Impact of Dentin Substrate Modification with Chitosan-Hydroxyapatite Precursor Nanocomplexes on Sealer Penetration and Tensile Strength

IntroductionThe purpose of this study was to evaluate the effect of dentin conditioning with chitosan-hydroxyapatite precursor (C-HA) nanocomplexes on the depth of tricalcium silicate sealer penetration into dentinal tubules and ultimate tensile strength (UTS).Methodssurface charge and size distribution for C-HA nanocomplex formulation was evaluated followed by bioactivity assessment of standardized films of C-HA nanocomplexes (n = 15) incubated in simulated body fluid. Mineralization potential was assessed with X-ray diffraction and Fourier-transform infrared spectroscopy, whereas scanning electron microscopy was used for ultrastructural evaluation. Static water contact angles and UTS were measured on dentin discs (n = 2/group) and dentin beams (n = 10/group) treated with/without sodium hypochlorite/EDTA and C-HA nanocomplex conditioning. In phase 2, the depth of sealer penetration after C-HA nanocomplex conditioning was evaluated using fluorescent imaging (n = 12/group). The percent area penetration and mean/maximum penetration depth were calculated at 4- and 6-mm levels from the root apex. Data from contact angle measurements, mechanical testing, and penetration assessment parameters were subjected to the independent samples t test with a significance level set at P < .05.ResultsA formulation of C-HA nanocomplexes (2 mg/mL) was chosen as a polyanionic, hydrophilic, nonaggregating concentration having bioactivity potential established through the formation of phosphate/carbonate bonds and the crystalline nature of the formed minerals. A significantly lower contact angle and higher UTS were registered for the C-HA nanocomplex–conditioned group (P < .05). Statistically significant (P < .05) greater sealer penetration was recorded at the 4-mm level for all assessment parameters and percent area penetration at 6 mm for the C-HA nanocomplex group.ConclusionsC-HA nanocomplex conditioning enhances dentin surface wettability to facilitate greater tricalcium silicate sealer penetration and UTS of dentin.     

Calcium phosphate formation in gelatin matrix using free ion precursors of Ca2+ and phosphate ions

ObjectivesHydroxyapatite (HAp)/gelatin (GEL) nanocomposite has been developed as a bone substitute. The nanocomposite formation in the GEL matrix is greatly affected by the reaction between Ca²⁺ and phosphate ions. The mineralization of GEL macromolecules was investigated through a co-precipitation of calcium phosphates (Ca-P) by using free ions of Ca²⁺ and phosphate ions, Pi. The purpose of this study was to prepare a dense HAp/GEL nanocomposite through a free ion production process.MethodsFree ionic calcium, Ca²⁺, was produced through electrodialysis process using a cation membrane (CMV). Triprotic acid ions were diffused through an anion membrane (AMV) from an aqueous solution of H₃PO₄. The HAp/GEL nanocomposite was prepared by the co-precipitation process. As a reference material for comparison, Ca(OH)₂ and H₃PO₄ were used for the preparation of a HAp/GEL nanocomposite.ResultsThe dense compact body of dried Ca-P/GEL nanocomposite was obtained through the fine chemical reaction of Ca²⁺ and Pi. The free calcium ion Ca²⁺, diffused from the CMV of the cation reactor greatly affected the formation of Ca–P phase. Phosphate ion species diffused through the AMV in the anion reactor definitely influenced the reaction with Ca²⁺. For the formation of the Ca–P phase in the GEL matrix, the organic–inorganic interaction was analyzed using FT-IR. The crystal growth of HAp in the GEL matrix increased with the increase of GEL from XRD, FT-IR and TEM.SignificanceThe mineralization reaction in GEL macromolecules was critically influenced by the free ions of Ca²⁺ and inorganic phosphate ions, Pi. The interaction between Ca²⁺ and Pi in the GEL matrix was very fine compared to the HAp/GEL nanocomposite prepared from Ca(OH)₂ and H₃PO₄ with the GEL. The dense compact body of HAp/GEL nanocomposite was obtained for an artificial bone application.     

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.

     

A mechanism for dental caries based on chemical processes and diffusion phenomena during in-vitro caries simulation on human tooth enamel.

