Reaction of silver diamine [corrected] fluoride with hydroxyapatite and protein

Silver diammine fluoride (SDF) is used as an anticaries agent; however, its mode of action is uncertain, whether chemical, physical, mechanical or antibacterial. As a preliminary study, the effect of SDF on hydroxyapatite (HAp) and gelatin (as a chemically-representative protein) was examined.

Methods

2.5 mg HAp powder specimens and 0.5 mL 10% gelatin (Riedel-de Haën) (initially as a sol at ∼37 °C), were mixed with 0.5 mL of 38% SDF (J. Morita), 4% NaF (Sigma) or 40% AgNO₃ (Sigma) and tumbled in 1.5 mL polypropylene tubes (Sarstedt) for 48 h at ∼23 °C, in two series: exposed to laboratory lighting, and kept dark at all times. The HAp specimens were separated by centrifugation and decanting, then these and one set of gelatin specimens were dried at 60 °C in situ; a second parallel set of gelatin specimens were dried at ∼23 °C. Each was washed with 1 mL deionized water for 1 min, 3 times. Treated materials were observed, before and after washing, with scanning and transmission electron microscopy (SEM, TEM); energy-dispersive X-ray analysis (EDX), and electron diffraction (ED).

Results

SDF appeared to produce globular particles of CaF₂ on the surface of the HAp, but these disappeared on washing, whilst with AgNO₃ yellow cubic crystals of Ag₃PO₄ formed which were not dissolved on washing, but which darkened, converting gradually to metallic silver, on exposure to light. NaF had no effect on gelatin, whilst with SDF and AgNO₃, particles of silver were produced which were resistant to washing.

Conclusions

Both principal components of tooth tissue react with SDF; the solubility of the putative CaF₂ formed weakens the case for it exerting a caries-protective effect. The importance of the persistent silver needs further study.     

Effect of silver and fluoride ions on enamel demineralization: a quantitative study using micro-computed tomography

Background: This study aimed to investigate the effect of silver and fluoride ions on demineralization of enamel. Methods: The coronal parts of 40 extracted sound premolars were prepared into tooth blocks. An unvarnished occlusal surface window (OW) and a flat buccal/lingual surface window (FW) were created for each tooth by covering all other surfaces with an acid‐resistant varnish. These blocks were randomly allocated into four groups of 10 blocks each and immersed in respective solutions for 5 minutes: Group 1 – 2.36 M silver fluoride; Group 2 – 2.36 M potassium fluoride; Group 3 – 2.36 M silver nitrate; and Group 4 – deionized water. After 7‐day immersion in a buffered demineralization solution at pH 4.4, micro‐CT scans were taken. Results: Mean lesion depth in the FW area for tooth blocks in AgF, KF, AgNO₃ and control groups were 0 μm, 3.3 ± 10.3 μm, 156.3 ± 30.8 μm, and 173.6 ± 48.6 μm, respectively (p < 0.001). The difference in mean lesion depth between the AgNO₃ and control groups was not statistically significant (p > 0.05). Similar OW and FW lesions were observed in tooth blocks in the AgNO₃ and control groups. Conclusions: Topical application of a 2.36 M fluoride solution can inhibit demineralization of enamel while topical application of silver ions has little effect.     

An alternate technique of care using silver fluoride followed by stannous fluoride in the management of root caries in aged care

An alternate technique of care to prevent, arrest and manage root caries using aqueous silver fluoride followed by stannous fluoride (AgF+SnF₂) in aged care is demonstrated by three case studies. With increasing age, the inability to maintain ones own oral care from dementia, illness or frailty and polypharmacy induced salivary gland hypofunction will result in dental caries becoming a progessively greater burden for the elderly. Future generations of elders will live longer and need to maintain many more teeth longer than earlier generations. Both silver diamine fluoride (SDF)and AgF+SnF₂ arrest and prevent caries and are easy to use in residential aged care facilities. Clinical differences between SDF and AgF+SnF₂ are discussed. However, in aged care, AgF+SnF₂ may offer advantages over SDF. AgF+SnF₂ used to arrest and prevent caries in children can be modified to provide effective but minimally invasive care for an ageing and frail population. These techniques are rapid, inexpensive and nonthreatening suited to treat frail elders, dementia patients exhibiting challenging behaviours and patients with multiple rapidly progressing decay. Silver fluoride, applied before placing glass‐ionomer cement (GIC) restorations is an important adjunct to the atraumatic restorative technique and may retard caries reactivation more than GIC used alone.     

