Standard Triangulation Language Research Articles

Accuracy of intraoral scanners based on jaw curve and inter-implant distance

Background: In digital dentistry, the intraoral scanner (IOS) is the primary data-collecting device. The data must be accurate to prevent undesirable stresses and technological difficulties resulting from prosthetic misfits. The span length of restorations influences the accuracy of IOS impressions. Purpose: This research aimed to compare the accuracy of virtual models scanned by different IOSs to determine whether jaw curvature and inter-implant distance affect accuracy. Methods: Four mandibular edentulous models were prepared by replacing the site of the missing tooth with an implant. The prepared holes were drilled at 7mm, 14mm, 21mm, and 28mm. Five scans for each model were taken with a desktop laboratory scanner as a reference model and with Trios3Shape and 3Disc Heron IOSs to evaluate trueness and precision (T&P). The scans were saved as standard triangulation language files and statistically analyzed at a level of significance (P ≤ 0.05). Results: There was a significant difference between the IOSs in inter-implant distances (P < 0.05). The greatest distortion was reported in the 21mm and 28mm groups for both scanners (P ≤ 0.05), while the lowest distortion was observed in the 7mm and 14mm groups for the Trios3Shape scanner. Conclusion: Jaw curvature and inter-implant distance impacted the accuracy of the IOS. Distortion and reduced reproducibility of T&P increased with jaw curve and inter-implant distance. The Trios3Shape IOS showed maximum accuracy at 7mm and 14mm inter-implant distances, while the 3Disc Heron IOS produced significant distortion of trueness at 21mm and 28mm inter-implant distances.

Virtual surgical planning in orthognathic surgery: A prospective evaluation of postoperative accuracy

ObjectivesThe development of 3D computer-assisted technologies over the past years has led to vast improvements in orthognathic surgery. The aim of the present study was to evaluate differences in maxillary position between 3D virtual surgical planning (VSP) and surgical results. Materials and methodsWe assessed data from 25 patients who underwent bimaxillary non-segmented orthognathic surgery with 3D VSP. Each patient underwent a postoperative CT scan within 40 days after surgery. We compared the STL (Standard Triangulation Language) file from the VSP with that obtained from the postoperative CT. ResultsAccording to our comparative analysis, the postoperative and VSP 3D models did not statistically differ. The Lin concordance correlation coefficient was always >0.95 for each landmark, but in 21 patients (84 % of the sample) we identified at least one point with a difference of more than 1.5 mm between the postoperative and VSP 3D model on at least one axis. The most frequently observed differences corresponded to sagittal translation and pitch rotation. ConclusionsAn intraoperative clinical and aesthetic evaluation of the consequences of bone movements on patient face is strongly recommended, also when we use VSP because we may have clinically significant differences from the planning.

3D-printed tool for creating standardized burn wounds in ex vivo skin tissues

IntroductionThe development of biomaterials and medical devices for burn wound treatment necessitates thorough investigation through in vitro/ex vivo models before transitioning to animal studies. Establishing a standardized and high-throughput burn wound model in ex vivo skin presents a considerable challenge. Our objective was to address this challenge by developing a practical and cost-effective 3D-printed burn wound tool capable of uniformly inducing burns in 12 skin samples simultaneously. Material and methodsUtilizing Autodesk Inventor software, we designed a 3D model comprising a plate-base component (PBC) and a rod-base component (RBC). The design was exported as a Standard Triangulation Language (STL) file, processed through "Slicer" software to generate a G-code file tailored for 3D printing. ResultsThe Rod-Base component underwent iterative design modifications to optimize weight, airflow, and material consumption, resulting in a final design featuring a unique star shape for enhanced airflow. Simultaneously, the Plate-Base component design evolved to enable easy and secure plate placement, demonstrating compatibility with 12-well plates. The average production time for the model was 14.5 h, with a production cost of approximately $20 (USD), covering printing material and steel rods. ConclusionIn conclusion, this study provides valuable insights into the required equipment and software, empowering researchers to efficiently produce their accurate and cost-effective 3D-printed tool for controlled and reproducible burn wound creation in ex vivo viable skin tissues.

Digital planning and bone regenerative technologies: A narrative review.

