Protecting children from taking up smoking: parents' views on what would help.

ISSUE ADDRESSED: The present study investigated what factors the parents of children in low-income areas of Auckland, New Zealand, thought could help protect their children from smoking initiation. METHODS: Participants in a large quasi-experimental trial that tested a community-, school- and family-based smoking-initiation intervention were asked in a questionnaire 'What could we do to help you protect your children from smoke and taking up smoking?' Free-text responses were divided into distinct meaning units and categorised independently by two of the researchers. RESULTS: 1806 participants (70% of parents who returned the questionnaire) completed the question. The majority of respondents (80%) were either Pacific Island or Maori mothers and 25% were current smokers. Five main categories of suggested strategies for preventing smoking initiation were identified: building children's knowledge of the ill-effects of smoking; denormalising smoking; reducing access to tobacco; building children's resilience; and health promotion activities. The most common suggestion was to educate children about smoking. CONCLUSION: Building children's knowledge of smoking risks was the main strategy parents proposed. There was some support for banning smoking in most public areas and for tougher moves to stop tobacco sales to minors. Few parents suggested innovative or radical strategies, such as banning the sale of tobacco, fining children for smoking or use of competitions. So what? To ensure reductions in smoking initiation for lower socioeconomic and Maori and Pacific Island people, further research should engage Maori, Pacific Island and lower socioeconomic parents in a process that elicits innovative thinking about culturally acceptable strategies.

Taking a risk perception approach to improving beach swimming safety.

BACKGROUND: Beach swimming is generally associated with a healthy lifestyle, yet the risk of drowning is universally significant. PURPOSE: The purpose of the study was to investigate the factors associated with safe swimming behavior using protection motivation theory as a guiding theoretical framework. METHOD: This cross-sectional study surveyed a sample of beachgoers (N = 3371) aged > or =16 years who completed an anonymous, self-report questionnaire to assess the associations between perceptions of the risk of drowning and safe swimming behavior. RESULTS: Compared with males, females perceived greater severity, vulnerability, response efficacy, and concern regarding their risk of drowning. Males, Maori, and 16 to 29 year olds reported higher self-efficacy scores compared to females, other ethnic groups, and older participants, respectively. After controlling for confounding variables, people perceiving a greater threat (severity) of experiencing difficulty while swimming as well as those reporting higher response efficacy (beliefs about the effectiveness of drowning prevention measures) were more likely to report safe swimming behavior. CONCLUSION: The effectiveness of water safety education programs could be strengthened by enhancing risk appraisal and coping skills and counter-acting the tendency of males and younger adults to overestimate their swimming ability and underestimate their risk with regard to drowning.

BMP-silk composite matrices heal critically sized femoral defects.

Clinical drawbacks of bone grafting prompt the search for alternative bone augmentation technologies such as use of growth and differentiation factors, gene therapy, and cell therapy. Osteopromotive matrices are frequently employed for the local delivery and controlled release of these augmentation agents. Some matrices also provide an osteoconductive scaffold to support new bone growth. In this study, silkworm-derived silk fibroin was evaluated as an osteoconductive matrix for healing critical sized mid-femoral segmental defects in nude rats. Four treatment groups were assessed over eight weeks: silk scaffolds (SS) with recombinant human BMP-2 (rhBMP-2) and human mesenchymal stem cells (HMSC) that had been pre-differentiated along an osteoblastic lineage ex vivo (Group I; pdHMSC/rhBMP-2/SS); SS with rhBMP-2 and undifferentiated HMSCs (Group II; udHMSC/rhBMP-2/SS); SS and rhBMP-2 alone (Group III; rhBMP-2/SS); and empty defects (Group IV). Bi-weekly radiographs revealed a progressive and similar increase in Group I-III mean defect mineralization through post-operative week (POW) 8. Radiographs, dual energy x-ray absorptiometry, and micro-computed tomography confirmed that Groups I-III exhibited similar substantial and significantly (p<0.05) greater defect mineralization at POW 8 than the unfilled Group IV defects which remained void of bone. No significant differences in Groups I-III defect healing at POW 8 were apparent using these same assays or mechanical testing. Histology at POW 8 revealed moderately good bridging of the parent diaphyseal cortices with woven and lamellar bone bridging islands of silk matrix in Groups I and III. Group II defects possessed comparatively less new bone which was most abundant adjacent to the parent bone margins. Elsewhere the silk matrix was more often enveloped by poorly differentiated loose fibrous connective tissue. Group IV defects showed minimal new bone formation. None of the treatment groups attained the mean mineralization or the mean biomechanical strength of identical defects implanted with SS and pdHMSCs alone in a previous study. However, addition of rhBMP-2 to SS prompted more bone than was previously generated using udHMSC/SS or SS alone. These data imply the clinical potential of silk scaffolds and rhBMP-2 as composite osteopromotive implants when used alone or with select stem cell populations. Additional studies in larger species are now warranted.