Fluoride Delivered via a Topical Application of 38% SDF and 5% NaF

ObjectivesThe objectives of this study were to compare the amount of fluoride delivered via a topical application of 38% silver diamine fluoride (SDF) solution and 5% sodium fluoride (NaF) varnish as well as to determine the amount of 38% SDF solution delivered using various micro-applicators.MethodsThe weights of 38% SDF (Saforide) and 5% NaF (Duraphat) applied to the occlusal surface of an extracted human upper first premolar with a regular-size (2.50-mm tip diameter) micro-applicator were measured using an electronic-analytical balance. Afterwards, the weight of 38% SDF applied to a premolar using the micro-applicators of 5 common brands (Premium Plus, 3M, Dentsply, Elevate Oral Care, and SDI) were studied. The tip diameter of each micro-applicator was measured under a microscope. The weights of the delivered fluoride and silver were also calculated.ResultsThe mean weights of the fluoride delivered via the SDF solution and NaF varnish were 0.25 ± 0.07 mg and 0.49 ± 0.08 mg, respectively (P < .001). In addition, the tip diameters of the micro-applicators ranged from 1.89 ± 0.03 mm to 2.76 ± 0.02 mm. The mean weights of the fluoride delivered per application of 38% SDF using different applicators ranged from 0.13 ± 0.06 mg to 0.30 ± 0.09 mg, whereas the mean weights of the silver ranged from 0.76 ± 0.32 mg to 1.68 ± 0.50 mg. The weights of the delivered 38% SDF solution varied with the brand and with the tip diameters of the dental micro-applicators (P < .001).ConclusionsThe fluoride of the 38% SDF solution delivered topically was significantly less than that of 5% NaF varnish. Moreover, the amount of SDF solution delivered depends on the brand and size of the micro-applicators.     

Characterization of silver diamine fluoride cytotoxicity using microfluidic tooth-on-a-chip and gingival equivalents

ObjectiveThis study aims to characterize the cytotoxicity potential of silver diamine fluoride (SDF) on dental pulp stem cells (DPSC) and gingival equivalents.MethodsDPSC cultured on 96-well plates was exposed directly to SDF (0.0001–0.01%) and cell viability (IC₅₀) quantified. Effect of SDF on DPSC viability under flow (with dentin barrier) conditions was evaluated using a custom-designed microfluidic "tooth-on-a-chip”. Permeability of dentin discs (0.5–1.5 mm thickness) was evaluated using lucifer yellow permeation assay. Dentin discs were treated with 38% SDF (up to 3 h), and cell viability (live/dead assay) of the DPSC cultured in the inlet (unexposed) and outlet (exposed) regions of the pulp channel was evaluated. To assess the mucosal corrosion potential, gingival equivalents were treated with 38% SDF for 3 or 60 min (OECD test guideline 431) and characterized by MTT assay and histomorphometric analysis.ResultsDPSC exposed directly to SDF showed a dose-dependent reduction in cell viability (IC₅₀: 0.001%). Inlet channels (internal control) of the tooth-on-a-chip exposed to PBS and SDF-exposed dentin discs showed> 85% DPSC viability. In contrast, the outlet channels of SDF-exposed dentin discs showed a decreased viability of< 31% and 0% (1.5 and ≤1.0 mm thick dentin disc, respectively) (p < 0.01). The gingiva equivalents treated with SDF for 3 and 60 min demonstrated decreased epithelial integrity, loss of intercellular cohesion and corneal layer detachment with significant reduction in intact epithelial thickness (p < 0.05).SignificanceSDF penetrated the dentin (≤1 mm thick) inducing significant death of the pulp cells. SDF also disrupted gingival epithelial integrity resulting in mucosal corrosion.     

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 four anticaries agents on lesion depth progression in an in vitro caries model.

