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.     

Enhanced effect of nano-monetite hydrosol on dentin remineralization and tubule occlusion

ObjectivesWe aim to investigate the dentin tubule occlusion and remineralization potential of a novel nano-monetite hydrosol (nMH).MethodsFirst, nano-monetite hydrosol (nMH) was fabricated by homogeneous precipitation method. Then, the effectiveness of toothpaste with nMH on improving remineralization was evaluated by the measurement of tubule occluding ratio and acid-resistant stability compared with dentifrices comprising nano-hydroxyapatite hydrosol (nHH) and bioactive glass (BG). To explain this result, we studied the ions releasing and remineralization based on gelatin scaffold among nMH, nHH and BG. Finally, the cytotoxicity of these three minerals on Human dental pulp stem cells (HDPSCs) was evaluated.ResultsProcessing for more than 7 days, the toothpaste containing nMH exhibited the significant remineralization potential and acid-resistant compared with two commercial de-sensitive dentifrices comprising nHH and BG. In addition, cytotoxicity test resulted that nMH has good cell compatibility to HDPSCs below extracts concentration of 3.12 mg/mL.SignificanceSmall size, the release of Ca²⁺ and PO₄³⁻ with high concentration, strongly binding on dental surface, and fast transformation to HAp, were all needed in the preparation of effective dentin tubule occluding biomaterials.     

含锶锌黄长石涂层钛表面促进骨髓间充质干细胞成骨分化的初步研究

目的钛合金表面制备新型含锶锌黄长石（Sr-Ca₂ZnSi₂O₇,Sr-HT）涂层,初步评估其对骨髓间充质干细胞（BMMSCs）成骨分化等生物学行为的调控能力,用于指导新型种植体设计以促进骨结合效果。方法采用等离子喷涂法对钛合金表面进行Sr-HT涂层修饰,分别以锌黄长石（Ca₂ZnSi₂O₂,HT）以及羟磷灰石（HAp）涂层钛表面作为对照。扫描电镜观察涂层的表面结构,并使用电感耦合等离子体发射光谱仪（ICP-OES）检测表面涂层的离子释放情况。原代培养犬骨髓间充质干细胞（BMMSCs）并接种于材料表面,用免疫荧光法观察细胞在三种涂层表面的粘附铺展情况,ALP半定量检测和OCN蛋白表达免疫荧光法观察细胞在三种涂层表面的成骨分化情况。结果扫描电镜下观察,三种涂层表面均为凸凹不平的微米尺度结构,与HAp涂层相比,Sr-HT和HT组浸提液中含有锌离子,Sr-HT涂层还能够释放大量锶离子。BMMSCs在Sr-HT和HT涂层表面粘附能力、ALP活性和OCN蛋白表达均显著高于HAp对照组,其中Sr-HT组更明显。结论与传统HAp涂层相比,新型Sr-HT涂层可促进BMMSCs的粘附和成骨分化,其促进成骨分化的作用与Zn和Sr离子释放有关。     

Vibrational study of adsorbed phosphate ions on rhodium single crystal electrodes

The adsorption of H₂PO₄^? ions was studied on low Miller index rhodium single crystal electrodes by in situ FTIR spectroscopy. It is found that for Rh(1 0 0) and Rh(1 1 0), H₂PO₄^? ions are the major species at low potentials, but at higher potentials, some of the H₂PO₄^? ions undergo a potential induced deprotonation and probably there is a mixture of H₂PO₄^? and HPO₄^2? ions. On Rh(1 1 1) the deprotonation starts at very low potentials and at higher potentials the H₂PO₄^? is fully converted to HPO₄^2?. The behavior of the band center and of the band intensity with the applied potential was also analyzed. It is found that the adsorption increases from 0.08 V vs. a Pd–H₂ electrode up to 0.5 V and then it decreases when the OH starts to be adsorbed.     