Artificial carious lesions were produced in a range of lactate buffers containing disodium-methane-hydroxy-diphosphonate and the depths of the lesions were measured. The depth of the body of the lesion depended on the calculated concentration of un-ionized lactic acid (HL), and the innermost boundary depended on HL concn. and pH. Apparent diffusion coefficients of the order 10^?10cm²/s were calculated from the boundary movement. A mechanism is proposed for the caries process. Diffusion, predominantly of the un-ionized chemical species HL, H₃PO₄, CaHPO₄, Ca(H₂PO₄)₂ and CaL₂ occurs through the intercrystalline and interprismatic pores of enamel filled with water and protein. Dissolution takes place throughout the lesion by H⁺ and L^? as HL dissociates. The outer enamel surface is partly protected by reversible adsorption of suitable chemical species.     

Functional and molecular characterization of transmembrane intracellular pH regulators in human dental pulp stem cells

ObjectiveHomeostasis of intracellular pH (pH_i) plays vital roles in many cell functions, such as proliferation, apoptosis, differentiation and metastasis. Thus far, Na⁺-H⁺ exchanger (NHE), Na⁺-HCO₃⁻ co-transporter (NBC), Cl⁻/HCO₃⁻ exchanger (AE) and Cl⁻/OH⁻ exchanger (CHE) have been identified to co-regulate pH_i homeostasis. However, functional and biological pH_i-regulators in human dental pulp stem cells (hDPSCs) have yet to be identified.DesignMicrospectrofluorimetry technique with pH-sensitive fluorescent dye, BCECF, was used to detect pH_i changes. NH₄Cl and Na⁺-acetate pre-pulse were used to induce intracellular acidosis and alkalosis, respectively. Isoforms of pH_i-regulators were detected by Western blot technique.ResultsThe resting pH_i was no significant difference between that in HEPES-buffered (nominal HCO₃⁻-free) solution or CO₂/HCO₃-buffered system (7.42 and 7.46, respectively). The pH_i recovery following the induced-intracellular acidosis was blocked completely by removing [Na⁺]_o, while only slowed (−63%) by adding HOE694 (a NHE1 specific inhibitor) in HEPES-buffered solution. The pH_i recovery was inhibited entirely by removing [Na⁺]_o, while adding HOE 694 pulse DIDS (an anion-transporter inhibitor) only slowed (−55%) the acid extrusion. Both in HEPES-buffered and CO₂/HCO₃-buffered system solution, the pH_i recovery after induced-intracellular alkalosis was entirely blocked by removing [Cl⁻]_o. Western blot analysis showed the isoforms of pH_i regulators, including NHE1/2, NBCe1/n1, AE1/2/3/4 and CHE in the hDPSCs.ConclusionsWe demonstrate for the first time that resting pH_i is significantly higher than 7.2 and meditates functionally by two Na⁺-dependent acid extruders (NHE and NBC), two Cl⁻-dependent acid loaders (CHE and AE) and one Na⁺-independent acid extruder(s) in hDPSCs. These findings provide novel insight for basic and clinical treatment of dentistry.     

Present and future of glass-ionomers and calcium-silicate cements as bioactive materials in dentistry: Biophotonics-based interfacial analyses in health and disease

Objective

Since their introduction, calcium silicate cements have primarily found use as endodontic sealers, due to long setting times. While similar in chemistry, recent variations such as constituent proportions, purities and manufacturing processes mandate a critical understanding of service behavior differences of the new coronal restorative material variants. Of particular relevance to minimally invasive philosophies is the potential for ion supply, from initial hydration to mature set in dental cements. They may be capable of supporting repair and remineralization of dentin left after decay and cavity preparation, following the concepts of ion exchange from glass ionomers.

Methods

This paper reviews the underlying chemistry and interactions of glass ionomer and calcium silicate cements, with dental tissues, concentrating on dentin–restoration interface reactions. We additionally demonstrate a new optical technique, based around high resolution deep tissue, two-photon fluorescence and lifetime imaging, which allows monitoring of undisturbed cement–dentin interface samples behavior over time.

Results

The local bioactivity of the calcium-silicate based materials has been shown to produce mineralization within the subjacent dentin substrate, extending deep within the tissues. This suggests that the local ion-rich alkaline environment may be more favorable to mineral repair and re-construction, compared with the acidic environs of comparable glass ionomer based materials.

Significance

The advantages of this potential re-mineralization phenomenon for minimally invasive management of carious dentin are self-evident. There is a clear need to improve the bioactivity of restorative dental materials and these calcium silicate cement systems offer exciting possibilities in realizing this goal.     

