| The aging of our society is becoming more and more serious.The incidence of aging dental caries is high while the treatment rate is low.The demand for treatment of dental diseases such as dental caries and edentulous jaws is increasing.Polymethyl methacrylate?PMMA?is used in dental restorations for denture bases because of its biocompatibility,odorlessness,transparency,low cost,ease of handling,and high patient acceptance.However,there are some technical problems limit the clinical application of PMMA resin,such as high shrinkage rate,low one-time curing degree,poor mechanical strength,low bacterial resistance,etc.With the rapid development of nanomaterials and digital light processing?DLP?photocurable additive manufacturing technology,high-performance,high-precision,personalized denture treatment is expected to become the mainstream mainstream of dental prosthetics worldwide.In this study,according to the clinical requirements of the oral cavity and the problems faced in the denture manufacturing process,the nano-filler is used to enhance the mechanical properties,biocompatibility and antibacterial properties of the PMMA photosensitive resin;the DLP photo-curing 3D printing device is improved;and the3D molding process of the prepared novel PMMA resin is verified.The study carried out the following research:First,two different PMMA resins that can be used in the manufacture of photo-cured denture bases were prepared by nano-filler modification technology.1.Modification of PMMA photosensitive resin using silver nanoparticles?Ag NPs?and nano-cellulose?CNCs?.The Ag NPs were uniformly dispersed on the CNCs surface to prepare the CNCs-Ag composite materials,which was then added to the PMMA resin with different proportions.The prepared CNCs-Ag/PMMA resin had good mechanical properties,antibacterial efficacy,biocompatibility and basic 3D printing performance.The experimental results showed that the CNCs-Ag/PMMA-0.1 resin was the most optimal resin comparing to other experimental groups.Compared with pure PMMA resin,the shrinkage rate of CNCs-Ag/PMMA-0.1 was reduced by 0.25%,the forming precision,bending strength,flexural modulus and impact resistance was increased by 2.78%,12.00%,5.70%,and 72.80%,respectively.CNCs-Ag/PMMA resin?CNCs-Ag within the range of 0.10–0.25 wt.%?exhibit high antibacterial activity with no significant cytotoxic effect.2.Modification of PMMA resin by nano titanium dioxide?Ti O2?and micron PEEK.The Ti O2-KH570/PEEK filler is added to the PMMA resin with different proportions.The prepared Ti O2-KH570/PEEK/PMMA resin had good mechanical properties,antibacterial efficacy,biocompatibility and basic 3D printing performance.When the addition amount of Ti O2-KH570 and PEEK is 1 wt.%,respectively,PMMA resin was the most optimal resin comparing to other experimental groups.Compared with pure PMMA resin,the shrinkage rate of the comoisute resin was reduced by 0.72%,and forming precision,bending strength,flexural modulus and impact resistance was increased by1.66%,18.60%,13.00%,and 44.80%,respectively.When the content of Ti O2-KH570 was 1wt.%or above,the PMMA resin exhibited good antibacterial properties;when the content of Ti O2was 1 wt.%and the content of PEEK was in the range of 0.5-3 wt.%,the prepared PMMA resins had good cytocompatibility and may have had some effect on promoting cell activities.Secondly,according to the patient treat requirements and the prepared PMMA resin properties,we systematically studied and improved the design of personalized denture base and molding process of the integrated denture.Through the techniques,such as,CT scanning,CAD modeling,finite element analysis,etc,we analyzed and proposed the clinical solution of denture base from individual design to high precision manufacturing.1.Using CAD/CAE technology to personalize the design and analysis of the denture base,therefore the prepared denture base was more comfortable.2.First proposing the molding method of full-denture multi-color integrated based on DLP light curing 3D printing.3.Proosing and verifing the design principle of the personalized denture base.The denture base prepared by the proosed design in this study has better manufacturing precision and tissue comfort than the traditional denture base preparation process.Thirdly,DLP photocuring 3D printing special equipment was developed and the molding process was improved,according to the requirements of patient and the denture base manufacturing.1.The Dental-1 device used the optical correction method to reduce the barrel distortion during surface exposure by adding an anti-distortion lens,which improved the molding accuracy and device stability.2.The Dental-2 device used the software correction method to adjust the gray value of the projected image according to the linear interpolation algorithm,which formed a relatively uniform light irradiation distribution.The light irradiance was uniform to 37.7±0.1×100?W/cm2,the error was only 0.2×100?W/cm2,and the device manufacturing precision was±0.05 mm.This was increased by 3.2%in the±0.05mm range and by 5.8%in the±0.1mm range.3.The molding process of the PMMA resin showed that the material forming precision was inversely proportional to the shrinkage rate,the Z-axis layer thickness and the ultraviolet light intensity.When the content of CNCs-Ag was 0.25 wt.%,the shrinkage of the composite decreases by 0.91%,the molding precision?±0.05mm?increases by 7.57%;when the content of Ti O2and PEEK was 1 wt.%and 3 wt.%,respectively,the shrinkage rate of the resin was reduced by 1.44%,and the forming precision?±0.05mm?was increased by 4.97%.when the Z-axis layer thickness was 25?m,the molding precision?±0.05mm?of CNCs-Ag/PMMA and Ti O2-KH570/PEEK/PMMA resin was 0.51%and 0.12%,respectively,higher than pure resin.When the Z-axis layer thickness was 50?m,molding precision for these two resins were increased by 0.96%and 0.71%,respectively,comparinting to PMMA resin.When the Z-axis layer thickness was 100?m,molding precision for these two resins were increased by 2.98%?2.57%,respectively,comparinting to PMMA resin.When UV intensity was 1700?W/cm2,the forming precision of CNCs-Ag/PMMA and Ti O2-KH570/PEEK/PMMA resins?±0.05mm?increased by 0.48%and0.14%than pure PMMA resin,respectively.When UV intensity was 2000?W/cm2,the forming precision of CNCs-Ag/PMMA and Ti O2-KH570/PEEK/PMMA resins?±0.05mm?increased by 0.82%and 0.71%than pure PMMA resin,respectively.When UV intensity was2300?W/cm2,the forming precision of CNCs-Ag/PMMA and Ti O2-KH570/PEEK/PMMA resins?±0.05mm?increased by 3.03%and 2.63%than pure PMMA resin,respectively.In this study,through the preparation of functional PMMA resin,personalized design of3D printing,improvement and integration of 3D printing equipment and molding process,a new technical scheme for the manufacture of PMMA composite denture base using DLP photocurable additive was proposed.It has been verified in this study that this personalized3D priting process showed good practicability and high efficiency. |
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