Serife Akkoyun - Department of Metallurgical and Materials Engineering, Faculty of Engineering and Natural Sciences, Ankara Yildirim Beyazit University, Ankara, Turkey
Mahmut Özdoğan - Department of Prosthodontics, Faculty of Dentistry, Ankara Yildirim Beyazit University, Ankara, Turkey

Introduction: This study presents a new design of multilayered PMMA dental composite material combining electrospun continuous composite polyvinylpyrrolidone (PVP) nanofibers filled with zirconia (ZrO۲) nanoparticles and two-component self-cure PMMA dental resin. The aim is to improve the mechanical properties of dental PMMA material via the large surface area of electrospun nanofibers, the toughening effect of PVP and ZrO۲ nanofillers. Methods: First, PVP/ZrO۲ composite nanofibers with different ZrO۲ contents of ۵%, ۱۰% and ۲۰% (wt. % of PVP) were prepared by electrospinning. Then, multilayered samples containing alternating PMMA resin and electrospun composite nanofiber mats with different ZrO۲ contents were manufactured by lay-up process. Samples containing single and double layers of nanofiber mats were prepared and cured in a water bath dental acrylic curing device in order to prepare composites without any void. Results: FTIR and SEM results reveal that PVP enables good interfacial interactions and compatibility between the nanofibers and PMMA matrix. The mechanical properties are improved as an increase of the flexural strength up to ۸۳% and ۶۷% is observed for PMMA/PVP/ZrO۲-۱۰s and PMMA/PVP/ZrO۲-۲۰d samples, respectively. The presence of PVP nanofiber layers significantly improves the flexural toughness, especially for samples reinforced with a single layer of nanofibers where improvements up to ۱۶۹% and ۱۵۳% are observed for PMMA/PVP/ZrO۲-۵s and PMMA/PVP/ZrO۲-۱۰s composite samples respectively. The micro-hardness is also higher for composite samples compared to neat PMMA dental material. Conclusion: The overall results clearly depict a noticeable enhancement of the mechanical properties, especially the flexural toughness of PMMA dental material 

dental composite, PMMA, Electrospinning, PVP/ZrO۲ composite nanofibers, flexural properties