The aim of this narrative review was to explore the application of digital technologies (DT) for the simplification and improvement of bone augmentation procedures in advanced implant dentistry. A search on electronic databases was performed to identify systematic reviews, meta-analyses, randomized and non-randomized controlled trials, prospective/retrospective case series, and case reports related to the application of DT in advanced implant dentistry. Seventy-nine articles were included. Potential fields of application of DT are the following: 1) the use of intra-oral scanners for the definition of soft tissue profile and the residual dentition; 2) the use of dental lab CAD (computer-aided design) software to create a digital wax-up replicating the ideal ridge and tooth morphology; 3) the matching of STL (Standard Triangulation Language) files with DICOM (DIgital COmmunication in Medicine) files from CBCTs with a dedicated software; 4) the production of stereolithographic 3D models reproducing the jaws and the bone defects; 5) the creation of surgical templates to guide implant placement and augmentation procedures; 6) the production of customized meshes for bone regeneration; and 7) the use of static or dynamic computer-aided implant placement. Results from this narrative review seem to demonstrate that the use of a partially or fully digital workflow can be successfully used also in advanced implant dentistry. However, the number of studies (in particular RCTs) focused on the use of a fully digital workflow in advanced implant dentistry is still limited and more studies are needed to properly evaluate the potentials of DT.

Rapid prototyping: A future in orthodontic

<abstract> <p>The term “rapid prototyping” (RP) refers to a variety of methods for creating “physical models based on computer-aided design and computer-aided manufacturing”. With the aid of RP technology, practically any variation of the surface and interior anatomical structure may be replicated in a medical model that is constructed layer by layer. To create the physical model, layer-by-layer construction is carried out using a variety of processes, including stereolithography, selective laser sintering, inkjet printing, and fused deposit modeling. Data for RP is received from magnetic resonance imaging and computed tomography scans, which are then turned into digital images and then into standard triangulation language files. The use of this computerized programming in orthodontics incorporates “diagnosis and treatment planning”, the creation of removable “orthodontic appliances”, “impression trays” for indirect bonding, “3D printed occlusal splints and aligners”, prototype models used in various orthognathic surgeries, and the production of a distractor for distraction osteogenesis. It increases a crucial understanding at the time of preoperative treatment planning and raises the effectiveness of the therapy, yet, clinical judgment is still essential. Applications of RP for an orthodontist vary, and if we utilize it creatively, the future appears more hopeful. This article briefly reviews key advancements, challenges, and prospects in the integration of rapid prototyping and 3D printing, shaping a promising future for orthodontics.</p> </abstract>

Development of patient-specific 3D printed implants for total knee arthroplasty

Aim: Arthritis is a degenerative condition characterized by the progressive deterioration of the knee joint, leading to aches, rigidity, and decreased mobility. Total knee arthroplasty (TKA) surgery is performed to alleviate pain for restoring activity in these patients. TKA is carried out due to natural wear of the cartilage and meniscus or by sudden impact at the knee joint area. The surgical procedure involves careful planning, precise bone cuts, and insertion of artificial components made of metal alloys and high-density polyethylene. However, conventional manufacturing of customized knee implants involves time and cost. This work aims to present the application of three-dimensional (3D) printing for developing individualized knee implants for TKA and the challenges faced during it. Methods: Morphometry of the knee joint varies among different populations, including Indian and Western, which pose challenges during the surgery as accurate alignment and implant sizing are crucial for optimal outcomes. A female patient’s pre-surgery computed tomography (CT) scan is considered to identify the disease and to find region of interest (ROI) such as knee joint. Process involves converting scanned data to a file format for 3D printing via computer-aided design (CAD). Results: The patient’s CT scan data is processed to obtain the CAD models of knee joint and standard triangulation language (STL) file. Additional geometries and noise present near the region are removed to get ROI. Open loops and overlapping triangles are rectified in the STL file. Based on the morphometry of the bone, resection is done to obtain the CAD models of knee implants. 3D printing of the knee joint and implant prototypes is then obtained using fused deposition modelling (FDM). Line layers on the printed implant prototype are seen. Conclusions: Patient-specific 3D printed knee joint implant prototypes are successfully obtained using FDM. Challenges faced during the work are successfully worked out.

