Effects of dentifrices differing in fluoride compounds on artificial enamel caries lesions in vitro

The aim of this study was to compare the caries-preventive effect of a stabilized stannous fluoride/sodium fluoride dentifrice containing sodium hexametaphosphate with those of a regular, solely sodium fluoride-containing and amine fluoride-containing dentifrice on pre-demineralized bovine enamel specimens using a pH-cycling model. Bovine enamel specimens with two artificial lesions each were prepared. Baseline mineral loss of both lesions was analyzed using transversal microradiography (TMR). Eighty-five specimens with a mean (SD) baseline mineral loss of 3393 (683) vol% × µm were selected and randomly allocated to five groups (n = 13/15). Treatments during pH-cycling (28 days and 2 × 20 min demineralization/day) were: brushing twice daily with slurries of AmF (1400 ppm F^?), NaF (1450 ppm F^?), SnF₂/NaF (1100 ppm F^?/350 ppm F^?), and fluoride-free (FF) dentifrices or they were immersed in distilled water and remained unbrushed (NB). Subsequently, from each specimen one lesion was covered with acid-resistant varnish, while the remaining lesion was demineralized for another 14 days. Differences in integrated mineral loss (??Z) were calculated between values before and after pH-cycling (??Z _E1) as well as before pH-cycling and after second demineralization (??Z _E2) using TMR. Treatments AmF and NaF induced a significantly higher mineral gain (??Z _E1/??Z _E2) compared to treatments FF and NB (p < 0.05; ANOVA test). Except for treatments AmF and NaF no significant differences in mineral loss between before and after pH-cycling could be observed (p < 0.05; t test) [??Z _E1: AmF:1563 (767); NaF:1222 (1246); SnF₂/NaF:258 (1259); FF:?52 (1223); NB:?151 (834)]. Both dentifrices with either AmF or NaF promoted remineralization, whereas SnF₂/NaF dentifrice did not promote remineralization in a biofilm-free pH-cycling model.     

Efficacy of the stannous ion and a biopolymer in toothpastes on enamel erosion/abrasion

Objectives

Sn²⁺ has promising erosion-inhibiting properties in solutions, but little is known about respective effects in toothpastes. In addition, biopolymers might have protecting potential. Aim of this study was to investigate the effects of Sn²⁺ in toothpastes and of a biopolymer (chitosan) added to a Sn²⁺ formulation on erosion/abrasion.

Methods

Enamel samples were subjected to cyclic erosion procedures (10 days; 0.50% citric acid, pH 2.5; 6× 2 min/day), and brushing (2× 15 s/day, load 200 g) during immersion in slurries (2 min). The toothpastes were NaF formulations (NaF/1, NaF/2, NaF/3) and Sn²⁺ formulations (NaF/SnCl₂, AmF/SnF₂, AmF/NaF/SnCl₂) and AmF/NaF/SnCl₂ + 0.5% chitosan.Declared concentrations of active ingredients in toothpastes were 1400–1450 μg/g F⁻ and 3280–3500 μg/g Sn²⁺. Negative controls were erosion only and placebo, positive control was a SnF₂ gel. Tissue loss was quantified profilometrically, Sn on enamel surfaces was measured by energy dispersive X-ray spectroscopy.

Results

Loss values (μm) for erosion only and placebo were 14.4 ± 4.5 and 20.2 ± 3.8, respectively, and 4.6 ± 1.9 for the positive control (p ≤ 0.001 each compared to erosion only). The other loss values were: NaF/1 16.5 ± 3.0, NaF/2 14.0 ± 2.7, NaF/3 12.6 ± 3.9, NaF/SnCl₂ 14.7 ± 5.1, AmF/SnF₂ 13.5 ± 4.8, AmF/NaF/SnCl₂ 12.4 ± 4.2, AmF/NaF/SnCl₂ + chitosan 6.6 ± 3.5 (except NaF/1 all p ≤ 0.01 compared to placebo). AmF/NaF/SnCl₂/chitosan was more effective than all other toothpastes (p ≤ 0.01 each). Sn on the enamel surface ranged between 1.3 ± 0.3 and 2.8 ± 0.04 wt.% with no obvious relationship with efficacy.

