Bonding of composite resin to contaminated human enamel and dentin

PURPOSE

The purpose of this in vitro study was to evaluate the bond strengths of a bonding agent and composite resin system to human enamel and dentin treated with five contaminants (saliva, plasma, zinc oxide-eugenol cement, noneugenol zinc oxide cement, and handpiece lubricant) using air, moisture, and water as controls.

MATERIALS AND METHODS

A commercial bonding agent (Gluma 2000; Bayer AG, Dormagen, Germany) and its composite (Pekafill; Bayer AG) were applied to tooth structure under two conditions (contaminated and re-etched). Samples were debonded in tension after 24 hours using an inverted, truncated cone bond test.

RESULTS

Among the controls, the highest bond strengths were obtained to enamel (20 MPa) and dentin (12 MPa) with air drying. Contaminants lowered the bond strength by 20% to 100%. Re-etching without additional mechanical preparation resulted in bond strengths similar to the air control.

CONCLUSIONS

Bond strength of Gluma 2000/Pekafill to tooth structure is sensitive to common forms of contamination but can be improved by re-etching after contamination occurs.

Influence of different factors on bond strength of hybrid ionomers

A new generation of filling materials, the hybrid-ionomer cements, has been introduced recently. In many clinical situations these hybrid ionomers may be an alternative to conventional glass-ionomer cements and resins bonded with dentin bonding agents. During the past years research has focused on factors influencing bond strength of dentin bonding systems, but there is not much knowledge about the bond strength of hybrid- and glass-ionomer filling materials under different conditions. Bond strengths of four hybrid ionomers, one conventional glass-ionomer cement, and one cermet cement were determined in superficial and deep, dry and moist dentin using a simplified pulp chamber model. All materials showed significantly higher bond strength to superficial compared to deep dentin. Moisture showed no significant influence on any material neither in deep nor in superficial dentin. Bond strengths of Fuji II LC, Variglass, and Vitremer were distinctly higher than those of the conventional glass-ionomer cement (Ketac-Fil) and the cermet cement (Ketac-Silver), while that of Photac-Fil was not significantly different. Ionomer samples failed cohesively in superficial dentin in over 60% of the samples. The bonding interfaces between Fuji II LC and Variglass and the treated dentin surface showed tags but no distinct hybrid layer. Bond strength is not only dependent on the pretreatment of the dentin, but also on the glass-ionomer resin composition of the material.

Color stability of resin cements after accelerated aging

The color stability of both light- and dual-polymerized samples of three shades of three commercial resin cements was measured using a reflection spectrophotometer after accelerated aging over a period of 179 hours. Porcelite cement was the most color stable, followed by Optec and then 3M. The Optec and Porcelite cements changed color after accelerated aging, but with one exception the changes were not perceptible. Five of six 3M cements had perceptible color changes after accelerated aging, becoming darker and more yellow. The two lighter shades of Optec and 3M changed color more than the darker shade. Most differences between light- and dual-polymerized samples were significant but none was perceptible.

Dye-enhanced ablation of enamel by pulsed lasers

Laser removal of dental hard tissue has been proposed as a replacement for or augmented approach to the dental handpiece. The main limitation for widespread usage of lasers in dentistry has been inefficient ablation of dental hard tissue, accompanied by potential laser-induced damage to the surrounding tissue. The research focuses on a novel approach for enhancement of tissue ablation and confinement of laser interaction to a small tissue volume by controlled placement of an exogenous dye on the enamel surface. Studies were done with both pulsed alexandrite and pulsed Nd:YAG lasers, with indocyanine green and India ink, respectively, used as photo-absorbers. These dye-enhanced laser processes demonstrated the feasibility of this technique for cavity preparation. While control studies produced little or no appreciable crater, average preparation depth for the dye-enhanced ablation was from 1 to 1.5 mm, with a diameter of approximately 0.6 mm. Knoop hardness measurements show that, surrounding the crater, there is small annular region slightly softened by the laser action. SEM studies of the interior structure of the tooth did not show significant damage to the surrounding tissue. Temperature measurement studies indicated that the pulsed nature of the laser, combined with the photo-absorbing dye, effectively prevented significant temperature rise at the pulp. The remarkable effectiveness of this technique in creating cavity preparations and the absence of any notable collateral damage to the surrounding tissue suggest that dye-enhanced pulsed-laser ablation could be used as an alternative to the dental handpiece in selected procedures.

Hemangioblastoma of the optic nerve

A 43-year-old woman presented with progressive loss of vision in the right eye. Magnetic resonance imaging (MRI) showed a prominently enhancing lesion of the optic nerve, thought preoperatively to represent an optic nerve meningioma or optic neuritis. Histological examination of the excised tumor showed this lesion to be hemangioblastoma. Her family history was unremarkable. However, subsequent review of the preoperative MRIs and postoperative imaging studies showed two small cerebellar lesions, probably hemangioblastomas, and renal, pancreatic, and adnexal cysts, establishing the diagnosis of von Hippel-Lindau disease.

