Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

Thesis (M.S.)--Oregon State University, 1986. / Typescript (photocopy). Includes bibliographical references (leaves 78-82). Also available on the World Wide Web.

Three particle boards, one flake board, one multi-layer board, and a plywood panel, all of 3/8-inch thickness, were overlaid with 1/20-inch Philippine mahogany veneer, using a urea-formaldehyde adhesive. Both non-overlaid and overlaid boards were subjected to physical and mechanical tests involving the glue line and the boards themselves. Results of the glue-line shear test indicated that glue-line failure between the veneer and the boards only occurred in the boards of higher density. Overlaying the boards decreased dimensional change in a plane parallel to the length of the board but slightly increased it parallel to the width of the board. Boards composed of flakes had better strength properties than those composed of particles. No delamination of the board occurred during accelerated aging; however, deterioration in the board core was extensive. In general, overlaying the boards tended to minimize differences in strength properties between boards, and improved the strength properties so as to be almost comparable to those of plywood. Overlaying decreased warping in the boards. Some physical properties of the boards, such as resistance to warping and face-checking, were more satisfactory than those of plywood. / Forestry, Faculty of / Graduate

Thesis (M.S.)--University of Michigan, 2001. / Includes bibliographical references.

Thesis (Ph.D.) - University of Queensland, 2002. / Includes bibliography.

The gluing properties of plantation-grown gmelina wood (Gmelina arborea Roxb.) from Nigeria were investigated. Three wood peeling temperatures - 20°C, 50°C and 85°C; two glue types - urea-formaldehyde (UF) and phenol-formaldehyde (PF); two glue spreads - 25 kg/MDGL (55 lb) and 32 kg/MDGL (70 lb); and two closed assembly times - 10 minutes and 20 minutes were used. Veneers from the sample logs were peeled tight and were 1.27 mm (0.05 in) thick. The specific gravity for the logs was determined and its influence on the probable end uses of gmelina plywood discussed. Three 5-ply plywood panels were made, for each treatment combination for 72 in all. A total of 1438 shear test specimens were used. The UF specimens were tested dry and after vacuum-pressure treatment whereas the PF specimens received vacuum-pressure and boil-dry-boil tests. Bond quality was evaluated on the basis of wood shear strength and percentage wood failure. Results were compared to the U.S., British and German Plywood Standards. Wood peeling temperature was highly significant regardless of glue type and bond quality testing method. Heating of gmelina logs prior to peeling did not improve veneer peel-quality. Veneers were of the highest peel-quality (basis: Thickness variation and surface roughness) when logs were peeled at 20°C. The highest peeling temperature yielded the lowest peel-quality. Bond quality, (percentage wood failure), was consistently reduced by increasing peeling temperature and was lowest at 85°C in all the UF and PF treatments, regardless of bond quality testing method. Ignoring glue spreads, panels made from veneers cut at temperatures of 50°C and 85°C gave the highest shear strength values among the UF treatments. On the other hand, panels from veneers cut at temperatures of 20°C and 85°C gave the highest shear strength values among the PF treatments. All factors considered, treatment combination of Spread 55 - Time 20, arising from veneers cut at the control temperature of 20°C, gave an impressive bond quality in all the UF and PF treatments used. Five of the 12 PF treatments used, regardless of type of bond quality testing method, pass the U.S. Plywood Standard; one passes the British Standard; while all pass the German Standard. On the other hand, five of the 12 UF treatments from vacuum-pressure test pass the U.S. Standard; two pass the British Standard; while all pass the German Standard. Furthermore, all the 12 UF treatments from dry test pass the U.S. Standard; six pass the British Standard; while all pass the German Standard. From the results obtained, plantation-grown Gmelina arborea wood from Nigeria, with a specific gravity of 0.41 ± 0.027 (as determined), was found suitable for use as construction plywood, core and crossband veneer for decorative panel as well as container veneer and plywood. The dominant factor accounting for the general trend of low percentage wood failure was attributed to veneer surface inactivation, resulting from surface aging of veneers. / Forestry, Faculty of / Graduate

OBJECTIVES: To evaluate the marginal chipping of anterior veneers made with CAD/CAM by calculating the chipping factor, to evaluate the failure load of different veneering materials and thicknesses under static loading and cyclic loading. MATERIALS AND METHODS: An ivorine central incisor was prepared to receive a traditional veneer. Using epoxy resin, 120 replication dies were made of the prepared tooth. Four ceramic materials were used; IPS Empress CAD, IPS e.max CAD, VITA ENAMIC and Lava Ultimate. Veneers were milled using a Sirona InLab MCXL at three different thicknesses, 0.4mm, 0.7mm and 1.0mm, n=10 for each group. Veneers were inspected under the light microscope to calculate the chipping factor (CF). All veneers were cemented to their tooth replicas using Variolink Veneer resin cement. Five specimens/group were loaded under compression using an Instron universal testing machine at a rate of 0.5 mm/minute until fracture. Another five specimens were subjected to cyclic loading at 30% of the mean fracture load for 30,000 cycles at frequency rate of 1 Hz, and then were loaded under compression to fracture. Modes of failure were recorded after each test. RESULTS: IPS Empress CAD 0.4mm CF was higher than all other groups, and VITA ENAMIC and Lava Ultimate 1.0mm CF were the lowest. There was a significant difference in the failure load of the IPS Empress CAD and IPS e.max CAD groups under static loading but not in VITA EANMIC and Lava Ultimate groups. Cyclic fatigue had no significant effect on the failure load of different veneering materials and thicknesses. CONCLUSIONS: Chipping factor decreases as the material thickness increases and can be used as an indicator of material machinability. IPS e.max CAD at 1.0mm had the highest static failure load value when compared to other materials. Cyclic fatigue did not affect the failure load values within the groups tested. / 2019-09-26T00:00:00Z

Graduation date: 1966

Thesis (M.E.F.E.)--University of Canterbury, 2006. / Typescript (photocopy). "January 2006." Includes bibliographical references (leaves 99-101).

