The effect of xylitol and fluoride on remineralization for primary tooth enamel caries in vitro

The effect of fluoride and xylitol on remineralization at the early stage of the enamel caries in primary tooth was studied. The samples were divided into four groups (control, 10% xylitol, 950 ppm NaF and 10% xylitol+950 ppm NaF) and analyzed by the using single thin section method and pHcycling model in vitro. The remineralizing ratio were control –8.9%, xylitol –0.4%, NaF 8.3% and xylitol + NaF 32.4%, respectively. Xylitol+NaF group particularly showed significantly smaller ΔZ value compared with 0 days (P<0.05). Therefore we assume that the effect of xylitol and fluoride are additive. We concluded that xylitol and fluoride treatment to the tooth enamel may be an effective caries-preventive measure in both primary and permanent tooth enamel.     

Sodium fluoride effect on erosion–abrasion under hyposalivatory simulating conditions

ObjectivesTo investigate the effect of fluoride (0, 275 and 1250 ppm F; NaF) in combination with normal and low salivary flow rates on enamel surface loss and fluoride uptake using an erosion–remineralization–abrasion cycling model.DesignEnamel specimens were randomly assigned to 6 experimental groups (n = 8). Specimens were individually placed in custom made devices, creating a sealed chamber on the enamel surface, connected to a peristaltic pump. Citric acid was injected into the chamber for 2 min followed by artificial saliva at 0.5 (normal flow) or 0.05 (low flow) ml/min, for 60 min. This cycle was repeated 4×/day, for 5 days. Toothbrushing with abrasive suspensions containing fluoride was performed for 2 min (15 s of actual brushing) 2×/day. Surface loss was measured by optical profilometry. KOH-soluble fluoride and enamel fluoride uptake were determined after the cycling phase. Data were analysed by two-way ANOVA.ResultsNo significant interactions between fluoride concentration and salivary flow were observed for any tested variable. Low caused more surface loss than normal flow rate (p < 0.01). At both flow rates, surface loss for 0 was higher than for 275, which did not differ from 1250 ppm F. KOH-soluble and structurally-bound enamel fluoride uptake were significantly different between fluoride concentrations with 1250 > 275 > 0 ppm F (p < 0.01).ConclusionsSodium fluoride reduced enamel erosion/abrasion, although no additional protection was provided by the higher concentration. Higher erosion progression was observed in low salivary flow rates. Fluoride was not able to compensate for the differences in surface loss between flow rates.     

Promotion of enamel caries remineralization by an amelogenin-derived peptide in a rat model

ObjectiveAn amelogenin-derived peptide has been shown to promote remineralization of demineralized enamel in an in vitro model of initial caries induced by pH cycling. The present study examines whether the peptide exerts similar effects within the complex oral environment in vivo.DesignSpecific pathogen-free Sprague-Dawley rats (n = 36) were infected with Streptococcus mutans, given ad libitum access to Diet 2000 and drinking water supplemented with sucrose (10%, w/v), and then randomly divided into three groups treated with 25 μM peptide solution, 1 g/L NaF or deionized water. Molar teeth were swabbed twice daily with the respective solutions for 24 days. Then animals were killed, their jaws were removed and caries lesions were analyzed using the quantitative light-induced fluorescence-digital (QLF-D) technique to measure changes in mineral content. To verify QLF-D results, caries were scored for lesion depth and size using the Keyes method, and analyzed using polarized light microscopy (PLM).ResultsMineral gain was significantly higher in teeth treated with peptide or NaF than in teeth treated with water (p < 0.05), based on the QLF-D results (ΔF and ΔQ). Incidence of smooth-surface and sulcal caries based on Keyes scores was similar in rats treated with peptide or NaF, and significantly lower in these groups than in rats treated with water (p < 0.05). Lesions on teeth treated with peptide or NaF were shallower, based on PLM. No significant differences were observed between molar enamel caries treated with peptide or NaF.ConclusionsThis amelogenin-derived peptide can promote remineralization in a rat caries model, indicating strong potential for clinical use.     

