1. Degradation of an Organic Overlayer Model of a Dental Composite Analyzed by Liquid Chromatography Mass Spectrometry Peter Koin, 2 Ayben Kilislioglu, 4 Manshui Zhou, 1 James L. Drummond, 3 and Luke Hanley 1,* University of Illinois at Chicago, Departments of 1 Chemistry, 2 Bioengineering, and 3 Restorative Dentistry, m/c 111, Chicago, IL 60607-7061 USA 4 Istanbul University, Department of Chemistry, Avcilar 34320, Istanbul, Turkey Motivation Goals Degradation Study Purpose Dental Composites consist of a polymerizable resin matrix, reinforcing glass filler particles, and a silane coupler. One of the most used resin monomer of dental composites is Bisphenol A glycerolate dimethacrylate (BisGMA) Composites undergo property changes due to oral environment Environment can weaken materials and reduce restoration longevity Can release compounds into tissues and accumulate Study materials that can leach out of composite New System of Analysis Degradation studies of commercial composites too complex [1] Monolayer system to understand degradation and erosion [2] Monolayer System Dental composites made of resin matrix, glass particle filler, and a silane coupling agent Resin matrix: Bisphenol A glycerolate dimethacrylate (BisGMA) Glass filler: Nanoporous silicon chip Silane coupling agent: MPS- 3- (trimethoxysilyl) propyl methacrylate Glass particles used to reduce overall polymer shrinkage Silane coupler covalently links resin to glass filler: improves mechanical properties and increases hydrolytic stability due to hydrophobic nature Dental Composite Model Experimental Methods Conclusions Funded by National Institute of Dental and Craniofacial Research, DE-07979 [1] MS Zhou, JL. Drummond, L Hanley. Dental Materials. 21 (2005) : 145-155. [2] MS. Zhou, CP. Wu, PD. Edirisinghe, JL. Drummond, L. Hanley. Journal of Biomedical Materials Research A. 76 (2006). Results Study degradation of Dental Composite Model after aging in water for 2 weeks Qualitative analysis to find degradation peaks using MS Fragmenter software and MS-MS analysis Silicon Wafer (N-Type 100) 24 (wt)% HF/EtOH 20 mA/cm 2, 5 min Nanoporous silicon 31.6% H 2 O 2 50°C, 1hr Porous SiO 2 Surface (Stored in 1N HNO 3 Solution) Porous SiO2 2 (wt) % MPS/Toluene 60°C, 96hrs Wash Toluene Baking 80°C, 12hrs MPS-Silanized Substrate 2.0 mg/ml BisGMA/EtOH Initiator Solution Cure, UV light 20 min Polymerized methacryloyl BisGMA Overlayer Instrumentation LCMS –Finnigan Mat LcQ HPLC –SpectraSYSTEMS SCM 1000 vacuum membrane degasser –P4000 gradient elution pump –AS 3000 autosampler –UV 2000 dual-wave length detector Data Analysis Software ACD Labs (Toronto, Ont., Canada) ACD MS Manager to analyze and process data ACD MS Fragmenter- Program generates fragments and structures by using standard fragmentation rules HPLC Conditions Mobile Phase: Gradient of MeOH/H20 Flow Rate: 0.3 ml/min Temperature: Room Temperature, 25°C UV Wavelength: 250 nm Column: Reverse Phase Water Symmetry C18 3.5 μm, 3.0 mm diameter, 150 mm length Injection volume: 10 μ L Standards Analysis to find retention time Standards Resin Material: BisGMA Silane Coupler: MPS- not run because of adverse effect of MPS with columns Photoinitiator solution: triethanolamine, vinyl pyrrolidinone, and eosin Y Glass Filler: nanoporous silicon chip, prepared similar to DIOS chips –Possible Degradation Products: bisphenol A, methacrylic acid Aged Monolayer Samples 3 nanoporous silicon chips per sample 2 weeks aged in de-ionized water Also aged blank nanoporous silicon chip with no BisGMA or methacryloyl layer to determine nanoporous silicon background TIC of Extract from Methacryoyl BisGMA monolayer on nanoporous silicon aged for 2 weeks in DI water. Electrospray ion trap mass spectra of BISGMA from TIC at 16.0 min with a main peak of m/z 530. M+NH4 MSMS of BisGMA, m/z 530. Spectra shows the M+NH 4 peak at m/z 530, M+H peak at m/z 513, M-H 2 0+H at m/z 495, and main degradation products at m/z 191, 277, and 427 Retention Time (min) m/zName # of runs Structure Method of ID peak Structure (# of runs) 16.014 +/- 0.546530BisGMA26 MS of Standard- Obvious 20.623 +/- 0.517634(BisGMA)”25Unknown StructureMS/MS (14) 19.088 +/- 0.477620(BisGMA)’15Unknown StructureMS/MS (4) 21.819 +/- 0.526644(BisGMA)”’12Unknown StructureMS/MS (8) 11.343 +/- 0.547462 BisGMA-MA 15 MS Fragmenter Software, MSMS (4) 24.115 +/- 0.304363 BisGMA- 2MA 5 MS Fragmenter Software Unknown Structure Electrospray ion trap mass spectra of (BisGMA)’ Polymer at 18.6 min, which is a BisGMA polymer derivative with a m/z difference of 44 between peaks. Unknown Structure Electrospray ion trap mass spectra of (BisGMA)” Polymer at 20.4 min. Unknown Structure Electrospray ion trap mass spectra of (BisGMA)”’ Polymer at 21.8 min, which is a BisGMA polymer derivative with a m/z difference of 44 between peaks. CH 3 CH 3 O O OH O OH CH 3 OH CH 2 O +H +H-H 2 O Electrospray ion trap mass spectra from TIC at RT= 11.5 min with a main peak at m/z 462 that corresponds to a BisGMA degradation product Electrospray ion trap mass spectra of BisGMA degradation product with a m/z 363, at a retention time of 23.8 min. TIC of Pure BisGMA run through HPLC, no aging. Unreacted BisGMA strongly adsorbs to surface of nanoporous silicon and slowly leaches out Aging also causes hydrolysis of ester bonds and causes degradation products of BisGMA to appear Oligomer peaks with unknown structures also appear after aging BisGMA-methacryloyl monolayer BisGMA-MA m/z 462 BisGMA-2MA m/z 363 A B Reaction of BisGMA-methacryloyl monolayer in the presence of water. Hydrolysis of ester bonds causes degradation products of BisGMA to appear. Hydrolysis reactions can also occur at black arrows, but do not show up in sample data. 530 462 363