Associations of mortality and cardiovascular disease risks with diabetes and albuminuria in urban Indigenous Australians: the DRUID follow-up study.

AIM: To assess the relationships of diabetes and albuminuria with all-cause mortality and cardiovascular disease outcomes in a population without prior cardiovascular disease using data from the Darwin Region Urban Indigenous Diabetes (DRUID) study. METHODS: We conducted a prospective cohort study of 706 participants (aged 15-81 years, 68% women) without prior cardiovascular disease who underwent a 75-g oral glucose tolerance test. Deaths and fatal or non-fatal cardiovascular disease were determined over 7 years, and hazard ratios with 95% CIs and population attributable risks were estimated for baseline glycaemia and albuminuria. RESULTS: Compared with normoglycaemia and after adjustment for age, sex, hypertension, dyslipidaemia and smoking, known diabetes was associated with an adjusted hazard ratio of 4.8 (95% CI 1.5-14.7) for all-cause mortality and 5.6 (95% CI 2.1-15.2) for cardiovascular disease. Compared with normoalbuminuria, the respective adjusted risks for macroalbuminuria were 10.9 (95% CI 3.7-32.1) and 3.9 (95% CI 1.4-10.8). The Adjusted all-cause mortality and cardiovascular disease estimated population attributable risks for diabetes were 27% and 32%, and for albuminuria they were 32% and 21%, respectively. CONCLUSIONS: In our study population, the burden of mortality and cardiovascular disease was largely driven by diabetes and albuminuria. This finding on the influence of diabetes and albuminuria is consistent with reports in other high-risk Indigenous populations and should be better reflected in risk scores and intervention programmes.

How well is the National Cervical Screening Program performing for Indigenous Australian women? Why we don't really know, and what we can and should do about it.

Since its inception in 1991, Australia's organised approach to cervical screening, the National Cervical Screening Program (NCSP), has seen a 50% reduction in both incidence and mortality from cervical cancer in Australia. However, Indigenous Australian women continue to experience a disproportionately higher burden of cervical cancer. No national data on screening participation of Indigenous women currently exist, in large part because pathology forms, the primary source of data for Pap Test Registers (PTR), do not record Indigenous status. While including Indigenous status on pathology forms is the obvious solution for producing essential information about cervical screening of Indigenous women, this will require an appropriate consultative process and it will be many years before reliable data are available. One interim option being explored is the feasibility of linking the PTR to another data source which includes Indigenous status, such as hospital data. However, despite its promise, there remain major impediments to obtaining useful linked data in Australia, and it continues to be unclear whether such an approach is viable for routine reporting. If we are to understand and improve cervical screening participation and outcomes for Indigenous women in the foreseeable future, Australia needs to act now to include Indigenous status in pathology forms and (subsequently) PTRs.

Performance of comorbidity indices in measuring outcomes after acute myocardial infarction in Australian indigenous and non-indigenous patients.

BACKGROUND: Indigenous Australians have higher prevalence of chronic diseases and worse acute care outcomes than other Australians. The extent to which higher chronic disease comorbidity levels are responsible for their worse outcomes is not clear, and the performance of comorbidity indices has not been assessed for this population with very high comorbidity levels. METHODS: Using hospital separations data, the Charlson and Elixhauser comorbidity indices were used to measure chronic disease prevalence in 2035 indigenous and non-indigenous patients hospitalised after their first acute myocardial infarction (AMI) in the Northern Territory of Australia between 1992 and 2004, and to adjust for comorbidity in multivariate analysis of mortality outcomes (in-hospital and long-term deaths from coronary heart disease and all causes). Index performance was assessed by the difference between C statistic, Akaike information criterion statistic and estimate of excess indigenous mortality in models with and without comorbidity adjustment. RESULTS: Comorbidity index scores were higher for indigenous than non-indigenous patients and increased considerably over time, at least partly because of information bias. Indigenous patients' higher risk of in-hospital all-cause death was almost fully explained by their higher comorbidity levels. Their higher risk of long-term coronary heart disease and all-cause death was partially explained by higher comorbidity levels. Charlson and Elixhauser indices performed satisfactorily and similarly in this population. CONCLUSION: Comorbidity indices performed well in a population with very high chronic disease prevalence. After adjusting for comorbidity, short-term outcomes were similar for indigenous and non-indigenous AMI patients, but comorbidity at the time of the acute episode only partly explained the worse long-term outcomes for indigenous patients.

