Comparison of additive manufactured models of the mandible in accuracy and quality using six different 3D printing systems

Multi-Site evaluation of a novel point-of-care 3D printing quality assurance protocol for a material jetting 3D printer

BACKGROUND

The maturation of 3D printing technologies has opened up a new space for patient advancements in healthcare from trainee education to patient specific medical devices. Point-of-care (POC) manufacturing, where model production is done on-site, includes multiple benefits such as enhanced communication, reduced lead time, and lower costs. However, the small scale of many POC manufacturing operations complicates their ability to establish quality assurance practices. This study presents a novel low-cost quality assurance protocol for POC 3D printing.

METHODS

Four hundred specially designed quality assurance cubes were printed across four material jetting printers (J5 Medijet, Stratasys, Eden Prairie, Minnesota, USA) at two large medical centers. Three inner dimension and three outer dimension measurements as well as edge angles were measured for every cube by trained research personnel. The delta and absolute error was calculated for each cube and then compared across variables (axis, material, inner vs. outer dimension, swath and machine/site/personnel) using ANOVA analysis.

RESULTS

Print axis and inner vs. outer dimension of the model produced statistically significant differences in error while there was no statistically significant difference in the error for material, print swath, or machine/site/personnel. For the print axes, the printers produced an average error of 26, 53, and 57 μm and the error at three sigma was found to be 100, 158, and 198 μm for the Z, R, and Theta axes, respectively.

CONCLUSION

This study demonstrates that this novel protocol is both feasible and reliable for quality assurance in POC 3D printing across multiple sites. This protocol offers an adaptable framework that allows users to tailor the QA process to their specific needs. Through the comprehensive method, users can measure and identify all relevant factors that might introduce error into their printed product and then follow the most critical aspects for their situation across every print. The QA cubes produced via this protocol can provide guidance on print quality and alert users to unsatisfactory machine operation which could cause prints to fall outside of engineering and clinical tolerances.

Quality assurance of 3D-printed patient specific anatomical models: a systematic review

BACKGROUND

The responsible use of 3D-printing in medicine includes a context-based quality assurance. Considerable literature has been published in this field, yet the quality of assessment varies widely. The limited discriminatory power of some assessment methods challenges the comparison of results. The total error for patient specific anatomical models comprises relevant partial errors of the production process: segmentation error (SegE), digital editing error (DEE), printing error (PrE). The present review provides an overview to improve the general understanding of the process specific errors, quantitative analysis, and standardized terminology.

METHODS

This review focuses on literature on quality assurance of patient-specific anatomical models in terms of geometric accuracy published before December 4th, 2022 (n = 139). In an attempt to organize the literature, the publications are assigned to comparable categories and the absolute values of the maximum mean deviation (AMMD) per publication are determined therein.

RESULTS

The three major examined types of original structures are teeth or jaw (n = 52), skull bones without jaw (n = 17) and heart with coronary arteries (n = 16). VPP (vat photopolymerization) is the most frequently employed basic 3D-printing technology (n = 112 experiments). The median values of AMMD (AMMD: The metric AMMD is defined as the largest linear deviation, based on an average value from at least two individual measurements.) are 0.8 mm for the SegE, 0.26 mm for the PrE and 0.825 mm for the total error. No average values are found for the DEE.

CONCLUSION

The total error is not significantly higher than the partial errors which may compensate each other. Consequently SegE, DEE and PrE should be analyzed individually to describe the result quality as their sum according to rules of error propagation. Current methods for quality assurance of the segmentation are often either realistic and accurate or resource efficient. Future research should focus on implementing models for cost effective evaluations with high accuracy and realism. Our system of categorization may be enhancing the understanding of the overall process and a valuable contribution to the structural design and reporting of future experiments. It can be used to educate specialists for risk assessment and process validation within the additive manufacturing industry.

Geometric Cuts by an Autonomous Laser Osteotome Increase Stability in Mandibular Reconstruction With Free Fibula Grafts: A Cadaver Study

BACKGROUND

Nonunion and plate exposure represent a major complication after mandibular reconstruction with free fibula flaps. These drawbacks may be resolved by geometric osteotomies increasing intersegmental bone contact area and stability.

PURPOSE

The aim of this study was to compare intersegmental bone contact and stability of geometric osteotomies to straight osteotomies in mandibular reconstructions with free fibula grafts performed by robot-guided erbium-doped yttrium aluminum garnet laser osteotomy.

