Prototyping for surgical and prosthetic treatment

Application of Biocompatible Scaffolds in Stem-Cell-Based Dental Tissue Engineering

Tissue engineering as an important field in regenerative medicine is a promising therapeutic approach to replace or regenerate injured tissues. It consists of three vital steps including the selection of suitable cells, formation of 3d scaffolds, and adding growth factors. Mesenchymal stem cells (MSCs) and embryonic stem cells (ESCs) are mentioned as two main sources for this approach that have been used for the treatment of various types of disorders. However, the main focus of literature in the field of dental tissue engineering is on utilizing MSCs. On the other hand, biocompatible scaffolds play a notable role in this regenerative process which is mentioned to be harmless with acceptable osteoinductivity. Their ability in inhibiting inflammatory responses also makes them powerful tools. Indeed, stem cell functions should be supported by biomaterials acting as scaffolds incorporated with biological signals. Naturally derived polymeric scaffolds and synthetically engineered polymeric/ceramic scaffolds are two main types of scaffolds regarding their materials that are defined further in this review. Various strategies of tissue bioengineering can affect the regeneration of dentin-pulp complex, periodontium regeneration, and whole teeth bioengineering. In this regard, in vivo/ex vivo experimental models have been developed recently in order to perform preclinical studies of dental tissue engineering which make it more transferable to be used for clinic uses. This review summarizes dental tissue engineering through its different components. Also, strategies of tissue bioengineering and experimental models are introduced in order to provide a perspective of the potential roles of dental tissue engineering to be used for clinical aims.

[CAD/CAM assisted facial epithesis: Clinical and technical aspects]

The face is an important part of the human body from an anatomical, functional, aesthetic and psychosocial point of view. It can be the site of several mutilations resulting from trauma, treatment of neoplasms and congenital malformations. The plastic facial prosthesis is therefore indicated to restore these facial deformities and to compensate for the various consequences. Recently, digital technologies have shown an increasing impact on the future of maxillofacial rehabilitation. Computer-aided design and manufacturing technique enabled practitioners to acquire numerical data, perform three-dimensional reconstructions, and then materialize and manufacture the facial epithesis through various manufacturing processes, by addition or subtraction. The aim of this article is to describe, through a clinical case, the steps of realization of a nasal epithesis by CAD/CAM, in a patient who underwent a surgical exeresis of the nasal pyramid following a squamous cell carcinoma. Thus, the clinical and technical aspects are highlighted, as follows, the taking of the impression, the materials used, the set-up and the make-up, as well as the software and the useful concepts for the computer-assisted realization of a facial plastic prosthesis of the nasal epithesis type. Our therapy will also focus on the interest of the multidisciplinary approach in Maxillofacial Prosthodontics.

Three-Dimensional Technology in Rhinoplasty

Rhinoplasty is uniquely suited to capitalize on different aspects of three-dimensional (3D) modeling technology. Currently, 3D surface imaging of preoperative and postoperative nasal structure provides a platform for better surgical planning and patient counselling as well as objective postoperative measurements. Physical nasal models using 3D printing technology can improve rhinoplasty performance intraoperatively, postoperative outcomes, together with nasal prosthetic manufacture, by tailoring to specific patient anatomy. Advances in tissue engineering using 3D-printed biocompatible scaffolds have shown excellent nasal cartilage mimicry and hold promise for increasingly versatile directed tissue regeneration in rhinoplasty and nasal reconstructive surgery. As health care innovations are expected to become increasingly common in standard rhinoplasty practices in the future, we give an account of how 3D technologies can create new opportunities to optimize surgical planning and improve overall the patient experience.

Comparison of Overall Fit of Milled and Laser-Sintered CAD/CAM Crown Copings

Background and Aims

The aim of this study was to investigate the effect of computer-aided design/computer-aided manufacturing (CAD/CAM) procedures on the overall fit of metal copings.

Materials and Methods

A standardized die was made in die stone of an upper right molar prepared for a full crown. The die was digitalized by an Identica Blue Light Scanner, and the coping substructure was designed using CAD software. Ten milled specimens and ten laser-sintered specimens were manufactured by Renishaw plc based on the generated file by the software. All twenty copings were digitized by the Identica scanner, and the data were superimposed with the original premanufacturing data file of the prepared full crown. Using the Geometric Modelling Library (GML) package, the fit discrepancies were displayed as colour maps showing discrepancies in three dimensions. Each map was made up of thousands of data points carrying numerical error values allowing detailed analyses.

