EventProf. Dirk W. Grijpma

Preparation of Orbital Floor Implants by Stereolithography using a PTMC and Nanoapatite Composite Resin

Introduction. Critical size fractures of the orbital floor are common injuries in traffic accidents and assaults. Inadequate treatment may result in serious complications such as extraocular muscle dysfunction and diplopia1. To reconstruct critical orbital floor defects, degradable osteoinductive implants that precisely fit the defect are required. Here, we report on composite structures of photo-crosslinked PTMC with osteoinductive nano-apatite powder prepared by stereolithography.

 

Methods. Three-armed PTMC was synthesized by ring-opening polymerization of trimethylene carbonate initiated by trimethylolpropane. The resulting oligomers were end-functionalized with methacrylic anhydride. To prepare a photocurable resin for use in stereolithography, nanoapatite powder was first dispersed in chloroform then the macromer and hydroquinone were dissolved in this dispersion. The composite dispersion was precipitated in methanol and dried. As a diluent, 40-50 wt.% propylene carbonate was added. After sonication, photoinitiator (5 wt.%) and Orasol Orange G dye (0.15 wt.%) were added, and implants were prepared using CT imaging data of defects in orbital floors. This data was converted to virtual models that were subsequently reproduced by stereolithography.

 

Results. The Mn and the degree of functionalization (DF) of the functionalized PTMC oligomer was determined by 1H-NMR, yielding an M value of 10 kg/mol and a DF of 80%. Gel contents of the composites were between 75 and 85%, indicating no significant interference of the nanoapatite with photo-crosslinking. SEM images showed incorporation of nanoapatite in the networks; the particles were homogeneously distributed.

Composite implants were prepared by stereolithography using virtual models of orbital floor defects obtained by imaging. Figure 1 shows the defect model and a manufactured PTMC composite orbital floor implant containing 10 wt.% nanoapatite.

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Figure 1. Orbital floor defect model (left), and corresponding PTMC/nanoapatite composite implant (right)

Conclusions. It was shown that photo-crosslinked PTMC and nanoapatite composite networks can readily be prepared. Using a photo-curable PTMC and nanoapatite resin, we prepared composite implants by stereolithography using imaging data of the orbital floor.

About The Speaker

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Prof. Dr. Dirk W. Grijpma is professor and head of the department of Biomaterials Science and Technology at the University of Twente. He also holds a part-time professorship in the Development and Clinical Application of Biodegradable Polymers at the University Medical Center Groningen. His expertise is in the synthesis, advanced processing and properties of (degradable) polymeric materials for use in medical devices, tissue engineering and in the delivery of relevant biologically active compounds. His research also includes the interaction of these materials and devices with cells and tissues.

He is editorial board member of Biomaterials, Acta Biomaterialia, the Journal for Applied Biomaterials and Biomechanics, the Journal of Orthopedic Translation and the Journal of Medical Materials and Technologies. He was elected Fellow Biomaterials Science and Engineering (FBSE) in 2008. Professor Grijpma is (co)author of more than 235 refereed scientific publications and is (co)inventor on 24 international patent applications.