Modern concepts in computer-assisted craniomaxillofacial reconstruction:

Resin adjustment of three-dimensional printed thermoset occlusal splints: Bonding properties - Short communication

OBJECTIVES

To evaluate the interfacial adhesion of an autopolymerizing acrylic resin to 3D printed thermoset occlusal splints compared to thermoplastic occlusal splints.

MATERIALS AND METHODS

Cylinders made of an autopolymerizing acrylic resin were adhered to 3D printed thermoset and also to thermoplastic plates. A different surface treatment and three storage conditions were used: dry, 7 days water-storage and 14 days water-storage. Bond strength test (so-called shear-bond strength test) was afterward performed.

RESULTS

ANOVA (R2 = 0.764) revealed significant differences in bond strength according to material (p < 0.001) and storage (p < 0.001) but not for surface treatment (p = 0.202).

CONCLUSIONS

The bond strength of autopolymerizing acrylic resin to 3D printed thermoset plates is higher when compared to thermoplastic plates. Bonding between acrylic resin and 3D printed splints was high enough for clinical applications.conclusion CLINICAL RELEVANCE: The bond strength values obtained in this study with 3D printed plates were at the level of generally accepted adequate bonding values for prosthetic materials.

Virtual Planning of a Complex Three-Part Bimaxillary Osteotomy

In maxillofacial surgery, every patient presents special problems requiring careful evaluation. Conventional methods to study the deformities are still reliable, but the advent of tridimensional (3D) imaging, especially computed tomography (CT) scan and laser scanning of casts, created the opportunity to better understanding the skeletal support and the soft tissue structures. Nowadays, virtual technologies are increasingly employed in maxillofacial surgery and demonstrated precision and reliability. However, in complex surgical procedures, these new technologies are still controversial. Especially in the less frequent cases of three-part maxillary surgery, the experience is limited, and scientific literature cannot give a clear support. This paper presents the case of a young patient affected by a complex long face dentofacial deformity treated by a bimaxillary surgery with three-part segmentation of the maxilla. The operator performed the surgical study completely with a virtual workflow. Pre- and postoperative CT scan and optical scanning of plaster models were collected and compared. Every postoperatory maxillary piece was superimposed with the presurgical one, and the differences were examined in a color-coded map. Only mild differences were found near the osteotomy lines, when the bony surface and the teeth demonstrated an excellent coincidence.

Development and refinement of computer-assisted planning and execution system for use in face-jaw-teeth transplantation to improve skeletal and dento-occlusal outcomes

PURPOSE OF REVIEW

To describe the development and refinement of the computer-assisted planning and execution (CAPE) system for use in face-jaw-teeth transplants (FJTTs).

RECENT FINDINGS

Although successful, some maxillofacial transplants result in suboptimal hybrid occlusion and may require subsequent surgical orthognathic revisions. Unfortunately, the use of traditional dental casts and splints pose several compromising shortcomings in the context of FJTT and hybrid occlusion. Computer-assisted surgery may overcome these challenges. Therefore, the use of computer-assisted orthognathic techniques and functional planning may prevent the need for such revisions and improve facial-skeletal outcomes.

SUMMARY

A comprehensive CAPE system for use in FJTT was developed through a multicenter collaboration and refined using plastic models, live miniature swine surgery, and human cadaver models. The system marries preoperative surgical planning and intraoperative execution by allowing on-table navigation of the donor fragment relative to recipient cranium, and real-time reporting of patient's cephalometric measurements relative to a desired dental-skeletal outcome. FJTTs using live-animal and cadaveric models demonstrate the CAPE system to be accurate in navigation and beneficial in improving hybrid occlusion and other craniofacial outcomes. Future refinement of the CAPE system includes integration of more commonly performed orthognathic/maxillofacial procedures.

Application of biodegradable 3D-printed cage for cervical diseases via anterior cervical discectomy and fusion (ACDF): an in vitro biomechanical study

OBJECTIVES

To design and fabricate a 3D-printed cervical cage composite of polylactic acid (PLA)/nano-sized and β-tricalcium phosphate (β-TCP).

