Indiana University-Purdue University Indianapolis (IUPUI) / If orthodontic direct bonding adhesives are to be successful, they must withstand the destructive influences of the oral environment and form a durable bond with enamel. Investigators have noted that moisture may be the greatest deterrent to an adhesive bond and water may have the ability to penetrate the adhesive-enamel interface, destroying this bond. An in vitro investigation was undertaken to determine whether moisture and other oral debris can penetrate this adhesive-enamel interface. Four commercially available orthodontic direct bonding systems were tested for microleakage using radioisotope45 calcium chloride (45Ca). Adhesives tested included Orthomite IIS, Directon, Unitek, and Genie. Polycarbonate brackets were bonded to freshly extracted human premolar teeth using the respective adhesive systems. Specimens were stored in 37.5°c water baths for periods of thirty days and ninety days before being tested. All specimens were thermal cycled 2500 cycles to provide a more heroic test. The thermal stressing was carried out at 15°c and 45°c with a 30 second dwell at each temperature. A total of eighty specimens were evaluated. The results of this study suggest that two of the orthodontic adhesives evaluated are susceptible to amounts of microleakage. Storage in water did affect the rate of leakage among the specimens. Generally, more specimens in the groups tested at ninety days showed leakage than at the thirty-day testing period. This study suggests that orthodontic adhesives may be susceptible to microleakage and that this may present problems clinically. However, long-term, well controlled investigations must be undertaken before more definite conclusions can be drawn concerning the effect on bond strength and enamel integrity.

Indiana University-Purdue University Indianapolis (IUPUI) / The present study was designed to test the tensile bond strength of two new bracket base designs and compare the results with those of the study by Higgins using Ormesh brackets. It was hypothesized that the visible increase in surface roughness of the two new bracket bases over the conventional (Ormesh) mesh would increase the tensile bond strength of the bracket. Sixteen DuraLingual mesh brackets and the acid-etched bracket bases were fabricated and bonded to human maxillary bicuspid teeth with a Bis-GMA compound adhesive as described by Higgins. After 24 hours, the bases were subjected to tensile bond strength testing until failure in tension and 10 brackets tested from each group were used to calculate the results. The following results were recorded: (1) The mean tensile bond strength of DuraLingual mesh and acid-etched bracket bases were significantly greater than the Ormesh wire mesh. (2) The mean tensile bond strength of the acid-etched base was significantly greater than the DuraLingual mesh. The visually apparent surface roughness and intricate microscopic voids and pits created by electrolytically-etching a smooth bracket base surface may have contributed to greater mechanical retention in this bracket compared to a smooth wire mesh bracket base (Ormesh) and a cast mesh (DuraLingual).

Thesis (M.S.)--University of Michigan, 1988.

Thesis (M.S.)--University of Michigan, 1981.

Thesis (M.S.)--University of Michigan, 1981.

Thesis (M.S.)--University of Michigan, 1988.

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Thesis (M.S.)--University of Michigan, Ann Arbor, 1989. / Includes bibliographical references (leaves 115-125). Also issued in print.

Thesis (M.S.)--University of Michigan, Ann Arbor, 1989. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 115-125).

Thesis (M.D.S.) -- University of Adelaide, Dept. of Dentistry, 1990. / Includes bibliographical references.