Surface free energy of enamel treated with sodium hexametaphosphate,calcium and phosphate

ObjectiveThis study evaluated the capacity of sodium hexametaphosphate (HMP) at different concentrations to alter the surface properties of dental enamel in order to increase calcium and phosphate adsorption.DesignBovine enamel blocks (4 mm × 4 mm, n = 144, 12/group) were divided: 0%; 0.25%; 0.5%; and 1% HMP, followed or not by application of solutions containing Ca or Ca-PO₄, totaling 12 groups. The treatments were performed for 2 min, and the surface free energy (mN/m) was calculated by measuring the contact angles of three probing liquids (deionized water, diiodomethane and ethylene glycol), which was used to determine the polar and nonpolar components of the enamel surface. Calcium (Ca), phosphate (PO₄) and HMP in the solutions treatment solutions were analyzed before and after treatment. The data presented normal and homogeneous distribution and then were subjected to ANOVA, followed by Student-Newman Keuls’ test (p < 0.05).ResultsThe higher the% of HMP in the solutions, the greater HMP adsorption and more electron-donor sites on enamel surface were achieved (p < 0.05). Also, Ca adsorption was higher with increasing% HMP in the solutions (p < 0.05), which in turn reduced electron-donor sites on enamel surface. Increased Ca and PO₄ adsorption occurred at 0.5% and 1% HMP after treatment with Ca-PO₄ solution, resulting in a less electron-donor sites on surface when compared to the other treatments (P < 0.05).ConclusionsHMP leads to a more electron-donor sites on enamel surface, what promotes greater adsorption of Ca and PO₄ ions.     

Dual-functional adhesive containing amorphous calcium phosphate nanoparticles and dimethylaminohexadecyl methacrylate promoted enamel remineralization in a biofilm-challenged environment

ObjectiveThe cariogenic biofilm on enamel, restoration, and bonding interface is closely related to dental caries and composite restoration failure. Enamel remineralization at adhesive interface is conducive to protecting bonding interface and inhibiting secondary caries. This study intended to assess the remineralization efficiency of adhesive with dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP) on initial caries lesion of biofilm-coated enamel.MethodsArtificial initial carious lesion was created via 72-hour immersion in demineralization solution and cariogenic biofilm was formed after 24-hour culture of Streptococcus mutans (S. mutans). Specimens were then divided into 4 groups: enamel control, enamel treated with NACP, DMAHDM and NACP+DMAHDM respectively. Samples next underwent 7-day cycling, 4 h in BHIS (brain heart infusion broth containing 1 % sucrose) and 20 h in AS (artificial saliva) per day. The pH of BHIS was tested daily. So did the concentration of calcium and phosphate in BHIS and AS. Live/dead staining, colony-forming unit (CFU) count, and lactic acid production of biofilms were measured 7 days later. The enamel remineralization efficiency was evaluated by microhardness testing and transverse microradiography (TMR) quantitatively.ResultsEnamel of NACP+DMAHDM group demonstrated excellent remineralization effectiveness. And the NACP+DMAHDM adhesive released a great number of Ca²⁺ and PO₄^3- ions, increased pH to 5.81 via acid neutralization, decreased production of lactic acid, and reduced CFU count of S. mutans (P < 0.05).SignificanceThe NACP+DMAHDM adhesive would be applicable to preventing secondary caries, strengthening enamel-adhesive interface, and extending the lifespan of composite restoration.     

