Development and validation of a cadaveric porcine Pseudotumor model for Oral Cancer biopsy and resection training.

OBJECTIVE: The gold standard of oral cancer (OC) treatment is diagnostic confirmation by biopsy followed by surgical treatment. However, studies have shown that dentists have difficulty performing biopsies, dental students lack knowledge about OC, and surgeons do not always maintain a safe margin during tumor resection. To address this, biopsies and resections could be trained under realistic conditions outside the patient. The aim of this study was to develop and to validate a porcine pseudotumor model of the tongue. METHODS: An interdisciplinary team reflecting various specialties involved in the oncological treatment of head and neck oncology developed a porcine pseudotumor model of the tongue in which biopsies and resections can be practiced. The refined model was validated in a final trial of 10 participants who each resected four pseudotumors on a tongue, resulting in a total of 40 resected pseudotumors. The participants (7 residents and 3 specialists) had an experience in OC treatment ranging from 0.5 to 27 years. Resection margins (minimum and maximum) were assessed macroscopically and compared beside self-assessed margins and resection time between residents and specialists. Furthermore, the model was evaluated using Likert-type questions on haptic and radiological fidelity, its usefulness as a training model, as well as its imageability using CT and ultrasound. RESULTS: The model haptically resembles OC (3.0 ± 0.5; 4-point Likert scale), can be visualized with medical imaging and macroscopically evaluated immediately after resection providing feedback. Although, participants (3.2 ± 0.4) tended to agree that they had resected the pseudotumor with an ideal safety margin (10 mm), the mean minimum resection margin was insufficient at 4.2 ± 1.2 mm (mean ± SD), comparable to reported margins in literature. Simultaneously, a maximum resection margin of 18.4 ± 6.1 mm was measured, indicating partial over-resection. Although specialists were faster at resection (p < 0.001), this had no effect on margins (p = 0.114). Overall, the model was well received by the participants, and they could see it being implemented in training (3.7 ± 0.5). CONCLUSION: The model, which is cost-effective, cryopreservable, and provides a risk-free training environment, is ideal for training in OC biopsy and resection and could be incorporated into dental, medical, or oncologic surgery curricula. Future studies should evaluate the long-term training effects using this model and its potential impact on improving patient outcomes.

Stereotactic radiotherapy in the management of oligometastatic and recurrent head and neck cancer: a single-center experience.

INTRODUCTION: Oligometastatic disease (OMD) is a metastatic stage that could benefit maximally from local therapies. Patients in this state have a better prognosis relative to those with disseminated metastases. Stereotactic radiotherapy provides a non-invasive ablative tool for primary malignant tumors and metastases. MATERIALS AND METHODS: We searched our register for patients with oligometastatic or recurrent head and neck cancer (OMD/R-HNC) who received stereotactic radiotherapy to manage their OMD/R. We evaluated the survival outcomes and prognostic factors that affected the survival of those patients. RESULTS: In all, 31 patients with 48 lesions met the inclusion criteria for the analysis. The lesions comprised various metastatic sites, with the majority being pulmonary (37 lesions). Squamous cell cancer was the most common histology (26 patients). The median overall survival (mOS) was 33 months, with a progression-free survival (PFS) of 9.6 months. Eight patients received subsequent stereotactic radiotherapy after disease progression. The local control (LC) rates were 91.3, 87.7, and 83% at 6, 12, and 36 months. Patients with the de novo OMD who received stereotactic radiotherapy as their initial treatment had a median systemic treatment-free survival of 23.9 months. In univariate analysis, a trend for better OS was observed in patients with p16-positive squamous cell tumors; patients who progressed within 150 days after diagnosis had a significantly lower OS. De novo OMD showed significantly better PFS compared to induced OMD. Multivariate analyses identified p16-positive squamous cell cancer, metachronous OMD and a longer time to progression as positive predictors of OS, while de novo OMD was the only positive predictor for PFS. Treatment-related toxicities were generally mild, with two cases of grade 3 dysphagia reported. CONCLUSION: Stereotactic radiotherapy demonstrated favorable outcomes in patients with OMD/R-HNC with limited toxicities. Further studies are warranted to validate these findings and optimize treatment strategies for this patient population.