Conclusions

The NaF and Sn²⁺ toothpastes without chitosan exhibited similar anti-erosion and abrasion-prevention effects. The experimental Sn²⁺ formulation with chitosan revealed promising results similar to those of the positive control.

Clinical significance

NaF toothpastes offer a degree of protection against erosion/abrasion, which is likely sufficient for most subjects with average acid exposures. For patients with initial erosive lesions, however, more effective toothpaste is desirable. The combination of Sn²⁺ and a biopolymer appears promising in this context.     

Application of a direct pulp capping cement containing S-PRG filler

Objectives

To evaluate new pulp capping cements containing surface pre-reacted glass ionomer (S-PRG) filler and to investigate ion release kinetics and pH shift of eluates from the cement.

Materials and methods

Molars of Wistar rats were directly pulp capped using three kinds of cement containing S-PRG filler and mineral tri-oxide aggregate (MTA) was used as a control. After 1, 2, or 4 weeks, histological evaluation was performed and differences of tertiary dentin formation were analyzed. Release of Sr²⁺, BO₃³⁻, SiO₃²⁻, Na⁺, and Al³⁺ ions was determined by inductively coupled plasma-atomic emission spectrometry, and F⁻ ion release was measured using a fluoride ion selective electrode. The pH of the eluate from each cement after mixing was measured with a pH electrode.

Results

One of S-PRG cements promoted tertiary dentin formation to the same extent as the control (p > 0.05) and it showed a tendency of less inflammatory response. This cement released more BO₃³⁻ and SiO₃²⁻, but less Sr²⁺, Na⁺, and F⁻ than other S-PRG specimens. Each cement recovered nearly neutral compared with glass ionomer cement.

Conclusions

S-PRG cement induced tertiary dentin formation based on multiple ion releases, suggesting that it is suitable as a pulp capping material.

Clinical relevance

This new material can be an alternative pulp capping agent to MTA.

     

Bleaching of simulated stained-remineralized caries lesions in vitro

Objective

Non-invasive esthetic treatment options for stained arrested caries lesions have not been explored. This study aimed to develop laboratory models to create stained-remineralized caries-like lesions (s-RCLs) and to test the efficacy of bleaching on their esthetic treatment.

Materials and methods

One hundred twelve enamel/dentin specimens were prepared from human molars, embedded, and had their color measured spectrophotometrically at baseline and after demineralization. They were randomly divided into four groups (n = 14) based on the staining/remineralization protocols for a total of 5 days: G1, no staining/no remineralization; G2, no staining/remineralization in artificial saliva (AS); G3, non-metallic staining/remineralization with sodium fluoride/AS; and G4, metallic staining/remineralization with silver diamine fluoride/AS. The lesion mineral loss (ΔZ) and depth (L) were measured using transverse microradiography along with color change (ΔE). Specimens were bleached and color was re-evaluated. Data were analyzed using ANOVA models followed by Fisher’s PLSD tests (α = 0.05).

Results

s-RCLs in G4 were significantly (p < 0.001) darker than G3, G2, and G1 regardless of substrate type and condition. s-RCLs in G2, G3, and G4 showed significantly lower ΔZ and L than G1 (all p < 0.001), confirming occurrence of remineralization. G4 exhibited significantly lower ΔZ and L compared to G2 (p < 0.001). Bleaching was more effective in non-metallic than in metallic stained lesions regardless of substrate type (p < 0.001).

Conclusion

The proposed models created distinct s-RCLs. Non-metallic s-RCLs were lighter and more responsive to bleaching compared to metallic s-RCLs.

Clinical relevance

The developed experimental models allow the further investigation of the efficacy and safety of different clinical strategies for the esthetic management of s-RCLs.

     

Effect of fluoride toothpaste with nano-sized trimetaphosphate on enamel demineralization: An in vitro study

