Remineralization of Artificial Dentin Lesions via the Polymer-Induced Liquid-Precursor (PILP) Process
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Remineralization of Artificial Dentin Lesions via the Polymer-Induced Liquid-Precursor (PILP) Process Taili Thula-Mata1, Anora Burwell2, Laurie B. Gower1, Stefan Habelizt2 and Grayson Marshall2 1 Materials Science & Engineering Department, University of Florida, Gainesville, FL 32611, U.S.A. 2 Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, CA, U.S.A. ABSTRACT Acid-etched dentin samples with a zone of demineralized dentin were remineralized via the polymer-induced liquid-precursor (PILP) process. Poly-L-aspartic acid was used as the polymeric process-directing agent. Samples were incubated in the mineralization solution for 14 weeks. Dentin samples remineralized by the PILP process presented a surface morphology very similar to the intact mineralized dentin’s architecture, in contrast to samples mineralized via the conventional nucleation and growth method (without polymer additive), which led to a superficial crust of randomly organized mineral crystals. Energy dispersive x-ray spectroscopy analysis of the PILP-mineralized samples showed the presence of calcium and phosphate ions at high levels. Since no hydroxyapatite (HA) clusters were observed on the surface of the PILPmineralized samples, we could conclude the signal was produced from the mineral embedded within the dentin matrix. TEM and diffraction analyses suggest that both intrafibrillar and interfibrillar remineralization occurred in the demineralized dentin matrix. INTRODUCTION Dental caries represents a major problem in dentistry despite the significant advances in preventive care. Repair of caries using resin-composite fillings is the preferred treatment. However, bonding between dentin and fillings created by adhesives fails with time due to in vivo degradation of demineralized collagen. A common experimental approach to improve the durability of these bonds is the remineralization of dentin in situ. Our group has been able to achieve intrafibrillar mineralization of a diverse group of collagen matrices using the polymerinduced liquid-precursor (PILP) mineralization process [1, 2]. The PILP process consists of the addition of anionic polymers to a supersaturated mineralization solution in order to induce an amorphous calcium phosphate precursor. The current work reported herein is focused on using this same polymer-directed process to remineralize partially demineralized human dentin substrates, where it is of interest to determine if this PILP process is capable of calcium phosphate mineral formation throughout multiple levels of the dentin hierarchical structure. EXPERIMENTAL DETAILS Dentin specimens were prepared from extracted non-carious human teeth. Prior to demineralization, teeth were cut into cubes with a 6-mm2 exposed surface area, followed by polishing to 0.25 µm. Demineralization of dentin was carried out for 66 hours in 40 mL of 0.05M acetic acid buffered with 2.2mM Ca2+ and PO43- (pH=5.0). Acid-etched dentin samples with a 150-µm-thick zone of highly demineralized dentin on top of the nat
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