Dentin Permeability and Nanoleakage of Universal Adhesives in Etch-and-rinse vs Self-etch Modes

Clinical Relevance Universal adhesives do not seem to have the ability to effectively seal dentin, regardless of the mode of application. SUMMARY Purpose: This study evaluates the reduction in dentin permeability (P) and the expression of nanoleakage in resin-dentin interfaces made with universal adhesives, comparing the self-etch mode of application with the etch-and-rinse mode of application. Methods and Materials: To measure dentin P at the baseline and after adhesive polymerization, 80 extracted noncarious human third molars (N=80) were sectioned to obtain 0.7-mm-thick midcoronal dentin disks. The specimens were randomly assigned to 8 groups according to the different adhesive systems and application modes used: Scotchbond Universal (SBU; etch-and-rinse [ER] mode vs self-etch [SE] mode), OptiBond XTR (OPT; etch-and-rinse mode vs self-etch mode), Clearfil Universal Bond Quick (CL; etch-and-rinse mode vs self-etch mode), and Adhese Universal (ADH; etch-and-rinse mode vs self-etch mode). A two-way analysis of variance with interaction was used to evaluate the P reduction differences among the groups (α=0.05). Sixteen additional 0.7-mm-thick dentin disks were similarly prepared and treated, immersed in 50 wt% ammoniacal silver nitrate, and then processed according to conventional methods for analysis under transmission electron microscopy. Results: The differences in P reduction among the adhesives were significant (p=0.029). For OPT and ADH (p=0.0304 and p=0.0120, respectively), the P reduction was higher in the ER mode than in the SE mode. For CL and SBU, no differences in P reduction was observed between the two application modes (p>0.05). All the groups showed some pattern of nanoleakage. Conclusions: No adhesive system completely reduced dentin P. Dentin sealing was higher for OPT and ADH in the ER mode, while for SBU and CL, there was no difference between the two modes. All the adhesive systems showed nanoleakage.

Influence of selective etching on the enamel and dentin leakage of three low shrinkage composites in class V restoration

This study determined if prior selective enamel etching affected leakage of enamel/dentin margins in Class V low-shrinkage resin-based composite restorations. Round cavities, centered on the cemento/enamel junction, 2 mm in diameter and 2 mm in depth were prepared on the buccal, palatal or lingual surfaces of premolar teeth to have a total of 60 cavities. One side of the tooth received selective enamel etching and both sides were restored using one of 3 restorative materials (n = 10): Aelite LS posterior/All-bond SE, Estelite Sigma Quick/Bond Force, or Filtek P90/P90 System Adhesive. The teeth were fatigued for 5000 thermal cycles, and the marginal sealing was challenged with 50% ammoniacal silver nitrate. The interface was analyzed and the leakage score was calculated. Two-way ANOVA revealed that Filtek P90 (25.5±17.4) had lower leakage than Estelite Sigma Quick (63.1±34.5) and Aelite LS Posterior (64.2±41.8) with self-etching. With selective etching, the three materials showed reduced leakage in enamel. A significant difference (P <0.05) was found between leakage in enamel and dentin for the Aelite LS Posterior selective etch group and for Estelite Sigma Quick. Selective etching reduced enamel leakage for all materials in one-step self-etch materials. Two-step self-etch adhesives bond better to enamel and dentin than one-step resin-based adhesives.

Synthesis of Silver Nanoparticles Loaded onto Polymer-Inorganic Composite Materials and Their Regulated Catalytic Activity