Results

The milled group displayed a mean of fit discrepancies of 42.20 μm (SD 3.04 μm), while the laser-sintered group showed a mean of 42.24 μm fit discrepancies (SD 2.94 μm). Thus, a small difference of 0.04 μm between the two groups was detected.

Conclusions

The evaluated manufacturing systems can be used in dental practice as a small and insignificant discrepancy of fit between the two manufacturing methods was detected.

Tissue Engineering and 3-Dimensional Modeling for Facial Reconstruction

Three-dimensional (3D) printing has transformed craniofacial reconstruction over the last 2 decades. For cutaneous oncologic surgeons, several 3D printed technologies are available to assist with craniofacial bony reconstruction and preliminary soft tissue reconstructive efforts. With improved accessibility and simplified design software, 3D printing has opened the door for new techniques in anaplastology. Tissue engineering has more recently emerged as a promising concept for complex auricular and nasal reconstruction. Combined with 3D printing, several groups have demonstrated promising preclinical results with cartilage growth. This article highlights the applications and current state of 3D printing and tissue engineering in craniofacial reconstruction.

Clinical value of 3D printing guide plate in core decompression plus porous bioceramics rod placement for the treatment of early osteonecrosis of the femoral head

BACKGROUND

The conventional method of core decompression combined with porous bioceramics rod is usually performed under C-arm fluoroscopy for the treatment of early osteonecrosis of the femoral head (ONFH). This study was to evaluate the clinical value and efficacy of three-dimensional (3D) printing guide plate in the process of core decompression plus porous bioceramics rod for the treatment of early ONFH.

METHODS

Forty patients were enrolled, including 20 patients undergoing the surgery with 3D printing guide plate in the experiment group and 20 controls with C-arm fluoroscopy. The following parameters such as surgery time, blood loss, fluoroscopy times, and the accuracy of core decompression for necrosis area, function outcome according to Harris Hip Score (HHS), and any possible complications were recorded and compared between the two groups. All the patients were followed up at 6, 12, and 18 months postoperatively.

RESULTS

The surgery time, fluoroscopy time, and intraoperative blood loss in the experiment group was significantly less (P < 0.05) than those in the control group. There was no statistical significance in the accuracy of core decompression and porous bioceramics rod placement between the two groups (P > 0.05). All patients were followed up for 18 months. There was a significant difference between the preoperative and final follow-up HSS scores in both groups (P < 0.05). In addition, there was also a significant difference between the groups in the last follow-up HSS scores (P < 0.05).

CONCLUSIONS

Compared with the traditional method, 3D printing guide plate could shorten the surgery time and fluoroscopy times and decrease intraoperative blood loss. It seems to be an effective method in the combined core decompression with porous bioceramics rod placement for early ONFH.

Clinical application of 3D technology for tooth autotransplantation: A case report

This report presents two cases of tooth autotransplantation using cone-beam computed tomography (CBCT), the three-dimensional (3D) simulation dental planning software and a computer-aided rapid prototyping (CARP) model. Two hopeless teeth of adult patients were replaced as their third molar teeth. Before deciding the autotransplantation, diagnostic CBCT images were acquired and imported to SimPlant software. The SimPlant dental program was used for surgical simulation prior to autotransplantation, which created 3D images of the available donor teeth and recipient site tooth and superimposed the images to display their morphological similarity. Efficient modification of the recipient socket was designed preoperatively. The CARP model of the donor tooth was prepared as a substitute for the donor tooth that would be fit into the new recipient socket during bone preparation. Autotransplantation was favourably performed in 5-6 min. Transplanted teeth healed up without clinical abnormality. The postoperative follow-up time was up to 6 years.

[Additive technologies in neurosurgery]

Modern achievements of technical progress, in particular additive technologies (ATs) and three-dimensional printing, have been increasingly introduced in neurosurgical practice. The increasing complexity of surgical interventions requires thorough planning of surgery and a high level of training of young neurosurgeons. Creation of full-scale three-dimensional models for planning of surgery enables visualization of the anatomical region of interest. Additive technologies are especially extensively used in reconstructive surgery of skull defects. ATs enable fast and efficient solving of the following tasks: - generation of accurate models of the skull and an implant; - development and fabrication of individual molds for intraoperative formation of implants from polymeric two-component materials (e.g., PMMA); - fabrication of individual implants from titanium alloys or polyetheretherketone (PEEK) for further use in surgery.

Error Analysis: How Precise is Fused Deposition Modeling in Fabrication of Bone Models in Comparison to the Parent Bones?

