Rapid prototyping modelling in oral and maxillofacial surgery: A two year retrospective study

Tracheal intubation in patients with Pierre Robin sequence: development, application, and clinical value based on a 3-dimensional printed simulator

Background: The main clinical manifestations of patients with Pierre Robin sequence (PRS) include micrognathia, the glossoptosis and dyspnoea. The difficulty of tracheal intubation (TI) in such patients is increased. Objective: The purpose of the study was to evaluate the reliability and efficacy of the PRS simulator. Methods: A PRS simulator was developed by using 3-dimensional (3D) printing technology under computer-aided design. A total of 12 anaesthesiologists each trained 5 times for TI on the PRS Training Simulator-1 and recorded the simulation time. After the training, they were randomly divided into three groups with a total of 12 nontrained anaesthesiologists, and the simulation was completed on PRS Simulator-2, 3 and 4. The simulation time was recorded, and the performance was evaluated by three chief anaesthesiologists. Then, all 24 anaesthesiologists completed the questionnaire. Results: A PRS simulator developed by 3D printing was used to simulate the important aspects of TI. The average number of years worked was 6.3 ± 3.1 years, and 66.7% were female. The time for the 12 anaesthesiologists to complete the training gradually decreased (p < 0.01). Compared with the trained anaesthesiologists, the simulation time of TI in the nontrained anaesthesiologists was much longer (all p < 0.01). In addition, the simulation performance of the trained anaesthesiologists was relatively better (all p < 0.01). Conclusion: The reliability and efficacy of the PRS simulator is herein preliminarily validated, and it has potential to become a teaching and training tool for anaesthesiologists.

Three-dimensional printing in the field of oral and maxillofacial surgery

Advanced imaging techniques and modalities coupled with computer-assisted surgical planning and simulation has been in use in the field of medicine. However, it is worth noting that it is now being frequently used for the evaluation and exploration of the craniofacial structures. It had gained ingress in the planning as well as forecasting of the surgical outcomes of oral and maxillofacial surgical interventions. Numerous surgical guides and devices which are tailor-made can be fabricated using three-dimensional (3D) printing technology. The article is intended to put forth an overview of 3D printing technology and its applications in the field of oral and maxillofacial surgery.

Investigation of Patient-Specific Maxillofacial Implant Prototype Development by Metal Fused Filament Fabrication (MF3) of Ti-6Al-4V

Additive manufacturing (AM) and related digital technologies have enabled several advanced solutions in medicine and dentistry, in particular, the design and fabrication of patient-specific implants. In this study, the feasibility of metal fused filament fabrication (MF³) to manufacture patient-specific maxillofacial implants is investigated. Here, the design and fabrication of a maxillofacial implant prototype in Ti-6Al-4V using MF³ is reported for the first time. The cone-beam computed tomography (CBCT) image data of the patient’s oral anatomy was digitally processed to design a 3D CAD model of the hard tissue and fabricate a physical model by stereolithography (SLA). Using the digital and physical models, bone loss condition was analyzed, and a maxillofacial implant initial design was identified. Three-dimensional (3D) CAD models of the implant prototypes were designed that match the patient’s anatomy and dental implant requirement. In this preliminary stage, the CAD models of the prototypes were designed in a simplified form. MF³ printing of the prototypes was simulated to investigate potential deformation and residual stresses. The patient-specific implant prototypes were fabricated by MF³ printing followed by debinding and sintering using a support structure for the first time. MF³ printed green part dimensions fairly matched with simulation prediction. Sintered parts were characterized for surface integrity after cutting the support structures off. An overall 18 ± 2% shrinkage was observed in the sintered parts relative to the green parts. A relative density of 81 ± 4% indicated 19% total porosity including 11% open interconnected porosity in the sintered parts, which would favor bone healing and high osteointegration in the metallic implants. The surface roughness of Ra: 18 ± 5 µm and a Rockwell hardness of 6.5 ± 0.8 HRC were observed. The outcome of the work can be leveraged to further investigate the potential of MF³ to manufacture patient-specific custom implants out of Ti-6Al-4V.

Validation of 3D printing materials for high dose-rate brachytherapy using ionisation chamber and custom phantom

Methods.Measurements were taken with the Exradin A20 (Standard Imaging) ionisation chamber, and the 'homemade' MARM phantom was made with the 3D Ultimaker 2+ printer using PLA material. The material used for validation was ABS Medical from Smart Materials 3D. The irradiation was undertaken with a¹⁹²Ir source by means of Varian's GammaMed Plus iX HDR equipment. EBT3 films were used to run additional tests. We compared different measurements for PLA, ABS Medical, and water. Additional validation methods, described in the bibliography, were also compared.Results.The measurements with the ionisation chamber that we obtained using the MARM phantom with PLA and ABS within the clinically relevant range (0.5-1.5 cm) differ with respect to the measures in the water reference, by 2.3% and 0.94%, respectively.Discussion.The literature describes highly heterogeneous validation methods, complicating the performance of systematic reviews and comparisons between materials. Thus, creating a phantom represents a single effort that will quickly pay off. This system enables comparisons, ensuring that geometric conditions remain stable-something that is not always possible with radiochromic films. The use of a calibrated ionisation chamber in the corresponding energy range, combined with the 'homemade' MARM phantom applied according to the proposed methodology, allows a differentiation between the attenuation of the material itself and the drop in the dose due to distance.Conclusion.The validation method for 3D printing materials, using an ionisation chamber and the MARM PLA phantom, represents an accessible, standardisable solution for manufacturing brachytherapy applicators.