ObjectiveThis study evaluated the effect of toothpastes containing 1100 ppm F associated or not with micrometric or nano-sized sodium trimetaphosphate (TMP) on enamel demineralization in vitro, using a pH cycling model.DesignBovine enamel blocks (4 mm × 4 mm, n = 96) were randomly allocated into eight groups (n = 12), according to the test toothpastes: Placebo (without fluoride or TMP); 1100 ppm F (1100F); 1100F plus micrometric TMP at concentrations of 1%, 3% or 6%; and 1100F plus nanosized TMP at 1%, 3% or 6%. Blocks were treated 2×/day with slurries of toothpastes and submitted to a pH cycling regimen for five days. Next, final surface hardness (SHf), integrated hardness loss (IHL), differential profile of integrated hardness loss (ΔIHL) and enamel fluoride (F) concentrations were determined. Data were analyzed by ANOVA and Student-Newman-Keuls’ test (p < 0.05).ResultsThe use of 1100F/3%TMPnano led to SHf 30% higher (p < 0.001) and IHL ∼ 80% lower (p < 0.001) when compared to 1100F. This toothpaste also resulted in ∼64% reduction of mineral loss (ΔIHL) when compared to 1100F. Moreover, the addition of nano-sized TMP promoted increases in enamel F uptake of 90%, 160% and 100%, respectively for the concentrations of 1%, 3% and 6%, when compared to 1100F (p < 0.001).ConclusionThe addition of nano-sized TMP at 3% to a conventional toothpaste significantly decreased enamel demineralization when compared to its counterparts without TMP or supplemented with micrometric TMP.     

Fluoride toothpastes containing micrometric or nano-sized sodium trimetaphosphate reduce enamel erosion in vitro

Objective: To evaluate the effect of fluoride toothpastes supplemented with micrometric or nano-sized sodium trimetaphosphate (TMP or TMPnano, respectively) on enamel erosion in vitro, as well as the influence of salivary acquired pellicle and saliva.

Material and methods: Bovine enamel blocks (n?=?120) were randomly assigned into the following experimental toothpastes: no F/TMP/TMPnano (Placebo); 1100?ppm F (1100?ppm F); 1100?ppm F plus 3% TMP or 3% TMPnano (1100 TMP or 1100 TMPnano, respectively) and 5000?ppm F (5000?ppm F). Erosive challenge was performed by immersion of the blocks in citric acid for 5?min, followed by 2?h immersion in human or artificial saliva, 4×/day, during 5 days. After each erosive challenge, blocks were exposed to slurries of the toothpastes. Enamel erosion (µm), surface hardness (SHf) and cross-sectional hardness (ΔKHN) were analyzed as response variables and the data were submitted to two-way ANOVA, followed by the Student–Newman–Keuls test (p?Results: 1100 TMPnano significantly reduced enamel loss when compared to 1100 TMP (p?=?.002), reaching values similar to those promoted by 5000?ppm F (p?=?.96). 1100?ppm F presented significantly lower enamel loss than Placebo (p?p?p?Conclusion: The addition of 3% TMPnano to 1100?ppm F toothpastes significantly increases the protective effect against enamel erosion in vitro when compared with its counterparts with micrometric TMP or without TMP. This effect was not influenced by the presence of acquired enamel pellicle and saliva.     

Anticaries effect of toothpaste with nano-sized sodium hexametaphosphate

Objective

To evaluate the effect of a fluoride toothpaste containing nano-sized sodium hexametaphosphate (HMPnano) on enamel demineralization on the biochemical composition and insoluble extracellular polysaccharide (EPS) in biofilm formed in situ.

Methods

This crossover double-blind study consisted of four phases (7 days each), in which 12 volunteers wore intraoral appliances containing four enamel bovine blocks. The cariogenic challenge was performed using 30% sucrose solution (6×/day). Blocks were treated 3×/day with the following toothpastes: no F/HMP/HMPnano (Placebo), conventional fluoride toothpaste, 1100 ppm F (1100F), 1100F + 0.5% micrometric HMP (1100F/HMP), and 1100F + 0.5% nano-sized HMP (1100F/HMPnano). The percentage of surface hardness loss (%SH), integrated loss of subsurface hardness (ΔKHN), and enamel calcium (Ca), phosphorus (P), and fluoride (F) were determined. Moreover, biofilms formed on the blocks were analyzed for F, Ca, P, and insoluble extracellular polysaccharide (EPS) concentrations. Data were analyzed using one-way ANOVA, followed by Student–Newman–Keuls’ test (p < 0.001).

Results

1100F/HMPnano promoted the lowest %SH and ΔKHN among all groups (p < 0.001). The addition of HMPnano to 1100F significantly increased Ca concentrations (p < 0.001). The 1100F/HMPnano promoted lower values of EPS when compared with 1100F (~ 70%) (p < 0.001) and higher values of fluoride and calcium in the biofilms (p < 0.001).