In vitro enamel erosion and abrasion-inhibiting effect of different fluoride varnishes

ObjectiveTo investigate the erosion and abrasion inhibiting effect of CPP-ACP/NaF and xylitol/NaF varnishes.MethodsBovine enamel samples (n = 40) were exposed to the following treatments (n = 10): NaF varnish (Duraphat^®, positive control); CPP-ACP/NaF varnish (MI varnishTM); xylitol/NaF (Profluorid^®) or distilled and deionized water (MilliQ^®, negative control). The samples were submitted for 3 days to 4 cycles/day of erosion (5 min in Sprite Zero) and 2 cycles of abrasion/day after the first and last erosive challenge, with a toothbrush machine and slurries of a placebo toothpaste for 15 s (50 strokes/s). Among the cycles and after the last daily cycle, the specimens remained in artificial saliva. The change in the enamel surface was evaluated by using 3D non-contact optical profilometry with surface roughness (Ra and Sa values) and tooth structure loss (TSL) measurements. Scanning electron microscopy (SEM) assessed the enamel topographic characteristics. Differences in the Ra, Sa and TSL among treatments were tested using one-way ANOVA followed by the Tukey test.ResultsAll varnishes promoted better results for Ra and Sa values than the negative control (p = 0.0001), without difference among them (p > 0.05). However, CPP-ACP/NaF varnish stimulated fewer TSL (7.09 ± 0.70 μm) compared to NaF varnish (10.33 ± 1.36 μm, p = 0.002), xylitol/NaF varnish (9.96 ± 0.41 μm, p = 0.007) and the negative control (18.38 ± 3.32 μm, p = 0.0001).ConclusionA single-application of fluoride topical varnishes was effective in reducing enamel wear. The CPP-ACP/NaF varnish had the best effect against enamel loss from an erosion-abrasion challenge.     

Effect of biomimetic mineralization on enamel and dentin: A Raman and EDX analysis

ObjectiveTo investigate the effect of an experimental biomimetic mineralization kit (BIMIN) on the chemical composition and crystallinity of caries-free enamel and dentin samples in vitro.MethodsEnamel and dentin samples from 20 human teeth (10 for enamel; 10 for dentin) were divided into a control group without treatment and test samples with BIMIN treatment. Quantitative analysis of tissue penetration of fluoride, phosphate, and calcium was performed using energy-dispersive X-ray spectroscopy (EDX). Mineralization depth was measured by Raman spectroscopy probing the symmetric valence vibration near 960 cm⁻¹ as a marker for crystallinity. EDX data was statistically analyzed using a paired t-test and Raman data was analyzed using the Student’s t-test.ResultsEDX analysis demonstrated a penetration depth of fluoride of 4.10 ± 3.32 μm in enamel and 4.31 ± 2.67 μm in dentin. Calcium infiltrated into enamel 2.65 ± 0.64 μm and into dentin 5.58 ± 1.63 μm, while the penetration depths for phosphate were 4.83 ± 2.81 μm for enamel and 6.75 ± 3.25 μm for dentin. Further, up to 25 μm of a newly mineralized enamel-like layer was observed on the surface of the samples. Raman concentration curves demonstrated an increased degree of mineralization up to 5–10 μm into the dentin and enamel samples.SignificanceBiomimetic mineralization of enamel and dentin samples resulted in an increase of mineralization and a penetration of fluoride into enamel and dentin.     

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.     

