Stereolithography File Research Articles

Evaluating the accuracy of intraoral direct digital impressions in 2 infants with unilateral cleft lip and palate compared with digitized conventional impression

Presurgical infant orthopedics was introduced as an interceptive approach for treating cleft lip and/or palate (CLP). This study aimed to evaluate the intraoral digital impression technique as a viable alternative to conventional impression in infants with unilateral CLP. Trios 3-Shape scanner (3Shape, Copenhagen, Denmark) was used for intraoral scanning of the infants' maxillary arches to provide a direct digital scan (DDS). In addition, conventional impressions of the same patients were taken in a hospital setting, and the resultant stone models were digitized using the same scanner to create an indirect digital scan (IDS). Both scans (DDS and IDS) were exported in stereolithography format, and the resultant stereolithography files were imported into computer-assisted-design software (Exocad DentalCAD; exocad GmbH, Darmstadt, Germany) for 3-dimensional surface model superimposition. Differences between the 2 surfaces were quantified in millimeters and visually displayed by a color map. Three-dimensional surface model superimposition of the DDS and IDS scans showed an excellent agreement between both approaches, in which differences ranged from 0.01 mm to 0.1 mm CONCLUSIONS: Intraoral direct digital impression in infants with unilateral CLP is a safe, accurate, and time-efficient technique, which can be a viable alternative to conventional impression. This will aid in overcoming the challenges and complications that are frequently associated with using conventional impressions in infants with unilateral CLP, thus reducing the burden of care not only on the patients' families but also on the care providers.

Using Blockchain to Protect 3D Printing from Unauthorized Model Tampering

As three-dimensional (3D) printing technology is widely used, security issues have arisen, especially in the terminal parts of automobiles, aircraft, and 3D-printed military equipment. If the original design models or the STL (stereolithography) files are hacked or tampered, severe consequences can be anticipated. In this paper, we propose a demonstration to use a high-throughput blockchain to store the “fingerprints” of the 3D model and verify the “fingerprints” before printing to prevent illegal tampering. Relying on the tamper-resistant features of blockchain, the security of the model and the credibility of the terminal components can be ensured. The combination of blockchain and 3D printing will help people to build a trusted manufacturing environment and realize a more flexible manufacturing for future industry.

Stereolithography (STL) measurement rubric for the evaluation of craniomaxillofacial STLs

BackgroundFacial deformities often demand reconstructive surgery and the placement of three-dimensional (3D) printed craniomaxillofacial prostheses. Prostheses manufacturing requires patients’ computed tomography (CT) images. Poor quality images result in incorrectly sized prostheses, necessitating repeat imaging and refitting. The Centre for Rapid Prototyping and Manufacturing (CRPM) produces most facial prostheses in South Africa but does not have a prescribed optimised CT protocol. Therefore, this study was undertaken.MethodsA collection of CRPM STLs used in the design and manufacturing of craniomaxillofacial prostheses is available. The image quality of stereolithography (STL) files of CRPM CT scans was evaluated to determine what constitutes good image quality. This collection was scrutinised for inclusion in the image quality evaluation. After scrutiny, 35 STLs of individuals ≥15 years of age were selected and included metadata attached to the DICOM file. Furthermore, only STLs created without manipulation by the same designer were included in the collection. Before the qualitative evaluation of the STLs, eight different critical anatomical reference points (CARPs) were identified with the assistance of an expert team. A visual acuity rating scale of three categories was devised for each CARP, where 1 was allocated to poor visual acuity, 2 to partial, and 3 to good visual acuity. Similarly, rating scales were devised for the presence of concentric rings and the overall impression score awarded by the two designers involved in the design and manufacturing of the prostheses. This stereolithography measurement rubric (SMR) was then applied to the 35 STLs by a team of three experts, including the two designers, during a structured evaluation session. The scores were used to calculate summary and inferential statistics.ResultsScores grouped around the central rating of partial visual acuity. The three evaluators’ mean total CARP scores ranged from 13.1 to 14.4 (maximum possible score 24), while the mean total CARP + ring scores ranged from 15.8 to 17.1 (maximum possible score 27). No significant differences were detected between the evaluators’ scores.ConclusionThis SMR appears to be the first of its kind. This image quality assessment of STLs provides the groundwork for finer CT image quality evaluation to formulate a CT imaging protocol for the CRPM to design and manufacture accurate internal cranial prostheses.

