Synthesis of silver-containing calcium aluminate particles and their effects on a MTA-based endodontic sealer.

OBJECTIVE: To synthetize calcium aluminate (C3A) and silver-containing C3A particles (C3A+Ag) testing their effects on the properties of a MTA-based endodontic sealer in comparison to an epoxy resin- and a calcium silicate-based sealer. METHODS: Pure C3A and C3A+Ag particles were synthesized by a chemical method and characterized using XRD to identify crystalline phases. SEM/EDS analysis investigated morphology, particle size, and elemental composition of particles. Setting time, flow, radiopacity, water sorption and solubility of commercial and modified sealers were evaluated according to ISO 6876/2012. The pH and ions release were measured using a pHmeter and a microwave induced plasma optical emission spectrometer. The inhibition of biofilm growth was evaluated by confocal laser scanning microscopy (CLSM). Data were rank transformed and analyzed by ANOVA and Tukey test (P<0.05). RESULTS: The C3A particles showed an irregular grain agglomerated structure with voids and pores. In C3A+Ag particles, Ag modified the material morphology, confirming the deposition of Ag. The physicochemical properties of the modified MTA-based sealer were similar to the commercial material, except for the significant increase in Ca+2 release. However, there was no Ag release. Setting time, flow, radiopacity, water sorption and solubility were adequate for all materials. All the materials showed alkaline pH. Antibiofilm effect was improved in the presence of C3A particles, while the biofilm inhibition was lower in the presence of Ag. SIGNIFICANCE: The modified sealer presented improved antibiofilm properties and calcium release, without dramatic effects on the other characteristics. It is expected a positive effect in its antimicrobial behavior.

Biocompatibility Investigation of New Endodontic Materials Based on Nanosynthesized Calcium Silicates Combined with Different Radiopacifiers.

INTRODUCTION: The aim of this article was to analyze biocompatibility and bioactivity of new endodontic materials on the basis of nanosynthesized calcium silicates (ALBO-MPCA1 and ALBO-MPCA2) combined with different radiopacifiers in comparison with MTA+. METHODS: Morphology of the samples was studied by scanning electron microscopy, and the pH and ion release analysis were also assessed. Biocompatibility of materials' eluates (24-hour, 7-day, and 21-day) was conducted by using MTT test. Twelve New Zealand white rabbits were used for intraosseous implantation. Four calvarial defects per animal were created and filled with freshly prepared investigated materials. RESULTS: Samples mostly consisted of agglomerates built up from nanoparticles, preferably spherical and rod-like. There was no significant difference among pH values of materials' eluates after 24 hours (P > .05). The amount of calcium and aluminum ion release decreased, whereas the amount of magnesium and bismuth (ALBO-MPCA1, MTA+) and barium (ALBO-MPCA2) increased during 21-day period. The metabolic activity of cells increased after the extraction time, except in case of undiluted elutes of ALBO-MPCA2 and ALBO-MPCA1 (21-day). Histologic analysis of the samples revealed newly formed bone tissue with moderate inflammation for all investigated materials, which subsided during 90-day period to mild. Both MTA+ and ALBO-MPCA1 were in direct contact with the newly formed bone tissue. After 90 days, statistically significant difference in hard tissue formation was observed in comparison of MTA+ and ALBO-MPCA1 with control group (P < .05). CONCLUSIONS: Experimental materials ALBO-MPCA1 and ALBO-MPCA2 possess both biocompatibility and bioactivity. Because ALBO-MPCA1 provokes favorable biological response, it is especially good candidate for further clinical investigations.

Calcium silicate-based sealers: Assessment of physicochemical properties, porosity and hydration.

