Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references (leaves 69-73). Also available in electronic version.

Thesis (Ph. D.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (month day, year) Vita. Includes bibliographical references.

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Thesis submitted in fulfilment of the requirements for the degree Master of Technology: Dental Technology in the Faculty of Health and Wellness Sciences at the Cape Peninsula University of Technology 2014 / A pure nylon denture base does not bond chemically to the acrylic teeth processed into the denture. A mechanical bond is created by boring retention holes (diatorics) into the tooth structure. Concerns are that this form of retention might be insufficient. The purpose of this study is, firstly, to compare the retention of acrylic denture teeth in pure nylon dentures with that of teeth in conventional acrylic denture bases (the acrylic test pieces serving as the control standard), and secondly, to explore whether the technique prescribed for creating diatorics in acrylic teeth for use with pure nylon denture bases potentially has a weakening effect on the acrylic tooth structure. Two sets of 26 identical anterior one-tooth test pieces were created. The first set, labelled N, comprises two different pure nylon denture base materials labelled N1 and N2 – all have diatorics in the acrylic teeth. The second set, labelled A, comprised the same acrylic denture base. The set labelled A1 is the control standard without diatorics in the acrylic teeth and the set labelled A2 has diatorics within the acrylic teeth. A compressive load was applied to these test pieces at an angle of 45 degrees on the palatal surface of the tooth until fracture occurred or maximum load was reached. Resulting data from the first part of the research was analysed by One-Way ANOVA analysis. Resulting data for the second part of the research was analysed via the Chi-square cross- tabulation method. The One-Way ANOVA test revealed that there is no statistical difference in the mean fracture or maximum load in Newton values between the two A (acrylic denture base) groups. There is also no statistical difference in the mean fracture or maximum load in Newton values between the two N (pure nylon denture base) groups. There is, however, a statistically significant difference in the mean fracture or maximum load in Newton values of Group A in comparison to Group N. The Chi-square cross-tabulation indicated that the A groups have very similar breakage patterns, and the N groups have similar breakage patterns respectively. It is concluded that the mechanical retention of acrylic denture teeth in pure nylon denture bases is weaker than the mechanical and chemical retention of acrylic denture teeth in acrylic denture bases. It is also concluded that when diatorics are created as prescribed within the tooth, these do not weaken the tooth structure.

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Magister Scientiae Dentium - MSc(Dent) / Both light-cured (LC) and chemically-cured (CC) acrylic resin custom tray materials are used at the Oral Health Centre, Faculty of Dentistry, University of the Western Cape. At present, the CC acrylic is the standard for formal undergraduate teaching and training. The LC material is not part of routine didactic teaching as little evidence-based scientific information is available with regards to its properties and its usage in the clinical environment. Negative effects have caused researchers to focus on alternatives and to research for other materials with more advantageous properties. The objectives of this study was to determine the linear dimensional shrinkage and fracture toughness of light-cured acrylic custom tray materials and compare it to the chemically-cured type. Also to evaluate the acceptance of light-cured acrylic resin custom trays by undergraduate students. / South Africa

A research report submitted to the School of Oral Health Science, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Dentistry in the field of Prosthodontics. Johannesburg, 2013 / Background: The majority of edentulous patients are unable to afford anything other than mucosa-borne complete dentures, but the conventional methods of complete denture fabrication can be lengthy and expensive. Simplified techniques have been proposed to reduce the number of clinical visits as well as the laboratory time and costs. One such technique has advocated making the final heat-cured acrylic resin denture base after the first visit, which then requires a second processing cure for the artificial teeth. This dual-cure has been reported to cause distortion of the previously cured denture base. Purpose: To measure the amount of linear and three-dimensional distortion of an acrylic resin maxillary denture base following an additional curing cycle using different processing methods. Method and Materials: A standardised method was developed for fabricating a maxillary denture base with measuring pins , as well as a standardised method for waxing an arch of teeth to the base. The pins were used to make three-dimensional measurements using a Reflex Microscope. The resins used were from the same manufacturer. Four dual cure methods of varying temperature and time were used: 1. Place flask in boiling water for 20 minutes, remove and plunge into cold water for 20 minutes; 2. Place into cold water, heat up to 70°C, leave for 1 hour, remove and bench cool; 3. Place into cold water, bring to 72°C for 8 hours and bench cool; and 4. Place in cold water, bring to the boil for 40 minutes, bench cool for 45 minutes, then plunge into cold water for 20 minutes. For each method five models were fabricated, to give a total of 20 models. Results: Although there was an overall distortion of all denture bases following a second cure, the linear and 3D differences were not statistically significant between and within the different dual cure methods tested. The mean percentage changes measured were translated into real changes in distances or angles between the pins, in order to ascertain the clinical relevance of these changes, for if they are too great, the distortion of the denture base will exceed the resilience of the mucosa as well as disrupt the peripheral seal, and the denture base will not be retentive. The largest mean change was seen in the three-dimension distance between the innermost pins in the posterior palate, but this was only 1.3mm. This also showed the worst change of all measurements, but it was still only 2.0mm. Conclusions: With the adaptive nature of the denture-supporting tissues, the changes described are unlikely to have any clinical significance. Although only one brand of denture base resin was used, it is representative of the modern rapid-cure resins, and so rapid cure methods can be advocated when a dual cure is required.

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Indiana University-Purdue University Indianapolis (IUPUI) / Indirect composites were introduced so that the composites can be cured extraorally to improve the degree of conversion and other material properties. These materials are indicated as long term full coverage dental restorative materials. However the mechanical and physical properties of new Second Generation Indirect Composites for this particular application have not been fully evaluated. The purpose of the study was to compare the appropriateness of the four commercially available laboratory composite resins for application as long term full coverage restorative materials. Water solubility and sorption levels, staining resistance, gloss, surface roughness, wear due to tooth brush abrasion, two-body and three-body wear, fracture toughness and radiopacity of four indirect composite restorative materials; Radica (Dentsply), Sculpture Plus (Pentron), Belleglass-NG (Kerr) and Gradia Indirect (GC America) were determined. The results showed that the four composites differed significantly from each other. Bell eglass-NG and Gradia Indirect showed negative water solubility. All the four groups demonstrated less color stability when exposed to coffee slurry for 3 weeks. Significant decrease in gloss and volume occurred when the omposites were exposed to simulated tooth-brush abrasion. Sculpture Plus v demonstrated lowest abrasion and attrition wear resistance among the four indirect composites. Radica had the highest fracture toughness and radiopacity of all the composites with values close to or less then dentin. In conclusion, different indirect composite systems possessed different mechanical and physical advantages when compared to each other. In general, Belleglass-NG demonstrated superior advantages due to its higher abrasion and attrition wear resistance and stain resistance. This was followed by Radica,Gradia Indirect and Sculpture Plus.