BACKGROUND

Rapid prototyping (RP) is used widely in dental and faciomaxillary surgery with anecdotal uses in orthopedics. The purview of RP in orthopedics is vast. However, there is no error analysis reported in the literature on bone models generated using office-based RP. This study evaluates the accuracy of fused deposition modeling (FDM) using standard tessellation language (STL) files and errors generated during the fabrication of bone models.

MATERIALS AND METHODS

Nine dry bones were selected and were computed tomography (CT) scanned. STL files were procured from the CT scans and three-dimensional (3D) models of the bones were printed using our in-house FDM based 3D printer using Acrylonitrile Butadiene Styrene (ABS) filament. Measurements were made on the bone and 3D models according to data collection procedures for forensic skeletal material. Statistical analysis was performed to establish interobserver co-relation for measurements on dry bones and the 3D bone models. Statistical analysis was performed using SPSS version 13.0 software to analyze the collected data.

RESULTS

The inter-observer reliability was established using intra-class coefficient for both the dry bones and the 3D models. The mean of absolute difference is 0.4 that is very minimal. The 3D models are comparable to the dry bones.

CONCLUSIONS

STL file dependent FDM using ABS material produces near-anatomical 3D models. The high 3D accuracy hold a promise in the clinical scenario for preoperative planning, mock surgery, and choice of implants and prostheses, especially in complicated acetabular trauma and complex hip surgeries.

Maxillofacial prostheses challenges in resource constrained regions

BACKGROUND

This study reviewed the current state of maxillofacial rehabilitation in resource-limited nations.

METHOD

A rigorous literature review was undertaken using several technical and clinical databases using a variety of key words pertinent to maxillofacial prosthetic rehabilitation and resource-limited areas. In addition, interviews were conducted with researchers, clinicians and prosthetists that had direct experience of volunteering or working in resource-limited countries.

RESULTS

Results from the review and interviews suggest rehabilitating patients in resource-limited countries remains challenging and efforts to improve the situation requires a multifactorial approach.

CONCLUSIONS

In conclusion, public health awareness programmes to reduce the causation of injuries and bespoke maxillofacial prosthetics training programmes to suit these countries, as opposed to attempting to replicate Western training programmes. It is also possible that usage of locally sourced and cheaper materials and the use of low-cost technologies could greatly improve maxillofacial rehabilitation efforts in these localities. Implications for Rehabilitation More information and support needs to be provided to maxillofacial defect/injuries patients and to their families or guardians in a culturally sensitive manner by governments. The health needs, economic and psychological needs of the patients need to be taken into account during the rehabilitation process by clinicians and healthcare organizations. The possibility of developing training programs to suit these resource limited countries and not necessarily follow conventional fabrication methods must be looked into further by educational entities.

Reconstruction of Frontal Bone With Custom-Made Prosthesis Using Rapid Prototyping

Frontal bone fracture treatment is still an issue of research in craniofacial surgery and neurosurgery. The aims of the treatment are to reduce the complication risks and to keep the aesthetic of the face. Before the management of this fracture type, it is necessary to consider the permanence or not of the frontal sinus function. Rapid prototyping has been an aid tool on planning and simulation of the surgical procedure, improving the diagnostic quality and the implant manufacture, beyond reducing the operative time. Among the used materials on treatment of these fractures, titanium mesh shows large versatility and ease of handling. Poly(methyl methacrylate) has been used in defects of partial thickness or irregularities on cranial surface. The aim of this study is to report a case of a patient presenting sequelae of large fracture of anterior wall of frontal bone, treated by a titanium mesh associated with the customized poly(methyl methacrylate) implant from the rapid prototyping. It could be concluded that the use of this technique showed itself effective on patient treatment, and rapid prototyping demonstrated being a valuable tool showing predictable and satisfactory results.

Three-Dimensional Printing: Custom-Made Implants for Craniomaxillofacial Reconstructive Surgery

Craniomaxillofacial reconstructive surgery is a challenging field. First it aims to restore primary functions and second to preserve craniofacial anatomical features like symmetry and harmony. Three-dimensional (3D) printed biomodels have been widely adopted in medical fields by providing tactile feedback and a superior appreciation of visuospatial relationship between anatomical structures. Craniomaxillofacial reconstructive surgery was one of the first areas to implement 3D printing technology in their practice. Biomodeling has been used in craniofacial reconstruction of traumatic injuries, congenital disorders, tumor removal, iatrogenic injuries (e.g., decompressive craniectomies), orthognathic surgery, and implantology. 3D printing has proven to improve and enable an optimization of preoperative planning, develop intraoperative guidance tools, reduce operative time, and significantly improve the biofunctional and the aesthetic outcome. This technology has also shown great potential in enriching the teaching of medical students and surgical residents. The aim of this review is to present the current status of 3D printing technology and its practical and innovative applications, specifically in craniomaxillofacial reconstructive surgery, illustrated with two clinical cases where the 3D printing technology was successfully used.

