Adhesion of composite resin to bleached and unbleached bovine enamel

Cylinders of microfil and small-particle light-cured composite resin were bonded to the flattened labial enamel surface of young bovine incisor teeth which had previously been subjected to four different treatments: (1) teeth immersed in 35% hydrogen peroxide (HP) for 60 min and etched (E) with 37% phosphoric acid gel for 60 sec; (2) teeth immersed in saline (S) for 60 min and E for 60 sec; (3) teeth E for 60 sec and immersed in HP for 60 min; and (4) teeth E for 60 sec, immersed in S for 60 min. Specimens were stored in water at 37 degrees for one and seven days prior to tension- and shear-testing. A total of 256 teeth was tested--eight teeth in each group for each day, for each resin, and for each test. Statistical analysis of the results indicated that there was a highly significant reduction in adhesive bond strength of the resins when the enamel was exposed to HP as compared with S. SEM examination of randomly selected fractured test specimens indicated that this reduction in adhesive bond strength occurred primarily at the bonding resin-enamel interface. Less significant differences in bond strength were noted in the control specimens, with regard to resin type, time of storage, and the etching order.

A technique for estimating the probability of clots in blood/contrast agent mixtures

Blood that contaminates the contrast agent syringe during angiography may clot and is thus a potential source of emboli. The older, high-osmolality agents prevent clotting. Newer, low-osmolality agents, while possessing other advantages, are less effective in this regard. The time over which such mixtures do not contain clot can be determined by allowing gross clotting to take place, modeling the process mathematically and determining the clot-free time from the model. Blood-contaminated Omnipaque-300 (Winthrop-Breon, New York, NY) (iohexol), Isovue-300 (E.R. Squibb and Sons, New Brunswick, NJ) (iopamidol), Hexabrix (Mallinckrodt, St. Louis, MO) (ioxaglate sodium meglumine), Renografin-76 (E.R. Squibb and Sons, New Brunswick, NJ) (diatrizoate sodium meglumine), and saline were studied in glass and plastic syringes (80 samples of each agent). After deliberate blood contamination, Renografin and Hexabrix showed no clots during the 90-minute study period. There was, however, a 1.3% chance of clotting in Omnipaque (range 0.4%-4.0%) and a 1.9% chance of clotting in Isovue (range 0.6%-5.5%) at 5 minutes after contamination of these contrast agents in plastic syringes. The chance of clotting in glass containers was significantly greater. We conclude that Hexabrix is a substantially stronger anticoagulant than Omnipaque and Isovue. Furthermore, it appears that this method will allow determination of clotting risks for other combinations of contrast agent and container.

Future directions for research on materials and design of dental implants

Previous reviews underscore the uncertainties in our knowledge of the influence of material characteristics, design-shape, and surface texture on the implant material-tissue interface. Current implant designs are based on intuitive approaches and there are no general principles for prediction of success of implant systems. Data on implant surfaces prepared by customary preparative techniques show that they are highly variable and dependent on processing. The long-term (years) effects of trace element release from implants is little understood because of past errors in analytical techniques and paucity of relevant data. To place the development of future implant systems on a more rational basis, scientific studies are needed (1) to identify and characterize new and modified materials and surfaces, (2) to validate surface characterization procedures and evaluate tissue responses to standardized surfaces, and (3) to measure trace and subtrace element levels in animal and human tissues over time in order to establish normal and pathologic limits.

Early postoperative hypoxia during transport

The incidence of immediate postoperative hypoxaemia following general anaesthesia was studied using a pulse oximeter in 120 ASA category I and II patients during transport to the recovery room. Thirty-two percent of those not given oxygen during transport developed desaturation (SaO2 less than 90%) in spite of receiving 100% oxygen for 5 min before transport. In 14.3% of patients SaO2 decreased to less than 85%. None of the patients given oxygen 2 litre min-1 via a nasopharyngeal catheter during transport exhibited an SaO2 less than 90%. The only variable which correlated with the development of desaturation was the duration of anaesthesia.

Cancer support groups--who joins and why?

Tak Tent is a cancer support organisation consisting of 14 groups of which 11 are based in Scotland. In 1985, a survey was conducted among those attending the Scottish groups. 146 (79%) of the groups' members completed survey questionnaires. The results showed that Tak Tent's membership mainly comprised cancer patients (36%), relatives of patients (34%) and professionals involved in cancer care (21%). Women outnumbered men 3 to 1 and most of the membership belonged to social classes I, II or III. The groups appeared to be meeting their members' expectations of them to varying degrees. Respondents were satisfied that group membership had allowed them to make new friends, find out more about cancer and meet others facing similar difficulties. They were less certain that participation in a group had enabled them to learn how to cope better with cancer, share their problems with others or provide support for others to the extent they had anticipated.

