Thesis (Ph.D.)--University of Hong Kong, 2004. / Also available in print.

Thesis (Ph. D.)--Drexel University, 2005. / Includes abstract and vita. Includes bibliographical references (leaves 90-94).

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.

This work is devoted to the synthesis, characterization and modification of a class of acrylic-based superabsorbent polymers. The techniques of inverse suspension and solution polymerisations were used for synthesis. Each absorbent was mainly characterised by its equilibrium capacity of water absorption and by the rate of absorption. The swelling characteristics of the polymers were evaluated in terms of change in polymerisation variables which include, type and amount of crosslinker, monomer composition, process of polymerisation, temperature, initiator concentration, monomer concentration and particle size of the product. The swelling dependency on salinity was also examined. In some cases, the base polymer was blended with certain polymers in order to upgrade the swelling properties. A swelling model was devised based on a simple viscoelastic model, i. e. Voigt model, to obtain a better understanding of the effect of the above-mentioned variables on the swelling behaviour. Finally, our materials of choice were compared with some commercial analogues and some further comments have been made for continuing the work.

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.

Limitations in the clinical applicability as well as undesireable side effects of the natural antispasmodic drubs, atropine and papaverine, turned early investigators to the problem of developing a more suitable antispasmodic through synthetic procedure.

the toxic effects resulting from acrylic monomer exposure can pose as occupational risk factors for those involved in the manufacture, distribution, and use of the monomer and as potential risk factors for those accidentally exposed. This study is a toxicological assessment of the in vivo (intact animal) and in vitro (isolated human cell culture) responses to acute methyl (α)-chloroacrylate (MCA) exposure.

Submitted in fulfillment of the Degree of Master in Technology: Dental Technology in the Department of Dental Services Faculty of Health Sciences, Durban University of Technology, 2008. / Globally in the field of Dental Technology, polymethyl methacrylate (PMMA) resin continues to be the popular material for the fabrication of denture bases in removable prosthodontics. However, the mechanical strength of the denture base is a concern due to fractures occurring intra-orally or when accidentally dropped. The objective of this in vitro investigation was therefore to evaluate and compare the flexural strength and microstructure of stick® glass fibre and wire mesh reinforced PMMA resin after thermocycling. The selection of the materials used in this study was based primarily on their popularity and availability in South Africa. These materials were selected to ensure that the results of this study would have further implicational value in the commercial dental industry when published. This investigation was conducted by means of fabricating a total of 90 PMMA resin specimens and divided in three groups consisting of 30 specimens each. Sample groups 1 and 2 were reinforced with stick® glass fibres and wire mesh respectively. The un-reinforced sample group was the control. All 90 specimens were thermocycled in water at temperatures between 5˚C and 55˚C for 2100 cycles. The flexural strength of each specimen was tested using a universal testing machine and the microstructure of the fractured surfaces was then analysed using scanning electron microscopes (SEM). SPSS version 15.0 was used for data analysis. A p-value of <0.05 was considered as statistically significant. Data were analysed using parametric and non-parametric statistical methods. Statistically significant differences in flexural strength existed between the three sample groups (p<0.001) with the stick® glass fibre and wire mesh sample groups being significantly superior to the control. Furthermore there was a significant association between fracture modes and sample groups. Microscopic analysis revealed the presence of voids. Statistically, in terms of microstructure (% of voids present), a significant difference existed between all sample groups. With regards to surface texture of the compression and tension sides of the test specimens, significant differences existed between the three sample groups. Furthermore microscopic analysis revealed partial impregnation and distribution of the fibres to the PMMA resin matrix and un-bonding between the wire mesh and PMMA resin matrix. Statistically, the Mann-Whitney test was conducted to compare flexural strength between sample groups with and without voids. The flexural strength was higher in sample groups with voids than those without. This is an important finding from the clinical perspective because, in some structures of dentures, toughness is a desired property. Nevertheless in order to find the long-term data especially on clinical behaviour of these new fibre reinforcement systems, more studies should be conducted. / DUT Institutional Research Committee

No description available.

The reason for this paper is to present a study of the compatibility of alkyd polyesters and acrylic paints in a painting technique incorporating plastic laminations. A number of tests ware conducted in order to discover the basic handling and visual characteristics of polyester in combination with acrylic paints. After the initial experiments, or "test plates," the information derived was applied to a series of demonstration paintings.