Preoperative interactive virtual simulation applying three-dimensional multifusion images using a haptic device for lumbosacral lipoma.

Untethering surgery for lumbosacral lipoma is a preventive procedure, and avoidance of complications and good long-term outcomes are required. We introduced presurgical interactive virtual simulation (IVS) applying three-dimensional multifusion images using a haptic device aimed at improving operative outcomes. Fourteen patients with newly diagnosed lumbosacral lipoma were recruited and underwent preoperative IVS. The median age at surgery was 8 months. A three-dimensional image analysis system was used to extract and fuse structures necessary for surgery, such as the lipoma, spinal cord and skin, from CT and MRI, and create three-dimensional multifusion images. The created images were individually converted to standard triangulated language format and loaded onto a workstation (Geomagic freeform™) that could be freely transformed, and the laminectomy range and lipoma extraction procedure were examined. Presurgical IVS was performed, and the actual surgery was performed. The disease types were dorsal, caudal, lipomyelomeningocele, transitional, and filum in 5, 5, 2, 1, and 1 patients, respectively. The surgical procedure and extent of the laminectomy were as planned for all patients. Resection of the lipomas tended to be less than expected preoperatively because of positive reactions on intraoperative monitoring. No postoperative complications were observed. The median postoperative follow-up period was 29 months, and there were no reoperations during the observation period. Although there are various types of lumbosacral lipoma, surgery can be safely performed by performing presurgical IVS. The short-term course is good; however, long-term follow-up is necessary for the appearance of neurological symptoms associated with growth and re-tethering.

Automated Process Planning System for Machining Injection Molding Dies Using CAD Models of Product Shapes in STL Format

In this study, we developed a method for automatically generating computer-aided design (CAD) models of injection molding dies. The method only required 3D CAD models of products in the Standard Triangulated Language (STL) format as the input information. We also developed a system for automatically generating numerical control (NC) programs by automating the system process planning necessary for machining the injection molding dies. The method generated CAD models of the injection molding dies by dividing the STL files of the products into triangular meshes on a specified split plane. For injection molding dies with several free curved surfaces, we acquired the tool positions of a ball end mill (as approximated by a spherical shape) and flat drill (as approximated by a cylindrical shape) from the geometrical relationships of the triangles constituting the CAD model. We generated a CAD model of an injection molding die using the proposed method with respect to the CAD model of a product shape to verify the validity of the developed system. Then, we machined the product based on the NC programs and tool position. In addition, we injection molded a product with a machined die to mold it into its original product shape.

3D 프린팅 출력물을 위한 3D 모델링의 오류 분석과 해결방안

Digital technology has attempted to blur the boundaries between architectural design and fabrication, which have been established since the Renaissance. However, these boundaries still exist, due to the discontinuity between digital modeling and fabrication, which often derives from errors encountered in the process of file conversion. To bridge this discontinuity, this study intends to identify and analyze the causes of errors during the process of converting 3D modeling to Standard Triangulated Language (STL) file, and then to provide solutions that fix the errors. The STL file errors are results of failing to understand or ignoring the difference between 3D modeling for 3D printing and for visual presentation. For this reason, this study conducted an error analysis using Materialize Magics (STL editing and repairing software) to investigate types of the errors and to suggest ways of repairing 3D modeling with such errors.

Accuracy of optical interocclusal registration using an intraoral scanner.

This study aimed to clarify the effect of occlusal force on appropriate optical interocclusal registration in clinical practice, considering periodontal ligament and jawbone deformation. Forty participants with natural, healthy dentition were enrolled (19 men and 21 women; mean age, 27.7 ± 2.0 years). A TRIOS3 intraoral scanner was used to scan the right lateral first premolar to the second molar areas of the upper and lower jaws. During scanning for interocclusal registration, participants were instructed to "bite normally," "bite lightly," and "bite strongly" to obtain data for the three occlusal patterns. The standard triangulated language (STL) data for each occlusion condition were superimposed using the appropriate software, following which the tooth displacement was calculated. The conventional method was also used to record the occlusal contact area for a silicone model using a dental contact analyzer. Tooth displacement was significantly lower for the strong-bite condition than for the weak-bite condition (0.018 mm vs. 0.028 mm, P<0.05). As the occlusal force increased, the occlusal contact area also increased, and significant differences were observed among the different occlusal conditions (P<0.05). Occlusal contact area changed depending on the bite force when using the silicone impression or optical intraoral scanning methods. Moreover, using optical impression methods in "strong bite force" may reduce the deviation and allow for stable interocclusal registration.

