Influence of Polishing Systems on Surface Roughness of Composite Resins: Polishability of Composite Resins

OBJECTIVES

The objective of this in vitro study was to compare, with a threshold value of 200 nm, the surface roughness obtained when using 12 different polishing systems on four different composite resins (microfill, nanofill, and two nanohybrids).

METHODS AND MATERIALS

A total of 384 convex specimens were made using Durafill VS, Filtek Supreme Ultra, Grandio SO, and Venus Pearl. After sandblasting and finishing with a medium-grit finishing disc, initial surface roughness was measured using a surface roughness tester. Specimens were polished using 12 different polishing systems: Astropol, HiLuster Plus, D♦Fine, Diacomp, ET Illustra, Sof-Lex Wheels, Sof-Lex XT discs, Super-Snap, Enhance/Pogo, Optrapol, OneGloss and ComposiPro Brush (n=8). The final surface roughness was measured, and data were analyzed using two-way analysis of variance. Pairwise comparisons were made using protected Fisher least significant difference.

RESULTS

There were statistical differences in the final surface roughness between polishing systems and between composite resins (p<0.05). The highest surface roughness was observed for all composite resins polished with OneGloss and ComposiPro Brush. Enhance/Pogo and Sof-Lex Wheels produced a mean surface roughness greater than the 200-nm threshold on Filtek Supreme Ultra, Grandio SO, and Venus Pearl. Data showed that there was an interaction between the composite resins and the polishing systems.

CONCLUSIONS

A single polishing system does not perform equally with all composite resins. Except for Optrapol, multi-step polishing systems performed generally better than one-step systems. Excluding Enhance/Pogo, diamond-impregnated polishers led to lower surface roughness. Durafill VS, a microfill composite resin, may be polished more predictably with different polishers.

Red-Light Effects Sensitized by Methylene Blue on Nitrate Reductase from Spinach (Spinacia oleracea L.) Leaves

Nitrate reductase from spinach (Spinacia oleracea L.) leaves, which had been inactivated in vitro by incubation with NADH and cyanide, was fully reactivated in minutes when irradiated in anaerobic conditions with red light in the presence of methylene blue. Both the rate and the extent of reactivation increased with light intensity (6 to 100 W·m-2) and dye concentration (1 to 10 μM). On the contrary, photoreactivation was completely abolished when NADH or ethylenediaminetetra-acetic acid were present during irradiation. We propose that methylene blue, when photo excited, exhibits a redox potential positive enough to reoxidise the CN--re-duced molybdenum complex settled in the inactive enzyme, thus causing its reactivation.

On the other hand, prolonged irradiation of nitrate reductase, under air and in the presence of methylene blue, promoted an oxygen-dependent irreversible inactivation of the two partial activities of the enzyme. This inactivation was markedly enhanced in 77% deuterated water and greatly prevented by azide, which indicates that singlet oxygen is the species primarily involved in the photooxidative inactivation of the enzyme.

The narrow specificity pyroglutamate amino peptidase degrading TRH in rat brain is an ectoenzyme

In order to determine the pathway of extracellular metabolism of the thyrotropin releasing hormone (pyroglu-his-proNH(2)) in brain, the topographical organization of pyroglutamate aminopeptidase II on the plasma membrane was investigated. Its activity was only slightly increased when intact brain synaptosomes were lysed by osmotic shock or detergent treatment. Trypsin treatment of intact synaptosomes destroyed 70-80% of enzyme activity without affecting lactate dehydrogenase. Pyroglutamate aminopeptidase II activity was present in primary cultures of foetal mice cortical cells. It was detected in intact cells, was not released by the cells and its activity was not increased by saponin pretreatment. Trypsin treatment of the cells reduced pyroglutamate aminopeptidase II by 70% but did not affect pyroglutamate aminopeptidase I and lactate dehydrogenase. These data support that brain pyroglutamate aminopeptidase II is an ectoenzyme. They suggest that this enzyme could be responsible for thyrotropin releasing hormone extracellular catabolism in brain.

[European Guidelines on Cardiovascular Disease Prevention in Clinical Practice. Spanish adaptation of the CEIPC 2008]

We present the Spanish adaptation made by the CEIPC of the European Guidelines on Cardiovascular Disease Prevention (CVD) in Clinical Practice 2008. This guide recommends the SCORE model for risk evaluation. The aim is to prevent premature mortality and morbidity due to CVD through the management of its related risk factors in clinical practice. The guide focuses on primary prevention and emphasizes the role of the nurses and primary care medical doctors in promoting a healthy life style, based on increasing physical activity, change dietary habits, and non smoking. The therapeutic goal is to achieve a Blood Pressure < 140/90 mmHg, but among patients with diabetes, chronic kidney disease, or definite CVD, the objective is <130/80 mmHg. Serum cholesterol should be < 200 mg/dl and cLDL<130 mg/dl, although among patients with CVD or diabetes, the objective is <100 mg/dl (80 mg/dl if feasible in very high-risk patients). Patients with type 2 diabetes and those with metabolic syndrome must lose weight and increase their physical activity, and drugs must be administered whenever applicable, to reach body mass index (BMI) guided and waist circumference objectives. In diabetic type 2 patients, the objective is glycated haemoglobin <7%. Allowing people to know the guides and developing implementation programs, identifying barriers and seeking solutions for them, are priorities for the CEIPC in order to transfer the recommendations established into the daily clinical practice.

Viscoelasticity of Asphalts Modified with SEBS Copolymers Functionalized with Various Amounts of Maleic Anhydride

It is known that the microstructure of polymer-modified asphalts (PMA) depends strongly of the characteristics of the polymer. The modifier polymer improves the mechanical properties of pure asphalt when used in paved roads. In this work, asphalt is modified using reactive polymers obtained via functionalization of styrene-ethylene/butylene-styrene (SEBS) copolymers in solution using various amounts of benzoil peroxide (BPO) as initiator and maleic anhydride (MAH). The resulting functionalized copolymer (SEBS-g-MAH) with variable amounts of grafting (variable reactivity) is blended with the asphalt at small contents (2–4 wt. %). The amount of MAH grafting was determined by FTIR, 1HNMR, GPC, DSC and by titration with KOH, and this amount is readily correlated with the improvement of the mechanical properties and thermal stability of the asphalt. In addition, the limit of the polymer-asphalt compatibility is determined for these systems.

Modeling of the Linear Viscoelastic Behavior of Partially Hydrogenated Polymer-Modified Asphalts

The modeling of the linear viscoelastic behavior of asphalt modified with 8 wt % of partially hydrogenated poly (styrene-butadiene-styrene) triblock copolymers is analyzed. Time-temperature superposition renders master curves in a wide range of frequencies and temperatures, from which a logarithmic distribution of relaxation times is obtained using the multimode Maxwell model. In addition, the linear viscoelastic data is analyzed with an emulsion model and agreement is only found at high frequencies, where the contribution from interfacial tension is negligible. Enhanced polymer-asphalt interactions at low frequencies evidenced by a decreasing limiting slope of the storage modulus in the terminal region are not predicted by the emulsion model, and relative agreement is found considering two viscoelastic phases. The Cole-Cole representation and the fractional Maxwell model predict the viscosity of asphalt in the complex plane, but strong asymmetry in the semicircular arcs is found in the polymer-modified asphalt blends. The Havriliak-Negami model accounts for asymmetric arcs and represents the data better in specific ranges of frequency.