RESULTS

CAD analysis provided a useful platform to design the preliminary cage. In vitro cell culture and in vivo animal results showed promising results in the biocompatibility of the constructs. Endplate matching evaluation showed better matching degree of 3D-printed cages than those of conventional cages. Biomechanical evaluation showed better mechanical properties of 3D-printed cages than those of conventional cages.

CONCLUSION

The novel 3D printed PLA/pβ-TCP cage showed good application potential, indicating a novel, feasible, and inexpensive method to manufacture cervical fusion cages.

[12 years of Computer-Aided Surgery around the Head : Developments in surgical planning and simulation from a Bern perspective]

Over the past years, the multidisciplinary character of the international Computer-Aided Surgery around the Head (CAS-H) symposium has advanced many medical technologies, which were often adopted by industry. In Bern, the synergetic effects of the CAS-H symposium have enabled many experiences and developments in the area of computer-aided surgery. Planning and simulation methods in the areas of craniomaxillofacial surgery and otorhinolaryngology were developed and tested in clinical settings. In the future, further CAS-H symposia should follow, in order to promote the possibilities and applications of computer-assisted surgery around the head.

Contemporary Correction of Dentofacial Anomalies: A Clinical Assessment

Contemporary computer-assisted technologies can support the surgical team in the treatment of patients affected by dentofacial deformities. Based on own experiences of 350 patients that received orthognathic surgery by the same team from 2007 to 2015, this clinical review is intended to give an overview of the results and risks related to the surgical correction of dentofacial anomalies. Different clinical and technological innovations that can contribute to improve the planning and transfer of corrective dentofacial surgery are discussed as well. However, despite the presence of modern technologies, a patient-specific approach and solid craftsmanship remain the key factors in this elective surgery.

Magnetic resonance imaging of intraoral hard and soft tissues using an intraoral coil and FLASH sequences

Objectives

To ascertain the feasibility of MRI as a non-ionizing protocol for routine dentomaxillofacial diagnostic imaging. Wireless coils were used for MRI of intraoral hard and soft tissues.

Methods

FLASH MRI was applied in vivo with a mandible voxel size of 250 × 250 × 500 μm³, FOV of 64 × 64 × 28 mm³ and acquisition time of 3:57 min and with a maxilla voxel size of 350 μm³ and FOV of 34 cm³ in 6:40 min. Ex vivo imaging was performed in 4:38 min, with a resolution of 200 μm³ and FOV of 36.5 cm³. Cone beam (CB) CT of the mandible and subjects were acquired. MRI was compared to CBCT and histological sections. Deviations were calculated with intraclass correlation coefficient (ICC) and coefficient of variation (c_v).

Results

A high congruence between CBCT, MRI and specimens was demonstrated. Hard and soft tissues including dental pulp, periodontium, gingiva, cancellous bone and mandibular canal contents were adequately displayed with MRI.

Conclusions

Imaging of select intraoral tissues was achieved using custom MRI protocols with an easily applicable intraoral coil in a clinically acceptable acquisition time. Comparison with CBCT and histological sections helped demonstrate dimensional accuracy of the MR images. The course of the mandibular canal was accurately displayed with CBCT and MRI.

Key points

• MRI is a clinically available diagnostic tool in dentistry

• Intraoral hard and soft tissues can be imaged with a high resolution with MRI

• The dimensional accuracy of MRI is comparable to cone beam CT

Electronic supplementary material

The online version of this article (doi:10.1007/s00330-016-4254-1) contains supplementary material, which is available to authorized users.

Three-dimensional planning in craniomaxillofacial surgery

Introduction:

Three-dimensional (3D) planning in oral and maxillofacial surgery has become a standard in the planification of a variety of conditions such as dental implants and orthognathic surgery. By using custom-made cutting and positioning guides, the virtual surgery is exported to the operating room, increasing precision and improving results.

