Thesis (M. Sc.)--University of Toronto, 1998. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M. Sc.)--University of Toronto, 1998. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Foundries today use temporary molds made from silica sand with a resin bonding agent to hold a form until the metal is poured. With the aid of computer simulations, the molds are designed to produce good castings with minimal pattern iterations by calculating cooling and porosity. Stress analysis simulations are being developed using the current software, but the known mechanical properties for the sand mold are minimal and incomplete. This study measures the elastic modulus of bonded sand as a function of temperature to obtain baseline data for the model. Following ASTM standards, a three point bend test is used to measure the elastic modulus of chemically bonded sand as a function of temperature to better understand the complex nature of the mold as it undergoes heating and cooling. Multiple measurements of the elastic modulus of PUNB bonded silica sand are performed from room temperature to 500°C in a nitrogen atmosphere to capture the changes in the elastic modulus under heating. It is found that for an intermediate heating rate of 8°C/min, the elastic modulus decreases steeply from a room temperature value of about 3,600 MPa to 600 MPa at 125°C. Between 125°C and 250°C, the elastic modulus is relatively constant. Above 250°C, it increases to 1,200 MPa at 280°C and then decreases again to 800 MPa at 350°C. Above 350°C, the elastic modulus increases linearly with temperature until it reaches 2,200 MPa at 500°C. At approximately 500°C, the strength of the bonded sand vanishes. At a given temperature above 125°C, the elastic modulus can vary by more than a factor of two depending on the heating rate. Furthermore, the elastic modulus agrees with previous steady state temperature measurement literature when specimens are held at a constant temperature until the elastic modulus reach steady. It is also found that the addition of black iron oxide has no effect on the elastic modulus, whereas solvent removal before a test increases the stiffness of the bonded sand at temperatures below 150°C.

Thesis (M.S.)--University of Michigan, 2003. / Includes bibliographical references.

ABSTRACT De-bonding is the most common failure of resin-bonded fixed partial dentures. The aim was to determine if the shear bond strength (SBS) differed between a dental adhesive and a Co-Cr alloy and an yttria-stabilized zirconia (Y-TZP). Furthermore, to determine whether retention holes in the two materials and storage for 21 days in water affected the results. The hypothesis was that there are no significant differences between the compared groups. 10 embedded discs of Co-Cr alloy without and 10 with retentive holes, and 10 discs of Y-TZP without and 17 with retentive holes were sand- and steam blasted. A pillar of adhesive cement was bonded to the surface of the discs and stored in water at 37 °C for 24 hr and / or 21 days. An UltraTest machine with a crosshead speed of 1 mm/ min was used for SBS. The mean SBS after 24 hr / 21 days in water were recorded. The SBS of Co-Cr alloy without retentive hole was 16.3 MPa after 24 hr and 11.4 MPa after 21 days, the SBS of Y-TZP without retentive hole was 18.5 MPa after 24 hr and 12.6 MPa after 21 days. The SBS of Co-Cr alloy with retentive hole 13.9 MPa after 21 days and Y-TZP with retentive hole 16.9 MPa after 21 days. No statistically significant differences were found between the groups with or without retentive holes and after 24 hr or 21 days in water, p> 0.05.

No description available.

No description available.