Effect of Ambient Lights on the Accuracy of a 3-Dimensional Optical Scanner for Face Scans: An In Vitro Study.

Most 3D scanners use optical technology that is impacted by lighting conditions, especially in triangulation with structured-light or laser techniques. However, the effect of ambient lights on the accuracy of the face scans remains unclear. The purpose of this study is to investigate the effect of ambient lights on the accuracy of the face scans obtained from the face scanner (EinScan Pro 2X Plus, Shining 3D Tech. Co., LTD., Hangzhou, China). A head model was designed in Rhinoceros 5 software (Rhino, Robert McNeel and Associates for Windows, Washington DC, USA) and printed with 200 micron resolution of polylactic acid and was dented with 2.0 mm of carbide bur to aid in superimposition in software. The head model was measured by a coordinate-measuring machine (CMM) to generate a reference stereolithography (STL) file as a control. The face model was scanned four times under nine light conditions: cool white (CW), warm white (WW), daylight (DL), natural light (NL), and illuminant (9w, 18w, 22w). Scan data were exported into an STL file. The scan STL files obtained were compared with the reference STL file by 3D inspection software (Geomagic Control X version 17, Geomagic, Morrisville, NC, USA). The deviations and root mean square errors (RMSEs) between the reference model (trueness) and within the group (precision) were selected for the statistical analysis. The statistical analysis was done using SPSS 20.0 (IBM Company, Chicago, USA). The trueness and precision were evaluated with the one-way ANOVA with multiple comparisons using the Tukey method. For trueness, the scanner showed the lowest RMSE under the NL group (77.18 ± 3.22) and the highest RMSE under the 18w-DL group (95.33 ± 6.89). There was a statistically significant difference between the NL group and the 18w-DL group (p < 0.05) for trueness. Similarly, for precision, the scanner showed the lowest RMSE under the NL group (56.92 ± 4.56) and the highest RMSE under the 9w-CW group (78.52 ± 10.61). There was statistically significant difference between NL, 18w-WW, 18w-CW, 18w-DL, 22w-WW, 22w-DL, 9w-CW, 9w-WW, and 9w-DL (p < 0.05) for the precision. Ambient lights affected the face scans. Under the natural light condition, the face scanner had the best accuracy in terms of both trueness and precision. The 18w-DL and 9w-WW conditions showed the least trueness whereasthe 9w-CW and 9w-DL conditions showed the least precision.

Accuracy of Orthodontic Indirect Bracket Bonding by CAD/CAM Transfer Tray

Introduction: Indirect bonding is a technique in which orthodontic attachments are transferred from dental casts (working models) and bonded onto dentition using a transfer tray. Indirect bonding is a preferred technique for many orthodontists as it is less time consuming compared to direct bonding. Evolution in technology allowed forming transfer trays digitally by the integration of computer-aided design and computer-aided manufacturing (CAD/CAM). This study was conducted to measure transfer accuracy of CAD/CAM indirect three dimensional printed bonding trays. Materials and methods: 140 teeth (all upper and lower incisors, canines and premolars) in 7 patients were bonded by vacuum-formed transfer tray formed on 3 dimensional (3D) printed models with resin brackets. Intra oral scanner was used initially to obtain stereolithographic file for virtual brackets positioning and another scan was taken after brackets bonding. Superimposition of virtual STL files and post bonding STL files was done by Geomagic Qualify software to measure linear and angular deviation of brackets positions. Results: One sample t-test was performed to determine whether the mean transfer error was statistically within the selected acceptable limits of 0.5 mm for linear measurements. P-values of less than 0.05 indicated differences within the limits of 0.5 mm for linear measurements. All brackets were transferred within the accepted deviation limits Conclusions: CAD/CAM designed and printed transfer trays had high transfer accuracy in linear measurements in all teeth.

