Does a final rinse to remove smear layer interfere on dentin permeability of root canals?

Objective. The objective of this study was to assess the influence of different final irrigating solutions on dentin permeability and smear layer removal using the same specimens and relate the results obtained. Study design. Forty anterior human teeth were instrumented and divided into 4 groups (n = 10) at the final rinse step, according to the irrigant used: G I (control) - 1% NaOCl; G II - 17% EDTA; G III - 17% EDTAT; and G IV - Biopure MTAD. The canals were filled with 0.5% methylene blue and maintained in bottles for 48 hours. The roots were transversally split in coronal, middle, and apical fragments. The specimens were photographed and analyzed regarding dye penetration. The fragments were then axially split and prepared for SEM. The photomicrographs were analyzed and qualified by scores. Results. Only the EDTA-T group exhibited statistical difference in which the apical third had less dentin permeability (P < .05). When a decalcifying agent was used, smear layer was removed, which did not happen in the NaOCl group. Regarding smear layer removal, differences were found only in the EDTA group in which the apical third presented more smear layer (P < .05). No correlation was found for both studies (r = 0.4207). Conclusions. There was not an even relationship between the results from both studies, which inferes that higher or lower dentinal permeability does not necessarily correspond to a higher or lower amount of smear layer. The analysis of dentin permeability and smear layer removal was shown to be a feasible procedure using the same specimens. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009; 107: e47-e51)

Effect of low-intensity laser therapy on mast cell degranulation in human oral mucosa

Little is known about the physiological mechanisms related to low-intensity laser therapy (LILT), particularly in acute inflammation and subsequent wound healing. The objective of this study was to verify the effect of LILT on mast cell degranulation. Epulis fissuratum tissues from eight patients were used. One part of the lesion was irradiated with an AsGaAl laser (lambda = 670 nm, 8.0 J/cm(2), 5 mW, 4 min). The other part was not irradiated. Then, the specimens were immediately removed, fixed and examined by light microscopy. The number of mast cells was similar in laser-treated samples when compared with non-irradiated specimens. The degranulation indexes of the mast cells observed in the irradiated samples were significantly higher than those of controls (P < 0.05). LILT with the parameters used increased the number of degranulated mast cells in oral mucosa.

MMP1 and MMP20 contribute to tooth agenesis in humans

Objective: Variations in genes that are critical for tooth formation may contribute to the tooth agenesis. MMPs are potential candidate genes for dental alterations based on the roles they play during embryogenesis. The aim of this study was to investigate the possible association between MMP1, MMP3, and MMP20 and tooth agenesis. Methods: One hundred sixty-seven nuclear families from two different populations were analysed, 116 from Brazil and 51 from Turkey. Probands had at least one congenitally missing tooth. DNA samples were obtained from blood or saliva samples and genotyping was performed using TagMan chemistry. In addition, Mmp20 was selected for quantitative real-time polymerase chain reaction analysis with SYBR Green I Dye in mouse tooth development. Results: Associations between tooth agenesis and MMP1 (p = 0.007), and MMP20 (p = 0.03) were found in Brazilian families. In the total dataset, MMP20 continued to be associated with tooth agenesis (p = 0.01). Mmp20 was not expressed during the initial stages of tooth development. Conclusion: Our findings provide evidence that MMP1 and MMP20 play a role in human tooth agenesis. (C) 2010 Elsevier Ltd. All rights reserved.

Comparison of dentin root canal permeability and morphology after irradiation with Nd:YAG, Er:YAG, and diode lasers