Silk based biomaterials to heal critical sized femur defects.

Bone auto- and allografts have inherent drawbacks, therefore the treatment of non-unions and critical size defects in load bearing long bones would benefit from the use of osteopromotive biodegradable, biocompatible and mechanically durable matrices to enhance migration or delivery of cell populations and/or morphogens/cytokines. Silk fibroin biomaterial scaffolds were evaluated as osteopromotive matrices in critical sized mid-femoral segmental defects in nude rats. Four treatment groups were assessed over 8 weeks in vivo: silk scaffolds (SS) with human mesenchymal stem cells (hMSCs) that had previously been differentiated along an osteoblastic lineage in vitro (group I; pdHMSC/SS); SS with undifferentiated hMSCs (group II; udHMSC/SS); SS alone (group III; SS); and empty defects (group IV). When hMSCs were cultured in vitro in osteogenic medium for 5 weeks, bone formation was characterized with bimodal peak activities for alkaline phosphatase at 2 and 4 weeks. Calcium deposition started after 1 week and progressively increased to peak at 4 weeks, reaching cumulative levels of deposited calcium at 16 mug per mg scaffold wet weight. In vivo osteogenesis was characterized by almost bridged defects with newly formed bone after 8 weeks in group I. Significantly (P < 0.01) greater bone volumes were observed with the pdHMSC/SS (group I) implants than with groups II, III or IV. These three groups failed to induce substantial new bone formation and resulted in the ingrowth of cells with fibroblast-like morphology into the defect zone. The implantation of pdHMSC/SS resulted in significantly (P < 0.05) greater maximal load and torque when compared to the other treatment regimens. The pdHMSC/SS implants demonstrated osteogenic ability in vitro and capacity to thrive towards the healing of critical size femoral segmental defects in vivo. Thus, these new constructs provide an alternative protein-based biomaterial for load bearing applications.

Stereotyping the smoker: adolescents' appraisals of smokers in film.

OBJECTIVE: To assess the relation between demographic factors and film smoking stereotypes in adolescents and the potential influence of smoker stereotypes on smoking susceptibility. DESIGN: A cross sectional questionnaire survey of school students (n = 3041) aged 12-13 and 16-17 years who were asked to describe the personal characteristics of female and male smokers in films. SETTING: 15 primary or intermediate schools and 10 secondary schools in Auckland, New Zealand. RESULTS: Appraisals of smokers in film were strongly influenced by age and sex with younger adolescents and males more likely to see female smokers as sexy, intelligent and healthy whereas older students and females more often appraised female smokers as stressed bored and depressed. Overall, image stereotypes (sexy, stylish) were more likely to be significantly associated with smoking susceptibility than emotional sensitivity stereotypes (stressed, depressed etc). CONCLUSIONS: Adolescents differ significantly in their appraisal of smokers in films; however, image based stereotypes, rather than emotional sensitivity stereotypes, are significantly associated with smoking susceptibility.

Interface effects on mechanical properties of particle-reinforced composites.