Cancer diagnosis and treatment in the Northern Territory: assessing health service performance for indigenous Australians.

Indigenous Australians with cancer are diagnosed with more advanced disease and have lower survival than other Australians. To investigate reasons for these differences. Retrospective cohort study of 1197 indigenous and nonindigenous people in the Northern Territory diagnosed with cancers of the colon and rectum, lung, breast, cervix and non-Hodgkin lymphoma between 1991 and 2000. Outcome measures were stage at diagnosis and relative risk of cancer death. Indigenous people compared with nonindigenous people had higher relative odds of advanced stage of cancer at diagnosis (relative odds 1.9, 95% CI 1.3-2.7) for four cancers but lower relative odds for lung cancer (relative odds 0.3, 95% CI 0.2-0.5). None of the potentially contributing factors examined could explain this difference. Risk of cancer death (adjusted for cancer type and age and stage at diagnosis) was higher in indigenous than in nonindigenous people (relative risk 1.7, 95% CI 1.4-2.1). This difference, however, was confined to indigenous people with an indigenous first language (relative risk 2.9, 95% CI 2.2-3.8). Adjustment for cancer treatment variables further reduced but did not eliminate this higher risk of death. Although more advanced stage at diagnosis appeared to be a sufficient explanation for poorer cancer outcome in indigenous people whose first language was English, poorer treatment also contributed to, but was still not sufficient to explain, poorer outcome in those who had an indigenous first language. Other factors, possibly including communication difficulties, knowledge of and attitudes to cancer symptoms and treatment and social and cultural 'distance' from mainstream health services, may also be involved.

In vitro wear of composite with varied cure, filler level, and filler treatment.

For the clinical wear of composite filing materials to be reduced, compositional factors such as degree of cure, filler level, and silanation level should be optimized. An oral-wear-stimulating machine was used to explore the effects of these factors on abrasion and attrition wear as well as on opposing enamel wear. The composites were made from Sr glass (1-2 micron avg) and a 50/50 Bis-GMA/TEGDMA resin. Series I (A-D, E) were light-cured (Triad II) for 9, 12, 25, and 40 sec/side to produce degree of cure (DC) as measured by FTIR of 56, 60, 61, and 63%, respectively. E received an additional heat cure (120 degrees C for 10 min) to reach a DC of 66%. Series II (D, F-I) were filled to 62, 53, 48, 37, and 28 vol%, respectively. In series III (D, J-M), the portion of fillers treated with a silane coupler (MPS) was 100, 80, 60, 40, and 20%, respectively. Samples were cycled 50,000 times against an enamel antagonist in a poppy seed/PMMA slurry in the oral wear simulator to produce abrasion (load = 20 N) and attrition (load = 70 N) simultaneously. Wear depth (micron: n = 5) was measured by profilometry. Results for each series were analysed by ANOVA/Turkey's (p < or = 0.05). The wear depths did reflect cure values, though only the abrasion difference for E < A was significant. Greater wear was correlated with lower filler levels (r2 = 0.88; p < 0.05), significantly increasing below 48 vol% (G). Wear increased linearly as the percent of silane-treated fillers was reduced (r2 = 0.99; p < 0.05). Abrasion and attrition did not differ significantly for any composite. Wear of the opposing enamel was largely unchanged by these factors. Compositional factors including degree of cure, filler level, and silanation directly affected the wear resistance of dental composites evaluated in an oral wear simulator.

Evaluation of subsurface defects created during the finishing of composites.