O objetivo deste trabalho foi avaliar, in vitro, a influência de diferentes preparos dentais e dois diferentes tipos de cerâmica, sobre a resistência à fratura e o vedamento marginal de dentes restaurados com facetas laminadas. Foram utilizados 56 incisivos centrais, divididos em 7 grupos (incluindo grupo controle de dentes hígidos), diferenciados pelo preparo: preparos tipo janela, preparos com término em bordo reto e preparos com término em bordo envelopado e cerâmica utilizada: feldspática (Vita VM7 – Vita) e à base de dissilicato de lítio (IPS Empress II – Ivoclar Vivadent). Os dentes foram preparados com pontas diamantadas de forma padronizada, conforme os grupos acima, após foram moldados com silicona de adição para confecção dos laminados com os materiais citados. Após a cimentação dos laminados com cimento resinoso, os espécimes foram termociclados e moldados novamente para obtenção de réplicas em resina epóxi que foram avaliadas quanto à presença de fenda marginal em microscopia eletrônica de varredura (MEV). Os espécimes (dentes restaurados) foram submetidos ao teste de resistência à fratura em máquina de ensaio universal com velocidade de 1 mm/min. Os resultados foram tabulados e analisados estatisticamente pelos testes ANOVA e Qui², com nível de significância de 5%. O grupo controle apresentou a maior resistência à fratura. A resistência dos dentes restaurados com laminados foi influenciada significativamente pelo tipo de preparo (p=0,03) e pelo tipo de cerâmica (p=0,011) empregados. Quando comparados os dois tipos de cerâmica empregados, o desempenho superior foi para o sistema cerâmico à base de dissilicato de lítio, quando da presença de bordos reto e envelope. Com relação aos preparos, houve diferença para as cerâmicas feldspáticas, sendo superior o preparo janela. Para a avaliação de vedamento marginal, os grupos com preparo em bordo reto e envelopado associados à cerâmica à base de dissilicato de lítio não apresentaram fendas marginais. Porém, o grupo com preparo do tipo janela e cerâmica à base de dissilicato de lítio e o grupo com preparo em bordo reto e cerâmica feldspática apresentaram 75% de fendas presentes. Conclui-se que quando a cerâmica utilizada for feldspática, o preparo janela apresentou melhor resistência à fratura. Por outro lado, se a cerâmica utilizada for à base de dissilicato de lítio, o tipo de preparo não influenciou na resistência. Os laminados confeccionados com a cerâmica à base de dissilicato de lítio associados ao tipo de preparo reto ou envelopado apresentaram ausência de fenda (100%) e melhores resultados em relação à resistência à fratura para estes tipos de preparo. / The aim of this study was to evaluate in vitro the influence of different dental tooth preparations and two different types of ceramics on the fracture resistance and marginal sealing of teeth restored with veneers. 56 central incisors were divided into 7 groups (including the control group of sound teeth), by preparation: according to window, ending in straight edge and ending in overlap and ceramic used: feldspathic (Vita VM7 – Vita) and lithium disilicate (IPS Empress II – Ivoclar Vivadent). Teeth were prepared with diamond burs in a standardized manner, according above groups and were impressed with vinyl polysiloxane for the fabrication of veneers with the materials cited. After cementation of veneers with resin cement, specimens were thermocycled and molded again to obtain replicas in epoxy resin that were evaluated for the presence of marginal gap in scanning electron microscopy (SEM). The specimens (restored teeth) were tested for resistance to fracture in a universal testing machine with a crosshead speed of 1 mm / min. The results were statistically analyzed by ANOVA and Chi square test, with a significance level of 5%. The control group showed the highest fracture resistance. Restored teeth resistance was significantly influenced by the type of preparation (p = 0.03) and the ceramic type (p = 0.011). When comparing the two ceramic types, the superior performance was optained with lithium disilicate ceramic, associated with straight edges and overlap preparations. Regarding preparations showed differences within the feldspathic ceramics, being higher for the window preparation. Regarding marginal sealing, groups with board preparation in straight and overlap associated with lithium disilicate ceramic showed no marginal gaps. However, the group with window preparation and lithium disilicate ceramic and group preparation on board straight and feldspathic ceramic showed 75% of gap presence. It is concluded that when the ceramic used was felsdpathic the window preparation showed better fracture resistance. On the other hand, if the ceramic used was lithium disilicate, the type of preparation didn’t influence the fracture resistance. Laminates made with lithium disilicate ceramic associated with in straight or overlap preparation showed no gap formation (100%), presented the best results in relation to fracture resistance.