From Academia: 3D-Printed Aligner, Bioprinting for Mouth Ulcer, Vertebroplasty Guides

Nov 08, 2019

This is our weekly selection of recently published academic abstracts focusing on topics 3DHEALS audience would be interested in. Submit your favorite publication to ([email protected])

This week’s collection comes from many different fields, including digital dentistry, spinal surgery, orthopedics, pharmacology, and more. The conclusion drawn from comparing the geometric and mechanical properties of the conventional thermoformed versus 3D-printed aligner showed a clear advantage of the 3d-printed version. However, scalability will remain a question. That said, this makes it easier to deliver dental aligners to patients who have little access to large scale commercial dental aligner products, removing third party involvement from the dentist and the patient, and possibly delivering higher quality and quick service.

In the medical 3D printing section, one group provided a thorough review of how they use a 3D-printed guide to help with vertebroplasty procedures in osteoporotic patients who experienced vertebral body compression fractures. Having participated in several such procedures myself, it is definitely a relief that surgeons/interventionist is looking into ways to remove the “art” part of practicing medicine and aim for more precision.

In pharmacology, more studies are showing up focusing on the on-demand formulation of medications for a variety of needs using 3D printing.

In the world of design, researchers are trying to design the best device to reduce the impact of falls, using 3D printing. This is especially important in elderlies, who often experience life-threatening injuries. This brings back the subject of generative design, where computers inspire the designers and equip them with performance data.

Dental 3D Printing

Mechanical and geometric properties of thermoformed and 3D printed clear dental aligners. (Jindal P, et al) Am J Orthod Dentofacial Orthop. 2019 Nov;156(5):694-701. doi: 10.1016/j.ajodo.2019.05.012.

INTRODUCTION:

The aim of this research was to compare compressive mechanical properties and geometric inaccuracies between conventionally manufactured thermoformed Duran clear dental aligners and 3D printed Dental Long Term (LT) resin-based clear aligners using 3D modeling and printing techniques.

METHODS:

Impressions of the patient’s dentition were scanned and using 3D modeling software, dental models were designed, and 3D printed. These printed models then underwent vacuum thermoforming to thermoform a clear Duran thermoplastic sheet of 0.75-mm thickness into clear dental aligners of the same thickness of 0.75 mm. For the same dental model, aligners were also designed, and 3D printed to 0.75-mm thickness creating biocompatible clear dental aligners using Dental LT resin utilizing a Formlabs 3D printing machine for direct usage by the patients. Five observers calculated teeth height for both types of aligners for the evaluation of geometric deviations. Both types of aligners were subjected to compression loading of 1000 N to evaluate their load vs displacement behavior.

RESULTS:

3D printed cured clear dental aligners were found to be geometrically more accurate with an average relative difference in tooth height of 2.55% in comparison with thermoformed aligners (4.41%). Low standard deviations (0.03-0.09 mm) were observed for tooth height measurements taken by all the observers for both types of aligners. 3D printed aligners could resist a maximum load of nearly 662 N for a low displacement of 2.93 mm; whereas, thermoformed aligners could resist a load on only 105 N for 2.93-mm displacement. Thermoformed aligners deformed plastically and irreversibly for large displacements; whereas, 3D printed aligners deformed elastically with reversibility for lower displacements.

CONCLUSIONS:

3D printed and suitably cured Dental LT resin-based clear dental aligners are suggested to be more suitable for patient use as they are geometrically more accurate; this presents an opportunity to make processing time savings while ensuring an aligner is mechanically stronger and elastic in comparison with the conventionally produced thermoplastic-based thermoformed clear dental aligners.

Copyright © 2019 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.

Medical 3D Printing

Usefulness of a 3D-Printed Thyroid Cancer Phantom for Clinician to Patient Communication.

(Hong D, et al) World J Surg. 2019 Nov 4. doi: 10.1007/s00268-019-05260-z.

BACKGROUND:

Thyroid glands and surrounding structures are very complex, and this complexity can pose a challenge for clinicians when explaining and communicating to the patient the details of a proposed surgery for thyroid cancer. A three-dimensional (3D) thyroid cancer model could help and improve this communication.

METHODS:

A 3D-printed phantom of a thyroid gland and its presenting cancer was produced from segmented head and neck contrast-enhanced computed tomography (CT) data from a patient with thyroid cancer. The phantom reflects the complex anatomy of the arteries, veins, nerves, and other surrounding organs, and the printing materials and techniques were adjusted to represent the texture and color of the actual structures. Using this phantom, patients and clinicians completed surveys on the usefulness of this 3D-printed thyroid cancer phantom.

PARTICIPANTS:

patients (n = 33) and clinicians (n = 10).

RESULTS:

In the patient survey, the patients communicated that the quality of understanding of their thyroid disease status was enhanced when clinicians explained using the phantom. The clinicians communicated that the 3D phantom was advantageous for explaining complex thyroid surgery procedures to patients, and that the 3D phantom was helpful in educating patients with relatively poor anatomical knowledge.

CONCLUSIONS:

Using 3D printing technology, we produced a CT-based 3D thyroid cancer phantom, and patient and clinician surveys on its utility indicated that it successfully helped educate patients, providing them with an improved understanding of the disease.

Three-Dimensional Printing Guide Template Assisted Percutaneous Vertebroplasty (PVP). (Hu P, et al) J Vis Exp. 2019 Oct 17;(152). doi: 10.3791/60010.