PURPOSE: This study compares four chemotherapeutic regimens used for inhibiting carious lesion progression: silver nitrate (AgNO3); silver fluoride/stannous fluoride (AgF/SnF2); silver diammine fluoride (SDF); and chlorhexidine (CHX). METHODS: For this study, a bacterial model system containing Mutans streptococci (MS) and Lactobacilli casei (L) was used to generate carious lesions on 85 extracted sound permanent third molars which were randomly assigned to four test groups and one control group. At week two, the four treatment regimens were applied to the lesions (one treatment per test group). RESULTS: Six weeks later, lesions treated with a single AgF/SnF2 or AgNO3 application demonstrated 29% and 19% less lesion progression, respectively, than did the control group (P < 0.05). SDF and CHX did not differ significantly from the control. CONCLUSION: AgF/SnF2 and AgNO3 may be useful in slowing down carious lesion depth progression.     

Solid-state NMR spectroscopy measurement of fluoride reaction by bovine enamel and dentin treated with silver diammine fluoride

ObjectivesThe aim of this study was to investigate the formation of fluoride compounds in bovine enamel and dentin treated with silver diammine fluoride (SDF) using ¹⁹F and ³¹P solid-state magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy.MethodsEnamel and dentin powder, obtained from bovine teeth, were treated with 38% SDF for four minutes and then washed thoroughly with Milli-Q water. The dehydrated SDF-treated samples were then examined. ¹⁹F solid-state MAS NMR spectra were acquired and ¹H–³¹P cross-polarization (CP) experiments were performed on SDF-treated enamel and dentin powder. The surfaces of SDF-treated enamel and dentin blocks were observed by Scanning Electron Microscope (SEM).Results¹⁹F MAS NMR detected a more pronounced signal intensity for the dentin sample than the enamel, indicating an increased reactivity of SDF for dentin, compared with enamel. ¹⁹F NMR spectra for the SDF-treated samples showed fluorhydroxyapatite (FHAp), and other fluoride compounds such as CaF₂ and the fluoride-substituted carbonate. The ¹H–³¹P CP intensities of prominent peaks were lower for the SDF-treated samples than the non-treated sample, indicating that the F^- ion replaced the OH^- ion in the lattice tunnel. SEM observations on the SDF-treated samples showed pronounced multiple precipitation and particles in dentin compared with enamel.SignificanceThe solid-state MAS NMR revealed the reaction of fluoride on enamel and dentin and the identification of fluoride compounds. In particular, the formation of FHAp indicates that SDF is effective in reducing the risk of tooth decay.     

The inhibitory effects of silver diamine fluorides on cysteine cathepsins

Aim

The expression of cysteine cathepsins in human carious dentine suggests that this enzyme contributes to the collagen degradation in caries progress. This study investigated whether silver diamine fluoride (SDF) inhibited the activity of cysteine cathepsins.

Methods

Three commercial SDF solutions with concentrations at 38%, 30% and 12% were studied. Two fluoride solutions with the same fluoride ion (F^-) concentrations as the 38% and 12% SDF solutions, and 2 silver solutions with the same silver ion (Ag⁺) concentrations as the 38% and 12% SDF solutions were prepared. Five samples of each experimental solution were used to study their inhibitory effect on two cathepsins (B and K) using cathepsin assay kits. Positive control contained assay buffer and cathepsins dilution was used to calculate the percentage inhibition (difference between the mean readings of the test solution and control solution divided by that of the control group).

Results

The percentage inhibition of 38%, 30% and 12% SDF on cathepsin B were 92.0%, 91.5% and 90.3%, respectively (p < 0.001); on cathepsin K were 80.6%, 78.5% and 77.9%, respectively (p < 0.001). Ag⁺ exhibited the inhibitory effect against both cathepsin B and K with or without the presence of F^- (p < 0.01). The solutions containing Ag⁺ have significantly higher inhibitory effect than the solutions containing F^- only (p < 0.01).

Conclusion

According to this study, SDF solution at all 3 tested concentrations significantly inhibited the activity of cathepsin B and K.     