Abdo-Man: a 3D-printed anthropomorphic phantom for validating quantitative SIRT

BACKGROUND

The use of selective internal radiation therapy (SIRT) is rapidly increasing, and the need for quantification and dosimetry is becoming more widespread to facilitate treatment planning and verification. The aim of this project was to develop an anthropomorphic phantom that can be used as a validation tool for post-SIRT imaging and its application to dosimetry.

METHOD

The phantom design was based on anatomical data obtained from a T1-weighted volume-interpolated breath-hold examination (VIBE) on a Siemens Aera 1.5 T MRI scanner. The liver, lungs and abdominal trunk were segmented using the Hermes image processing workstation. Organ volumes were then uploaded to the Delft Visualization and Image processing Development Environment for smoothing and surface rendering. Triangular meshes defining the iso-surfaces were saved as stereo lithography (STL) files and imported into the Autodesk® Meshmixer software. Organ volumes were subtracted from the abdomen and a removable base designed to allow access to the liver cavity. Connection points for placing lesion inserts and filling holes were also included. The phantom was manufactured using a Stratasys Connex3 PolyJet 3D printer. The printer uses stereolithography technology combined with ink jet printing. Print material is a solid acrylic plastic, with similar properties to polymethylmethacrylate (PMMA).

RESULTS

Measured Hounsfield units and calculated attenuation coefficients of the material were shown to also be similar to PMMA. Total print time for the phantom was approximately 5 days. Initial scans of the phantom have been performed with Y-90 bremsstrahlung SPECT/CT, Y-90 PET/CT and Tc-99m SPECT/CT. The CT component of these images compared well with the original anatomical reference, and measurements of volume agreed to within 9 %. Quantitative analysis of the phantom was performed using all three imaging techniques. Lesion and normal liver absorbed doses were calculated from the quantitative images in three dimensions using the local deposition method.

CONCLUSIONS

3D printing is a flexible and cost-efficient technology for manufacture of anthropomorphic phantom. Application of such phantoms will enable quantitative imaging and dosimetry methodologies to be evaluated, which with optimisation could help improve outcome for patients.

Application of Computer-Aided Designing and Rapid Prototyping Technologies in Reconstruction of Blowout Fractures of the Orbital Floor

INTRODUCTION

Traumatology of the maxillofacial region represents a wide range of different types of facial skeletal injuries and encompasses numerous treatment methods. Application of computer-aided design (CAD) in combination with rapid prototyping (RP) technologies and three-dimensional computed tomography techniques facilitates surgical therapy planning for efficient treatment.

OBJECTIVE

The purpose of this study is to determine the efficiency of individually designed implants of poly-DL-lactide (PDLLA) in the reconstruction of blowout fractures of the orbital floor.

METHODS

In the course of a surgical treatment, individually designed implants manufactured by CAD/RP technologies were used. Preoperative analysis and postoperative monitoring were conducted to evaluate the successfulness of orbital floor reconstruction using customized PDLLA implants, based on: presence of diplopia, paresthesia of infraorbital nerve, and presence of enophthalmos.

RESULTS

In 6 of the 10 patients, diplopia completely disappeared immediately after surgical procedure. Diplopia gradually disappeared after 1 month in 3 patients, whereas in 1, it remained even after 6 months. In 7 patients, paresthesia disappeared within a month after surgery and in 3 patients within 2 months. Postoperative average Orbital volume (OV) of the injured side (13.333 ± 3.177) was significantly reduced in comparison with preoperative OV (15.847 ± 3.361) after reconstruction of the orbital floor with customized PDLLA implant (P < 0.001). Thus, average OV of corrected orbit was not different compared with the OV of the uninjured orbit (P = 0.981).

CONCLUSIONS

Reconstruction of blowout fractures of the orbital floor by an individually designed PDLLA implant combined with virtual preoperative modeling allows easier preoperative preparation and yields satisfactory functional and esthetic outcomes.