STUDY DESIGN, SETTING, SAMPLE

This cadaveric in-vitro study was performed on fresh frozen human skull and fibula specimens. Computed tomography (CT) scans of all specimens were performed for virtual planning of mandibular resections and three-segment fibula reconstructions. The virtual planning was implemented in a Cold Ablation Robot-guided Laser Osteotome.

PREDICTOR/EXPOSURE/INDEPENDENT VARIABLE

For predictor variables, straight and geometric puzzle-shaped osteotomies were designed at resection of the mandible and corresponding fibula reconstruction.

MAIN OUTCOME VARIABLES

The primary outcome variable was the stability of the reconstructed mandible investigated by shearing tests. Moreover, secondary outcome variables were the duration of the laser osteotomies, the contact surface area, and the accuracy of the reconstruction, both evaluated on postsurgical CT scans.

COVARIATES

Covariables were not applicable.

ANALYSES

Data were reported as mean values (± standard deviation) and were statistically analyzed using an independent-sample t-test at a significance level of α = 0.05. Root mean square deviation was tested for accuracy.

RESULTS

Eight skulls and 16 fibula specimens were used for the study. One hundred twelve successful laser osteotomies (96 straight and 16 geometrical) could be performed. Geometric osteotomies increased stability (110.2 ± 36.2 N vs 37.9 ± 20.1 N, P < .001) compared to straight osteotomies. Geometric osteotomy of the fibula took longer than straight osteotomies (10.9 ± 5.1 min vs 5.9 ± 2.2 min, P = .028) but could provide larger contact surface (431.2 ± 148.5 mm2 vs 226.1 ± 50.8 mm2, P = .04). Heat map analysis revealed a mean deviation between preoperational planning and postreconstructive CT scan of -0.8 ± 2.4 mm and a root mean square deviation of 2.51 mm.

CONCLUSION AND RELEVANCE

Mandibular resection and reconstruction by fibula grafts can be accurately performed by a Cold Ablation Robot-guided Laser Osteotome without need for cutting guides. Osteotomy planning with geometric cuts offers higher stability and an increased bone contact area, which may enhance healing of the reconstructed mandible.

Comparison of different 3D printers in terms of dimensional stability by image data of a dry human mandible obtained from CBCT and CT

OBJECTIVES

To manage the mandibular traumas, for the expression of the complex anatomy or pathology in education of health sciences related branches, a model of the traumatized mandible is indispensable. For these, different 3D-print-technologies can be used. The aim of this study is, to measure how close these 3D-printed-models are to human-mandible (trueness) and the effectiveness of CT and CBCT at this point.

STUDY DESIGN

One-dry-human-mandible and 10-models manufactured by five different 3D-printers in four different-kinds of additive-manufacturing technology (Fused-Deposition-Modeling (FDM), Stereolithography (SLA), Binder-jetting (BJ), Polyjet (PJ)) were used, five-anatomic-landmarks and eight-distances were measured and evaluated. Mandible's data were constructed based on DICOM-3.0 data from CBCT and CT scans. Images were opened in MIMICS (software-program).

RESULTS

Study compared the devices that produced models with the same dry human-mandible. It was seen that the model with the highest margin of error (132.5 mm) was manufactured by Fused-deposition-modeling device using CT-data. In terms of distance to real-data, the model with the lowest error was generated by Binder-Jetting (ZCorp) with CBCT-data. Models produced with CBCT-data are closer to dry-human-mandible than models with CT-data.

CONCLUSION

The current study shows that CBCT generates significantly better data than CT in producing mandibular models. The first choice for manufacturing of human mandible is BJ and the second choice is the technology of SLA.

Accuracy of additive manufacturing in stomatology

With the rapid development of the three-dimensional (3D) printing technology in recent decades, precise and personalized manufacturing has been achieved gradually, bringing benefit to biomedical application, especially stomatology clinical practice. So far, 3D printing has been widely applied to prosthodontics, orthodontics, and maxillofacial surgery procedures, realizing accurate, efficient operation processes and promising treatment outcomes. Although the printing accuracy has improved, further exploration is still needed. Herein, we summarized the various additive manufacturing techniques and their applications in dentistry while highlighting the importance of accuracy (precision and trueness).