The Application of Pre-operative Three-Dimensional Models in the Management of Mandibular Pathology: Is it Really Useful? An Institutional Study

Aim

To assess the usefulness of 3D models for the surgical management of mandibular pathology requiring resection with continuity defects reconstructed using reconstruction plates.

Patients and Method

A bidirectional study was conducted in 40 patients, 20 each in group 1 and 2. Group 1 included those patients taken up for resection with continuity defects and reconstruction using reconstruction plates without using 3D models and Group 2 included those patients managed similarly with 3D models. Pre-operative pathological model and mirrored model was fabricated for accurate placement and pre-bending of plates and determining the position and length of the screws. The level of understanding of the patients with regards to the diagnosis and extent of the disease (VAS 0-10), treatment planning (VAS 0-10), accuracy of fixation by a blinded surgeon (VAS 0-5), operative time, change in the mouth Opening, occlusal disturbance, implant-related complications was assessed as outcome measures and tested statistically.

Results

The level of understanding of the patients with regards to the diagnosis and extent of the disease, treatment planning, operative time and accuracy of fixation was found to be statistically significant with superior performance in Group 2. No statistical significance was elicited in the change in mouth opening. No limitation in the mandibular range of movements and occlusal disturbance was found in any patient. No implant-related complications were found during the follow-up.

Conclusion

3D model fabrication can serve as a valuable adjunct in improving clinical outcomes with minimal operating time, increased patient compliance and radiological accuracy of fixation.

Improving Oral Surgery: A Workflow Proposal to Create Custom 3D Templates for Surgical Procedures

Background:

Computer-guided technologies are adopted in various fields of surgery to limit invasiveness and obtain patient benefits in terms of surgery duration and post-operative course. Surgical templates realized through CAD/CAM technologies are widely diffused in implant dentistry. The aim of this work is to propose, beyond implantology, the feasibility of application of 3D printed surgical templates in oral surgery procedures requiring osteotomies (like maxillary cyst enucleation and tooth disimpaction) in order to obtain accurate surgeries, avoid anatomical damage of surrounding structures and decrease patient’s morbidity, using a simple, low-cost protocol of fabrication.

Objective:

To provide a reliable CAD-CAM workflow for the realization of surgical templates in oral surgery.

Methods:

Three clinical scenarios are described: A maxillary canine disimpaction, a mandibular cyst removal, and an orthodontic miniscrew placement. Each one was managed using custom surgical templates realized using the proposed workflow. A Stereolithography (STL) file of maxillary structures was obtained by the use of a 3D medical image processing software (Materialise Mimics 20.0) a segmentation toolbox acquiring RX volumes by Cone-Beam Computed Tomography (CBCT). Digital models of the teeth, acquired as STL files directly, are imported in the same 3D medical image processing freeware (Materialise Mimics 20.0) to merge STL files of maxillary structures and teeth. Data are transported into Blue Sky Plan 4.0 (Blue Sky Bio, LLC), a software for 3D implant guides fabrication, together with the DICOM images package of maxillary volumes to carry out the pre-surgical treatment planning. Anatomical structures at risk are identified; a contour of ideal incision shape and bone osteotomy extent is drawn. Finally, the resulting three-dimensional guide is digitally generated and the surgical guide printed. The resulting 3D template shows the following major features: teeth support, flap management and bone osteotomy design.

Results:

The proposed work-flow aided the surgeon in both pre-operative and intra-operative work phases through accurate virtual planning and the fabrication of precise surgical guides to be used in oral surgery practice. In each clinical scenario, the use of custom 3D templates allowed better control of the osteotomy planes and flap management. No adverse events occurred during both surgical and healing phases.

Conclusion:

The proposed digital workflow represents a reliable and straightforward way to produce a surgical guide for oral surgery procedures. These templates represent a versatile tool in maxillary cyst enucleations, tooth disimpaction, and other surgical procedures, increasing accuracy, minimizing surgical complications, and decreasing patient’s morbidity.

Imaging Factors Impacting on Accuracy and Radiation Dose in 3D Printing

Objectives

To compare reconstructed area and surface roughness of 3D models acquired using nine image acquisition protocols. Radiation dose was also compared among acquisition protocols.

Methods

A dry craniofacial specimen was scanned using three CT devices (a cone beam CT, a 16-channel fan beam CT, and a 64-channel fan beam CT), with three different acquisition protocols each. Nine 3D models were manufactured using polylactic acid. Surface roughness and reconstructed area were determined for each 3D model. The radiation dose during acquisitions was measured using lithium crystals. ANOVA was used to compare the data among the 3D models. Linear function optimization techniques based on stochastic variables were applied to identify the most suitable protocol for use.

Results

For surface roughness, statistically significant differences were observed among all 3D models and the specimen. For reconstructed area, CBCT and one CT-16 channel protocols originated 3D models statistically significant different from the specimen. Higher radiation doses were observed with fan beam CT acquisitions.

Conclusions

All three CT devices were suitable for 3D printing when used at full resolution. The highest reconstruct area vs. radiation dose ratio was found for 64-channel CT devices.