OBJECTIVES: Investigation of hydration, chemical, physical properties and porosity of experimental calcium silicate-based sealers. METHODS: Experimental calcium silicate-based sealers with calcium tungstate and zirconium oxide radio-opacifiers were prepared by mixing 1g of powder to 0.3 mL of 80% distilled water and 20% propylene glycol. MTA and MTA Fillapex were used as controls. The raw materials and set sealers were characterized using a combination of scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Physical properties were analyzed according to ANSI/ADA. The pH and calcium ion release were assessed after 3, 24, 72 and 168 h. The porosity was assessed using mercury intrusion porosimetry. RESULTS: The analysis of hydration of prototype sealers revealed calcium hydroxide as a by-product resulting in alkaline pH and detection of calcium ion release, with high values in initial periods. The radiopacity was similar to MTA for the sealers containing high amounts of radio-opacifiers (p>0.05). Flowability was higher and film thickness was lower for resinous MTA Fillapex sealer (p<0.05). The test sealers showed water sorption and porosity similar to MTA (p>0.05). SIGNIFICANCE: The prototype sealers presented adequate hydration, elevated pH and calcium ion release. Regarding physical properties, elevated proportions of radio-opacifiers were necessary to accomplish adequate radiopacity, enhance flowability and reduce film thickness. All the tested sealers presented water sorption and porosity similar to MTA.

In vitro evaluation of antibacterial effect of AH Plus incorporated with quaternary ammonium epoxy silicate against Enterococcus faecalis.

INTRODUCTION: The purpose of this study was to evaluate the in vitro antibacterial effect of AH Plus (Dentsply, DeTrey, Konstanz, Germany) incorporated with quaternary ammonium epoxy silicate (QAES) against Enterococcus faecalis. METHODS: QAES particles were synthesized by the cocondensation of tetraethoxysilane with 2 trialkoxysilanes (3-[trimethoxysilyl]propyldimethyloctadecyl ammonium chloride and 3-glycidyloxypropyltrimethoxysilane) through a 1-pot sol-gel route. Dried QAES particles were then characterized by attenuated total reflection Fourier transform infrared spectroscopy and scanning electron microscopy. AH Plus sealers incorporated with 0-8 wt% QAES were tested after 4 weeks of water aging to assess the in vitro antibacterial activity against E. faecalis by the direct contact test (DCT) and 3-dimensional image analysis of live/dead-stained E. faecalis biofilms using confocal laser scanning microscopy. RESULTS: The Fourier transform infrared spectroscopy spectrum of QAES particles revealed the coexistence of the characteristic absorbance band of the siloxane backbone (Si-O-Si) from 1,000-1,100 cm(-1), epoxide band peaking at ∼916 cm(-1), and C-N stretching vibration peaking at 1,373 cm(-1). The scanning electron microscopic image showed the spherical morphology of QAES particles with ∼120 nm in diameter and a rough surface. DCT results revealed that AH Plus alone (0 wt% QAES) after 4 weeks of water aging had no inhibitory effect on E. faecalis growth (P = .569). AH Plus incorporated with QAES (2-8 wt%) showed antibacterial activity against E. faecalis as shown in DCT and biofilm viability results (P < .001). CONCLUSIONS: The incorporation of QAES into epoxy resin-based AH Plus may be a promising approach for controlling endodontic infection at the time of canal filling and preventing subsequent reinfection.

Synthesis and characterization of a glycerol salicylate resin for bioactive root canal sealers.

AIM: To develop and characterize a salicylate resin with potential use in bioactive endodontic sealers. METHODOLOGY: Methyl salicylate, glycerol and titanium isopropoxide were added in a closed system for the transesterification reaction. The resin obtained was characterized by proton nuclear magnetic resonance spectroscopy (1H NMR) and size exclusion chromatography (SEC). To verify the applicability of the resin to the development of endodontic sealers, experimental cements were prepared by mixing glycerol salicylate resin, calcium hydroxide and methyl salicylate in the ratios of 2 : 1 : 1, 1 : 2 : 1, 1 : 1 : 2, 1 : 1 : 1, 4 : 1 : 1, 1 : 4 : 1 and 1 : 1 : 4. Setting times were measured according to ISO 6876. Features of the hardening reaction were described by micro-RAMAN spectroscopy. RESULTS: The transesterification reaction had a 72% efficiency. The (1) H NMR analysis revealed the presence of the expected functional groups (hydroxyls and aromatic rings), and the SEC confirmed the molar mass of the resin produced. The setting times of experimental sealers ranged from 70 min (ratio 1 : 1 : 1) to 490 min (ratio 1 : 1 : 4). The conversion of the salicylic groups (1 613 cm(-1) ) to salicylate salt (1 543 cm(-1) ) and the reduction in calcium hydroxide peaks (1084 and 682 cm(-1) ) were confirmed by micro-RAMAN spectroscopy, which showed the calcium chelation by the resin. CONCLUSION: The new glycerol salicylate resin was successfully synthesized and revealed a potential application in the development of endodontic sealers.