Asphalt Modified by Partially Hydrogenated SBS Tri-Block Copolymers

This work examines the modification of asphalt with hydrogenated poly (styrene-butadiene-styrene) copolymer containing different amounts of butadiene and ethylene-co-butylene. The polymer composition can be described generically as poly (styrene−[(butadiene)1−x−(ethylene−co−butylene)x]−styrene), where x is the hydrogenated fraction of the molecule. These hydrogenated (SBEBS) copolymers were produced by in-situ hydrogenation following a Ziegler-Natta catalytic reaction of poly (styrene-butadiene-styrene) tri-block copolymers (SBS), which were previously synthesized by anionic polymerization. Control over the hydrogenation time produces SBEBS polymers with various degrees of saturation of the polybutadiene block, as characterized by FTIR, HNMR, differential scanning calorimetry (DSC) and gel permeation chromatography (GPC). Polymer-modified asphalts (PMA) were obtained by a high-temperature mixing process with AC-20 asphalt (Salamanca, Mexico) and SBS or SBEBS copolymers. PMA samples were characterized before and after high-temperature storage tests by fluorescence microscopy, rheometry, and mechanical tests. Results indicate that PMA obtained from SBEBS contain a polymer matrix with well-dispersed asphalt rich phase, with improved mechanical and thermal stability over those PMA produced with SBS. Compatibility between SBEBS and the aromatic fraction of maltenes can explain the dispersion of the polymer in asphalt and the enhanced properties.

Resin-dentin interfacial ultrastructure and microtensile dentin bond strength after five-year water storage

OBJECTIVE

To evaluate a total-etch three-step adhesive system's resin-dentin interfacial ultrastructure and microtensile dentin bond strength (microTBS) after multi-year storage in water.

METHODS

Resin composite crowns were formed on 600 grit SiC flattened extracted human molars using a total-etch three-step adhesive system (Optibond FL, Kerr) and a hybrid resin composite (Prodigy, Kerr). microTBS specimens were fabricated and placed in water with 0.5% chloramine T at 37 degrees C until respective static load to failure testing at one-month, six-months and five-year storage. Failure modes were determined by scanning electron microscopy. The interfacial ultrastructure of the resin-dentin interface was analyzed by transmission electron microscopy (TEM) at 48-hours and 44-months storage. microTBS was modeled with Weibull distribution for survival analysis and failure curve distributions were analyzed by the Wald chi-square statistic for significant differences at alpha=0.05.

RESULTS

The characteristic tensile strength (sigma omicron) at one-month, six-months and five-year storage was 52.63, 14.77 and 23.57 Mpa, with a Weibull modulus of 3.04, 1.56 and 1.28, respectively. Failure distributions for all groups were significantly different (p<0.0001) with one-month > five-year > six-months. TEM interfacial morphology demonstrated hydrolytic degradation of hybrid layer components at 44-months storage.

SIGNIFICANCE

The decrease in tensile strength and changes in ultrastructure may be caused by water sorption and resultant hydrolytic degradation of the adhesive joint.

Accumulation of astaxanthin and lutein in Chlorella zofingiensis (Chlorophyta)

When grown photoautotrophically, Chlorella zofingiensis strain CCAP 211/14 accumulates a significant amount of valuable carotenoids, namely astaxanthin and lutein, of increasing demand for use as feed additives in fish and poultry farming, as colorants in food, and in health care products. Under standard batch-culture conditions, this microalgal strain exhibits high values of both growth rate (about 0.04 h(-1)) and standing cell population (over 10(11) cells l(-1), or 7 g dry weight l(-1)). Lutein, in a free (unesterified) form, was the prevalent carotenoid during early stages of cultivation (over 0.3 pg cell(-1), equal to 4 mg g(-1) dry weight, or 20 mg l(-1) culture), whereas esterified astaxanthin accumulated progressively, to reach a maximum (over 0.1 pg cell(-1), equal to 1.5 mg g(-1) dry weight, or 15 mg l(-1) culture) in the late stationary phase. A differential response of lutein and astaxanthin accumulation was also recorded with regard to the action of some environmental and nutritional factors. C. zofingiensis CCAP 211/14 represents a unique model system for analyzing the differential regulation of the levels of primary (lutein) and secondary (astaxanthin) carotenoids. Relevant also from the biotechnological viewpoint, this photosynthetic organism, with outstanding attributes for fast photosynthetic growth and carotenoid accumulation, might prove most valuable for its application to the mass production of either or both lutein and astaxanthin.

Thyrotropin-releasing hormone-induced down-regulation of pyroglutamyl aminopeptidase II activity involves L-type calcium channels and cam kinase activities in cultures of adenohypophyseal cells

Released thyrotropin-releasing hormone (TRH) is inactivated by a narrow specificity ectopeptidase, pyroglutamyl aminopeptidase II (PPII), present in brain and lactotrophs. Various hypothalamic/paracrine factors, including TRH, slowly (in hours) regulate the activity of PPII on the surface of adenohypophyseal cells. TRH-induced down-regulation was mimicked by protein kinase C (PKC) activation but was not affected by inhibition of PKC. Adenylate cyclase activation can also down-regulate PPII. The purpose of this study was to identify elements of the transduction pathway used by TRH to regulate PPII activity. In primary cultures of female adenohypophyseal cells, activation of the stimulatory G protein or adenylate cyclase produced an effect additive to that of TRH; inhibition of protein kinase A activity did not interfere with TRH action. However, regulation of PPII activity by TRH was inhibited by a phospholipase C beta inhibitor or chelation of intracellular calcium. L-type calcium channels (LCC) agonists mimicked TRH action and their effect was not additive with that of TRH. Antagonists of LCC channels and inhibitors of calmodulin or calcium/calmodulin-dependent protein kinase blocked TRH action. Therefore, TRH-induced calcium entry through L-type calcium channels and the activity of calcium/calmodulin-dependent protein kinase are required for TRH effect on PPII activity in primary cultures of adenohypophyseal cells. This pathway may coregulate PPII and prolactin biosynthesis in response to TRH.

Microtensile bond strength of eleven contemporary adhesives to dentin

PURPOSE

To evaluate the microtensile bond strength (microTBS) of eleven contemporary adhesives to dentin, including three one-step self-etch systems, four two-step self-etch systems, three two-step total-etch systems, and one three-step total-etch system.

MATERIALS AND METHODS

Resin composite (Z100) was bonded to flat, mid-coronal dentin from 33 extracted human third molars using the adhesives strictly according to the respective manufacturer's instructions. After storage overnight in 37 degrees C water, the bonded specimens were sectioned into 3 to 6 slabs of approximately 1 mm thickness and 2.5 mm width. They were then trimmed into an hourglass shape resulting in an interface area of approximately 1 mm2, and subsequently subjected to microTBS testing with a crosshead speed of 1 mm/min.

RESULTS

The microTBS varied from 30.0 MPa for the one-step self-etch adhesive Prompt L-Pop 2 (ESPE) to 63.1 MPa for the three-step total-etch adhesive OptiBond FL (Kerr), the latter being the only one that significantly differed from all other microTBS values. Although not significantly different, one-step self-etch adhesives tended to have lower microTBS than two-step self-etch and two-step total-etch adhesives. Specimen failures during sample preparation occurred with Prompt L-Pop 2 (4 pretesting failures out of 17 specimens) and NRC/Prime & Bond NT (7 pretesting failures out of 14 specimens).

CONCLUSION

Adhesives with simplified application procedures, either following a total-etch or self-etch approach, produced lower bond strengths to dentin than a conventional three-step total-etch adhesive. Some concern exists regarding the consistency in bonding effectiveness to dentin of some self-etch adhesives.

Early detection of maedi-visna (ovine progressive pneumonia) virus seroconversion in field sheep samples

The aim of this work was to investigate whether an enzyme-linked immunosorbent assay (ELISA) was useful for early detection of maedi-visna virus (MVV) infection in sheep under field conditions. An ELISA based on p25 recombinant protein and a gp46 synthetic peptide was used. Sequentially obtained serum samples (n = 1,941) were studied for 4 years. ELISA results were compared with those of the agar gel immunodiffusion (AGID) test, and results of both tests were compared with a reference result established using consensus scores for at least 2 of 3 serologic techniques (AGID, ELISA, and western blotting, which was used to resolve result discrepancies between the other 2 techniques). A total of 247 discrepancies were observed between ELISA and AGID. Of these, 131 were due to an earlier detection of 120 sera by the ELISA and 11 sera by AGID. The remaining discrepancies (116) were due to the presence of false reactions in both tests. Fewer false-negative results were found by ELISA than with AGID (6 vs. 69 sera, respectively), whereas the number of false-positive results was virtually the same for ELISA and AGID (21 vs. 20, respectively). In relation to the reference result, ELISA sensitivity and specificity were 97.8% and 98.2%, respectively, whereas values for AGID were 76.3% and 98.3%, respectively. The agreement between ELISA and the reference result was higher than that between AGID and the reference result (K value: 0.96 and 0.77, respectively). A variation in the ELISA signal (based on optical density) was observed during the study period, suggesting different antibody levels throughout the animal's life. The ELISA was useful for detecting MVV-infected sheep in field conditions and has potential for use in control and eradication programs.