Bond strengths of dentinal bonding systems to enamel and dentin

Contemporary, third-generation dentinal bonding products have become highly specialized in producing high bond strengths to dentin. This investigation compared in vitro bond strengths of six dentinal bonding systems and their matched composite resins to human enamel and dentin. The effects of treatment by dentinal primers on enamel bond strengths as well as the effects of phosphoric acid on the strengths of dentinal bonds were measured. The use of dentinal primer on enamel improved the bond strengths of Prisma Universal Bond 3/Prisma APH and XR Bond/Herculite systems and had no effect on Denthesive/Charisma, Scotchbond 2/Silux, and Tenure/Perfection, while the enamel bond strengths of Gluma/Pekalux declined. Pretreatment of dentin with phosphoric acid improved the bond strengths of Denthesive/Charisma, Prisma Universal Bond 3/Prisma APH and XR Bond/Herculite, but had no effect on Gluma/Pekalux, Scotchbond 2/Silux and Tenure/Perfection.

Maxillary molar vertical control with the use of transpalatal arches

Upper molar eruption and its clinical significance to vertical control were measured in a retrospective cephalometric study of 40 patients (20 with and 20 without transpalatal arches) treated in a private practice. Pretreatment and posttreatment cephalometric values were compared to determine how well the patients were matched. No statistically significant differences were noted between control and test groups for the following variables: maxillary and mandibular molar vertical eruption per year, maxillary complex vertical growth per year, effective horizontal condylar growth per year, ratio of effective horizontal pogonion movement to effective vertical pogonion movement, ratio of effective vertical condylar growth to the summation of maxillary, and mandibular vertical molar eruption plus maxillary complex vertical growth, beginning age, and ending age. The control group exhibited statistically greater forward positioning of pogonion and greater effective vertical condylar growth than did the treatment group.

Bond strength of adhesive composites to dental substrates

PURPOSE

The purpose of this study was to evaluate the in vitro bond strength of adhesive and traditional composites to several materials that might be encountered in clinical practice.

MATERIALS AND METHODS

An adhesive composite, an adhesive composite with a bonding agent, and a traditional composite with a bonding agent were bonded to enamel, dentin, amalgam, porcelain, and nickel-chromium-beryllium (Ni-Cr-Be) alloy. Tensile bond strengths were determined after 24 hours storage at 23 degrees C or thermocycling.

RESULTS

The use of an adhesive composite with a bonding agent resulted in increased bond strength to amalgam, porcelain, and dentin, but not to enamel or Ni-Cr-Be alloy at 23 degrees C, when compared with the adhesive composite alone. The adhesive composite with a bonding agent had higher bond strengths to amalgam, porcelain, and dentin than did the traditional composite with bonding agent, but not to enamel or Ni-Cr-Be alloy at 23 degrees C.

CONCLUSIONS

The use of a bonding agent with an adhesive composite produced higher bond strengths than the adhesive composite alone. The traditional composite bonded better to enamel and Ni-Cr-Be alloy than did the adhesive composite. Thermocycling generally had no effect on bond strengths or increased them slightly.

Bond strength of glass ionomers to coronal and radicular dentin

A study was conducted to compare the shear bond strength of a glass-ionomer cement and glass-ionomer base to coronal and radicular dentin. Two different glass ionomers were bonded to paired coronal and radicular human dentin surfaces that had received no surface treatment or had been treated passively for 20 seconds with either 40% or 25% polyacrylic acid. When only the effect of the type of dentin surface was considered, glass-ionomer bonds were greater to radicular dentin than to coronal dentin. With one exception, bond strengths to both dentin surfaces were greater with the base ionomer (Ketac-Bond) than with the luting cement (Ketac-Cem). Bond strengths of both glass ionomers were greater after dentin surface treatment with either 25% or 40% polyacrylic acid than with no treatment.

Hyperostosis cranii ex vacuo: a rare complication of shunting for hydrocephalus

Hyperostosis cranii ex vacuo is a condition that may develop after successful ventricular shunting for hydrocephalus. It is characterized by diffuse thickening of the skull (particularly the inner table) involving the calvarium and the base. It is a diagnosis that distinguishes marked calvarial thickening from thickening of the skull because of other causes. It is an entity that needs to be considered in patients who have diffuse thickening of the skull, have premature closure of sutures, and who have been treated for hydrocephalus in the past.

An ultrastructural analysis of human post-infectious (allergic) encephalomyelitis

A 6-year-old boy developed post-infectious encephalomyelitis and underwent a brain biopsy (10 days after the onset of neurologic symptoms). Electron microscopic analysis of brain showed demyelinated axons, thinly myelinated axons, aberrant remyelination, and numerous phagocytes containing myelin debris. Physical stripping of myelin by pseudopodial extensions of macrophages, as reported in experimental allergic encephalomyelitis, was noted. Hypertrophic and hyperplastic astrocytes were prominent among the phagocytic cells and played an unexpectedly active role in demyelination.

Meningeal meningiomatosis in a child: case report

We report a child with multifocal meningeal lesions demonstrating mixed meningiomatous histologic features. This lesion appears to have evolved over seven years, starting with a brief episode of garbled speech, nausea, and headache at 4.5 years of age. The child was then asymptomatic until 9 when she presented with bilateral leg weakness, in addition to her prior presenting symptoms and communicating hydrocephalus. Meningeal biopsies of two lesions were performed 18 months later. Immunohistochemistry and electron microscopy were needed to substantiate the histologic diagnosis. Radiation therapy to the craniospinal axis and corticosteroids were of some benefit, but more aggressive therapeutic modalities became necessary. The nosology of this lesion is discussed.