OBJECTIVES: Effective bonding between the filler and matrix components typically improves the mechanical properties of polymer composites containing inorganic fillers. The aim of this study was to test the hypothesis that composite flexural modulus, flexure strength, and toughness are directly proportional to filler-matrix interfacial shear strength. METHODS: The resin matrix component of the experimental composite consisted of a 60:40 blend of BisGMA:TEGDMA. Two levels of photoinitiator components were used: 0.15, and 0.5%. Raman spectroscopy was used to determine degree of cure, and thermogravimetry (TGA) was used to quantify the degree of silane, rubber, or polymer attachment to silica and glass particles. Filler-matrix interfacial shear strengths were measured using a microbond test. Composites containing glass particles with various surface treatments were prepared and the modulus, flexure strength, and fracture toughness of these materials obtained using standard methods. Mechanical properties were measured on dry and soaked specimens. RESULTS: The interfacial strength was greatest for the 5% MPS treated silica, and it increased for polymers prepared with 0.5% initiator compared with 0.15% initiator concentrations. For the mechanical properties measured, the authors found that: (1) the flexural modulus was independent of the type of filler surface treatment, though flexural strength and toughness were highest for the silanated glass; (2) rubber at the interface, whether bonded to the filler and matrix or not, did not improve toughness; (3) less grafting of resin to silanated filler particles was observed when the initiator concentration decreased. SIGNIFICANCE: These findings suggest that increasing the strength of the bond between filler and matrix will not result in improvements in the mechanical properties of particulate-reinforced composites in contrast to fiber-reinforced composites. Also, contraction stresses in the 0.5 vs 0.15% initiator concentration composites may be responsible for increases in interfacial shear strengths, moduli, and flexural strengths.

Fatigue of restorative materials.

Failure due to fatigue manifests itself in dental prostheses and restorations as wear, fractured margins, delaminated coatings, and bulk fracture. Mechanisms responsible for fatigue-induced failure depend on material ductility: Brittle materials are susceptible to catastrophic failure, while ductile materials utilize their plasticity to reduce stress concentrations at the crack tip. Because of the expense associated with the replacement of failed restorations, there is a strong desire on the part of basic scientists and clinicians to evaluate the resistance of materials to fatigue in laboratory tests. Test variables include fatigue-loading mode and test environment, such as soaking in water. The outcome variable is typically fracture strength, and these data typically fit the Weibull distribution. Analysis of fatigue data permits predictive inferences to be made concerning the survival of structures fabricated from restorative materials under specified loading conditions. Although many dental-restorative materials are routinely evaluated, only limited use has been made of fatigue data collected in vitro: Wear of materials and the survival of porcelain restorations has been modeled by both fracture mechanics and probabilistic approaches. A need still exists for a clinical failure database and for the development of valid test methods for the evaluation of composite materials.

PriA mutations that affect PriA-PriC function during replication restart.

In Escherichia coli, repair and restart of collapsed replication forks is thought to be essential for cell growth. The replication restart proteins, PriA, PriB, PriC, DnaB, DnaC, DnaG, DnaT and Rep, form redundant pathways that recognize repaired replication forks and restart them. Recognition, modulation of specific DNA structures and loading of the replicative helicase by the replication restart proteins, is likely to be important for replication restart. It has been hypothesized that PriB and PriC function with PriA in genetically separate and redundant PriA-PriB and PriA-PriC pathways. In this study, the del(priB)302 or priC303:kan mutations were used to isolate the PriA-PriB and PriA-PriC pathways genetically so that the effects of three priA missense mutations, priA300 (K230R), priA301 (C479Y) and priA306 (L557P), on these pathways could be assessed. In a wild-type background, the three priA mutations had little, if any, effect on the phenotypes of UV resistance, basal levels of SOS expression and cell viability. In the priB mutant, priA300 and priA301 caused dramatic negative changes in the three phenotypes listed above (and others), whereas the third priA mutant allele, priA306, showed very little negative effect. In the priC mutant, all three priA mutations behaved similarly, producing little, if any, changes in phenotypes. We conclude that priA300 and priA301 mostly affect the PriA-PriC pathway and do so more than priA306. We suggest that PriA's helicase activity is important for the PriA-PriC pathway of replication restart.