Effects of varied ionic calcium and phosphate on the proliferation, osteogenic differentiation and mineralization of human periodontal ligament cells in vitro

An S, Ling J, Gao Y, Xiao Y. Effects of varied ionic calcium and phosphate on the proliferation, osteogenic differentiation and mineralization of human periodontal ligament cells in vitro. J Periodont Res 2012; 47: 374–382. ©2011 John Wiley & Sons A/S Background and Objective: A number of bone‐filling materials containing calcium (Ca²⁺) and phosphate (P) ions have been used in the repair of periodontal bone defects; however, the effects that local release of Ca²⁺ and P ions has on biological reactions are not fully understood. In this study, we investigated the effects of various levels of Ca²⁺ and P ions on the proliferation, osteogenic differentiation and mineralization of human periodontal ligament cells (hPDLCs). Material and Methods: The hPDLCs were obtained using an explant culture method. Defined concentrations and ratios of ionic Ca²⁺ to inorganic P were added to standard culture and osteogenic induction media. The ability of hPDLCs to proliferate in these growth media was assayed using the Cell Counting Kit‐8. Cell apoptosis was evaluated by the fluorescein isothiocyanate–annexin V/propidium iodide double‐staining method. Osteogenic differentiation and mineralization were investigated by morphological observations, alkaline phosphatase activity and Alizarin Red S/von Kossa staining. The mRNA expression of osteogenic related markers was analysed using RT‐PCR. Results: Within the ranges of Ca²⁺ and P ion concentrations tested, we observed that increased concentrations of Ca²⁺ and P ions enhanced cell proliferation and formation of mineralized matrix nodules, whereas alkaline phosphatase activity was reduced. The RT‐PCR results showed that elevated concentrations of Ca²⁺ and P ions led to a general increase of Runx2 mRNA expression and decreased alkaline phosphatase mRNA expression, but gave no clear trend on osteocalcin mRNA levels. Conclusion: The concentrations and ratios of Ca²⁺ and P ions could significantly influence proliferation, differentiation and mineralization of hPDLCs. Within the range of concentrations tested, we found that the combination of 9.0 mm Ca²⁺ ions and 4.5 mm P ions were the optimal concentrations for proliferation, differentiation and mineralization in hPDLCs.     

Antibacterial,remineralising and matrix metalloproteinase inhibiting scandium-doped phosphate glasses for treatment of dental caries

ObjectivesAntibiotic resistance is increasingly a growing global threat. This study aimed to investigate the potential use of newly developed scandium-doped phosphate-based glasses (Sc-PBGs) as an antibacterial and anticariogenic agent through controlled release of Sc³⁺ ions.MethodsSc-PBGs with various calcium and sodium oxide contents were produced and characterised using thermal and spectroscopic analysis. Degradation behaviour, ion release, antibacterial action against Streptococcus mutans, anti-matrix metalloproteinase-2 (MMP-2) activity, remineralisation potential and in vivo biocompatibility were also investigated.ResultsThe developed glass system showed linear Sc³⁺ ions release over time. The released Sc³⁺ shows statistically significant inhibition of S. mutans biofilm (1.2 log₁₀ CFU reduction at 6 h) and matrix metalloproteinase-2 (MMP-2) activity, compared with Sc-free glass and positive control. When Sc-PBGs were mounted alongside enamel sections, subjected to acidic challenges, alternating hyper- and hypomineralisation layers consistent with periods of re- and demineralisation were observed demonstrating their potential remineralising action. Furthermore, Sc-PBGs produced a non-toxic response when implanted subcutaneously for 2 weeks in Sprague Dawley rats.SignificanceSince Sc³⁺ ions might act on various enzymes essential to the biological mechanisms underlying caries, Sc-PBGs could be a promising therapeutic agent against cariogenic bacteria.     

Influence of calcium, phosphate and complexing substances on inorganic pyrophosphatase in mineralizing hamster molars.