Inhibition of enamel mineral loss by fissure sealant: An in situ study

ObjectivesThis study evaluated the effect of fluoride and non-fluoride sealants on hardness decrease (HD) and marginal adaptation (MA) on enamel substrates after cariogenic challenge.MethodsOcclusal enamel blocks, from human third molars, were randomly divided into six groups (n = 12), according to occlusal fissures condition (S – sound; C – caries-like lesion; CF – caries-like lesion + topical fluoride) and sealants (F – FluroShield; H – Helioseal Clear Chroma). Lesion depths were 79.3 ± 33.9 and 61.3 ± 23.9 for C and CF groups, respectively. Sealants were placed on occlusal surface and stored at 100% humidity (37 °C; 24 h/d). HD was measured by cross-sectional microhardness analysis at the sealant margin distances: ?1 (under sealant), 0 (sealant margin), 1, 2 (outer sealant). Sealant MA was observed by polarized light microscopy and scored according to: 0 – failure (no sealant MA or total sealant loss); 1 – success (sealant MA present). MA and HD were analysed by ANOVA-R and mixed model analysis, respectively.ResultsFor HD (ΔS), F values (6900.5 ± 3686.6) were significantly lower than H values (8534.6 ± 5375.3) regardless of enamel substrates and sealant margin distances. Significant differences were observed among sealant margin distances: ?1 (5934.0 ± 3282.6) < 0 (8701.5 ± 6175.7) = 1 (8473.2 ± 4299.4) = 2 (7761.5 ± 4035.1), regardless of sealant and substrate. MA was similar for all groups (p ≥ 0.05).ConclusionMA was not affected by sealant type or substrate condition, whereas enamel HD was favourably impacted by fluoride in the sealant. In addition, sealants were more effective as a physical barrier than as its chemical potency in reducing enamel HD.Clinical significanceSealing with a fluoride material is a recommended procedure to prevent caries of occlusal permanent molars in high-caries-risk patients, even though those exhibiting white spot lesions, since the enamel hardness decrease when fluoride sealant was used in vitro.     

Remineralisation of enamel with silver diamine fluoride and sodium fluoride

Objective

To evaluate the remineralising effect of the adjunctive application of 38% silver diamine fluoride (SDF) solution and 5% sodium fluoride (NaF) varnish on artificial enamel caries lesions.

Effect of low level fluoride on demineralization kinetics of human dental enamel

The purpose of this study was to examine the effect of fluoride levels similar to those reported for saliva from low fluoridated and high fluoridated water areas on the demineralization of human permanent enamel. An adaptation of the method described by Robinson et al. was used. Sections of sound enamel were immersed in a vial containing demineralizing solution [2.0 mM Ca(NO₃)₂, 1.2 mM KHPO₄ in 50 mM acetic acid, pH 4.8] for 1 hour. The demineralizing solution contained 0, 0.02 or 0.05 ppm fluoride, added as NaF was prepared. Twenty microliters aliquots were taken from the demineralizing solution at the time point up to 1 hour, with a sampling frequency bias towards the early time point. The phosphate content of the removed sample was determined by colorimetry. When the mineral loss curves for fluoridated and non-fluoridated demineralizing solutions were compared, there were significant differences between both groups. There was a decrease in the net mineral loss when fluoride was used. This result suggested that salivary fluoride levels of 0.02 ppm and 0.05 ppm had a protective effect against demineralization.     

Chitosan microparticles for the controlled delivery of fluoride

ObjectivesTo manufacture and characterise chitosan/fluoride microparticles prepared by spray drying and assess their utility as controlled release vehicles for fluoride.MethodsMicroparticles were manufactured from dispersions containing 1.0% and 2.0% (w/v) chitosan and 0.20% or 0.40% (w/v) NaF in the absence/presence of glutaraldehyde. Particle size distributions were determined using laser diffraction; fluoride loading and release were determined by ion-selective electrode. Release profiles were studied in isotonic media (pH 5.5) over 360 min; microparticles exhibiting greatest cumulative fluoride release were further evaluated at pH 4.0 and 7.0. Particle morphology was investigated using environmental scanning electron microscopy. Bioadhesion parameters were determined with a texture-probe analyser.ResultsMicroparticles exhibited low polydispersity and volume mean diameters (VMDs) <6 μm. VMDs increased on doubling the chitosan/fluoride concentrations but were largely independent of glutaraldehyde concentration. Recovered yields were inversely proportional to dispersion viscosity due to compromised fluid atomisation; adding NaF reduced viscosity and improved yields. Best-case entrapment efficiency and NaF loading were 84.1% and 14%, respectively. Release profiles were biphasic, releasing 40–60% of the total fluoride during the first 600 s, followed by a prolonged release phase extending out to 6 h. Incorporation of 0.40% NaF to the 2.0% chitosan dispersion yielded microparticles with reduced bioadhesive parameters (F_max and WOA) versus the chitosan-only control whilst retaining significant bioadhesive potential.ConclusionsBioadhesive chitosan/fluoride microparticles manufactured using a spray-drying protocol have been extensively characterised and further opportunity for optimisation identified. These microparticles may provide a means of increasing fluoride uptake from oral care products to provide increased protection against caries, however further work is required to demonstrate this principle in vivo.Clinical significanceSpray-drying is a low-cost route for the manufacture of bioadhesive chitosan/fluoride microparticles which can be exploited as controlled fluoride release agents to aid fluoride retention in the oral cavity. The potential exists to optimise release profiles to suit the delivery format thereby maximising the cariostatic benefits.     