The comparative anticaries efficacy of a dentifrice containing 0.3% triclosan and 2.0% copolymer in a 0.243% sodium fluoride/silica base and a dentifrice containing 0.243% sodium fluoride/silica base: a two-year coronal caries clinical trial on adults in Israel.

The purpose of this two-year clinical study was to provide a comparison of the anticaries efficacy associated with two commercially available, American Dental Association-accepted dentifrices: Colgate Total Toothpaste, which contains 0.3% triclosan and 2% copolymer in a 0.243% sodium fluoride/silica base; and Crest Cavity Fighting Toothpaste with Fluoristat, which contains 0.243% sodium fluoride in a silica base. The study was conducted in harmony with the published 1988 American Dental Association guidelines for studies geared toward the comparison of fluoride dentifrices. The study employed a double-blind parallel-group design, and involved adults living in communities throughout Israel. Qualifying subjects were randomly assigned to the two treatment groups, with multiple subjects in the same household all assigned to the dentifrice randomly allocated to the first among them. Caries examinations were conducted in accordance with U.S. Food and Drug Administration guidelines for the clinical evaluation of drugs to prevent dental caries. Two calibrated examiners performed all of the measurements. After treatment assignment, study participants were instructed to brush their teeth at home with their assigned dentifrice at least twice daily. Brushing instructions were reinforced by indoctrination in proper oral hygiene techniques by dental professionals, supplemented by pamphlets supplied by the sponsor and yearly mailings to participants, emphasizing good oral hygiene and the need to ensure compliance with the study. Post-baseline examinations were performed after one year of product use, and again after two years of product use. Three-thousand, three-hundred and ninety-two (3,392) subjects completed this two-year study. For these subjects, the mean caries scores (DFS, decayed or filled surfaces) at baseline were 21.96 for the Colgate Total Toothpaste group, and 21.49 for the Crest Cavity Fighting Toothpaste with Fluoristat group. For caries increment after one year, the respective means were 1.37 for the Colgate Total Toothpaste group, and 1.56 for the Crest Cavity Fighting Toothpaste with Fluoristat group. After two years, the mean caries increments were 1.46 for the Colgate Total Toothpaste group, and 1.75 for the Crest Cavity Fighting Toothpaste with Fluoristat group. No statically significant difference was indicated between the treatment groups at baseline. However, for both the one-year and two-year increments, there was a statistically significant difference between treatment groups. Relative to the Crest Cavity Fighting Toothpaste with Fluoristat group, the Colgate Total Toothpaste group presented a 12.2% reduction in caries increment scores at one year, and a 16.6% reduction in caries increment scores at two years. In accordance with the procedures and standards provided by the published guidelines of the American Dental Association for the comparison of the anticaries efficacy of fluoride dentifrices, the results of this study support the conclusion that Colgate Total Toothpaste provides a superior level of coronal anticaries efficacy compared to Crest Cavity Fighting Toothpaste with Fluoristat.

The enhanced anticaries efficacy of a sodium fluoride and dicalcium phosphate dihydrate dentifrice in a dual-chambered tube. A 2-year caries clinical study on children in the United States of America.