Additive manufacturing of collagen scaffolds by three-dimensional plotting of highly viscous dispersions

Additive manufacturing (AM) allows the free form fabrication of three-dimensional (3D) structures with distinct external geometry, fitting into a patient-specific defect, and defined internal pore architecture. However, fabrication of predesigned collagen scaffolds using AM-based technologies is challenging due to the low viscosity of collagen solutions, gels or dispersions commonly used for scaffold preparation. In the present study, we have developed a straightforward method which is based on 3D plotting of a highly viscous, high density collagen dispersion. The swollen state of the collagen fibrils at pH 4 enabled the homogenous extrusion of the material, the deposition of uniform strands and finally the construction of 3D scaffolds. Stabilization of the plotted structures was achieved by freeze-drying and chemical crosslinking with the carbodiimide EDC. The scaffolds exhibited high shape and dimensional fidelity and a hierarchical porosity consisting of macropores generated by strand deposition as well as an interconnected microporosity within the strands as result of the freeze-drying process. Cultivation of human mesenchymal stromal cells on the scaffolds, with and without adipogenic or osteogenic stimulation, revealed their cytocompatibility and potential applicability for adipose and bone tissue engineering.

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

Background

The use of rapid prototyping (RP) models in medicine to construct bony models is increasing.

Material and Methods

The aim of the study was to evaluate retrospectively the indication for the use of RP models in oral and maxillofacial surgery at Helsinki University Central Hospital during 2009-2010. Also, the used computed tomography (CT) examination – multislice CT (MSCT) or cone beam CT (CBCT) - method was evaluated.

Results

In total 114 RP models were fabricated for 102 patients. The mean age of the patients at the time of the production of the model was 50.4 years. The indications for the modelling included malignant lesions (29%), secondary reconstruction (25%), prosthodontic treatment (22%), orthognathic surgery or asymmetry (13%), benign lesions (8%), and TMJ disorders (4%). MSCT examination was used in 92 and CBCT examination in 22 cases. Most of the models (75%) were conventional hard tissue models. Models with colored tumour or other structure(s) of interest were ordered in 24%. Two out of the 114 models were soft tissue models.

Conclusions

The main benefit of the models was in treatment planning and in connection with the production of pre-bent plates or custom made implants. The RP models both facilitate and improve treatment planning and intraoperative efficiency.

Key words:Rapid prototyping, radiology, computed tomography, cone beam computed tomography.

Presurgical nasoalveolar molding for cleft lip and palate: the application of digitally designed molds

BACKGROUND

The authors present a novel nasoalveolar molding protocol by prefabricating sets of nasoalveolar molding appliances using three-dimensional technology.

METHODS

Prospectively, 17 infants with unilateral complete cleft lip and palate underwent the authors' protocol before primary cheiloplasty. An initial nasoalveolar molding appliance was created based on the patient's first and only in-person maxillary cast, produced from a traditional intraoral dental impression. Thereafter, each patient's molding course was simulated using computer software that aimed to narrow the alveolar gap by 1 mm each week by rotating the greater alveolar segment. A maxillary cast of each predicted molding stage was created using three-dimensional printing. Subsequent appliances were constructed in advance, based on the series of computer-generated casts. Each patient had a total three clinic visits spaced 1 month apart. Anthropometric measurements and bony segment volumes were recorded before and after treatment.

RESULTS

Alveolar cleft widths narrowed significantly (p < 0.01), soft-tissue volume of each segment expanded (p < 0.01), and the arc of the alveolus became more contiguous across the cleft (p < 0.01). One patient required a new appliance at the second visit because of bleeding and discomfort. Eleven patients had mucosal irritation and two experienced minor mucosal ulceration.

CONCLUSIONS

Three-dimensional technology can precisely represent anatomic structures in pediatric clefts. Results from the authors' algorithm are equivalent to those of traditional nasoalveolar molding therapies; however, the number of required clinic visits and appliance adjustments decreased. As three-dimensional technology costs decrease, multidisciplinary teams may design customized nasoalveolar molding treatment with improved efficiency and less burden to medical staff, patients, and families.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Emerging Applications of Bedside 3D Printing in Plastic Surgery

