Effects of Water Sorption and Solubility on Degradation of Silorane and Methacrylate-Based Dental Composites.

INTRODUCTION: Wet oral environment may have deleterious effects on performance of the composites due to influences of water sorption and solubility. The study evaluated the hydrolytic degradation caused because of water sorption and solubility of silorane and methacrylate-based dental composites. METHODS: Ten disc samples (2 mm × 10 mm) were prepared. Samples were analyzed for water solubility and sorption according to ISO 4049:2000 regulations and tested for mass gain or loss following immersion in water or in artificial saliva at 1 day, 15 days, and 30 days period. Student's 't' test, repeated measures analysis of variance (ANOVA), and Tukey's post-hoc tests determined statistical significance of the experimental results with global significance set at P = 0.05. RESULTS: Considerable sorption and solubility was observed with time in both materials on immersion. Silorane composites showed lower water sorption and solubility than methacrylate-based composite (MBC). Artificial saliva demonstrated higher sorption and solubility compared to distilled water. CONCLUSION: Silorane composites display enhanced hydrolytic stability even after a month of immersion in contrast to conventional methacrylate-based composites (MBCs), making it a better alternative to MBC resins clinically.

Factors affecting outcome after the use of the Ponseti method for the management of idiopathic clubfoot, a retrospective study in an orthopaedic referral institute.

TIn the last few decades Ponseti method has replaced soft tissue releases as the gold standard in the management of idiopathic clubfoot. However, the recurrence of the deformity is common without post tenotomy bracing. The purpose of this study was to retrospectively see various attributes of the patients associated with poor outcome after use of Ponseti method in idiopathic clubfoot management. Seventy nine consecutive patients with one hundred and twenty three idiopathic clubfeet treated with Ponseti method by single orthopaedic surgeon were followed for a period of two years and recurrence of the deformity was studied in relation to age of patient at presentation (< 3 months or more), sex of the patient, severity of the deformity ( moderate to severe verses (Vs.) very severe), compliance to post tenotomy bracing (compliant Vs. non compliant), educational level of parents (high school or less) and access of parents to internet (Yes or No) and odds ratio for recurrence and level of significance determined for each using Fisher's exact t-test. Non compliance in seventeen patients (17.7%) with post tenotomy bracing was the most important factor related to the recurrence, with an odds ratio of 6.22 (P =0.0059). Educational level (less than high school) of parents (36.7%) was the second most important factor with odds ratio of 5.5 (P=0.0073). Fifteen patients with severe Demiglio scoring feet had an odds ratio of 5.3 (P= 0.0097) for the recurrence of the deformity. Inaccess of the parents to the internet had an odds ratio of 6.33 (P =0.011) for the recurrence of the deformity. Age and sex of the patients was not found to have a significant effect on the recurrence of the deformity. In conclusion, the risk factors associated with recurrence of the idiopathic clubfoot deformity except severity of the deformity are modifiable and extra minutes can be spent with risk group parents during follow up visits to prevent a recurrence by making them understand natural history of the corrected foot without post tenotomy bracing, encouraging them for regular follow up visits, arranging interactive sessions with other patients who are regular in their follow up and compliant with bracing, and encouraging the literate parents to update their information about clubfoot from internet.

Osteoprotective effect of propranolol in ovariectomized rats: a comparison with zoledronic acid and alfacalcidol.

BACKGROUND: Currently ß-adrenergic receptor blockers are considered to be potential drugs under investigation for preventive or therapeutic effect in osteoporosis. However, there is no published data showing the comparative study of ß-blockers with well accepted agents for the treatment of osteoporosis. To address this question, we compared the effects of propranolol with well accepted treatments like zoledronic acid and alfacalcidol in an animal model of postmenopausal osteoporosis. METHODS: Five days after ovariectomy, 36 ovariectomized (OVX) rats were divided into 6 equal groups, randomized to treatments zoledronic acid (100 µg/kg, intravenous single dose); alfacalcidol (0.5 µg/kg, oral gauge daily); propranolol (0.1 mg/kg, subcutaneously 5 days per week) for 12 weeks. Untreated OVX and sham OVX were used as controls. At the end of treatment serum calcium and alkaline phosphatase were assayed. Femurs were removed and tested for bone density, bone porosity, bone mechanical properties and trabecular micro-architecture. RESULTS: Propranolol showed a significant decrease in alkaline phosphatase levels and bone porosity in comparison to OVX control. Moreover, propranolol significantly improved bone density, bone mechanical properties and inhibited the deterioration of trabecular microarchitecture when compared with OVX control. The osteoprotective effect of propranolol was comparable with zoledronic acid and alfacalcidol. CONCLUSIONS: Based on this comparative study, the results strongly suggest that propranolol can be a candidate therapeutic drug for the management of postmenopausal osteoporosis.

Improvement in bone properties by using risedronate adsorbed hydroxyapatite novel nanoparticle based formulation in a rat model of osteoporosis.

A superior drug formulation capable of achieving efficient osteogenesis is in imperative demand for the treatment of osteoporosis. In the present study we investigated the potential of using novel risedronate-hydroxyapatite (HA) nanoparticle based formulation in an animal model of established osteoporosis. Nanoparticles of HA loaded with risedronate (NHLR) of various sizes (80-130 nm) were generated for bone targeted drug delivery. Three months after ovariectomy, 36 ovariectomized (OVX) rats were divided into 6 equal groups and treated with various doses of NHLR (500, 350 and 250 microg/kg intravenous single dose) and sodium risedronate (500 microg/kg, intravenous single dose). Untreated OVX and sham OVX served as controls. One month after drug administration, the left tibia and femur were tested for bone mechanical properties and histology, respectively. In the right femur, bone density was measured by method based on Archimedes principle and bone porosity analyses were performed using X-ray imaging. NHLR (250 microg/kg) showed a significant increase in bone density and reduced bone porosity when compared with OVX control. Moreover, NHLR (250 microg/kg) significantly increased bone mechanical properties and bone quality when compared with OVX control. The results strongly suggest that the NHLR, which is a novel nanoparticle based formulation, has a therapeutic advantage over risedronate sodium monotherapy for the treatment of osteoporosis in a rat model of postmenopausal osteoporosis.

