Thesis (M.S. )--University of Tennessee Health Science Center, 2007. / Title from title page screen (June 30, 2008). Research advisor: Joo L. Ong, Ph.D. Document formatted into pages (vi, 47 p. : ill.). Vita. Abstract. Includes bibliographical references (p. 41-46).

Thesis (M.Sc. (Prosthodontics))--Mahidol University, 2008.

Thesis (M.S.)--University of Michigan, Ann Arbor, 1983. / Typescript (photocopy). Includes bibliographical references (leaves 45-48). Also issued in print.

Thesis (doctoral)--Lunds Universitet, Malmö, 1998. / Added t.p. with thesis statement inserted. Includes bibliographical references.

Thesis (M.S.)--University of Michigan, Ann Arbor, 1983. / Typescript (photocopy). eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 45-48).

Thesis (doctoral)--Lunds Universitet, Malmö, 1998. / Added t.p. with thesis statement inserted. Includes bibliographical references.

Thesis (D.Phil.(Dentistry))--Faculty of Health Sciences)-University of Pretoria, 2003. / Summary in English. Includes bibliographical references. Also available online.

Dissertation submitted in full compliance with the requirements of the degree of Master of Technology: Dental Technology, Durban University of Technology, 2012. / This study examined the perceptions of South African dental laboratory owners, dental technicians and dentists so as to understand their opinions and experiences regarding the outsourcing of dental prostheses in the industry. The study explored the legislative position of the South African Dental Technicians Council (SADTC). In addition, the study sought the Dental Technicians Association of South Africa (DENTASA) opinion regarding legislation and outsourcing practices in the dental laboratory industry. This is a post-positivist qualitative study conducted in the interpretive paradigm. The study was conducted in Gauteng as this province has the greatest concentration of technicians and dentists. Simple random sampling was used to select participants for individual semi-structured interviews. Interviews were conducted with three different groups of participants – laboratory owners, technicians and dentists. In addition, a representative of the SADTC and DENTASA, respectively, was interviewed. The data collected from interviews was analysed using thematic content analysis. Findings generated from the study revealed that where dental laboratory services are outsourced, no formal contractual relationship exists between parties. Contracts are verbal. The study concluded that the dental technology industry does not operate within clearly defined legal frameworks when outsourcing. It was established that offshore outsourcing occurs infrequently, therefore having minimal impact on the industry and labour market. Technicians interviewed failed to see the potential negative influence that enhanced outsourcing volumes could have on the labour market. The study established that domestic outsourcing is widely practised and dental laboratories receive significant quantities of imported work. The study briefly considered medical device legislation as the South African dental technician industry is reported to be required to comply with the International Standard of Operation (ISO 13485) which will legislate medical device legislation. Dentists stated, confirming a widely held dental technology industry belief that they did not believe that they were sufficiently qualified to carry out laboratory procedures. The study revealed that technicians regularly consult with patients with the consent of dentists. This is, currently, an illegal practice. Disclosure of who is doing the laboratory work does not always occur. It was established that economic consideration was not a driver when respondents considered outsourcing offshore. Quality was considered a more important factor than price. The study found that that no legislation exists in South Africa that regulates the dental laboratory materials used. Therefore, the possibility of inferior material filtering the South African market is real and the need for a regulatory body is indicated. Technicians felt that there is no need to regulate outsourcing in South Africa. Dentists, on the other hand, were ambivalent. In conclusion, it is postulated that dental technology industry is in a developmental stage and there is a need for the industry to understand itself better. This research showed that the dental technology industry has an inexperienced understanding of business practices. A greater emphasis on producing a well rounded dental technician with the knowledge and understanding of general business concepts and practices which include legislation, regulations and ethics related to the industry is indicated.

The main purpose of this study was to examine the difference in intrapulpal temperature (IPT) comparing a “grinding” and a “cutting” technique during single crown preparation. The difference in preparation time between the two techniques was also examined. A thermocouple was placed in the pulp chamber of 20 extracted human permanent molar teeth. The teeth were placed in a silicone model. The model was immersed in a thermostatically controlled water bath with a temperature of 37 degrees centigrade (°C), and with a water level reaching the cementoenamel junction at the teeth. For both preparation techniques an electric handpiece (NSK Ti-Max Ti85L 1:5) was used. A diamond bur was used for the “grinding” and a carbide bur for the “cutting” technique. The IPT during preparation was measured with a K-thermocouple connected to Testo 176 T4 temperature data logger. There was a significant difference in IPT rise between the two techniques for preparing the teeth. The “cutting” technique showed a higher mean temperature, 31.9 °C, compared to the “grinding”, 29.5 °C (p<0.05). Neither reached the critical value of 5.5 °C IPT increase. The “grinding” technique averaged a longer preparation time of 106 seconds per tooth than the “cutting” technique (p<0.05). Our study shows that the “cutting” technique results in a higher mean temperature but that both preparation techniques can be considered as safe in regard to IPT during single crown preparation as long as sufficient water cooling is applied.