Spray-drying-assisted fabrication of CaF2/SiO2 nanoclusters for dental restorative composites

ObjectiveThe objective of this study is to develop novel CaF₂/SiO₂ nanoclusters (NCs) fillers, which can endow the dental resin composites (DRCs) with excellent mechanical properties, stable and sustained fluoride ion release, and good antibacterial activity.MethodsThe CaF₂/SiO₂ NCs were efficiently fabricated by assembling CaF₂/SiO₂ nanoparticles (NPs) as building blocks with a spray-drying technology. CaF₂/SiO₂ NCs with different SiO₂ coating amounts (20 wt%, 50 wt% and 80 wt%) were incorporated into the DRCs at the filler content of 55 wt% for the measurement of mechanical properties including flexural strength, flexural modulus, compressive strength, and hardness. The effect of the filling amount of CaF₂/50SiO₂ NCs (50 represents 50 wt% SiO₂ coating amount) in the DRCs was investigated, while CaF₂/50SiO₂ NPs were adopted as comparison group. The fluoride ion release and antibacterial activity of the DRCs with the optimal mechanical performances were evaluated. Furthermore, the statistical analyses were performed for mechanical properties.ResultsSpherical CaF₂/50SiO₂ NCs with an average size of 2.4 µm were obtained at the feed rate of 7.4 mL/min and the CaF₂/50SiO₂ NPs solid content of 2 wt% in the suspension. The optimum comprehensive performances of the DRCs can be achieved by filling 55 wt% CaF₂/50SiO₂ NCs. Compared with CaF₂/50SiO₂ NPs, the filling amount of CaF₂/50SiO₂ NCs was increased by 5 wt% (50–55 wt%), and under the same filling amount of 50 wt%, the flexural strength, flexural modulus, compressive strength, and hardness of the DRCs containing CaF₂/50SiO₂ NCs were improved by 9.8%, 17.7%, 7.5% and 69.8%, respectively. Furthermore, the DRCs filled with 50 wt% CaF₂/50SiO₂ NCs exhibited more cumulative F-release by 126% and more stable F-release rate than the counterpart filled with 50 wt% CaF₂/50SiO₂ NPs after immersed for 1800 h. And 55 wt% CaF₂/50SiO₂ NCs filled DRCs could inhibit the growth of S. mutans, reaching an antibacterial ratio of 93%.SignificanceThe spray-dried CaF₂/50SiO₂ NCs are promising fillers for the development of high-performance multifunctional DRCs.     

In vivo effects of fluoride on enamel permeability

This in vivo study evaluated the effects of topical fluoride application on enamel by repeated scanning electron microscopy analysis of replicas. Baseline fluid droplets were employed as qualitative indication of enamel permeability. CaF₂-like globules were detected in vivo after fluoride application and were not found after professional brushing, ultrasound action, or chemical extraction. Absence of water permeability of enamel was demonstrated even after removal of CaF₂-like globules. Droplets reappeared within 1 h in sodium fluoride-treated teeth, but they did not reappear even after 1 week following topical enamel treatment with acidulated phosphate fluoride. Teeth treated with an acidulate fluoride-free solution showed lack of CaF₂-like globules and no droplets for at least 1 week as detected in acidulate phosphate fluoride-treated teeth. The caries-preventing action of fluoride may be due to its ability to decrease permeability and diffusion pathways. CaF₂-like globules seem to be indirectly involved in enamel protection over time maintaining an impermeable barrier, and phosphoric acid seemed to play an unexpected fluoride-independent preventive role.     

Pharmacokinetics of 38% topical silver diamine fluoride in healthy adult volunteers

Background

Silver diamine fluoride (SDF) is used topically to prevent or arrest caries. The authors' aim was to characterize the kinetics of silver and fluoride after topical application of SDF.