Pontic site development for fixed dental prostheses with and without soft tissue grafting: 1-year results of a cohort study

AimTo describe and compare the pontic site development for fixed-dental prostheses (FDPs) with and without soft tissue grafting up to one-year post insertion of FDPs.Materials and methodsA convenience sample of 24 patients participating in an ongoing RCT was provided with three-unit tooth-borne FDPs. Six patients received a subepithelial connective tissue graft (SCTG) at the pontic site, whereas 18 patients were treated without any soft tissue graft (CONTROL). Digital impressions were taken prior to tooth preparation, after tooth preparation, after insertion of the final FDP, and at the 1 year of follow-up. The obtained stereolithography files (STL) were superimposed and profilometric as well as linear changes of the soft tissue profile were assessed at the pontic regions. Profilometric outcomes included changes of the ridge contour, the alveolar ridge width, and the crown height of the pontic. Further outcomes assessed included: the papilla index, the pink esthetic score (PES), probing depth (PD), bleeding on probing (BOP), and plaque control record (PCR). Descriptive and nonparametric statistics were applied for all outcome measures.ResultsThe median profilometric contour between tooth preparation and 1 year after the insertion of the final FDP decreased by − 0.25 mm [Q1, Q3: − 0.36, 0.14] in the CONTROL group and increased by 0.61 mm [Q1, Q3: − 0.18, 1.06] in the SCTG group (intergroup p = 0.038). The alveolar ridge width between prior to tooth preparation and the one-year follow-up amounted to − 0.12 mm [Q1, Q3: − 0.74, 0.70] (= loss) in the CONTROL group and to 2.23 mm [Q1, Q3: 0.62, 3.86] (= gain) in the SCTG group (intergroup p = 0.032). At one year, the median crown height of the pontic tended to decrease by − 1.24 mm [Q1, Q3: − 2.05, − 1.05] in the SCTG group (intragroup p = 0.094) and by − 0.22 mm [Q1, Q3: − 0.58, 0.66] in the CONTROL group (intragroup p = 0.831), with significant differences between the groups (intergroup p = 0.022). The papilla index between prior to tooth preparation and one year of follow-up improved significantly in both groups (p < 0.05). Between FDP delivery and one year of follow-up, the PES values decreased significantly in the CONTROL group (intragroup p = 0.007), while in the SCTG group the change was not significant (intragroup p = 0.875). Clinical parameters (PD, BOP, and PCR) remained stable over time and did not differ between the groups at any time point (intergroup p > 0.05).ConclusionWithin the limitations of the present study, soft tissue grafting tends to limit contour changes at pontic sites, thus maintaining the esthetic outcomes over time. The lack of soft tissue grafting results in stable clinical outcomes; however, it may lead to a decrease in aesthetic outcomes over time.Clinical relevanceAutogenous soft tissue grafting seems to be a valid therapeutic option for the development of the pontic site to restore ridge defects prior to the delivery of fixed dental prostheses and to limit dimensional changes over time.

Contour Changes Following Implant Placement and Concomitant Soft Tissue Augmentation Applying a Volume-Stable Collagen Matrix.

The objective of this study was to assess volumetric and linear changes of buccal mucosal thickness at implant sites following soft tissue augmentation with a volume-stable collagen matrix (VCMX). Soft tissue augmentation using a VCMX was performed in 12 patients at the time of implant placement. Hydrocolloid impressions were taken prior to surgery and at 1 and 6 months postsurgery. Stone cast models were scanned, and stereolithography (STL) files from the three time points were uploaded to an image-analysis software. At all time points, linear and volumetric measurements of the contour changes up to 3 mm apical to the mucosal margin were performed and were analyzed statistically. At 1 mm apical to the mucosal margin, the change in soft tissue thickness between presurgery (T1) and 1 month (T2) amounted to 0.21 ± 1.22 mm, and the change between T1 and 6 months (T3) was 0.08 ± 1.47 mm. At 3 mm apical to the mucosal margin, the change in soft tissue thickness was 1.92 ± 1.70 mm between T1 and T2 and 0.31 ± 1.26 mm between T1 and T3. Contour (volumetric) changes revealed an increase of 0.58 ± 0.73 mm between T1 and T2 and an overall gain of 0.55 ± 0.73 mm between T1 and T3. Soft tissue augmentation with VCMX increased the ridge profile. The increase in ridge width was greater at 3 mm below the ridge crest than at 1 mm below the ridge crest. Remodeling processes during healing showed a decrease in the ridge contour between 1 and 6 months.