Materials and Methods:

We present our experience in the treatment of craniofacial deformities with 3D planning. Software to plan the different procedures has been selected for each case, depending on the procedure (Nobel Clinician, Kodak 3DS, Simplant O&O, Dolphin 3D, Timeus, Mimics and 3-Matic). The treatment protocol is exposed step by step from virtual planning, design, and printing of the cutting and positioning guides to patients’ outcomes.

Conclusions:

3D planning reduces the surgical time and allows predicting possible difficulties and complications. On the other hand, it increases preoperative planning time and needs a learning curve. The only drawback is the cost of the procedure. At present, the additional preoperative work can be justified because of surgical time reduction and more predictable results. In the future, the cost and time investment will be reduced. 3D planning is here to stay. It is already a fact in craniofacial surgery and the investment is completely justified by the risk reduction and precise results.

Image-guided bone resection as a prospective alternative to cutting templates—A preliminary study

OBJECTIVE

To evaluate the accuracy of craniomaxillofacial resections performed with an image-guided surgical sagittal saw.

MATERIAL AND METHODS

Twenty-four craniomaxillofacial resections were performed using an image-guided sagittal saw. Surgical outcomes were compared with a preoperative virtual plan in terms of the resected bone volume, control point position and osteotomy trajectory angle. Each measurement was performed twice by two independent observers.

RESULTS

The best convergence between the planned and actual bone resection was observed for the orbital region (6.33 ± 4.04%). The smallest mean difference between the preoperative and postoperative control point positions (2.00 ± 0.66 mm) and the lowest mean angular deviation between the virtual and actual osteotomy (5.49 ± 3.17 degrees) were documented for the maxillary region. When all the performed procedures were analyzed together, mean difference between the planned and actual bone resection volumes was 9.48 ± 4.91%, mean difference between the preoperative and postoperative control point positions amounted to 2.59 ± 1.41 mm, and mean angular deviation between the planned and actual osteotomy trajectory equaled 8.21 ± 5.69 degrees.

CONCLUSION

The results of this study are encouraging but not fully satisfactory. If further improved, the hereby presented navigation technique may become a valuable supporting method for craniomaxillofacial resections.

Accuracy of fibular sectioning and insertion into a rapid-prototyped bone plate, for mandibular reconstruction using CAD-CAM technology

Modern techniques of mandibular reconstruction, such as CAD-CAM technology and rapid prototyping, offer new means by which reconstructive surgery can be planned to optimise aesthetic outcomes and prosthetic rehabilitation. The high degree of accuracy afforded by these approaches is principally attributable to high-precision fibular sectioning and insertion of the bone into a customised bone plate. CAD-CAM mandibular reconstruction procedures using vascularised bone free-flap transfers were performed on 10 patients with benign or malignant neoplasms. Five were not treated with the aid of CAD-CAM technology, and served as the control group. Five were scheduled for maxillofacial surgery using surgical cutting guides and customised bone plates. A generalised linear model for linear measures was used to compare the accuracy of reconstruction between the two groups. A difference, even though not significant, in the lateral shift of the mesial and distal positions of the fibular units was evident between groups. CAD-CAM-generated fibular surgical guides afford improved accuracy when used to restore native anatomy, especially in the context of mandibular arch restoration, and both operating room time and related costs are reduced during fibular sectioning.

Precise positioning of an intraoral distractor using augmented reality in patients with hemifacial microsomia

BACKGROUND

Through three-dimensional real time imaging, augmented reality (AR) can provide an overlay of the anatomical structure, or visual cues for specific landmarks. In this study, an AR Toolkit was used for distraction osteogenesis with hemifacial microsomia to define the mandibular osteotomy line and assist with intraoral distractor placement.

METHODS

20 patients with hemifacial microsomia were studied and were randomly assigned to experimental and control groups. Pre-operative computed tomography was used in both groups, whereas AR was used in the experimental group. Afterwards, pre- and post-operative computed tomographic scans of both groups were superimposed, and several measurements were made and analysed.

