Faculty of Health Sciences
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Item Dental composite materials: highlighting the problem of wear for posterior restorations(South African Dental Association, 2007) Le Roux, Andre Rayne; Lachman, NirushaManufacturers of dental composites promote their products as having ideal wear resistant characteristics. Evaluation of the problems that persist with wear of dental composites is made. Recommendations for further research involving wear resistance of dental composite materials are provided. This article provides a review of English, peer-reviewed literature involving wear resistance of dental composite materials conducted through ScienceDirect and hand searched data bases between 1994 and 2006.Item Wear and flexural strength comparisons of alumina/feldspar resin infiltrated dental composites(South African Dental Association, 2008) Le Roux, Andre Rayne; Lachman, Nirusha; Walker, Mark; Botha, T.Introduction: Incorporating a feldspar chemical bond between alumina filler particles is expected to increase the wear-resistant and flexural strength properties. Aims and Objectives: An investigation was carried out to evaluate the influence of the feldspar chemical bonding between alumina filler particles on wear and flexural strength of experimental alumina/feldspar dental composites. It was hypothesized that wear resistance and flexural strength would be significantly increased with increased feldspar mass. Methods: Alumina was chemically sintered and bonded with 30% and 60% feldspar mass, silanized and infiltrated with UDMA resin to prepare the dental restorative composite material. Results and conclusions: Higher wear-resistant characteristics resulted with increased feldspar mass of up to 60% (p<0.05). Higher flexural strength characteristics resulted as the feldspar mass was increased up to 60% (p>0.05). Feldspar chemical bonding between the alumina particles may improve on the wear-resistance and flexural strength of alumina/ feldspar composites.Item Flexibility of experimental alumina/feldspar and SR ADORO dental composites(South African Dental Association, 2010) Le Roux, Andre Rayne; Lachman, NirushaIntroduction: Flexure of a dental composite can be detrimental to the success of a restoration. Flexibility considerations are thus important when comparing dental materials to optimize the success of resin restorations. Aims and objectives: Flexibility of 5.6 x 18.0 x 2.0 mm3 experimental alumina/feldspar and SR ADORO® dental composites specimens were compared. It was hypothesized that alumina/ feldspar composites would be less flexible under a load than SR ADORO® composites and that the flexibility would decrease significantly as the feldspar content was increased. Methods: Alumina was chemically sintered or bonded with 40%, 50% and 60% feldspar mass, silanized and infiltrated with urethane dimethacrylate (UDMA) to prepare the alumina/feldspar dental restorative composite specimens. Three point bending tests were performed in the Instron 44® machine for flexural comparison to SR ADORO®. Results and conclusions: The alumina/feldspar specimens showed lower flexibility (mm displacement) than SR ADORO® (p<0.05). Accurate flexibility comparisons were performed with 5.6 x 18.0 x 2.0 mm3 specimens. Flexibility comparisons performed with 5.6 x 18.0 x 2.0 mm3 specimens indicated that experimental alumina/ feldspar dental composites may provide added marginal seal benefit. However confirmation via in vivo function of alumina/ feldspar dental composites is recommended.Item Reducing the alloy thickness of base metal ceramic restorations(Dental Technicians Association of South Africa, 2009) Le Roux, Andre RayneReduction in base metal alloy thickness will permit additional porcelain depth and improved aesthetics but unfortunately little information exists regarding the thickness to which base metal alloys may be reduced in comparison to noble metal alloys for metal ceramic restorations. Even with comparison of noble metal alloys the aesthetic benefits are restricted to improving aesthetics in base metal restoration further, since noble metal alloys are generally regarded as providing superior aesthetics to base metal restorative alloys. Purpose: The objective of this study was to determine whether a significant reduction in thickness could be achieved using a base metal alloy as compared to a noble metal alloy and the thickness to which base metal alloy substructures could safely be reduced while still providing the same resistance to fracture of the porcelain. Material and methods: Tensile strength tests (N) of the modulus of rupture of the porcelain were performed on 40 base metal alloy (Wiron 99, Bego, Germany) and 12 noble metal alloy rectangular specimens (5.8 mm wide and 15.0 mm long) bonded to a standardized 1.0 mm thickness of dentine Creation porcelain. The base metal alloy thickness varied in 0.1mm increments from 0.1 to 0.4 mm. The results were compared to 12 noble metal alloy (Bio Y 81, Argen, South Africa) specimens of recommended minimum thickness (0.3 mm). Data for the results was obtained using a universal tensile testing instrument, which was set to operate at a cross head speed of 0.5mm (Instron Mini 44, Instron corporation U.S.A). The applied force (N) that measured the modulus of rupture of each specimen was printed from a computer connected to the Instron Mini 44 that operated on a 95% level of confidence. Instron Agents (Durban, South Africa) performed the calibration and setting up of the machine prior to testing the specimens. Results: The results indicated a permissible 33.33% reduction in the base metal alloy specimens as compared to the noble metal alloy control specimens. This was deduced from the reduction in alloy thickness of up to 0.2 mm for base metal alloy specimens as compared to the 0.3 mm noble metal alloy specimens. The recommended thickness to which the base metal alloys could be reduced without distortion of the alloy was also 0.2 mm. The one-way ANOVA showed a level of significance of (α=05).