Conclusion

1100F/HMPnano demonstrated a greater protective effect against enamel demineralization and on the composition of biofilm in situ when compared to 1100F toothpaste.

Clinical relevance

This toothpaste could be a viable alternative to patients at high risk of caries.

     

Indirect caries‐preventive effect of silver diamine fluoride on adjacent dental substrate: A single‐section demineralization study

This study assessed the indirect effect of 38% silver diamine fluoride (SDF) on demineralization of adjacent untreated sound and pre‐demineralized enamel and dentine using a single‐section model for digital transverse microradiography (TMR‐D). Forty‐eight bovine dentine single sections were demineralized, stratified (n = 12) according to integrated mineral loss (ΔZ), and treated with SDF or deionized water (DIW). Each “treated dentine” section was attached between untreated sound and pre‐demineralized enamel or dentine and then subjected to demineralization. ΔZ and lesion depths (LD) of all specimens at baseline, 24 and 48 h demineralization, and after treatment of “treated dentine” were quantified using TMR‐D. Fluoride in the demineralization solution of SDF clusters was determined using an ion‐selective electrode. ΔZ and LD of sound and ΔZ of pre‐demineralized enamel adjacent to SDF‐treated dentine did not increase over time. All untreated dentine demineralized significantly; however, ΔZ of sound dentine adjacent to SDF‐treated specimen was still significantly lower than control. SDF‐treated dentine remineralized and released fluoride even after 48 h. Consistent with clinical findings, when applied only to demineralized teeth in this chemical model, 38% SDF completely inhibited demineralization in adjacent untreated sound enamel. Demineralization prevention was observed to a lesser extent in adjacent pre‐demineralized enamel but not in dentine.     

Effects of regular and highly fluoridated toothpastes in combination with saliva substitutes on artificial enamel caries lesions differing in mineral content

ObjectiveFor patients with hyposalivation fluorides are supportive to prevent caries lesions. Remineralization of subsurface lesions might be improved by toothpastes containing 5000 μg F^?/g compared with those having 1400 μg F^?/g. This could be influenced by the degree of baseline mineralization. Therefore, this in vitro study evaluated the effects of fluoride toothpastes differing in fluoride concentration in combination with de- and remineralizing saliva substitutes using two lesion types.DesignSpecimens with shallow (SL; ΔZ (SD): 1915 (543) vol% × μm) or deep lesions (DL; 5804 (427) vol% × μm) were either stored in mineral water [saturation with respect to octacalcium phosphate (S_OCP): 0.5], demineralizing experimental (Exp, S_OCP: 0.3), demineralizing commercial (Glandosane, S_OCP: 0.3), or remineralizing saliva substitute (modified Saliva natura; S_OCP: 1.9) for five weeks (37 °C). Either one of three brushing procedures was performed additionally three times daily: no brushing, Elmex anticaries toothpaste (E; 1400 μg F^?/g), Duraphat toothpaste (D; 5000 μg F^?/g). Mineral parameters before and after storage were evaluated using microradiographs.ResultsStorage in Exp as well as Glandosane induced a significant demineralization (p < 0.05; relatively more pronounced in SL than DL). Additional brushing in particular with D reduced these effects. Storage alone in modified Saliva natura remineralized specimens (p < 0.05).ConclusionsUnder the in vitro conditions chosen shallow lesions seem to be more susceptible for demineralization compared with deeper ones when stored in an undersaturated (with respect to OCP) saliva substitute. The highly fluoridated toothpaste seemed to be more beneficial than a regular one.     

Glass hybrid,but not calcium hydroxide,remineralized artificial residual caries lesions in vitro

Objectives

For deep carious lesions, less invasive carious tissue removal is recommended. The resulting residual carious lesions might benefit from remineralization by lining or restoration materials. We aimed to compare mineral gains in artificial residual lesions provided by calcium hydroxide and glass hybrid materials in combination with pulpal fluid simulation.