Effect of immersion disinfection on properties of impression materials

PURPOSE

Dimensional change and wettability were determined for three addition silicones and a polyether impression material after disinfection by immersion for two 30-minute cycles in 2% acid-potentiated glutaraldehyde.

MATERIALS AND METHODS

Contact angles of water on disks were measured on a goniometer. Dimensional change was determined by change in distance between two reference lines. Contact angle (degree) and dimensional change (percent) of five samples were measured after 0-, 30-, 60-, and 1,440-minute intervals of storage in air and disinfectant.

RESULTS

The contact angle in air increased for two addition silicones and remained constant for the remaining materials. In disinfectant, the contact angle increased for all four materials, with the contact angle of the polyether increasing the least. In air, dimensional change decreased significantly for an addition silicone and a polyether. In disinfectant, the dimensional changes of the addition silicones were not significant, but the polyether increased in dimension after 1,440 minutes.

CONCLUSIONS

Two 30-minute cycles of disinfection in 2% acid-potentiated glutaraldehyde reduced wettability, but had little effect on the dimensional change of the addition silicones and polyethers tested.

Surface roughness of two polished ceramic materials

Conventional and CAD-CAM ceramic restorations often require adjustments that result in a need to reduce surface roughness. Surface roughness resulting from five polishing systems on two ceramics was assessed. Disks of Ceramco II and Dicor MGC ceramic blocks were polished with five combinations of 45, 25, and 10 microns diamonds; a 30-fluted carbide; three silicon carbide-impregnated rubber points; 4 and 1 micron diamond gels; and an aluminum oxide point and two aluminum oxide pastes. Five profilometer average roughness measurements (Ra) were taken of five replications of each step in each sequence. Controls were autoglazed Ceramco II and Dicor MGC ceramic specimens milled with a Cerec diamond wheel. Feldspathic porcelain could be polished smoother than glazed. Dicor ceramic could be polished smoother than Ceramco II ceramic. Finishing diamond points followed by diamond gels produced the smoothest surface. A 30-fluted carbide did not improve smoothness as used. The aluminum oxide point followed by aluminum oxide pastes was equivalent to finishing diamonds and gels for Dicor ceramic.

Effect of dissolution on color of extrinsic porcelain colorants

The effect of in vitro dissolution in acidulated phosphate-fluoride gel on the color of metal ceramic samples having surface metal oxide colorants was determined. Three different colorants were applied using two techniques at two different firing temperatures. The color difference was most apparent when the colorant and glaze were combined with only one firing cycle. All colorants increased in value, but changes in color difference were most evident with the blue colorant. It was concluded that dissolution in acidulated phosphate-fluoride gel does affect the color of extrinsic metallic oxide colorants.

Effects of post-curing on mechanical properties of a composite

The mechanical properties (diametral tensile strength, compressive strength, modulus of elasticity in compression, Knoop hardness, and Rockwell Superficial indentation and recovery) were measured for one light-cured composite (Herculite XRV) post-cured by five different conditions. The post-curing conditions were: boiling water, CRC-100, D.I.-500, Translux EC Light Box, and Triad 2000 with normal light curing as a control. Post-curing Herculite XRV significantly improved the diametral tensile strength (24-39%), Knoop hardness (8-22%) and Rockwell Superficial recovery (3-6%); decreased Rockwell Superficial indentation (0-19%) but did not affect the compressive strength significantly. Modulus of elasticity was not affected, except by the Translux EC Light Box, which increased the modulus by 33%. Post-curing Herculite XRV with the Triad 2000 and Translux EC Light Box produced the most improved properties. Water at 100 degrees C was the least effective of the post-curing methods.

Mechanical properties of direct and post-cured composites

Surface mechanical properties (diametral tensile strength, Knoop hardness, and Rockwell Superficial indentation and recovery) and bulk mechanical properties (compressive strength and modulus of elasticity in compression) of seven composites were measured in vitro under two curing conditions (light-curing only and light-curing plus manufacturer's recommended post-curing). Post-curing improved the Knoop hardeness by 7 to 46% and diametral tensile strength by 15 to 39% of some of the composites. None of the composites had improved compressive strength and only two had an improved modulus of elasticity.

Bond strength of resin cements to microfilled composites

The in vitro bond strengths of three resin cements and a light-cured and a laboratory-processed micro-filled composite were measured. Effects of two surface treatments, and three bond enhancers were analyzed. Resin cements were bonded to sandblasted composite substrates, stored at 37 degrees C in 100% humidity overnight, and debonded in tension. An analysis of variance revealed significant differences among bond strengths. Overall, the composite substrate had the largest effect on bond strength, followed by bond enhancer, cement and, finally, surface treatment. Mean bond strengths ranged from 0.9 to 13.6 MPa. A combination of Concept, Dual Cement, phosphoric acid and Silane produced the lowest mean bond strength (0.9 MPa), while EOS, Dual Cement, hydrofluoric acid, and Heliobond produced the highest recorded mean bond strength (13.6 MPa). In general, the highest bonds were produced using the light-cured composite (EOS), the acrylic monomer (Special Bond II) or the dimethacrylate monomer (Heliobond), the adhesive cement (CR Inlay Cement), and surface treatment with hydrofluoric acid (Comp-Etch). Most of the bond failures (86%) with the laboratory-cured microfilled composite were adhesive. With the light-cured composite, 69% of the failures were mixed adhesive-cohesive types.

