rio de Janeiro, RJ, Brazil, 12,300 ppm F, acidulated). Slabs (n=10/group) of sound enamel and with caries lesion were used, in which the concentrations of total fluoride (TF), and loosely (CaF2-like) and firmly (FAp) bound types were determined. The importance of agitation during application was previously tested. The determinations were made with fluoride ion-specific electrode and the results were expressed in μg F/cm² of the treated enamel area. ANOVA and Tukey tests were used to analyze the difference among treatments, independently for sound and carious enamel. The agitation of the products during application significantly increased the reactivity of the foam (p<0.05), but not that of the gel (p>0.05). The foam did not differ from F-gel (p>0.05) concerning the formation of TF and CaF2-like in sound or carious enamel. Regarding FAp, the foam did not differ from F-gel (p>0.05) in the carious enamel, but the concentration in the sound was lower (p<0.05). The results show that this commercial fluoride foam tested needs to be agitated during application to improve its reactivity with enamel, which raises a question about other brands.

Early childhood caries management using fluoride varnish and neutral fluoride gel: a randomized clinical trial

The aim of this study was to evaluate the clinical efficacy of varnish and neutral fluoride gel in the management of early childhood caries (ECC). A randomized clinical trial was conducted to compare two strategies for ECC management: topical application of neutral fluoride gel (NFG group) and varnish (FV group) every four months for a period of one year. The sample consisted of children between the ages of three and four years, enrolled in public daycare centers. The incidence of ECC between the groups was compared by assessing values (new dmfs) at two levels: d2 when enamel/dentin were affected and d3 when dentin affected. Pearson's Chi-square, Fisher's Exact, Kolmogorov-Smirnov and Mann-Whitney tests were used to compare the incidence and increment of caries between the NFG and FV groups (p<0.05). A total of 240 children were included in this study and 213 children (88.7%) were followed up for 12 months. The incidence of ECC was 24.1% in the GF and 21.0% in the FV groups (p=0.586). The increment of caries in d2mfs was 1.36 (95% CI = 0.83 - 1.89) in the NFG and 1.33 (95% CI = 0.75 - 1.89) in FV (p=0.756) groups. Increment of caries in d3mfs was 1.60 (95% CI = 0.95 - 2.25) in NFG and 1.40 (95% CI = 0.75 - 2.04) in FV (p=0.468). Neutral fluoride gel and fluoride varnish exhibited similar efficacy in the management of ECC after 12 months of follow-up.

Engineered Salivary Peptides Reduce Enamel Demineralization Provoked by Cariogenic S. mutans Biofilm

Engineering of the acquired enamel pellicle using salivary peptides has been shown to be a promising anticaries strategy. However, the mechanisms by which these peptides protect teeth against tooth decay are not fully understood. In this study, we evaluated the effect of the engineered salivary peptides DR9-DR9 and DR9-RR14 on enamel demineralization in two experimental conditions: (1) adsorbed onto the enamel surface forming the AEP, and (2) forming the AEP combined with their use to treat the biofilms 2×/day, using a validated cariogenic Streptococcus mutans in vitro biofilm model. Biofilms were grown for 144 h on enamel slabs and then collected to determine the bacterial viability (CFU/biofilm) and biofilm mass (mg protein/biofilm), and to extract cellular/extracellular proteins, which were characterized by mass spectrometry. The culture medium was changed 2×/day to fresh medium, and pH (indicator of biofilm acidogenicity) and calcium concentration (indicator of demineralization) was determined in used medium. DR9-RR14 peptide significantly reduced enamel demineralization (p < 0.0001) in both experimental conditions. However, this peptide did not have a significant effect on biofilm biomass (p > 0.05) nor did it modulate the expression of cellular and extracellular bacterial proteins involved in biofilm cariogenicity. These findings suggest that DR9-RR14 may control caries development mainly by a physicochemical mechanism.

Insoluble NaF in Duraphat® may prolong fluoride reactivity of varnish retained on dental surfaces

There is no consensus about the clinical recommendation of the time that Duraphat® varnish should be maintained on enamel surfaces without suffering mechanical disturbance by the patient. Considering the importance of calcium fluoride (CaF2)-like reservoirs on the anticaries effect of professional fluoride application, an in vitro study was designed to test the reactivity of Duraphat® varnish with enamel forming these reservoirs as a function of time. Since most fluoride in Duraphat® varnish is insoluble to react and form products on enamel, the relative contribution of the varnish soluble and insoluble fluoride fractions to the reactivity was also evaluated. For this, whole-varnish, containing soluble and insoluble fluoride (total fluoride concentration of 23699 ± 384 µg F/g), or centrifuged varnish, containing only soluble fluoride (fluoride concentration of 258 ± 97 µg F/g), were applied in a standardized manner on enamel slabs (n=8/varnish group/time), which were immersed in continuously renewed artificial saliva for up to 36 h. CaF2-like reservoirs formed on enamel by varnish application were extracted using 1 M KOH and fluoride concentration was measured with ion specific electrode. The results were expressed as µg F/cm(2) of enamel area. Whole varnish formed significantly higher fluoride concentration on enamel than centrifuged varnish, reaching maximum concentration at 24 h (22.0 ± 4.5 µg F/cm(2)). Centrifuged varnish reached maximum concentration at 6 h (3.20 ± 0.81 µg F/cm(2)). In conclusion, a longer varnish retention time than the usually recommended could improve the anticaries effect of Duraphat® varnish, allowing that NaF particles, initially insoluble in the varnish matrix, prolong the reactivity with enamel.

