| IntroductionOral medicine is an important part of stomatology, it is a comprehensive and practical subject. Oral medicine practical operation is with high technical requirements, it requires dentists to have good overall knowledge and rich skilled operating experience which can significantly improve the clinical operating technical ability. Dental anatomy includes the tooth surface morphology and anatomy of the medullary cavity morphology. The tooth canal located inside the highly mineralized dentine, which has led to direct invisible, making the canal morphological study much more complex than the study of the tooth surface morphology. Currently teaching system in oral medicine, and operation simulating system, extracted teeth are most commonly used in exercises to improve oral medicine skills. However, because of the limitation in extracted teeth sources, unable to be duplicated, cross-infection, ethical issues and other reasons, extracted teeth can not be used for large scale operation training. Resin teeth, plastic pieces, are different with extracted teeth in tooth anatomy and simulatedness. So there is still a lack of alternative models which can be used for large-scale operation training and have high degree of simulation of extracted teeth.3D printing technology (Three-dimensional Printing) is carried out by three-dimensional digital model reconstruction and segmentation layered, layer by layer and then stacked to form a solid model. Its characteristics are precise, able to produce complex structures, personalization and mass production. Rapid progressing of materials science has made personalized 3D printing tooth model possible. Foreign scholars obtained complicated tooth image data with cone-beam CT (cone beam CT, CBCT),then use in analog operation and operation plan. However, it is still uable to simulate real teeth precisly. Thus,3D printing of the complex fine structure, ultra-high resolution image data is particularly critical.Micro-CT(micro-computed tomography)has several advantages such as high resolution, accurate positioning, repeatability and other characteristics. Micro-CT is widely used in recent years in oral medical research. Micro-CT has various orientation and angle which can display the anatomy of tooth surface and the pulp cavity, complex morphological characteristics, spatial position and the adjacent relations. Several researchs have used Micro-CT in oral scientific research. However, the use of micro-CT as the input source of 3D digital tooth printing digital model has not been reported.ObjectiveIn this study, we utilized human teeth extracted due to periodontal disease, integrated with micro-CT imaging technology to generate a 3D printed tooth model with a specific focus on anatomic fidelity instead of extracted tooth for dental training and preoperative surgical rehearsal.Materials and methods1. Major equipmentProJet 3510 HD 3D printing device (3D System, USA); DDP desktop 3D printing apparatus (EnvisionTEC, Germany); SCANCO ×CT80 (SCANCO Medical AG, Switzerland); ProMax 3D (Planmeca, Finland); Mimics 10.01 software (Materialise, Belgium); Geomagic Studio 11 software (Raindrop Geomagic, USA); Geomagic Qualify 11 software (Raindrop Geomagic, USA); Solid Works 2014 software (Dassault Systemes SA, United States).2. Method2.1 experimental specimen classification, treatment, screeningChoose good shape due to the removal of periodontal disease, caries-free, no defects extracted teeth 160, with 10% formalin soaking extracted teeth, removing the surrounding alveolar bone, periodontal ligament and calculus, shot with ProMax 3D CBCT models and filter out single root canal representative front teeth, the front double root canal teeth, double teeth root canals, three molar tube each one.2.2 micro-CT data obtainedSCANCO μCT80 performed using micro-CT scanning equipment, set energy of 70kV, strength of 114μA, with a resolution of 1024 pixels×1024 pixels, with layers 36μm pitch dental scan the entire length. When scanning, keep their teeth long axis perpendicular to the scanning plane, scanning from the apical to the cusp.2.3 to establish three-dimensional model of isolated teethThe micro-CT imaging Import 3D reconstruction software Mimics 10.01 software, create four types of dental 3D models.2.4 3D printing equipment and materials3D printing apparatus forming principle:Principle ProJet 3510 HD model is a multi-jet molding technology (Multi-Jet Manufacture, MJM), directly from the ejection head plastic instant freezing liquid and rapid prototyping.Rapid prototyping principle DDP models for digital light processing technology (Digital Light Processing, DLP), which uses a high-resolution Digital Light Processor projector curable liquid photopolymer layer by layer of light curing.3D printing material selection and the basic properties:Select adaptation Pro Jet 3510 HD model material is VisiJet Crystal, the material is transparent resin molding in Pro Jet 3510 HD models in the accuracy of 16μm, the support material is a paraffin wax.Select the type material is adapted DDP Wic300a and E-Dent, E-Dent tooth color with the color close, high hardness and rigidity, is available for dental crowns to repair 3D print of the photo-curable resin, biocompatible better, formed in the DDP models accuracy 100μm, support material for their own powder. Wic300a price is relatively cheap industrial resins, molding accuracy DDP for 25μm, support material for their own Wic300a powder.2.5 Canals Proficiency TestTest model design sketchSolidWorks 2014 software is a mechanical engineering design software, application software design Root Canals test model sketches, from small to large diameter of the root canal was 0.2mm,0.3mm,0.4mm,0.5mm,0.6mm,0.7mm, 0.8mm,0.9mm,1.0mm.3D printing test to get root canal modelWith Wic300a, E-Dent and Visijet Crystal 3D printing three materials design sketch Root Canals test model, the test model to obtain root canal.LED light irradiation testWith eight 3V LED retrofit bulbs and transformer manufacturing test light source is turned on, the three materials were irradiated root canal test models and shooting with the camera, observe the diameter of the lumen whether forming were determined using the three kinds of material 3D printing capability Root Canals.2.6 three-dimensional model modification of extracted teethAccording to Root Canals proficiency test results to determine the minimum root canal diameter can be formed with Mimics 10.01 software modification of extracted teeth three-dimensional model, and import Geomagic Studio 11 after storage software deal with STL format for the final three-dimensional model of extracted teeth.2.7 3D printed model