Advisory Committee Chair
Nathaniel Lawson Lawson
Document Type
Thesis
Date of Award
2024
Degree Name by School
Master of Science (MS) School of Dentistry
Abstract
Background: This project investigates the materials used in injection molding dental resin composites which involves injecting flowable composite into a clear mold. Understanding the physical and optical properties of both the resin composite and the clear mold material is crucial for successful clinical outcomes. For the clear mold material, its translucency, curing light transmission, and rigidity are vital factors. Correlations may be present between trans-lucency and curing light transmission. For the resin composite, comparing wear, hardness, translucency, radiopacity, shrinkage stress, flexural strength, and modulus will affect mate-rial performance. Finally, the depth of cure of the material will be dependent on both the resin composite and clear mold materials. Objectives: This study investigates the translucency, curing light transmission, and rigidity of clear polyvinyl siloxane (PVS) materials. Additionally, the study investigates the filler weight percentage, wear, hardness, translucency, radiopacity, shrinkage stress, flexural strength, and modulus of resin composites commonly used for injection molding. Finally, this study will compare the depth of cure of a composite after curing through different thicknesses of different clear PVS materials. Materials and Methods: Four clear PVS materials were used. 2mm, 4mm, 6mm, 8mm, and 10mm tall cylinders of the materials were prepared in molds. The translucency of the specimens were calculated by measuring the translucency parameter (change in color be-tween a white and black background). The same specimens were used to measure the de-crease in light intensity on an integrating sphere when the specimens are cured through. The rigidity of the clear PVS materials was tested by measuring the slope of the force/displacement curve required to compress (compression) specimens 30% of their length. Five flowable resin composites and one conventional composite (Filtek Supreme) were used. The filler weight percentage of each resin composite was determined by weigh-ing specimens before and after burning out all resin content. Wear was tested in the UAB wear machine using 33% glycerine, stainless steel antagonists, 20N load, and 400,000 cy-cles. Hardness was measured with a Vickers microhardness tester. Translucency was tested similar to the clear PVS materials. Radiopacity was measured using digital radiographs relative to an aluminum step ladder. Shrinkage stress was measured by bonding composite between 2 plexiglass tubes that were 2mm apart and connected to a load cell. Flexural strength and modulus was tested with 2x2x25mm bars in a 3-point bend loading fixture in a universal testing machine. The depth of cure was measured in a split metal mold. Clear PVS cylinders of different thicknesses was placed above the hole in the metal mold and cured through. Results: In the evaluation of polyvinyl siloxane (PVS) materials, Exaclear exhibited the highest translucency and light transmission across all thicknesses compared to other materi-als. Affinity and Memosil 2 demonstrated the highest compressive modulus. For composite materials, Filtek Supreme had the highest filler content at 71.95%, while Evanesce had the lowest at 52.73%. Wear resistance was found to be highest in Filtek Supreme and Clearfill Majesty ES Flow, while Filtek Supreme Flowable and Omnichroma demonstrated the least wear. Hardness values ranged from 17.01Hv for Evanesce to 90.28Hv for Filtek Supreme. Omnichroma exhibited the highest translucency with TP = 19.09 and Evanesce Flow showing the least. Radiopacity was lowest in Omnichroma at 0.3, while Filtek Supreme and Supreme Flow had a similar value of 1.5. Shrinkage was maximum in Clearfill Majesty ES Flow at 78.00MPa and minimal in Evanesce Flow at 39.17MPa. Moreover, Filtek Supreme had the highest flexural strength and modulus, whereas Evanesce showed the lowest values for both parameters. Conclusion: Translucency and irradiance transmission through clear PVS materials de-creased as their thickness increased, yet Exaclear exceled in maintaining high translucency and superior light transmission capabilities. Compressive modulus in clear PVS materials varied by type; Affinity and Memosil 2 demonstrate higher modulus, offering more stability of the clear mold. The conventional composite had higher filler percentage, more wear, higher hardness, higher radiopacity, lower shrinkage stress, higher flexural strength, and higher modulus than most of the flowable composites. Keywords: flowable composite, injection molding, light irradiance, curing light trans-mission
Recommended Citation
Farias Machado, Nadia Christine, "Physical And Optical Properties Of Material Used For Injection Molding" (2024). All ETDs from UAB. 3892.
https://digitalcommons.library.uab.edu/etd-collection/3892