The influence of calcium and phosphorus on PP_i-ase activity in mineralizing hamster molars was studied in the presence and absence of several complexing substances. These complexing substances inhibited the PP_i-ase activity. Only Zn²⁺ completely reversed this inhibition. The Ca²⁺ stimulation of the PP_i-ase was substrate-dependent with an optimal activity at a Ca:PP_i ratio of 1. At higher concentrations, Ca²⁺ was strongly inhibitory, possibly by forming neutral salts with PP_i. The influence of complexing substances on the enzyme was modified by Ca²⁺, which changes the mol Ca²⁺:PP_i ratio or competes slightly with Zn²⁺ for the complexing agent. There was a small inhibition of the PP_i-ase activity by P_i which was not influenced by the substrate used (PP_i^4?, Mg-PP_i^2?or Ca-PP_i^2?. P_i can reverse the inhibiting effects of complexing substances to a small extent, except for stronger inhibitions obtained for 0.1 mM EHDP and 2mM Cl₂ MDP. These small in-vitro effects of Ca²⁺ and P_i on the PP_i-ase activity could not explain the great changes in PP_i-ase activity in mineralizing molars during normal development and at P_i depletion. This supports a stimulating role for the PP_i-ase in mineralization. It was concluded that, during mineralization, different Ca²⁺ and P_i concentrations can modify the inhibitory effects of the complexing substances on the PP_i-ase only to a very small extent.     

Electrochemistry of human enamel: Selectivity to potassium in solutions containing calcium or phosphate ions

Further studies have been made at 25 ± 1 °C of the steady-state electromotive forces (emfs) developed across the enamel caps of whole teeth and synthetic hydroxyapatite membranes in concentration cells using KH₂PO₄, K₂HPO₄ and K₃PO₄ solutions at their natural pH values, and of the variation in the emf of enamel and Permutit C20 cation-exchange membranes in 0.100/0.010 M KCl concentration cells when small concentrations of calcium and phosphate are added separately (as CaCl₂ and K₂HPO₄) to both KCl solutions. Over the concentration range examined, the cationic selectivity of both enamel and HA cells with the potassium phosphate gradients was always greater than that with KCl gradients, the selectivity with K₂HPO₄ and K₃PO₄ gradients being virtually ideal. The results thus appear to substantiate the inferences drawn in previous work that (a) the mineral fraction is responsible for the observed effects and (b) that enamel is a “non-leaky” membrane. In KCl concentration cells with small calcium additions, a marked decrease in the membrane potential was observed which, by comparison with the results for the synthetic cation-exchange membrane C20, is attributed to the preferential selectivity of the enamel for Ca²⁺ ions under these conditions. With small concentrations of added phosphate, a decrease in potential was observed which could be ascribed to changes in the K⁺ ion gradient in the cells.     

The effect of magnolol on Ca2+ homeostasis and its related physiology in human oral cancer cells

ObjectiveMagnolol, a polyphenol compound from herbal medicines, was shown to alter physiology in various cell models. However, the effect of magnolol on Ca²⁺ homeostasis and its related physiology in oral cancer cells is unclear. This study examined whether magnolol altered Ca²⁺ signaling and cell viability in OC2 human oral cancer cells.MethodsCytosolic Ca²⁺ concentrations ([Ca²⁺]_i) in suspended cells were measured by using the fluorescent Ca²⁺-sensitive dye fura-2. Cell viability was examined by 4-[3-[4-lodophenyl]-2-4(4-nitrophenyl)-2H-5-tetrazolio-1,3-benzene disulfonate] water soluble tetrazolium-1 (WST-1) assay.ResultsMagnolol at concentrations of 20–100 μM induced [Ca²⁺]_i rises. Ca²⁺ removal reduced the signal by approximately 50%. Magnolol (100 μM) induced Mn²⁺ influx suggesting of Ca²⁺ entry. Magnolol-induced Ca²⁺ entry was partially suppressed by protein kinase C (PKC) regulators, and inhibitors of store-operated Ca²⁺ channels. In Ca²⁺-free medium, treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) abolished magnolol-evoked [Ca²⁺]_i rises. Conversely, treatment with magnolol abolished BHQ-evoked [Ca²⁺]_i rises. Inhibition of phospholipase C (PLC) with U73122 partially inhibited magnolol-induced [Ca²⁺]_i rises. Magnolol at 20–100 μM decreased cell viability, which was not reversed by pretreatment with the Ca²⁺ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM).ConclusionsTogether, in OC2 cells, magnolol induced [Ca²⁺]_i rises by evoking partially PLC-dependent Ca²⁺ release from the endoplasmic reticulum and Ca²⁺ entry via PKC-sensitive store-operated Ca²⁺ entry. Magnolol also caused Ca²⁺-independent cell death. Therefore, magnolol-induced cytotoxicity may not be involved in activation mechanisms associated with intracellular Ca²⁺ mobilization in oral cancer cells.     