Prediction accuracy of incisal points in determining occlusal plane of digital complete dentures.

This study aimed to predict the positional coordinates of incisor points from the scan data of conventional complete dentures and verify their accuracy. The standard triangulated language (STL) data of the scanned 100 pairs of complete upper and lower dentures were imported into the computer-aided design software from which the position coordinates of the points corresponding to each landmark of the jaw were obtained. The x, y, and z coordinates of the incisor point (XP, YP, and ZP) were obtained from the maxillary and mandibular landmark coordinates using regression or calculation formulas, and the accuracy was verified to determine the deviation between the measured and predicted coordinate values. YP was obtained in two ways using the hamular-incisive-papilla plane (HIP) and facial measurements. Multiple regression analysis was used to predict ZP. The root mean squared error (RMSE) values were used to verify the accuracy of the XP and YP. The RMSE value was obtained after cross-validation using the remaining 30 cases of denture STL data to verify the accuracy of ZP. The RMSE was 2.22 for predicting XP. When predicting YP, the RMSE of the method using the HIP plane and facial measurements was 3.18 and 0.73, respectively. Cross-validation revealed the RMSE to be 1.53. YP and ZP could be predicted from anatomical landmarks of the maxillary and mandibular edentulous jaw, suggesting that YP could be predicted with better accuracy with the addition of the position of the lower border of the upper lip.

Analysis of additive manufacturing techniques used for maxillofacial corrective surgeries

Patients with jaw deformities often lead a poor quality of life due to problems encountered during speech, mastication and aesthetics, which makes maxillofacial reconstructive/corrective surgery necessary. Surgeons find difficulty in visualizing complex facial anatomy; therefore, a method of viewing a physical 3D maxillofacial model is highly beneficial. Accurately reproduced 3D models of a patient’s maxillofacial structure assist in pre-planning of a surgical procedure. AM (Additive Manufacturing) allows effective reproduction of a digital image into a physical model, replicating actual facial anatomy, thereby providing an effective solution. Among the AM techniques, PolyJet, FDM (Fused Deposition Modelling), SLA (Stereolithography) and SLS(Selective-Laser-Sintering) are being used for such applications. Comparison of these techniques is presented to determine the most efficient technique in reproducing such models for dimensional accuracy and cost. 20 models of five patients with deformed maxillofacial structures were designed using CAD (Computer-Aided Design) from STL (Standard Triangulation Language) files obtained from CT (Computerized Tomography) scans, which were manufactured using the aforementioned techniques. These models were then analysed for dimensional accuracies by identifying nine critical landmarks within the maxillofacial structures. Overall weight of the models was also evaluated for a cost-effective manufacturing solution. Dimensional measurement results of the 3D printed models indicated a relative error trend as PolyJet&lt;SLA&lt;SLS&lt;FDM while material cost expenditure involved during 3D printing of these models indicated a trend as FDM&lt;PolyJet&lt;SLA&lt;SLS, thereby recommending PolyJet as the most favoured AM technique for reproducing a maxillofacial structure. As a best practices guideline, incorporating AM for complex bone reconstruction procedures results in improved dimensional accuracies, reduced intraoperative time, reduced patient’s exposure to anaesthesia and ultimately an improved aesthetic outcome to the patient.

Three-Dimensional (3D) Stereolithographic Tooth Replicas Accuracy Evaluation: In Vitro Pilot Study for Dental Auto-Transplant Surgical Procedures.