We present a novel approach for the preparation of polymer-TiO2 composite microgels. These microgels were prepared by the in situ hydrolysis and condensation of titanium tetrabutoxide (TBOT) in a mixed ethanol/acetonitrile solvent system, using poly(styrene-co-N-isopropylacrylamide)/poly(N-isopropylacrylamide-co-methacrylic acid) (P(St-NIPAM/P(NIPAM-co-MAA)) as the core component. Silver nanoparticles (AgNPs) were controllably loaded onto the polymer-TiO2 composite microgels through the reduction of an ammoniacal silver solution in ethanol catalyzed by NaOH. The results showed that the P(St-NIPAM)/P(NIPAM-co-MAA)-TiO2 (polymer-TiO2) organic-inorganic composite microgels were less thermally sensitive than the polymer gels themselves, owing to rigid O–Ti–O chains introduced into the three-dimensional framework of the polymer microgels. The sizes of the AgNPs and their loading amount were controlled by adjusting the initial concentration of [Ag(NH3)2]+. The surface plasmon resonance (SPR) band of the P(St-NIPAM)/P(NIPAM-co-MAA)-TiO2/Ag (polymer-TiO2/Ag) composite microgels can be tuned by changing the temperature of the environment. The catalytic activities of the polymer-TiO2/Ag composite microgels were investigated in the NaBH4 reduction of 4-nitrophenol. It was demonstrated that the organic-inorganic network chains of the polymer microgels not only favor the mass transfer of the reactant but can also modulate the catalytic activities of the AgNPs by tuning the temperature.

Influence of gamma radiation on microshear bond strength and nanoleakage of nanofilled restoratives in Er, Cr:YSGG laser-prepared cavities

ABSTRACT Objective: To evaluate the effect of gamma radiation on microshear bond strength and nanoleakage of nanofilled restoratives in laser-prepared cavities. Materials and Methods: Twenty-eight flat buccal dentin surfaces were prepared for microshear bond strength test. Er, Cr:YSGG laser was used to prepare another 28 Class V cavities on the buccal surfaces of the molars. All teeth were divided into four groups; 1st group: Application of Filtek Z350 nanocomposite material, 2nd group: As the 1st group and then exposure to gamma radiation, 3rd group: Application of Ketac N100 nanoglass ionomer, and the 4th group: As the 3rd group and then gamma irradiated. The bond strength test was performed after storage in artificial saliva for 24 h. For the nanoleakage test, teeth were submerged in a solution of ammoniacal silver nitrate, sectioned, and then examined under a scanning electron microscope. The collected data were statistically analyzed. Results: Nanocomposite showed higher bond strength values than nanoglass ionomer. Despite the fact that gamma radiation did not decrease nanocomposite bond strength, it decreased nanoglass ionomer bond strength. Nanoglass ionomer-restored cavities showed higher silver ion penetration than nanocomposite in both control and gamma-irradiated groups. Conclusion: Gamma radiation has no effect on bond strength and nanoleakage of nanocomposite so that it can be placed before radiotherapy. On the other hand, the bond strength of nanoglass ionomer was adversely affected by gamma radiation.

Morphology and infraciliature of two new earthworm ciliates, Hoplitophrya polymorphus sp. nov. and Anoplophrya simplex sp. nov. (Ciliophora: Oligohymenophorea: Astomatia)

Morphological and infraciliature studies carried out using pyridinated ammoniacal silver carbonate and the 4’,6-diamidino-2-phenylindole (DAPI) staining techniques, led to the identification of two new species of ciliates pertaining to the subclass Astomatia. The first species, Hoplitophrya polymorphus sp. nov., displays two main cellular forms: the elongated form (150–247 μm long and 40–87 μm width) and the stocky form (140–170 μm long and 70–98 μm width). The macronucleus is generally skinny in the elongated forms and ribbon-shaped in the stocky forms. The common feature of the two cellular shapes uniting them in the same species is the identical structure of their skeletal apparatus, a V-shaped element located in an apical depression and bearing skeletal fibres on its ventral face. The second species, Anoplophrya simplex sp. nov., is totally deprived of skeletal apparatus. The cell shape is fusiform and dorsoventrally flattened (105–180 μm long and 65–125 μm width). Six to 12 pulsatile vacuoles form two rows arranged symmetrically on either side of the macronucleus. These two newly identified species highlight the extremely rich diversity of ciliates inhabiting the digestive tract of tropical earthworms.

Photosynthesized silver–polyaminocyclodextrin nanocomposites as promising antibacterial agents with improved activity

Ag nanocomposites were prepared by photoreduction of ammoniacal silver acetate in the presence of poly-{6-[3-(2-(3-aminopropylamino)ethylamino)propylamino]}-(6-deoxy)-β-CD (amCD).