Predictability of overbite control with the Invisalign appliance comparing SmartTrack with precision bite ramps to EX30

Although the Invisalign appliance has reported difficulty in achieving the overbite outcomes predicted by ClinCheck software (Align Technology, Santa Clara, Calif), the effect of modifications to the material and components of the appliance are largely unquantified. This study aimed to investigate and determine the accuracy of Invisalign in correcting a deep overbite by comparing the predicted outcome from ClinCheck to the achieved posttreatment outcome for treatment groups that use different components of the appliance system. A retrospective study was conducted using pretreatment and posttreatment intraoral scans and predicted outcomes (ClinCheck) stereolithography files of 2 groups of consecutively treated adult patients from private specialist orthodontic practices, 1 group treated with EX30 material with no bite ramps (n= 29) and 1 treated with the newer SmartTrack material and precision bite ramps (n= 39). Inclusion criteria comprised nonextraction treatment, with a minimum of 14 dual arch Invisalign aligners using a 2-weekly aligner change protocol. Geomagic Control X software (3D Systems, Rock Hill, SC) was used to measure overbite in the pretreatment, posttreatment, and predicted outcome stereolithography files for each patient. Results were compared with a previously published treatment group that used SmartTrack material and no precision bite ramps. The regression coefficient analysis indicated that for both groups, the deeper the pretreatment overbite and the greater overbite reduction projected according to ClinCheck, there is a linear increase in the discrepancy of overbite expression posttreatment. ClinCheck overpredicted overbite reduction in 96.6% of patients with precision bite ramp in which, on average, 43.4% of the prescribed overbite reduction was expressed. For EX30 patients, ClinCheck overpredicted overbite reduction in 87.2% of patients in which, on average, 55.1% of the prescribed overbite reduction was expressed. The use of precision bite ramps does not appear to significantly improve the ability of SmartTrack material to predictably open the bite. SmartTrack material with or without bite ramps does not appear to produce better bite opening predictability than that seen with EX30 material.

Influence of printing procedure and printing axis of dental alloys on dimensional accuracy, surface roughness, and porosity

Objectives: This study aimed to evaluate the printing procedure and printing axis and its influence on the dimensional accuracy, surface roughness, porosity, and strength of 3D-printed dental alloys used in orthodontics prepared using binder jetting (BJ), electron beam melting (EBM), or selective laser melting (SLM). Material and Methods: Specimens with a dimension of 50 mm × 12 mm were produced using BJ, EBM, and SLM techniques of dental alloys and were printed either along the X-, Y-, or Z-axis (n = 8 per group). Specimen dimension was chosen according to the ISO standard 6892-1 for tensile strength test specimens. Surface roughness parameters Sa, Sz, Sq, and Ssk were obtained using a 3D laser microscope and porosities were visualized with scanning electron microscopy (SEM). The specimen surfaces were optically scanned and volumetric deviations from the original stereolithography files were calculated. Afterward, tensile strength was measured. Results: The printing method and printing axis significantly affected surface roughness parameters (P &lt; 0.05). Overall, the lowest surface roughness Sa values were found for BJ (9.1 ± 3.4 µm) followed by SLM (39.8 ± 24.2 µm) and EBM (50.4 ± 6.4 µm). BJ showed the smallest dimensional deviation followed by EBM and SLM. SEM analysis revealed a porous structure of BJ while fewer pores were observed on EBM and SLM samples. The ultimate tensile strength was only determined for BJ (495 ± 6 MPa) and EBM (726 ± 50 MPa) as the strength of SLM superseded the strength of the holder of the universal testing machine. Conclusion: BJ printing provides the highest dimensional accuracy with the smoothest surfaces irrespective of the printing axis. However, the remaining porosities owed to this printing procedure may have decreased the strength of the material.

Evaluation of radiodensity and dimensional stability of polymeric materials used for oral stents during external beam radiotherapy of head and neck carcinomas