The aim of this study was to compare the effects of Nd:YAG, Er:YAG, and diode lasers on the morphology and permeability of root canal walls. The three laser wavelengths mentioned interact differently with dentin and therefore it is possible that the permeability changes caused will determine different indications during endodontic treatment. Twenty-eight human single-rooted teeth were instrumented up to ISO 40 and divided into four groups: group C, control (GC), non-laser irradiated; group N (GN), irradiated with Nd:YAG laser; group E (GE), with Er:YAG laser and group D (GD) with diode laser. After that, the roots were filled with a 2% methylene blue dye, divided into two halves and then photographed. The images were analyzed using Image J software and the percentage of dye penetration in the cervical, middle, and apical root thirds were calculated. Additional scanning electron microscopy (SEM) analyses were also performed. The analysis of variance (ANOVA) showed significant permeability differences between all groups in the middle and cervical thirds (p < 0.05). The Tukey test showed that in the cervical third, GN presented means of dye penetration statistically significantly lower than all of the other groups. In the middle third, GE and GD showed statistically higher dye penetration means than GC and GN. SEM analysis showed melted surfaces for GN, clean wall surfaces with open dentinal tubules for GE, and mostly obliterated dentinal tubules for GD. Er:YAG (2,094 nm) laser and diode laser (808 nm) root canal irradiation increase dentinal permeability and Nd:YAG (1,064 nm) laser decreases dentin permeability, within the studied parameters.

Influence of the bonding substrate in dental composite polymerization stress testing

Our objective was to compare the polymerization stress (sigma(pol)) of a series of composites obtained using poly(methyl methacrylate) (PMMA) or glass as bonding substrates, and to compare the results with those from in vitro microleakage of composite restorations. The tested hypothesis was that stress values obtained in a less rigid testing system (i.e. using PMMA) would show a better relationship with microleakage data. Five dental composites were tested: Filtek Z250 (FZ), Z100 (Z1), Concept (CO), Durafill (DU) and Heliomolar (HM). sigma(pol) was determined in 1 mm high specimens inserted between two rods (empty set = 5 mm) of either PMMA or glass. The composite elastic modulus (E) was obtained by three-point bending. sigma(pol) and E data were submitted to a one-way analysis of variance/Tukey test (alpha = 0.05). For the microleakage test (MI), bovine incisors received cylindrical cavities (empty set = 5 mm, h = 2 mm), which were restored in bulk. After storage for 24 h in water, specimens were subjected to dye penetration using AgNO(3) as tracer. Specimens were sectioned twice, perpendicularly, and microleakage was measured (in millimeters) under 20x magnification. Data from MI were submitted to the Kruskal-Wallis test. Means (SD) of sigma(pol) (MPa) using glass/PMMA were FZ: 7.5(1.8)(A)/2.5(0.2)(bc); Z1: 7.3(0.5)(A)/2.8(0.3)(ab); CO: 6.8(1.1)(A)/3.2(0.5)(a); DU: 4.5(0.7)(B)/2.0(0.2)(bc); HM: 3.5(0.2)(B)/2.3(0.3)(c). sigma(pol) obtained using PMMA rods were 34-67% lower than with glass. Means (SD) for tooth average/tooth maximum microleakage were FZ: 0.92(0.19)(B)/1.53(0.30)(a); Z1: 1.19(0.21)(A)/1.75(0.20)(a); CO: 1.26(0.25)(A)/1.78(0.24)(a); DU: 0.83(0.30)(B)/1.68(0.46)(a): HM: 0.81(0.27)(B)/1.64(0.54)(a). The tested hypothesis was confirmed, as the composites showed the same ordering both in the polymerization stress test using PMMA rods and in the microleakage test. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Physical Properties and Interfacial Adaptation of Three Epoxy Resin-based Sealers

Introduction: The aim of the study was to evaluate the radiopacity, solubility, flow, film thickness, setting time, and adaptation to the root canal walls of 3 epoxy resin based sealers: AH Plus, Acroseal, and Adseal. Methods: Physical tests were performed following American National Standards Institute/American Dental Association`s requirements. For interfacial adaptation analysis, 30 maxillary canines were shaped by using Pro Taper instruments. The specimens were divided into 3 groups (n = 10): group 1, AH Plus; group 2, Acroseal; and group 3, Adseal. The sealers were mixed with rhodamine B dye, and the canals were filled by using the lateral compaction technique. The percentage of gaps and voids area was calculated at 2, 4, and 6 mm levels from the apex. Statistical evaluation was performed by using analysis of variance for physical analysis and nonparametric Kruskal-Wallis and Dunn tests for interfacial adaptation (P<.05). Results: No statistical differences were found for adaptation, percentage of voids, solubility, flow, and film thickness among the sealers (P>.05). AH Plus was significantly more radiopaque (P<.05). For the setting time, there were statistical differences among all the studied sealers (P<.05). Conclusions: AH Plus, Acroseal, and Adseal presented similar root canal adaptation, solubility, flow, and film thickness. Statistical differences were found for radiopacity and setting time (P<.05). (J Endod 2011;37:1417-1421)

