Social comparisons, health and well-being.

Health and well-being are socially determined. One of the ways in which this comes about is via social comparisons with other individuals in the same personal, geographic or social networks, with the comparisons referring either to income or other aspects of economic and social life. The existence of such comparison effects with respect to income may help to explain the social gradient in health.

Factors influencing the survival of implant-supported ceramic-ceramic prostheses: A randomized, controlled clinical trial.

OBJECTIVE: The goals of this research are: (1) to determine the clinical survival of ceramic-ceramic 3-unit implant supported fixed dental prostheses (FDPs) compared with control metal-ceramic and; (2) to analyze the effects of design parameters such as connector height, radius of curvature of gingival embrasure, and occlusal veneer thickness. MATERIALS AND METHODS: This randomized, controlled clinical trial enrolled 96 participants with 129 3-unit implant-supported FDPs. Participants were randomized to receive different design combinations to include FDP material, thickness of occlusal veneer ceramic, radius of curvature of gingival embrasure and connector height. Participants were recalled for 6 months, 1year and yearly thereafter for the next 5 years. FDPs were examined for evidence of fracture and radiographs were made to assess viability of implants. Fractographic analyses and Kaplan Meier survival analysis was used to analyze the data. RESULTS: 27 FDPs, representing 21%, exhibited chipping fractures of the veneer during the 5-year observation period. There was no statistically significant effect of type of material, veneer thickness, radius of curvature of gingival embrasure and connector height on occurrence of fracture. Fractographic and occlusal analyses reveal that fractures originated from the occlusal surface and that occlusion was the most important factor in determining survival. Stresses calculated at failure demonstrated lower values compared with in vitro data. CONCLUSION: Implant-supported ceramic-ceramic prosthesis is a viable alternative to metal-ceramic. Survival analysis for both materials were comparable and design parameters employed in this study did not affect survival as long as zirconia was used as the core material.

Developing and testing an algorithm for automatic segmentation of the fetal face from three-dimensional ultrasound images.

Fetal craniofacial abnormalities are challenging to detect and diagnose on prenatal ultrasound (US). Image segmentation and computer analysis of three-dimensional US volumes of the fetal face may provide an objective measure to quantify fetal facial features and identify abnormalities. We have developed and tested an atlas-based partially automated facial segmentation algorithm; however, the volumes require additional manual segmentation (MS), which is time and labour intensive and may preclude this method from clinical adoption. These manually refined segmentations can then be used as a reference (atlas) by the partially automated segmentation algorithm to improve algorithmic performance with the aim of eliminating the need for manual refinement and developing a fully automated system. This study assesses the inter- and intra-operator variability of MS and tests an optimized version of our automatic segmentation (AS) algorithm. The manual refinements of 15 fetal faces performed by three operators and repeated by one operator were assessed by Dice score, average symmetrical surface distance and volume difference. The performance of the partially automatic algorithm with difference size atlases was evaluated by Dice score and computational time. Assessment of the manual refinements showed low inter- and intra-operator variability demonstrating its suitability for optimizing the AS algorithm. The algorithm showed improved performance following an increase in the atlas size in turn reducing the need for manual refinement.

Novel Testing for Corrosion of Glass-Ceramics for Dental Applications.

The effects of pH cycling immersion on the corrosion of glass-based ceramic materials were investigated by examining the silicon release level in the immersion solution and the surface morphology of the ceramic after immersion. The hypothesis that pH cycling causes more surface degradation than constant immersion was tested. An inductively coupled plasma atomic emission spectrometer was used for Si ion concentration determination and scanning electron microscopy for surface morphology analyses. Two pH cycling sequences (pH 2, 7, 10 and pH 10, 2, 7) were employed in this study. Glass-ceramic disks were immersed in each pH solution for 3 d, then cycled for 27 d. The silicon release levels during the pH cycling were significantly higher than those in the constant pH immersion. The silicon levels for both cycling sequences were around 47 and 2 times higher than that in constant pH conditions for 2 and 10, respectively. The morphology of the ceramic treated with cycling was also significantly degraded as compared with the ceramic immersed in the constant pH solution. Thus, the severity of glass-ceramic degradation depends not only on the pH of the immersed solution but also on the pH of the previous solution. Since the pH of the oral environment can vary depending on the diet and buffering capacity of saliva, materials testing in constant pH immersion might underestimate the in vivo corrosion. New mechanisms were proposed to account for the effect of pH cycling on glass-ceramic corrosion.

A homoleptic chromium(iii) carboxylate.

Structurally characterized chromium(iii) carboxylates form clusters with a variety of bridging groups introduced from aqueous reaction conditions. The first homoleptic monomeric chromium(iii) carboxylate has been prepared using an anhydrous salt metathesis synthetic route. The carboxylate groups coordinate the chromium in a bidentate chelate yielding an aliphatic soluble complex. The complex was characterized by a variety of methods including high energy X-ray diffraction, FD-MS, IR and Raman spectroscopy, complemented by DFT modeling.