Methods

On the coronal aspect of human dentin discs (n = 20), artificial carious lesions were induced using acetic acid. Median mineral loss ΔZ [25th/75th percentiles] of resulting lesions was 1643 [1301/1858] vol% μm. One third of each disc served as baseline sample. The remaining disc was divided into four groups, each being covered with one experimental material (n = 20/group): flowable composite (control (CO)), setting or non-setting calcium hydroxide liner plus flowable composite (CH-S, CH-NS), and glass hybrid (GH). Samples were mounted in a dual-chamber device. Pulpal surfaces were exposed to simulated pulpal fluid at 2.94 kPa. Coronal surfaces were exposed to artificial saliva and rinsed with 200 ppm NaF every 2 weeks. After 12 weeks, mineral loss differences (ΔΔZ) were assessed using transverse microradiography. Electron probe microscopic analysis was used to measure fluoride and strontium concentrations.

Results

Mineral gains were not significantly different between CO (ΔΔZ = 372 [115/501] vol% μm), CH-S (ΔΔZ = 317 [229/919] vol% μm), or CH-NS (ΔΔZ = 292 [130/579] vol% μm; p > 0.05/Wilcoxon test) but significantly increased in GH (ΔΔZ = 1044 [751/1264] vol% μm, p < 0.001). Samples in GH showed fluoride and strontium enrichment deep into the dentin. Such enrichment was not found in CO.

Conclusions

Within the limitations of this study, GH, but not calcium hydroxide, provided coronal remineralization of residual carious lesions.

Clinical relevance

Glass hybrids might provide additional remineralization of residual carious lesions. The functional implications of this mineral gain need to be evaluated.

     

Reflectance and color prediction of dental material monolithic samples with varying thickness

ObjectiveTo assess accuracy of reflectance reconstruction and color estimation of different dental materials with varying thicknesses using Principal Component Analysis (PCA).MethodA1, A2, A3, A3.5, B2, C2 and D2 shades and 5 thicknesses (within 0.5–2.5 mm range) of Vita Suprinity (VS-PC) and Vitapan Dentine (VD), were used. Reflectance measurements were performed over black background using a non-contact spectroradiometer with CIE 45^°∕0^° geometry. A PCA based algorithm was proposed to reconstruct spectral data and color of samples, using both extrapolation and interpolation approaches. Root Mean Square Error (RMSE), Goodness of Fit (GFC), correlation coefficient (R²) as well as ΔE₀₀ with corresponding 50:50% acceptability and perceptibly thresholds (AT and PT) were used as performance assessment.ResultsThe interpolation approach provided an average RMSE = 0.01 and GFC > 0.999 when comparing predicted and measured spectral reflectances for both materials, while for the extrapolation approach RMSE = 0.02 and GFC > 0.999. Interpolation approach also resulted in lower overall mean color difference ΔE₀₀ = 0.8 (ΔE₀₀ = 0.9 for VS-PC and ΔE₀₀ = 0.7 for VD), while using extrapolation approach resulted in higher overall mean color difference ΔE₀₀ = 1.6, although below the AT (ΔE₀₀ = 1.8 for VS-PC and ΔE₀₀ = 1.5 for VD). Correlation values between predicted and measured spectral reflectances of R² = 0.987 and R² = 0.993 were globally obtained for VS-PC and VD, respectively.SignificanceThe proposed PCA-based algorithm is able to efficiently predict reflectance spectrum and color of monolithic samples of different dental materials with varying thickness. It can be used to optimize dental materials manufacturing processes and to improve chromatic accuracy of clinical dental restorations.     

In vitro dentine remineralization with a potential salivary phosphoprotein homologue