of teethThree materials were used for four different types of teeth in vitro for 3D printing,3D printing to obtain the dental model, compare the appearance and outlook search root canal patency selected two kinds of material models to reverse engineer checking comparison.2.8 3D printing three-dimensional reconstruction of the dental modelThe two material microscopic model selected for the second CT scan imaging, 3D reconstruction with Mimics 10.01 Tooth 3D printed model.2.9 3D print simulation evaluation form tooth modelChecking the use of reverse engineering software Geomagic Qualify 11 is separated into the three-dimensional model of the surface morphology of 3D models and endosteal 3D models. Respectively, from the surface and endosteal two aspects of 3D printing three-dimensional model of the dental model with the three-dimensional model of isolated teeth do two two best-fit registration, setting teeth in vitro three-dimensional model as a reference model, the difference in magnitude registration on the difference map displayed by a different color, differences in the distribution of the reference color pictures can aid data analysis, digital anatomy reverse check to compare.Results1.Canals proficiency test resultsSuccessfully designed and manufactured Wic300a, E-Dent,3D VisiJet Crystal three materials print Root Canals test model, to meet the LED light irradiation experiment design requirements. Photographed image are analyzed and compared, the smallest diameter of the beam through the test pattern is 0.4mm Wic300a; minimum diameter E-Dent test pattern is 0.6mm, Visijet Crystal, test models of 0.8mm. Wic300a root canal forming the strongest, followed by the E-Dent, the worst is Visijet Crystal.2.obtained from extracted teeth and 3D printing model three-dimensional model Successfully established a single front tooth root canal, before the double root canal teeth, double teeth root canals, three dimensional model of the molar tube, transparent model treated surface morphology and endosteal clear and intuitive display, good continuity, and may be three-dimensional rotation.3.3D dental model PrintAccording to Root Canals proficiency test results, the three-dimensional model is modified so that the root canal is narrowest 0.6mm, to get the final three-dimensional model of isolated teeth. Combined with 3D printing technology successfully obtain a single root canal Anterior E-Dent, Wic300a, Visijet Crystal, the former double root canal molar, double root canal molars, the three root canal molar 3D printing teeth model, model 1:1 reduction of extracted teeth three-dimensional model. In natural light, intuitive form and are very close to real teeth, realistic effect, E-Dent model in terms of color and aesthetics closer to extracted teeth. Visijet Crystal model is apical ash clogged, do not use the material model form of reverse check to compare.4 3D printing surface morphology of the dental model accuracy analysis3D printing on the surface morphology of the dental model, Wic300a model set of standard error mean (0.008121±0.0480) mm,.E-Dent model set of standard error of mean (0.009554±0.0526) mm,.2.5 3D print model endosteal dental precision analysis3D model of the tooth canal print form, Wic300a model standard error of the mean for the group (0.04518±0.1022) mm. E-Dent model set of standard error of mean (0.056953±0.1995) mm.2 kinds of materials in the model group root molar model double standard tube before the smallest error.ConclusionThe study used a combination of microscopic three-dimensional CT reconstruction technique to construct a three-dimensional model of the tooth, not only provides an accurate three-dimensional data model for the 3D printing teeth, but also a more three-dimensional display of the anatomy of the tooth surface and the anatomy of the medullary cavity.3D printing technology has a better morphology demonstrated ability to meet internal build complex three-dimensional structural model of demand, combined with the advantages of the present study to build a 3D model to replace the print teeth extracted teeth, not only it can be applied to the tooth teaching anatomy, but also for complex clinical cases preoperative diagnosis and surgical simulation. In addition, the oral medicine can also be used on training, such as clinicians cavity filling technique, root canal therapy and other skills training. In this study, Geomagic Qualify 11 software on two kinds of material models and endosteal surface were simulated assessment and conclusion:The surface morphology (1) dental model, model group and two kinds of material extracted teeth better consistency and the same type of model teeth, two materials were no significant differences. (2) canal morphology, consistency Wic300a model group is acceptable, but the E-Dent model group consistency is poor, the same type of dental model group two materials significantly different. (3) Wic300a model standard error of the mean smaller group. Instructions,3D printing technology capacity forming surface morphology than endosteal strong, Wic300a on forming endosteal compared with E-Dent advantage, but E-Dent color appearance closer to the real teeth, two kinds of material 3D printing tooth model have their own advantages.However,3D printing tooth model at this stage still some defects and deficiencies. Since the apical hole diameter can reach 0.2mm,3D experiments in this study obtained in the pre-print dental root canal model is less clear, Visijet Crystal 3D printing model tooth apical closure, Wic300a and E-Dent were apical 1/ 3 segment clogged, so the model needs to be modified in order to print out the dental model. Root Canals proficiency test results show Wic300a Root Canals strongest, followed by the E-Dent, the worst is Visijet Crystal, precision three materials were 25μm, 100μm,16μm, DDP models supporting material for their own powder, ProJet 3510 HD models, compared with ash. Presumably, the root canal forming ability, and print material accuracy and ease of removal of the support material related to machine precision and higher support material more easily removed, the root canal shaping ability better, on the contrary, the root canal forming the worse. Because at this stage 3D printing materials and limit the overall level of development, is not yet a perfect copy of endosteal real teeth, but the problem in the near future will continue with the development of 3D printing technology and materials be resolved.In summary, in the term of anatomy, this 3D printing model serves as an excellent replica of human teeth for training and preoperative surgical rehearsal. |
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