After immediate tooth extraction or after alveolar socket healing, tooth transplants are increasingly used for functional restoration of edentulous maxillary areas. Recent studies have shown the periodontal ligament (PDL) viability and the tooth housing time in the adapted neo-alveolus as key factors for transplantation success. During surgical time, 3D stereolithographic replicas are used for fitting test procedures. In this paper, the accuracy of 3D dental replicas, compared with the corresponding natural teeth, is assessed in surgical transplantation. Lamb skulls were selected and submitted to Cone Beam Computer Tomography (CBCT). Scanning information, converted into Standard Digital Imaging and Communications in Medicine (DICOM) and Standard Triangulation Language (STL), was sent to the Volux X-ray Centre for 3D replica printing. After the tooth extractions, all lambs’ incisors were measured with a digital caliber and compared with the 3D replicas. Volume and dimensional error values were evaluated. All replicas showed macroscopically smaller volume (45.54%). Root replicas showed higher variations compared with the crown areas, with several unreplicated apical root areas. The cement–enamel junction tooth area was replicated quite faithfully, and the base area relative error showed 9.8% mean value. Even further studies with a larger number of replicas are needed. Data obtained confirmed high volumes of macroscopic discrepancies with several unreproduced apical root sites. The achieved accuracy (90.2%) confirmed that the 3D replicas cannot be used to reduce the surgical time during transplantation predictable procedures.

Comparison of digital and silicone impressions for single-tooth implants and two- and three-unit implants for a free-end edentulous saddle

BackgroundThe use of intraoral scanners (IOS) has facilitated the use of digital workflows for the fabrication of implant-supported prostheses not only for single missing teeth, but also for multiple missing teeth. However, the clinical application of IOS and computer-aided design/manufacturing (CAD/CAM) in implant-supported prosthodontics remains unclear. This study aimed to compare the accuracy of digital and silicone impressions for single-tooth implants for bounded edentulous spaces and two-unit and three-unit implant-supported fixed dental prostheses for free-end edentulous spaces.MethodsThis study enrolled 30 patients (n = 10 for each of the three groups) with an average age of 61.9 years. Conventional silicone-based and digital IOS-based impressions were made for all patients, and the implant superstructures were fabricated. We measured the scan-body misfit and compared the accuracy of the impressions for single-unit, two-unit, and three-unit implant prostheses with a bounded edentulous space by superimposing the standard triangulated language (STL) data obtained from IOS over the STL data of the plaster model used for final prosthesis fabrication. The scan bodies of the superimposed single-molar implant, two-unit implant prosthesis without teeth on the mesial side, two-unit implant prosthesis without teeth on the distal side, three-unit implant prosthesis without teeth on the mesial side, and three-unit implant prosthesis without teeth on the distal side were designated as A, B1, B2, C1, and C2, respectively. The misfit for each scan body was calculated and the accuracies were compared using the Tukey–Kramer method.ResultsThe average scan-body misfit for conditions A, B1, B2, C1, and C2 was 40.5 ± 18.9, 45.4 ± 13.4, 56.5 ± 9.6, 50.7 ± 14.9, and 80.3 ± 12.4 μm, respectively. Significant differences were observed between the accuracies of A and B2, A and C2, and C1 and C2 (P < 0.001).ConclusionsIOS and CAD/CAM can find clinical applications for implant-supported prostheses of up to three units for a bounded edentulous saddle. The use of IOS could render implant treatment easier, benefiting both the surgeons and patients. Prosthesis maladjustment may lead to peri-implantitis and prosthetic fracture. Therefore, further validation of the accuracy of IOS impressions is required in patients with multiple missing teeth in long-span implant prostheses.

Comparison of three-dimensional facial morphologies acquired with digital stereophotogrammetry imaging system and computed tomography

ObjectiveThe aim of this study was to compare the characteristics of 3D facial images obtained by multi-detector computed tomography (MDCT) and stereophotogrammetry and to determine whether both methods can be integrated with accurate analysis in the same coordinate system for treatment planning and postoperative assessment in orthognathic surgery. MethodsThe subjects were 20 patients with jaw deformities. All of the patients underwent MDCT and stereophotogrammetry examinations for the assessment of maxillofacial morphologies before treatment. Standard triangulated language (STL) data of 3D facial surface images obtained by using MDCT and stereophotogrammetry were superimposed with four landmarks and the forehead and nasion area by a best-fit algorithm. The differences in Z coordinate values (mm) at ten measurement points and in six measurment volumes (cm3) between images obtained by using MDCT and stereophotogrammetry were calculated. Differences in Z coordinate values at the central measurement points were within 1 mm, but differences at the lateral measurement points, especially lower points, were significantly large. The volumes using MDCT were smaller than those using stereophotogrammetry, especially at lateral regions. Mean differences at the central measurement volumes were within 1 cm3, but mean differences at the lateral measurement volumes, ranging from 1.6 cm3 to 3.5 cm3, were comparatively large. In conclusion, the method presented for 3D superposition of images obtained from different modalities may be useful for treatment planning and postoperative evaluation of orthognathic surgery.