ObjectiveAdvantages of introducing a salivary phosphoprotein homologue under standardized in vitro conditions to simulate the mineral-stabilizing properties of saliva have been proposed. This study longitudinally investigates the effects of casein, incorporated as a potential salivary phosphoprotein homologue in artificial saliva (AS) solutions with/without fluoride (F) on in vitro dentine lesion remineralization.DesignThin sections of bovine root dentine were demineralized and allocated randomly into 6 groups (n = 18) having equivalent mineral loss (ΔZ) after transverse microradiography (TMR). The specimens were remineralized using AS solutions containing casein 0 μg/ml, F 0 ppm (C₀–F₀); casein 0 μg/ml, F 1 ppm (C₀–F₁); casein 10 μg/ml, F 0 ppm (C₁₀–F₀); casein 10 μg/ml, F 1 ppm (C₁₀–F₁); casein 100 μg/ml, F 0 ppm (C₁₀₀–F₀) or casein 100 μg/ml, F 1 ppm (C₁₀₀–F₁) for 28 days with TMR taken every 7 days.ResultsSurface mineral precipitation, evident in group C₀–F_1, was apparently inhibited in groups with casein incorporation. Repeated measures ANOVA with Bonferroni correction revealed higher ΔZ for non-F and non-casein groups than for their counterparts (p < 0.001). Subsequent multiple comparisons showed that mineral gain was higher (p < 0.001) with 10 μg/ml casein than with 100 μg/ml when F was present in the earlier stages of remineralization, with both groups achieving almost complete remineralization after 28 days.ConclusionCasein is a potential salivary phosphoprotein homologue that could be employed for in vitro dentine remineralization studies. Concentration related effects may be clinically significant and thus must be further examined.     

The effect of temperature and ionic solutes on the fluoride release and recharge of glass-ionomer cements

ObjectiveTo determine the effect of storage temperature and the presence of sodium chloride in solution on the fluoride uptake and release of glass-ionomer cements.MethodsSeveral commercial brands were used, and stored at either room temperature (21–23 °C) or 37 °C, in KF solution at a concentration of 1000 ppm F⁻ with and without 0.9% NaCl present. Fluoride levels in the storage solutions after 24 h were measured using a fluoride-ion selective electrode. Specimens were then stored in water, and fluoride release after 24 h was determined. Studies were also carried out to determine chloride levels when specimens were stored in 0.9% NaCl, with or without 1000 ppm fluoride, again using an ion selective electrode.ResultsAll glass-ionomer specimens took up fluoride, and most of the fluoride was retained over the next 24 h when the specimens were stored in water. There was a slight variation in the amount of fluoride taken up with storage temperature and with the presence of sodium chloride. All specimens also took up chloride, with greater uptake at higher temperatures, but little or no effect when KF was also present in solution.SignificanceThe substantial retention of fluoride after 24 h in deionised water confirms previous findings and suggests that an insoluble species, possibly SrF₂, forms in situ. Chloride uptake has not been reported previously, and its significance requires further investigation. Fluoride and chloride uptake were apparently independent of each other, which suggests that the ions are taken up at different sites in the cement. This may relate to differences in the respective sizes and hydration states of F⁻ and Cl⁻ ions.     

Physical chemical effects of zinc on in vitro enamel demineralization

Objectives

Zinc salts are formulated into oral health products as antibacterial agents, yet their interaction with enamel is not clearly understood. The aim was to investigate the effect of zinc concentration [Zn²⁺] on the in vitro demineralization of enamel during exposure to caries-simulating conditions. Furthermore, the possible mechanism of zinc's action for reducing demineralization was determined.

Methods

Enamel blocks and synthetic hydroxyapatite (HAp) were demineralized in a range of zinc-containing acidic solutions (0–3565 ppm [Zn²⁺]) at pH 4.0 and 37 °C. Inductively coupled-plasma optical emission spectroscopy (ICP-OES) was used to measure ion release into solution. Enamel blocks were analysed by Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), and HAp by X-ray diffraction (XRD) and neutron diffraction (ND).

Results

ICP-OES analysis of the acidic solutions showed a decrease in [Ca²⁺] and [PO₄³⁻] release with increasing [Zn²⁺]. FTIR revealed a α-hopeite (α-Zn₃(PO₄)₂.4H₂O)-like phase on the enamel surfaces at >107 ppm [Zn²⁺]. XRD and ND analysis confirmed a zinc-phosphate phase present alongside the HAp.

Conclusions

This study confirms that zinc reduces enamel demineralization. Under the conditions studied, zinc acts predominantly on enamel surfaces at PO₄³⁻ sites in the HAp lattice to possibly form an α-hopeite-like phase.

Clinical significance

These results have a significant implication on the understanding of the fundamental chemistry of zinc in toothpastes and demonstrate its therapeutic potential in preventing tooth mineral loss.     

In vitro evaluation of fluoride and calcium sodium phosphosilicate toothpastes, on root dentine caries lesions

Objectives

The aim of this in vitro study was to assess the effect of toothpastes containing three different sodium fluoride concentrations and a calcium sodium phosphosilicate system, on root dentine demineralization and remineralization.

