Complex Facial Deformity Reconstruction With a Surgical Guide Incorporating a Built-in Occlusal Stent as the Positioning Reference:

The effects of manufacturing technologies on the surface accuracy of CAD-CAM occlusal splints

PURPOSE

To investigate the effects of the manufacturing technologies on the surface (cameo and intaglio) accuracy (trueness and precision) of computer-aided design and computer-aided manufacturing (CAD-CAM) occlusal splints.

MATERIALS AND METHODS

The digital design of the master occlusal splint was designed in a CAD software program. Six groups (n = 10) were tested in this study, including Group 1 - Milling (Wax), Group 2 - Heat-polymerizing, Group 3 - Milling (M series), Group 4 - Milling (DWX-51/52D), Group 5 - 3D-printing (Cares P30), and Group 6 - 3D-printing (M2). The study samples were placed in a scanning jig fabricated from putty silicone and Type III dental stone. The study samples were then scanned with a laboratory scanner at the intaglio and cameo surfaces, and the scanned files were exported in standard tessellation language (STL) file format. The master occlusal splint STL file, was used as a reference to compare with all scanned samples at the intaglio and cameo surfaces in a surface matching software program. Root mean square (RMS, measured in mm, absolute value) values were calculated by the software for accuracy comparisons. Group means were used as the representation of trueness, and the standard deviation for each group was calculated as a measure of precision. Color maps were recorded to visualize the areas of deviation between study samples and the master occlusal splint file. The data were normalized and transformed to rank scores, and one-way ANOVA was used to test for the differences between the groups. Pairwise comparisons were made between different groups. Fishers least square differences were used to account for the family-wise error rate. A 5% significance level was used for all the tests.

RESULTS

The null hypotheses were rejected. The manufacturing technologies significantly affected the trueness of occlusal splints at both intaglio and cameo surfaces (p < 0.001). At the cameo surfaces, Group 1 - Milling (Wax) (0.03 ± 0.02 mm), Group 3 - Milling (M series) (0.04 ± 0.01 mm), and Group 4 - Milling (DWX-51/52D) (0.04 ± 0.01 mm) had the smallest mean RMS values and highest trueness. Group 3 had the smallest standard deviation and highest precision among all groups (p < 0.001, except p = 0.005 when compared with Group 2). Group 5 had the largest standard deviation and lowest precision among all groups (p < 0.001). At the intaglio surfaces, Group 1 - Milling (Wax) (0.06 ± 0.01 mm) had the smallest RMS values and highest trueness among all groups (p < 0.001), and Group 2 - Heat-polymerizing (0.20 ± 0.03 mm) and Group 5 - 3D-printing (Cares P30) (0.15 ± 0.05 mm) had significantly larger mean RMS and standard deviation values than all other groups (p < 0.001), with lowest trueness and precision. In the color maps, Group 2 - Heat-polymerizing and Group 5 - 3D-printing (Cares P30) showed the most discrepancies with yellow and red (positive discrepancies) in most areas, and Group 1 - Milling (Wax) showed the best and most uniform surface matching with the most area in green.

CONCLUSION

The manufacturing technologies significantly affected the trueness and precision of occlusal splints at both intaglio and cameo surfaces. The 5-axis milling units and industrial-level CLIP 3D-printer could be considered to achieve surface accuracy of occlusal splints.

Patient-Specific Three-Dimensional Printing Guide for Single-Stage Skull Bone Tumor Surgery: Novel Software Workflow with Manufacturing of Prefabricated Jigs for Bone Resection and Reconstruction

OBJECTIVE

To describe a novel system workflow to design and manufacture patient-specific three-dimensional (3D) printing jigs for single-stage skull bone tumor excision and reconstruction and to present surgical outcomes of 14 patients.

METHODS

A specific computer-aided design/computer-aided manufacturing software and hardware system was set up, including a virtual surgical planning subsystem and a 3D printing-associated manufacturing subsystem. Computed tomography data of the patient's skull were used for 3D rendering of the skull and tumor. The output of patient-specific designing included a 3D printing guide for tumor resection and a 3D printing model of the bone defect after tumor excision. A polymethyl methacrylate implant was fabricated preoperatively and used for repair.

RESULTS

The specific 3D printing guide was used to design intraoperative jigs and implants for 14 patients (age range, 1-72 years) with skull bone tumors. In all cases, the cutting jig allowed precise excision of tumor and bone, and implants were exact fits for the defects created. All operative results were successful, without intraoperative or postoperative complications. Postoperative computed tomography scans were obtained for analysis. Postoperative 3D measurement of the skull symmetry index (cranial vault asymmetry index) showed significant improvement of head contour after surgery.

CONCLUSIONS

The computer-aided design/computer-aided manufacturing system described allows definitive preoperative planning and fabrication for treatment of skull bone tumors. Apparent benefits of the method include more accurate determination of surgical margins and better oncological outcomes.

A simple method to estimate the linear length of the orbital floor in complex orbital surgery

BACKGROUND

The orbital floor (OrF) and infraorbital rim (IOR) repair in cases of complete destruction is challenging mainly due to the fact that the defect length cannot be measured. The aim of the current study is to develop a method of calculating the Orf length by using the gender and the lengths of the medial, superior and lateral orbital walls (OrW) of the same orbit.