钛表面接枝溴代十六烷后的杀菌效果研究

目的 在钛表面沉积透明质酸(HA)和壳聚糖(CHI)聚电解质多层膜,并用溴代十六烷对CHI上的氨基季铵化,以评价其杀菌效果.方法 在碱化处理过的钛片上吸附带正电荷的聚乙烯亚氨(PEI),再用层层自组装的方法在钛表面交替沉积带负电荷的HA和带正电荷的CHI,并用溴代十六烷(C16H33Br)对CHI上的氨基季铵化,形成Ti-PEI-(HA-CHI)20-N+(C16H33)3Br涂层,扫描电子显微镜(SEM)对涂层断面进行表征;以纯钛为对照组,Ti-PEI-(HA-CHI)20和Ti-PEI-(HA-CHI)20-N+(C16H33)3Br-为实验组,分别在其表面进行变形链球菌(S.m)培养24h后用荧光显微镜和SEM检测钛片表面的细菌活性.结果 SEM显示聚电解质多层膜已沉积到钛片表面并具有一定的厚度.荧光显微镜显示纯钛表面有大量的活细菌,Ti-PEI-(HA-CHI)20上细菌数量较少,且有部分死菌;而Ti-PEI-(HA-CHI)20-N+(C16H33)3Br-上细菌几乎全为死菌.SEM结果显示纯钛、Ti-PEI-(HA-CHI)20、Ti-PEI-(HA-CHI)20-N+(C16H33)3Bf 3组钛片上的细菌数量依次减少.结论 钛表面沉积HA/CHI聚电解质多层膜,并对多层膜中的CHI季铵化后,其表面具有显著的杀菌作用.     

Preparation,characterization and electrocatalytic properties of polynuclear mixed-valent ruthenium oxide/hexacyanoruthenate film modified electrodes

Polynuclear mixed-valent ruthenium oxide/ruthenocyanide (ruthenium oxide/hexacyanoruthenate or mvRuO/RuCN) films were prepared using consecutive cyclic voltammetry directly from the mixing of Ru³⁺ and Ru(CN)₆^4? ions from solutions of two divalent cations (Ba²⁺ and Ca²⁺), and seven monovalent cations (H⁺, Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, and Ga⁺). The films exhibited three redox couples with Ba(NO₃)₂ or BaCl₂ aqueous solutions, and the formal potentials of the redox couples showed a cation and pH effect. An electrochemical quartz crystal microbalance (EQCM), cyclic voltammetry, UV–visible spectroscopy, and the stopped-flow method (SFM) were used to study the growth mechanism of the mvRuO/RuCN films. The results indicated that the redox process was confined to the immobilized ruthenium oxide/ruthenocyanide. The EQCM results showed a Ba²⁺ ion exchange reaction for the two most negative redox couples. The electrocatalytic reduction properties of SO₅^2?, and S₂O₈^2? by the ruthenium oxide/ruthenocyanide films were determined. The electrocatalytic oxidation of NADH and dopamine were also determined, and revealed two different types of properties. The electrocatalytic oxidations of SO₃^2?, S₂O₃^2?, and N₂H₄ were also investigated. The electrocatalytic reactions of the ruthenium oxide/ruthenocyanide films were investigated using the rotating ring-disk electrode method.     

Effects of Intracanal Antimicrobials on Viability and Differentiation of Stem Cells From the Apical Papilla: An In Vitro Study

BackgroundRecent studies have indicated that intracanal antimicrobials used to disinfect the root canal in regenerative endodontic therapies (RETs) may be cytotoxic to stem cells from the apical papilla (SCAP), leading to inconsistent treatment outcomes. However, the effects of intracanal antimicrobial agents on the odontogenic differentiation capacity of SCAP at sub-lethal concentrations have not been investigated. The aim of this study was to determine the effects of intracanal antimicrobials on SCAP viability and odontogenic differentiation capacity using a clinically relevant concentration range (0.1–0.8 mg/mL).MethodsImmature human third molars were collected from 71 patients and the apical papillae were harvested to form single-cell suspensions. The cytotoxic effects of intracanal antimicrobials including double antibiotic paste (DAP), triple or modified-triple antibiotic paste (TAP or MTAP), and calcium hydroxide (Ca(OH)₂) on STRO-1⁺ SCAP were assessed using AlamarBlue and Live/Dead assays after exposing cells to treatment groups for 7 days at 0.1 to 0.8 mg/mL. The odontogenic differentiation potential of STRO-1⁺ SCAP was evaluated by immunocytochemistry staining of dentin matrix protein-1 and dentin sialophosphoprotein expression.ResultsAll concentrations of TAP significantly reduced STRO-1⁺ SCAP viability and odontogenic differentiation (P < .001), whereas no DAP concentrations were significantly cytotoxic. Ca(OH)₂ and MTAP concentrations below 0.4 mg/mL and 0.2 mg/mL, respectively, did not significantly reduce viability. The DAP, MTAP, and Ca(OH)₂ did not significantly impact the odontogenic differentiation capacity of STRO-1⁺ SCAP.ConclusionThe varying effects of intracanal antimicrobials on STRO-1⁺ SCAP in vitro suggest amendments to the current root canal disinfection protocol may improve the success of RETs.     