PURPOSE: To clinically evaluate and compare a dentifrice system in a dual-chambered tube, wherein one chamber contained sodium fluoride in a silica base and the other chamber contained dicalcium phosphate dihydrate (Test Dentifrice delivering 0.243% sodium fluoride), to a dentifrice containing 0.243% sodium fluoride in a silica base (Positive Control Dentifrice). MATERIALS AND METHODS: This study was conducted in harmony with the published 1988 American Dental Association guidelines for studies geared toward the comparison of fluoride dentifrices. This 2-yr caries clinical study employed a double-blind, parallel-group design, and involved 5-17 yr-old children from the Central and South areas of Florida and from the Lares area of Puerto Rico. Qualifying subjects were stratified according to age and sex, and were randomly assigned to the two treatment groups, with multiple subjects in the same household all assigned to the dentifrice randomly allocated to the first among them. Caries examinations were conducted in accordance with U.S. Food and Drug Administration guidelines for the clinical evaluation of drugs to prevent dental caries. Two calibrated examiners performed all the measurements. After treatment assignment, study participants were instructed to brush their teeth at home with their assigned dentifrice at least twice daily. Brushing instructions were reinforced by indoctrination in proper oral hygiene techniques by dental professionals, supplemented by pamphlets supplied by the sponsor and yearly mailings to participants, emphasizing good oral hygiene and the need to enforce compliance with the study. Post-baseline examinations were performed after 1 yr of product use, and again after 2 yrs of product use. RESULTS: Two thousand five hundred six (2,506) subjects completed this 2-yr study. For these subjects, the mean caries scores (DMFS, decayed, missing and filled tooth surfaces) at baseline were 2.29 for the Test Dentifrice group, and 2.47 for the Positive Control Dentifrice group. For caries increments after 1 yr, the respective means were 0.69 for the Test Dentifrice group and 0.81 for the Positive Control Dentifrice group. Finally, after 2 yrs, the mean caries increments were 1.25 for the Test Dentifrice group, and 1.46 for the Positive Control Dentifrice group. No statistically significant difference was indicated between the treatment groups at baseline or between the 1-yr caries increment scores. However, there was a statistically significant difference in the 2-yr caries increment scores between the treatment groups. Relative to the Positive Control Dentifrice group, the Test Dentifrice group presented a 14.38% reduction in caries increment scores at 2 yrs. In accordance with the procedures and standards provided by the published guidelines of the American Dental Association for the comparison of the anticaries efficacy of fluoride dentifrices, the results of this study support the conclusion that the dentifrice system in a dual-chambered tube, wherein one chamber contained sodium fluoride in a silica base and the other chamber contained dicalcium phosphate dihydrate, delivering 0.243% sodium fluoride, provided a superior level of anticaries efficacy than did the dentifrice containing 0.243% sodium fluoride in a silica base.

The enhanced anticaries efficacy of a sodium fluoride and dicalcium phosphate dihydrate dentifrice in a dual-chambered tube. A 2-year caries clinical study on children in Brazil.

PURPOSE: To clinically evaluate and compare a dentifrice system in a dual-chambered tube, wherein one chamber contained sodium fluoride in a silica base and the other chamber contained dicalcium phosphate dihydrate (Test Dentifrice delivering 0.243% sodium fluoride), to a dentifrice containing 0.243% sodium fluoride in a silica base (Positive Control Dentifrice). MATERIALS AND METHODS: This study was conducted in harmony with the published 1988 American Dental Association guidelines for studies geared toward the comparison of fluoride dentifrices. This 2-yr caries clinical study employed a double-blind, parallel-group design, and involved 6-10 yr-old children from the metropolitan area of Maceio, Alagoas, Brazil. Qualifying subjects were stratified according to age and sex, and were randomly assigned to the two treatment groups, with multiple subjects in the same household all assigned to the dentifrice randomly allocated to the first among them. Caries examinations were conducted in accordance with U.S. Food and Drug Administration guidelines for the clinical evaluation of drugs to prevent dental caries. One calibrated examiner performed all the measurements. After treatment assignment, study participants were instructed to brush their teeth at home with their assigned dentifrice at least twice daily. Brushing instructions were reinforced by indoctrination in proper oral hygiene techniques by dental professionals, supplemented by pamphlets supplied by the sponsor and yearly mailings to participants, emphasizing good oral hygiene and the need to enforce compliance with the study. Post-baseline examinations were performed after 1 yr of product use, and again after 2 yrs of product use. RESULTS: Two thousand four hundred thirty-two (2,432) subjects completed this 2-yr study. For these subjects, the mean caries scores (DMFS, decayed, missing and filled tooth surfaces) at baseline were 3.84 for the Test Dentifrice group, and 4.06 for the Positive Control Dentifrice group. For caries increments after 1 yr, the respective means were 2.02 for the Test Dentifrice group and 2.12 for the Positive Control Dentifrice group. Finally, after 2 yrs, the mean caries increments were 4.30 for the Test Dentifrice group, and 4.83 for the Positive Control Dentifrice group. No statistically significant difference was indicated between the treatment groups at baseline or between the 1-yr caries increment scores. However, there was a statistically significant difference in the 2-yr caries increment scores between the treatment groups. Relative to the Positive Control Dentifrice group, the Test Dentifrice group presented a 10.97% reduction in caries increment scores at 2 yrs. In accordance with the procedures and standards provided by the published guidelines of the American Dental Association for the comparison of the anticaries efficacy of fluoride dentifrices, the results of this study support the conclusion that the dentifrice system in a dual-chambered tube, wherein one chamber contained sodium fluoride in a silica base and the other chamber contained dicalcium phosphate dihydrate, delivering 0.243% sodium fluoride, provided a superior level of anticaries efficacy than did the dentifrice containing 0.243% sodium fluoride in a silica base.