Synthesis and characterizations of a fluoride-releasing dental restorative material.

The aim was to develop an obturating material which has the tendency to release fluoride and minimize interfaces with tooth. Nano-fluorapatite (nFA) powder was synthesized by sol-gel. The composite based on polyurethane (PU) was obtained by chemically binding the nFA (10, 15, 20%wt/wt) to the diisocyanate component by utilizing in-situ polymerization. The procedure involved stepwise addition of monomeric units of PU, and optimizing the reagent concentrations to synthesize composite. The structural, phase and morphological analysis of nFA was evaluated. The structural, fluoride release and in-vitro adhesion analysis with tooth structure of PU/nFA was conducted. For fluoride release analysis the samples were stored in artificial saliva and deionized water for periodical time intervals. Bond strength of composites was analyzed by push-out test. Chemical linkage was achieved between PU and nFA without intermediate coupling agent. The insignificant difference of fluoride release pattern was observed in artificial saliva and (p≥0.05) deionized water. The PU/nFA composite provided sustained release of fluoride over a long period of time. The composite showed more adhesion toward tooth structure with the increase in concentration of nFA. Bond strength of composite was in accordance with root canal filling material, hence, the material with anti-cariogenic properties can be used as an obturating material.

New nanostructural biomaterials based on active silicate systems and hydroxyapatite: characterization and genotoxicity in human peripheral blood lymphocytes.

AIM: To characterize and investigate the genotoxic effect of a new endodontic cement based on dicalcium- and tricalcium-silicate (CS) with hydroxyapatite (HA) on human lymphocytes. METHODOLOGY: Hydrothermal treatment was applied for synthesis of CS and HA. The final mixture HA-CS, with potential to be used in endodontic practice, is composed of CS (34%) and HA (66%). Human lymphocytes were incubated with HA, HA-CS and CS for 1 h, at 37 °C and 5% CO2. Cell viability was determined using the trypan blue exclusion assay. To evaluate the level of DNA damage comet assay (single cell gel electrophoresis) was performed. For the statistical analysis anova and Duncan's Post Hoc Test were used. RESULTS: The SEM analysis indicated that CS consisted mostly of agglomerates of several micrometers in size, built up from smaller particles, with dimensions between 117 and 477 nm. This is promising because dimensions of agglomerates are not comparable with channels inside the cell membranes, whereas their nano-elements provide evident activity, important for faster setting of these mixtures compared to MTA. Values of DNA damage obtained in the comet assay indicated low genotoxic risk of the new endodontic materials. CONCLUSIONS: The significantly improved setting characteristics and low genotoxic risk of the new material support further research.

The effect of various mixing and placement techniques on the compressive strength of mineral trioxide aggregate.