Dentin collagen denaturation status assessed by collagen hybridizing peptide and its effect on bio-stabilization of proanthocyanidins

ObjectiveTo assess dentin collagen denaturation from phosphoric acid and enzyme treatments using collagen hybridizing peptide (CHP) and to investigate the effect of collagen denaturation on bio-stabilization promoted by proanthocyanidins (PA).MethodsHuman molars were sectioned into 7-µm-thick dentin films, demineralized, and assigned to six groups: control with/without PA modification, H₃PO₄-treated collagen with/without PA modification, enzyme-treated collagen with/without PA modification. PA modification involved immersing collagen films in 0.65% PA for 30 s. H₃PO₄ and enzyme treatments were used to experimentally induce collagen denaturation, which was quantitated by fluorescence intensity (FI) from the fluorescently-conjugated-CHP (F-CHP) staining (n = 4). FTIR was used to characterize collagen structures. All groups were subject to collagenase digestion to test the bio-stabilization effect of PA on denatured collagen using weight loss analysis and hydroxyproline assay (n = 6). Data were analyzed using two-factor ANOVA and Games-Howell post hoc tests (α = 0.05).ResultsFTIR showed collagen secondary structural changes after denaturation treatments and confirmed the incorporation and cross-linking of PA in control and treated collagen. F-CHP staining indicated high-degree, medium-degree, and low-degree collagen denaturation from H₃PO₄-treatment (FI = 83.22), enzyme-treatment (FI = 36.54), and control (FI = 6.01) respectively. PA modification significantly reduced the weight loss and hydroxyproline release of all groups after digestion (p < 0.0001), with the results correlated with FI values at r = 0.96–0.98.SignificanceA molecular method CHP is introduced as a sensitive technique to quantitate dentin collagen denaturation for the first time. PA modification is shown to effectively stabilize denatured collagen against collagenase digestion, with the stabilization effect negatively associated with the collagen denaturation degree.     

The state of calcium and inorganic orthophosphate in human saliva

The state of calcium and inorganic orthophosphate was investigated in resting parotid saliva and in stimulated parotid, submaxillary and whole saliva. Macromolecular binding was determined utilizing ultrafiltration procedures. Ionized calcium and phosphate in the ultrafiltrates were calculated on the basis of chemical analyses and considering the formation of the ion pairs CaHPO₄^o, CaH₂PO₄⁺ and CaHCO₃⁺. Mean findings showed that 85 per cent of the calcium in resting parotid saliva was ionized, while 8 per cent was bound to macromolecules and 6 per cent in ion pairs. In stimulated secretions, the ionized calcium ranged from 45 per cent (submaxillary saliva) to 54 per cent (mixed whole saliva) of total calcium. The macromolecular bound fraction accounted for 30–43 per cent while ion pairs bound 12–17 per cent of the calcium. Mean concentrations of ionized calcium were 0.74, 0.49, 0.76 and 0.59 mM respectively for the four types of saliva. Ultrafiltrability of inorganic orthophosphate ranged from 66 to 70 per cent in stimulated salivas and was over 90 per cent in resting parotid saliva. The ultrafiltrable phosphate was almost fully ionized because only 1–2 per cent was complexed with calcium. Mean concentrations of ionized orthophosphate were 6.58,2.59,2.08 and 2.53 mM respectively for the four types of saliva.     