Peri-implant tissue augmentation by volume-stable collagen matrix transplantation: a study of dog mandibles.

The aim of this study was to investigate histologically the amount of peri-implant tissue augmentation after volume-stable porcine collagen matrix transplantation. Six male beagle dogs were used in the experiment. P2, P4, and M1 distal roots were extracted under general anesthesia. After 6months, implants were placed in the same sites, and volume-stable porcine collagen matrix transplantation was performed. Impressions were taken at 1 and 2weeks and at 1, 2, and 3months after transplantation. The dogs were euthanized at 3months, and their mandibles were removed and scanned using micro-computed tomography. Standard Triangulated Language data were also obtained. Using preoperative models as a reference, the data for all time points were compared, and changes in the thickness of the cross-section of the implant sites were measured. The model created at 3months was then compared with the mandible data, and the thickness of collected peri-implant soft tissue was measured under optical microscopy. Increased thickness was found at some of the sites on the buccal side. Regarding the peri-implant soft tissue, the thickness of the measured sites on the buccal side was significantly increased at 3months in the experimental group. Histological observations of the internal structures of the tissue in the experimental group revealed irregular collagen fibers and a remnant collagen matrix. Endogenous tissue was observed within the collagen matrix, indicating good fusion with the surrounding autologous tissue. These results suggest that volume-stable porcine collagen matrix transplantation promotes peri-implant tissue augmentation on the buccal side.

SCARLET-1.0: SpheriCal Approximation for viRtuaL aggrEgaTes

Abstract. Aggregation of particles occurs in a large variety of settings and is therefore the focus of many disciplines, e.g., Earth and environmental sciences, astronomy, meteorology, pharmacy, and the food industry. In particular, in volcanology, ash aggregation deeply influences the sedimentation of volcanic particles in the atmosphere during and after a volcanic eruption, affecting the accuracy of model predictions and the evaluation of hazard and risk assessments. It is thus very important to provide an exhaustive description of the outcome of an aggregation process, starting from its basic geometrical features such as the position in space of its components and the overall porosity of the final object. Here we present SCARLET-1.0, a MATLAB package specifically created to provide a 3D virtual reconstruction for volcanic ash aggregates generated in central collision processes. In centrally oriented collisions, aggregates build up their own structure around the first particle (the core), acting as a seed. This is appropriate for aggregates generated in turbulent flows in which particles show different degrees of coupling with respect to the turbulent eddies. SCARLET-1.0 belongs to the class of sphere-composite algorithms, a family of algorithms that approximate 3D complex shapes in terms of a set of sphere-composite nonoverlapping spheres. The conversion of a 3D surface to its equivalent sphere-composite structure then allows for an analytical detection of the intersections between different objects that aggregate together. Thus, provided a list of colliding sizes and shapes, SCARLET-1.0 places each element in the vector around the core, minimizing the distances between their centers of mass. The user can play with different parameters that control the minimization process. Among them the most important ones are the cone of investigation (Ω), the number of rays per cone (Nr), and the number of orientations of the object (No). All the 3D shapes are described using the Standard Triangulation Language (STL) format, which is the current standard for 3D printing. This is one of the key features of SCARLET-1.0, which results in an unlimited range of applications of the package. The main outcome of the code is the virtual representation of the object, its size, porosity, density, and the associated STL file. In addition, the object can be potentially 3D printed. As an example, SCARLET-1.0 has been applied here to the investigation of ellipsoid–ellipsoid collisions and to a more specific analysis of volcanic ash aggregation. In the first application we show that the final porosity of two colliding ellipsoids is less than 20 % if flatness and elongation are greater than or equal to 0.5. Higher values of porosities (up to 40 %–50 %) can instead be found for ellipsoids with needle-like or extremely flat shapes. In the second application, we reconstruct the evolution in time of the porosity of two different aggregates characterized by different inner structures. We find that aggregates whose population of particles is characterized by a narrow distribution of sizes tend to rapidly reach a plateau in the porosity. In addition, to reproduce the observed densities, almost no compaction is necessary in SCARLET-1.0, which is a result that suggests how ash aggregates are not well described in terms of the maximum packing condition.