Effect of brain irradiation on demyelinating lesions

Demyelinating lesions, such as those in multiple sclerosis, may resemble primary or metastatic brain tumors on CT or MRI, and even be mistaken for neoplasms on biopsy. We encountered five such patients in whom an incorrect diagnosis of CNS neoplasm was made on the basis of radiologic appearance (five) and biopsy (four). All five received radiation therapy, and three chemotherapy. Review of the pathologic findings indicated that the original lesions were not neoplastic but demyelinative. The four patients who received radiation in full tumoricidal doses had unexpectedly poor clinical outcome, suggesting that radiation is especially injurious to patients with demyelinating disease.

In vitro bond strength of two adhesives to enamel and dentin under normal and contaminated conditions

In vitro bond strengths of human enamel and dentin treated with five contaminants were measured with air, water and damp conditions as controls. Two commercial bonding agents (a lower-viscosity, solvent-containing type, AB, and a higher-viscosity, hydrophilic monomer type, SB) and their composites were applied to tooth structure under two conditions (contaminated and re-etched). Samples were debonded in tension after 24 h using an inverted, truncated cone test. Among the controls, the highest bond strengths were obtained with damp conditions for AB (24 MPa) and damp conditions or air for SB (22 MPa) with small differences between enamel and dentin. Most contaminants lowered the bond strength. Re-etching without additional mechanical preparation resulted in bond strengths similar to controls. Bond strengths to tooth structure with the bonding agents tested may be less sensitive to common forms of contamination than typically assumed.

Bond strength of resin cements to a hybrid composite

Tensile bond strengths among three resin inlay cements and a light-cured and a post-cured hybrid composite prepared with two different surface treatments and three different bond-enhancing liquids were measured in vitro. The resin cements were bonded to sandblasted hybrid composite, stored at 37 degrees C in 100% humidity overnight, and debonded in tension. Interfacial bond strengths were affected most by the type of pre-bond surface treatment. Hydrofluoric acid produced weaker bond strengths than surface treatment with phosphoric acid. Post-cured Herculite XRV produced weaker bond strengths than the light-cured Herculite XRV. Porcelite cement produced the highest bond strengths. Of the surface enhancers, the acrylic monomer (Special Bond II) produced the highest bond strengths, regardless of which cement or surface preparation was used. Fracture analysis revealed mostly adhesive failures with hydrofluoric acid treatment in both light-cured and post-cured Herculite.

Bond strength of composite to etched and sandblasted porcelain

In vitro tensile bond strengths of composite to porcelain treated by acid etching or sandblasting were measured. A 9.5% HF gel was applied for 30, 60, 150, or 300 seconds at 23 degrees C. Al2O3 particles were applied as wet-10.2, dry-33.5, dry-48.0, or dry-78.0 microns. Average roughness (Ra) was measured by profilometry before and after each treatment. Both longer etching time and sandblasting using Al2O3 with larger particle sizes produced increased surface roughness of porcelain. Etching with 9.5% hydrofluoric acid gel produced higher bond strengths than sandblasting with a series of Al2O3 particles. Etching longer than 60 seconds produced increased cohesive failures in porcelain, whereas most failures observed with sandblasted surfaces were adhesive.

Bond strength of composite to alloy treated with bonding systems

PURPOSE

The in-vitro bond strengths of a composite bonded to a nickel-chromium-beryllium alloy treated by eight bonding systems were measured after three storage conditions.

MATERIALS AND METHODS

Nickel-chromium-beryllium alloy samples were treated by eight commercial bonding systems including adhesive composite cements, all-purpose bonding agents, and silica-coating systems. A composite was bonded to the alloy samples. Sample groups were stored in water for 24 hours at 23 degrees C, or thermocycled, or stored for 6 months at 23 degrees C and then debonded in tension.

RESULTS

Bond strengths after 24 hours storage were: adhesive composite cements, 14.2 to 22.1 MPa; all-purpose bonding agents, 11.4 to 14.6 MPa; and silica-coating systems, 18.6 to 20.2 MPa. Bond strengths after thermocycling were: adhesive composite cements, 12.6 to 20.6 MPa; all-purpose bonding agents, 9.9 to 17.7 MPa; and silica-coating systems, 11.1 to 19.2 MPa. Bond strengths after 6 months were: adhesive composite cements, 12.0 to 13.1 MPa; all-purpose bonding agents, 8.7 to 14.1 MPa; and silica-coating systems, 14.8 to 18.4 MPa.

CONCLUSIONS

Only two bonding systems showed decreased bond strength after thermocycling, as compared with 24 hours' storage; whereas four bond systems showed decreased bond strength after 6 months' storage. Bond strengths measured after thermocycling were not predictive of those measured after 6 months' storage.