INTRODUCTION: The aim of this study was to evaluate the effect of various mixing techniques including mechanical and manual mixing as well as the effect of ultrasonic agitation during placement on the compressive strength of mineral trioxide aggregate (MTA). METHODS: Tooth-colored ProRoot MTA (Dentsply Maillefer, Ballaigues, Switzerland) and white MTA Angelus (Angelus Soluções Odontologicas, Londrina, Brazil) were used. One gram of each powder was mixed with a 0.34-g aliquot of distilled water. Specimens were mixed either by mechanical mixing of capsules for 30 seconds at 4,500 rpm or by a saturation technique and the application of a condensation pressure of 3.22 MPa for 1 minute. Half of the specimens were placed in stainless steel molds and agitated using indirect ultrasonic activation. All specimens were subjected to compressive strength testing after 4 days. RESULTS: The compressive strength values of ProRoot MTA were significantly greater than those of MTA Angelus (P < .05). The highest compressive strength values were recorded from ProRoot MTA samples that were mixed mechanically and placed using ultrasonic activation (mean = 101.71 MPa), whereas the lowest values were recorded for MTA Angelus samples that were mixed manually and placed without ultrasonic activation (mean = 53.47 MPa). Ultrasonically agitated groups had higher compressive strength values (P < .001). The specimens mixed mechanically had higher compressive strength values than those mixed manually (P < .05). CONCLUSIONS: The compressive strength values of ProRoot MTA were significantly greater than those of MTA Angelus. Mechanical mixing enhanced the compressive strength of the material. Regardless of the mixing techniques applied, ultrasonic agitation improved the compressive strength of the material.

Mineral trioxide aggregate-based endodontic sealer stimulates hydroxyapatite nucleation in human osteoblast-like cell culture.

INTRODUCTION: The main purpose of this study was to evaluate the biocompatibility and bioactivity of a new mineral trioxide aggregate (MTA)-based endodontic sealer, MTA Fillapex (MTA-F; Angelus, Londrina, Brazil), in human cell culture. METHODS: Human osteoblast-like cells (Saos-2) were exposed for 1, 2, 3, and 7 days to MTA-F, Epiphany SE (EP-SE; SybronEndo, Orange, CA), and zinc oxide-eugenol sealer (ZOE). Unexposed cultures were the control group (CT). The viability of the cells was assessed by MTT assay and the morphology by scanning electron microscopy (SEM). The bioactivity of MTA-F was evaluated by alkaline phosphatase activity (ALP) and the detection of calcium deposits in the culture with alizarin red stain (ARS). Energy-dispersive X-ray spectroscopy (EDS) was used to chemically characterize the hydroxyapatite crystallites (HAP). Saos-2 cells were cultured for 21 days for ARS and SEM/EDS. ARS results were expressed as the number of stained nodules per area. Statistical analysis was performed with analysis of variance and Bonferroni tests (P < .01). RESULTS: MTA-F exposure for 1, 2, and 3 days resulted in increased cytotoxicity. In contrast, viability increased after 7 days of exposure to MTA-F. Exposure to EP-SE and ZOE was cytotoxic at all time points. At day 7, ALP activity increase was significant in the MTA-F group. MTA-F presented the highest percentage of ARS-stained nodules (MTA-F > CT > EP-SE > ZOE). SEM/EDS analysis showed hydroxyapatite crystals only in the MTA-F and CT groups. In the MTA-F group, crystallite morphology and chemical composition were different from CT. CONCLUSIONS: After setting, the cytotoxicity of MTA-F decreases and the sealer presents suitable bioactivity to stimulate HAP crystal nucleation.

Effect of sodium fluorosilicate on the properties of Portland cement.

INTRODUCTION: Mineral trioxide aggregate (MTA) satisfies most of the ideal properties of a surgical root-end filling and perforation repair material. It has been found to be nontoxic, noncarcinogenic, nongenotoxic, biocompatible, insoluble in tissue fluids, and dimensionally stable and promotes cementogenesis. The major disadvantages are its long setting time and difficult handling characteristics during placement when performing endodontic procedures. MTA is similar to Portland cement (PC) in both composition and properties. The cement industry has used many additives to decrease the setting time of PC. Proprietary formulas of PC additives include fluorosilicates, which decrease setting time. The purpose of this pilot study was to determine whether sodium fluorosilicate (SF) could be used to decrease the setting time without adversely affecting the compressive strength of PC. METHODS: To determine the most appropriate amount of SF to add to PC to decrease its setting time, 1%, 2%, 3%, 4%, 5%, 10%, and 15% SF by weight were added to PC and compared with PC without SF. Setting times were measured by using a Gilmore needle, and compressive strengths were determined by using a materials testing system at 24 hours and 21 days. RESULTS: Statistical analysis was performed by using one-way analysis of variance with post hoc Games-Howell test. None of the percentages of SF were effective in changing the setting time of PC (P > .05), and the SF additives were found to decrease the compressive strength of PC (P < .001). CONCLUSIONS: On the basis of the conditions of this study, SF should not be used to decrease setting time and increase the compressive strength of PC and as such does not warrant further testing with MTA.