Analyzing the Fitting of Novel Preformed Osteosynthesis Plates for the Reduction and Fixation of Mandibular Fractures

Purpose: The known preformed osteosynthesis plates for the midface are helpful tools for a precise and fast fixation of repositioned fractures. The purpose of the current study is to analyze the precision of newly developed prototypes of preformed osteosynthesis plates for the mandible. Methods: Four newly designed preformed osteosynthesis plates, generated by a statistical shape model based on 115 CT scans, were virtually analyzed. The used plates were designed for symphyseal, parasymphyseal, angle, and condyle fractures. Each type of plate has three different sizes. For analysis, the shortest distance between the plate and the bone surface was measured, and the sum of the plate-to-bone distances over the whole surface was calculated. Results: A distance between plate and bone of less than 1.5 mm was defined as sufficient fitting. The plate for symphyseal fractures showed good fitting in 90% of the cases for size M, and in 84% for size L. For parasymphyseal fractures, size S fits in 80%, size M in 68%, and size L in 65% of the cases. Angle fractures with their specific plate show good fitting for size S in 53%, size M in 60%, and size L in 47%. The preformed plate for the condyle part fits for size S in 75%, for size M in 85%, and for size L in 74% of the cases. Conclusion: The newly developed mandible plates show sufficient clinical fitting to ensure adequate fracture reduction and fixation.

Mandible reconstruction with free fibula flaps: Accuracy of a cost-effective modified semicomputer-assisted surgery compared with computer-assisted surgery - A retrospective study

A new individualized, cost-effective, modified semi-computer-assisted surgery (MSCAS) concept for free fibular flap mandibular reconstruction is reported and compared with the computer-assisted surgery (CAS) concept. Patients were divided into two groups and retrospectively reviewed. In the MSCAS and CAS groups, intraoperative guides were created using computer-aided design with manual fabrication and computer-aided design and manufacturing, respectively. Differences in specific linear and angular parameters on pre- and postoperative computed tomography scans were calculated for morphometric comparison, and clinical parameters and efficiency were analysed. RESULTS: Eighteen patients (CAS, 7; MSCAS, 11), were included. The morphometric comparison showed no significant differences between the groups. The mean deviation of the mandibular ramus length, body length, width 1 and width 2 was 0.82 ± 0.29 mm, 1.84 ± 0.43 mm, 1.89 ± 0.61 mm and 1.45 ± 0.61 mm in the CAS group versus 1.56 ± 0.54 mm, 1.72 ± 0.33 mm, 2.24 ± 0.55 mm and 2.36 ± 0.50 mm in the MSCAS group (p = 0.7804, p = 0.9997, p = 0.9814 and p = 0.6334). The mean deviation of the sagittal, axial and coronal mandibular angles was 1.56 ± 0.48°, 1.93 ± 0.50° and 2.15 ± 0.72° in the CAS group versus 2.19 ± 0.35°, 1.86 ± 0.35° and 1.94 ± 0.55° in the MSCAS group (p = 0.7594, p = 0.9996 and p = 0.9871). There were no significant differences in clinical parameters, efficiency or postoperative complications between the groups. CONCLUSION: The accuracy and operative efficiency of the MSCAS concept are comparable to those of the more expensive CAS concept. Therefore, in times of increasing clinical costs, this concept might be an adequate and inexpensive alternative to preoperative CAS.

Estimating the Accuracy of Mandible Anatomical Models Manufactured Using Material Extrusion Methods

The development of new solutions in craniofacial surgery brings the need to increase the accuracy of 3D printing models. The accuracy of the manufactured models is most often verified using optical coordinate measuring systems. However, so far, no decision has been taken regarding which type of system would allow for a reliable estimation of the geometrical accuracy of the anatomical models. Three types of optical measurement systems (Atos III Triple Scan, articulated arm (MCA-II) with a laser head (MMD × 100), and Benchtop CT160Xi) were used to verify the accuracy of 12 polymer anatomical models of the left side of the mandible. The models were manufactured using fused deposition modeling (FDM), melted and extruded modeling (MEM), and fused filament fabrication (FFF) techniques. The obtained results indicate that the Atos III Triple Scan allows for the most accurate estimation of errors in model manufacturing. Using the FDM technique obtained the best accuracy in models manufactured (0.008 ± 0.118 mm for ABS0-M30 and 0.016 ± 0.178 mm for PC-10 material). A very similar value of the standard deviation of PLA and PET material was observed (about 0.180 mm). The worst results were observed in the MEM technique (0.012 mm ± 0.308 mm). The knowledge regarding the precisely evaluated errors in manufactured models within the mandibular area will help in the controlled preparation of templates regarding the expected accuracy of surgical operations.