Ion Concentration of Silver Diamine Fluoride Solutions

ObjectiveThe aim of this work was to determine the free fluoride and silver ion concentrations and the alkalinity of 4 commercially available 38% silver diamine fluoride (SDF) solutions.MethodsFour common brands of 38% SDF solutions, namely Saforide, Advantage Arrest, e-SDF, and Topamine, were selected. Three bottles of each brand of SDF solution from the same lot were assessed. Measurements of the silver and fluoride content and alkalinity were performed directly when a bottle was opened. Each measurement was repeated to recheck its reliability. The free fluoride ion concentrations were measured using a calibrated ion-selective electrode. The free silver ion concentrations were measured using optical emission spectrometry. The alkalinity of the SDF solution was determined with a pH electrode.ResultsThe mean concentrations of fluoride ions of the Saforide, Advantage Arrest, e-SDF, and Topamine were 43,233 ppm, 44,333 ppm, 51,370 ppm, and 54,400 ppm, respectively; their percentage differences from the expected value (44,800 ppm) were 3.5%, 2.4%, 14.7%, and 21.4%, respectively. The mean concentrations of silver ions of the Saforide, Advantage Arrest, e-SDF, and Topamine were 258,841 ppm, 260,016 ppm, 336,149 ppm, and 319,966 ppm, respectively; their percentage differences from the expected value (253,900 ppm) were 3.2%, 5.8%, 32.4%, and 25.9%, respectively. The 4 products had pH values of 9.2, 9.1, 9.2, and 9.0, respectively.ConclusionsThis study showed differences between the claimed and measured fluoride and silver ion concentrations in 4 common 38% SDF products, which were alkaline with a pH value of 9.     

Effect of silver-containing agents on the ultra-structural morphology of dentinal collagen

ObjectiveThis study investigated the effect of silver diammine fluoride (SDF), nano-silver (AgNPs) and nano-silver/potassium fluoride (AgNPs/KF) on the morphology of dentin collagen and color staining on the dentin. Also, we investigated the anti-caries properties in terms of anti-bacterial effects and potentiality of dentin remineralization at collagen level.MethodsDentin specimens obtained from bovine tooth roots were finished with #2000 SiC and sonicated for 5 min. Specimens were divided into two main groups: sound and demineralized dentin. Each group was subdivided into five subgroups according to treatment solution: control (no treatment), SDF, nano-silver (AgNPs), AgNPs/KF and KF. Specimens were analyzed using transmission electron microscope (TEM), spectrophotometer, scanning electron microscope (SEM) and antibacterial test. Repeated Measures ANOVA was used for statistical analysis of color change while one-way ANOVA was used for CFU analysis.ResultsRegarding color change, SDF showed the highest values while the other groups exhibited insignificant changes. SDF showed alteration in the collagen fibrils while the other groups showed normal intact fibrils. Regarding antibacterial activity, SDF and AgNPs/KF showed the greatest antibacterial effect.SignificanceSDF altered the dentin collagen morphology and inferior ethetics, but still providing intrafibrillar remineralization. Nano-silver fluoride preparations (AgNPs/KF) can be an alternative material for SDF as it can preserve the dentin collagen, showing no color change overtime, and provide a high anti-caries property including intrafibrillar remineralization with a significant anti-bacterial effect.     

Differences between normal and demineralized dentine pretreated with silver fluoride and potassium iodide after an in vitro challenge by Streptococcus mutans

BACKGROUND: The application of diamine silver fluoride (Ag(NH3)2F) and potassium iodide (KI) to demineralized dentine has been shown to inhibit the growth of Streptococcus mutans. The purpose of this study was to observe the differences between demineralized and non-demineralized dentine treated with AgF/KI. METHODS: Thirty-five dentine discs were bonded to the bases of 5 mL polycarbonate screw top vials which were filled with nutrient medium, sterilized and placed into the overflow from a continuous culture of S. mutans. Samples were divided as follows: 10 samples of demineralized dentine; 10 samples of demineralized dentine treated with AgF/KI; 5 samples of non-demineralized dentine; and 10 samples of non-demineralized dentine treated with AgF/KI. Following two weeks connected to the Chemostat, an electron probe microanalysis (EPMA) of percentage weights and penetration depths of calcium, phosphorous silver and fluoride was conducted. Bacterial growth was monitored by taking optical density readings of the growth medium in each vial and outer surfaces of the specimens were examined by scanning electron microscopy (SEM). RESULTS: AgF/KI treatment of demineralized and non-demineralized dentine prevented biofilm formation and reduced further demineralization by S. mutans. AgF/KI treatment of demineralized dentine was more effective in reducing dentine breakdown and the growth of S. mutans. Significantly higher levels of silver and fluoride were deposited within demineralized dentine. CONCLUSIONS: A topical treatment with AgF/KI on dentine reduced in vitro caries development and inhibited surface biofilm formation. Reduction of in vitro caries development and viability of S. mutans was more pronounced on the dentine samples that had been demineralized prior to the application of     