Cavity preparation devices: effect on microleakage of Class V resin-based composite restorations

PURPOSE

To evaluate the effect of cavity preparation device (i.e. carbide bur, diamond bur, air abrasive, Sonicsys, and Er:YAG laser) on microleakage of Class V resin-based composite (RBC) restorations, the tooth restoration interface and dentin ultrastructure.

MATERIALS AND METHODS

Eight groups (n=18) of 9 human molars each were prepared on the buccal and lingual surfaces for Class V RBC restorations using five preparation devices: Group 1: carbide bur #8 round; Group 2: diamond bur #801; Group 3: KCP 1000 air abrasion unit; Group 4: Sonicsys Approx.; Group 5: Er:YAG laser; Group 6: carbide bur plus air abrasive; Group 7: carbide bur plus laser, and Group 8: laser without etching. Circular cavity preparations, 3 mm diameter and 1.5 mm deep, were cut at the CEJ on the buccal and lingual surfaces of each tooth. A bevel was placed on the enamel margin. All cavities were restored using Single Bond adhesive system and Silux Plus according to manufacturer's directions, with the exception that no etchant was used with Group 8. After thermocycling, specimens were tested for microleakage using silver nitrate methodology. Dye penetration data was collected and subjected to non-parametric statistical analysis. SEM analysis of the dentin-RBC interface, as well as the effect of each cavity preparation device on the surface of dentin was performed.

RESULTS

Microleakage did not occur in enamel for any method of cavity preparation when the enamel was etched prior to adhesive application. Kruskal-Wallis One-way ANOVA revealed differences in dentin microleakage among the tested groups at alpha=0.05. Mann-Whitney Test for Paired Comparisons at alpha=0.01 demonstrated significantly greater dentin microleakage in Groups 5 and 7 compared to all groups except Group 3 (air abrasive). Although Group 8 had the least microleakage in dentin, this was not significantly different from Groups 1, 2, 4 and 6. SEM observation revealed hybridization at the dentin-resin interface for all groups except for Group 8 (laser prepared, non-etched). Surface analysis showed differences related to the operating mode of each preparation device.

CLINICAL SIGNIFICANCE

The method of cavity preparation did not affect microleakage in etched enamel. When using a laser for cavity preparation, enamel should be etched although not etching dentin may help to improve marginal seal.

Lutein production by Muriellopsis sp. in an outdoor tubular photobioreactor

The effect of dilution rate, mixing and daily solar cycles on lutein and biomass productivity of the green unicellular alga Muriellopsis sp. has been studied, throughout the year, in an outdoor tubular photobioreactor. Highest productivity values, for both lutein (about 180 mg m(-2) per day) and biomass (about 40 g (dry weight) m(-2) per day) were achieved on May and July. Values for the optimal dilution rate varied, being lower in May (0.06 h(-1)) than in November (0.09 h(-1)). Similar values for photosynthetic efficiency (about 4%) were recorded throughout the year, indicating that optimization of culture conditions was achieved for each experimental period. Along the daily solar cycle, there was a fast increase of lutein content of Muriellopsis sp. in response to irradiance during the early hours of daytime, with maximal lutein content (about 6 mg (g dry weight)(-1)) being recorded at noon, and decreasing slowly, thereafter. An increase in cell growth was observed following the establishment of maximum lutein/chlorophyll ratio, which might indicate a role for lutein in protecting cells from photodamage.

Association between microtensile bond strength and leakage in the indirect resin composite/dentin adhesively bonded joint

PURPOSE

Develop a methodology to correlate microtensile bond strength (microTBS) and leakage within the same site of a specimen and evaluate the predominate debond and leakage pathways.

MATERIALS AND METHODS

A Class II (MO) slot cavity was prepared in 37 extracted human molars and restored with indirect resin composite restorations. The restored teeth were thermocycled 300X between 5 and 55 degrees C and then stained with silver. Two specimens per tooth were obtained by diamond saw sectioning for measurement of leakage (microm) and microtensile bond strength (MPa) at the gingival wall and then tested for association with regression analysis. Scanning electron microscopy techniques and energy dispersive spectroscopy (EDS) were used to evaluate the debond and leakage pathways.

RESULTS

Association between leakage and bond strength was not significant (t=1.31, p=0.198). All 74 samples debonded within the joint, predominantly at the hybrid layer-adhesive resin region with only one specimen including a small portion of resin cement in the debond pathway. Secondary and backscatter imaging and EDS analysis showed leakage in all samples that involved the hybrid layer.

CONCLUSION

This study demonstrates a feasible method for evaluating leakage and bond strength at the joint interface within the same specimen.

Regulation of adenohypophyseal pyroglutamyl aminopeptidase II activity by thyrotropin-releasing hormone and phorbol esters

Thyrotropin-releasing hormone (TRH) is inactivated by a narrow specificity ectopeptidase, pyroglutamyl aminopeptidase II (PPII), in the proximity of target cells. In adenohypophysis, PPII is present on lactotrophs. Its activity is regulated by thyroid hormones and 17beta-estradiol. Studies with female rat adenohypophyseal cell cultures treated with 3,3',5'-triiodo-L-thyronine (T3) showed that hypothalamic/paracrine factors, including TRH, can also regulate PPII activity. Some of the transduction pathways involve protein kinase C (PKC) and cyclic adenosine monophosphate (cAMP). The purpose of this study was to determine whether T3 levels or gender of animals used to propagate the culture determine the effects of TRH or PKC. PPII activity was lower in cultures from male rats. In cultures from both sexes, T3 induced the activity. The percentages of decrease due to TRH or PKC were independent of T3 or gender; the percentage of decrease due to cAMP may also be independent of gender. These results suggest that T3 and hypothalamic/paracrine factors may independently control PPII activity in adenohypophysis, in either male or female animals.

The physical properties of packable and conventional posterior resin-based composites: a comparison

BACKGROUND

The authors compared the physical properties of three packable hybrid resin-based composites with those of a conventional hybrid and a microfill composite material advocated for use as posterior restorative materials. They evaluated diametral tensile strength, or DTS; compressive strength, or CS; flexural strength, or FS; and depth of cure, or DC.

METHODS

The authors studied the following resin-based restorative materials: three packable composites, Alert Condensable Composite (Jeneric Pentron), SureFil High Density Posterior Restorative (Dentsply Caulk) and Solitaire (Heraeus Kulzer); one conventional hybrid composite, TPH Spectrum (Dentsply Caulk); and one microfill, Heliomolar Radiopaque (Ivoclar-Vivadent). The authors evaluated DTS, CS, FS and DC, according to American National Standards Institute criteria. They made scanning electron micrographs of the packable resin-based composites.

RESULTS

Results demonstrated that the conventional hybrid, TPH Spectrum, had significantly greater DTS and FS than other resin-based composites. Alert and SureFil had comparable DTS and FS, which were significantly greater than Heliomolar's DTS and FS. Solitaire had significantly lower DTS and FS than all other resin-based composites. SureFil had the highest CS, followed by TPH Spectrum, Solitaire and Alert, which were comparable and had significantly greater CS than Heliomolar. TPH Spectrum and Alert had significantly greater DC than all other resin-based composites, followed in decreasing order by SureFil, Solitaire and Heliomolar.

CONCLUSION

While the packable composites tested in this study had physical properties superior to those of the microfill composite, they were no better suited for use as a posterior restorative material than was the conventional hybrid resin-based composite.