Effects of mutations involving cell division, recombination, and chromosome dimer resolution on a priA2::kan mutant.

Recombinational repair of replication forks can occur either to a crossover (XO) or noncrossover (non-XO) depending on Holliday junction resolution. Once the fork is repaired by recombination, PriA is important for restarting these forks in Escherichia coli. PriA mutants are Rec(-) and UV sensitive and have poor viability and 10-fold elevated basal levels of SOS expression. PriA sulB mutant cells and their nucleoids were studied by differential interference contrast and fluorescence microscopy of 4',6-diamidino-2-phenylindole-stained log phase cells. Two populations of cells were seen. Eighty four percent appeared like wild type, and 16% of the cells were filamented and had poorly partitioned chromosomes (Par(-)). To probe potential mechanisms leading to the two populations of cells, mutations were added to the priA sulB mutant. Mutating sulA or introducing lexA3 decreased, but did not eliminate filamentation or defects in partitioning. Mutating either recA or recB virtually eliminated the Par(-) phenotype. Filamentation in the recB mutant decreased to 3%, but increased to 28% in the recA mutant. The ability to resolve and/or branch migrate Holliday junctions also appeared crucial in the priA mutant because removing either recG or ruvC was lethal. Lastly, it was tested whether the ability to resolve chromosome dimers caused by XOs was important in a priA mutant by mutating dif and the C-terminal portion of ftsK. Mutation of dif showed no change in phenotype whereas ftsK1cat was lethal with priA2kan. A model is proposed where the PriA-independent pathway of replication restart functions at forks that have been repaired to non-XOs.

Adolescent perceptions of smoking imagery in film.

Smoking amongst adolescents in New Zealand continues to be a problem, with more than a one-third increase in smoking prevalence between 1992 and 1997. Favourable portrayals of smoking in the media have been cited as potential motivators of the initiation of smoking among adolescents. To date, however, its role in influencing smoking perceptions and behaviours has not received systematic analysis. A qualitative study was conducted to explore how adolescents interpret and decode smoking imagery in movies. Data was collected through focus groups. Same-gender groups of 12- and 13-year-old students were interviewed at their schools. Participants discussed their recollections of and responses to portrayals of smoking in recently viewed films, as well as their perceptions of smoking in general. Students perceived that smoking in film is both highly prevalent and recognisable, and they regarded on-screen-smoking imagery as an accurate reflection of reality. Adolescents in this study were predominantly nonchalant towards the inclusion of smoking images in film, and they perceived an unrealistically high prevalence of smoking amongst peers and adults. Their noncholant response is linked with the perception that smoking is normal and prevalent and with the broad understanding of the constructed nature of media imagery. Smoking imagery in film may play a critical role in reinforcing cultural interpretations of tobacco use, such as its role as a means of stress relief, development of self-image and as a marker of adult independence.

Lifetime predictions for resin-based composites using cyclic and dynamic fatigue.