Effect of topically applied silver compounds on the demineralisation of hydroxyapatite

ObjectivesThis study investigates the demineralization inhibitory mechanisms of AgNO₃, AgF and silver diamine fluoride (SDF) using a previously used hydroxyapatite (HAP) caries demineralization model system.MethodsHAP discs were allocated into three groups (n = 3) and immersed in demineralization solution (buffered pH 4.0, 0.1 mol/L acetic acid) for 4 h. Each disc was treated topically with either 3.16 M AgNO₃, 3.16 M AgF or 3.16 M SDF using a micro-brush. The discs were then demineralized for a further 4 h. Calcium, silver, and fluoride ion selective electrodes (ISEs) were used to monitor the changes in each ion concentration at 1 min intervals throughout. Demineralization inhibition was calculated as the percentage reduction in the rate of calcium ion loss from HAP (PRCL_HAP). Characterization of similarly treated HAP powder was carried out with Magic Angle Spinning-Nuclear Magnetic ResonanceResultsThe mean PRCL_HAP for each treatment group was; AgF (72.3 + 4.8%), SDF (69.7 + 5.3%) and AgNO₃ (14.9 + 2.7%). Ag₃PO₄ was detected in all HAP powders. CaF₂ and fluorohydroxyapatite (FHA) were detected only in powders treated with either AgF or SDF.The demineralization inhibitory efficacy of topically applied AgNO₃ results from the formation of a Ag₃PO₄ barrier. Whereas, the demineralization inhibitory efficacy of topically applied AgF, and SDF, results from the formation of a barrier composed of Ag₃PO₄, CaF₂, and FHA.SignificanceIn addition to their anti-microbial properties, clinical topical application of silver compounds for caries preventative treatment is due to their ability to form acid-resistant barriers composed of silver phosphate. When fluoride is present, this barrier also contains CaF₂ and FHA, additionally protecting the mineral.     

Improved two-step anodization technique for ordered porous anodic aluminum membranes

We report on an improved two-step anodization technique through combining the first hard anodization in C₂H₂O₄ with the second mild anodization in H₃PO₄, which successfully overcome the drawbacks of irregular top surfaces in the conventional two-step hard anodization in C₂H₂O₄ and disordered pore arrays in the two-step mild anodization in H₃PO₄. The key success of our method is the strong guidance effect of the first hard anodization on the second mild anodization. Highly-ordered (both top and bottom surfaces) porous anodic aluminum (PAA) membranes with interpore spacing from 220 to 350 nm have been realized under anodizing voltages from 100 to 150 V. The interpore spacing is only determined by the first anodizing voltage, while the pore diameter can be manipulated in the second step by adding ethanol in the H₃PO₄ electrolyte, changing the H₃PO₄ bath temperature, and altering the second anodizing voltage. The bath temperature for the steady growth of ordered structures can be expanded up to 20 °C, from which the average activation energy can be yielded. The present novel two-step anodization approach is simple, efficient, and cost-effective. It expands the self-ordering regime of PAA membranes, which is of great value for applications in diverse areas of nanotechnology.     

Dry bonding to dentin: Broadening the moisture spectrum and increasing wettability of etch-and-rinse adhesives

ObjectiveTo determine whether the effect of dentin moisture on the etch-and-rinse bonding may be minimized by dry-bonding protocols utilizing aqueous or ethanolic dimethyl sulfoxide (DMSO) pretreatments.MethodsH₃PO₄-etched mid-coronal dentin surfaces from human molars were randomly blot- or air-dried for 30 s and pretreated with DMSO/H₂O or DMSO/EtOH solutions. Untreated samples served as control. Moisture control was performed by either blot- or air-drying. Samples were bonded with a multistep etch-and-rinse adhesive. Restored crown segments (n = 8/group) were stored in distilled water for 24 h and sectioned for microtensile bond strength testing. Resin-dentin beams (0.8 mm²) were tested under tension until fracture (0.5 mm/min) after 24 h and two years of storage in artificial saliva at 37 °C.SEM nanoleakage evaluation was performed on aged samples. Collagen wettability was also measured by sessile drops of the hydrophilic and hydrophobic bonding resins (n = 8/group). Data were examined by factorial ANOVA followed by the Tukey test (α = 0.05).ResultsDry bonding to untreated collagen produced inferior immediate and long-term bond strengths than wet bonding (p < 0.05). Regardless of initial hydration and moisture control, DMSO-dry bonding produced initially higher and stable bond strengths after aging (p < 0.05). DMSO-pretreated groups presented improved collagen wettability with lower silver uptake (p < 0.05).SignificanceDespite the common belief that etch-and-rinse adhesives must be applied onto moist collagen, DMSO-dry bonding protocols not only improved bonding performance and hybrid layer integrity, but also brought more versatility to collagen hybridization by reducing overdrying-related issues.     

