Patient-specific polyetheretherketone facial implants in a computer-aided planning workflow.

PURPOSE: In the present study, we report an innovative workflow using polyetheretherketone (PEEK) patient-specific implants for esthetic corrections in the facial region through onlay grafting. The planning includes implant design according to virtual osteotomy and generation of a subtraction volume. The implant design was refined by stepwise changing the implant geometry according to soft tissue simulations. MATERIALS AND METHODS: One patient was scanned using computed tomography. PEEK implants were interactively designed and manufactured using rapid prototyping techniques. Positioning intraoperatively was assisted by computer-aided navigation. Two months after surgery, a 3-dimensional surface model of the patient's face was generated using photogrammetry. Finally, the Hausdorff distance calculation was used to quantify the overall error, encompassing the failures in soft tissue simulation and implantation. RESULTS: The implant positioning process during surgery was satisfactory. The simulated soft tissue surface and the photogrammetry scan of the patient showed a high correspondence, especially where the skin covered the implants. The mean total error (Hausdorff distance) was 0.81 ± 1.00 mm (median 0.48, interquartile range 1.11). The spatial deviation remained less than 0.7 mm for the vast majority of points. CONCLUSIONS: The proposed workflow provides a complete computer-aided design, computer-aided manufacturing, and computer-aided surgery chain for implant design, allowing for soft tissue simulation, fabrication of patient-specific implants, and image-guided surgery to position the implants. Much of the surgical complexity resulting from osteotomies of the zygoma, chin, or mandibular angle might be transferred into the planning phase of patient-specific implants.

Splint sterilization--a potential registration hazard in computer-assisted surgery.

PURPOSE: Registration of preoperative targeting information for the intraoperative situation is a crucial step in computer-assisted surgical interventions. Point-to-point registration using acrylic splints is among the most frequently used procedures. There are, however, no generally accepted recommendations for sterilization of the splint. An appropriate method for the thermolabile splint would be hydrogen peroxide-based plasma sterilization. This study evaluated the potential deformation of the splint undergoing such sterilization. Deformation was quantified using image-processing methods applied to computed tomographic (CT) volumes before and after sterilization. MATERIALS AND METHODS: An acrylic navigation splint was used as the study object. Eight metallic markers placed in the splint were used for registration. Six steel spheres in the mouthpiece were used as targets. Two CT volumes of the splint were acquired before and after 5 sterilization cycles using a hydrogen peroxide sterilizer. Point-to-point registration was applied, and fiducial and target registration errors were computed. Surfaces were extracted from CT scans and Hausdorff distances were derived. Effectiveness of sterilization was determined using Geobacillus stearothermophilus. RESULTS: Fiducial-based registration of CT scans before and after sterilization resulted in a mean fiducial registration error of 0.74 mm; the target registration error in the mouthpiece was 0.15 mm. The Hausdorff distance, describing the maximal deformation of the splint, was 2.51 mm. Ninety percent of point-surface distances were shorter than 0.61 mm, and 95% were shorter than 0.73 mm. No bacterial growth was found after the sterilization process. CONCLUSION: Hydrogen peroxide-based low-temperature plasma sterilization does not deform the splint, which is the base for correct computer-navigated surgery.

The Anatomy Course During COVID-19: The Impact of Cadaver-Based Learning on the Initiation of Reflection on Death.

Background: During the COVID-19 pandemic, in-person cadaveric dissection laboratories for teaching anatomy were omitted by many schools around the world. While knowledge domains can be easily evaluated via remote exams, non-traditional discipline-independent skills such as those encouraged through reflection on the topic of death are often overlooked. This study investigated how different anatomy course formats played a role in initiating students' reflections on death during the COVID-19 pandemic. Method: In fall 2020, 217 medical, dental, premedical, and health sciences students from 13 international universities discussed differences in their anatomy courses online. Formats of anatomy courses ranged from dissection-based, prosection-based, hybrid (combination of dissection and prosection) to no laboratory exposure at all. Students' responses to the question, "Did/does your anatomy course initiate your thinking about life's passing?" were collected, and they self-reported themes that were present in their reflections on death using a multiple-choice prompt. Statistical analyses to detect differences between students with and without exposure to cadavers were performed using the chi-squared test. Results: When comparing students who had exposure to human anatomical specimens to those who had no exposure, the majority of students with exposure thought that the course did initiate thoughts about life's passing, compared to students without exposure (P < 0.05). Reflection themes were consistent across groups. Discussion: These findings indicate that anatomy dissection courses are important for the initiation of students' feelings about the topic of death. Omission of cadaveric dissection- or prosection-based laboratories will decrease the likelihood that students initiate reflection on this topic and gain important transferable skills.

