Development of Poly(L-lactic acid)/Organically Modified Montmorillonite Nanocomposites for the Fabrication of Orthodontic Anchoring Screws

作者：Nakanishi Ko^*; Yamagata Shuichi; Akasaka Tsukasa; Abe Shigeaki; Yoshida Yasuhiro; Iida Junichiro

来源：Journal of Nanoscience and Nanotechnology, 2016, 16(9): 9292-9297.

DOI：10.1166/jnn.2016.12917

• Poly(lactic acid)
• Montmorillonite
• Nanocomposites
• Orthodontic Anchorage
• Anchoring Screw

Titanium orthodontic anchoring screws are being increasingly used as a source of orthodontic force. However, the incidence of screw fracture during insertion and removal is not negligible; sometimes, invasive procedures are required for removal of the screw fragments. Therefore, poly(L-lactic acid) (PLLA)/organically modified montmorillonite (OMMT) nanocomposites were fabricated via a solution intercalation method for the development of novel orthodontic anchoring screws with adequate mechanical strength and bioabsorbability. The structural features and mechanical and thermal properties of the screws were characterized, and the viability of cells exposed to OMMT was also investigated to evaluate the biological safety of the PLLA/OMMT composites. Human osteosarcoma (MG-63) and mouse osteoblastic (MC3T3-E1) cell lines were used as target cells. The (001) diffraction peaks in the X-ray diffraction patterns of samples of pure OMMT, and polymer composites containing 2 and 4 vvt% OMMT were 2 theta = 2.5, 2.3, and 2.3 degrees, indicating interlayer distances of 3.5, 3.8 and 3.8 nm, respectively. Transmission electron microscopy images of the nanocomposite with 4 wt% OMMT revealed that the interlayer distance of the compounded OMMT was irregularly enlarged and ranged from 2 to 5 nm. In addition, some of OMMT layers were exfoliated. The flexural modulus values of the nanocomposites were significantly increased compared to that for pure PLLA, according to the results of three-point transverse analyses. Differential scanning calorimetry measurements also revealed that the glass transition temperatures, melting temperatures and degree of crystallinity were nearly the same for all of the samples and, thus, independent of the quantity of added OMMT. The cell viabilities for the MG-63 and MC3T3-E1 cells (greater than 90% and 80%, respectively) were also independent of the OMMT concentration. Scanning electron microscopy images of both types of cells following OMMT exposure exhibited normal shapes. Based on these results, we conclude that PLLA/OMMT nanocomposites prepared via solution intercalation should be useful for the development of bioabsorbable orthodontic anchoring screws.

• 出版日期2016-9