Methods

During a fourteen-day pH-cycling protocol, pre-softened bovine root dentine specimens were immersed twice daily, before and after the demineralization periods, for 2 min, in the following toothpaste slurries: (a) non-fluoridated (control), (b) 7.5% calcium sodium phosphosilicate, (c) 1450 ppm F, (d) 2800 ppm F, and (e) 5000 ppm F. Subsequently, the slabs were subjected to a fifty-hour acid resistance test. Knoop microhardness at different lesion depths was assessed in specimen cross-sections and KHN values were converted to vol.% mineral. Comparisons between the groups were performed at each lesion depth through ANOVA-based tests and furthermore, regression analysis of the derived statistic of “integrated vol.% mineral loss” was carried out. Also, lesions were evaluated qualitatively using transmission and polarized light microscopy.

Results

The 5000 ppm F toothpaste group, during pH-cycling, presented significantly less total vol.% mineral loss and subsequently exhibited considerably increased surface acid resistance, compared to all the other tested groups. The calcium sodium phosphosilicate toothpaste, during pH-cycling, inhibited demineralization and/or promoted remineralization of the surface layers significantly more effectively than the control group nevertheless, subsequently, the acid resistance of the calcium sodium phosphosilicate dentifrice group was similar to that of the control group. These observations were confirmed by microscopic examination of the lesions.

Conclusions

Under the present experimental conditions, the 5000 ppm F toothpaste, promoted remineralization and inhibited demineralization more effectively, than the other tested toothpastes.     

Effect of the addition of nano-sized sodium hexametaphosphate to fluoride toothpastes on tooth demineralization: an in vitro study

Clinical Oral Investigations - This study evaluated the effect of toothpastes containing 1100&nbsp;ppm F associated with nano-sized sodium hexametaphosphate (HMPnano) on enamel demineralization...     

Impact of combined CO2 laser irradiation and fluoride on enamel and dentin biofilm-induced mineral loss

Objectives

The caries-protective effects of CO₂ laser irradiation on dental enamel have been demonstrated using chemical demineralization models. We compared the effect of CO₂ laser irradiation, sodium fluoride, or both on biofilm-induced mineral loss (∆Z) and Streptococcus mutans adhesion to enamel and dentin in vitro.

Materials and methods

Ground, polished bovine enamel, and dentin samples were allocated to four groups (n = 12/group): no treatment (C); single 22,600-ppm fluoride (F) varnish (5 % NaF) application; single CO₂ laser treatment (L) with short pulses (5 μs/λ = 10.6 μm); and laser and subsequent fluoride treatment (LF). Samples were sterilized and submitted to an automated mono-species S. mutans biofilm model. Brain heart infusion plus 5 % sucrose medium was provided eight times daily, followed by rinses with artificial saliva. After 10 days, bacterial numbers in biofilms were enumerated as colony-forming units/ml (CFU/ml) (n = 7/group). ∆Z was assessed using transversal microradiography (n = 12/group). Univariate ANOVA with post hoc Tukey honestly-significant-difference test was used for statistical analysis.

Results

Bacterial numbers were significantly higher on dentin than enamel (p < 0.01/ANOVA). On dentin, LF yielded significantly lower CFUs than other groups (p = 0.03/Tukey), while no differences between groups were found for enamel. The lowest ∆Z in enamel was observed for L (mean/SD 2036/1353 vol%×μm), which was not only significantly lower than C (9642/2452 vol%×μm) and F (7713/1489 vol%×μm) (p < 0.05) but also not significantly different from LF (3135/2628 vol%×μm) (p > 0.05). In dentin, only LF (163/227) significantly reduced ∆Z (p < 0.05).

Conclusion/clinical relevance

CO₂ laser irradiation did not increase adhesion of S. mutans in vitro. Laser treatment alone protected enamel against biofilm-induced demineralization, while a combined laser-fluoride application was required to protect dentin.