Modern imaging techniques are an essential component of preoperative planning in plastic and reconstructive surgery. However, conventional modalities, including three-dimensional (3D) reconstructions, are limited by their representation on 2D workstations. 3D printing, also known as rapid prototyping or additive manufacturing, was once the province of industry to fabricate models from a computer-aided design (CAD) in a layer-by-layer manner. The early adopters in clinical practice have embraced the medical imaging-guided 3D-printed biomodels for their ability to provide tactile feedback and a superior appreciation of visuospatial relationship between anatomical structures. With increasing accessibility, investigators are able to convert standard imaging data into a CAD file using various 3D reconstruction softwares and ultimately fabricate 3D models using 3D printing techniques, such as stereolithography, multijet modeling, selective laser sintering, binder jet technique, and fused deposition modeling. However, many clinicians have questioned whether the cost-to-benefit ratio justifies its ongoing use. The cost and size of 3D printers have rapidly decreased over the past decade in parallel with the expiration of key 3D printing patents. Significant improvements in clinical imaging and user-friendly 3D software have permitted computer-aided 3D modeling of anatomical structures and implants without outsourcing in many cases. These developments offer immense potential for the application of 3D printing at the bedside for a variety of clinical applications. In this review, existing uses of 3D printing in plastic surgery practice spanning the spectrum from templates for facial transplantation surgery through to the formation of bespoke craniofacial implants to optimize post-operative esthetics are described. Furthermore, we discuss the potential of 3D printing to become an essential office-based tool in plastic surgery to assist in preoperative planning, developing intraoperative guidance tools, teaching patients and surgical trainees, and producing patient-specific prosthetics in everyday surgical practice.

Rapid prototyping-assisted maxillofacial reconstruction

Rapid prototyping (RP) technologies have found many uses in dentistry, and especially oral and maxillofacial surgery, due to its ability to promote product development while at the same time reducing cost and depositing a part of any degree of complexity theoretically. This paper provides an overview of RP technologies for maxillofacial reconstruction covering both fundamentals and applications of the technologies. Key fundamentals of RP technologies involving the history, characteristics, and principles are reviewed. A number of RP applications to the main fields of oral and maxillofacial surgery, including restoration of maxillofacial deformities and defects, reduction of functional bone tissues, correction of dento-maxillofacial deformities, and fabrication of maxillofacial prostheses, are discussed. The most remarkable challenges for development of RP-assisted maxillofacial surgery and promising solutions are also elaborated.

Rapid prototyping for in vitro knee rig investigations of prosthetized knee biomechanics: comparison with cobalt-chromium alloy implant material

Retropatellar complications after total knee arthroplasty (TKA) such as anterior knee pain and subluxations might be related to altered patellofemoral biomechanics, in particular to trochlear design and femorotibial joint positioning. A method was developed to test femorotibial and patellofemoral joint modifications separately with 3D-rapid prototyped components for in vitro tests, but material differences may further influence results. This pilot study aims at validating the use of prostheses made of photopolymerized rapid prototype material (RPM) by measuring the sliding friction with a ring-on-disc setup as well as knee kinematics and retropatellar pressure on a knee rig. Cobalt-chromium alloy (standard prosthesis material, SPM) prostheses served as validation standard. Friction coefficients between these materials and polytetrafluoroethylene (PTFE) were additionally tested as this latter material is commonly used to protect pressure sensors in experiments. No statistical differences were found between friction coefficients of both materials to PTFE. UHMWPE shows higher friction coefficient at low axial loads for RPM, a difference that disappears at higher load. No measurable statistical differences were found in knee kinematics and retropatellar pressure distribution. This suggests that using polymer prototypes may be a valid alternative to original components for in vitro TKA studies and future investigations on knee biomechanics.

Finite element analysis of patient-specific condyle fracture plates: a preliminary study

Various patterns of internal fixation of mandibular condyle fractures have been proposed in the literature. This study investigates the stability of two patient-specific implants (PSIs) for the open reduction and internal fixation of a subcondylar fracture of the mandible. A subcondylar fracture of a mandible was simulated by a series of finite element models. These models contained approximately 1.2 million elements, were heterogeneous in bone material properties, and also modeled the muscles of mastication. Models were run assuming linear elasticity and isotropic material properties for bone. The stability and von Mises stresses of the simulated condylar fracture reduced with each of the PSIs were compared. The most stable of the plate configurations examined was PSI 1, which had comparable mechanical performance to a single 2.0 mm straight four-hole plate.

A novel method for intraoral access to the superior head of the human lateral pterygoid muscle

Background. The uncoordinated activity of the superior and inferior parts of the lateral pterygoid muscle (LPM) has been suggested to be one of the causes of temporomandibular joint (TMJ) disc displacement. A therapy for this muscle disorder is the injection of botulinum toxin (BTX), of the LPM. However, there is a potential risk of side effects with the injection guide methods currently available. In addition, they do not permit appropriate differentiation between the two bellies of the muscle. Herein, a novel method is presented to provide intraoral access to the superior head of the human LPM with maximal control and minimal hazards. Methods. Computational tomography along with digital imaging software programs and rapid prototyping techniques were used to create a rapid prototyped guide to orient BTX injections in the superior LPM. Results. The method proved to be feasible and reliable. Furthermore, when tested in one volunteer it allowed precise access to the upper head of LPM, without producing side effects. Conclusions. The prototyped guide presented in this paper is a novel tool that provides intraoral access to the superior head of the LPM. Further studies will be necessary to test the efficacy and validate this method in a larger cohort of subjects.