Ultrastructural morphometric data of human spermatozoa

A morphometric study of the volumetric parameters of human spermatozoa has been carried out, volume densities being obtained by point counting and converted to absolute volumes by employing the point-sampled intercept method. Data for the Spermatozoa from the semen of 15 recently fertile men are presented. The significance of the results is discussed in relation to results obtained by other methods and in relation to the building of a diagnostic reference database.

Dental cements

The manifold uses of dental cements-as (a) luting agents, (b) cavity linings and bases, and (c) restorations for teeth—make them perhaps the most important materials in clinical dentistry. The research of the last 10 years has resulted in four main types, classified by matrix-forming species: (1) phosphate, (2) phenolate, (3) polycarboxylate, and (4) polymethacrylate. The zinc phosphate cements continue to be widely used for luting in an essentially unchanged form. Acidity and oral dissolution remain as problems. The zinc-oxide eugenol cements and their modifications are useful as linings and temporary materials but are susceptible to hydrolytic breakdown. Vanillate cements may be an improvement. Calcium hydroxide-salicylate cements are widely used as cavity linings, especially on exposures, and show improved resistance to acid dissolution. Polycarboxylate cements as both zinc polycarboxylate and glass-ionomer cements show adhesion potential, good physical properties, fluoride release, and, generally, good biological properties. Glass-ionomer cements when correctly manipulated show minimal oral dissolution. Polymethacrylate cements have been used principally for bonding etched cast metal restorations to etched enamel. Recently, adhesive crown-and-bridge cements have been developed. There are no well-established correlations between laboratory measurements of apparently relevant properties and clinical performance. More clinically-based research is needed to facilitate the development of new cements.

Thiol exchange catalysed refolding of small proteins utilizing solid-phase supports

The study of isolated snake toxin refolding has been a valuable tool in the understanding of protein folding dynamics. We report here differences in the refolding characteristics of three toxin classes and introduce a novel method for overcoming disulphide mismatching and oligomer formation by utilizing solid-phase thiol exchange gels.

Anger, perceived control and school behavior among students with learning problems

With regard to students with learning problems, findings indicate that the more severe the learning problem, the greater the tendency toward anger in response to conflicts at school. The relationship between learning problem severity and perceptions of control at school was not significant, but anger was negatively correlated to perceived control. None of the variables were significantly related to misbehavior. A stepwise regression analysis indicated perceived control as the most potent single variable accounting for the variance in anger scores. Overall, findings highlight implications for work focused on reactions to learning problems and factors associated with their cause and correction.

Microgeographic genetic variation in the apple maggot rhagoletis pomonella

We examined electrophoretic variability at five enzyme loci in the apple maggot fly, Rhagoletis pomonella, on a microgeographic scale. Treating flies from individual hawthorn trees as separate populations, we estimated F(ST) values from allele frequencies. The results indicate that there is significant allele frequency heterogeneity among fly populations over a small spatial scale at some loci but not at others. This variation among loci in degree of differentiation is itself statistically significant, casting doubt on the role of genetic drift in maintaining the heterogeneity. There is also heterogeneity between years in flies from a given tree. These data provide a baseline with which future work on genetic differentiation among apple maggot populations associated with different species of host plants may be compared.

Evaluation of shear strength at the cement-endodontic post interface

The strength characteristics of the cement-implant interface were evaluated for smooth-tapered, threaded, and porous-surfaced endodontic implants with the use of different cements. Specifically, tensile and torsional shear strengths were measured for zinc phosphate, polycarboxylate, glass-ionomer, silicophosphate, and AH-26 cements. The results indicated superior shear strength characteristics for threaded endodontic implants on axial loading. However, this strength was diminished when torsional forces were applied. Porous-surfaced endodontic implants showed strong resistance to both axial and torsional loading.

Hinged shutter for image alternator

A hinged, mobile shutter was designed to reduce the effect of extraneous light on the interpretion of chest radiographs and angiograms. The authors believe that the device greatly facilitates the daily work by decreasing eye fatigue and probably by increasing the signal-to-noise ratio.