Analysis of four gutta-percha techniques used to fill mesial root canals of mandibular molars

P>Aim To compare the percentage of gutta-percha, sealer and voids and the influence of isthmuses in mesial root canals of mandibular molars filled with different techniques. Methodology Canals in 60 mesial roots of mandibular first molars were prepared with ProTaper instruments to size F2 (size 25, 0.08 taper) and filled using a single-cone, lateral compaction, System B or Thermafil techniques. An epoxy resin sealer was labelled with Rhodamine-B dye to allow analysis under a confocal microscope. The percentage of gutta-percha, sealer and area of voids was calculated at 2, 4 and 6 mm from the apex, using Image Tool 3.0 software. Statistical analysis was performed using nonparametric Kruskal-Wallis and Dunn tests (P < 0.05). The influence of isthmuses on the presence or absence of voids was evaluated using the Fisher test. Results At the 2 mm level, the percentage of gutta-percha, sealer and voids was similar amongst the System B, lateral compaction and single-cone techniques. The single-cone technique revealed significantly less gutta-percha, more sealer and voids in comparison with the Thermafil technique at the 2 and 4 mm level (P < 0.05). The analysis of all sections (2, 4 and 6 mm) revealed that more gutta-percha and less sealer and voids were found in root canals filled with Thermafil and System B techniques (P < 0.05). The Fisher test revealed that the presence of isthmuses increased the occurence of voids in the lateral compaction group only (P < 0.05). Conclusion Gutta-percha, sealer filled area and voids were dependent on the canal-filling technique. The presence of isthmuses may influence the quality of root filling.

Biofilm Dissolution and Cleaning Ability of Different Irrigant Solutions on Intraorally Infected Dentin

Introduction: The aim of this study was to evaluate the biofilm dissolution and cleaning ability of different irrigant solutions on intraorally infected dentin. Methods: One hundred twenty bovine dentin specimens were infected intraorally by using a removable orthodontic device. Thirty samples were used for each irrigant solution: 2% chlorhexidine and 1%, 2.5%, and 5.25% sodium hypochlorite (NaOCl). The solutions were used for 5, 15, and 30 minutes and at 2 experimental volumes, 500 mu L and 1 mL. The samples were stained by using acridine orange dye before and after the experiments and evaluated by using a confocal microscope. The percentage of biofilm, isolated cells, and noncolonized dentin was measured by using a grid system. Differences in the reduction or increase of the studied parameters were assessed by using nonparametric methods (P < .05). Results: The higher values of biofilm dissolution and noncolonized dentin were found in the 30-minute NaOCl group and in the 5-minute and 15-minute groups of 5.25% NaOCL. The use of 2% chlorhexidine solution did not improve the biofilm dissolution or increase the cleaning of the dentin in comparison with the NaOCl solutions (P < .05). Conclusions: Two percent chlorhexidine does not dissolve the biofilms. Thirty minutes of NaOCl are necessary to have higher values of biofilm dissolution and to increase the cleaning of the dentin independently of the concentration in comparison with the 5-minute and 15-minute contact times. (J Endod 2011;37:1134-1138)

Influence of occlusal access on demineralized dentin removal in the Atraumatic Restorative Treatment (ART) approach

Purpose: To verify the influence of cavity access diameter on demineralized dentin removal in the ART approach. Methods: 40 non-carious human premolars were randomly divided into four groups. The occlusal surface was ground flat and the teeth were sectioned mesio-distally. The hemi-sections were reassembled and occlusal access preparations were carried out using ball-shaped diamonds. The resulting size of the occlusal opening was 1.0 mm, 1.4 mm, 1.6 mm and 1.8 mm for Groups A, B, C, and D, respectively. Standardized artificial carious lesions were created and demineralized dentin was excavated. After excavation, the cavities were analyzed using: (a) the tactile method, (b) caries-detection dye to stain demineralized dentin, as proposed by Smales & Fang, and (c) Demineralized Tissue Removal index, as proposed in this study. Statistical analysis was performed using Fisher, Spearman correlation coefficient, kappa, Kruskal-Wallis and Miller tests (P < 0.05). Results: The three methods of evaluation showed no significant difference between Groups A vs. B, and C vs. D, while statistically significant differences were observed between Groups A vs. C, A vs. D, B vs. C and B vs. D. Based on the results of this study, the size of occlusal access significantly affected the efficacy of demineralized tissue removal.