CLINICAL IMPLICATIONS

Packable composites may be easier for clinicians to handle than conventional resin-based composites; however, their physical properties were not superior to those of the conventional small-particle hybrid resin-based composite. In addition, these materials may have the clinical drawback of increased wear and surface roughness that was seen with early, large-particle composite restorative materials.

Metal surface treatment: characterization and effect on composite-to-metal bond strength

This study evaluated the effect of four methods of metal surface preparation and the use of silane on the bond strength between resin and a Noble metal alloy. SEM Examination and x-ray energy-dispersive spectroscopy (EDS) of the various metal surface treatments was also performed. One-hundred metal disks were cast in a Noble metal alloy (Porcelain #76). Ninety disks were polished flat and the surfaces received one of four abrasive treatments (n = 20). 1) Roughening with a diamond bur at high speed; 2) Air abrasion with an intraoral sandblaster using alumina particles; 3) Air abrasion with KCP-2000 and 4) Air abrasion with an intraoral sandblaster using silanated silica covered alumina particles (CoJet-Sand). Half the specimens from each treatment group (n = 10) were silanated prior to bonding procedures (All-Bond 2 adhesive system, Pertac-Hybrid composite). Specimens were stored in distilled water at 37 degrees C and thermocycled prior to shear strength testing. The 10 remaining metal disks were used for scanning electron microscopy and x-ray energy-dispersive spectroscopy (EDS). Scanning electron microscopy examined the micromorphology of the metal surfaces produced by the four abrasive treatments and x-ray energy-dispersive spectroscopy (EDS) to evaluate changes in surface composition. Two untreated disks served as controls. One-way ANOVA and Tukey's HSD post-hoc test demonstrated that air abrasion with CoJet-Sand and silane resulted in significantly higher resin-to-metal bond strength than all other metal surface treatments, while roughening with a diamond bur produced the lowest bond strength. Resin-to-metal bond strength was similar for all other particle abrasive treatments with or without silane. Using silane significantly improved bond strength only for metal surfaces treated with CoJet-Sand. An increase in Al concentration was observed on metal surfaces sandblasted with aluminum oxide, and an increase in the concentration of both Al and Si was observed on surfaces air-abraded with CoJet-Sand.

Effect of two abrasive systems on resin bonding to laboratory-processed indirect resin composite restorations

PURPOSE

This study compared two methods of surface roughening or preparation, with or without the use of proprietary surface wetting agents, to evaluate their effect on resin cement adhesion to the following laboratory-processed, indirect restorations: Artglass (AG), belleGlass HP (BG), Concept (C), and Targis (T). Methods of surface roughening or preparation included microetching with aluminum oxide (AO): 50 microns at 34 psi and silanized silica coating, CoJet-Sand (CJ): 30 microns at 34 psi. Artglass and Concept were tested with and without the use of their respective surface wetting agents: Artglass Liquid (AGL) and Special Bond II (SB).

MATERIALS AND METHODS

One hundred twenty specimens, each consisting of a pair of cylinders (7.0 x 3 mm and 4.3 x 3 mm) were fabricated. The larger cylinder or base was embedded in self-curing resin in a phenolic ring, and bonding surfaces were finished with 320-grit silicon carbide paper. Specimen pairs for each restorative material were randomly assigned to treatment groups (n = 10) and received the following surface treatments prior to cementation: group 1 (AG/AO/+AGL), group 2 (AG/AO/-AGL), group 3 (AG/CJ/+AGL), group 4 (AG/CJ/-AGL), group 5 (BG/AO), group 6 (BG/CJ), group 7 (C/AO/+SB), group 8 (C/AO/-SB), group 9 (C/CJ/+SB), group 10 (C/CJ/-SB), group 11 (T/AO), and group 12 (T/CJ). Specimen pairs were cemented with a dual-cure resin cement (Dual) and a standardized force of 1 MPa. Specimens were light-cured 40 seconds per side (80 s total), then thermocycled 300 times at between 5 degrees and 55 degrees C. Shear bond strengths (MPa) were determined using a Zwick Materials Testing Machine at a crosshead speed of 5 mm per minute.

RESULTS

One-way analysis of variance (ANOVA) and Duncan's multiple range test (alpha = 0.05) by restoration type indicated no significant differences in shear bond strength between BG group 5 (29.8 +/- 5.8), BG group 6 (28.3 +/- 4.3), T group 11 (29.3 +/- 4.9), and T group 12 (29.0 +/- 4.4). Shear bond strength in AG group 3 (35.9 +/- 3.4) was significantly higher than in AG group 4 (32.4 +/- 4.0) and equal to that in AG group 2 (31.9 +/- 3.9) and AG group 1 (30.0 +/- 3.6). Shear bond strength in C group 10 (24.8 +/- 5.7) was equal to that in C group 9 (21.5 +/- 2.9), but was higher than in C groups 7 (19.4 +/- 3.1) and 8 (19.3 +/- 3.4).

CLINICAL SIGNIFICANCE

Under the conditions of this study, the combination of CoJet-Sand and Artglass Liquid resulted in the highest bond strength for Artglass restorations. Microetching with CoJet-Sand or aluminum oxide followed by wetting with an unfilled adhesive was an effective surface pretreatment for dual-cure resin cementation of the four proprietary indirect resin-ceromer restorations tested.

The spectrum of composites: new techniques and materials

BACKGROUND

During the past 25 years, advances in adhesive technology and composite-based resins have provided dentists and patients with new treatment options. This technology provides patients with more tooth-conserving and highly esthetic restorations.

CLINICAL IMPLICATIONS

This article reviews advances in composite-based resin materials. It discusses composition and classification of current resin-based composite. It also reviews techniques for successful placement of these materials and provides a discussion of current concepts of polymerization.

Chemical and rheological properties of an extracellular polysaccharide produced by the cyanobacterium Anabaena sp. ATCC 33047

The cyanobacterium (blue-green alga) Anabaena sp. ATCC 33047 produces an exopolysaccharide (EPS) during the stationary growth phase in batch culture. Chemical analysis of EPS revealed a heteropolysaccharidic nature, with xylose, glucose, galactose, and mannose the main neutral sugars found. The infrared (IR) spectrum of EPS showed absorption bands of carboxylate groups. The average molecular mass of the polymer was 1.35 MDa. Aqueous dispersions at EPS concentrations ranging from 0.2% to 0.6% (w/w) showed marked shear-thinning properties (power-law behavior). Linear dynamic viscoelastic properties showed that the elastic component was always higher than the viscous component. Viscous and viscoelastic properties demonstrated the absence of conformational changes within the concentration range studied. Stress-growth experiments revealed that 0.4% and 0.6% (w/w) EPS dispersions showed thixotropic properties. A detailed comparison of the linear dynamic viscoelasticity, transient flow, and decreasing shear rate flow curve properties was made for 0.4% (w/w) dispersions of xanthan gum (XG), Alkemir 110 (AG), and EPS. Viscoelastic spectra demonstrated that the EPS dispersion turned out to be more "fluidlike" than the AG and XG dispersions. The flow indexes indicated that the EPS dispersion was less shear-sensitive than that of XG, showing essentially the same viscosity, that is, >50 s(-1). The fact that viscosities of EPS and AG dispersions were not substantially different within the shear-rate range covered must be emphasized, in relation to EPS potential applications. The rheological behavior of EPS dispersions indicates the formation of an intermediate structure between a random-coil polysaccharide and a weak gel.