The development of iron-free partially stabilized cement for use as dental root-end filling material.

AIM: To determine the effect of increasing the proportion of zinc on partially stabilized cement (PSC) produced using a one-step sol gel process. METHODOLOGY: A one-step sol-gel process of Portland cement-based PSC with Zn was synthesized by replacing iron nitrate. The crystalline phases of the PSC-Zn powder were analysed by using X-ray diffraction (XRD). The experimental groups [i.e., MTA, PSC-Fe (control), PSC with 1% Zn, PSC with 3% Zn, and PSC with 5% Zn] were immersed in simulated body fluid for 3 h, 1 and 3 days to evaluate the hydration product formation. The microstructure and surface morphology were analysed using scanning electron microscopy (SEM). Initial and final setting times of the materials were determined using an ASTM Vicat needle testing machine. To evaluate the cytotoxicity of PSC-Zn system, primary osteoblasts cell lines were used. RESULTS: The addition of increased weight percentages of Zn, resulted in a more unstable phase which favoured the formation of a monoclinic structure of C3 S with an increased hydration reaction of PSC and reduced setting time. The cytotoxicity testing of PSC with Zn revealed that the material was not toxic. CONCLUSIONS: The newly synthesized PSC-Zn material had short setting time and was biocompatible.

Deproteinization technique stabilizes the adhesion of the fiberglass post relined with resin composite to root canal.

To evaluate the effects of pretreatment of root dentin by 5.25% sodium hypochlorite (NaOCl) alone, associated with 2% chlorhexidine in gel base (CHX) and/or ethanol (EtOH), and the air-drying technique (Air) on the bond strength and adhesive durability of fiberglass post relined with resin composite to root dentin. A total of 100 bovine incisor roots were divided into 10 groups: G1 (control), irrigation with physiologic solution; G2, Air; G3, NaOCl; G4, NaOCl + Air; G5, NaOCl + EtOH; G6, NaOCl + EtOH + Air; G7, NaOCl + CHX; G8, NaOCl + CHX + Air; G9, NaOCl + CHX + EtOH; G10, NaOCl + CHX + EtOH + Air. Fiberglass post relined with resin composite was cemented and each group was randomly divided into two subgroups: 24 h of water storage and 12 months of water storage. The push-out test was performed and bond strength values were analyzed by ANOVA and Tukey's test. The use of NaOCl alone or associated with CHX had the highest values of bond strength with or without Air in the immediate and stored groups, being statistically similar to the immediate control group (p > 0.05). The groups using EtOH or Air alone had lower bond strength in the immediate and stored groups (p < 0.05). A significant decrease with the time of the bond strength in the control group was observed after 12 months of storage (p > 0.05). The use of NaOCl or NaOCl associated with CHX preserved the bond strength immediate and for 12 months. The air-drying technique and the other associations decreased the immediate bond strength values.

Development of the foremost light-curable calcium-silicate MTA cement as root-end in oral surgery. Chemical-physical properties, bioactivity and biological behavior.