MATERIAL AND METHODS

Ninety-seven (59 male and 38 female) European adult dry skulls were classified according to age: 20-39, 40-59 and 60 years and above. The length of each OrW was measured by using the direct distance between the optic foramen and a landmark in each orbital rim.

RESULTS

A side asymmetry was detected for the lengths of the inferior, superior and medial OrW. Although a gender dimorphism was detected, no correlation with the age was found. Using the Stepwise multiple regression analysis two formulas were developed, one for the right and one for the left OrF with coefficient of determination R² 0.43 and 0.57, respectively.

CONCLUSIONS

The proposed formulas represent a simple, applicable and individualized method to calculate the OrF linear length in cases of complete destruction of the IOR and OrF, with accuracy and without the use of expertise material. Such data may improve the surgery planning of orbital floor fractures and complex orbital reconstructions.

Radiological Society of North America (RSNA) 3D printing Special Interest Group (SIG): guidelines for medical 3D printing and appropriateness for clinical scenarios

Medical three-dimensional (3D) printing has expanded dramatically over the past three decades with growth in both facility adoption and the variety of medical applications. Consideration for each step required to create accurate 3D printed models from medical imaging data impacts patient care and management. In this paper, a writing group representing the Radiological Society of North America Special Interest Group on 3D Printing (SIG) provides recommendations that have been vetted and voted on by the SIG active membership. This body of work includes appropriate clinical use of anatomic models 3D printed for diagnostic use in the care of patients with specific medical conditions. The recommendations provide guidance for approaches and tools in medical 3D printing, from image acquisition, segmentation of the desired anatomy intended for 3D printing, creation of a 3D-printable model, and post-processing of 3D printed anatomic models for patient care.

Development and initial porcine and cadaver experience with three-dimensional printing of endoscopic and laparoscopic equipment

INTRODUCTION

Recent advances in three-dimensional (3D) printing technology have made it possible to print surgical devices. We report our initial experience with the printing and deployment of endoscopic and laparoscopic equipment.

MATERIALS AND METHODS

We created computer-aided designs for ureteral stents and laparoscopic trocars using SolidWorks. We developed three generations of stents, which were printed with an Objet500 Connex printer, and a fourth generation was printed with an EOSINT P395 printer. The trocars were printed with an Objet30 Pro printer. We deployed the printed stents and trocars in a female cadaver and in vivo porcine model. We compared the printed trocars to two standard trocars for defect area and length using a digital caliper. Paired T-tests and ANOVA were used to test for statistical difference.

RESULTS

The first two generations of stents (7F and 9F) were functional failures as their diminutive inner lumen failed to allow the passage of a 0.035 guidewire. The third generation 12F stent allowed passage of a 0.035 guidewire. The 12F diameter limited its deployment, but it was introduced in a cadaver through a ureteral access sheath. The fourth-generation 9F stents were printed and deployed in a porcine model using the standard Seldinger technique. The printed trocars were functional for the maintenance of the pneumoperitoneum and instrument passage. The printed trocars had larger superficial defect areas (p<0.001) and lengths (p=0.001) compared to Karl Storz and Ethicon trocars (29.41, 18.06, and 17.22 mm(2), respectively, and 14.29, 11.39, and 12.15 mm, respectively).

CONCLUSIONS

In this pilot study, 3D printing of ureteral stents and trocars is feasible, and these devices can be deployed in the porcine and cadaver models. Three-dimensional printing is rapidly advancing and may be clinically viable in the future.

Anti-Reflux Ureteral Stent with Polymeric Flap Valve Using Three-Dimensional Printing: An In Vitro Study

PURPOSE

This article aims to describe the design of an anti-reflux ureteral stent with a polymeric flap valve and the fabrication methods using three-dimensional (3D) printing. The stent effectively prevents backward flow with a negligible reduction in forward flow. Fabrication of miniaturized valves was easy with high precision and rapid prototyping.

MATERIALS AND METHODS

The proposed stent comprised a 7F Double-J (DJ) stent and a polymeric flap valve. The valve was made of Tango Plus FLX980 and was fabricated using a 3D printer. Two types of stent were prepared for in vitro tests: DJ stents with (1) an uncoated valve (UCV) stent and (2) a parylene C coated valve (PCV) stent for enhanced biocompatibility. The flow characteristics of each stent were evaluated considering flow direction, parylene coating, and stent side holes, and were compared to the intact DJ stent.

RESULTS

The forward flow rate for the distal portion of the UCV and PCV stents was 9.8 mL/min and 7.8 mL/min at applied pressure of 15 cm H2O (normal anterograde pressure in patients with stents), respectively. Backward flow rate for the distal portion of the UCV and PCV stents was decreased by 28 times and 8 times at applied pressure of 50 cm H2O (maximum bladder pressure), respectively, compared with the distal portion of the intact DJ stent. Forward flow rates of whole stents were 22.2 mL/min (UCV stent) and 20.0 mL/min (PCV stent) at applied pressure of 15 cm H2O, and backward flow rates of whole UCV and PCV stents were decreased by 8.3 times and 4.0 times at applied pressure of 50 cm H2O, respectively, compared with the intact DJ stent.

CONCLUSIONS

The anti-reflux ureteral stent was successfully designed and fabricated using a 3D printer. In vitro studies showed that the stent effectively prevented backward flow while minimizing reduction in forward flow.