Effect of mono- and divalent ions on diffusion and binding in bovine tooth enamel

A radiochemical method was used to determine quantitatively the effect of RbCl, CaCl₂ and MgCl₂ on the transport of [³H]-sorbitol, [¹⁴C]-glycerol, ⁴⁵Ca²⁺, ³⁶Cl^? and ⁸⁶Rb⁺ through dental enamel. The findings indicate that the transport of ⁴⁵Ca²⁺ is influenced strongly by surface exchange reactions. The influence of Ca²⁺ and Mg²⁺ on the transport of ⁸⁶Rb⁺ and ³⁶Cl^? indicates that, at a concentration of ~10mmol/l, these ions alter the fixed charge of enamel from negative to less negative, or positive values. Previously adsorbed ⁴⁵Ca²⁺ ions are desorbed at higher Ca²⁺ and Mg²⁺ concentrations. Rb⁺ ions at 10 mmol/l have no such effect. The results indicate that Ca²⁺ and Mg²⁺ can be adsorbed reversibly on the crystal surfaces or in their Stern layers in the pores of dental enamel.     

The impact of nitric oxide on calcium homeostasis in PE/CA-PJ15 cells

ObjectiveNitric oxide (NO) production and Ca²⁺ homeostasis are key determinants for the control of many cell functions. NO is known to be a mediator of Ca²⁺ homeostasis in a highly complex and cell-specific manner and although Ca²⁺ homeostasis has been explored in human oral cancer cells, the exact mechanisms are not completely understood. In this study we investigated the impact of exogenous NO on [Ca²⁺]_c homeostasis in PE/CA-PJ15 cells.DesignCells were treated with S-nitrosocysteine as NO-donor and the determinations of cytosolic Ca²⁺ concentrations were performed using FURA-2 AM. Carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone (FCCP) and oligomycin were used to challenge mitochondrial functionality, whereas thapsigargin (TG) and La³⁺ were employed to perturb intracellular calcium levels.ResultsNO derived from S-nitrosocysteine (CySNO) induced a dose-dependent reduction of cytosolic calcium [Ca²⁺]_c whereas oxy-haemoglobin (oxyHb) completely counteracted this effect. Subsequently, we assessed possible relationships between NO and cellular structures responsible for Ca²⁺ homeostasis. We found that uncoupling of mitochondrial respiration with carbonyl-cyanide-4-(trifluoromethoxy)-phenylhydrazone (FCCP) and oligomycin strongly reduced the effect of NO on [Ca²⁺]_c. Moreover, we found that during this mitochondrial energetic deficit, the effect of NO on [Ca²⁺]_c was also reduced in the presence of La³⁺ or thapsigargin.ConclusionsNO induces a concentration-dependent [Ca²⁺]_c reduction in PE/CA-PJ15 human oral cancer cells and potentiates mitochondrial Ca²⁺ buffering in the presence of TG or La³⁺.Further, we show that exogenous NO deregulates Ca²⁺ homeostasis in PE/CA-PJ15 cells with fully energized mitochondria.     