Planar Morphology of Silver Leakage at Resin-Dentin Adhesion Interface

The objectives of this in vitro study is to display the overall planar morphology of leakage at resin-dentin interface using ammoniacal silver nitrate as tracer. Twelve human extracted third molars were used and the occlusal enamel of each tooth was removed. All teeth were divided into four groups of three teeth each and bonded with one of four adhesives (Prime&Bond NT, Adper Prompt, Xeno III, Clearfil S3 Bond) and then a composite resin crown was built up. After storage in water (37°C) for 24 h, all teeth were vertically serially sectioned into stick-shaped specimens the bond interfaces. All specimens were immersed in ammoniacal silver nitrate solution, followed by developing solution and subjected to tensile test and the fracture surface were observed with a SEM. The overall planar morphology of leakage at resin-dentin interface appeared to be various tree-like figures, with character of stem-like portion in the periphery and extending from the periphery to the center of the fractured surface and stretching out a lot of branches. Prim&bond NT presented a couple of big tree-like silver deposition extending to center besides many short tree-like figures located along the periphery. Adper Prompt showed short tree-like figures with many branches. Xeno III displayed tree-like figures with thinner stem portion and more branches. Clearfil S3 Bond presented many short shrub-like figures with fewer branches.

Hybridization quality and bond strength of adhesive systems according to interaction with dentin

ABSTRACT Objective: To evaluate the hybridization quality and bond strength of adhesives to dentin. Materials and Methods: Ten human molars were ground to expose the dentin and then sectioned in four tooth-quarters. They were randomly divided into 5 groups according to the adhesive used: Two single-step self-etch adhesives - Adper Prompt (ADP) and Xeno III (XE), two two-step self-etching primer systems - Clearfil SE Bond (SE) and Adhe SE (ADSE), and one one-step etch-and-rinse system - Adper Single Bond (SB). Resin composite (Filtek Z250) crown buildups were made on the bonded surfaces and incrementally light-cured for 20 s. The restored tooth-quarters were stored in water at 37΀C for 24 h and then sectioned into beams (0.8 mm 2 in cross-section). Maximal microtensile bond strength (μ-TBS) was recorded (0.5 mm/min in crosshead speed). The results were submitted to one-way ANOVA and Tukey′s test (α = 0.05). Thirty additional teeth were used to investigate the hybridization quality by SEM using silver methenamine or ammoniacal silver nitrate dyes. Results: SE reached significantly higher μ-TBS (P < 0.05); no significance was found between ADSE and XE (P > 0.05), and between SB and ADP (P > 0.05); ADSE and XE were significantly higher than SB and ADP (P < 0.05). The bonding interface of SB showed the most intense silver uptake. SE and ADSE showed more favorable hybridization quality than that observed for ADP and XE. Conclusions: The bond strength and hybridization quality were affected by the interaction form of the adhesives with dentin. The hybridization quality was essential to improve the immediate μ-TBS to dentin.

Two Modes of Nanoleakage Expression in Single-step Adhesives

Self-etch adhesives that etch, prime, and bond simultaneously should not exhibit incomplete resin infiltration within hybrid layers. We hypothesized that nanoleakage patterns in these systems are artifacts caused by mineral dissolution in mildly acidic silver nitrate. Resin-dentin interfaces bonded with four single-step, self-etch adhesives were examined for nanoleakage by conventional (pH 4.2) and basic ammoniacal (pH 9.5) silver nitrate and prepared for transmission electron microscopy. All adhesives exhibited a reticular mode of nanoleakage within hybrid layers when conventional silver nitrate was used. With ammoniacal silver nitrate, an additional spotted pattern of nanoleakage was observed within adhesive and hybrid layers. The reticular mode of nanoleakage in self-etch adhesives probably represents sites of incomplete water removal that leads to regional suboptimal polymerization. The spotted pattern identified with the use of ammoniacal silver nitrate probably represents potentially permeable regions in the adhesive and hybrid layers that result from the interaction of the basic diamine silver ions with acidic/hydrophilic resin components.