Novel colloidal materials for high-throughput screening applications in drug discovery and genomics

Tracking the reaction history is the means of choice to identify bioactive compounds in large combinatorial libraries. The authors describe two approaches to synthesis on silica beads: a) addition of a reporter dye tag during each synthesis step (see Figure), which attaches itself to the bead by colloidal forces, and b) encapsulating arrays of fluorescent dyes into the beads to encode them uniquely, for recognition with a flow cytometer after each reaction step.

Molecular Lego (R): non-centrosymmetric alignment within interdigitating layers

(E)-N-Hexadecyl-4-[2-(4-octadecyloxynaphthyl) ethenyl] quinolinium bromide, which has a wide-bodied chromophore and terminal n-alkyl groups, adopts a U-shape when spread at the air-water interface but a stretched conformation when compressed to ca. 35 mN m(-1). The high-pressure phase has a narrow stability range prior to collapse but may be extended from 40 to 60 mN m(-1) by co-spreading the dye in a 1 : 1 ratio with docosanoic acid. The mixed Langmuir-Blodgett (LB) film has a monolayer thickness of 4.6 +/- 0.2 nm which decreases to 2.5 +/- 0.1 nm layer(-1) in the bulk, the reduction arising from an interdigitating layer arrangement, both top and bottom. It is the first example of LB-Lego(R) and, in addition, represents the only fully interdigitating structure with non-centrosymmetrically aligned chromophores. They are tilted 38 degrees from the substrate normal. The second-harmonic intensity increases quadratically with the number of layers, i.e. as I-(N)(2 omega) = (I(1)N2)-N-2 omega, with a second-order susceptibility of chi ((2))(zzz) = 30 pm V-1 at 1064 nm for refractive indices of n(omega) = 1.55 and n(2 omega) = 1.73, d = 2.5 nm layer(-1) and phi = 38 degrees. Angle resolved X-ray photoelectron spectra (XPS) of these films provide no evidence of the bromide counterion, which suggests that it is replaced by OH 2 or HCO3-, which occur naturally in the aqueous subphase, or C21H43COO- from the co-deposited fatty acid. This probably applies to all cationic dyes deposited by the LB technique.

Multi-fluorescent silica colloids for encoding large combinatorial libraries

Large chemical libraries can be synthesized on solid-support beads by the combinatorial split-and-mix method. A major challenge associated with this type of library synthesis is distinguishing between the beads and their attached compounds. A new method of encoding these solid-support beads, 'colloidal bar-coding', involves attaching fluorescent silica colloids ('reporters') to the beads as they pass through the compound synthesis, thereby creating a fluorescent bar code on each bead. In order to obtain sufficient reporter varieties to bar code extremely large libraries, many of the reporters must contain multiple fluorescent dyes. We describe here the synthesis and spectroscopic analysis of various mono- and multi-fluorescent silica particles for this purpose. It was found that by increasing the amount of a single dye introduced into the particle reaction mixture, mono- fluorescent silica particles of increasing intensities could be prepared. This increase was highly reproducible and was observed for six different fluorescent dyes. Multi-fluorescent silica particles containing up to six fluorescent dyes were also prepared. The resultant emission intensity of each dye in the multi-fluorescent particles was found to be dependent upon a number of factors; the hydrolysis rate of each silane-dye conjugate, the magnitude of the inherent emission intensity of each dye within the silica matrix, and energy transfer effects between dyes. We show that by varying the relative concentration of each silane-dye conjugate in the synthesis of multi-fluorescent particles, it is possible to change and optimize the resultant emission intensity of each dye to enable viewing in a fluorescence detection instrument.