Initiating Students' Reflections on Life's Passing in the Anatomy Course - an International Observation at 14 Universities.

BACKGROUND: Medical and dental students' feelings and thoughts about the topic of death and life's passing are often associated with learning in the gross anatomy course, when students begin working with a deceased body donor in order to study human anatomy. Little is known of whether the format of anatomy teaching has an impact on these experiences. An observational study was performed to capture the initiation of students' sentiments on the topic of life's passing during the anatomy course at 14 international universities, identify common themes regarding these thoughts, and to study the connection to variations in anatomy course formats and included elements. METHOD: Preclinical anatomy students reflected on one question (i.e., "How did your experience in the anatomy laboratory bring about your reflections on the meaning of life and human existence as well as the sanctity of one's passing?"). Written assignments were collected and anonymously coded. Information on anatomy courses was obtained via faculty questionnaires. RESULT: A variety of themes were identified at the different schools, correlated with different anatomy formats and elements. Results indicate that the courses that offer hands-on cadaveric dissections may play an important role in triggering these sentiments. DISCUSSION: The initiation of students' sentiments about the topic of death varies and includes several themes. There can be a connection to the way anatomy is taught, particularly if hands-on comprehensive cadaveric dissection or prosections are included. CONCLUSION: In summary, anatomy courses can initiate students' thinking about life's passing - particularly in schools that offer hands-on cadaveric dissections or prosections.

An International Partnership of 12 Anatomy Departments - Improving Global Health through Internationalization of Medical Education.

Background: At a time of global interconnectedness, the internationalization of medical education has become important. Anatomy as an academic discipline, with its close connections to the basic sciences and to medical education, can easily be connected with global health and internationalization of medical education. Here the authors present an international program based on a partnership between twelve anatomy departments in ten countries, on four continents. Details of a proposed plan for the future direction of the program are also discussed. Objective: The aim is to improve global healthcare by preparing future global healthcare leaders via early international networking, international collaboration and exchange, intercultural experience, and connecting two seemingly distant academic disciplines - anatomy and global health - via internationalization of medical education. Methods: Based in the anatomy course, the program involved early international collaboration between preclinical medical and dental students. The program provided a stepwise progression for learning about healthcare and intercultural topics beyond pure anatomy education - starting with virtual small groups of international students, who subsequently presented their work to a larger international audience during group videoconferences. The above progressed to in-person visits for research internships in the basic sciences within industrialized countries. Findings: Students appreciated the international and intercultural interaction, learned about areas outside the scope of anatomy (e.g., differences in healthcare education and delivery systems, Public and Global Health challenges, health ethics, and cultural enrichment), and valued the exchange travel for basic sciences research internships and cultural experience. Conclusions: This unique collaboration of international anatomy departments can represent a new role for the medical anatomy course beyond pure anatomy teaching - involving areas of global health and internationalization of medical education - and could mark a new era of international collaboration among anatomists.

Effectiveness of Two Different Lingual Flap Advancing Techniques for Vertical Bone Augmentation in the Posterior Mandible: A Comparative, Split-Mouth Cadaver Study.

Vertical ridge augmentation in the posterior mandible is a technique-sensitive procedure that requires adequate anatomical knowledge and precise surgical skills to minimize the risk of complications. One of the most important but also challenging aspects of the surgical technique is proper flap management to allow for passive flap closure and reduce the chances of postoperative complications affecting deep anatomical spaces. This article presents a detailed description of a novel lingual flap advancement technique and its validation via a split-mouth, comparative study using a cadaver model. A total of 12 fresh cadaver heads presenting bilateral posterior mandibular edentulism were selected. Sides were randomized to receive a classic lingual flap release technique (control) or the modified technique presented here, which involves the intentional preservation of the mylohyoid muscle attachment to the mandible. Vertical flap release was measured at three different zones using standard forces. The mean difference between the test and control group in zones I (retromolar pad area), II (middle area), and III (premolar area) was 8.273 ± 1.794 mm (standard error of the mean [SEM] = 0.5409 mm), 10.09 ± 2.948 mm (SEM = 0.8889 mm), and 10.273 ± 2.936 mm (SEM = 0.8851 mm), respectively, reaching very strong statistical significance (P < .0001) in all three zones.