PurposeIntraoral stents protect the healthy tissues from ionizing radiation during external beam radiotherapy reducing mucositis, hyposalivation and osteoradionecrosis.This study investigated the radiodensity and dimensional stability of polymeric materials for suitability in construction of intraoral stents and aimed to provide clinical guidelines. MethodsSpecimens were fabricated using 4 material types namely, resin composite (ProTemp-PRO), polymethylmethacrylate (PMMA) (Enamel Temp Plus-ETP, Palapress-PAL, TAB 2000-TAB), polycaprolactone (Orfit-ORF) and silicone (Adisil-ADI, Lab Putty-LAB, Memosil2-MEM, Optosil-OPT, President Plus-PRE, Siolaplast A-SIA).They were randomly assigned to measuretheir radiodensity inHounsfield Units(HU)(12x12x11mm3) (Nradiodensity = 66; n = 6)using a computer tomograph (CBCT,Toshiba Aquillon LB scanner)at baseline and after 6 weeks. The scanning protocol was applied with and without single energy metal artifact reduction (SEMAR) scans using a slice thickness of 1 and 5 mm.The same materials have been tested for their dimensional stability (µm3)at baseline, 1, 6, 12, 24 h, 3 and 6 weeks(14 × 4 × 2 mm3)(Ndimension = 55; n = 5 per material) using stereolithography (STL) files generated by a lab scanner (L2i, Imetric4D, Courgenay, Switzerland) and analyzed using a matchingsoftware(Geomagic ControlX 2020,3D Systems).Data were analyzed using a paired t-test (alpha = 0.05). ResultsRadiodensity values (HU) were significantly affected by the material classification (p < 0.05).Polycaprolactone(43.6) presented significantly lower HU valuesfollowed by PMMA (91.3–414.9) than those of silicone materials (292.8–874.5). In terms of dimensional stability (µm3), PMMA materials (Δ:1.53–2.68) andresin composite (Δ:2.89)were significantly more dimensionally stable compared to those of silicone materials(Δ:13.64–6.63)andpolycaprolactone (Δ:-0.76) and (p < 0.05). ConclusionFor fabricating intraoral stents, when reducedradiodensity valuesarerequiredpolycaprolactone could be recommended as it fulfils the requirements for reduced radiodensity and dimensional stability. Among all silicone materials,OPT and MEMcan be recommended based on the low HU and dimensional stability.

A framework of tolerance specification for freeform point clouds and capability analysis for reverse engineering processes

The combination of reverse engineering (RE) with additive manufacturing (AM) is widely used for solid freeform fabrication and overcomes limitations with the current capabilities of designers and CAD packages that are restricted to classical model shapes. The shape flexibility offered by RE typically leads to the generated CAD models being represented in point cloud formats or stereolithography files. One resulting challenge is the difficulty with tolerance specification for the RE-generated models, especially for freeform shapes. Geometric metrology for the AM-produced parts to determine their geometric conformation can also be involved. Furthermore, conventional process analyses cannot be performed directly after RE because of the complex geometric data structure. We propose to address all these issues with a new tolerance specification and process analysis framework based on volumetric data analysis. The tolerance zone constructed under our framework, and the corresponding geometric measurements, are consistent with the profile tolerance in geometric dimensioning and tolerancing standards. Reverse engineering's process capability is assessed under our methodology via a parametric bootstrap procedure in the size-and-shape space. The performance and utility of the proposed framework are validated via a process capability study on RE-generated CAD models of multiple, additively manufactured freeform objects.

Reliability and Time Efficiency of Digital vs. Analog Bite Registration Technique for the Manufacture of Full-Arch Fixed Implant Prostheses.

Objective: Information about full-digital protocols for bite registration with intraoral scanners on multiple implants in the edentulous jaw is scarce. The purpose of this comparative in vivo study was to investigate the reliability and time efficiency of a novel full-digital bite registration technique for the manufacture of full-arch maxillary fixed implant prostheses. Material and methods: In ten patients, a full-arch maxillary fixed implant prosthesis was manufactured on multi-unit abutment level through an analog prosthetic workflow. The bite registration was performed with use of a screw-retained polymethyl methacrylate (PMMA) verification jig with detachable wax rim. To articulate the definitive edentulous maxillary implant cast in centric relation at the appropriate occlusal vertical dimension (OVD) to the mandibular antagonist cast, a type II articulator (Artex, Amann Girrbach) was used. Three to six months later, a full-digital bite registration was performed with use of dual-function scan bodies and bilateral connected bite pillars. The bite pillars screwed into the scan bodies were used to adjust and articulate the edentulous maxillary implant arch to the mandibular antagonist arch at the defined OVD. Treatment time for analog and digital bite registration technique was measured in each patient. The reliability of the digital bite registration technique was evaluated by 3D comparison of two sets of stereo lithographic (STL) files obtained from each patient. The three-dimensional deviation was defined along the X-, Y- and Z-axes (Geomagic Control X, 3D Systems Inc., Rock Hill, SC, USA). Results: The treatment time for digital bite registration using dual-function scan bodies and bite pillars was significantly shorter than analog bite registration with verification jig and wax rim (60.30%, SD 5.72%). Minor differences between the two techniques were observed with a linear deviation range of 1115 µm (SD 668 µm) overall, 46.2 µm (SD 731.3 µm) along the X-axis, −200.3 µm (SD 744.3 µm) along the Y-axis and 67.1 µm (SD 752.2 µm) along the Z-axis. Bilateral balanced contacts were registered in all patients during full-digital bite registration. Conclusions: The novel digital bite registration technique with dual-function scan bodies and bite pillars allows for a full-digital workflow for full-arch implant supported restorations. The digital bite workflow was 60% faster, and the overall deviation was around 1 mm, which can be considered clinically acceptable.

