Preparation And Performance Study Of PETG/BaTiO₃NPs Antibacterial Invisible Orthodontic Composite Material

Background:In recent years,the technology of orthodontic treatment using bracketless clear aligners has become increasingly popular among patients due to its aesthetic appeal,comfort,and convenience compared to traditional fixed braces.However,clinical studies have shown that patients using clear aligners may experience varying degrees of enamel demineralization,and in cases of poor oral hygiene,complications such as tooth decay and periodontal disease may arise,which can negatively affect the orthodontic treatment process and final outcome.The main cause of enamel demineralization is the growth,proliferation,and biofilm formation of pathogenic bacteria on the tooth surface.Therefore,the development of clear aligner materials with antibacterial properties is of great clinical significance.Objective:The aim of this study is to develop a new type of antibacterial clear aligner material to improve oral health problems caused by bacterial biofilm colonization on the tooth surface during orthodontic treatment,and to provide new ideas for the development of antibacterial clear aligner materials.Methods:In this study,piezoelectric Barium titanate nanoparticles（BaTiO₃NPs）were uniformly dispersed in the base material of clear aligners,polyethylene terephthalate-co-1,4-cyclohexylenedimethylene terephthalate（PETG）,at mass ratios of 0 wt%,wt%,20 wt%,and 30 wt%to synthesize PETG/BaTiO₃NPs（0 wt%,10wt%,20 wt%,and 30 wt%）diaphram.The microstructure,morphology,and composition of the materials were characterized using Scanning electron microscopy（SEM）,X-ray diffraction（XRD）and Raman spectroscopy.The 7-day salivary absorption rate of the materials were tested in artificial saliva.The surface hydrophobicity of the materials were measured using a contact angle tester.The thermal stability of the materials were evaluated using a thermogravimetric analyzer.The antibacterial effect of the materials against Streptococcus mutans biofilm were evaluated using the plate count method and crystal violet staining.The biocompatibility of the materials were evaluated using the CCK-8 cell viability assay and live/dead staining cytotoxicity assay.Results:（1）SEM,XRD and Raman spectroscopy characterized the successful synthesis of PETG/BaTiO₃NPs composite materials.（2）The 7-day saliva absorption rates of PETG/BaTiO₃NPs（0 wt%,10 wt%,20wt%,30 wt%）diaphram were 0.66%,0.37%,0.61%,and 0.52%,respectively.The saliva absorption rates of the composite diaphram containing BaTiO₃NPs were lower than those of the PETG base diaphram.（3）The average water contact angles of PETG/BaTiO₃NPs（0 wt%,10 wt%,20wt%,30 wt%）diaphram were 66.2±4.7°,70.6±5.5°,72.3±3.9°,80.5±7.3°,respectively.The surface hydrophobicity of the composite diaphram containing BaTiO₃NPs was higher than that of the PETG base diaphram,indicating that the surface hydrophobicity gradually increased with the increasing content of BaTiO₃NPs.（4）The initial decomposition temperature（～380℃）and final decomposition temperature（～460℃）of the composite diaphram containing BaTiO₃NPs were not significantly different from those of the PETG base diaphram,indicating good thermal stability.（5）The introduction of BaTiO₃NPs endowed the PETG/BaTiO₃NPs composite diaphram with antibacterial properties,which were dependent on the content of BaTiO₃NPs and the polarization of the materials.With the increase of BaTiO₃NPs content（10 wt%,20 wt%,30 wt%）,the antibacterial activity of the composite diaphram increased,and the antibacterial rates were 19.35±4.35%,37.64±5.75%,42.90±3.72%,respectively.Moreover,the antibacterial activity of the composite materials containing BaTiO₃NPs was significantly enhanced after surface polarization treatment,and the antibacterial rates were 41.65±2.34%,63.15±4.98%,67.39±5.35%,respectively.The enhancement of antibacterial rate of polarized complex membrane is related to the accumulation of reactiveoxygenspecies（ROS）in bacterial cell environment.（6）The statistical results of the CCK-8 experiments showed that the survival rate of L-929 cells co-cultured for 24 h,48 h,and 72 h was above 92.62%.CCK-8 cell toxicity experiments and Calcein-AM/PI cell toxicity experiments showed that the PETG/BaTiO₃NPs composite diaphram containing BaTiO₃NPs and polarized PETG/BaTiO₃NPs composite diaphram both exhibited good biocompatibility.Conclusion:In this study,PETG/BaTiO₃NPs antibacterial composite materials were successfully prepared.Compared with PETG matrix material,PETG/BaTiO₃NPs antibacterial composite materials have reduced salivary absorption rate and increased surface hydrophobicity,showing good biocompatibility.BaTiO₃NPs can be used as a modification material for invisible appliance.It has potential clinical application prospect.