Design of a Single-Tooth Model and Its Application in Oral Scan System Assessment

Intraoral scanners have been widely used in the application of dentistry. Accuracy includes trueness and precision; they have an important position in the assessment of intraoral scanners. The existing standard models are divided into the inlay and the crown, but the operation is relatively complicated. In this study, in order to simplify the current standard model, we designed a new integration model to compare the accuracy of two intraoral scanners (CEREC and TRIOS) and an extraoral scanner (SHINING). The coordinate measuring machine measured value is the gold standard. Values of the length and angle were analyzed by converting the scanned digital impressions into an STL (standard triangulation language) format to evaluate the accuracy of the intraoral scanner and to verify the feasibility of the designed model. The result shows that the integration model can be successfully scanned and imaged. In the case of the powder-free integration model, intraoral scanner precision, trueness, 3D fitting, and imaging are better than the extraoral scanner. It can be seen straightly from the measurement result and the 3D fitting result that the intraoral scanner can acquire the shape of the standard model integrally with good repeatability. Therefore, it can be concluded that TRIOS is superior to CEREC and SHINING in accuracy, and the integration model is feasible as a reference in the examination of intraoral scanners. The performance of the newly designed integration model that can be scanned is clinically significant, suggesting that this model can be used as a standard reference model.

3D Printing of Rapid, Low-Cost and Patient-Specific Models of Brain Vasculature for Use in Preoperative Planning in Clipping of Intracranial Aneurysms.

We developed a practical and cost-effective method of production of a 3D-printed model of the arterial Circle of Willis of patients treated because of an intracranial aneurysm. We present and explain the steps necessary to produce a 3D model from medical image data, and express the significant value such models have in patient-specific pre-operative planning as well as education. A Digital Imaging and Communications in Medicine (DICOM) viewer is used to create 3D visualization from a patient’s Computed Tomography Angiography (CTA) images. After generating the reconstruction, we manually remove the anatomical components that we wish to exclude from the print by utilizing tools provided with the imaging software. We then export this 3D reconstructions file into a Standard Triangulation Language (STL) file which is then run through a “Slicer” software to generate a G-code file for the printer. After the print is complete, the supports created during the printing process are removed manually. The 3D-printed models we created were of good accuracy and scale. The median production time used for the models described in this manuscript was 4.4 h (range: 3.9–4.5 h). Models were evaluated by neurosurgical teams at local hospital for quality and practicality for use in urgent and non-urgent care. We hope we have provided readers adequate insight into the equipment and software they would require to quickly produce their own accurate and cost-effective 3D models from CT angiography images. It has become quite clear to us that the cost-benefit ratio in the production of such a simplified model is worthwhile.

Automated Process Planning System for End-Milling Operation by CAD Model in STL Format

A method for extracting the machining region from a 3D CAD model in Standard Triangulated Language (STL) format and automatically generating a tool path is proposed. First, a method is proposed for extracting the machining region and obtaining the geometrical features such as a convex or concave shape from only the 3D CAD model in STL format. The STL format uses only triangular mesh data and drops all information, which is necessary for extracting the removal volume for the machining and geometrical characteristics. Furthermore, the triangular mesh size is non-uniform. A contour line model is proposed in which the product model is minutely divided on the plane along any one axial direction and is represented by points at intervals below the indicated resolution obtained from the contour line of the cross section of the product. Subsequently, a method is proposed to determine the machining conditions for each extracted machining region and automatically generate a tool path according to the geometrical features of the machining region obtained. A machining experiment was conducted to validate the effectiveness of the proposed method. As a result of the machining experiment, it was confirmed that the tool path automatically generated from the 3D CAD model in STL format can be machined without any problems and with a practical level of accuracy.