The objective of this study was to test the hypothesis that a degraded subsurface layer containing microcracks is produced in dental composites as a result of finishing procedures. Various composites in the form of rectangular bars were finished with a 12-fluted carbide bur or a fine diamond within minutes of light-curing, and were subsequently stained with silver nitrate. Microscopic evaluation revealed that significant penetration of stain occurred in the unfinished as well as in the finished surfaces. The extent of dye penetration that could be directly attributed to a damaged layer produced by the finishing procedure was less than 10 microns, being greatest for a microfill (Silux Plus) and a hybrid (P-50) composite. There was no difference between the effects of the finishing instruments. SEM analysis of the subsurface showed an absence of any cracks for the composites. However, occasional disruption of the interface between the pre-polymerized resin fillers and the matrix was apparent for the microfill material. The results showed that only a very limited subsurface damage may be created in certain composites during the initial contouring of a restoration.

Wear and marginal breakdown of composites with various degrees of cure.

Loss of anatomical form due to wear has been cited as one factor limiting the clinical use of posterior composites. The physical properties and possibly the wear resistance of composite are influenced by the extent to which it is cured. The aim of this study was to vary degree of conversion (DC) in composites to test the hypothesis that resistance to wear and marginal breakdown could be improved by enhanced curing. A light-cured hybrid composite containing a 50% Bis-GMA/50% TEGDMA resin and 62 vol% of strontium glass (1 to 2 microm) with microfill silica was formulated (Bisco). Composite was placed into two 2.5-mm-diameter cylindrical holes in Co-Cr teeth replacing first and second molars in the mandibular dentures of 50 edentulous patients. The composites were light-cured for different time periods (9 s, 12 s, 25 s, 40 s, and 40 s + 10 min at 120 degrees C) and then polished. The microfill Heliomolar was also tested. DC (%) was measured by FTIR and ranged between 55% for 9 s of light-curing and 67% for 40 s of light-curing followed by heat application. Impressions were evaluated at baseline, 6 mo, 1 yr, and 2 yrs. Stone casts were evaluated independently by three observers to determine the % of the total margin exhibiting breakdown. Epoxy replicas were measured with a profilometer for wear. Wear of the hybrid composite at 2 yrs ranged from a high of 144 microm with 9 s of light-curing to a low of 36 microm with 40 s of light-curing followed by heat. Heliomolar exhibited from 11 to 16 microm of wear at 2 yrs. There was a strong negative correlation (r2 = 0.91) between the degree of cure and the abrasive wear of the hybrid composites. Marginal breakdown was negligible for the hybrids, and was reduced for the microfill from 40% to 15% of the margin by heat treatment. This study showed that the resistance to abrasive wear of a dental composite could be improved by enhancement of its degree of conversion.

The effects of adhesive thickness on polymerization contraction stress of composite.

A layer of an unfilled adhesive resin placed between the tooth and composite restoration has been shown to absorb some of the stress generated in the composite during polymerization and to reduce interfacial leakage. The objectives of this study were to measure the change in polymerization contraction stress of bonded composite as the thickness of the resin adhesive was systematically varied, and to correlate the effects of the adhesive thickness and reduced stress on marginal leakage in class V cavities. The maximum contraction force of composite (Herculite XRV) was measured in a tensilometer as the thickness of the adhesive bonding agent (Scotchbond MP) was varied from 20 to 300 microm. Composite was placed in Class V cavities prepared on the labial surfaces of bovine teeth to which different thicknesses of adhesive had been applied by layering, and a marginal leakage test was performed by means of staining with silver nitrate. Contraction stress decreased significantly as the adhesive thickness was increased. This result was supported by a theoretical examination of the data. In class V cavities, additional adhesive layering in the marginal area reduced the overall degree of microleakage. The contraction stress generated during the placement of a composite restoration contributes significantly to early marginal leakage, and this stress was significantly absorbed and relieved by the application of an increasing thickness of low-stiffness adhesive.

A single issue program in an isolated area: mammography screening in Darwin, NT.