Carotenoid content of chlorophycean microalgae: factors determining lutein accumulation in Muriellopsis sp. (Chlorophyta)

Fifteen strains of chlorophycean microalgae have been investigated with regard to their carotenoid profile. Lutein, beta-carotene and violaxanthin were present in virtually all of the strains, lutein, in general, being the most abundant carotenoid, whereas canthaxanthin and astaxanthin were found in some strains only. Chlorella fusca SAG 211-8b, Chlorococcum citriforme SAG 62.80, Muriellopsis sp., Neospongiococcum gelatinosum SAG B 64.80 and Chlorella zofingiensis CCAP 211/14 exhibited high lutein levels, the latter strain containing in addition substantial amounts of astaxanthin. Muriellopsis sp. was further characterized, since besides a high lutein content (up to 35 mg l(-1) culture), it had the highest growth rate (up to 0.17-0.23 h(-1)) and maximal standing cell density (up to 8 x 10(10) cells l(-1) culture). These levels of lutein are in the range of those reported for astaxanthin in Haematococcus and for beta-carotene in Dunaliella, microalgae of recognized interest for the production of these carotenoids. Lutein content of Muriellopsis sp. increased during the exponential phase of growth, with the highest value being recorded in the early stationary phase. Maximum levels of lutein in Muriellopsis sp. cultures were recorded at 20-40 mM NaNO3, 2-100 mM NaCl, 460 micromol photon m(-2) s(-1), pH 6.5 and 28 degrees C, conditions which were, in general, also optimal for cell growth. Growth-limiting conditions, such as pH values of 6 or 9 and a temperature of 33 degrees C, were found to stimulate carotenogenesis in Muriellopsis sp. This strain represents a potential source of lutein, a commercially interesting carotenoid of application in aquaculture and poultry farming, as well as in the prevention of cancer and diseases related to retinal degeneration.

Characterization of soybean Bradyrhizobium strains adapted to the Brazilian savannas

Brazilian soils are originally free from soybean bradyrhizobia and the first inoculants were brought to the country in this century, but a search for adapted strains started immediately and still continues. A strain selection program was established at Embrapa based on the reisolation of strains after a long period of adaptation to the soils followed by a search for variant genotypes with higher N(2) fixation capacity and competitiveness. A second approach of this program consists of searching for variant colonies of a single strain with higher N(2) fixation rates and competitiveness, following a short period of adaptation to the soil. In this study, using both approaches, strains belonging to three serogroups, CB 1809, 532C and SEMIA 5020, were obtained. In general, the variant strains showed differences in colony morphology (mucoidy) but produced similar protein and lipopolysaccharide profiles. Within serogroup CB 1809, containing variants obtained via the second approach, a low level of DNA polymorphism was detected relative to the parental genotype by ERIC and REP-PCR. However, within the two other serogroups, containing variant strains obtained via the first approach, a high level of polymorphism in ERIC and REP-PCR fingerprints was observed relative to the putative serologically related parental genotypes. These results show that a great variability can be detected following adaptation of Bradyrhizobium strains to the soil, although other potential explanations for the DNA polymorphisms observed are discussed. Some of the variant strains obtained by both methodologies were found to have higher rates of N(2) fixation and almost all were more competitive than the parental genotypes, suggesting that it is possible to select variant strains which can contribute to an improved plant N nutrition status.

Colorimetric assessment of laser and home bleaching techniques

PURPOSE

This study recorded in vitro color change of three tooth bleaching techniques that included laser-activated hydrogen peroxide and two concentrations of carbamide peroxide.

MATERIALS AND METHODS

Forty extracted human central incisors were exposed to argon laser-activated 35% H2O2, 10% carbamide peroxide, or 20% carbamide peroxide. A fourth group (control) did not receive any bleach treatment (n = 10/group). Commission International de l'Eclariage (CIE) L*a*b* coordinates were recorded prior to bleaching (baseline), at 1 week, and at 2 weeks. The color difference (delta E*ab) between baseline and subsequent measurements was calculated.

RESULTS

The control group did not demonstrate significant color difference over time (p > .05). The laser group was not statistically different from the control group (p > .01). The color difference of the 10% and 20% carbamide peroxide groups was statistically different from the control group (p < .01).

CLINICAL SIGNIFICANCE

Exposure to 20% carbamide peroxide produced the greatest perceivable change in color. The recommended one-time application of laser-activated hydrogen peroxide did not demonstrate any perceivable color change. The clinician should be aware that additional or longer applications may be required.

Amalgam shear bond strength to dentin using single-bottle primer/adhesive systems

PURPOSE

To evaluate the in vitro shear bond strengths (SBS) of a spherical amalgam alloy (Tytin) to dentin using several single-bottle primer/adhesive systems both alone: Single Bond (SB), OptiBond Solo (Sol), Prime & Bond 2.1 (PB), One-Step (OS) and in combination with the manufacturer's supplemental amalgam bonding agent: Single Bond w/3M RelyX ARC (SBX) and Prime & Bond 2.1 w/Amalgam Bonding Accessory Kit (PBA). Two, three-component adhesive systems, Scotchbond Multi-Purpose (SBMP) and Scotchbond Multi-Purpose Plus w/light curing (S + V) and w/o light curing (S+) were used for comparison.

MATERIALS AND METHODS

One hundred eight extracted human third molars were mounted lengthwise in phenolic rings with acrylic resin. The proximal surfaces were ground to expose a flat dentin surface, then polished to 600 grit silicon carbide paper. The teeth were randomly assigned to 9 groups (n = 12), and dentin surfaces in each group were treated with an adhesive system according to the manufacturer's instructions, except for S + V specimens, where the adhesive was light cured for 10 s before placing the amalgam. Specimens were then secured in a split Teflon mold, having a 3 mm diameter opening and amalgam was triturated and condensed onto the treated dentin surfaces. Twenty minutes after condensation, the split mold was separated. Specimens were placed in distilled water for 24 hrs, then thermocycled (300 cycles, between 5 degrees C and 55 degrees C, with 12 s dwell time). All specimens were stored in 37 degrees C distilled water for 7 days, prior to shear strength testing using a Zwick Universal Testing Machine at a cross-head speed of 0.5 mm/min.

RESULTS

The highest to the lowest mean dentin shear bond strength values (MPa) for the adhesive systems tested were: S + V (10.3 +/- 2.3), SBX (10.2 +/- 3.5), PBA, (6.4 +/- 3.6), SOL (5.8 +/- 2.5), SBMP (5.7 +/- 1.8), S+ (4.8 +/- 2.3), PB (2.7 +/- 2.6), SB (2.7 +/- 1.1) and OS (2.5 +/- 1.8). One-way ANOVA and Duncan's Multiple Range Test indicated significant differences among groups. SBX and S + V produced significantly higher amalgam to dentin shear bond strengths than all other adhesive systems. Bond strengths of amalgam to dentin for the single-bottle adhesives, SOL and PBA were comparable to the three-component systems, SBMP and S+ and were significantly greater than OS, SB and PB (P < 0.05).

[Health, healthy family and healthy child: views and relationships of community agents]

This article reports the experience lived by the authors during their training time in one of the practical activities of the Nursing Teaching Course. In the context of a Continued Education Project developed with community agents of the Family Health Program, the research approaches a discussion that was triggered off on a meeting about the subject: "Health, Healthy Family and Healthy Child", when some manifestations of persons involved in the project were argued. The authors concluded that, as a pedogogic strategy, the use of group dynamics enlarges the possibilities of using the experience and knowledge that determines the person's action, as a teaching-learning process base.

[AIDS and the hospital institution: why to think/rethink about this relationship?]

Through the report of a situation occurred within the hospital institution, the article tries to focus on the way how the AIDS question has been thought in this enviroment. Furthermore, it broaches the possibility of compromising the hospital as a space for reflection and discussion. Through the analysis, it articulates the subjects implicated in the situation with gender, sex, sexuality, race and ethic questions. It also relates AIDS to risk groups, as a meaning to promote the occlusion, and to power relations within the hospital institution. As a conclusion, the article proposes more questions for us to think over our practice as professionals inserted in this context.

Current status of luting agents for fixed prosthodontics

STATEMENT OF THE PROBLEM

The long-term clinical outcome of fixed prosthodontic treatment depends, in part, on the use of adhesives that can provide an impervious seal between the restoration and the tooth. There are several types of available luting agents, each possessing unique properties and handling characteristics. No one product is ideal for every type of restoration.

PURPOSE

The purpose of this article is to review available dental luting agents, discuss improvements and drawbacks in newly formulated adhesives, and present the indications for their use.

RESULTS

Each cement type is physically and chemically unique. A single adhesive will not suffice in modern day clinical practice.