Some studies on evaluation of degradation in composite adhesive joints using ultrasonic techniques.

Experimental and theoretical studies on degradation of composite-epoxy adhesive joints were carried out on samples having different interfacial and cohesive properties. Oblique incidence ultrasonic inspection of bonded joints revealed that degradation in the adhesive can be measured by significant variation in reflection amplitude as also by a shift in the minima of reflection spectrum. It was observed that severe degradation of the adhesive leads to failure dominated by interfacial mode. Through this investigation it is demonstrated that a correlation exists between the bond strength and a frequency shift in reflection minimum. The experimental data was validated using analytical models. Though both bulk adhesive degradation and interfacial degradation influences the shift in spectrum minimum, the contribution of the latter was found to be significant. An inversion algorithm was used to determine the interfacial transverse stiffness using the experimental oblique reflection spectrum. The spectrum shift was found to depend on the value of interfacial transverse stiffness using which a qualitative assessment can be made on the integrity of the joint.

Acoustic emission source location in composite structure by Voronoi construction using geodesic curve evolution.

Conventional analytical/numerical methods employing triangulation technique are suitable for locating acoustic emission (AE) source in a planar structure without structural discontinuities. But these methods cannot be extended to structures with complicated geometry, and, also, the problem gets compounded if the material of the structure is anisotropic warranting complex analytical velocity models. A geodesic approach using Voronoi construction is proposed in this work to locate the AE source in a composite structure. The approach is based on the fact that the wave takes minimum energy path to travel from the source to any other point in the connected domain. The geodesics are computed on the meshed surface of the structure using graph theory based on Dijkstra's algorithm. By propagating the waves in reverse virtually from these sensors along the geodesic path and by locating the first intersection point of these waves, one can get the AE source location. In this work, the geodesic approach is shown more suitable for a practicable source location solution in a composite structure with arbitrary surface containing finite discontinuities. Experiments have been conducted on composite plate specimens of simple and complex geometry to validate this method.

Time reversal technique for health monitoring of metallic structure using Lamb waves.

Time reversal active sensing using Lamb waves is investigated for health monitoring of a metallic structure. Experiments were conducted on an aluminum plate to study the time reversal behavior of A(0) and S(0) Lamb wave modes under narrow band and broad band pulse excitation. Damage in the form of a notch was introduced in the plate to study the changes in the characteristics of the time reversed Lamb wave modes experimentally. Time-frequency analysis of the time reversed signal was carried out to extract the damage information. A measure of damage based on wavelet transform was derived to quantify the hidden damage information in the time reversed signal. It has been shown that time reversal can be used to achieve temporal recompression of Lamb waves under broadband signal excitation. Further, the broad band excitation can also improve the resolution of the technique in detecting closely located defects. This is demonstrated by picking up the reflection of waves from the edge of the plate, from a defect close to the edge of the plate and from defects located near to each other. This study shows the effectiveness of Lamb wave time reversal for temporal recompression of dispersive Lamb waves for damage detection in health monitoring applications.

Body fat and lean body mass assessment in human subjects--a comparison of two different techniques.

Body fat and lean body mass was assessed in young college students by two different techniques involving NIR method and body circumference measurements. NIR technique significantly over-estimated the body fat as compared to the results obtained by the other method. The difference between the methods was 23-30% high for fat and the variation was 5-9% low for lean body mass for the whole group. Results obtained by the body girth size measurements agreed well with fat and lean body mass values from other studies on Indian subjects which had employed different methods.

Effect of ammonia, urea and diammonium phosphate (DAP) on lung functions in fertilizer plant workers.

A spirometric study (FVC, FEV1 & PEFR/Min) was carried out in workers exposed to fertilizer chemicals (91) as a whole, out of which 31 were Ammonia, 30 Urea and 30 DAP plant workers, and 68 were controls belonging to the same age, sex, body surface area and socio-economic status. This study showed significant reduction in both PEFR/min and FEV1, the reduction being more in PEFR/Min., seems to indicate obstructive type of lung changes affecting the larger air-ways first, followed by bronchospasm. But FVC showed a significant reduction only after more than 10 years of exposure, probably causing restrictive changes only after prolonged exposure. Out of the 3 chemicals, DAP affected all the 3 parameters most, followed by Ammonia and Urea affected the least.

A comparative study of lung functions in rice mill and saw mill workers.

A lung function study was carried out to determine the relative effect of rice husk and saw dust on mill workers. The study consisted of 195 subjects of which 56 rice mill workers, 71 saw mill workers and 68 controls of similar age, sex and socio-economic condition. FVC was significantly reduced in saw-mill workers compared to both the controls and rice mill workers. Both FEV1 and PEFR/min were significantly reduced in both mill workers compared to controls. The fall in PEFR/min in saw mill workers was also significant when compared to rice mill workers. FVC was reduced after 5 years of exposure only in saw mill workers. FEV1 was reduced within a year which was further reduced after 5 years in both mill workers. PEFR/min was highly reduced within a year remained so even after 5 years.