AIM: An innovative light-curable calcium-silicate cement containing a HEMA-TEGDMA-based resin (lc-MTA) was designed to obtain a bioactive fast setting root-end filling and root repair material. METHODS: lc-MTA was tested for setting time, solubility, water absorption, calcium release, alkalinizing activity (pH of soaking water), bioactivity (apatite-forming ability) and cell growth-proliferation. The apatite-forming ability was investigated by micro-Raman, ATR-FTIR and ESEM/EDX after immersion at 37°C for 1-28 days in DPBS or DMEM+FBS. The marginal adaptation of cement in root-end cavities of extracted teeth was assessed by ESEM/EDX, and the viability of Saos-2 cell on cements was evaluated. RESULTS: lc-MTA demonstrated a rapid setting time (2min), low solubility, high calcium release (150-200ppm) and alkalinizing power (pH 10-12). lc-MTA proved the formation of bone-like apatite spherulites just after 1 day. Apatite precipitates completely filled the interface porosities and created a perfect marginal adaptation. lc-MTA allowed Saos-2 cell viability and growth and no compromising toxicity was exerted. SIGNIFICANCE: HEMA-TEGDMA creates a polymeric network able to stabilize the outer surface of the cement and a hydrophilic matrix permeable enough to allow water absorption. SiO(-)/Si-OH groups from the mineral particles induce heterogeneous nucleation of apatite by sorption of calcium and phosphate ions. Oxygen-containing groups from poly-HEMA-TEGDMA provide additional apatite nucleating sites through the formation of calcium chelates. The strong novelty was that the combination of a hydraulic calcium-silicate powder and a poly-HEMA-TEGDMA hydrophilic resin creates the conditions (calcium release and functional groups able to chelate Ca ions) for a bioactive fast setting light-curable material for clinical applications in dental and maxillofacial surgery. The first and unique/exclusive light-curable calcium-silicate MTA cement for endodontics and root-end application was created, with a potential strong impact on surgical procedures.

Chemical constitution, physical properties, and biocompatibility of experimentally manufactured Portland cement.

INTRODUCTION: An experimental Portland cement was manufactured with pure raw materials under controlled laboratory conditions. The aim of this study was to compare the chemical constitution, physical properties, and biocompatibility of experimentally manufactured Portland cement with those of mineral trioxide aggregate (MTA) and Portland cement. METHODS: The composition of the cements was determined by scanning electron microscopy (SEM) and energy-dispersive x-ray analysis (EDAX). The setting time and compressive strength were tested. The biocompatibility was evaluated by using SEM and XTT assay. RESULTS: SEM and EDAX revealed the experimental Portland cement to have a similar composition to Portland cement. The setting time of the experimental Portland cement was significantly shorter than that of MTA and Portland cement. The compressive strength of the experimental Portland cement was lower than that of MTA and Portland cement. The experimental Portland cement showed a similar biocompatibility to MTA. CONCLUSIONS: The experimental Portland cement might be considered as a possible substitute for MTA in clinical usage after further testing.

Effect of tricalcium aluminate on the properties of tricalcium silicate-tricalcium aluminate mixtures: setting time, mechanical strength and biocompatibility.

AIM: To prepare biphasic mixtures by adding Ca(3) Al(2) O(6) into Ca(3) SiO(5) and to evaluate the effect of Ca(3) Al(2) O(6) on physical and ex vivo biological properties of the Ca(3) SiO(5) /Ca(3) Al(2) O(6) mixtures derived from mineral trioxide aggregate (MTA). METHODOLOGY: Combinations of Ca(3) SiO(5) and Ca(3) Al(2) O(6) (0, 5%, 10% and 15%) powders were mixed with deionized water. After hydration, setting time, compressive strength, ex vivo bioactivity and biocompatibility of each mixture were investigated and compared to pure Ca(3) SiO(5) . RESULTS: With the addition of Ca(3) Al(2) O(6) from 0% to 15%, the initial setting time and final setting time of the Ca(3) SiO(5) /Ca(3) Al(2) O(6) mixtures decreased from 110 to 43min and from 220 to 97min, respectively (P≤0.05). However, the compressive strength increased from 6.75 to 16.20MPa after one day (P≤0.05) and from 17.73 to 29.13 Mpa after 28 days. Furthermore, the mixtures with 10% Ca(3) Al(2) O(6) or less had similar bioactivity and biocompatibility when compared to the pure Ca(3) SiO(5). CONCLUSIONS: The addition of Ca(3) Al(2) O(6) into Ca(3) SiO(5) accelerated the hydration process, reduced the setting time and improved the compressive strength. Furthermore, these mixtures were bioactive and biocompatible and had a stimulatory effect on the L929 cell growth when the content of Ca(3) Al(2) O(6) was below 10%. Therefore, the mixtures with 10% Ca(3) Al(2) O(6) produced the best compromise between hydration and ex vivo biological properties.