Evaluation of acidic primers in microleakage of Class 5 composite resin restorations

The purpose of this in vitro study was to evaluate the marginal seal of two adhesive systems on class 5 composite resin restorations. Two adhesive systems that use acidic primers were used in this study: Clearfil Liner Bond 2 and Denthesive II. Scotchbond Multi-Purpose was used as a control. Class 5 cavity preparations were made at the CEJ (half of the preparation was in enamel and half in dentin/cementum) of 60 extracted human molars. Both systems were used with and without etching. The control group was used with etching only. Composite resin restorations were placed, light cured for 40 seconds, and polished. All specimens were thermocycled 500 times. The specimens were immersed in erythrosin B, tetra-iodo-fluorescent 2% solution, then sectioned to obtain 600 mm-thick sections. These were examined under X13.2 magnification, and the degree of dye penetration was measured in microns. A chi-square test demonstrated no significant differences in microleakage among groups for either dentin (P = 0.54) or enamel (P = 0.35).

TRH inactivation in the extracellular compartment: role of pyroglutamyl peptidase II

TRH (pGlu-His-ProNH2) inactivation in the brain and pituitary extracellular fluid is reviewed. While TRH could be eliminated by alternative mechanisms, i.e. uptake or internalization, modification, hydrolysis by broad specificity peptidases such as pyroglutamyl peptidase I and prolyl endopeptidase, evidence accumulates to support a specific neuroectopeptidase as the main mechanism responsible for its extracellular inactivation. Pyroglutamyl peptidase II (PPII; E.C. 3.4.19.6) is a narrow specificity zinc metallopeptidase hydrolyzing the pyroglutamyl-histidyl peptide bond of TRH. PPII is an integral membrane protein with a small intracellular domain, a transmembrane segment and a large extracellular domain that contains the catalytic site. It is therefore idealy situated to degrade TRH present in the extracellular space. PPII is highly enriched in brain, specifically present in neuronal cells. PPII inhibition enhances recovery of TRH released in vitro. In situ hybridization studies demonstrate that PPII mRNA colocalizes with TRH-receptor mRNA in various brain regions. However, the existence of exceptions suggest that alternative inactivation mechanisms for TRH may operate. PPII activity is regulated in various pharmacological or pathophysiological conditions which alter TRH transmission. It is also present in adenohypophysis, preferentially on lactotrophs, where its activity is stringently regulated by hormones and hypothalamic factors. PPII activity regulation may contribute to adjust TRH neural and hormonal transmissions.

Adhesive composite inlays for the restoration of cracked posterior teeth associated with a tongue bar

While body piercing has become fashionable in contemporary society, numerous health risks are directly related to this trend. Tongue piercing in particular presents several concomitant complications for the attending clinician, including the possibility of soft tissue infection or damage to the natural dentition or existing restorations. Clinicians must be proficient in the selection of the proper materials and techniques utilized to treat affected patients. This article details a comprehensive clinical protocol for the use of adhesive composite inlay restorations for cracked posterior teeth.

Multifactorial modulation of TRH metabolism

1. Thyrotropin releasing hormone (TRH), synthesized in the paraventricular nucleus of the hypothalamus (PVN), is released in response to physiological stimuli through median eminence nerve terminals to control thyrotropin or prolactin secretion from the pituitary. 2. Several events participate in the metabolism of this neuropeptide: regulation of TRH biosynthesis and release as well as modulation of its inactivation by the target cell. 3. Upon a physiological stimulus such as cold stress or suckling, TRH is released and levels of TRH mRNA increase in a fast and transient manner in the PVN; a concomitant increase in cfos is observed only with cold exposure. 4. Hypothalamic cell cultures incubated with cAMP or phorbol esters show a rise in TRH mRNA levels; dexamethasone produces a further increase at short incubation times. TRH mRNA are thus controlled by transsynaptic and hormonal influences. 5. Once TRH is released, it is inactivated by a narrow specificity ectoenzyme, pyroglutamyl peptidase II (PPII). 6. In adenohypophysis, PPII is subject to stringent control: positive by thyroid hormones and negative by TRH; other hypothalamic factors such as dopamine and somatostatin also influence its activity. 7. These combined approaches suggest that TRH action is modulated in a coordinate fashion.

Polymerization of composite resins: argon laser vs conventional light

The purpose of this in vitro study was to compare polymerization of composite resins, as indicated by microhardness, at increasing depths using an argon laser versus a conventional light. For this, a microfill (Silux Plus) and a hybrid (TPH) composite resin were used. Five specimens per group were prepared by injecting composite into a rectangular split Teflon mold 3 x 3 x 8 mm. Specimens were then polymerized by either a 40-second exposure to the conventional visible light (VL) or a 30-, 20-, or 10-second exposure to the argon laser (AL). Specimens were stored in a light-proof container for 24 hours at 37 degrees C, then Knoop hardness was determined. Four measurements were taken for each specimen at depths of 0, 1, 2, 3, and 4 mm from the exposed surface. No significant differences were found in surface hardness for either the microfill or hybrid composite regardless of light source or exposure time. For the microfill composite, at 1, 2, 3, and 4 mm depths, VL40 and AL30 exposures produced comparable hardness, which was significantly greater than that found for AL20 and AL10. At a depth of 4 mm, exposure to VL40 resulted in significantly greater hardness compared to AL20. With AL10 exposure, the composite was too soft to determine hardness. The hybrid composite had comparable hardness to a depth of 3 mm for VL40, AL30 and AL20.

Multiple hypothalamic factors regulate pyroglutamyl peptidase II in cultures of adenohypophyseal cells: role of the cAMP pathway

In the adenohypophysis, thyrotrophin-releasing hormone (TRH) is inactivated by pyroglutamyl peptidase II (PPII), a TRH-specific ectoenzyme localized in lactotrophs. TRH slowly downregulates surface PPII activity in adenohypophyseal cell cultures. Protein kinase C (PKC) activation mimics this effect. We tested the hypothesis that other hypothalamic factors controlling prolactin secretion could also regulate PPII activity in adenohypophyseal cell cultures. Incubation for 16 h with pituitary adenylate cyclase activator peptide 38 (PACAP; 10(-6) M) decreased PPII activity. Bromocryptine (10(-8) M), a D2 dopamine receptor agonist, or somatostatin (10(-6) M) stimulated enzyme activity and blocked the inhibitory effect of [3-Me-His2]-TRH, a TRH receptor agonist. Bromocryptine and somatostatin actions were suppressed by preincubation with pertussis toxin (400 ng ml(-1)). Because these hypophysiotropic factors transduce some of their effects using the cAMP pathway, we analysed its role on PPII regulation. Cholera toxin (400 ng ml(-1)) inhibited PPII activity. Forskolin (10(-6) M) caused a time-dependent decrease in PPII activity, with maximal inhibition at 12-16 h treatment; ED50 was 10(-7) M. 3-isobutyl-1-methylxanthine or dibutiryl cAMP, caused a dose-dependent inhibition of PPII activity. These data suggest that increased cAMP down-regulates PPII activity. The effect of PACAP was blocked by preincubation with H89 (10(-6) M), a protein kinase A inhibitor, suggesting that the cAMP pathway mediates some of the effects of PACAP. Maximal effects of forskolin and 12-O-tetradecanoylphorbol 13-acetate were additive. PPII activity, therefore, is independently regulated by the cAMP and PKC pathways. Because most treatments inhibited PPII mRNA levels similarly to PPII activity, an important level of control of PPII activity by these factors may be at the mRNA level. We suggest that PPII is subject to 'homologous' and 'heterologous' regulation by elements of the multifactorial system that controls prolactin secretion.

Interfacial ultrastructure of the resin-enamel region of three adhesive systems

PURPOSE

To observe the resin/enamel interface produced by different adhesive systems.

