Document Type

Dissertation

Date of Award

12-31-2021

Degree Name

Doctor of Philosophy in Materials Science and Engineering - (Ph.D.)

Department

Committee for the Interdisciplinary Program in Materials Science and Engineering

First Advisor

Michael Jaffe

Second Advisor

N. M. Ravindra

Third Advisor

Cristiano L. Dias

Fourth Advisor

Murat Guvendiren

Fifth Advisor

Henry Keith Chenault

Abstract

Amalgam and Bisphenol A glycerolate dimethacrylate (BisGMA) are the main dental filling materials in use today. Because of the negative perception of amalgam and its lower esthetic appeal, as well as the desire to replace the endocrine disruptor Bisphenol A, which is the building block of BisGMA, there has been a critical need to search for safer alternatives to these dental filling materials.

Isosorbide is a sugar-based molecule generally recognized as safe. It has been extensively studied as a replacement to the Bisphenol A core in various materials. However, isosorbide is extremely hygroscopic, and water uptake in dental fillings causes expansion, plasticization and reduced mechanical properties.

Hydrophilic materials take up more water than hydrophobic ones. Therefore, modifying isosorbide with hydrophobic moieties such as hydroxy benzoates, can lead to improved and controlled water uptake and mechanical properties of the isosorbide dental resin.

A series of bio-based hydrophobically modified isosorbide dimethacrylates, with a para, meta, and ortho benzoate aromatic spacer, are synthesized, characterized, and evaluated as dental restorative resins. The new monomers, isosorbide 2,5-bis(glyceryloxybenzoate) dimethacrylates, are further mixed with triethylene glycol dimethacrylate (TEGDMA) at a 60:40 weight ratio, and evaluated for viscosity, degree of conversion, polymerization shrinkage, water sorption, glass transition temperature, flexural strength, and modulus. BisGMA is prepared and evaluated as a reference. Isosorbide glycerolate dimethacrylate (ISDGMA), a hydrophilic isosorbide dimethacrylate control, is synthesized and evaluated as well.

The polymers derived from the hydrophobically modified isosorbide dimethacrylates show significant reduction in water sorption at 39-44 µg/mm3 over poly(ISDGMA/TEGDMA) at 73 µg/mm3, and improved network stability. Their flexural strength is also higher at 37-42 MPa in comparison to 10 MPa for poly(ISDGMA/TEGDMA) after immersion in a phosphate buffer solution for 24 hours.

The performance of the new materials is close to that of the reference poly(BisGMA/TEGDMA), whose water sorption is 26 µg/mm3 and flexural strength is 52 MPa. The degree of monomeric conversion and glass transition temperature for the ortho derived isosorbide polymer at 52% and 85°C is also close to that of poly(BisGMA/TEGDMA) at 54% and 95°C, respectively. Therefore, this dissertation demonstrates the design and development of a potential BisGMA dental resin replacement.

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