Three-Dimensional Additive Manufacturing of Artificial Oil Reservoir Rock Core Plugs for Core Flooding Experimental Tests.

Laboratory tests in which a fluid or combination of fluids that are injected into a core rock are designed to determine oil reservoir rock petrophysical properties, understand the mobility of fluid flow in the porous samples, and calibrate porous media fluid flow models. The core material is extracted from the oil reservoir. However, the manufacture of core plugs is challenging because of the complexity of extracting natural rocks from the reservoir and their morphological and atypical heterogeneity. In addition, core flooding tests are essentially destructive, making it impossible to achieve experimental repeatability by using identical cores. The use of 3D printing in digital rock physics has permitted the production and replication of synthetic rock samples with the morphological characteristics of natural rocks for core analysis and core flooding tests. This study proposes the 3D manufacture of artificial core plugs from microcomputed tomography of Berea sandstone. The digital samples were constructed using a digital particle packing approach by systematically manipulating rock textural parameters, such as the grain size and shape, cementation pattern, and sorting grain, making it possible to obtain a core plug that fulfills experimental requirements. Before the 3D printing of the sample, the flow distribution through the porous media structure was numerically simulated using the Lattice Boltzmann method to obtain the core plug samples' permeability and porosity. The core plug was digitally embedded within a core holder to generate a stereolithography file for 3D printing of the core flooding setup, which can be used directly in conventional experiments. The permeabilities of the 3D printed plugs were experimentally determined to permit a direct comparison to the numerical results and evaluate the utility of printed plugs for displacement experiments.

Detailed Investigation of Three-Dimensional Modeling and Printing Technologies from Medical Images to Analyze Femoral Head Fractures Using Finite Element Analysis

Objectives: One of the fields, where additive manufacturing has numerous applications, is biomedical engineering. 3D printing is preferred over traditional manufacturing methodologies, mostly while developing subject-specific implants and medical devices. This study aims to provide a process flow detailing all the stages starting from the acquisition of radiological images from different imaging modalities; such as computed tomography (CT) and magnetic resonance imaging (MRI) to the printing of the bone morphology and finite element analysis; including the validation process.Materials & Methods: First, the CT scan of a lower abdomen area of a patient was converted into a 3D image using interactive medical imaging control system software. The segmentation process was applied to isolate the femoral head from the soft tissue and the pelvic bone. After the roughness errors and the gaps in the segments were removed using the 3Matic software, the file was converted to stereolithography (STL) file format to transfer to the 3D printer. The printing process was carried out via commercial powder-based Selective Laser Sintering (SLS) printer. The subject-specific femoral head model was formed in 3D. The Finite Element Analysis (FEA) of the femoral head was performed using a commercial FE software package.Results: The results show that experimental analysis and the CT scan-based FEA were compatible both for the stress distributions and the strain values as predicted by the models (R2=0.99). The deviation was calculated as approximately 12% between the experimental results and the Finite Element (FE) results. In addition, it was observed that the SLS technique produced useful results for modeling biomedical tissues with about 24x faster prototyping time.Conclusion: The prescribed process flow could be utilized in clinical settings for the pre-planning of the surgeries (≈428 minutes for femoral head) and also as an educational tool in the biomedical engineering field.

Effect of the implant-supported provisional restoration on the accuracy of digital peri-implant mucosa replication-A clinical study.