Percutaneous vertebroplasty (PVP) is considered an effective treatment for the back pain caused by osteoporotic vertebral compression fracture. The accuracy of PVP mainly depends on the surgeons’ experience and multiple fluoroscopes during a traditional procedure. Puncture related complications were reported all over the world. To make the surgical procedure more precise and decrease the rate of puncture-related complications, our team applied a three-dimensional printing guide template to PVP to modify the traditional procedure. This protocol introduces how to model target vertebrae DICOM imaging data into three-dimensions in the software, how to simulate operation in this 3-D model, and how to use all of the surgical data to reconstruct a patient-specific template for an application. Using this template, surgeons can identify suitable puncture points accurately to improve the accuracy of the operation. The whole protocol includes 1) diagnosis of the osteoporotic vertebral compression fracture; 2) acquisition of CT imaging of the target vertebra; 3) simulation of the operation in the software; 4) design and fabrication of the 3-D printing guide template; and 5) application of the template into an operation procedure.

Check out a video associated with this article.

The figure above: Typical operation steps. (A) Use the gradient to ensure that the patient is in the same position when the CT was performed; (B) Match one template with skin to determine the puncture points; (C) Final puncture points; (D) Use the puncture needles to double-check the puncture points; (E) Fix the other sterilized template and insert the needles; (F) Tap the needles to the end of the trajectories; (G) Inject bone cement bilaterally via the needles; (H) Final fluoroscope of the distribution of bone cement within the vertebral body.

Sterility of 3D-Printed Orthopedic Implants Using Fused Deposition Modeling. (Skelley NW, et al)

Orthopedics. 2019 Nov 6:1-6. doi: 10.3928/01477447-20191031-07.

The use of 3-dimensional (3D) printing in orthopedics is developing rapidly and impacting the areas of preoperative planning, surgical guides, and simulation. As this technology continues to improve, the greatest impact of 3D printing may be in low- and middle-income countries where surgical items are in short supply. This study investigated the sterility of 3D-printed ankle fracture fixation plates and cortical screws. The hypothesis was that the process of heated extrusion in fused deposition modeling printing would create sterile prints in a timely fashion that would not require postproduction sterilization. A free computer-assisted design program was used to design the implant models. One control group and 8 study groups were printed. Print construct, orientation, size, and postproduction sterilization differed among the groups. Sterility was assessed using thioglycollate broth cultures at 24 hours, 48 hours, and 7 days. Positive growth was speciated for aerobic and anaerobic bacteria. Print time and failed prints were recorded. Control samples were 100% positive for bacterial growth. All test samples remained sterile at all time points (100%). Speciation of control samples was obtained, and Staphylococcus was the most common species. Print times varied; however, no print time exceeded 6.75 minutes. Eighteen prints (17%) failed in the printing process. These findings demonstrate an intrinsic sterilization process associated with fused deposition modeling 3D printing and indicate the feasibility of 3D-printed surgical implants and equipment for orthopedic applications. With future research, 3D-printed implants may be a treatment modality to assist orthopedic surgeons in low- and middle-income countries.

Design

Developing Fall-impact Protection Pad with 3D Mesh Curved Surface Structure using 3D Printing Technology.

(Park JHLee JR.) Polymers (Basel). 2019 Nov 1;11(11). pii: E1800. doi: 10.3390/polym11111800.

In this study, we present the development of fall-impact protection pads for elderly people using three-dimensional (3D) printing technology. To develop fall-impact protection clothing, it is important to maintain the functionality of the protection pad while ensuring that its effectiveness and appearance remain optimal in the process of inserting it. Therefore, this study explores the benefit of exploiting 3D scan data of the human body using 3D printing technology to develop a fall-impact protection pad that is highly suited to the human body shape. The purpose of this study was to present a 3D modeling process for creating curved protective pads comprising a hexagonal mesh with a spacer fabric structure and to verify the impact protection performance by printing curved pads. To this end, we set up a section that includes pads in the 3D human body scan data and extracted body surface information to be applied in the generation of the pad surface. The sheet-shaped hexagonal mesh structure was cut and separated according to the pad outline, and then deformed according to the curved surface of the human body. The pads were printed, and their protection performance was evaluated; a 79.2-81.8% reduction in impact force was observed compared to similar cases in which the pads were not used.

Pharmacology

Fabrication of Muco-Adhesive Oral Films by the 3D Printing of Hydroxypropyl Methylcellulose-Based Catechin-Loaded Formulations.

(Tagami T, et al) Biol Pharm Bull. 2019;42(11):1898-1905. doi: 10.1248/bpb.b19-00481.

Pharmaceutical applications of three dimensional (3D) printing technology are increasing following the approval of 3D-printed tablets by the U.S. Food and Drug Administration. Semi-solid extrusion-type 3D printers are used to 3D print hydrogel- and paste-based materials. We previously developed tablet formulations for semi-solid extrusion-type 3D bioprinters. In the present study, we extended our study to the preparation of mucoadhesive oral film formulations to 3D bioprint mouth ulcer pharmaceuticals. We focused on hydroxypropyl methylcellulose (HPMC)-based catechin (model drug)-loaded hydrogel formulations and found that the viscosity of a hydrogel formulation is dependent on the HPMC concentration and that viscosity is important for facile 3D printing. HPMC-based films were prepared using two different drying methods (air drying and freeze-drying). The films exhibited different drug dissolution profiles and increasing the amount of HPMC in the film delayed drug dissolution. The fabrication of HPMC-based catechin-loaded films with different shapes provides a model of individualized, on-demand pharmaceuticals. Our results support the flexible application of 3D bioprinters (semi-solid extrusion-type 3D printers) for preparing film formulations.

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