     

Total and soluble fluoride content in commercial dentifrices in Chile

Abstract

Objective. Regardless of the total amount of fluoride (F) in a dentifrice, only the soluble fraction presents anti-caries activity and its concentration must be above 1000 ppm. No information regarding the quality of F in Chilean toothpastes is available. The aim of this study, therefore, was to determine the F concentration present in commercially-available toothpastes in Chile. Materials and methods: Eighteen toothpastes of five different brands were tested, each purchased from three different chain drugstores in Chile. For each toothpaste, total, total soluble and ionic F concentrations were assessed and expressed as ppm of F (μg F/g). Results. Among the dentifrices evaluated, 77.8% contained NaF (sodium fluoride), 16.7% MFP (monofluorphosphate) and 5.6% both types of F salts; 77.2% of the dentifrices showed similar total F content to that declared by the manufacturer in the labeling with only five with lower concentration than expected, beyond a 5% disagreement tolerance range. Total soluble F ranged from 958.8–1496.3 ppm (mean ± SD: 1270.5 ± 183.7). Five toothpastes showed lower total soluble F than total F. Only one toothpaste showed soluble salt levels below the recommended dose for this type of dentifrice. Conclusion: Most Chilean dentifrices evaluated contained soluble F within the range of 1000–1500 ppm and, therefore, may have anti-caries activity.     

Observations on the Life Cycle of the Gingival Epithelial Cells of Mice as Revealed by Autoradiography

Abstract

Objective. This study tested the hypothesis that the benefit of fluoride-releasing restorative materials continues even after their reserve of fluoride has been depleted. Materials and methods. Pits in perspex blocks simulating cavities were filled with either a fluoride-releasing or a non-fluoride-releasing restorative material and a dentin single-section was placed 1 mm from the edge of the filled pit. These combinations were exposed to an acid gel system. Each demineralized dentin section was separated from the adjacent material and immersed in fresh demineralizing solutions. Transversal microradiographs were taken following the two experimental periods. This study defined ΔΔZ as the increase of integrated mineral loss (ΔZ) during the second acid attack. Results. The first acid attack substantially demineralized the near-surface region (depth < 40 μm) in all samples. The second acid attack, however, did not cause further demineralization in this near-surface region. Instead, it demineralized dentin deeper than 40–60 μm. The ΔΔZ of the material that did not release fluoride was significantly greater than that of fluoride-releasing materials. Negative correlations were found between ΔΔZ and the mineral volume% of the near-surface region and lesion body of the initial lesions. These results indicate that the dentin mineral in the near-surface region is chemically altered to become acid-resistant fluorapatite. In addition, lesion progression during the second period of demineralization, which was fluoride-free, may have been affected for the materials that have high mineral content of the surface layer and lesion body. Conclusions. It is concluded that dentin surrounding fluoride-releasing materials is protected against demineralization even after the fluoride release has diminished.     

Effect of sodium fluoride on oral biofilm microbiota and enamel demineralization

ObjectiveFluoride is widely used as an anti-caries agent, e.g. in toothpastes and mouth rinses. However, the nature of the anti-caries action is not entirely clear. Mechanisms suspected to explain the cariostatic effect include inhibitory effects on acid formation by bacteria, inhibition of extracellular polysaccharide (EPS) production, inhibition of enamel demineralization and enhancement of remineralizaton or combination thereof. The aim of this study was to examine with the supragingival Zurich in vitro biofilm model the effect of fluoride in NaF formulation, on the microbiota and on demineralization.MethodsBiofilms consisting of Actinomyces oris, Candida albicans, Fusobacterium nucleatum, Streptococcus oralis, Veillonella dispar and Streptococcus sobrinus, were grown anaerobically on sintered hydroxyapatite or bovine enamel disks, exposed to 200, 400, and 1400 ppm of NaF, or 0.1% chlorhexidine (positive control). The biofilms were harvested after 64 h and CFUs were assessed for total bacteria. Demineralization of enamel disks was measured by quantitative light-induced fluorescence.ResultsNaF did not affect the bacterial numbers. No enamel mineral loss was observed at 1400 and 400 ppm of fluoride, whereas the pH of the surrounding medium was increased to 5.5 and 5.0, respectively, compared to the untreated control (pH 4.5 and mineral loss ΔF of −32%). At 1400 ppm NaF the biofilm’s EPS volume was also significantly reduced.ConclusionsAdministration of NaF completely prevented demineralization without affecting biofilm composition and growth. This protective effect may be attributed to the observed decrease in acid production or EPS volume, or to a shift in the de/remineralization balance.