OBJECTIVE: A process evaluation of the Northern Territory (NT) mammography program, NT Breast Screen (NTBS), during its initial 18 months of operation. METHODS: The study was undertaken in Darwin, NT, from December 1994 to May 1996. Clinical outcomes were obtained by reviewing computerised and manual program records to determine waiting times for results, recall rates and cancer detection rates. Client satisfaction was assessed by a questionnaire sent to all women with normal results over a 12-week period. General practitioner satisfaction was assessed by a questionnaire sent to all general practitioners in the region who had one or more clients who had attended the service. RESULTS: During this time, 2,882 screening mammograms were performed; 98 women were recalled for assessment (3.4%). Breast cancer was detected in 10 women (3.5 per 1000 women screened). The program was well accepted by clients and general practitioners. Performance criteria were not met for waiting times for results. CONCLUSIONS: NTBS faced challenges because of its small and dispersed population, a lack of local radiologists with mammographic experience and the conflict with other pressing health issues, particularly in Aboriginal health. Despite these challenges, the program functioned effectively during its initial 18 months. IMPLICATIONS: Mammography screening programs in isolated areas can function effectively. The constraints encountered by NTBS are likely to apply to similar programs. Issues identified requiring further research are the psychological consequences of long waiting times for results, and the prioritisation of mammography for Aboriginal women.

Evaluation of composite wear with a new multi-mode oral wear simulator.

OBJECTIVES: The goals of this study were to develop a machine which simultaneously produces wear through the two main oral wear mechanisms of abrasion and attrition by the action of an enamel antagonist and to compare the results obtained for dental composites using this machine to those obtained from clinical studies and other in vitro studies. METHODS: The accuracy of this new wear tester was determined by examining 11 commercial composite filling materials and 1 amalgam. Specimens were subjected to three-body abrasion and attrition wear for 50,000 cycles. Profilometry was used to quantitate wear of the composites. Linear regression analysis was used to correlate the results to those obtained from clinical studies, as well as from other in vitro wear testers. The area of enamel wear was also determined by image analysis. The SEM was used to evaluate the wear surfaces. RESULTS: The lowest abrasion wear was recorded for the amalgam and for the microfill and smaller-particle composites. Attrition wear was enhanced for the microfill composites and one small-particle hybrid. There was a strong correlation between the results obtained with the new wear tester and those obtained in the clinical trials cited in the literature. Wear of the enamel antagonist was the greatest for the composites with the largest particle sizes. The wear tester showed a reasonable correlation with other wear-producing machines. SIGNIFICANCE: A new wear tester developed to evaluate and discriminate abrasion and attrition wear provided results similar to those reported in the literature for a variety of commercial composites. The new machine is capable of characterizing the behavior of a material in multiple wear modes simultaneously with one simple, realistic test.

Reduction of composite contraction stress through non-bonded microfiller particles.

OBJECTIVES: To determine the reduction in composite polymerization stress through the addition of non-bonded microfiller particles. METHODS: Microfillers that were unsilanated, silanated, and treated with a nonfunctional silane were added to dental resin and to a small-particle composite. The contraction stress generated by these materials was measured by polymerizing them between glass plates mounted in a mechanical testing machine. The maximum force was recorded 15 min after photo-initiation. Results were analysed by ANOVA (analysis of variance)/Turkey's test (p < or = 0.05). RESULTS: The addition of non-functional silanated microfillers to dental resin resulted in a significant 50% decrease in polymerization stress. The addition of unsilanated microfillers did not reduce the contraction stress. When added to small-particle composite, the unsilanated microfillers produced a significant 30% reduction in contraction stress compared to the composite containing silanated microfillers. The non-functional silanated microfillers did not reduce the contraction stress in the small-particle composite. SIGNIFICANCE: The polymerization shrinkage of dental composite can impose high levels of stress on the tooth surfaces to which it is bonding. This contraction stress can lead to failure of bond formation with the surrounding tooth structure. Microfiller particles that are not bound to the resin matrix might provide sites for relief of internal stresses, significantly reducing contraction stress in dental composite.

Rate of elution of leachable components from composite.

The uptake of solvent and the elution of molecules from a dental composite and an unfilled resin were monitored with time during soaking in either water or an ethanol/water mixture. The results showed that approximately 50% of the leachable species were eluted from the composite within three hours of soaking in water, while 75% of the leachable molecules were eluted into the ethanol/water mixture. Elution of nearly all of the leachable components was complete within a 24-hour period in either solvent. The study lends support to the view that dental composites do not provide a chronic source of unreacted monomer to the pulp or other oral tissues, due to a rapid and complete elution of the molecules.

Post-cure heat treatments for composites: properties and fractography.