In situ remineralisation of eroded enamel lesions by NaF rinses

ObjectiveThe purpose of this pilot study was to evaluate the remineralisation of eroded enamel by NaF rinses in an intra-oral model.MethodsServing as their own control, subjects (N = 80) participated in a randomised, four-leg (20 subjects/leg), 28-day, parallel design study. In each leg, each participant wore a customised orthodontic bracket attached to a mandibular molar that contained one tooth block having an initial erosive lesion (0.3% citric acid, pH 3.75, 2 h). Within the 28-day period, participants engaged in twice-daily brushing for 1 min with a fluoride-free dentifrice followed by 1-min rinsing with one of the following aqueous rinses: fluoride-free (0 ppm F), 225 ppm F, 225 ppm F plus functionalised β-tricalcium phosphate (fTCP), and 450 ppm F. Following intra-oral exposure, appliances were removed and specimens were analysed using surface microhardness (SMH) and transverse microradiography (TMR).ResultsStatistically significant (p < 0.05) remineralisation, as determined by SMH and TMR, of the eroded enamel relative to baseline occurred for each fluoride system. No significant differences in SMH were observed amongst the fluoride groups (p > 0.05), however, 225 ppm plus fTCP produced 27% and 7% SMH indent length reduction relative to 225 ppm F and 450 ppm F, respectively. No significant differences in TMR were observed amongst the fluoride groups (p > 0.05), however, 225 ppm F plus fTCP and 450 ppm F produced significant (p < 0.05) mineral gains relative to the fluoride-free control, whilst 225 ppm F did not (p > 0.05). Relative to the 225 ppm F group, the 450 ppm F and 225 ppm F plus fTCP groups produced 65% and 61% greater mineral change, respectively.ConclusionsThese pilot results demonstrate this model is sensitive to fluoride and that addition of fTCP to an aqueous rinse containing 225 ppm F may provide significant remineralisation benefits. Therefore, the combination of relatively low levels of fluoride and fTCP might be an effective alternative to a high fluoride treatment for anti-erosion benefits.     

Effect of topical application of fluoride gel NaF 2% on enzymatic and non-enzymatic antioxidant parameters of saliva

ObjectiveThe aim of the study was to evaluate the effect of topical fluoride gel NaF 2% application on antioxidant parameters of whole saliva from children.DesignThe saliva mechanically stimulated with parafilm was collected from 25 children (6–12 years) attending the Clinic of Paediatric Dentistry of Universidade Cruzeiro do Sul, São Paulo, Brazil, before (control group) and immediately after application of neutral fluoride gel NaF 2% (fluoride-gel group), according to the Standards for Research Using Human Subjects, Resolution 196/96 of the USA National Health Council of 10/10/1996. Afterwards, pre-post ferric-reducing antioxidant power (FRAP), trolox-equivalent antioxidant capacity (TEAC), uric acid, reduced/oxidised glutathione content (GSH/GSSG) and total peroxidase activity (TPO) were evaluated in whole saliva of both groups.ResultsAll non-enzymatic antioxidant parameters were augmented by fluoride-gel NaF 2% application, whereas a notable reduction (31%) of peroxidase activity was concomitantly observed in the children's saliva (p ≤ 0.05). Nevertheless, the reducing power of saliva was kept unaltered under these circumstances (p ≤ 0.05).ConclusionsDespite the reduced activity of peroxidase (an important antimicrobial and antioxidant enzyme), the topical fluoride gel NaF 2% favourably stimulated the release of non-enzymatic antioxidant components of saliva, sustaining the reducing power of saliva and the natural defences of the oral cavity.     