No longer destined to eat their young: satisfaction among Army family practice faculty

In January 1987, all 63 faculty members at Army Family Practice Residencies received satisfaction questionnaires. Fifty-nine faculty (93.8%) responded with 40 (67.8%) being satisfied and 19 (32.2%) dissatisfied. Compared to faculty 7 years prior, these faculty are slightly older, have more practice experience, more opportunities for fellowship training, and are less likely both to have remaining mandatory military obligation and to leave the Army after 3 years. The key areas of faculty development, control over professional life, administration, and departmental goals and objectives truly discriminated satisfaction from dissatisfaction. A strategy to systematically develop potential faculty and reduce dissatisfaction is proposed.

The Inflammatory Myelinopathy of Adreno-Leukodystrophy

Prominent inflammation in the demyelinative lesion of adreno-leukodystrophy (ALD) has suggested an immune-mediated pathogenetic component. Commercially available antibodies to T cells, B cells, macrophages, class I and II molecules, complement, IgG, IgM, IgA, interleukin-1 (IL-1), intercellular adhesion molecule-1 (ICAM-1) and tumor necrosis factor-alpha (TNF) were applied to paraffin sections of formaldehyde-fixed postmortem samples. Twenty-five primary demyelinative lesions from five juvenile ALD, three adult ALD, and three adrenomyeloneuropathic patients were evaluated with appropriate positive and negative controls. Macrophages and astrocytes were the predominant cells detected at the active edge; T lymphocytes, including T4 and CD45R subsets, were nearly as numerous but usually located around vessels within the lesion. B cells and plasma cells, usually containing IgG, were uncommon. The expression of class II molecules, restricted to one adult, was problematic; class I expression was increased in microvascular and other cells. Degraded myelin was labeled with antibodies to C3d and IL-1; IL-1 and ICAM-1 immunoreactivity was seen on microvessels and astrocytes. Tumor necrosis factor-alpha immunoreactivity was detected in macrophages, but more prominently in astrocytes. These data support a natural immune response in the demyelinative lesion of ALD, consisting predominantly of reactive astrocytes, macrophages, T cells and cytokines. A two-stage pathogenetic theory is discussed. The postulated roles of TNF and reactive astrocytes, in concert with a fundamental myelinolytic biochemical defect, suggest a different pathogenetic mechanism and raise novel therapeutic possibilities.

Immunohistochemistry and proliferative activity in Lhermitte-Duclos disease

We have evaluated a recurrence of Lhermitte-Duclos disease by immunohistochemistry for Purkinje cell markers and proliferative activity (proliferating cell nuclear antigen), by electron microscopy and for DNA ploidy (image analysis). While most of the abnormal neurons in the lesion appear to be derived from granule cells, several Purkinje cell specific polyclonal and monoclonal antibodies, including L7, PEP 19 and calbindin, labeled a minor subpopulation. Staining with monoclonal antibodies to proliferating cell nuclear antigen and measuring cell DNA index and ploidy with a cell image analyzer revealed no proliferative activity. Electron microscopy findings were similar to those previously reported. In spite of its recurrence, our findings support the notion that Lhermitte-Duclos disease is malformative, not neoplastic, and that the characteristic neurons are derived predominantly but not exclusively from a non-Purkinje cell source, probably the granule cell.

Cellular tropism and localization in the rodent nervous system of a neuropathogenic variant of Friend murine leukemia virus

BACKGROUND

We studied PVC-211 murine leukemia virus (MuLV) (1), a neuropathogenic variant of Friend MuLV, to determine its cellular tropism and distribution in the nervous system of infected rats and the factors that affected disease expression.

EXPERIMENTAL DESIGN

Rats from five different strains and mice from 3 strains were inoculated intracerebrally or intraperitoneally from birth to 10 days of age and observed for signs of neurologic disease and tumors for 24 weeks. Nervous system pathology, MuLV gp70 expression, and virus production were evaluated weekly for 4 weeks after perinatal infection of Fisher (F344) rats. Blood-brain-barrier integrity and ultrastructure were evaluated in 21-day-old symptomatic infected rats. Microvessel and mixed glial cell cultures were prepared from brains of infected and uninfected 21-day-old F344 rats and evaluated for virus production, MuLV gp70 expression, and the presence of PVC-211 MuLV DNA.

RESULTS

Tremor, ataxia, spasticity, and hindlimb weakness occurred in rats and mice as early as 3 weeks after neonatal infection. Severity, latency, and progression varied among mouse and rat strains but exposure to PVC-211 MuLV before 6 days of age was required for disease expression. Rapid PVC-211 MuLV replication in brain capillary endothelial cells (BCEC) early in the perinatal period was followed by widespread astrogliosis, neuropil vacuolation, and finally, neuronal degeneration in the spinal cord, brainstem, cerebellum, and subcortex. MuLV gp70 expression in vivo increased during infection, was restricted to BCEC, but was not associated with perivascular inflammatory infiltrates. BCEC cultured from microvessel preparations but not astrocytes or microglia in mixed glial cell cultures isolated from infected rats contained PVC-211 MuLV DNA, expressed MuLV gp70, and produced infectious virus.

CONCLUSIONS

The rapid replication of PVC-211 MuLV that occurs in the nervous system of infected rodents is restricted to BCEC. These infected BCEC appear to play a critical role in initiating the astroglial response in this neurodegenerative process through mechanisms that remain to be defined.