Two commercial and four experimental composites were subjected to post-cure heat treatments of 10 min and 3 h duration immediately after light-curing. Fracture toughness, flexural modulus, microhardness and degree of conversion (FTIR) were evaluated 24 h later. The results showed that post-cure heat treatments at 120 degrees C of short or long duration can be used to produce significant improvements in the degree of cure and the mechanical properties of dental composites used as inlays. A 10 min heat treatment was as effective as a 3 h treatment in enhancing properties and degree of cure. In addition, a 3 h heat treatment carried out 7 days after the initial light-curing was capable of improving properties and cure to almost the same extent as the immediate heat treatments. The improvement in properties, in conjunction with the fractography, indicate a toughening of the filled resin matrix and possibly an improved filler/matrix adhesion in the microfills. The changes appear to be predominantly the result of an increase in degree of cure.

In vitro evaluation of the marginal degradation of dental composites under simulated occlusal loading.

OBJECTIVES: Our objective was to use an in vitro oral wear simulator to compare the susceptibility to marginal breakdown of different classes of dental composites. METHODS: Two microfill composites (Silux Plus, 3M and Heliomolar, Vivadent), two minifills (Z100, 3M and Herculite, Kerr) and two midifills (Fulfil, Caulk and Clearfil, Kuraray) were placed in two increments (40 s cure) into class I cavities (5 x 3.5 x 2 mm3 deep) cut into the facial enamel surfaces of bovine incisors treated with an adhesive (Scotchbond MP, 3M). The restored teeth were aged 1 day in water, mounted in the OHSU oral wear simulator, covered with a slurry of poppy seeds/PMMA beads and subjected to 50 K cycles of wear against an enamel stylus [J.R. Condon, J.L. Ferracane, Evaluation of composite wear with a new multi-mode oral wear simulator, Dent. Mater. 12 (1996) 218-226). The specimens (n = 10) were positioned to produce abrasive wear (load = 20 N] across one margin and attrition wear (load = 70 N) across the second margin. Volume loss of material (mm3 x 1000) was estimated from 10 profilometric tracings perpendicular to the attrition margin, and then differentiated into composite and enamel degradation. Fracture toughness of the composites was measured in bending with the single-edge notch technique. Results were compared with ANOVA and Tukey's test at p < 0.05. RESULTS: Significant wear of the composite was produced at the attrition margin. Enamel degradation at the margin paralleled the composite results. The microfills, and to a lesser extent the minifills, showed more marginal breakdown than the midifill composites. Marginal breakdown shows an excellent inverse correlation with fracture toughness for these composites. SIGNIFICANCE: These results are in general agreement with clinical studies showing greater marginal degradation for microfill composites and suggest that the OHSU oral wear simulator may be a useful adjunct for the study of the marginal degradation of dental composites.

Properties of heat-treated composites after aging in water.

OBJECTIVES: Post-cure heat treatments have been shown to increase the fracture toughness and elastic modulus of composites. The objective of this study was to determine if the increase remained after the composites were aged in water. METHODS. The fracture toughness (K(lc)), flexural modulus and flexural strength of four experimental and one commercial composite (Z-100, 3M Dental Products) were tested after 1, 7, 30, 60 and 180 d of aging in 37 degrees C water. The four experimental composites were made with a BisGMA/TEGDMA resin and were characterized as follows: Micro = 38 vol% silane-treated silica, Fine = 65 vol% silane-treated quartz of 1-2 micrometer average size, Hybrid = 65 vol% silane treated quartz of a mixture of 1-2 micrometer average and 8 micrometer average size, and Large = 65 vol% quartz of 8 micrometer average size (of which only 75% were silane-treated). All specimens were light-cured (normal-cured; Triad II - 80 s). One set of each composite was further heat-cured at 120 degrees C for 10 min (heat-cured). A third set of the Hybrid was heat-cured with simultaneous light exposure (Elipar, Espe) for the first 3 min. RESULTS: By 30 d, normal-cured and heat-cured specimens showed significant (ANOVA/Tukey's test; p < or = 0.05) reductions in fracture toughness (avg. 16% and 22%, respectively), flexural modulus (avg. 11% and 11%, respectively) and flexural strength (avg. 25% and 29%, respectively). Further aging had little effect. The use of additional light-curing during heating did not affect the properties more than heat-curing alone. SIGNIFICANCE: The improvements in some of the properties of composites produced by heat-treating are of only short-term benefit, and are for the most part negated due to an alteration of the resin matrix as the composite equilibrates with water.