RESULTS

Both the conventional method and AR technique achieved proper positioning of the osteotomy planes, although the AR was more accurate. The difference in average vertical distance from the coronoid and condyle process to the pre- and post-operative cutting planes was significant (p < 0.01) between the two groups, whereas no significant difference (p > 0.05) was observed in the average angle between the two planes. The difference in deviations between the intersection points of the overlaid mandible across two cutting planes was also significant (p < 0.01).

CONCLUSION

This study reports on an efficient approach for guiding intraoperative distraction osteogenesis. Augmented reality tools such as the AR Toolkit may be helpful for precise positioning of intraoral distractors in patients with hemifacial microsomia in craniofacial surgery.

RapidSplint: virtual splint generation for orthognathic surgery - results of a pilot series

Background

Within the domain of craniomaxillofacial surgery, orthognathic surgery is a special field dedicated to the correction of dentofacial anomalies resulting from skeletal malocclusion. Generally, in such cases, an interdisciplinary orthodontic and surgical treatment approach is required. After initial orthodontic alignment of the dental arches, skeletal discrepancies of the jaws can be corrected by distinct surgical strategies and procedures in order to achieve correct occlusal relations, as well as facial balance and harmony within individualized treatment concepts. To transfer the preoperative surgical planning and reposition the mobilized dental arches with optimal occlusal relations, surgical splints are typically used. For this purpose, different strategies have been described which use one or more splints. Traditionally, these splints are manufactured by a dental technician based on patient-specific dental casts; however, computer-assisted technologies have gained increasing importance with respect to preoperative planning and its subsequent surgical transfer.

Methods

: In a pilot study of 10 patients undergoing orthognathic corrections by a one-splint strategy, two final occlusal splints were produced for each patient and compared with respect to their clinical usability. One splint was manufactured in the traditional way by a dental technician according to the preoperative surgical planning. After performing a CBCT scan of the patient’s dental casts, a second splint was designed virtually by an engineer and surgeon working together, according to the desired final occlusion. For this purpose, RapidSplint®, a custom-made software platform, was used. After post-processing and conversion of the datasets into .stl files, the splints were fabricated by the PolyJet procedure using photo polymerization. During surgery, both splints were inserted after mobilization of the dental arches then compared with respect to their clinical usability according to the occlusal fitting.

Results

Using the workflow described above, virtual splints could be designed and manufactured for all patients in this pilot study. Eight of 10 virtual splints could be used clinically to achieve and maintain final occlusion after orthognathic surgery. In two cases virtual splints were not usable due to insufficient occlusal fitting, and even two of the traditional splints were not clinically usable. In five patients where both types of splints were available, their occlusal fitting was assessed as being equivalent, and in one case the virtual splint showed even better occlusal fitting than the traditional splint. In one case where no traditional splint was available, the virtual splint proved to be helpful in achieving the final occlusion.

Conclusions

In this pilot study it was demonstrated that clinically usable splints for orthognathic surgery can be produced by computer-assisted technology. Virtual splint design was realized by RapidSplint®, an in-house software platform which might contribute in future to shorten preoperative workflows for the production of orthognathic surgical splints.

Cingi Steps for preoperative computer-assisted image editing before reduction rhinoplasty

BACKGROUND

The aim of this work is to provide a stepwise systematic guide for a preoperative photo-editing procedure for rhinoplasty cases involving the cooperation of a graphic artist and a surgeon.

METHODS

One hundred female subjects who planned to undergo a reduction rhinoplasty operation were included in this study. The Cingi Steps for Preoperative Computer Imaging (CS-PCI) program, a stepwise systematic guide for image editing using Adobe PhotoShop's "liquify" effect, was applied to the rhinoplasty candidates. The stages of CS-PCI are as follows: (1) lowering the hump; (2) shortening the nose; (3) adjusting the tip projection, (4) perfecting the nasal dorsum, (5) creating a supratip break, and (6) exaggerating the tip projection and/or dorsal slope.

