In situ effect of a dentifrice with low fluoride concentration and low pH on enamel remineralization and fluoride uptake

Effect of dentifrices with different pH and fluoride concentrations on fluoride levels in biofilm and nails: an RCT

PURPOSE

to evaluate the effect of dentifrice pH and fluoride concentration ([F]) on fluoride uptake on the biofilm and nails of children from a non-fluoridated area.

METHODS

two hundred and twenty-eight two- to four-year-old children were randomly allocated into 3 groups according to the type of dentifrice: G1: 1100 μg F/g, pH 4.5 (n = 76); G2: 750 μg F/g, pH 4.5 (n = 74); and G3: 1100 μg F/g, pH 7.0 (n = 78). Nails were collected at 4, 8, and 12 months after starting dentifrice use and biofilm was collected 5 and 60 minutes after toothbrushing. The concentrations of F in nails and biofilm were analyzed by HMDS facilitated diffusion. Data were analyzed by Kruskal-Wallis/Mann-Whitney's test and the comparison between biofilm collection times was done using Wilcoxon test (p £ 0.05).

RESULTS

a significant reduction of [F] in biofilm was observed 60 minutes after toothbrushing, regardless of the dentifrice used. However, 5 minutes after toothbrushing, G1 had a significantly higher [F] compared to G2 and G3, and 60 minutes after toothbrushing, [F] was significantly higher for G1 and G2 compared to G3. G1 and G3 had significantly higher [F] in the nails compared to G2.

CONCLUSION

a lower dentifrice concentration is a relevant factor for the reduction of excessive fluoride intake. The use of a low-F acidified dentifrice combines the reduction of fluoride uptake with caries prevention by leading to greater incorporation of F into the biofilm over time.

Randomised in situ clinical trial investigating self-assembling peptide matrix P11-4 in the prevention of artificial caries lesions

The aim was to investigate the ability of self-assembling Peptide P11-4 Matrix (SAPM) to remineralize artificial initial caries lesions compared to the use of fluoride varnish. Volunteers were recruited for this randomised, cross-over in situ trial. Bovine specimens, half including orthodontic brackets, were recessed on the buccal aspects of mandibular appliances. Specimens included internal sound enamel control, a demineralised control and a part exposed during the in situ phase. Each phase lasted four weeks, followed by a one-week washout. Treatment groups were: A: negative control, no treatment,B: positive control, 22,600 ppm fluoride varnish,C: test group, 1,000 ppm SAPM. Laser fluorescence values (LF) were measured before/after demineralisation, and after the in situ period. Micro-CT analysis was used to assess mineral changes within the specimens after the in situ phase. In specimens without brackets, ΔLF values after in situ phase were: A: +5.28, B: +0.85, C: −2.89. Corresponding ΔLF for specimens with brackets were: A: +5.77, B: +1.30, C: −3.15. LF-values between groups significantly differed from each other (p < 0.0001) after the in situ phase. Micro-CT analysis yielded no significant difference among groups for specimens without brackets. For specimens with brackets, the test group showed significantly more remineralisation than the negative (p = 0.01) and positive control (p = 0.003). Within the limitations of the study, SAPM showed prevention of caries and remineralisation of enamel around orthodontic brackets.

Effect of dentifrice of varying fluoride concentration on surface microhardness of fluorosed enamel: an in vitro study

AIM

To evaluate the effect of dentifrice with varying concentrations of fluoride on surface microhardness of fluorosed enamel as compared to a non-fluoridated dentifrice.

STUDY DESIGN

In vitro, comparative type.

METHOD

60 enamel blocks with score-3 enamel fluorosis were randomly divided into three groups: Group I non-fluoridated dentifrice, Group II 1000-ppm fluoridated dentifrice and Group III 1400-ppm fluoridated dentifrice. After evaluating the baseline surface microhardness, samples from each group were brushed for 2 min, twice daily for a period of 21 days with 0.02 g of respective interventional agents as per protocol. Microhardness of the samples was re-evaluated at the end of 21 days. Statistical analysis was performed using paired t test, ANOVA and Kruskal-Wallis test.

RESULTS

The surface microhardness within the group from the baseline to 21st day post intervention, showed a statistically significant increase in all three groups, hence indicating that all the three interventional agents used were effective against the fluorosed enamel surface. Intergroup comparison of the surface microhardness of fluorosed enamel from baseline to 21st day post intervention showed a statistically significant difference (p < 0.001) amongst the groups with Group III proving most effective followed by Group I and Group II.

CONCLUSION

1400-ppm fluoridated dentifrice is more effective as compared to 1000-ppm fluoridated dentifrice and non-fluoridated dentifrice in increasing the surface microhardness of fluorosed enamel.

Effect of dentifrices on their remineralizing potential in artificial carious lesions: An in situ study

Background:

The eventual sequel of dental caries is determined by the dynamic equilibrium between pathological factors which lead to demineralization and protective elements, which in turn leads to remineralization. Remineralization is the natural process for noncavitated demineralized lesions and relies on calcium and phosphate ions assisted by fluoride to rebuild a new surface on existing crystal remnants in subsurface lesions remaining after demineralization. Hence, the present study was designed to evaluate the efficacy of fluoride dentifrices in remineralizing artificial caries-like lesions in situ.

Materials and Methods:

A double-blind, randomized study with an initial washout period of 7 days was carried out for 3 weeks. Twenty volunteers were enrolled, who wore the intraoral cariogenicity test appliance having enamel slabs incorporated into them, for 3 weeks. 10 participants were instructed to use Group A dentifrice (fluoride) and the other 10 Group B dentifrice (nonfluoride) for brushing their teeth. The enamel slabs were analyzed by surface microhardness testing and scanning electron microscopy (SEM) at 3 intervals.