MATERIALS AND METHODS

A conventional three-step smear layer removing adhesive system (Scotchbond Multi-Purpose), a two-step smear layer removing adhesive system (Prime & Bond), and a two-step smear layer dissolving adhesive system containing a self-etching primer (Panavia 21) were evaluated. Flat enamel surfaces were obtained from approximal surfaces of 18 extracted human molars. A total of 36 surfaces were collected and divided into three groups of 12 samples. One-half of each specimen in each group was etched with 35% phosphoric acid prior to the application of each adhesive system, with the second half being kept unetched. Subsequently, resin composite was placed and polymerized for 40 seconds. The samples were fractured and immersed into HCl and NaOCl solutions, followed by critical point drying and sputter coating for examination with a field emission scanning electron microscope.

RESULTS

In the etched samples, Panavia 21 and Scotchbond Multi-Purpose showed more consistent resin tag penetration than did Prime & Bond. Unetched Prime & Bond and Scotchbond Multi-Purpose samples showed minimal or no adhesive penetration in enamel surfaces.

Surface treatment techniques for resin composite repair

PURPOSE

To compare bond strengths of fresh resin composites to previously polymerized ("aged") composites following various surface treatments.

MATERIALS AND METHODS

Eighty Pertac Hybrid (PH) and an equal number of Silux Plux (SLX) specimens were fabricated and stored for 1 week prior to surface treatment. The specimens were then polished and stored for an additional 24 hours prior to final surface treatment. The surface treatments included use of one of the following: (1) diamond bur (DB), (2) microetcher with 50 microns Al2O3@80 psi pressure (ME), (3) high-pressure air abrasion with 27 microns Al2O3@psi, (KCP), or (4) low-pressure silicate ceramic deposition using 30 microns particles@34 psi (CJ-S) with a microetcher. Half of the samples were treated with a silanating agent. Fresh resin composite (same type as used for the aged specimen) was bonded to the treated surfaces, and specimens were then stored 24 h and thermocycled 300 x at 5 degrees and 55 degrees C prior to testing for shear bond strength. Two-way ANOVA was used to determine significant differences between mean shear bond strengths for both composite materials.

RESULTS

Significant differences were found between the groups for both surface treatment and silane use (P < 0.05). The interaction between the two main effects was also significant (P < 0.05). Overall, the highest bond strengths were found when the low-pressure silicate ceramic deposition system (CJ-S) was used, with or without silane.

Evaluation of adhesive systems using acidic primers

PURPOSE

To evaluate in vitro the dentin and enamel shear bond strength of two adhesive systems that contain acidic primers.

MATERIALS AND METHODS

Clearfil Liner Bond 2 (CLB2) and Denthesive II (DTII), containing acid primers were used with (ETCH) and without (NOET) etching. Scotchbond Multi-Purpose (SBMP) was utilized as a control. Sixty flat enamel and dentin bonding sites were prepared to 600 grit on extracted human molars. Both acidic primer systems were used with (ETCH) and without etching (NOET) for both enamel and dentin surfaces. The control group used etching only. After applying primer and adhesive, a microfill composite (Silux Plus) was placed in a 2.5 mm diameter matrix on the tooth surface, and polymerized for 40 seconds. All specimens were thermocycled 500 times. Shear bond strengths were determined using a Zwick testing machine.

RESULTS

One-way ANOVA revealed significant differences among groups for enamel (P = 0.0001) and dentin (P = 0.0002). Duncan's multiple range test (alpha = 0.05) revealed that enamel shear bond strength of DTII-ETCH was equal to that of CLB2-NOET and these were significantly greater than CLB2-ETCH, SBMP and DTII-NOET. For dentin, bond strengths for CLB2-ETCH and CLB2-NOET were significantly greater than DTII-NOET.

Interfacial micromorphology and shear bond strength of single-bottle primer/adhesives

OBJECTIVES

This study was conducted 1) to characterize through SEM analysis the resin-dentin interface produced by single-bottle primer/adhesives and a three-component system [Scotchbond Multi-Purpose (3M Dental)] and 2) to evaluate the shear bond strength to dentin of these adhesive systems.

METHODS

Single-bottle primer/adhesives [Bond 1 (Jeneric/Pentron), Single Bond, (3M Dental Products); One Step (Bisco Inc.), OptiBond Solo (Kerr Corp.), Prime & Bond 2.1 (L.D. Caulk-Dentsply), Syntac Single-Component (Ivoclar-Vivadent), Tenure Quilk with Fluoride (Den-Mat)] were used according to manufacturers' instructions to bond resin composite to flat dentinal surfaces of extracted human third molars (n = 15). All samples were thermocycled 300x. Twelve specimens per group were used to measure shear bond strength and three specimens were used to evaluate the interfacial morphology under SEM. A one-way ANOVA and Turkey's test were used to assess the results.

RESULTS

Mean shear bond strengths in MPa +/- SD for the groups ranged from 22.27 +/- 4.5 MPa for Single Bond to 7.6 +/- 3.9 MPa for Syntac Single-Component. The statistical analysis indicated that Single Bond produced significantly higher (p < 0.001) bond strengths than Syntac Single-Component, Prime & Bond 2.1, Bond 1 and Tenure Quik With Fluoride. Bond strengths for Syntac Single-Component were significantly lower than One-Step, OptiBond Solo, Scotchbond Multi-Purpose Plus and Single Bond. SEM examination clearly revealed the formation of a distinct hybrid layer for all adhesive systems; however, minor variations in ultrastructure existed among products.

SIGNIFICANCE

Some single-bottle primer/adhesive present in vitro bond strengths and hybrid layer formation similar to those found for the conventional three-component adhesive system tested.

Resin-dentin shear bond strength and interfacial ultrastructure with and without a hybrid layer

The purpose of this study was (1) to evaluate the effect of a 2-minute exposure of 5% NaOCl following acid conditioning of the dentin on the shear bond strength for two adhesive systems and (2) to examine the ultrastructure of the resindentin interface under SEM. The mesial and distal surfaces of 28 extracted human third molars were ground to expose dentin, then polished with 600-grit SiC. Teeth were randomly assigned to four test groups (n = 14) and received the following treatments: Scotchbond Multi-Purpose (SBMP)--Samples were conditioned with 37% phosphoric acid, rinsed and left moist, SBMP primer and adhesive were applied according to the manufacturer's directions, and Restorative Z-100 composite resin was bonded to the dentin surface. SBMP/NaOCl--The same procedures were followed as for SBMP except the surfaces were treated with 5% NaOCl for 2 minutes, after acid conditioning. All-Bond 2 (AB2)--The same technique was followed as for SBMP, using AB2 according to the manufacturer's recommendations. AB2/NaOCl--The same procedure was followed as for SBMP/NaOCl, using AB2. Specimens were thermocycled in a water bath 300 times between 5 degrees-55 degrees C, then sheared in a Zwick Universal Testing Machine. A one-way ANOVA and Duncan's Multiple Range Test were used for statistical analysis of the data. A 2-minute exposure of dentin to 5% NaOCl following acid conditioning of the dentin had no significant effect on the dentin shear bond strength for Scotchbond Multi-Purpose, but significantly increased the bond strength of All-Bond 2 specimens. The interfacial structure of the dentin to resin bond for two dentin treatments and two adhesive systems was studied morphologically under the scanning electron microscope. Argon ion beam etching and acid demineralization clearly revealed the hybrid layer for the conventional treatment with phosphoric acid and indicated an absence of this resin-impregnated collagen network in those specimens treated with both phosphoric acid and NaOCl.

Effect of in vitro maedi-visna virus infection on adherence and phagocytosis of staphylococci by ovine cells

This work was aimed at studying the effect of maedi-visna virus (MVV) infection in vitro on the ability of sheep cells to adhere to staphylococci (Staphylococcus aureus and Staphylococcus epidermidis), and phagocytose these bacteria. Adherence was studied in sheep choroid plexus cells (SCPC) using an ELISA test and phagocytosis was studied in pulmonary alveolar macrophages (PAM) by chemiluminescence. A 5- and 7-day of in vitro MVV infection resulted in syncytium formation and a significant increased adherence (P < 0.01) of SCPC to bacteria. SCPC endogenous fibronectin was significantly higher (P < 0.01) on days 5 and 7 than on day 0 of MVV infection. A significantly decreased phagocytosis (P < 0.05) was also observed on days 5 and 7 of MVV infection in PAM when compared to MVV-free controls. Comparatively, phagocytosis was highest for S. aureus non-slime producing strains, followed by S. epidermidis, and S. aureus slime producing strains, in that order. Finally, increased expression of both, class I and class II major histocompatibility antigens was also observed in MVV-infected PAM on days 5 and 7, whereas SCPC only demonstrated upregulation of MHC class I. These results, indicative of an alteration of some cell functions in MVV-infected cells, may help to understand interactions between MVV-infected cells and bacteria in simultaneous infections and may provide clues to the possible in vivo interactions of both pathogens.