Reduction of polymerization contraction stress for dental composites by two-step light-activation.

OBJECTIVES: The goal of this study was to assess the reduction of polymerization contraction stress of composites during a two-step light-activation process and to relate this reduction to the process of polymerization shrinkage and specimen thickness. METHODS: Three test procedures were performed to compare two-step light-activation with delay with one-step continuous irradiation of composites: polymerization contraction stress using a closed-loop servohydraulic testing instrument, polymerization shrinkage by a mercury dilatometer, and degree of conversion by FTIR. For the one-step continuous curing method, the samples were light-activated for 60s at 330 mW/cm(2). For the two-step curing method, a 5s light exposure at 60 mW/cm(2) was followed by 2 min without light exposure, and then a second light exposure for 60s at 330 mW/cm(2). The same light parameters were used for measurements of stress, shrinkage, and degree of conversion. Three composites, Heliomolar, Herculite and Z100 were evaluated. The contraction stress experiments were repeated with varying thickness for Herculite using the one-step and two different two-step techniques. RESULTS: Polymerization contraction stress 10 min after light-activation was significantly reduced (P<0.05) by the two-step method: 29.7% for Heliomolar, 26.5% for Herculite, and 19.0% for Z100. Total volumetric shrinkage and degree of conversion were not significantly different for composites cured by the two different techniques. Increasing the thickness of the composite sample reduced the measured contraction stress, especially for one of the two-step curing methods. SIGNIFICANCE: A combination of low initial energy density followed by a lag period before a final high-intensity light irradiation provides a reduction of polymerization contraction stresses in dental composites. The stress reductions cannot be attributed to reductions in degree of conversion or unrestrained volumetric shrinkage.

Prevention of hypercalcaemic nephropathy and tissue calcification by glucagon during phosphate infusion.

Patients with serum calcium above 4.5 mmol/litre risk sudden death. Rehydration and frusemide may decrease calcium levels by 0.5-1 mmol/litre but result in a high renal filtered load of calcium which, if above 3.7 mmol/litre, causes calcium phosphate protein complexes to form giving rise to hypercalcaemic nephropathy. Current drugs namely clodronate, calcitonin and plicamycin take days to lower serum calcium and have disadvantages. Intravenous phosphate rapidly lowers serum calcium but when the calcium phosphate product rises above 4.6 mmol/litre the saturation point for the precipitation of calcium hydrogen phosphate is reached and tissue calcification occurs. Intravenous glucagon results in a steep reduction in serum phosphate within minutes and also lowers serum calcium, resulting in a marked fall in the calcium phosphate product to well below the critical level of 4.6 mmol/litre. If, in addition to glucagon, intravenous phosphate is now given, it should have a further calcium-lowering effect by inhibiting bone osteoclasts.

Assessing the effect of composite formulation on polymerization stress.

BACKGROUND: In this study, the authors measured the magnitude of the polymerization stress of a variety of dental composite materials and explored the effect of a novel monomer, a methacrylated derivative of styrene-allyl alcohol, or MSAA, in reducing polymerization stress. METHODS: Eleven commercially available composites and a series of experimental composites were evaluated in a mechanical testing machine to measure the maximum stress generated during placement in a confined setting. RESULTS: A significant relationship between higher filler volume and increased polymerization stress was found among the commercial materials. Introduction of MSAA produced a 30 percent reduction in polymerization stress in an experimental composite material. CONCLUSIONS: Composites that contain lower levels of inorganic filler particles are less likely to produce high levels of polymerization stress during placement. Modifications to traditional composite chemistry can result in materials that produce lower polymerization stress levels. CLINICAL IMPLICATIONS: The polymerization stress produced by dental composite materials during light-curing is a leading reason for bond failures in adhesive restorations, resulting in postoperative sensitivity, marginal staining and recurrent caries.