Results:

No significant differences was seen in the microhardness values recorded for Group A and Group B at baseline and after demineralization (P > 0.05); however Group B exhibited lesser microhardness compared to Group A, after intra-oral exposure (P < 0.05). In the SEM analysis, the Group A enamel surfaces had more regular and longer crystallites to those of the Group B.

Conclusion:

Fluoride dentifrices avert the decrease in enamel hardness and loss of minerals from the enamel surface to a large extent as compared to the nonfluoride dentifrices.

Development of caries adjacent to composite restorations after exposure to dentifrices with different fluoride concentrations

Objective To evaluate the development of recurrent caries after exposure to fluoride dentifrices with different concentrations. Material and method: 48 samples of bovine incisors (4x4mm2) were exposed to pH cycling for 7 days before the preparation of the cavities (2mm deep). The samples were restored with a microhybrid resin composite. Then, the samples were exposed to thermal cycling (350 cycles) and they were randomly allocated into 4 treatment groups (n = 12): Group A - non-fluoridated dentifrice (negative control); Group B - 500 ppm dentifrice; Group C - 750 ppm dentifrice; group D - 1100 ppm dentifrice (positive control). The samples were treated with solutions of each dentifrice (9.6 ml water/1.6 g dentifrice) for 60 seconds and then were immersed in demineralizing (3 h) and remineralizing (2 h) solutions 3 times a day. Next, the samples were immersed in a remineralizing solution for 18 hours. Then, the blocks were sectioned for examination of the length of the outer caries lesion, using polarized light microscopy. The ANOVA parametric test complemented by the Tukey test with a confidence level of 95%, were used in the statistical analysis. Result: A smaller lesion length was observed in the group treated with the fluoride concentration of 1100 ppm F, but there were no differences between toothpastes with fluoride concentrations of 500 and 750 ppm F. Conclusion: The use of fluoride dentifrices (1100 ppm) reduces the development of caries adjacent to dental restorations.

Mechanisms of action of fluoridated acidic liquid dentifrices against dental caries

OBJECTIVE

This study attempted to clarify the mechanisms of action of fluoridated acidic liquid dentifrices against dental caries.

DESIGN

In the in vitro leg, enamel specimens were submitted to a pH-cycling model, treated with distinct dentifrices (0, 550 μgF/g pH 4.5 and pH 7.0, 1100 or 5000 μgF/g pH 7.0) and analyzed using hardness. Alkali-soluble fluoride (F) deposition was quantified on pre-demineralized specimens treated with the dentifrices. In the clinical leg, 2-to-4-year-old children who had been using liquid dentifrices for 6 months (550 μgF/g pH 4.5 or pH 7.0 or 1100 μgF/g pH 7.0) had their plaque samples collected 5 and 60 min after the last brushing. Fluoride uptake in whole plaque was evaluated.

RESULTS

The reduction of the pH had a partial preventive effect on subsurface hardness loss only. [F] had a significant influence on the deposition of fluoride, surface and subsurface hardness loss. In vivo, the reduction of the pH was able to significantly increase plaque F uptake, leading to similar levels as those found for the neutral dentifrice containing twice [F].

CONCLUSION

The results obtained from in vitro studies whose design does not include the presence of dental plaque should be interpreted with caution.

Enamel surface remineralization: Using synthetic nanohydroxyapatite

OBJECTIVE

The purpose of this study was to evaluate the effects of synthetically processed hydroxyapatite particles in remineralization of the early enamel lesions in comparison with 2% sodium fluoride.

MATERIALS AND METHODS

Thirty sound human premolars were divided into nanohydroxyapatite group (n = 15) and the sodium fluoride group (n = 15). The specimens were subjected to demineralization before being coated with 10% aqueous slurry of 20 nm nanohydroxyapatite or 2% sodium fluoride. The remineralizing efficacy of the materials was evaluated using surface microhardness (SMH) measurements, scanning microscopic analysis and analysis of the Ca/P ratio of the surface enamel. Data analysis was carried out using paired t-test and independent t-test.

RESULTS

The results showed that the nanohydroxyapatite group produced a surface morphology close to the biologic enamel, the increase in mineral content (Ca/P ratio) was more significant in the nanohydroxyapatite group (P < 0.05) and the SMH recovery was closer to the baseline level in the nanohydroxyapatite group (P < 0.05). Both the groups did not show any significant difference in thickness (P > 0.05).

CONCLUSION

The use of biomimetic nanohydroxyapatite as a remineralizing agent holds promise as a new synthetic enamel biocompatible material to repair early carious lesions.

pH-cycling models to evaluate the effect of low fluoride dentifrice on enamel de- and remineralization

Since the currently available pH-cycling models do not differentiate the anti-caries potential of dentifrices with low fluoride (F) concentration, two models were developed and tested in the present. Bovine enamel blocks were subjected to the models and treated with F solutions containing from 70 to 280 microg F/mL in order to validate them in terms of dose-response effect. The models were also tested by evaluating the dentifrices Colgate Baby (500 microg F/g, as a low fluoride dentifrice), Tandy (1,100 microg F/g, as an active F-dentifrice) and Crest (1,100 microg F/g, as positive control). Enamel mineral loss or gain was assessed by surface and cross-sectional microhardness, and lesion depth was analyzed by polarized light microscopy. The pH-cycling models showed F dose-response effect either reducing enamel demineralization or enhancing remineralization. The low F dentifrice presented anti-caries potential, but it was not equivalent to the dentifrices containing 1,100 microg F/g. These data suggest that the models developed in this study were able to evaluate the anti-caries potential of low F dentifrice either on resistance to demineralization or on enhancement of remineralization.