Three-dimensional (3D) printing has numerous applications and has gained much interest in the medical world. The constantly improving quality of 3D-printing applications has contributed to their increased use on patients. This paper summarizes the literature on surgical 3D-printing applications used on patients, with a focus on reported clinical and economic outcomes. Three major literature databases were screened for case series (more than three cases described in the same study) and trials of surgical applications of 3D printing in humans. 227 surgical papers were analyzed and summarized using an evidence table. The papers described the use of 3D printing for surgical guides, anatomical models, and custom implants. 3D printing is used in multiple surgical domains, such as orthopedics, maxillofacial surgery, cranial surgery, and spinal surgery. In general, the advantages of 3D-printed parts are said to include reduced surgical time, improved medical outcome, and decreased radiation exposure. The costs of printing and additional scans generally increase the overall cost of the procedure. 3D printing is well integrated in surgical practice and research. Applications vary from anatomical models mainly intended for surgical planning to surgical guides and implants. Our research suggests that there are several advantages to 3D-printed applications, but that further research is needed to determine whether the increased intervention costs can be balanced with the observable advantages of this new technology. There is a need for a formal cost–effectiveness analysis.

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3D-printing techniques in a medical setting: a systematic literature review

Custom implants for the reconstruction of craniofacial defects have gained importance due to better performance over their generic counterparts. This is due to the precise adaptation to the region of implantation, reduced surgical times and better cosmesis. Application of 3D modeling in craniofacial surgery is changing the way surgeons are planning surgeries and graphic designers are designing custom implants. Advances in manufacturing processes and ushering of additive manufacturing for direct production of implants has eliminated the constraints of shape, size and internal structure and mechanical properties making it possible for the fabrication of implants that conform to the physical and mechanical requirements of the region of implantation. This article will review recent trends in 3D modeling and custom implants in craniofacial reconstruction.

3D modeling, custom implants and its future perspectives in craniofacial surgery.

The mechanical properties of the skin are important for various applications. Numerous tests have been conducted to characterize the mechanical behavior of this tissue, and this article presents a review on different experimental methods used. A discussion on the general mechanical behavior of the skin, including nonlinearity, viscoelasticity, anisotropy, loading history dependency, failure properties, and aging effects, is presented. Finally, commonly used constitutive models for simulating the mechanical response of skin are discussed in the context of representing the empirically observed behavior.

Skin mechanical properties and modeling: A review.

Aim
To assess the accuracy of static computer-guided implant placement.

Material and methods
Electronic and manual literature searches were conducted to collect information on the accuracy of static computer-guided implant placement and meta-regression analyses were performed to summarize and analyse the overall accuracy. The latter included a search for correlations between factors such as: support (teeth/mucosa/bone), number of templates, use of fixation pins, jaw, template production, guiding system, guided implant placement.

Results
Nineteen accuracy studies met the inclusion criteria. Meta analysis revealed a mean error of 0.99 mm (ranging from 0 to 6.5 mm) at the entry point and of 1.24 mm (ranging from 0 to 6.9 mm) at the apex. The mean angular deviation was 3.81° (ranging from 0 to 24.9°). Significant differences for all deviation parameters was found for implant-guided placement compared to placement without guidance. Number of templates used was significant, influencing the apical and angular deviation in favour for the single template. Study design and jaw location had no significant effect. Less deviation was found when more fixation pins were used (significant for entry).

Conclusion
Computer-guided implant placement can be accurate, but significant deviations have to be taken into account. Randomized studies are needed to analyse the impact of individual parameters in order to allow optimization of this technique. Moreover, a clear overview on indications and benefits would help the clinicians to find the right candidates.

Accuracy of computer‐aided implant placement

Development of a surgical navigation system based on augmented reality using an optical see-through head-mounted display

Development and validation of a surgical training simulator with haptic feedback for learning bone-sawing skill

An In Vivo Experimental Validation of a Computational Model of Human Foot

Reverse engineering in CAD model reconstruction of customized artificial joint

Purpose: In the field of oral implantology, there is a trend toward computer-aided implant surgery, especially the application of computerized tomography (CT)-derived surgical templates. However, because of relatively unsatisfactory match between the templates and receptor sites, conventional surgical templates may not be accurate enough for the severely resorbed edentulous cases during the procedure of transferring the preoperative plan to the actual surgery. The purpose of this study is to introduce a novel bone–tooth-combined-supported surgical guide, which is designed by utilizing a special modular software and fabricated via stereolithography technique using both laser scanning and CT imaging, thus improving the fit accuracy and reliability.



Materials and Methods: A modular preoperative planning software was developed for computer-aided oral implantology. With the introduction of dynamic link libraries and some well-known free, open-source software libraries such as Visualization Toolkit (Kitware, Inc., New York, USA) and Insight Toolkit (Kitware, Inc.) a plug-in evolutive software architecture was established, allowing for expandability, accessibility, and maintainability in our system. To provide a link between the preoperative plan and the actual surgery, a novel bone–tooth-combined-supported surgical template was fabricated, utilizing laser scanning, image registration, and rapid prototyping. Clinical studies were conducted on four partially edentulous cases to make a comparison with the conventional bone-supported templates.



Results: The fixation was more stable than tooth-supported templates because laser scanning technology obtained detailed dentition information, which brought about the unique topography between the match surface of the templates and the adjacent teeth. The average distance deviations at the coronal and apical point of the implant were 0.66 mm (range: 0.3–1.2) and 0.86 mm (range: 0.4–1.2), and the average angle deviation was 1.84° (range: 0.6–2.8°).



Conclusions: This pilot study proves that the novel combined-supported templates are superior to the conventional ones. However, more clinical cases will be conducted to demonstrate their feasibility and reliability.

Modular Preoperative Planning Software for Computer‐Aided Oral Implantology and the Application of a Novel Stereolithographic Template: A Pilot Study

Background

VR-based surgery simulation provides a cost-effective and efficient method to train novices. In this study, a virtual training system for maxillofacial surgery (VR-MFS), which aims mainly at the simulation of operations on mandible and maxilla, was developed and demonstrated.



Methods

The virtual models of the anatomic structures were reconstructed from CT data, and the virtual instruments were built from laser scanning data using reverse engineering technology. For collision detection, axis aligned bounding boxes (AABBs) were constructed for the anatomic models. Then, the simulation algorithms were developed, and the haptic force feedback was consequently calculated based on regression equations. Finally, the vivid 3D stereo effect was implemented with the use of an immersive workbench.



Results

A virtual training system for maxillofacial surgery was developed; in particular, the application for Le-Fort I osteotomy was implemented. The tactile, visual and aural effects were highly integrated, making the virtual surgical environment vivid and realistic.



Conclusions

The VR-MFS provides an effective approach in terms of helping novices to become familiar with maxillofacial surgery procedures. The same method can also be applied to other bone simulations. Copyright © 2013 John Wiley & Sons, Ltd.

Chengtao Wang

Papers

Development and validation of a surgical training simulator with haptic feedback for learning bone-sawing skill

An In Vivo Experimental Validation of a Computational Model of Human Foot

Reverse engineering in CAD model reconstruction of customized artificial joint

Modular Preoperative Planning Software for Computer‐Aided Oral Implantology and the Application of a Novel Stereolithographic Template: A Pilot Study

A virtual training system for maxillofacial surgery using advanced haptic feedback and immersive workbench