Randomized clinical study of wear of enamel antagonists against polished monolithic zirconia crowns.

OBJECTIVES: To test the hypothesis that there is no difference in the in vivo maximum wear of enamel opposing monolithic zirconia crowns, enamel opposing porcelain fused to metal crowns and enamel opposing enamel. METHODS: Thirty patients needing single crowns were randomized to receive either a monolithic zirconia or metal-ceramic crown. Two non-restored opposing teeth in the same quadrants were identified to serve as enamel controls. After cementation, quadrants were scanned for baseline data. Polyvinylsiloxane impressions were obtained and poured in white stone. Patients were recalled at six-months and one-year for re-impression. Stone models were scanned using a tabletop laserscanner to determine maximum wear. Statistical analysis was performed using Mann-Whitney U to determine any significant differences between the wear of enamel against zirconia and metal-ceramic crowns. RESULTS: Sixteen zirconia and 14 metal-ceramic crowns were delivered. There were no statistical differences in mean wear of crown types (p=0.165); enamel antagonists (p=0.235) and enamel controls (p=0.843) after one year. CONCLUSION: Monolithic zirconia exhibited comparable wear of enamel compared with metal-ceramic crowns and control enamel after one year. SIGNIFICANCE: This study is clinically significant because the use of polished monolithic zirconia demonstrated comparable wear of opposing enamel to metal-ceramic and enamel antagonists.

Effect of insulin on GLUT4 cell surface content and turnover rate in human skeletal muscle as measured by the exofacial bis-mannose photolabeling technique.

Insulin-stimulated glucose transport across the skeletal muscle cell membrane is a major regulatory step in postprandial glucose disposal. To estimate the total molar concentration of GLUT4 as well as the turnover rate of GLUT4 in human vastus lateralis muscles at the cell surface in the basal state and after insulin exposure, we have applied the sensitive exofacial bis-mannose photolabeling technique on in vitro incubated human skeletal muscle strips from healthy subjects. In addition, we have measured 3-O-methylglucose transport in other muscle strips prepared from the same surgically removed human skeletal muscle biopsies to compare glucose transport with cell surface level of GLUT4. Maximal in vitro insulin stimulation (2,400 pmol/l) resulted in a twofold increase compared with basal in both surface GLUT4 content (0.38 +/- 0.05 vs. 0.19 +/- 0.03 pmol/g wet muscle wt, P < 0.005) and 3-O-methylglucose transport (1.24 +/- 0.13 vs. 0.63 +/- 0.08 pmol x ml(-1) x h(-1), P < 0.005). The insulin-induced increment in 3-O-methylglucose transport was strongly correlated with the insulin-induced increase in cell surface GLUT4 content (r2 = 0.91; P < 0.005). The calculated turnover rate of human skeletal muscle GLUT4 amounted to approximately 8 x 10(4) min(-1) at 35 degrees C and was unaffected by insulin. In conclusion, maximal in vitro insulin stimulation of vastus lateralis muscle strips from healthy subjects resulted in a twofold rise in glucose transport as well as in cell surface content, whereas the turnover rate of GLUT4 was unaffected by insulin under the chosen experimental conditions.

A study of enzymes involved in catecholamine metabolism in parents of patients with schizophrenia.

The concentrations of serum homovanillic acid (HVA), norepinephrine (NE), tyrosine (Tyr), phenylalanine (Phe) and tryptophan (Trp), and the activities of serum dopamine-beta-hydroxylase (DBH), platelet monoamine oxidase (MAO), and erythrocyte catechol-O-methyl transferase (COMT) were measured in 68 healthy parents who had schizophrenic offspring. The results show a significant correlation between the parents of schizophrenic patients in serum HVA (r=0.38, n=34, p<0.05), NE (r=0.40, n=33, p<0.02), Phe (r=0.44, n=34, p<0.0l), Tyr (r=0.43, n = 34, p <0.02) and DBH activity (r=0.51, n = 30, p <0.005), but do not show a significant correlation in erythrocyte COMT (r=0.01, n=27), platelet MAO (r=0.04, n=23) or serum Trp (r=0.10, n=34). There were no significant correlations in these measurements between randomly matched parents. The present study suggests that both parental sides of schizophrenic patients are likely to have similar alleles associated with the catecholamine pathway, and their ill offspring may possess a double dose of the schizophrenogenic alleles.

Elastofibroma dorsi.