Liquid distribution in wet granulation: dimensionless spray flux

This study investigates binder distribution in wet granulation and focuses on the nucleation zone, which is the area where the liquid binder and powder surface come into contact and form the initial nuclei. An equipment independent parameter, dimensionless spray flux Psi (a), is defined to characterise the most important process parameters in the nucleation process: solution flowrate, powder flux, and binder drop size. Ex-granulator experiments are used to study the relationship between dimensionless spray flux, process variables and the coverage of binder fluid on the powder surface. Lactose monohydrate powder on a variable speed riffler passed under a flat spray once only. Water and 7% HPC solution at two spray pressures were used as binders. Experiments with red dye and image analysis demonstrate that changes in dimensionless spray flux correlate with a measurable difference in powder surface coverage. Nucleation experiments show that spray flux controls the size and shape of the nuclei size distribution. At low Psi (a), the system operates in the drop controlled regime, where one drop forms one nucleus and the nuclei size distribution is narrow. At higher Psi (a), the powder surface cakes creating a broader size distribution. For controlled nucleation with the narrowest possible size distribution, it is recommended that the dimensionless spray flux be less than 0.1 to be in the drop-controlled regime. (C) 2001 Elsevier Science S.A. All rights reserved.

Exploiting the versatility of human cytochrome P450 enzymes: The promise of blue roses from biotechnology

The cytochrome P450 (P450) enzymes involved in drug metabolism are among the most versatile biological catalysts known. A small number of discrete forms of human P450 are capable of catalyzing the monooxygenation of a practically unlimited variety of xenobiotic substrates, with each enzyme showing a more or less wide and overlapping substrate range. This versatility makes P450s ideally suited as starting materials for engineering designer catalysts for industrial applications. In the course of heterologous expression of P450s in bacteria, we observed the unexpected formation of blue pigments. Although this was initially assumed to be an artifact, subsequent work led to the discovery of a new function of P450s in intermediary metabolism and toxicology, new screens for protein engineering, and potential applications in the dye and horticulture industries.

Functional heterogeneity within rhodamine123(lo) Hoechst33342(lo/sp) primitive hemopoietic stem cells revealed by pyronin Y

Objective. The aim of this study was to determine the function of primitive hematopoietic stem cells (PHSC) at phases G(0) and G(1) of the cell cycle. Materials and Methods. A combination of supravital dyes rhodamine123 (Rh), Hoechst33342 (Ho), and pyronin (PY) was used to isolate the G(0) and G(1) subsets of PHSC. A competitive repopulation assay was used to evaluate their in vivo function. Results. We confirmed that the Rh(lo)Lin(-)Kit(+)Sca-1(+) PHSC were relatively quiescent when compared with the more mature Rh(hi)Lin(-)Kit(+)Sca-1 HSC and Rh(hi)Lin(-)Kit(+)Sca-1(-) progenitors. In addition, cells with Rh(lo)Lin(-)Kit(+)Sca-1(+), Rh(lo)Ho(lo)Lin(-)Sca-1(+), or Rh(lo)Ho(sp)Lin(-)Sca-1(+) phenotypes identified the same cell population. We further subfractionated the Rh(lo)Ho(lo/sp)Lin(-)Sca-1(+) PHSC using PY into PYlo and PYhi subsets. Limiting dilution analysis revealed that the frequency of long-term in vivo competitive repopulating units (CRU) of the (PYRhHolo/sp)-Rh-lo-Ho-lo PHSC was 1 in 10 cells, whereas there was at least a three-fold lower frequency in those isolated at the G(1) phase (PYhi) We found a dose-dependent PY-mediated cytotoxicity that at moderate concentration affected most of the murine hematopoietic compartment but spared the early HSC compartment. Conclusion. Our data confirm that the HSC compartment is hierarchically ordered on the basis of quiescence and further extend this concept to PY-mediated cytotoxicity. PY supravital dye can be used to reveal functional heterogeneity within the (RhHolosp)-Ho-lo PHSC population but is of limited use in dissecting the relatively more mature hematopoietic stem/progenitor cell population. (C) 2001 International Society for Experimental Hematology. Published by Elsevier Science Inc.