A new optical detection method to assess the erosion inhibition by in vitro salivary pellicle layer

ObjectivesApplication of the recently developed optical method based on the monitoring of the specular reflection intensity to study the protective potential of the salivary pellicle layer against early enamel erosion.MethodsThe erosion progression was compared between two treatment groups: enamel samples coated by the 15 h-in vitro-formed salivary pellicle layer (group P, n = 90) and the non-coated enamel surfaces (control group C, n = 90). Different severity of the erosive impact was modelled by the enamel incubation in 1% citric acid (pH = 3.6) for 2, 4, 8, 10 or 15 min. Erosion quantification was performed by the optical method as well as by the microhardness and calcium release analyses.ResultsOptical assessment of the erosion progression showed erosion inhibition by the in vitro salivary pellicle in short term acidic treatments (≤4 min) which was also confirmed by microhardness measurements proving significantly less (p < 0.05) enamel softening in the group P at 2 and 4 min of erosion compared to the group C. SEM images demonstrated less etched enamel interfaces in the group P at short erosion durations as well.ConclusionsMonitoring of the specular reflection intensity can be successfully applied to quantify early erosion progression in comparative studies. In vitro salivary pellicle (2 h) provides erosion inhibition but only in short term acidic exposures.Clinical significanceThe proposed optical technique is a promising tool for the fast and non-invasive erosion quantification in clinical studies.     

Effect of iron on enamel demineralization and remineralization in vitro

ObjectiveTo evaluate the effect of ferrous sulphate on enamel demineralization and remineralization, using pH-cycling models.DesignFifty blocks were selected by their initial surface hardness and subjected to a pH-cycling demineralization process. Artificially demineralized lesions were produced in 60 blocks; out of these blocks, the surface hardness of 50 blocks and the cross-sectional hardness of 10 blocks were determined. The 50 blocks were then subjected to a remineralization pH-cycling process. Treatments were carried out using ferrous sulphate solutions of different concentrations (0.333, 0.840, 18.0, and 70.0 μg Fe/mL) and a control group (deionized water). The final surface hardness (SH₂) was determined, and the integrated subsurface hardness (ΔKHN) was calculated. The enamel blocks were analysed for fluoride, calcium, phosphorus, and iron. The obtained data were distributed heterogeneously and were analysed using the Kruskal–Wallis test (p < 0.05).ResultsIn demineralization pH cycling, the group treated with the 18.0 μg Fe/mL solution had higher secondary surface hardness and lower integrated subsurface hardness (ΔKHN) than the other groups. In remineralization pH cycling, the control group showed the lowest value of ΔKHN. A decline in Ca and P concentration was observed when the Fe concentration increased (p < 0.05). There was no significant difference in the F concentration (p > 0.05) and an increase in Fe concentration (p < 0.05) in the enamel was observed when the Fe concentration increased in both the demineralization and remineralization experiments.ConclusionThe results suggest that iron reduces demineralization but does not allow remineralization to occur.     

Effects of heat-inactivated Bifidobacterium BB12 on cariogenicity of Streptococcus mutans in vitro

ObjectiveSince some probiotic bacteria are cariogenic themselves, their suitability for caries management is questionable. Inactivated bacteria or their supernatants have been found to exert probiotic effects, whilst having several advantages compared with living bacteria. We hypothesized that viable and heat-inactivated Bifidobacterium animalis BB12 reduces the cariogenicity of Streptococcus mutans (SM) in vitro.DesignWe assessed mono- and mixed species biofilms of SM and viable or heat-inactivated BB12. Biofilms were grown in a continuous-culture-system under cariogenic conditions on smooth proximal enamel or cavitated dentine. For each of eight experimental subsets (4 biofilms × 2 hard-tissue conditions), a total of 32 specimens was used. After 10 days, bacterial numbers of 12 biofilms per group were analysed, and all specimens submitted to transversal microradiography.ResultsMineral loss was higher in cavitated dentine than smooth enamel for all biofilms (p < 0.001, t-test). BB12-monospecies biofilms induced significantly less mineral loss than SM in both enamel (p < 0.05) and dentine (p < 0.001). Viable BB12 did not significantly reduce cariogenicity of SM (p > 0.05), whilst heat-inactivated BB12 decreased cariogenicity of SM in dentinal cavities (p < 0.01). Bacterial numbers were higher on dentine than enamel (p < 0.05), but not significantly influenced by biofilm species (p > 0.05).ConclusionsHeat-inactivated BB12 reduced the cariogenicity of SM in dentinal cavities in vitro. Inactivated probiotics might be suitable for caries control.     