Amoxicillin-Loaded Sponges Made of Collagen and Poly[(methyl vinyl ether)-co-(maleic anhydride)] for Root Canal Treatment: Preparation, Characterization and In Vitro Cell Compatibility.

The difficulty of eliminating Enterococcus faecalis and other bacteria infecting dental root canals makes it desirable to develop formulations capable of sustained release of antibiotics within the canal. With this function in view, in this work we compared the mechanical, drug release and biocompatibility properties of amoxicillin-loaded collagen (CL) and CL complexed with poly[(methyl vinyl ether)-co-(maleic anhydride)] (PVMMA), with or without glutaraldehyde (GTA) or the natural product genipin (GN) as cross-linker. Collagen was not denatured by complexation with PVMMA. Only CL-PVMMA-GN sponges did not disintegrate during 7 days exposure to cell culture medium (un-cross-linked CL disintegrated within 24 h and un-cross-linked CL-PVMMA within 4 days), and CL-PVMMA-GN sponges also exhibited the most appropriate combination of mechanical properties (hardness, modulus of deformability and plasticity). CL-PVMMA-GN sponges absorbed aqueous medium faster than other cross-linked formulations, but their maximum uptake was less; and drug release from CL-PVMMA-GN sponges tended to be faster than from any other, except un-cross-linked CL-PVMMA, maximum release taking about 4 days. No formulation significantly altered the viability of L929 fibroblast-like mouse connective tissue cells, but cells growing on sponges showed signs of non-adherence. It is concluded that genipin-cross-linked CL-PVMMA sponges merit further investigation as antibiotics vehicles and aids to tissue regeneration in the dental root canal.

Evaluation of new tri-methacrylates as a reactive diluent in root canal sealant.

In this work, a novel tri-methacrylate oligomer, GPTEMA, with three long-branched chain structures was synthesized through the reaction of glycerol propoxylate triglycidyl ether (GPTE) and methacrylic acid. The structure of GPTEMA was confirmed by FT-IR, (1)H-NMR, gel-permeation chromatography (GPC) and element analysis. The GPTEMA was used to partially or completely replace TEGDMA as reactive diluent and applied in a root canal sealant system containing Bis-GMA. The effects of GPTEMA on the polymerization behavior of Bis-GMA/TEGDMA/GPTEMA co-polymer and properties of its polymerizing product were investigated. Polymerization shrinkage, double bond conversion, glass transition temperature, flexural strength, flexural modulus, water sorption and diffusion coefficient of the Bis-GMA/TEGDMA/GPTEMA co-polymer were measured. The results illustrated that the Bis-GMA/TEGDMA/GPTEMA co-polymer attained lower polymerization shrinkage and higher double bond conversion. However, its T g, flexural strength and flexural modulus decreased with increasing content of GPTEMA, water sorption and diffusion coefficient increased with increasing content of GPTEMA.

Composites made of flame-sprayed bioactive glass 45S5 and polymers: bioactivity and immediate sealing properties.

AIM: To engineer systems using polyisoprene (PI) or polycaprolactone (PCL) and nanometric bioactive glass 45S5 (BG) that could create a hydroxyapatite interface and thus ultimately make the use of an endodontic sealer unnecessary. METHODOLOGY: Different composites using PI or PCL as matrix material were prepared with BG contents of up to 30 wt%. Unfilled PI and PCL, commercially available filled PI (Obtura gutta-percha) and PCL pellets (Resilon) served as control materials. Bioactivity (in vitro precipitate formation in simulated body fluid) was investigated using scanning electron microscopy and X-ray diffraction analysis. To test immediate sealing ability, simulated root canals were filled with heated materials, and dye leakage was assessed. Leakage was statistically compared between groups using Kruskal-Wallis analysis of variance followed by Mann-Whitney U tests and Bonferroni correction. The alpha-type error was set at 0.05. RESULTS: Both composite systems revealed hydroxyapatite formation on their surface. This was not observed on control materials. Incorporating 30 wt% BG into PI and PCL significantly (P < 0.05) improved their immediate sealing ability compared to that of unfilled polymers, so that dye leakage in simulated root canals was prevented completely. CONCLUSION: Polyisoprene and PCL composites with BG showed promising results as single root canal filling materials. Incorporation of BG fillers into the polymers under investigation made the resulting composite materials bioactive and improved their immediate sealing ability.

