Shear bond strength of Bis-GMA resin and methacrylated dendrimer resins on silanized titanium substrate.

OBJECTIVES: The study compared the bond strengths of three resins, Bis-GMA and two novel experimental methacrylated polyester dendrimer resins to grit-blasted titanium substrate with three silanes. METHODS: Two commercial dental silanes (ESPE Sil and Monobond-S) and an experimental 0.5 vol% 3-methacryloxypropyltrimethoxysilane were applied to grit-blasted Ti substrates. Light-polymerizable resins of Bis-GMA and methacrylated dendrimer were applied to the grit-blasted Ti substrate with polyethylene molds. The substrates with resin stubs (n = 10) were thermocycled (6000 cycles, 5-55 degrees C) or kept in water (37 degrees C, 24 h). The shear bond strength of the resin was measured at a crosshead speed of 1.0 mm min(-1). The surface examination, before and after silanization, was made with a scanning electron microscope (SEM). The silane reactions on the Ti surface were monitored by Fourier transform infrared spectrometry. RESULTS: Statistical analysis (ANOVA) showed that the highest shear bond for thermocycled samples was obtained for Bis-GMA with Monobond-S (19.4 MPa, standard deviation (SD) 7.1 MPa), and after water storage with a laboratory-made silane (26.4 MPa, SD 8.1 MPa). The dendrimer and Bis-GMA resins conferred equal bonding properties to grit-blasted titanium after thermocycling. The silane, resin type, and storage conditions significantly affected the shear bond strength (p < 0.001 for all factors). SEM images suggested a mainly cohesive type of bonding failure. SIGNIFICANCE: A dendrimer based resin and the Bis-GMA resin systems conferred statistically equivalent bonding properties to silica-coated Ti after thermocycling.     

Femoral neck structure in adult female athletes subjected to different loading modalities.

Loading modality is a strong external determinant of structure and concomitant strength of the femoral neck. Particularly effective seem to be loadings, which arise from high impacts or impacts from atypical loading directions. INTRODUCTION: Physical loading plays an important role, not only in the process of bone modeling and remodeling, but also in shaping a mechanically appropriate bone structure. This study aimed at testing the hypothesis that the type of loading partly determines the femoral neck structure. MATERIALS AND METHODS: A total of 255 premenopausal female athletes representing volleyball, hurdling, squash-playing, soccer, speed skating, step aerobics, weight-lifting, orienteering, cross-country skiing, cycling, and swimming and their 30 nonathletic counterparts were measured with DXA. Besides the conventional areal BMD (aBMD) of the femoral neck, the hip structure analysis (HSA) was used to estimate the cross-sectional area (CSA), subperiosteal width (W), and section modulus (Z, an index of bone strength) at the narrowest section of the femoral neck. Also, training history, muscle strength, and calcium intake were assessed. The above-mentioned sports were classified according to the type of loading they apparently produce at the hip region; that is, high-impact loading (volleyball, hurdling), odd-impact loading (squash-playing, soccer, speed-skating, step aerobics), high-magnitude loading (weightlifting), low-impact loading (orienteering, cross-country skiing), and nonimpact loading (swimming, cycling). RESULTS: High-impact and odd-impact loading sports were associated with the highest age-, weight-, and height-adjusted aBMD (23% and 29% higher values compared to nonathletic referents), CSA (22% and 27%), and Z (22% and 26%). In contrast, repetitive, nonimpact loading sports were not associated with any clear benefit in any bone value compared with the referents. The W at the narrowest femoral neck section was similar in all groups. Body height and weight accounted virtually for one-half of the variation in Z, whereas the type of loading predicted 13% of the total variation of this variable-clearly more than the 2% attributable to isometric leg extension strength. Both high-impact and odd-impact loading modalities were associated with a large benefit in Z, corresponding to >1 SD in the reference group, whereas repetitive, low-impact loading showed a benefit that was only one-half of that. Surprisingly, high-magnitude loading (weightlifting) was not associated with a statistically significant increase in Z. CONCLUSION: We conclude that mechanical loading and its modality are strong external determinants of structure and concomitant strength of the femoral neck. Particularly effective seem to be loadings, which arise from high impacts or impacts from atypical loading directions.     

Relation of exploratory behavior of rats in elevated plus-maze to brain receptor binding properties and serum growth hormone levels

Forty-five male Wistar rats were selected according to their behavior in the elevated plus-maze. They were separated as follows: animals with low exploratory activity (‘anxious'), an ‘intermediate' group and animals having high exploratory activity (‘non-anxious'). Various receptor binding studies and hormonal assays were also performed in these selected rats. The affinity of 5-hydroxytryptamine 5-HT_2A receptors in the frontal cortex was lower in the ‘anxious' rats compared to home-cage controls and ‘non-anxious' animals. Moreover, the number of cholecystokinin (CCK) receptors in the hippocampus was significantly elevated in the ‘anxious' group compared to home-cage control animals. The blood levels of growth hormone (GH) were significantly lower in the ‘non-anxious' rats compared to ‘anxious' counterparts. In conclusion, it seems likely that the decreased exploratory activity of rats is related to the increased 5-hydroxytryptamine (5-HT) and CCK mediated neurotransmission in the brain. The different serum levels of GH in the selected rats probably reflect alterations in the activity of 5-HT and CCK.     