A novel cytoplasmic structure containing DNA networks in Entamoeba histolytica trophozoites

We report here the presence of cytoplasmic DNA arranged in networks in the trophozoites of the human parasite Entamoeba histolytica. Cytoplasmic DNA was detected in live trophozoites in a structure that we called EhkO, using the fluorescent dye acridine orange, and by in situ hybridization to trophozoites with a rDNA probe. The EhkO was found in the axenically grown clones A, L6 (strain HMI:IMSS) and MAVax (strain MAV) and in the polyxenically grown clone MAVpx (strain MAV). Bacteria present in MAVpx did not cross hybridize with the DNA probe neither in in situ hybridization or in Southern blot experiments. Autoradiography of metabolically [3H]thymidine-labeled trophozoites showed the presence of EhkO, and an EhkO-enriched fraction, purified from a nuclei-free extract and examined by light microscopy, exhibited [3H]thymidine incorporation into this structure. DNA was purified from the EhkO and enriched nuclear fractions and analyzed by transmission electron microscopy. The EhkO fraction contained DNA networks resembling those of trypanosome kDNA, whereas nuclear DNA was present mainly as linear molecules and some circles. Our findings imply that E. histolytica may be taxonomically more closely related to the Trypanosomatidae than previously suspected.

Effect of composite type, light intensity, configuration factor and laser polymerization on polymerization contraction forces

PURPOSE

To investigate the effect of composite type, light intensity, configuration factor and laser polymerization on polymerization contraction force.

MATERIALS AND METHODS

Glass rods (10 pairs/group) were etched with HF acid, silanated, unfilled resin applied and light cured for 20 s. Rods were held vertically in chucks on a Zwick machine. A cylindrical matrix was filled with Silar chemical cure, Silux Plus microfill or Z-100 hybrid composite and the crosshead of the UTM positioned at an inter-rod distance corresponding to a specific ratio of bound to unbound composite surface area (configuration factor or C). Exposure time with the Demetron 401 conventional visible light curing unit (D401) was 40 s/side (80 s total). Exposure times for the ILT Model D5500 air cooled laser (LAC) and Model 5500ABL water cooled laser (LWC) was 20 s/side (40 s total). Experimental groups, n = 10 with constant factors in parentheses, included: (1) Silar chemical-cured (C = 3); (2) Z-100 hybrid (C = 3, D401, 100% intensity); (3) Silux Plus microfill (C = 3, D401, 100% intensity); (4) D401 100% light intensity = 476 mW (Z-100, C = 3, D401); (5) D401 50% intensity = 238 mW (Z-100, C = 3, D401); (6) D401 25% intensity = 119 mW (Z-100, C = 3, D401); (7-9) C = 5, 3 & 1 respectively (Z-100, D401, 100% intensity); (10) D401 with 13 mm tip = 391 mW/cm2 (Z-100, C = 3; D401); (11) D401 with Turbo Tip = 811 mW/cm2 (Z-100, C = 3; D401); (12) LAC = 265 mW, 689 mW/cm2 (Z-100, C = 3); (13) LWC = 365 mW, 1100 mW/cm2 (Z-100, C = 3). One Way ANOVA and Duncan's Multiple Range Test (alpha = 0.05) were performed separately for each variable.

RESULTS

Homogeneous subsets by variable were: composite type Group 1 (25N) < Group 3 (65.8N) < Group 2 (90.4N); intensity Group 6 (73.9N) = Group 5 (77.7N) < Group 4 (90.4N); C-Factor Group 7 (81.8N) < Group 8 (90.4N) < Group 9 (103.4N); light source Group 12 (77.4N) = Group 13 (79.1N) < Group 10 (90.4N) = Group 11.(89.4N). The chemical-cured composite had the lowest maximum polymerization contraction force, the microfill was intermediate and the hybrid composite had the highest recorded force. Increases in light intensity increased the maximum force on the force/time curve. Maximum forces were inversely related to C-factor (C5 < C3 < C1) and directly related to composite volume in a non-rigid system which allowed compliance. Maximum force was not significantly different with the two tips tested on the conventional curing light. Forces obtained with laser polymerization were similar for the two laser groups, which were both statistically lower than the conventional light tested.

Effect of HEMA-containing dentin desensitizers on shear bond strength of a resin cement

PURPOSE

To determine whether the use of two HEMA-containing dentin desensitizing agents [Health-Dent Desensitizer with fluoride (H) or Gluma Desensitizer (G)], when applied at simulated "cavity preparation" and "cementation" appointments, affects the bond strength of lab processed resin composite restorations cemented to dentin.

MATERIALS AND METHODS

The occlusal surfaces of 70 teeth were ground flat to expose dentin and polished to 600 grit. Teeth were randomly assigned to seven groups (n = 10). The treatments were applied in two sessions in order to simulate cavity preparation and cementation appointments. Water (W) was applied as a control instead of a desensitizing agent. H or G were applied for 30 seconds with a rubbing motion (1) at preparation appointment (HW and GW), or (2) at cementation appointment, after etching (WH and WG), or (3) at both sessions (HH and GG). In the control group, water was applied at both sessions (WW). All-Bond 2 and Dual Cement were used according to manufacturers' instructions to cement pre-polymerized resin composite cylinders (4 mm diameter) to the dentin surfaces using a force of 1.0 MPa. Specimens were thermocycled 300x and tested in shear until failure. Data was analyzed using one-way ANOVA and Tukey's HSD test at alpha = 0.05.

RESULTS

Mean bond strength and standard deviations are reported in MPa: GW = 7.4 +/- 6.0; WW = 7.7 +/- 5.8; HW = 8.2 +/- 4.3; WH = 10.8 +/- 6.2; GG = 13.5 +/- 6.0; HH = 13.8 +/- 7.1; WG = 19.9 +/- 8.8. There were no significant differences in bond strengths for GW, WW, HW, WH and GG. Shear bond strength for WG and HH was significantly higher than all groups except for GG. Results of this in vitro study indicate that the use of desensitizers at the preparation and/or cementation appointment does not interfere with bond strengths of resin cement to dentin.

Dentin desensitizing agents: SEM and X-ray microanalysis assessment

PURPOSE

To evaluate the effect of four proprietary dentin desensitizing agents on dentin tubular occlusion, chemical composition changes on the dentin surface, and the effect of saliva and toothbrushing on these agents.

MATERIALS AND METHODS

Fifty dentin discs, obtained from 50 freshly extracted human premolar and molar teeth were used in this study. These were divided into five groups of 10 discs each. Five discs from each group were treated with the desensitizing agents, viewed under the SEM and subjected to energy dispersive X-ray analysis. The other five discs were treated with the desensitizing agents, immersed in artificial saliva, subjected to simulated toothbrushing equivalent to 3 weeks of normal brushing and viewed under the SEM. The agents studied were Sensodyne Dentin Desensitizer, Therma-Trol Desensitizer Gel, Gluma Desensitizer and All-Bond DS.

RESULTS

The Kruskal-Wallis test followed by the Wilcoxon signed-rank test showed that Sensodyne Dentin Desensitizer exhibited the greatest amount of tubular occlusion among the unbrushed samples, followed by Therma-Trol Desensitizer Gel, Gluma Desensitizer and All-Bond DS (P < 0.05) in that order. Toothbrushing increased tubular occlusion in all cases except the Sensodyne Dentin Desensitizer treated samples.