Synthesis, characterization and photopolymerization of a new dimethacrylate monomer based on (alpha-methyl-benzylidene)bisphenol used as root canal sealer.

Methacrylate resin-based sealers have attracted wide attention because of their easy handling, superior aesthetic qualities, good mechanical properties and excellent adhesive ability with dentin. 2,2-Bis[4-(2'-hydroxy-3'-methacryloyloxypropoxy)-phenyl]-propane (Bis-GMA) is the main component of the newly developed commercial root canal sealer 'Epiphany', which is one of the methacrylate resin-based sealers. In order to further reduce the polymerization volume shrinkage of Bis-GMA, 4,4'-(alpha-methylbenzylidene)-bis(2'-hydroxy-3'-methacryloyloxy-propoxy)benzene (4,4'-AMBHMB) with higher molecular weight and larger molecular volume was synthesized to replace Bis-GMA as one of the components of the root canal sealer used in this study. The structure of monomer 4,4'-AMBHMB was confirmed by FT-IR, (1)H-NMR, mass spectrum and elemental analysis. The photopolymerization behavior of mixture of 4,4'-AMBHMB and triethylene glycol dimethacrylate (TEGDMA) was investigated by FT-IR. Degree of double bond conversion, volume shrinkage, water sorption and solubility, diffusion coefficient value, flexure strength and glass transition temperature of 4,4'-AMBHMB/TEGDMA system with a mass ratio of 50:50 were measured. A 50:50 Bis-GMA/TEGDMA formulation was used as reference. The results illustrated that 4,4'-AMBHMB/TEGDMA system had the same double bond conversion and water sorption with Bis-GMA/TEGDMA system. Polymerization shrinkage, water solubility and diffusion coefficient of 4,4'-AMBHMB/TEGDMA system were lower than that of the Bis-GMA/TEGDMA system, whereas the flexural strength and glass-transition temperature of 4,4'-AMBHMB/TEGDMA system were higher than that of the Bis-GMA/TEGDMA system.

The effect of various mixing techniques on the surface microhardness of mineral trioxide aggregate.

AIM: To evaluate the influence of various mixing procedures including ultrasonic vibration, trituration of customized encapsulated mineral trioxide aggregate (MTA) and condensation on the Vickers surface microhardness of MTA. METHODOLOGY: ProRoot MTA Original, ProRoot MTA (white), MTA-Angelus (grey) and MTA White Angelus (white) were prepared using several mixing techniques including ultrasonic vibration, trituration of customized encapsulated MTA and conventional condensation. Twelve experimental groups (four materials: three techniques) were evaluated, each with 35 samples. All samples were incubated after preparation and subjected to Vickers surface microhardness testing after 4 and 28 days. Data was were subjected to a two-way anova. RESULT: At 28 days, the surface microhardness value was significantly greater for all experimental groups compared to 4 days after mixing (P < 0.00001). The application of ultrasonic energy to MTA produced significantly higher surface microhardness values compared to the other mixing techniques at both 4 and 28 days (P < 0.0001). However, no significant difference existed between condensation and trituration techniques at both time intervals. Regardless of the mixing technique employed, a significant difference (P < 0.0001) was observed in surface microhardness value between all types of MTA apart from between Angelus grey and ProRoot white at both 4 and 28 days, both of which produced the highest values. CONCLUSION: Compared to trituration and condensation techniques, the application of ultrasonic energy to MTA produced a significantly higher surface microhardness value at both 4 and 28 days. Irrespective of mixing technique, ProRoot white and Angelus grey had the highest surface microhardness values. Trituration of encapsulated, premeasured MTA and water provides a standardiszed method of mixing that produces MTA slurries with more controllable handling characteristics.