Mineralization-defects are comparable in fluorotic impacted human teeth and fluorotic mouse incisors

ObjectiveFluoride excess of 0.05–0.07 mg F/kg bw/day in water or food additives like salt is the principal cause of endemic dental fluorosis. How fluoride causes these defects is not clear yet. Recent studies in rodents suggest that development of enamel fluorosis is associated with insufficient neutralization of protons released during the formation of hypermineralized lines.DesignHere we examined whether hypermineralization could also be assessed by MicroCT in developing molar enamel of humans exposed to fluoride.ResultMicro-CT analysis of hypomineralized enamel from human fluorotic molars graded by the Thylstrup–Fejerskov (TF) Index as III–IV showed weak hypermineralized lines and hypermineralized patches not seen in TF-I/II grade enamel. The mesio-distal sides of these molar teeth were significantly smaller (∼18%, p = 0.02) than in TF-I/II teeth.ConclusionThe patterns of changes observed in human fluorotic teeth were similar to those in fluorotic rodent incisors. The data are consistent with the hypothesis that also in developing human teeth fluoride-stimulated local acidification of enamel could be a mechanism for developing fluorotic enamel.     

High-fluoride acitivates the FasL signalling pathway and leads to damage of ameloblast ultrastructure

ObjectiveHigh fluoride can induce stress-mediated apoptosis and degradation of ameloblasts. Fas ligand (FasL) has been regarded as a key regulator in intracellular responses for stress-induced apoptosis in reproductive or cancerous cell lineages. The objective of this study is to explore the role of FasL in the regulation of ameloblast ultrastructure damage.DesignPrimary ameloblasts were isolated from the molar tooth germ of 4-day-old SD rats. The ameloblasts were incubated with 3.2 mM NaF or nothing. After incubation for different time arranging from 12 h to 72 h, ELISA was used to detected the secretion levels of FasL in the medium. Then at 48 h post treatment, the ameloblast ultrastructure was detected with Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM), and expression of apoptotic proteins and peroxidative enzymes/products were examined. Finally, a specific FasL inhibitor was applied to co-treat the ameloblasts with NaF, and the ameloblast ultrastructure was detected with TEM and SEM.ResultsThe secretion of FasL was notably increased by 3.2 mM NaF treatment, and the increase reached to the peak after incubation for 48 h. High fluoride incubation damaged the ameloblast untrastructure manifesting a series of intracelluar stress responsing cell organelle destruction, and a marked increase in expression of apoptotic genes and oxidative stress. The FasL inhibitor treatment partially mitigated the untrastructure damage caused by high dose NaF.ConlusionHigh-fluoride leads to damage of the ameloblast ultrastructure through paritially acitivating the FasL signalling pathway.     

Optimization of calcium concentration of saliva with phosphoryl oligosaccharides of calcium (POs-Ca) for enamel remineralization in vitro