Two cases of elastofibroma dorsi are reported and the light and electron microscopic features analysed. The appearances suggest that the characteristic fibres and globules that stain as for elastin arise by denaturation of collagen. The fibres differ from the elastin of arterial wall, elastotic degeneration of skin, and pseudoxanthoma elasticum. The morphology and clinical behaviour indicate that elastofibroma dorsi is a reactive fibromatosis rather than a true neoplasm.

Decreased tyrosine transport in fibroblasts from schizophrenics: implications for membrane pathology.

Two independent studies reported recently have shown a significant decrease in Vmax of tyrosine transport in fibroblasts grown from schizophrenics' skin compared with controls. It has also been shown that tyrosine transport into the brain is decreased in schizophrenics compared with controls. In view of the importance of these findings in elucidating the biochemical mechanism(s) associated with schizophrenia, we have studied the kinetics of tyrosine transport and the levels of monoamine oxidase (MAO) activity in fibroblasts grown from the skins of schizophrenics and unrelated control subjects. Using the Lineweaver-Burk plot, the Eadie Hostee plot and the Hanes plot we have calculated the Km and Vmax for tyrosine transport. We have found a significant decrease in the Km and Vmax values for tyrosine transport in schizophrenics compared with control fibroblast samples. No changes were observed in the levels of MAO. Using Lineweaver-Burk plot (1/S Versus 1/V) it has been shown that the tyrosine transport inhibition is uncompetitive. This finding proposes that the inhibition is in the substrate transport protein complex, which may be taking place during the transit of the substrate through the cell membrane. From the observed findings and from the literature evidence we suggest that the altered metabolism of phospholipids in schizophrenics, such as deficiency of arachidonic acid and docosahexaenoic acid, may be contributing to this observed phenomena.

Glucose oxidation and monoamine oxidase activity from the fibroblasts of schizophrenic patients and controls.

Fibroblasts have emerged as one of the best systems in which to study several genetically inherited diseases. Their use avoids the contaminating effects of medication and other environmental factors. Moreover, fibroblast cells cultured in vitro can express several biochemical parameters which are characteristic of neuronal cells. We have studied fibroblast MAO-A and glucose oxidation and platelet MAO-B from schizophrenic patients and control subjects. Fibroblasts from schizophrenics showed an increased glucose oxidation in two different experiments conducted (122% and 126% compared to controls). No changes were found in the levels of fibroblast MAO-A or platelet MAO-B activity. Possibly these alterations in glucose oxidation may be associated with a generalized membrane abnormality which has been reported in schizophrenia.

Treatment of herpes labialis.

Untreated herpes labialis may take up to 10 days or more to heal and antiviral therapy must be initiated early if it is to be effective. Acyclovir ointment has been reported to have an antiviral effect but no clinical benefit and a newer formulation, acyclovir cream, has been developed in an attempt to enhance skin penetration. In placebo-controlled trials, acyclovir cream shortened the duration of lesions significantly and when therapy was started before vesicles developed, the number of lesions aborting was increased significantly. This therapy was well tolerated by most patients. Topical acyclovir offers hope for the successful management of herpes labialis where systemic therapy is considered inappropriate.

Quantitative assessment of dentin bridge formation following pulp-capping in miniature swine.

A quantitative assessment of dentin bridges was conducted on sections prepared from teeth capped with four pulp-capping agents (Bioglass, Life, Demineralized Dentin Matrix, and Teflon) in a micro-swine model. The degree of mineralization of the dentin bridges relative to the adjacent primary dentin was measured using a computer-based image analysis of microradiographs prepared from the sections. The rate of formation of the dentin bridge was measured from fluorescent bands formed in the same sections by a Demeclocycline dentin marker. There were no statistically significant differences in the relative mineral densities of the dentin bridges and the rate of dentin bridge formation under the four pulp-capping agents. These findings support the suggestion that components of the extracellular matrix rather than pulp-capping agents may be important in the formation and mineralization of dentin bridges in repairing dental pulps.

Using 45S5 bioglass cones as endosseous ridge maintenance implants to prevent alveolar ridge resorption: a 5-year evaluation.

Bioglass cones acting as space fillers after removal of tooth roots delay the resorption of alveolar ridges. In 1987, 242 implants in 29 patients with a mean postimplantation interval of 19.9 months were reported by the authors. Bioglass cones had been fitted snugly at least 2 mm below the alveolar crest, and dentures were placed no sooner than 6 weeks following tooth removal; 2.9% had been lost and 3.7% developed dehiscences. The present report on 168 implants in 20 recalled patients (mean postimplantation interval of 63.2 months) revealed a loss of 14.3% of the implants and 7.7% of the implants requiring recontouring. Literature indicates highest survival rates for implants in the anterior mandible; however, the present data demonstrate a statistically significant retention rate in the anterior maxilla. With this high rate of Bioglass cone retention (85.7%) after 5 years, their placement into fresh sockets to maintain the alveolar ridge is recommended.