Randomized clinical trial on effectiveness of silver diamine fluoride and glass ionomer in arresting dentine caries in preschool children

ObjectiveTo compare the effectiveness of annual topical application of silver diamine fluoride (SDF) solution, semi-annual topical application of SDF solution, and annual application of a flowable high fluoride-releasing glass ionomer in arresting active dentine caries in primary teeth.MethodsA total of 212 children, aged 3–4 years, were randomly allocated to one of three groups for treatment of carious dentine cavities in their primary teeth: Gp1-annual application of SDF, Gp2-semi-annual application of SDF, and Gp3-annual application of glass ionomer. Follow-up examinations were carried out every six months to assess whether the treated caries lesions had become arrested.ResultsAfter 24 months, 181 (85%) children remained in the study. The caries arrest rates were 79%, 91% and 82% for Gp1, Gp2 and Gp3, respectively (p = 0.007). In the logistic regression model using GEE to adjust for clustering effect, higher caries arrest rates were found in lesions treated in Gp2 (OR = 2.98, p = 0.007), those in anterior teeth (OR = 5.55, p < 0.001), and those in buccal/lingual smooth surfaces (OR = 15.6, p = 0.004).ConclusionAnnual application of either SDF solution or high fluoride-releasing glass ionomer can arrest active dentine caries. Increasing the frequency of application to every 6 months can increase the caries arrest rate of SDF application.Clinical significanceArrest of active dentine caries in primary teeth by topical application of SDF solution can be enhanced by increasing the frequency of application from annually to every 6 months, whereas annual paint-on of a flowable glass ionomer can also arrest active dentine caries and may provide a more aesthetic outcome.     

渗透树脂和多乐氟处理脱矿釉质后的抗酸性和再矿化能力比较

目的 通过观察渗透树脂与多乐氟处理脱矿釉质后其牙齿表面显微硬度和粗糙度的变化,对两种材料在釉质抗酸性和再矿化能力方面的性能进行评估。方法 选择正畸拔除的健康前磨牙48颗,建立釉质表面脱矿模型,按照不同材料的处理条件随机分为4组,A（不做任何处理）,B（渗透树脂）,C（多乐氟）;D（渗透树脂+多乐氟）,分别经脱矿液组（1d,3d）和再矿化液组（7d）浸泡处理后,测定牙齿表面的显微硬度和粗糙度。结果 不同材料处理脱矿模型后即刻,B、D组的显微硬度、粗糙度均明显增加（P<0.001）,B、D组之间无统计学差异（P>0.05）;而C组显微硬度、粗糙度均明显减低（P<0.001）。继续脱矿（1d,3d）后,各组的显微硬度均下降,而粗糙度却明显增加;再矿化7d后,A、C组显微硬度和粗糙度均显著增加（P<0.001）,B、D组增加不明显（P>0.05）。结论 渗透树脂具有良好的改善牙齿表面硬度的作用,但在抗酸性和促进牙齿再矿化方面无明显优势。而氟化物则在抗酸性和促进再矿化方面有突出表现。当两者联合应用时,可以起到较好协同作用,明显增强牙齿的硬度、抗酸性和再矿化性能。     

Caries-preventive effect of anti-erosive and nano-hydroxyapatite-containing toothpastes in vitro

Objectives

The aim of the study was to investigate the caries-preventive effect of newly developed fluoride and fluoride-free toothpastes specially designed for erosion prevention. The hypothesis was that these products might also show superior caries-inhibiting effect than regular fluoride toothpastes, since they were designed for stronger erosive acid challenges.