Interfacial Characterization of Dentin Conditioned with Chitosan Hydroxyapatite Precursor Nanocomplexes Using Time-of-flight Secondary Ion Mass Spectrometry

IntroductionThe purpose of this study was to evaluate the effect of chitosan-hydroxyapatite precursor (C-HA) nanocomplex conditioning on the chemical modifications at the tricalcium silicate sealer-dentin interface using time-of-flight secondary ion mass spectrometry.MethodsDentin slabs from human premolar root dentin were prepared, demineralized, and randomly distributed between control and C-HA nanocomplex conditioned groups. Tricalcium silicate sealer was applied, and the slabs were allowed to set in 100% humidity for 10 days. The cross-sectional area was exposed, and the sealer-dentin interface was characterized for chemical/ultrastructural evaluation with time-of-flight secondary ion mass spectrometry and transmission electron microscopy, respectively.ResultsChemical analysis revealed the presence of an ion-rich layer constituted of abundant phosphates (PO₂⁻, PO₃⁻, and PO₄⁻), hydroxide (OH⁻), and chitosan fragments (C₂H₄NO⁻, C₃H₄NO₂^−, C₂H₅O₂⁺, C₂H₆NO⁺, C₄H₆NO₂⁺, C₅H₆NO⁺, and C₅H₅O₂⁺) on the dentin surface at the sealer-dentin interface and subsurface dentin after conditioning with C-HA nanocomplexes. In contrast, a decreased interfacial presence of calcium (Ca⁺) and calcium phosphates (CaPO₂⁺, CaPO₃⁺, CaPO₄⁺, and Ca₂PO₃⁺) and the absence of phosphate fragments in the control were noted. Ultrastructural evaluation showed an interfacial layer (<1 μm) with interrupted mineral aggregates in the controls as opposed to a continuous (5 μm) mineral layer formation on the conditioned dentin.ConclusionsC-HA nanocomplex conditioning of dentin before tricalcium silicate sealer application resulted in a chemically modified dentin substrate with an ion-rich layer consisting of phosphate, calcium, calcium phosphates, and chitosan that chemically modified the dentin surface/subsurface.     

An infrared and x-ray diffractometric study of the incorporation of fluoride into hydorxyapatite under conditions of the cyclic variation of pH.

The solid products from the interaction of hydroxyapatite with supernatant solutions of sodium fluoride under conditions where the pH of the supernatant have been cyclically varied between the limits pH 4 and pH 7 were examined by chemical analysis, infrared spectrophotometry, X-ray diffraction and thermogravimetry. During the initial lowering of the pH from 7 to 4, there is a dissolution of the hydroxyapatite, followed or accompanied by a precipitation of calcium fluoride formed by reaction of the Ca²⁺ ions released with supernatant fluoride ions. On raising the pH from 4 to 7, this latter phase reacts with supernatant H₂PO₄^? ions to form fluoroapatite. Subsequent cyclic variations in the pH increasingly yield a more homogeneous product. The efficiency of fluoride incorporation into the hydroxyapatite depends on the number of complete fluctuation cycles employed. The results are discussed in terms of the dynamic equilibrium existing at the solid-liquid interface.     

Calcium and phosphate ion releasing composite: Effect of pH on release and mechanical properties

ObjectivesSecondary caries and restoration fracture are the two main challenges facing tooth cavity restorations. The objective of this study was to develop a composite using tetracalcium phosphate (TTCP) fillers and whiskers to be stress-bearing, and to be “smart” to increase the calcium (Ca) and phosphate (PO₄) ion release at cariogenic pH.MethodsTTCP was ball-milled to obtain four different particle sizes: 16.2, 2.4, 1.3, and 0.97 μm. Whiskers fused with nano-sized silica were combined with TTCP as fillers in a resin. Filler level mass fractions varied from 0 to 75%. Ca and PO₄ ion releases were measured vs. time at pH of 7.4, 6, and 4. Composite mechanical properties were measured via three-point flexure before and after immersion in solutions at the three pH.ResultsTTCP composite without whiskers had flexural strength similar to a resin-modified glass ionomer (Vitremer) and previous Ca–PO₄ composites. With whiskers, the TTCP composite had a flexural strength (mean ± S.D.; n = 5) of (116 ± 9) MPa, similar to (112 ± 14) MPa of a stress-bearing, non-releasing hybrid composite (TPH) (p > 0.1). The Ca release was (1.22 ± 0.16) mmol/L at pH of 4, higher than (0.54 ± 0.09) at pH of 6, and (0.22 ± 0.06) at pH of 7.4 (p < 0.05). PO₄ release was also dramatically increased at acidic pH. After immersion, the TTCP–whisker composite matched the strength of TPH at all three pH (p > 0.1); both TTCP–whisker composite and TPH had strengths about threefold that of a releasing control.SignificanceThe new TTCP–whisker composite was “smart” and increased the Ca and PO₄ release dramatically when the pH was reduced from neutral to a cariogenic pH of 4, when these ions are most needed to inhibit caries. Its strength was two- to threefold higher than previously known Ca–PO₄ composites and resin-modified glass ionomer. This composite may have the potential to provide the necessary combination of load-bearing and caries-inhibiting capabilities.     

