published_or_final_version / Dentistry / Master / Master of Dental Surgery

Dissertation submitted in compliance with the requirements for the Master's Diploma in Technology: Dental Technology, Technikon Natal, 1993. / The unpredictability of solder joints in dental base metal alloys constitute a major problem. This study aimed to establish whether gold plating the joint surfaces of a metal ceramic base metal alloy prior to postceramic soldering would enhance the predictability of the soldering method and joint strength. 150 standardised test specimens were prepared from 3 Oegussa dental alloys, viz Resistal P (Nier), Oegulor M (AUPt) and Realor (PdAU). The Resistal P specimens were subjected to 6 porcelain firing cycles and solder joint surfaces of 40 specimens gold plated prior to soldering, using gold plating equipment and solutions found in the jewellery industry. suitable fluxes were used and all soldering was done in a porcelain furnace. First the soldering method was validated by soldering 20 oegulor M specimens and determining the tensile strength of the 10 joints in an Instron testing machine. The data were then compared with the ISO minimum standards. The soldering method proved sound and a control was thus established. secondly, using 3 alloy combinations without gold plating, 30 solder joints were made and their tensile strengths determined. This established the level of predictability and strength and parameters for comparison. Thirdly, the above procedure was repeated, but the Resistal P specimen joint surfaces were gold plated prior to investing for soldering. The levels of predictability and strength were then compared with the parameters set. The fracture sites of broken joints were examined and photographed using a metallurgical microscope. The data were analysed using 4 statistical tests. The Oegulor M control group solder joints were the strongest and the Resistal P joints the weakest. The success rates for the non-plated joints were; oegulor M to oegulor M = 100%, Resistal P to oegulor M = 90%, Resistal P to Realor = 80% and Resistal P to Resistal P = 60%. The success rates for the gold plated joints were; Resistal P to oegulor M = 60%, Resistal P to Realor = 40% and Resistal P to Resistal P = 80%. This study found, under the circumstances of testing, that gold plating of the base metal alloy prior to investing for postceramic soldering did not enhance the strength, solderability and predictability of the solder joints to an extent that a flux that does not discolour porcelain can be used. / M

MSc (Dentistry), Faculty of Health Sciences, University of the Witwatersrand, 2009 / Problem. One of the sources of inaccuracy in utilising the CEREC Chairside CAD/CAM system has been the difficulty of accurately positioning the intraoral camera relative to the path of insertion of the preparation and restoration. The degree of inaccuracy produced by variations in the angulation of the camera relative to the path of insertion is not known. Purpose. The purpose of this study was to first review the literature and history of CAD/CAM in dentistry, and the CEREC Chairside System in particular, and then to determine the errors that may result from changes in angulation of the camera in three dimensions. Further, to design a device which would help stabilise the camera to eliminate such errors. Method and Materials. A prefabricated Aesthetic Base Gold (ABG) Model was used and mounted on an articulator in order to simulate changes in angulation of each of the three dimensional axes which cause variations in roll, pitch, and yaw in the positioning of the camera. Images were captured for angle variations of 0°, 1°; 3°, 5°, 10°, 15° and 20° using the CEREC software on a crown preparation for tooth 24. The same software was used to make measurements on the resulting images to determine the mesio-distal, bucco-lingual orientation and the occlusal, internal shoulder and external shoulder dimensions. In addition, a quality assessment was carried out to observe any shadows, surface texture changes, margin discrepancies and ability to automatically complete the restoration with ease and accuracy. An intraoral stabilising device was designed that could be placed intraorally using polyvinyl siloxane putty. The ABG model was positioned to simulate quadrants 2 and 4 on crown iv preparation for tooth 24. Time to set up and place the device was recorded, and a Visual Analogue Scale was used to determine ease of use. Results. Difficulties were encountered in measurements of images where there was an angle deviation of greater than 5º, and so it was only possible to analyse the four angles of 0, 1, 3, and 5º. A three-way ANOVA revealed expected significant differences between the different measurements (as they are measuring different things) but there were no other significant differences. Thus neither the four different angles nor the three different axes had any influence on the readings. There was also consistency across the measurements, for every combination of the levels of the three factors (angle, measurement and axis). The stabilising device proved quick and easy to set up and place the silicone putty (less than 20 seconds) and the average VAS score for using the device improved by 25.3% when using the device in the lower, and by 36.4% when using the device in the upper arch. Conclusions. The angle of the camera relative to the path of insertion of the restoration should not exceed 3° for changes in Pitch, or 5° for changes in Roll and Yaw of the camera. The stability device designed during this study proved to be more convenient and accurate for data capture as it decreased the time of search and reduced both the internal and external factors which interfere with data capture.

Thesis (Ph. D., Education)--University of Idaho, April 2009. / Major professor: Roger L. Scott. Includes bibliographical references (leaves 286-299). Also available online (PDF file) by subscription or by purchasing the individual file.

Thesis (Odontologie Doktorsgrad)--Tandläkarhögskolan i Stockholm, 1951. / Includes bibliographical references (p. 248-249).

published_or_final_version / Endodontics / Master / Master of Dental Surgery

published_or_final_version / Paediatric Dentistry / Master / Master of Dental Surgery

<p>The purpose of this research project was to assess the safety and efficacy of a combination of drugs for conscious sedation in patients undergoing office-based plastic and reconstructive surgery. A pilot study was done to determine the safety of the co-administration of the drugs used in the sedation technique.</p>

<p>The purpose of this research project was to assess the safety and efficacy of a combination of drugs for conscious sedation in patients undergoing office-based plastic and reconstructive surgery. A pilot study was done to determine the safety of the co-administration of the drugs used in the sedation technique.</p>

Thesis (Ph. D.)--University of Adelaide, Dept. of Chemical Engineering, Materials Engineering Group, 1992. / Includes bibliographical references (leaves 290-294).