This study aimed to quantitatively evaluate the effect of implant-supported provisional restorations (ISPRs) on the accuracy of the intraoral scanned peri-implant soft-tissue profile in the esthetic area. Sixteen patients with a single ISPR in the maxillary central incisor's region were recruited for this study. Three impression methods were sequentially used in each patient: (1) an intraoral scanning (IOS) with the ISPR, (2) a conventional impression using the ISPR as impression coping, and (3) a routine IOS without the ISPR. The stereolithography files of the three impression methods obtained from the same patient were superimposed, and the conventional impression method was used as the reference model. Two-dimensional (2D) and three-dimensional (3D) analyses were performed to measure the peri-implant soft-tissue deviation between the reference models and IOS from the groups with or without the ISPR, respectively. Data were presented as the means±standard deviations. Two-way analyses of variance with post hoc Sidak's multiple comparisons and paired t-tests were performed for 2D and 3D analyses, respectively. The significance level was set at p<.05. The peri-implant mucosa without the ISPR immediately collapsed (<20s), particularly on the palatine side of the labial mucosa and labial side of the palatine mucosa. Consequently, the IOS without the ISPR led to 414.7±116.0μm of overall dimensional deformation in the cuff-like submucosal region, which was significantly larger (p<.0001) than that in the IOS with the ISPR (230.6±85.5μm). Implant-supported provisional restorations are important for accurate replication of the intraorally scanned peri-implant soft-tissue profile.

319 G-Master: A Novel 3D Printed ACL Graft Preparation System That Improves Speed and Autonomy

Abstract Aim One of the most commonly performed procedures in orthopaedics is anterior cruciate ligament reconstruction. Autograft hamstring tendons are mostly used. The preparation of a hamstring autograft varies on patient factors and clinician choices. The use of a bulky, and expensive metal platform is usually involved, or an assistant is tasked to hold the other end of the graft. We aim to produce a 3D-printed sterilisable preparation system (G-Master) that improves autonomy and speed of the surgeon preparing the ACL graft. Method A stereolithography file (.stl) of the device was designed on Blender program and then manufactured on a commercial Fusion Deposition Modelling Ender 5 3-dimensional (3D) printer using a polylactic acid variant. The 3D printed parts include an attachable platform, two pillars whereby the attached pillar is where the endobutton (SN) holding the autograft sits in tension. These were autoclaved at 121°C under 15 psi of steam pressure for 30 minutes before the operation. Approval for device use was subjected to a rigorous process as class I devices as per the UK government Medicines and Healthcare Products Regulatory Agency guidelines and was then successfully used in vivo. Results We found the bespoke device to be beneficial in reducing graft preparation time and overall cost while increasing the autonomy of the surgeon and efficiency of the knee operating theatre list. Conclusions This is, to our knowledge, the first ACL graft preparation system that was produced using rapid prototyping and 3D printing. Other applications of 3D printing in manufacturing orthopaedic surgical instruments should be explored.

Mitral paravalvular leak 3D printing from 3D-transesophageal echocardiography - proof of concept

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Ministry of Science and Higher Education Background Paravalvular leak (PVL) may occur in almost 15% of patients undergoing surgical mitral valve replacement. This complication can cause congestive heart failure and hemolysis. Multimodal imaging including computed tomography (MSCT) and 3D-transesophageal echocardiography (3D-TEE) is essential for assessment of PVLs. 3D-TEE-based 3D-printing might be useful in preprocedural planning of PVL closure for the optimization of transcatether procedures. In contrast to 3D-printing based on MSCT, use of 3D-TEE for segmentation and printing is not standardized. Purpose A proof of concept study to evaluate 3D printing of mitral PVLs using 3D-TEE. Methods A case of a 64-year-old woman with 2 clinically significant PVLs around a mitral prosthetic valve is presented. In 3D-TEE (Philips Epiq) anteromedial defects were visualized (surgical view). Qlab Station was used to export the 3D recording of PVLs with surrounding tissue in cartesian DICOM format. Next Slicer, a free open-source software, was used for segmentation and preparation of a STL (stereolithography) file. The PVL model was printed with Starsys Objet 30 printer using Med620 material. Diameters PVLs were the same in 3D Echocardiography and 3D printed model (12mm and 9mm). Results Printed PVL model and corresponding 3D-TEE image are shown in Figure 1 and Figure 2, respectively. Conclusion(s) Proof of concept study confirms feasibility of using standard 3D-TEE and open source software for preparation of 3D models of anatomically complex mitral PVLs. Further studies to assess cost-effectiveness and clinical applicability of the presented methodology are ongoing. Abstract Figure 1. Abstract Figure 2.