A method for determining concentrations of calcium complexes in human parotid saliva by gel filtration

Saliva was collected at two flow rates (approx. 0.15 ml/min, pH 6.6 and 1.5 ml/min, pH 7.4) from one subject. The saliva was gel-filtrated at 37 °C in a column, equilibrated and eluted with a buffer containing Ca²⁺ at a concentration equal to that of saliva. Three peaks containing the Ca complexes were identified as proteins (I), phosphate, citrate, lactate (II) and bicarbonate (III). In the weakly stimulated saliva, the total Ca was 0.61 mmol/l, distributed as Ca²⁺ (45 per cent), bound to proteins (10 per cent), complexes to the inorganic ions (35 per cent) and to the organic acids (10 per cent). For strongly stimulated saliva (total Ca 1.15 mmol/l), the corresponding figures were 43.5, 8.7, 40 and 7.8 per cent respectively. The higher total Ca concentration in the strongly stimulated saliva was recovered mainly as Ca²⁺ and Ca complexed to carbonate.     

Ion release and enamel remineralizing potential of miswak,propolis and chitosan nano-particles based dental varnishes

Purpose

Natural products can have an important role in caries control through their inherent biological abilities.

Ion release characteristics,precipitate formation and sealing ability of a phosphate glass–polycaprolactone-based composite for use as a root canal obturation material

ObjectivesThe filling material used to obturate root canal systems during the common dental procedure, root canal treatment, has popularly involved gutta-percha (GP) in one of its many forms for almost a 100 years. An optimal root filling material should provide a predictable seal, inhibit or kill residual bacteria, prevent re-contamination and facilitate periapical healing. Although the goal of obturation is stated as the creation of a “seal”, its precise role still remains elusive and the seal offered suspect.The primary goal of the study was to develop a novel polycaprolactone/phosphate glass composite deliverable as a root filling and capable of releasing ionic species to enable a predictable seal in an aqueous environment.Materials and methodsDifferent compositions of polycaprolactone–iron phosphate glass (Fe₂O₃ 1, 3 and 5 mol%) composites were produced and delivered into an ex vivo root canal model. Standardized root canals were prepared in extracted human teeth. The teeth were examined for root filling adaptation and precipitate formation (SEM), ion release (Na⁺, Ca²⁺, PO₄^3?, P₂O₇^4?, P₃O₉^3?, and P₅O₁₀^5?), and sealing ability. The experiments were controlled with teeth obturated with contemporary GP and a conventional zinc-oxide/eugenol sealer.ResultsAdaptation of the experimental material was statistically significantly better than the GP control groups. Precipitate formation was noted in some specimens but all released various ionic species in an inverse proportion to the iron oxide concentration. The experimental material exhibited significantly (P < 0.001) less leakage after 7 days immersion in saline compared with those not immersed, or the control GP group.SignificancePCL–phosphate glass composites showed good potential as a root filling material capable of producing a seal in an aqueous environment without a sealer.