Accuracy of using computer-aided rapid prototyping templates for mandible reconstruction with an iliac crest graft

Background

This study aimed to evaluate the accuracy of surgical outcomes in free iliac crest mandibular reconstructions that were carried out with virtual surgical plans and rapid prototyping templates.

Methods

This study evaluated eight patients who underwent mandibular osteotomy and reconstruction with free iliac crest grafts using virtual surgical planning and designed guiding templates. Operations were performed using the prefabricated guiding templates. Postoperative three-dimensional computer models were overlaid and compared with the preoperatively designed models in the same coordinate system.

Results

Compared to the virtual osteotomy, the mean error of distance of the actual mandibular osteotomy was 2.06 ± 0.86 mm. When compared to the virtual harvested grafts, the mean error volume of the actual harvested grafts was 1412.22 ± 439.24 mm³ (9.12% ± 2.84%). The mean error between the volume of the actual harvested grafts and the shaped grafts was 2094.35 ± 929.12 mm³ (12.40% ± 5.50%).

Conclusions

The use of computer-aided rapid prototyping templates for virtual surgical planning appears to positively influence the accuracy of mandibular reconstruction.

Complete integration of technology for improved reproduction of auricular prostheses

The accurate reproduction of the form and surface details of missing body structures is an essential part of any successful prosthetic rehabilitation. It helps mask the prosthesis and gives confidence to the patient. This clinical report details the integration of multiple in-house digital technologies of laser scanning, rapid prototyping, and digital color scanning and formulating to improve the shape, texture, orientation, and color of auricular prostheses for 3 patients with missing unilateral ears. A structured light laser scanner was used to digitize the patient's nondefect ear. The digitized data were then manipulated in specialist software and mirrored to reflect the opposing side. A rapid prototyping machine was used to manufacture a 3-dimensional (3D) model of the soft tissue required. This 3D mirrored ear model allowed the accurate reproduction of missing soft tissue. A color spectrometer was used to accurately reproduce the skin tones digitally and physically.

Effect of various veneering techniques on mechanical strength of computer-controlled zirconia framework designs

PURPOSE

The objectives of this study were to evaluate the fracture resistance (FR), flexural strength (FS), and shear bond strength (SBS) of zirconia framework material veneered with different methods and to assess the stress distributions using finite element analysis (FEA).

MATERIALS AND METHODS

Zirconia frameworks fabricated in the forms of crowns for FR, bars for FS, and disks for SBS (N = 90, n = 10) were veneered with either (a) file splitting (CAD-on) (CD), (b) layering (L), or (c) overpressing (P) methods. For crown specimens, stainless steel dies (N = 30; 1 mm chamfer) were scanned using the labside contrast spray. A bilayered design was produced for CD, whereas a reduced design (1 mm) was used for L and P to support the veneer by computer-aided design and manufacturing. For bar (1.5 × 5 × 25 mm(3) ) and disk (2.5 mm diameter, 2.5 mm height) specimens, zirconia blocks were sectioned under water cooling with a low-speed diamond saw and sintered. To prepare the suprastructures in the appropriate shapes for the three mechanical tests, nano-fluorapatite ceramic was layered and fired for L, fluorapatite-ceramic was pressed for P, and the milled lithium-disilicate ceramics were fused with zirconia by a thixotropic glass ceramic for CD and then sintered for crystallization of veneering ceramic. Crowns were then cemented to the metal dies. All specimens were stored at 37°C, 100% humidity for 48 hours. Mechanical tests were performed, and data were statistically analyzed (ANOVA, Tukey's, α = 0.05). Stereomicroscopy and scanning electron microscopy (SEM) were used to evaluate the failure modes and surface structure. FEA modeling of the crowns was obtained.

RESULTS

Mean FR values (N ± SD) of CD (4408 ± 608) and L (4323 ± 462) were higher than P (2507 ± 594) (p < 0.05). Mean FS values (MPa ± SD) of CD (583 ± 63) and P (566 ± 54) were higher than L (428 ± 41) (p < 0.05). Mean SBS values (MPa ± SD) of CD (49 ± 6) (p < 0.05) were higher than L (28 ± 5) and P (30 ± 8). For crown restorations, while cohesive failures within ceramic and zirconia were seen in CD, cohesive failures within ceramic were found in both L and P. Results were verified by FEA.