Development and implementation of a software for wire arc additive manufacturing preprocessing planning: trajectory planning and machine code generation

To overcome a shortage of flexible and low-cost solutions for wire arc additive manufacturing (WAAM) preprocessing, this work’s objective was to develop and validate an in-house computational programme in an open-source environment for WAAM preprocessing planning. Algorithms for reading STL (stereolithography) files and implementing rotation, slicing, trajectory planning, and machine code generation were elaborated and implemented in the Scilab environment (free and open-source). A graphical interface was developed to facilitate user interaction, with 5 options for path planning. The functionality of each work step is detailed. For validation of the software, single and multiple-layer prints, with different geometrical complexity and printing challenges, were built in a CNC table geared by the generated machine code. The validation criteria were deposition imperfection, morphological, and dimensional tolerances. The outputs showed that the parts were successfully printed. Therefore, this work demonstrates that Scilab provides the necessary resources for companies and universities to implement and/or develop algorithms for planning and generating trajectories for WAAM. Moreover, emerging ideas can be reasonably easily implemented in such software, not always possible in commercial packages.

All-in-one encoder/decoder approach for non-destructive identification of 3D-printed objects.

This paper presents an all-in-one encoder/decoder approach for the nondestructive identification of three-dimensional (3D)-printed objects. The proposed method consists of three parts: 3D code insertion, terahertz (THz)-based detection, and code extraction. During code insertion, a relevant one-dimensional (1D) identification code is generated to identify the 3D-printed object. A 3D barcode corresponding to the identification barcode is then generated and inserted into a blank bottom area inside the object's stereolithography (STL) file. For this objective, it is necessary to find an appropriate area of the STL file and to merge the 3D barcode and the model within the STL file. Next the information generated inside the object is extracted by using THz waves that are transmitted and reflected by the output 3D object. Finally, the resulting THz signal from the target object is detected and analyzed to extract the identification information. We implemented and tested the proposed method using a 3D graphic environment and a THz time-domain spectroscopy system. The experimental results indicate that one-dimensional barcodes are useful for identifying 3D-printed objects because they are simple and practical to process. Furthermore, information efficiency can be increased by using an integral fast Fourier transform to identify any code located in areas deeper within the object. As 3D printing is used in various fields, the proposed method is expected to contribute to the acceleration of the distribution of 3D printing empowered by the integration of the internal code insertion and recognition process.

The effect of the digital manufacturing technique of cantilevered implant-supported frameworks on abutment screw preload.

PURPOSEThe purpose of this study was to investigate the misfit and screw preload at the implant abutment connection of implant supported fixed dental prosthesis with cantilever (ICFDP) manufactured using different digital manufacturing techniques and to compare the screw preload before and after cyclic loading.MATERIALS AND METHODSMandibular jaw model with four intra-foraminal implants was scanned using digital scanner. Stereolithography file was used to design a framework with nonengaging (NE) abutments and 10 mm cantilever distal to one terminal implant. Five frameworks were constructed using combined digital-conventional techniques (CAD-cast), and five frameworks were constructed using three-dimensional printing (3DP). Additional CAD-cast framework was constructed in a way that ensures passive fit (PF) to use as control. Scanning electron microscope (SEM) measured the implant abutment connection misfit. Sixty screws were used on the corresponding frameworks. Screws were torqued and pre-cyclic loading reverse torque value (RTV) was recorded. Frameworks were subjected to 200,000 loading cycles with a loading point 9 mm from the center of terminal implants adjacent to the cantilever and post-cyclic loading RTVs were recorded.RESULTSMicroscopic readings showed significant differences between frameworks. PF demonstrated the lowest measurements of 16.04 (2.6) µm while CAD-cast demonstrated the highest measurements of 29.2 (3.1) µm. In all groups, RTVs were significantly lower than the applied torque. Post-cyclic loading RTV was significantly lower than pre-cyclic loading RTV in PF and 3DP frameworks. Differences in RTVs between the three manufacturing techniques were insignificant.CONCLUSIONAlthough CAD-cast and three-dimensionally printed (3DP) both produce frameworks with clinically acceptable misfit, 3DP might not be the technique of choice for maintaining screw’s preload stability under an aggressive loading situation.