CO2 laser and topical fluoride therapy in the control of caries lesions on demineralized primary enamel

This study evaluated the effect of CO₂ laser irradiation and topical fluoride therapy in the control of caries progression on primary teeth enamel. 30 fragments (3 × 3 × 2 mm) from primary canines were submitted to an initial cariogenic challenge that consisted of immersion on demineralizing solution for 3 hours and remineralizing solution for 21 hours for 5 days. Fragments were randomly assigned into three groups (n = 10): L: CO₂ laser (λ = 10.6 μm), APF: 1.23% acidulated phosphate fluoride, and C: no treatment (control). CO₂ laser was applied with 0.5 W power and 0.44 J/cm² energy density. Fluoride application was performed with 0.1 g for 1 minute. Cariogenic challenge was conducted for 5 days following protocol previously described. Subsurface Knoop microhardness was measured at 30 μm from the edge. Obtained data were subjected to analysis the variance (ANOVA) and Duncan test with significance of 5%. It was found that the L group showed greater control of deciduous enamel demineralization and were similar to those of APF group, while being statistically different from C group (P ≤ 0.05) that showed the lowest microhardness values. It was concluded that CO₂ laser can be an additional resource in caries control progression on primary teeth enamel.

An in vitro evaluation of the efficacy of a novel iontophoresis fluoride tray on remineralization

Objectives: The aim of this study is to determine the effects on remineralization of a novel iontophoresis device called ‘Fluorinex’, conventional (acidulated phosphat fluoride) APF gel treatment, and conventional ionthophoresis device comparatively by laser fluorescence measurements. Study Design: Artificial incipient carious lesions were created on immature, 60 intact premolar and molar teeth with no defects. The specimens were randomly allocated to four groups. In the first group 1.23% APF gel was applied to specimens by conventional method for 4 minutes and in the second group 2% (sodium fluoride) NaF solution applied by conventional iontophoresis device for 4 minutes. In Fluorinex group specimens were pretreated with (copper chloride) CuCl2 for 1 minute and then treated for 4 minutes with 1.23% APF gel in a Fluoritray. Control group was placed in distilled water for 4 minutes. After these applications all specimens were included to a pH cycling. DIAGNOdent pen measurement were obtained in three different time intervals; after incipient carious lesions, after fluoride treatments and after pH cycling. Specimens were studied by SEM(scanning electron microscopy) after artificial caries lesions and fluoride treatments. Results: Alterations on DIAGNOdent pen measurements before and after treatment, the Fluorinex group was statistically different from conventional APF gel (p=0.011), conventional NaF iontophoresis (p<0.001) and control group (p<0.001). As the DIAGNOdent pen measurements before treatment and after pH cycling were compared, differences were statistically significant in Fluorinex and conventional APF gel groups (p<0.001). Conclusions: The results of this in vitro study has shown that fluoride application by Fluorinex was superior to the conventional APF gel application and NaF iontophoresis on incipient carious lesions.

Key words:Fluoride, iontophoresis, remineralization.

Effect of fluoride gels on microhardness and surface roughness of bleached enamel

The effect of bleaching treatments containing added calcium and combined with neutral or acidic fluoride gels on tooth enamel was investigated in vitro through Knoop microhardness (KHN) and surface roughness (SR) measurements. A total of 60 bovine incisors were tested, including 30 for SR measurements and 30 for KHN measurements. The specimens were divided into 12 groups and subjected to a bleaching agent with hydrogen peroxide 35% (Whiteness HP 35% Maxx, FGM) or hydrogen peroxide 35% with calcium (Whiteness HP 35% Blue Calcium, FGM) and a fluoride treatment flugel acidulated phosphate fluoride (APF) or flugel neutral fluoride (NF). Control specimens were submitted to bleaching treatments without fluoride. Microhardness tests were performed using a Knoop indentor. Roughness measurements were obtained using a roughness analyzer. Measurements were obtained before and after treatment. The specimens were stored in distilled water at 37 °C between treatments. The results were analyzed using descriptive and inferential statistics. Treatments using APF combined with 35% HP caused a decrease in microhardness, while NF combined with HP 35% Ca increased the enamel hardness. Fluoride gels did not alter the SR of the bleached enamel.

Acquired acid resistance of human enamel treated with laser (Er:YAG laser and Co2 laser) and acidulated phosphate fluoride treatment: An in vitro atomic emission spectrometry analysis

BACKGROUND

Dental caries is essentially a process of diffusion and dissolution. If the aspect of dissolution can be curtailed some degree of prevention can be achieved.

AIMS

The present study was carried out to evaluate and compare the effect of Er:YAG laser and Co2 laser irradiation combined with acidulated phosphate fluoride treatment on in vitro acid resistance of human enamel.

DESIGN

An in vitro study was carried out on 30 human premolars to evaluate the enamel's acid resistance using an atomic emission spectrometry analysis.

MATERIALS AND METHODS

A total of 60 enamel specimens were prepared from 30 human premolars and were randomly assigned to 6 groups: (1) Untreated (control); (2) 1.23% acidulated phosphate fluoride (APF) gel application alone for 4 min; (3) Er:YAG laser treatment alone; (4) Co2 laser treatment alone; (5) Er:YAG laser + APF gel application; (6) Co2 laser + APF gel application. The specimens were then individually immersed in 5 ml of acetate buffer solution (0.1 mol/L, pH 4.5) and incubated at 37°C for 24 h, and the acid resistance was evaluated by determining the calcium ion concentration using the atomic emission spectrometry.

STATISTICAL ANALYSIS

An ANOVA model was constructed (P value of 0.05), followed by Tukey's test for multiple pair wise comparisons of mean values.

RESULTS

Significant differences were found between the control group and the test groups (P < 0.001).

CONCLUSIONS

Combining acidulated phosphate fluoride with either Er:YAG or Co2 laser had a synergistic effect in decreasing the enamel demineralization more than either fluoride treatment or laser treatment alone.