The in vivo wear resistance of 12 composite resins

PURPOSE

The in vivo wear resistance of 12 composite resins were compared with an amalgam control using the Latin Square experimental design. Sixteen edentulous patients wearing specially designed complete dentures formed the experimental population.

MATERIALS AND METHODS

The Michigan Computer Graphics Measurement System was used to digitize the surface of the control and composite resin samples before and after 3-month test periods to obtain wear data. The 12 composite resins selected for this investigation based on their published composite classification types were seven fine particle composites, three blends, and two microfilled composite resins. The Latin Square experimental design was found to be valid with the factor of material being statistically different at the 5% level of significance. Wear was computed as volume loss (mm3/mm2), and all of the composites studied had more wear than the amalgam control (P = .001).

RESULTS

After 3 months, the mean (error) of wear of the amalgam was 0.028 (0.006). Means (error) of wear for the 12 composites were ranked from most to least wear by mean wear volume loss.

CONCLUSION

The absence of any relationship between mean wear volume loss and the volume percentage filler was confirmed by the correlation coefficient r = -0.158.

Phospholipids in X-linked adrenoleukodystrophy white matter: fatty acid abnormalities before the onset of demyelination

Changes in fatty acid composition of complex lipids were analyzed in postmortem white matter from a patient with late onset adrenoleukodystrophy (ALD). The specimen showed three regions with progressive myelin breakdown: morphologically normal white matter; areas with active demyelination and perivascular lymphocyte and macrophage infiltration; and areas with marked gliosis. In the morphologically intact region, cholesterol esters were similar in amount and fatty acid composition to those in control tissue, although marked changes were observed in the actively demyelinating area. Galactolipids in these areas were also similar to those in controls. In contrast, glycerophospholipids were increased in amount and in very long chain fatty acids (VLCFA), which are the hallmark of ALD, at the active edge of the demyelinative lesion and even in the apparently intact sample. Further fractionation of the glycerophospholipids by high performance liquid chromatography showed a significant (up to 39-fold) accumulation of hexacosanoic acid (C26:0) in phosphatidylcholine, but not in other phosphatidyl derivatives. The consistent increases in phosphatidylcholine VLCFA in all samples from the ALD brain, which are postulated to represent progressive stages in the development of the disorder, suggest that phosphatidylcholine may be involved in antigen formation and may underlie an immunological basis for the pathogenesis of ALD.

Mechanical properties of new denture resins polymerized by visible light, heat, and microwave energy

Properties of seven newer resins polymerized using a water bath, microwave energy, or by visible light were measured. Generally, the new resins were harder and less flexible but had lower impact strength than did the heat-polymerized, rubber-modified resin (Lucitone). The light-activated urethane dimethacrylate resin (Triad) was the least flexible. Microwave polymerization improved the modulus of elasticity of two resins, decreased the impact strength of one, and had little effect on the properties of two other resins.

In vitro bond strength of silica-coated metal posts in roots of teeth

This study determined the in-vitro bond strength of abrasive-sprayed and silica-coated Ni-Cr-Be posts to roots of extracted teeth using three resin cements (Panavia EX [P], Super-Bond C&B [SB], Prisma Universal Bond 2-Dicor [PUB-D]) and zinc phosphate cement (ZP). There were no significant differences among bond strengths of resin cements (8.8 to 10.8 MPa) bonded to abrasive-sprayed posts, but the bonds were stronger than those obtained using zinc phosphate cement (4.4 MPa). With the silica-coated posts, Super-Bond C&B produced the highest bond strength (14.5 MPa), followed by PUB-D (10.9 MPa), P (7.5 MPa), and ZP (5.4 MPa).

Progressive multifocal leukoencephalopathy in patients with human immunodeficiency virus

Lesions of progressive multifocal leukoencephalopathy (PML) in patients infected with the human immunodeficiency virus (HIV) often have mononuclear cell infiltrates so intense that they obscure the nature of the lesion. This response may be especially prominent in stereotactic biopsies of contrast-enhancing areas. Of 10 consecutive PML lesions biopsied stereotactically, three were markedly, two were moderately, and five were mildly inflamed. There were few to no enlarged oligodendrocytic nuclei with inclusions in the markedly and moderately inflamed lesions. We investigated all biopsies with immunoperoxidase, DNA in situ hybridization, polymerase chain reaction, and Southern immunoblot methodologies for toxoplasmosis and the following viruses: JC, cytomegalovirus, herpes simplex viruses I and II, and human T-cell lymphotropic viruses I, II, and III. We confirmed the presence of JC virus in each lesion; polymerase chain reaction revealed HIV genome only in one. Inflammatory PML lesions in HIV+ patients do not reflect co-infection with toxoplasmosis or viruses commonly seen in these patients. The mononuclear cells are primarily T lymphocytes. Patients with severely inflamed PML lesions, whether HIV+ or not, often show stabilization of symptoms with or without antiviral treatment and have longer lengths of survival than patients with less inflamed lesions.