Materials and methods

Enamel specimens were obtained from bovine teeth and pre-demineralized (pH = 4.95/21 days) to create artificial caries lesions. Baseline mineral loss (ΔZ_B) and lesion depth (LD_B) were determined using transversal microradiography (TMR). Ninety specimens with a median ΔZ_B (SD) of 6027 ± 1546 vol% × μm were selected and randomly allocated to five groups (n = 18). Treatments during pH-cycling (14 days, 4 × 60 min demineralization/day) were brushing 2×/day with AmF (1400 ppm F⁻, anti-caries [AC]); AmF/NaF/SnCl₂/Chitosan (700 ppm F⁻/700 ppm F⁻/3500 ppm Sn²⁺, anti-erosion [AE1]); NaF/KNO₃ (1400 ppm F⁻, anti-erosion [AE2]); nano-hydroxyapatite-containing (0 ppm F⁻, [nHA]); and fluoride-free toothpastes (0 ppm F⁻, negative control [NC]). Toothpaste slurries were prepared with mineral salt solution (1:3 wt/wt). After pH-cycling specimens presenting lesion, surface loss (mainly by NC and nHA) were discarded. For the remaining 77 specimens, new TMR analyses (ΔZ_E/LD_E) were performed. Changes in mineral loss (ΔΔZ = ΔZ_B − ΔZ_E) and lesion depth (ΔLD = LD_B − LD_E) were calculated.

Results

All toothpastes caused significantly less demineralization (lower ΔΔZ) than NC (p < 0.05, ANOVA) except for nHA. The fluoride toothpastes did not differ significantly regarding ΔΔZ and ΔLD (p > 0.05, ANOVA).

Conclusion/clinical relevance

While both anti-erosive and anti-caries toothpastes reduced mineral loss to a similar extent, the fluoride-free nano-hydroxyapatite-containing toothpaste seemed not to be suitable for inhibition of caries demineralization in vitro.

     

Twelve-month randomized controlled trial of 38% silver diamine fluoride with or without potassium iodide in indirect pulp capping of young permanent molars

BackgroundThe clinical and radiographic effectiveness of 38% silver diamine fluoride (SDF) with and without potassium iodide (KI) was tested and compared with resin-modified glass ionomer cement (RMGIC) in indirect pulp capping of deep carious lesions in young permanent molars.MethodsOne hundred eight permanent first molars with deep occlusal cavitated carious lesions in 49 children aged 6 through 9 years were randomly allocated into 3 groups (n = 36 molars per group) and treated with SDF plus KI, SDF, and RMGIC. RMGIC was used as a base and a resin-based composite restoration followed. Clinical assessments for secondary caries (primary outcome), postoperative pain, tooth vitality, and restoration success and quality rates according to Modified US Public Health Service and Ryge Criteria for Direct Clinical Evaluation of Restorations were performed after 3, 6, and 12 months. Periapical radiographs were obtained at baseline, 6 months, and 12 months. Outcomes were assessed using mixed effects multilevel logistic and linear regression analyses.ResultsThere were no significant differences (P = .26) among the groups at all times for secondary caries, postoperative pain, tooth vitality, clinical abscess, radiographic signs of pulpal pathology, restorations’ marginal adaption, anatomic form, and surface roughness. There was a significant difference (P = .03) in restoration color, marginal staining, and luster. The RMGIC group outperformed the 2 SDF groups in color and luster.ConclusionsThe authors did not find differences among the groups in preventing secondary caries or pain or in maintaining pulpal health. The RMGIC group had better restoration color and luster than both SDF groups and better marginal staining than the SDF group.Practical ImplicationsThe results of this study can help guide treatment decision making regarding use of SDF and SDF plus KI as indirect pulp capping materials in deep cavitated lesions.This clinical trial was registered at ClinicalTrials.gov. The registration number is NCT04236830.     

Liquid membrane system for extraction and electrodeposition of silver(I)

The process of Ag⁺ ions extraction from nitric solutions by bulk liquid membranes containing di(2-ethylhexyl)phosphoric acid and tri-n-octylamine accompanied with silver(I) electrodeposition from perchloric acid solutions is studied at galvanostatic electrodialysis. The effects of the current density as well as of composition of the liquid membrane and aqueous solutions on the rate of the silver(I) transport are determined. More than 90% of silver ions was extracted from the feed solution containing 0.01 mol l⁻¹ AgNO₃ and about 40% of metal was electrodeposited during 1 h of electrodialysis. Sound adherent silver coatings have been deposited on platinum and copper cathodes.