To etch or not to etch,Part I: On the fatigue strength and dentin bonding performance of universal adhesives

ObjectiveTo characterize whether the bonding performance and fatigue strength of resin-dentin interfaces created by a universal adhesive would be affected by different H₃PO₄-application times to more accurately assess long-term durability.MethodsMid-coronal flat dentin surfaces with standardized smear-layers were produced on sound third molars, etched with 32% H₃PO₄ for 0, 3 and 15 s, bonded with a mild universal adhesive (3M-ESPE) and restored with a nanofilled composite. Bonded specimens (0.9 × 0.9 mm) were stored in deionized water for 24 h and sectioned into beams for microtensile testing (n = 10). Resin-dentin beams were tested under tension until failure (0.5 mm/min) after 24 h or 6 month storage in artificial saliva at 37 ?C. Bar-shaped resin-dentin beams (0.9 × 0.9 × 12 mm) were tested under 4-point-flexure initially at quasi-static loads (n = 22) and then under cyclic loads (n > 50). The stress-life fatigue behavior was evaluated using the twin-bonded interface approach by the staircase method at 4 Hz. Fractured interfaces and the tension side of unfractured beams were evaluated under SEM, along with the micro-morphology of the etched dentin surfaces and hybrid layers. Data were analyzed by ANOVA and Tukey test and Wilcoxon Rank Sum Test (α = 0.05).ResultsQuasi-static loads were limited to discriminate the bonding performance of resin-dentin interfaces. Application modes significantly affected etching patterns, fatigue strength, endurance limits and hybrid layer morphology (p < 0.001).SignificanceReductions in fatigue strength of self-etched bonded interfaces raise concerns about the true ability of universal adhesives to properly bond to dentin.     

Temporary zinc oxide–eugenol cement: eugenol quantity in dentin and bond strength of resin composite

Uptake of eugenol from eugenol‐containing temporary materials may reduce the adhesion of subsequent resin‐based restorations. This study investigated the effect of duration of exposure to zinc oxide–eugenol (ZOE) cement on the quantity of eugenol retained in dentin and on the microtensile bond strength (μTBS) of the resin composite. The ZOE cement (IRM Caps) was applied onto the dentin of human molars (21 per group) for 1, 7, or 28 d. One half of each molar was used to determine the quantity of eugenol (by spectrofluorimetry) and the other half was used for μTBS testing. The ZOE‐exposed dentin was treated with either OptiBond FL using phosphoric acid (H₃PO₄) or with Gluma Classic using ethylenediaminetetraacetic acid (EDTA) conditioning. One group without conditioning (for eugenol quantity) and two groups not exposed to ZOE (for eugenol quantity and μTBS testing) served as controls. The quantity of eugenol ranged between 0.33 and 2.9 nmol mg^?1 of dentin (median values). No effect of the duration of exposure to ZOE was found. Conditioning with H₃PO₄ or EDTA significantly reduced the quantity of eugenol in dentin. Nevertheless, for OptiBond FL, exposure to ZOE significantly decreased the μTBS, regardless of the duration of exposure. For Gluma Classic, the μTBS decreased after exposure to ZOE for 7 and 28 d. OptiBond FL yielded a significantly higher μTBS than did Gluma Classic. Thus, ZOE should be avoided in cavities later to be restored with resin‐based materials.     

Histopathologic evaluation of the effects of four calcium hydroxide liners on monkey pulps

