Fabrication And Evaluation Of Sustained Release Dental Fillers Using 3D Printing Technology

In view of the high incidence and long-term treatment of dental caries,personalized dental fillers with long therapeutic action have broad application prospects in the dental clinic.In this study,dental fillers were fabricated via 3D printing technology,and then evaluated using in vitro dissolution and biomechanical behavior simulation.The results could provide an experimental basis for the preparation and evaluation of personalized sustained release implants.Customized molds were prepared via 3D scanning and 3D printing,tinidazole(TNZ)dental filler was prepared using hot melt extrusion and thermal pressing.The results showed that using mold prepared by polylactic acid,the obtained dental filler had a smooth appearance and well-fitted dimensions with the dental cavity.The thermal degradation of TNZ started at about 201?,indicating that TNZ had good thermal stability throughout the preparation process.TNZ exhibited a sharp endothermic peak at 125?,and TNZ existed in the form of microcrystal in the dental fillers.To improve the HME operation,triethyl citrate was used as an optimal plasticizer.To ensure the high strength(?_b=3.40 MPa)and toughness(?_b=10.0%)of dental fillers,the optimal plasticizer concentration was 20%.Customized dissolution mold was prepared by 3D printing,miniature release pool was designed,and a novel in vitro release method of dental fillers was established.Hydroxypropyl methylcellulose-E5 was chosen as release modifier to maintain drug concentration of media above the minimal antibacterial concentration of TNZ.The TNZ release characteristics can be tailored based on clinical requirements by varying the concentration of release modifier from 2.5%to 10%.The optimized dental filler was capable of sustained releasing TNZ over one week.The most appropriate model was the Peppas equation(R=0.9861),and the drug release mechanism was considered as diffusion-erosion dominant(n=0.629).Customized compression mold was prepared by 3D printing,and a compression behavior test method of dental fillers was established.The result showed that the compression process of dental fillers could be quantitatively evaluated via the compression stress-compression strain curves,and the influence of immersion for 7 d on the compression behavior of dental fillers could be evaluated.Typical 1/2 3D mesh models of dental filler and compression mold were established,and the biomechanical behavior simulation was conducted using finite element method.The results of Von Mises stress distribution and Von Mises strain distribution showed that the ultimate Von Mises stress appeared on the contact surface of compression mold with high strength,while the ultimate strain appeared on the contact surface of the dental filler with high ductility.The ultimate Von Mises stress had no obvious different after immersion in the media for one week,while the ultimate Von Mises significantly increased from 10.6%to 13.8%.The optimal dental filler was biomechanically integrity during immersion for one week,and met the clinical use requirement.Based on the simulation model,various influence factors on the biomechanical behavior of dental fillers was studied.A good linear relationship between the force and the ultimate Von Mises stress was found,and the angle of the caries cavity obviously affected the ultimate Von Mises stress.To ensure the high strength and small deformation of the filler during treatment,and to accelerate the drug release,multi-layer dental fillers were prepared.The optimized sealing layer was composed of polylactic acid:triethyl citrate=4:1,while the optimized immediate-release layer was Soluplus~?.Typical double-layer dental filler was used to evaluate the biomechanical behavior.The result of the simulation indicated that the ultimate Von Mises stress appeared on the contact surface of compression mold,while the ultimate Von Mises strain appeared on the contact surface of the double-layered dental filler.There was no significant change in the Von Mises strain distribution,but the ultimate Von Mises stress decreased significantly,suggesting that the double-layered filler had good strength and little deformation during normal chewing process.Typical three-layer dental filler was used to evaluate the in vitro dissolution.The result showed that the immediate-release layer facilitated the drug release.The drug concentration at 5 min reached the minimum inhibitory concentration,the highest drug concentration obtained at 0.5 d,while the sustained-release behavior lasted for more than 7d.