Because dental restorative materials undergo fatigue in use, testing is often performed in the laboratory to evaluate material responses to cyclic loading. The purpose of this study was to compare the lifetime predictions resulting from two methods of fatigue testing: dynamic and cyclic fatigue. Model composites were made in which one variable was the presence of a silanizing agent, and specimens tested in 4-point flexure. Cyclic fatigue was carried out at a frequency of 5 Hz, while dynamic fatigue testing spanned seven decades of stress rate application. Data were reduced and the crack propagation parameters for each material were calculated from both sets of fatigue data. These parameters were then used to calculate an equivalent static tensile stress for a 5-year survival time. The 5-year survival stresses predicted by dynamic fatigue data were approximately twice those predicted by cyclic fatigue data. In the absence of filler particle silanization, the survival stress was reduced by half. Aging in a water-ethanol solution reduced the survival stresses by a factor of four to five. Cyclic fatigue is a more conservative means of predicting lifetimes of resin-based composites.

Analysis of the nursing work force compared with national trends.

Nursing work force analysis gives crucial data for administrators, allowing them to anticipate employment opportunities and areas of limited growth. Using an economic model of supply and demand, this study examined the employment and educational needs for nurses. In many areas of data collection, the District of Columbia data paralleled national trends, indicating the nationwide relevance of the conclusions. Projected mismatches between the type of nurses (by educational preparation) entering the work force and the skills required for the job vacancies could lead to increased demand for nurses with certain credentials as well as shortages of nurses in certain types of facilities.

Size effect in resin/glass composite flexure strengths.

The objective of this study was to test the hypothesis that composite restorative materials possess an elastic-brittle nature and therefore will exhibit a size effect for flexure strength data. The experimental material consisted of 20 wt% 60:40 BISGMA:TEGDMA, 10 wt% colloidal silica, and 70 wt% Sr glass and was cured by light irradiation. Two sizes of flexure specimens were fabricated: 3.2x1.6x35 mm, and 6.25x3.1x35 mm. Half of the specimens made were soaked to equilibrium weight gain in 50:50 ethanol:water. The fracture strengths were measured in four-point bending tests. The beams under load were modelled by the finite element package ABAQUS. A statistical fracture mechanics methodology embodied in a public domain computer program called CARES/LIFE, developed by NASA, utilized the ABAQUS input and the fracture strengths of the smaller specimens to predict the fracture strengths of the larger specimens. In making the computation it used an approach that combines a Weibull distribution of flaw size with Batdorf's fracture mechanical model for failure at a material flaw. Both the soaked and unsoaked specimens exhibited Weibull behaviour, with shape parameters ranging from 4.04 to 8.15. Soaking had a clearly detrimental effect on the strengths of specimens of both sizes, and produced a comparable percentage reduction in the estimated scale parameter of the fracture strength distribution. Both the soaked and unsoaked specimens also exhibited a clear and comparable size effect, i.e. the larger specimens had a fracture strength that was lower than that of the smaller specimens by roughly the same percentage. Moreover, the magnitude of the size effect was well predicted by the CARES/LIFE methodology for both the soaked and the dry specimens. The elastic-brittle character of both soaked and unsoaked composite specimens was validated by load-deflection data, the magnitude of the Weibull shape parameters of the observed fracture strength data (<10), and the observed effect of specimen size. The accuracy of CARES/LIFE in predicting the magnitude of the observed size effect in beams of two different sizes strongly suggests that CARES/LIFE will be useful for computation of failure probabilities for clinically relevant structures.

Home-based leg strengthening for older adults initiated through private practice.

BACKGROUND: Leg strength correlates with functional ability in the frail elderly, many of whom can be reached through a private practice setting. The purpose of this study was to demonstrate the feasibility of physician-prescribed, home-based, clinic-monitored, high-intensity leg-strengthening treatment among elderly patients with a variety of medical problems. METHODS: Twenty-two elderly patients with a variety of chronic medical conditions were invited to participate during regularly scheduled office visits if they had difficulty rising from a chair and an unsteady, cautious gait (age 85.1 +/- 5.7, 14 female). Physical therapists (PT) instructed patients to lift ankle weights at home, three times per week. Patients visited PT five times over a 12-week period. Weights were increased at each visit. RESULTS: Patients' one-repetition maximum increased (right leg 13 to 21 lb, P = 0.00; left leg 15 to 22 lb, P = 0.00). Patients also improved in habitual (18 to 12 s, P = 0.01) and tandem (38 to 26 s, P = 0.00) 20-foot walking times and sit-to-stand time (5 to 3 s, P = 0.01). CONCLUSION: The primary care physician can initiate a home-based leg-strengthening program that is practical for and well tolerated by the frail elderly.