A comparison between zinc phosphate and glass ionomer cement in orthodontics

In the past orthodontic band cementation has relied heavily on mechanically retentive cements such as zinc phosphate luting agents. The clinical performance of a glass ionomer cement (GIC), a chemically retentive cement, was evaluated against a conventional zinc phosphate cement (ZP). The recementation values for ZP were significantly higher over a 2-year treatment period than those of GIC. Failures between cement and enamel, and cement and stainless steel were noted for the ZP. Glass ionomer cement had significantly better retentive strength to enamel than to band material. Moisture contamination does not appear to be a problem in orthodontic band cementation with glass ionomer cement.

Evaluation of the retention of endodontic implants

The study investigated the retentive strength of endodontic implants measured by forced removal (pull-out or push-out tests) as a function of implant design and cement type. Smooth-tapered, threaded, and an innovative porous-surfaced implant were evaluated. Specimens were cemented in single-rooted human teeth with five different cements: zinc phosphate, polycarboxylate, glass ionomer, silicophosphate, or AH-26. The results indicated superior retention for the threaded and porous-surfaced implants, and stronger retention with glass-ionomer and AH-26 cements.

The glove rattling induction maneuver (GRIM): a valuable angiographic technique

A technique in which the attending radiologist can facilitate various angiographic maneuvers by the learning radiology resident is described. It is simple, quick, and inexpensive; its usefulness was demonstrated in a prospective study.

Psychosocial consequences of mastectomy: levels of morbidity and associated factors

Psychosocial morbidity was examined in 90 consecutive patients with Stage I or II breast cancer aged under 70 treated by mastectomy. In the two years after surgery, the prevalences of depression and anxiety of clinical degree were generally under 10%--less than half of those reported in early controlled studies in the United Kingdom. However, cancer patients aged under 50 showed significantly higher prevalences compared with cancer patients aged 50 or above and compared with matched control subjects with benign breast disease. Social and work problems were common at all ages. Sexual problems were more severe than mood disturbance. Patients at risk of mood disturbance could be predicted by a combination of age, measures of emotional lability and whether or not they were receiving chemotherapy. The results of this study are consistent with those of other recent reports from the United Kingdom and United States, which show that following mastectomy, mood disturbance of clinical degree may be considerably less common than has previously been supposed.

Validity of the General Health Questionnaire and its subscales in patients receiving chemotherapy for early breast cancer

The performance of the General Health Questionnaire as a case detector was assessed in 75 patients receiving chemotherapy for early breast cancer. The questionnaire and its subscales were found to be valid when compared with observer ratings. The misclassification rate of the 60-item version of the questionnaire was lowest when the standard threshold score for clinical morbidity was doubled to 24. It was lowest for the 28-item version when the threshold score was doubled to 10. Suggested threshold scores for clinical morbidity for the subscales are: anxiety and insomnia subscale 6/7; severe depression subscale 2/3; somatic symptoms subscale 6/7; and social dysfunction subscale 7/8. However, lower thresholds would be appropriate if the questionnaire were used as screening instrument prior to interview by a trained observer.

Three new low-osmolality contrast agents: a comparative study of patient discomfort

Relative patient discomfort resulting from carotid injections of three new low-osmolality contrast agents was assessed in 78 patients. Omnipaque-300 (iohexol), Isovue-300 (iopamidol), and hexabrix (ioxaglate) were sequentially injected into both common carotid arteries of each patient. Patients were asked to rank the relative intensities of the three injections on each side. Mean patient rankings revealed that Hexabrix was preferred most often, Omnipaque-300 next, and Isovue-300 the least. The differences are statistically significant. We conclude that while patients usually tolerated all intracarotid low-osmolality contrast agents rather well, the agent preferred most often was Hexabrix.

Psychosocial morbidity in patients awaiting breast biopsy

Psychosocial morbidity was compared in 91 patients awaiting breast biopsy and 30 women awaiting elective cholecystectomy. Somatic symptoms and social dysfunction were prominent in cholecystectomy patients. Patients subsequently found to have benign breast disease had the highest levels of psychological morbidity. Patients found to have breast cancer appeared no more anxious or depressed than those awaiting cholecystectomy. However, within the breast cancer group, patients aged 45 or less were significantly more anxious than those over 45, and a past history of psychological upset, prior to discovery of breast disease, was positively and independently associated with anxiety. Results are consistent with recent research suggesting an association between benign breast disease and a predisposition to psychological morbidity.