Utilization of bio-waste cotton (Gossypium hirsutum L.) stalks and underutilized paulownia (paulownia fortunie) in wood-based composite particleboard

The objective of this study was to investigate some mechanical (modulus of rupture, modulus of elasticity and internal bond) and physical (thickness swelling and water absorption) properties of wood-based three-layer particleboard containing different cotton (Gossypium hirsutum L.) stalks and underutilized paulownia (paulownia fortunie) wood particle ratios (30, 50 and 70%) using urea formaldehyde resin. Addition of cotton stalk and paulownia wood in particleboard improved mechanical properties of resulting composites boards significantly. However, the water resistance decreased with increasing cotton stalk and paulownia wood particle contents. The highest mechanical properties were obtained at cotton stalk and paulownia wood particle loading of 50 and 70%, respectively. Conclusively, valuable underutilized natural resources, cotton stalk and paulownia wood can be used with the mixture of industrial wood particles in the production of particleboards with high mechanical properties.Keywords: Wood, resin, urea-formaldehyde, mechanical properties, physical propertie

Identification and Evaluation of Oncoming Changes of Wood and Paper Industries of the Country

Studying and rating of oncoming challenges of the wood and paper industries of the country can create a delicate attitude for policy makers and investors of these valuable industries. This study by the aim of identification and evaluation of wood and paper industries challenges with scientific and authentic method of likert spectra scale was done is 2010. Present challenges of wood and paper industries were detected by literature review and consulting with experts and academician and a number of manufacturing unites of wood and paper industries and query was designed. Intended data and statistics obtained from experts of wood and paper industries were compared and analyzed by likert scale spectra. The results showed that of 24 examined challenges, shortage of raw material, lake of long, compressive and applied prospective, existence of great gap between the university and industrial units and wearied and aged machinery are among the most important. Finally the identified challenges were submitted to the authorities for helping the economy of the country as well as causing the prosperity and budding of these industries

Awareness of Orthodontic Treatments among School Teachers of Two Cities in Iran

Background and aims. Since most orthodontic patients are children and adolescents, it is believed that teachers can help find these patients and make them aware of their orthodontic problems. Therefore, teachers are expected to have proper knowledge about these problems. The aim of this study was to determine teachers’ awareness about orthodontic treatments in Tabriz and Saqqez and compare it in different educational levels. Materials and methods. A questionnaire was given to 384 teachers (204 in Tabriz and 180 in Saqqez) in randomly selected schools of different levels. The questionnaire had 17 questions in 3 sections, including general information, age, and costs of orthodontic treatments. The teachers’ awareness in two cities was analyzed with independent t-test and in educational levels with one-way ANOVA. Results. About 94% of the participants believed orthodontic treatment consisted of arrangement of teeth with special braces. However, there was no significant difference between the two cities in general information (p=0.23) and the age suitable for orthodontic treatment (p=0.53). The differences in the teachers’ awareness in three educational levels were not statistically significant between the two cities (p=0.23). Conclusion. Awareness of teachers about orthodontic treatment in Saqqez and Tabriz was not sufficient and different; 75% of the participants believed that high cost of orthodontic treatment is the main problem

Comparison of the effect of hydrogel and solution forms of sodium ascorbate on orthodontic bracket-enamel shear bond strength immediately after bleaching: An <i>in vitro </i>study

<b>Aim:</b> This study compared the effects of hydrogel and solution forms of sodium ascorbate (SA) with two different application times on bracket bond strength subsequent to bleaching. <b> Materials and Methods:</b> A total of 72 sound premolars were randomly divided into six groups (n = 12): An unbleached control group (group one) and five experimental groups of carbamide peroxide. Specimens in group two were bonded immediately after bleaching; specimens in groups three and four were bleached, then treated with SA solution for ten minutes and three hours, respectively, and then bonded. In groups five and six, SA hydrogel was used and the specimens were prepared similar to groups three and four, respectively. Following debonding, bond strengths were recorded in MPa. To evaluate the amount of resin left on the enamel surfaces, adhesive remnant index (ARI) scores were used. <b> Statistical Analysis:</b> The bond strength data were analyzed with ANOVA and pairwise comparisons were made by Tukey test. The ARI data were subjected to Kruskal-Wallis test and two-by-two comparisons were made by the Mann-Whitney U test. <b> Results:</b> There were significant differences in bond strengths between the groups (<i> P</i> &lt; 0.0005). However, the differences between groups three, four, five and six were not significant. Furthermore, there were no significant differences between group one and groups four and six, whereas the differences between the other groups were significant (<i> P</i> &lt; 0.05). Regarding ARI, there were significant differences among the groups (<i> P</i> = 0.004). <b>Conclusion:</b> Bleaching significantly decreased the bracket bond strength. Compromised bonding was reversed with a three-hour application of both forms of SA