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, 2012 / Statement of problem It is well documented that water sorption and water solubility by auto-polymerizing resins have a negative impact on their physical properties and may lead to harmful tissue reactions. The presence of residual monomer is often identified as the main cause for adverse tissue reactions. To optimize the polymerization reaction, the use of the proper powder/liquid ratio is recommended in the fabrication of a dental appliance. It is also recommended that a dental appliance should be soaked in water for at least 24 hours before delivery to a patient, in order to reduce the possible adverse effect. For auto-polymerizing resins, associated with higher residual monomer levels than heat-cured resins, soaking the appliance at elevated temperatures (65ºC for 60 minutes), would reduce the residual monomer content more efficiently than at room temperature. This requires additional processing conditions from the technician or dentist. Changing the powder/liquid ratios, deliberately or not, may modify the residual monomer content of the final product. A relationship exists between the levels of residual monomer and water sorption. Also, residual monomer leaching into the oral fluids may lead to adverse effects such as, oral tissue irritation or a delayed hypersensitivity reaction. Aim of the study The aim of this study was to evaluate the effect of different powder/liquid ratios and different water temperatures on the levels of sorption and solubility of an auto-polymerizing resin material used for denture bases. The null-hypothesis tested was that there is no difference in sorption and solubility among groups of specimens made from an auto-polymerizing resin material soaked in water at different temperatures and/or fabricated with different powder/liquid ratios. Material and methods Specimens were made from cold-cure pour-type denture base resin (Type 2, Class 2) using different powder/liquid ratios and soaked at different soaking temperatures. One group of specimens fabricated with the manufacturer’s recommended powder/liquid ratio and soaked in water at 37ºC, served as the control group for both experiments. Custom-made stainless steel moulds were used to fabricate resin disks, with a diameter of 50mm and a thickness of 0.5mm. For the temperature-controlled experiment, identical specimens were prepared and stored in distilled water at 37ºC; 45ºC; 55ºC and 67ºC. For the ratio-controlled experiment, the ratios were increased incrementally for each group, starting with a 10% increase, followed by a 15%; 20% and 25% increase in monomer. Water sorption and solubility were tested in accordance with ISO Standard 1567 (1999). Specimens were weighed before and after water immersion, and desiccation. Water sorption and solubility were calculated using the difference in wet and dry mass and the volume of the specimens. The water sorption and solubility results were analyzed by means of analysis of variance. For multiple comparisons, Bonferroni simultaneous confidence intervals (α=0.05) were applied. Results For the ratio-controlled experiment, water sorption mean values varied from 24.148 μg/mm3 to 25.1333 μg/mm3. Statistically significant differences in mean values were found between the following groups: 0%-10%; 0%-15%; 0%-25%; 10%-20%; 15%-20% and 20%-25% ratio groups (P<.0001). Water solubility mean values varied from 0.616μg/mm3 to 0.932μg/mm3. Statistically significant differences in mean values were found between the following groups: 0%-15%; 0%-20%; 0%-25% and 10%-25% and 20%-25% ratio groups (P<.0001). For the temperature-controlled experiment, water sorption mean values varied from 24.185μg/mm3 to 26.434μg/mm3. Statistically significant differences in mean values were found between the following groups: 37ºC-45ºC; 37ºC-55ºC; 37ºC-67ºC; 45ºC-67ºC and 55ºC-67ºC temperature-controlled experiments (P<.0001). Water solubility mean values, for the same experimental groups, varied from 0.616μg/mm3 to 2.752μg/mm3. Statistically significant differences in mean values were found among all the 6 pairs of groups (P<.0001). Despite statistical differences, the water sorption and water solubility values of the tested resin for both experiments and all groups were within the ISO Standard 1567 (1999) specification limits. Conclusion For the ratio-controlled experiment, there was an inverse relationship between the mean sorption and solubility values with an increase in liquid in the mixture: low water sorption levels are associated with high solubility levels. The lower water sorption and higher solubility results for more fluid mixtures could be related to initial and residual high monomer content characteristic of auto-polymerizing materials. These higher levels of free monomer are consequently released upon immersion in water; hence the higher water solubility levels. For the temperature-controlled experiment, a higher soaking temperature resulted in an increase in water solubility levels. The higher solubility levels could be attributed to the higher soaking temperatures causing higher or faster monomer diffusion from the resin material. Except for the 67ºC group, sorption is also lower with higher temperatures. It may be assumed that an additional polymerization process takes place and a subsequent more inaccessible polymer matrix is produced. For the 67ºC group, thermal expansion may explain the higher sorption level. Clinical Implications In terms of the sorption and solubility results, this auto-polymerizing pour-type resin may be used as a denture base resin. Even though statistical differences were demonstrated, the material satisfies the ISO 1567 (1999) requirements not only for auto-polymerizing but also for heat-polymerizing resins. Therefore, within limits, the mixture may be prepared more fluidly in order to improve flow of the material, without negatively affecting its sorption and solubility properties. Because solubility is higher at higher soaking temperatures, this property can be used to minimize monomer content of the appliance. Therefore, it is recommended that the dental appliance be soaked in warm water, below 67ºC, prior to delivery to the patient.