Occlusal restorative decisions based on visual inspection –calibration and comparison of different methods

Abstract The purpose of this in vitro study was to calibrate occlusal restorative decision-making based on visual inspection (VI), and to compare it with visual inspection with magnifying (×1.25) lenses (VIM), and fibre-optic transillumination (VIF). Sixty extracted human third molars mounted in plaster were examined using VI by ten dentists three times during the calibration process. After wash-out periods, the teeth were re-examined by the same dentists using VI, VIM and VIF. The inter-examiner reproducibility for VI, expressed as Kappa (κ) statistics (K±SD), was 0.46±0.10 before and 0.59±0.1 1 after the calibration process and remained at the same level after the wash-out period. Intra-examiner reproducibility was substantially higher for VI (κ=0.68±0.15) before and after the wash-out period. There were no significant changes in restorative treatment decisions based on VIM and VIF when compared to VI. The reproducibility between the methods was good for VI vs. VIM (κ= 0.64) and moderate for VI vs. VIF (κ= 0.56). In contrast, the inter-examiner reproducibilities expressed as Kappa were considerably lower for VIM (κ= 0.46±i0.17) and VIF (κ=0.42±0.19). It was concluded that the inter-examiner reproducibility can be improved with a calibration process based on a simple feedback method and that inter-examiner variation, especially without calibration, may be as important a factor for restorative treatment decisions as the diagnostic method itself.     

Acrylic resin-fiber composite—part I: The effect of fiber concentration on fracture resistance

This study tested the effect on the fracture resistance of acrylic resin test specimens when different amounts of fibers were incorporated in the resin matrix. The fibers used included glass, carbon, and aramid fibers, with 30 test specimens of each concentration of fibers. Transverse sections of the specimens were studied by scanning electron microscope to establish how the fibers behave in the polymerization process. The results indicated that an increase in the amount of fibers enhanced the fracture resistance of the test specimens (p < 0.001). The SEM micrographs of transverse sections of test polymerized specimens revealed void spaces of different sizes inside the fiber roving.     

Ways of coping with asthma in everyday life: Validation of the Asthma Specific Coping Scale

Objective: This study examines the validity of the Asthma Specific Coping Scale. Methods: Study samples were comprised of persons with drug-treated asthma (n=3464) drawn from the Drug Reimbursement Registry and asthma rehabilitation participants [brief (n=278) and comprehensive (n=316) intervention]. Data were collected by questionnaires. Results: The expected structure of the six subscales (restricted lifestyle, hiding asthma, positive reappraisal, information seeking, ignoring asthma, and asthma worry) was supported. The Cronbach's reliabilities of the subscales ranged from .63 to .84. Concurrent validity was supported by meaningful correlations between asthma coping scales and psychosocial resources, health-related quality of life, and general coping. The asthma coping scales discriminated between the intervention participants and the population-based sample. Four out of six subscales also showed sensitivity to change after rehabilitation. Conclusion: Though further longitudinal studies are needed, this scale seems to be a promising instrument to be used in surveys and outcome studies.     

Rapid endocrine effects of tamoxifen and testolactone in prostatic carcinoma patients

The short-term (6-day) endocrine effects of tamoxifen and testolactone were investigated in men with prostatic carcinoma. Tamoxifen treatment (20 mg/day) did not affect the gonado-tropin levels, but it temporarily increased prolactin, induced sex hormone-binding globulin production, and suppressed peripheral serum progesterone, 17-hydroxyprogesterone, an-drostenedione, testosterone, and 5α-dihydrotestosterone concentrations. These changes were attributed to the estrogenic properties of tamoxifen, since no changes in peripheral serum estradiol concentrations were observed. Testolactone (1000 mg/day) decreased peripheral estradiol concentrations by 50% and increased the concentrations of the neutral steroids measured. The increases in serum FSH and LH were very small. This study corroborates the early estrogen-like action of tamoxifen, and the experiment with testolactone further suggests that endogenous estradiol has physiological functions in man, regulating gonadotropin and androgen production.     

Compressive strength and surface characterization of glass ionomer cements modified by particles of bioactive glass.

OBJECTIVES: The aim of this study was to determine compressive strength, Young's modulus of elasticity, and Vickers' surface hardness, of conventional cure and resin-modified glass ionomer cements after the addition of bioactive glass (BAG) particles into the cements. METHODS: Experimental glass ionomer cement (GIC)-BAG materials were made by mixing 10- or 30-wt% of BAG particles with conventional cure and resin-modified GIC powders. Materials were processed into cylindrical specimens and immersed in water for 1, 3, 7, 14, 30 and 180 days before mechanical tests. SEM and EDS analysis was used to characterize the changes in surface topography and the main elemental composition. RESULTS: The compressive strength of the test specimens decreased with the increasing amount of BAG. The compressive strength of resin-modified GIC increased during the immersion, but remained at a lower level than that of the other materials. The conventional cure GIC-based materials had on average 55% higher surface microhardness than the resin-modified materials. In the elemental composition, more Ca was detected in the BAG-containing materials than in the pure GICs. The amount of F was significantly higher (p < 0.001) on all resin-modified materials, being highest on resin-modified GIC with 30-wt% of BAG after 180d of immersion. SIGNIFICANCE: The addition of BAG to GIC compromises the mechanical properties of the materials to some extent. Thus, their clinical use ought to be restricted to applications where their bioactivity can be beneficial, such as root surface fillings and liners in dentistry, and where high compressive strength is not necessarily needed.