Relative fit of new denture resins polymerized by heat, light and microwave energy

This study compared in vitro the relative fit of seven denture resins polymerized by different methods to their gypsum casts. Relative fit in the molar-to-molar region of the resin bases on their stone casts was evaluated independently by five evaluators at three times (after processing, after polishing and after storage in water) and ranked using non-parametric statistics. The denture resins polymerized by microwave energy, (Acron MC), low heat, (Perform, 45 degrees C), and visible light, (Triad) fit better after polishing and after storage in water than those resins polymerized at higher temperatures (Lucitone 199, 74 degrees C and Accelar 20, Compak and Permacryl 20, 100 degrees C). The traditional heat-polymerized resin (Lucitone) had an average fit after storage in water.

Bond strength of composites to etched and silica-coated porcelain fusing alloys

In vitro bond strengths of two composite veneering materials to two porcelain fusing alloys were measured utilizing two storage conditions. The alloys were etched or treated with silica applied by blasted, thermal or pyrogenic techniques and then silanated. Bond strengths were higher for the Ni-Cr-Be than the Au-Pd alloy with most values greater than 18 MPa. Bond strengths to etched and silanated Au-Pd alloy were low (less than 6.5 MPa), whereas samples treated with silica and silanated had significantly higher values. Bond strengths to the Ni-Cr-Be alloy were highest with the thermal and pyrogenic silica treatments. After thermocycling, most bond strengths to the Au-Pd alloy decreased, but were the same or higher to the Ni-Cr-Be alloy. Cohesive failures of the opaquers were observed.

Bond strength of composite to porcelain treated with new porcelain repair agents

In vitro tensile bond strengths of composite to porcelain were evaluated using three pretreatments (HF etching, sandblasting, diamond abrasion) of the porcelain, four bonding agents (Clearfil Porcelain Bond, Porcelain Liner M, Porcelain Liner M with Super-Bond C&B, and Scotchprime) and two storage conditions (24 h and thermocycling). The overall coefficient of variation was 27%. Significant differences among bond strengths were observed, with storage condition being the most important factor, followed by bonding agent and then pretreatment. Thermocycling decreased the bond strength of all samples, but samples treated with Scotchprime were affected least. For 24 h storage, Clearfil Porcelain Bond and Scotchprime had bond strengths above 23 MN/m2 to sandblasted porcelain.

Concomitant Creutzfeldt-Jakob and Alzheimer diseases

We report a 69-year-old female with cerebral and cerebellar symptomatology of 15-month duration. At autopsy, both panencephalopathic Creutzfeldt-Jakob and plaque-predominant Alzheimer diseases were found. Plaque amyloid was exclusively of the beta/A4 type, but abundant abnormal protease-resistant protein was identified by Western blot analysis of brain extracts.

The metabolic landscape of cortico-basal ganglionic degeneration: regional asymmetries studied with positron emission tomography

Regional metabolic rate for glucose (rCMRGlc) was estimated using [18F]fluorodeoxyglucose (FDG) and positron emission tomography (PET) in five patients (four men, one woman; mean age 68; mean disease duration 2.4 years) with clinical findings consistent with the syndrome of cortico-basal ganglionic degeneration (CBGD). Left-right rCMRGlc asymmetry, (L-R)/(L + R) x 100, was calculated for 13 grey matter regions and compared with regional metabolic data from 18 normal volunteers and nine patients with asymmetrical Parkinson's disease (PD). In the CBGD group mean metabolic asymmetry values in the thalamus, inferior parietal lobule and hippocampus were greater than those measured in normal control subjects and patients with asymmetrical PD (p less than 0.02). Parietal lobe asymmetry of 5% or more was evident in all CBGD patients, whereas in PD patients and normal controls, all regional asymmetry measures were less than 5% in absolute value. Measures of frontal, parietal and hemispheric metabolic asymmetry were found to be positively correlated with asymmetries in thalamic rCMRGlc (p less than 0.05). The presence of cortico-thalamic metabolic asymmetry is consistent with the focal neuropathological changes reported in CBGD brains. Our findings suggest that metabolic asymmetries detected with FDG/PET may support a diagnosis of CBGD in life.

In vitro properties of light-polymerized reline materials

One premixed and three powder-liquid light-polymerized, hard denture reline materials were evaluated for Knoop hardness, transverse strength, and tensile strength when bonded to a heat-activated denture resin. The chemical compositions of the components of the reline materials were analyzed. The premixed light-activated liner was harder, had a higher tensile bond strength to the heat-activated denture resin, and was somewhat stronger than the power-liquid reline materials. Properties of the resins were related to their compositions.

Non-neoplastic pineal cysts

We identified 53 patients with non-neoplastic cysts of the pineal gland. In contrast to patients with pineal neoplasms, pineal cysts are usually asymptomatic. They infrequently obstruct the aqueduct to cause hydrocephalus or compress the tectum to produce the neuro-ophthalmologic signs of dorsal midbrain dysfunction. Obstructive hydrocephalus was present in only five patients (9.4%); three of them showed clinical signs of Parinaud's syndrome. CT and MRI typically reveal a cystic mass that averages 1.6 cm in anteroposterior (A-P) diameter with calcification at the periphery and faint rim-like contrast enhancement. Sagittal MRI is the most useful diagnostic test because it shows the anatomic relationship of the cyst to the aqueduct. The mass may compress the tectum and distort the proximal aqueduct; occasionally a large cyst may occlude the aqueduct. All patients with obstructive hydrocephalus had cysts greater than 2.0 cm in A-P diameter. Nine patients had suboccipital craniotomy. In all of them, the cysts contained clear fluid and were easily removed. We advocate conservative management with clinical observation of these benign lesions that may be developmental variants of normal pineal gland.