ObjectivePhosphoryl oligosaccharides of calcium (POs-Ca) are highly soluble calcium source made from potato starch. The aim of this study was to investigate the optimal concentrations of POs-Ca for the remineralization of subsurface enamel lesions in vitro.DesignDemineralized bovine enamel slabs (n = 5) were remineralized in vitro for 24 h at 37 °C with artificial saliva (AS) containing 0–0.74% POs-Ca to adjust the Ca/P ratio to 0.4–3.0, then sectioned and analysed by transversal microradiography (TMR). The data were analysed by Scheffe's post hoc test. The Ca/P ratio with most remineralization was used to investigate the effect of calcium on enamel remineralization (n = 11). The demineralized slabs were treated with AS with calcium-chloride- (CaCl₂-) or POs-Ca with an identical calcium content, and sectioned for TMR and wide-angle X-ray diffraction (WAXRD) analyses to evaluate the local changes in hydroxyapatite (HAp) crystal content. The data were analysed using the Mann–Whitney U-test.ResultsThe highest mineral recovery rate resulted from addition of POs-Ca to adjust the Ca/P to 1.67. At this ratio, the mineral recovery rate for AS containing POs-Ca (24.2 ± 7.4%) was significantly higher than that for AS containing CaCl₂ (12.5 ± 11.3%) (mean ± SD, p < 0.05). The recovery rate of HAp crystallites for AS containing POs-Ca (35.7 ± 10.9%) was also significantly higher than that for AS containing CaCl₂ (23.1 ± 13.5%) (p < 0.05). The restored crystallites were oriented in the same directions as in sound enamel.ConclusionsPOs-Ca effectively enhances enamel remineralization with ordered HAp at a Ca/P ratio of 1.67.     

Electrochemical evaluation of the hydrogen peroxide- and fluoride-induced corrosive property and its recovery on the titanium surface

PurposeThis study aimed to elucidate the effects of hydrogen peroxide (H₂O₂) and sodium fluoride (NaF) on titanium surfaces under conditions mimicking those encountered during dental treatment.MethodsTitanium samples were immersed in artificial saliva (AS), 1 M H₂O₂, 1 M H₂O₂ with catalase, 1000 ppmF NaF, 1 M H₂O₂ with 1000 ppmF NaF, or 9000 ppmF NaF (9000 ppmF NaF: pH 5.3, other solutions: pH 6.5) for 3 min. The electrochemical properties of the titanium samples were analyzed before and after the immersion procedures using a potentiostat. The amounts of titanium eluted into each solution were measured using inductively coupled plasma mass spectrometry. The post-immersion color changes (ΔE*ab) and gloss values of the titanium samples were determined using spectrophotometry. Moreover, the solution-treated titanium samples were subsequently immersed in AS and analyzed electrochemically at 1, 2, 3, 4, 6, 8, and 24 h.ResultsThe immersion of titanium in any of the solutions except 1000 ppmF NaF caused significant increases in corrosive and passive currents and significant reductions in polarization resistance. No titanium elution or color changes were observed, except when 9000 ppmF NaF was used. After immersion in AS, the electrochemical properties of all of the titanium samples, except the 9000 ppmF NaF-treated samples, recovered within 24 h.ConclusionsOne M H₂O₂ and 1000 ppmF NaF can be used alone or in combination in the clinical setting without causing significant titanium corrosion because the corrosive properties they induce is reversible. However, highly concentrated acidic fluorides can cause irreversible corrosion.     

Frequency of intake and amount of fluoride in milk for remineralisation of artificial caries on enamel and dentine: Ex vivo/in situ study

ObjectivesThis study analysed the effect of frequency of intake and amount of fluoride in milk on the remineralisation of artificial enamel and dentine caries lesions ex vivo/in situ.Materials and methodsPre-demineralised bovine enamel and dentine slabs were randomly allocated into 5 groups and fixed in removable appliances used by subjects for 7 days in each phase. Each treatment comprised milk containing 2.5 ppm fluoride daily (T1), or every other day (T2), 5.0 ppm F daily (T3), or every other day (T4) or no treatment (T5).ResultsEnamel alterations were quantified by surface hardness recovery (%SHR) and transversal microradiography (TMR), and in dentine by TMR only. Data were analysed by ANOVA and Tukey’s test (p < 0.05). For enamel, the highest %SHR was found for T1 and T3 compared to control, without significant differences between them. All groups showed positive values of ΔΔZ − T1 (247.3 ± 198.5); T2 (110.9 ± 303.2); T3 (226.0 ± 299.2); T5 (5.0 ± 288.0), except T4 (−274.5 ± 407.3). For dentine, the only group that presented remineralisation was T2 (350.0 ± 657.5).ConclusionsFluoridated milk daily seems to have higher remineralising effect on enamel than its use every other day. Dentine, does not seem to benefit from daily use of fluoridated milk.