Pulpal response of four calcium hydroxide liners, MPC 10®, MPC 12®, Dycal® and Pulpdent® were tested on primary and permanent teeth with zinc oxide and eugenol (ZOE) and silicate as controls. Responses of the pulps were evaluated in Rhesus monkeys, utilizing Class V cavity preparations at 3 days, 5 and 8 weeks. An equivalent number of anterior and posterior teeth were studied for all compounds. The Ca(OH)₂ liners, zinc oxide and eugenol (ZOE) and silicate controls were placed in 80 primary and 80 permanent teeth. Following perfusions the teeth were prepared utilizing routine histological procedures. The 3 day response of the calcium hydroxides was moderate with some disruption in the odontoblasts, vacuolization and mild inflammation underlying the cavity except Pulpdent which was more severe. At 5 weeks a decrease in inflammatory response and the formation of reparative dentin was similar for all calcium hydroxides tested at this time period. At 8 weeks more reparative dentin was noted with slight to moderate pulpal responses. At all time periods ZOE produced the least pulpal response while silicate produced the most severe response at 5 and 8 weeks. This study reports the biological responses of four calcium hydroxide compounds used as cavity liners in non-exposures in a series of primary and permanent teeth of monkeys using ZOE and silicate as controls. Responses to the four Ca(OH)₂ compounds were moderate for all the experimental compounds except Pulpdent which was more severe at the early time period tested. ZOE produced a milder and silicate a severe response at all periods. All of these compounds were placed by random selection in anterior and posterior teeth of both arches and five teeth were evaluated in both primary and permanent teeth at 3 days, 5 and 8 weeks.     

Electrochemically driven polystyrene-sulfonic acid particles in deionized suspension: microscope analysis

Polystyrene latex particles, 1.6 μm in diameter, with sulfonic acid groups were driven by the application of voltages for E<−0.4 or >0.6 V in a well-deionized suspension, accompanied by Brownian motion. Their positions were monitored and recorded with a video-microscope at various electrode voltages. The moving rates decreased with the time of the potential application, and were proportional to the Faradaic current. Therefore, the motion is relevant to electrode reactions rather than simply the electrostatic force between the two electrodes. The electrode reactions generate OH⁻ or H₃O⁺. The extra charge on OH⁻ or H₃O⁺ is compensated by the negatively charged latex particles. From the relation between the current and the velocity of the particles, only 2% of the current contributes to the motion of the particles.     

A microleakage study of gutta-percha/AH Plus and Resilon/Real self-etch systems after different irrigation protocols

The development and maintenance of the sealing of the root canal system is the key to the success of root canal treatment. The resin-based adhesive material has the potential to reduce the microleakage of the root canal because of its adhesive properties and penetration into dentinal walls. Moreover, the irrigation protocols may have an influence on the adhesiveness of resin-based sealers to root dentin.

Objective

The objective of the present study was to evaluate the effect of different irrigant protocols on coronal bacterial microleakage of gutta-percha/AH Plus and Resilon/Real Seal Self-etch systems.

Material and Methods

One hundred ninety pre-molars were used. The teeth were divided into 18 experimental groups according to the irrigation protocols and filling materials used. The protocols used were: distilled water; sodium hypochlorite (NaOCl)+eDTA; NaOCl+H₃PO₄; NaOCl+eDTA+chlorhexidine (CHX); NaOCl+H₃PO₄+CHX; CHX+eDTA; CHX+ H₃PO₄; CHX+eDTA+CHX and CHX+H₃PO₄+CHX. Gutta-percha/AH Plus or Resilon/Real Seal Se were used as root-filling materials. The coronal microleakage was evaluated for 90 days against Enterococcus faecalis. Data were statistically analyzed using Kaplan-Meier survival test, Kruskal-Wallis and Mann-Whitney tests.

Results

No significant difference was verified in the groups using chlorhexidine or sodium hypochlorite during the chemo-mechanical preparation followed by eDTA or phosphoric acid for smear layer removal. The same results were found for filling materials. However, the statistical analyses revealed that a final flush with 2% chlorhexidine reduced significantly the coronal microleakage.

Conclusion

A final flush with 2% chlorhexidine after smear layer removal reduces coronal microleakage of teeth filled with gutta-percha/AH Plus or Resilon/Real Seal SE.     

Electrochemistry of a urea-functionalized calix[4]diquinone sulfate-anion selective receptor

A new class of neutral ligands is synthesized and studied for the binding properties with anions by electrochemical methods. The binding of calix[4]diquinone 1 with HSO₄^? causes a large negative shift of the electrode potentials of the calix[4]diquinone. This novel neutral anion receptor 1 binds anions through hydrogen-bonding and shows high selectivity for HSO₄^? over H₂PO₄^?, Cl^?, and CH₃CO₂^?. The selectivity of HSO₄^? over H₂PO₄^?, Cl^?, and CH₃CO₂^? may be attributed to the stronger hydrogen-bonding with the urea moiety, and also with the quinone moiety of 1 receptor, and also the greater compatibility of the cavity of 1 with tetrahedral HSO₄^?.