Focus of doctor-patient communication in follow-up consultations for patients treated surgically for colorectal cancer.

A series of consultations between patients treated surgically for colorectal cancer and their hospital consultants were examined to establish the main focus of the consultation at various stages in the post-surgical period. The results showed that follow-up consultations were predominantly doctor driven. Patients interviewed less than 12 months since the time of surgery (short-term group) were more likely to receive a longer consultation with a significantly higher number of verbal interactions (questions, responses) than patients more than 12 months since surgery at the time of interview (long-term group). Furthermore, patients in the short-term group played a greater participatory role within consultations than patients in the long-term group. The predominant focus throughout all consultations was biomedical, with little attention afforded to patients' expressions of post-operative anxiety. At present, it appears that out-patient consultations play a minimal role in either detecting or addressing psychosocial morbidity amongst colorectal cancer patients in the post-surgical period.

Efficacy of a dentifrice containing 5% potassium nitrate and 1500 PPM sodium monofluorophosphate in a precipitated calcium carbonate base on dentinal hypersensitivity.

The effect on dentinal hypersensitivity from the use of a dentifrice containing 5.0% potassium nitrate, 1500 ppm sodium monofluorophosphate in a precipitated calcium carbonate (PCC) base over an eight-week period was compared to a placebo dentifrice without potassium nitrate. A total of forty-eight subjects were entered into the study and stratified into two balanced groups according to their baseline mean thermal (air blast) and tactile (Yeaple Probe) sensitivity scores. The two groups were randomly assigned to use either the potassium nitrate/PCC dentifrice or a placebo dentifrice without potassium nitrate. The two groups were well balanced with regard to their mean baseline thermal tactile sensitivity scores, sex and age. Subjects were instructed to brush their teeth twice daily (morning and evening) for one minute with their assigned dentifrice and a commercially available soft-bristled toothbrush. Dentinal hypersensitivity examinations, which included tactile and thermal sensitivity, were conducted at baseline, four weeks, and eight weeks. Examinations were conducted by the same dental examiner (TS) on the subjects at each examination. After four weeks' use of their assigned products, those subjects in the potassium nitrate/PCC dentifrice group demonstrated statistically significant improvements (p < 0.0001), as compared to the placebo dentifrice without potassium nitrate, in tactile and thermal sensitivity. After eight weeks' use of their assigned products, those subjects in the potassium nitrate/PCC dentifrice group again demonstrated statistically significant improvements (p < 0.0001), in tactile and thermal sensitivity, as compared to the placebo dentifrice without potassium nitrate. Thus it can be concluded from this study that the use of a dentifrice containing 5.0% potassium nitrate and 1500 ppm sodium monofluorophosphate in a precipitated calcium carbonate (PCC) base is a clinically effective method for reducing dentinal hypersensitivity.

Weibull models of fracture strengths and fatigue behavior of dental resins in flexure and shear.

In estimating lifetimes of dental restorative materials, it is useful to have available data on the fatigue behavior of these materials. Current efforts at estimation include several untested assumptions related to the equivalence of flaw distributions sampled by shear, tensile, and compressive stresses. Environmental influences on material properties are not accounted for, and it is unclear if fatigue limits exist. In this study, the shear and flexural strengths of three resins used as matrices in dental restorative composite materials were characterized by Weibull parameters. It was found that shear strengths were lower than flexural strengths, liquid sorption had a profound effect on characteristic strengths, and the Weibull shape parameter obtained from shear data differed for some materials from that obtained in flexure. In shear and flexural fatigue, a power law relationship applied for up to 250,000 cycles; no fatigue limits were found, and the data thus imply only one flaw population is responsible for failure. Again, liquid sorption adversely affected strength levels in most materials (decreasing shear strengths and flexural strengths by factors of 2-3) and to a greater extent than did the degree of cure or material chemistry.