CONCLUSION

The file splitting technique showed higher bonding values in all mechanical tests, whereas a layering technique increased the FR when an anatomical core design was employed.

CLINICAL SIGNIFICANCE

File splitting (CAD-on) or layering veneering ceramic on zirconia with a reduced framework design may reduce ceramic chipping.

Revision of complex acetabular defects using cages with the aid of rapid prototyping

This study details a method using rapid prototyping (RP) technique to assist in acetabular revision with complex bone defects. Hemi-pelvic RP models were built among 25 patients with complex acetabular bone defects. Each patient was scheduled to undergo revision using either commercially available or customized cages based on individualized RP models. Average follow-up was 4.4 years (range, 1 to 9 years). The average Harris hip score was 36.1 (range, 20 to 58) preoperatively and reached an average of 82.6 (range, 60-96) at the last follow-up. No mechanical failure or loosening was observed. One patient experienced hip dislocation 4 days postoperatively. The resultant findings of this study merit consideration of RP as a helpful clinical complement for dealing with some complex bone defect of acetabulum.

Inaccuracies in additive manufactured medical skull models caused by the DICOM to STL conversion process

INTRODUCTION

The process of fabricating physical medical skull models requires many steps, each of which is a potential source of geometric error. The aim of this study was to demonstrate inaccuracies and differences caused by DICOM to STL conversion in additively manufactured medical skull models.

MATERIAL AND METHODS

Three different institutes were requested to perform an automatic reconstruction from an identical DICOM data set of a patients undergoing tumour surgery into an STL file format using their software of preference. The acquired digitized STL data sets were assessed and compared and subsequently used to fabricate physical medical skull models. The three fabricated skull models were then scanned, and differences in the model geometries were assessed using established CAD inspection software methods.

RESULTS

A large variation was noted in size and anatomical geometries of the three physical skull models fabricated from an identical (or "a single") DICOM data set.

CONCLUSIONS

A medical skull model of the same individual can vary markedly depending on the DICOM to STL conversion software and the technical parameters used. Clinicians should be aware of this inaccuracy in certain applications.

Bone Regeneration Based on Tissue Engineering Conceptions - A 21st Century Perspective

The role of Bone Tissue Engineering in the field of Regenerative Medicine has been the topic of substantial research over the past two decades. Technological advances have improved orthopaedic implants and surgical techniques for bone reconstruction. However, improvements in surgical techniques to reconstruct bone have been limited by the paucity of autologous materials available and donor site morbidity. Recent advances in the development of biomaterials have provided attractive alternatives to bone grafting expanding the surgical options for restoring the form and function of injured bone. Specifically, novel bioactive (second generation) biomaterials have been developed that are characterised by controlled action and reaction to the host tissue environment, whilst exhibiting controlled chemical breakdown and resorption with an ultimate replacement by regenerating tissue. Future generations of biomaterials (third generation) are designed to be not only osteoconductive but also osteoinductive, i.e. to stimulate regeneration of host tissues by combining tissue engineering and in situ tissue regeneration methods with a focus on novel applications. These techniques will lead to novel possibilities for tissue regeneration and repair. At present, tissue engineered constructs that may find future use as bone grafts for complex skeletal defects, whether from post-traumatic, degenerative, neoplastic or congenital/developmental "origin" require osseous reconstruction to ensure structural and functional integrity. Engineering functional bone using combinations of cells, scaffolds and bioactive factors is a promising strategy and a particular feature for future development in the area of hybrid materials which are able to exhibit suitable biomimetic and mechanical properties. This review will discuss the state of the art in this field and what we can expect from future generations of bone regeneration concepts.

Diagnosis and Treatment Planning using Rapid Prototyping Technology in Surgical Endodontics

Medical imaging technologies involve from X-rays to more advanced imaging modalities like computerized tomography (CT) and magnetic resonance imaging (MRI). These new technologies are able to provide detailed three-dimensional (3D) pictures of areas of interest and therefore valuable data for diagnosis and therapeutic management. The construction of a physical model using this data provides numerous advantages like better visualization of complex anatomic areas, pretreatment surgical practice and enhanced communication and patient education. The following paper describes a case report of a large periapical lesion involving upper anterior teeth requiring periapical surgery. The use of rapid prototyping technology aided in the accurate diagnosis and the precise measurements of the size and location of the lesion and its subsequent management.

How to cite this article

Ramachandran A, Khan SIR. Diagnosis and Treatment Planning using Rapid Prototyping Technology in Surgical Endodontics. J Contemp Dent 2013;3(3):147-150.