RESULTS

Performing the Cingi Steps allows the patient to see what will happen during the operation and observe the final appearance of his or her nose. After the application of described steps, 71 patients (71%) accepted step 4, and 21 (21%) of them accepted step 5. Only 10 patients (10%) wanted to make additional changes to their operation plans.

CONCLUSION

The main benefits of using this method is that it decreases the time needed by the surgeon to perform a graphic analysis, and it reduces the time required for the patient to reach a decision about the procedure. It is an easy and reliable method that will provide improved physician-patient communication, increased patient confidence, and enhanced surgical planning while limiting the time needed for planning.

Virtual planning for craniomaxillofacial surgery--7 years of experience

Contemporary computer-assisted surgery systems more and more allow for virtual simulation of even complex surgical procedures with increasingly realistic predictions. Preoperative workflows are established and different commercially software solutions are available. Potential and feasibility of virtual craniomaxillofacial surgery as an additional planning tool was assessed retrospectively by comparing predictions and surgical results. Since 2006 virtual simulation has been performed in selected patient cases affected by complex craniomaxillofacial disorders (n = 8) in addition to standard surgical planning based on patient specific 3d-models. Virtual planning could be performed for all levels of the craniomaxillofacial framework within a reasonable preoperative workflow. Simulation of even complex skeletal displacements corresponded well with the real surgical result and soft tissue simulation proved to be helpful. In combination with classic 3d-models showing the underlying skeletal pathology virtual simulation improved planning and transfer of craniomaxillofacial corrections. Additional work and expenses may be justified by increased possibilities of visualisation, information, instruction and documentation in selected craniomaxillofacial procedures.

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.

Traditional and contemporary surgical approaches to the orbit

Traditional orbital approaches are nearly a century old and still comprise the foundation of techniques used today. Computer-assisted planning and intraoperative navigation have recently been reported with more prevalence in the literature. The purpose of this article was to review commonly used approaches to the orbit: old and new.

Latest trends in craniomaxillofacial surgical instrumentation

PURPOSE OF REVIEW

To review the past year's literature regarding recent innovations in surgical instrumentation for craniomaxillofacial surgery.

RECENT FINDINGS

Current advances in surgical instrumentation have led to many improvements in the field, allowing greater visualization and precision both before and during procedures. One of the common goals is to achieve excellent outcomes with minimal complications, while at the same time minimizing invasiveness of surgery. Highlighted innovations include greater capacities for acquisition of data, leading to improved imaging modalities and expansion of computer-assisted surgical techniques; continued developments in biomaterials used in various reconstructions; and novel uses of bone cutting and bone fixation instrumentation.

SUMMARY

Technology in the field of craniomaxillofacial surgery is developing rapidly, leading to novel instrumentation being utilized across a broad spectrum of areas. Published data have been encouraging to date, indicating an ever increasing adaptation of these innovations in clinical practice. Future efforts need to focus on cost-benefit analysis and constructing larger-scale studies to better understand effectiveness and patient outcomes.

Maxillary ridge augmentation with custom-made CAD/CAM scaffolds. A 1-year prospective study on 10 patients

Several procedures have been proposed to achieve maxillary ridge augmentation. These require bone replacement materials to be manually cut, shaped, and formed at the time of implantation, resulting in an expensive and time-consuming process. In the present study, we describe a technique for the design and fabrication of custom-made scaffolds for maxillary ridge augmentation, using three-dimensional computerized tomography (3D CT) and computer-aided design/computer-aided manufacturing (CAD/CAM). CT images of the atrophic maxillary ridge of 10 patients were acquired and modified into 3D reconstruction models. These models were transferred as stereolithographic files to a CAD program, where a virtual 3D reconstruction of the alveolar ridge was generated, producing anatomically shaped, custom-made scaffolds. CAM software generated a set of tool-paths for manufacture by a computer-numerical-control milling machine into the exact shape of the reconstruction, starting from porous hydroxyapatite blocks. The custom-made scaffolds were of satisfactory size, shape, and appearance; they matched the defect area, suited the surgeon's requirements, and were easily implanted during surgery. This helped reduce the time for surgery and contributed to the good healing of the defects.