L’objectif de cette étude était d’évaluer et de comparer la force d’adhésion de deux résines de collage: le ClearfilTM Esthetic Cement & DC Bond Kit (C) et le RelyXTM Unicem (R), sur trois adhérents différents : une surface d’émail, un alliage de métaux non précieux (Np) et un alliage de métaux semi-précieux (Sp). La surface des échantillons des alliages métalliques a subi différents traitements de surface. Sur l’émail (n=15) ainsi que sur les plaquettes d’alliages Np et Sp (n=15), des cylindres de résine étaient appliqués et polymérisés. Suite au processus de collage, les échantillons ont été incubés à 37°C pendant 24 heures, puis ont subi 500 cycles de thermocyclage. Des tests de cisaillement ont été effectués, suivi par l’analyse de la surface des échantillons au microscope à balayage électronique. Une comparaison de type T-test et des comparaisons multiples post hoc, ont été effectuées pour l’analyse statistique (p 0,05). Sur l’émail, les résultats ont démontré que la résine C présentait une force d'adhésion moyenne statistiquement supérieure (33,97±17,18 MPa) à la résine R (10,48±11,23 MPa) (p 0,05). Le type d’alliage utilisé n’influençait pas la force d’adhésion, et ce, peu importe le type de résine de collage (p>0,05). Pour le groupe Sp, la résine C a démontré une adhésion statistiquement supérieure à la résine R, et ce, pour tous les traitements de surface (p 0,05). En conclusion, la résine C a démontré des résultats d’adhésion significativement supérieurs à la résine R sur l’émail ainsi que sur presque toutes les surfaces traitées des alliages de métaux. / The objective of this study was to assess and compare the shear bond strength of two types of resin cements: ClearfilTM Esthetic Cement & DC Bond Kit (C) and RelyXTM Unicem (R) when these resins cements were applied to three different surfaces: enamel, non precious metal alloy (Np) and semi-precious metal alloy (Sp). Both types of alloy surfaces were treated differently. On both enamel (n=15) and alloy plates Np and Sp (n=15) surfaces, cylinder shaped resin cements were bonded and lightpolymerized. After the adhesion process, all samples were placed into an incubator at 37°C for 24 hours and 500 thermal cycles were accomplished. Shear bond strength tests followed by electron microscopy analysis were performed. Statistical analysis was done using a T-test comparison followed by a post hoc multiple comparisons (p 0.05). The results on enamel showed that the C resin cement had a statistically significant higher bond strength (33.97±17.18 MPa) than the R resin cement (10.48±11.23 MPa) (p 0.05). The type of alloy did not influence the bond strength regardless the type of resin cement (p 0.05). For the Sp group, the bond strength was statistically higher for the C resin than for the R resin and those results are valuable for all treated surfaces (p 0.05). To conclude, the C resin cement showed a statistically significant higher bond strength than the R resin cement with enamel and most of the metal alloy treated.

L’objectif de cette étude était d’évaluer et de comparer la force d’adhésion de deux résines de collage: le ClearfilTM Esthetic Cement & DC Bond Kit (C) et le RelyXTM Unicem (R), sur trois adhérents différents : une surface d’émail, un alliage de métaux non précieux (Np) et un alliage de métaux semi-précieux (Sp). La surface des échantillons des alliages métalliques a subi différents traitements de surface. Sur l’émail (n=15) ainsi que sur les plaquettes d’alliages Np et Sp (n=15), des cylindres de résine étaient appliqués et polymérisés. Suite au processus de collage, les échantillons ont été incubés à 37°C pendant 24 heures, puis ont subi 500 cycles de thermocyclage. Des tests de cisaillement ont été effectués, suivi par l’analyse de la surface des échantillons au microscope à balayage électronique. Une comparaison de type T-test et des comparaisons multiples post hoc, ont été effectuées pour l’analyse statistique (p 0,05). Sur l’émail, les résultats ont démontré que la résine C présentait une force d'adhésion moyenne statistiquement supérieure (33,97±17,18 MPa) à la résine R (10,48±11,23 MPa) (p 0,05). Le type d’alliage utilisé n’influençait pas la force d’adhésion, et ce, peu importe le type de résine de collage (p>0,05). Pour le groupe Sp, la résine C a démontré une adhésion statistiquement supérieure à la résine R, et ce, pour tous les traitements de surface (p 0,05). En conclusion, la résine C a démontré des résultats d’adhésion significativement supérieurs à la résine R sur l’émail ainsi que sur presque toutes les surfaces traitées des alliages de métaux. / The objective of this study was to assess and compare the shear bond strength of two types of resin cements: ClearfilTM Esthetic Cement & DC Bond Kit (C) and RelyXTM Unicem (R) when these resins cements were applied to three different surfaces: enamel, non precious metal alloy (Np) and semi-precious metal alloy (Sp). Both types of alloy surfaces were treated differently. On both enamel (n=15) and alloy plates Np and Sp (n=15) surfaces, cylinder shaped resin cements were bonded and lightpolymerized. After the adhesion process, all samples were placed into an incubator at 37°C for 24 hours and 500 thermal cycles were accomplished. Shear bond strength tests followed by electron microscopy analysis were performed. Statistical analysis was done using a T-test comparison followed by a post hoc multiple comparisons (p 0.05). The results on enamel showed that the C resin cement had a statistically significant higher bond strength (33.97±17.18 MPa) than the R resin cement (10.48±11.23 MPa) (p 0.05). The type of alloy did not influence the bond strength regardless the type of resin cement (p 0.05). For the Sp group, the bond strength was statistically higher for the C resin than for the R resin and those results are valuable for all treated surfaces (p 0.05). To conclude, the C resin cement showed a statistically significant higher bond strength than the R resin cement with enamel and most of the metal alloy treated.