Cultured human keratinocytes as a model for studying the dopamine metabolism in schizophrenia.

The dopamine hypothesis is the major etiological hypothesis of schizophrenia which proposes that enhanced central nervous system dopaminergic activity is the causative factor for this disease. The hypothesis remains unproven despite decades of research. The major difficulty in studying the disease is due to the unavailability of a suitable animal model. Studies with human blood, cerebrospinal fluid or post-mortem brains lead only to inconclusive results, due to the effects of medication and other environmental factors. No extra-neuronal cells, with the exception of adrenal medulla, have been reported to contain a dopamine metabolic pathway. Literature evidence and our own study suggest that human keratinocytes express the enzymes to synthesize and degrade dopamine. We have compared the properties of tyrosine hydroxylase, the rate-limiting enzyme, from mouse striatum and from human skin keratinocytes cultured in vitro. Moreover we could also detect dopamine beta hydroxylase and catechol-o-methyl transferase in keratinocytes. We propose that human keratinocytes cultured in vitro can be used to study the relevance of dopamine metabolism to schizophrenia under controlled conditions avoiding the effects of medication and other environmental factors.

Pulp capping with a modified bioglass formula (#A68-modified).

PURPOSE: To evaluate a modified Bioglass (Formula #68 (MBF68) when used as a pulp capping agent. MATERIALS AND METHODS: After exposure, the pulps were contaminated with saliva for 60s, rinsed, dried and treated with Consepsis, acting as a hemostatic and bactericidal agent. After drying the Consepsis, the MFB68, having been pre-mixed in sterile saline, was carefully deposited over the pulp exposure, covered with polycarboxylate cement and restored with the ProBond bonding resin system. A calcium hydroxide group was used as control. RESULTS: There was no evidence of mummification, the incidence of properly positioned dentin bridge formation was higher and the incidence of extruded dentin bridge formation was reduced.

Tissue response to Bioglass endosseous ridge maintenance implants.

Conical devices placed in the alveolar ridge after tooth extraction have been used clinically for several years to maintain the ridge morphology. In this way, the bone atrophy which occurs after extractions is minimized, and denture fit and function are enhanced. A system using such cones made from Bioglass (registered trademark of the University of Florida) and matching burs has been developed and tested clinically. Average four-year data show a retention rate of over 90%, which compares favorably with other systems using other materials (see Hench et al., 1991). Stanley et al. (to be published), in a review of the four-year clinical data, point out that a few of the cones, although firmly positioned within the alveolar ridge, have a radiolucent zone around the implant. In a clinical study, it is not possible to determine whether this radiolucent zone represents areas of fibrous capsule which are not attached to the implant and therefore compromise its long-term stability, or whether the soft tissue is adherent to the implant and thus contributes to its long-term stability. In a recent study, conical implants identical to those in the clinical trial were placed in the alveolar ridges of dogs and evaluated for up to two years. The adhesion of bone and soft tissue was measured and the development and stabilization of the reactive gel layer monitored. The findings in this animal study support the clinical observations and contribute to an explanation of the success of the Bioglass system in patients.

Clinical use of a bioactive glass particulate in the treatment of human osseous defects.

The dental practitioner has a wide choice of materials available for use in bone grafting procedures. A bioactive glass particulate possesses many favorable qualities not often found in other materials, including the ability to remain where placed even with adjacent suctioning; hemostasis; and incorporation into the host bone without the fibrous encapsulation encountered with most other synthetic materials. It is also quick and easy to prepare. This article reviews clinical experiences with PerioGlas in the setting of private practice periodontics, in which this material was used as the grafting material for periodontal defects, apicoectomies, cysts, and ridge augmentation and maintenance procedures, as well as for implant repairs. Several cases detail the advantages of this grafting material.

Surface degradation of dental ceramics as a function of environmental pH.

We tested the hypotheses that glass-ceramic veneers and overglazes degrade by ion exchange in an acidic environment, and that they degrade by breakdown of the silica network in a basic environment. Disk specimens of glass-ceramic veneer and glaze were fabricated and immersed in pH 2, 7, or 10 buffer solutions, for 1, 3, 5, 10, 15, and 30 days. Each specimen was placed in a shaker bath containing de-ionized distilled water at 80°C. Concentrations of Al(3+), Ca(2+), Zn(2+), Li(2+), and Si(4+) were analyzed by means of inductively coupled plasma atomic emission spectrometry (ICP/AES). Statistical analyses were performed by factorial ANOVA. Significant differences occurred among leached ion concentrations as a function of material type, solution pH, and exposure time. A substantial release of Si occurred at pH 10 over time, leading to a breakdown of the glass phase. At pH 2, dissolution was controlled by an ionic exchange mechanism. We conclude that ceramic veneers and glazes may be susceptible to considerable degradation in low- and high-pH buffer solutions.