Evaluation of an experimental oblique plate for osteosynthesis of mandibular condyle fractures.

OBJECTIVE: The aim of this study was to test the bone thickness and potential screw length for osteosynthesis of condylar base fractures (according to the Loukota classification) with an experimental titanium plate, placed in an ideal position against 2 types of conventional plates. STUDY DESIGN: After exclusion of completely edentulous mandibles, 28 dentate macerated mandibles available at the time of the study were included. Linear regression models 1 and 2 compared the sums of the 2 cranial bone thicknesses and the 3 caudal thicknesses among the 3 different plate designs, and linear models 3 and 4 tested the bone thickness in the 2 most cranial screw axes. RESULTS: Linear models 1 and 2 revealed significantly higher potential screw lengths for the experimental oblique plate. Equally, linear models 3 and 4 indicated significantly higher bone thickness for the novel oblique plate. CONCLUSION: The novel proposed oblique plate allows for favorable plate positioning in a biomechanically ideal location with sufficient amounts of local bone for stable plate fixation. When plates with 15-degree angulated screw holes are used, stable bicortical plate fixation can be achieved.

Morphometric analysis of sinus depth in the posterior maxilla and proposal of a novel classification.

The aim of this study was to analyse the posterior maxillary sinus based on its extension into the alveolar process and to provide a simple clinical classification. A retrospective cohort study was conducted in CT scans of 200 dentate and 200 edentulous patients (100 women and 100 men, respectively). After manual placement of 12 reference points morphometric analysis was performed and sinus depth, residual alveolar ridge height (RH) and the sinus opening angle were calculated. Sinuses were classified according to the quartiles of sinus depth: class I (above the hard palate), class II (0-6 mm below the hard palate) and class III (>6 mm below the hard palate). Sinus depth was found to be a reliable anatomical landmark and did not vary significantly between gender (p = 0.8940) or dentition groups (p = 0.9723). Alveolar height varied significantly between sinus classes (p < 2 × 10-16) and dentition groups (p < 2 × 10-16) but not between genders (p = 0.5178). The sinus opening angle was significantly different between sinus classes (p < 2.2 × 10-16) but not between gender or dentition groups. We propose a novel classification built upon the quartiles of sinus depth, dividing the sinuses into three classes. Our classification is the first one that represents the anatomy of the patient independent of gender and dentition.

Split-thickness flap with a semicircular punched-ridge pedicled periosteal flap for implant restoration in highly atrophic patients: a technical note.

Attached gingiva is a crucial aspect of healthy peri-implant tissue. Severely atrophied jaws have minimal quantities of attached gingiva. Any surgical procedure bears the potential risk of further loss of attached gingiva. The split-thickness flap described here provides excellent access. Using a biopsy punch, the periosteum is easily cut in semicircular fashion on the labial surface of the bone so that it remains pedicled on the lingual or palatal ridge. The split-thickness flap permits fixation of the gingival flap to the periosteum. The periosteal flap is closed with sutures to achieve soft tissue closure over the implants even in case of simultaneous vestibuloplasty.

Evaluation of bone surface registration applying a micro-needle array.

AIM: In this study we present and evaluated a new registration technology for the jaw-bone surface. It is based on a micromechatronic device for the generation of a "mechanical image" of the bone surface by means of an array of micro-needles that are penetrating the soft tissue until they touch the surface of the bone. This "mechanical impression image" is aligned with the CT data set. MATERIAL AND METHODS: Based on laboratory measurements on 10 specially prepared jawbone models we evaluate the accuracy of this new registration method. RESULTS: Our measurements of the 10 specimens revealed a maximum overall location error of 0.97 mm (range: 0.35-0.97 mm). CONCLUSIONS: From the technical point of view the presented registration technology has the potential to improve the performance (i.e. accuracy and avoidance of errors) of the registration process for bony structures in selected applications of image-guided surgery.