In vitro bond strength of repaired amalgam with adhesive bonding systems

The in vitro tensile bond strengths of Amalgambond and All-Bond were evaluated as adhesive systems for the repair of amalgam (Valiant Ph.D.) by two repair amalgams (Valiant or Valiant Ph.D.). Other variables evaluated were two surface finishes (SiC finish and sandblasted) and two storage conditions (37 degrees C, 24 h, and thermocycled). The Amalgambond bond was not reliable. All-Bond bonded amalgam to amalgam with Liner-FX. Bond strengths ranged from 3.4 to 8.8 MPa. The highest bond strengths were achieved with a sandblasted surface repaired with Valiant. Thermocycling did not affect bond strength.

In vitro tensile bond strengths of amalgam to treated dentin

Since amalgam traditionally relies on undercuts in the tooth preparation for retention, extensive tooth structure must be removed for amalgam core build-ups. In contrast, the ideal build-up material would achieve its retention by directly bonding to tooth structure. This study compared tensile bond strengths of amalgam to dentin using All-Bond Liner-FX with three different dentin pretreatment conditions and Amalgambond according to the manufacturer's directions. One hundred and twenty dentin samples were tested. Groups 1-3 used All-Bond Liner-FX as a bonding agent. Group 1 received a 15-second application of 10 percent phosphoric acid on the dentin; Group 2 received the recommended dentin conditioner; and Group 3 received no dentin pretreatment. Group 4 used Amalgambond as the bonding agent after a 10-second application of 10 percent citric acid/3 percent ferric chloride. Analysis of the data was conducted using both ANOVA and the Weibull statistic. Results of the analysis of variance indicate that there were no statistical differences among mean tensile bond strengths for the three dentin pretreatment conditions using All-Bond. All (30) of the Amalgambond specimens debonded prior to testing. The All-Bond fracture data was well described by the Weibull function as evidenced by the high coefficient of determination (R2 = 0.98-0.99). Fracture analysis indicated that all of the Amalgambond failures were adhesive at the Amalgambond-amalgam interface. All-Bond fractures were mixed cohesive/adhesive failures indicating similar bonding to amalgam and dentin.

Intracerebral Hodgkin's disease in a human immunodeficiency virus-seropositive patient

Intracerebral involvement of Hodgkin's disease (HD) is rarely described, with only 42 cases in the literature. Since the outbreak of the acquired immune deficiency syndrome (AIDS) epidemic, there has been an increasing number of human immunodeficiency virus (HIV)-infected (HIV+) persons who have diffuse non-Hodgkin's lymphoma and, more recently, atypical aggressive HD. The authors report the case of a patient with a history of intravenous drug abuse (IVDA) and Stage IVB HD who, after a drug-induced clinical remission, had intracerebral mixed-cellularity HD. This appears to be the first report of intracerebral HD in a person who is HIV+.

Spreading of oligomers on polymers

The successful repair of a composite restoration may depend on the ability of a repair composite to spread on the restoration to be repaired. The purpose of this study was to measure the spreading of four oligomers on their polymers. The oligomers were: ethoxylated bisphenol A dimethacrylate (EB), BisGMA/3EDMA:70/30 (ED), BisGMA-Nupol (NU), and urethane dimethacrylate (UD). Polymer strips were made from these oligomers by light-curing. Spreading was calculated from measurements of the contact angle of the oligomers on the polymers, the surface tension of the oligomers, and the viscosity of the oligomers. In this model system, values of spreading of EB, ED, UD, and NU on oligomer ED were: 2.8, 1.4, 0.24, and 0.0009 cm/s, respectively. The spreading by oligomers EB, ED, and UD on polymer ED was slightly higher than that on polymer UD.

Inpatient treatment for depressed children and adolescents: preliminary evaluations

Reported are the results of two uncontrolled outcome studies that evaluate the effectiveness of inpatient psychiatric treatment of children and adolescents suffering from clinical depression. Study 1 employed a sample of 7 children and measured outcome with the Depression Self-rating Scale (DSRS), the Hopelessness Scale for Children (HSC), and the Global Asssessment of Functioning (GAF) scale, which were administered to each child upon admission and again at discharge. Inpatient treatment involved multiple interventions, including individual psychotherapy, medication, milieu therapy and token economy, and other procedures. At discharge, statistically significant improvements were found on the patients' GAF and HSC scores, but not on their DSRS scores. Study 2 used a sample of 15 adolescents, also admitted for clinical depression. Administered at each patient's admission and discharge, the Beck Depression Inventory (BDI), Generalized Contentment Scale (GCS), and Index of Self-esteem (ISE) were used to measure outcome. The multi-modal treatment program offered to the sample in Study 2 was similar to that offered the sample in Study 1. At discharge all three outcome measures reflected statistically significant improvements in the patients studies; therefore, these results provide addmtional support for the inpatient treatment of depressed children and adolescents.