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.