Clinical Outcomes of Low-level Laser Therapy in Management of Advanced Implant Surgery Complications: A Comparative Clinical Study.

INTRODUCTION: Nowadays, implant insertion is accompanied by undesired consequences. As surgery techniques become more and more complex, an increase of intra- and post-op complications can be expected. Application of low-level laser (LLL) is one of the conservative approaches to control the complications with any side effects and low treatment costs. The present study aimed to evaluate the effect of 650 nm LLL irradiation on the reduction of complications after advanced implant surgeries. MATERIALS AND METHODS: In this triple-blinded clinical trial, 30 patients aged between 25 to 65 years were in need of bone graft or sinus lift procedure for simultaneously implant insertion. In the LLL treatment group, the surgical site of each implant was treated with 650 nm laser. The same method and duration were applied in the placebo group. The pain levels, facial swelling, and wound healing were evaluated. RESULTS: This study indicated that pain levels were reduced in the laser group (p <0.05). Also, facial swelling in the 3rd and 7th day after the surgery relieved more in laser group. Furthermore, investigation of the surgical site showed a higher level of wound healing in the laser group (p <0.05). CONCLUSION: Regarding the biological effects of advanced implant surgeries and accompanying complications, adjuvant treatment with a laser could significantly improve wound healing and reduce the severity and duration of pain and swelling. CLINICAL SIGNIFICANCE: This clinical trial demonstrates reductions of the level of pain, facial swelling and improvements of wound healing are followed by the use of low-level laser therapy.

Can Use of Rigid Fixation After Consolidation Increase Stability in Cleft Patients Following Distraction Osteogenesis?

PURPOSE: The stability of distraction osteogenesis (DO) is an important issue in maxillary advancement for patients with cleft lip and palate (CLP). The aim of this study was to evaluate postoperative stability in patients with and without internal fixation after removing maxillary distraction devices. MATERIALS AND METHODS: This randomized clinical trial assessed patients with CLP who needed maxillary advancement greater than 6 mm; they were randomly assigned to 1 of 2 groups. In group 1, distraction devices were removed 3 months after distraction and then 4 L miniplates were placed bilaterally in the maxilla. In group 2 (controls), no miniplates were placed after removing the distraction devices. Lateral cephalograms taken on 3 occasions (preoperatively, immediately after removing the distraction device, and after 18 months) were used to determine vertical and horizontal changes at the A point. RESULTS: Twenty-two patients (n = 11 per group) were included. There was no significant difference between groups for horizontal relapse (P = .79). The results showed no significant difference for vertical relapse between the 2 groups (P = .11). The Pearson correlation test showed a correlation between the amount of advancement and horizontal relapse at the A point in group 1 (P = .01) and group 2 (P = .001). In group 1, for every 1-mm maxillary advancement, a 0.36-mm relapse was seen (B = 0.36, P = .01). In group 2, for every 1-mm maxillary advancement, a 0.43-mm relapse was seen (B = 0.43, P = .001). CONCLUSION: According to these results, rigid fixation after consolidation did not increase stability in patients with CLP after DO.

Functional donor site morbidity longer than one year after fibula free flap: A prospective biomechanical analysis.

OBJECTIVES: The fibula free flap is the workhorse procedure for osseous reconstruction. The objective of this study was to investigate long-term functional outcomes of the harvesting site. PATIENTS AND METHODS: About 19 patients (10 male, 9 female, mean age 58.1 years) were available for the long-term analysis 13-51 months after surgery. Jumping mechanography and balance testing on a ground force reaction plate (Leonardo Mechanograph GFRP) were performed before and surgery. The Esslinger Fitness Index (EFI, maximum peak power in W/kg normalized for age and gender) was considered as primary endpoint. Secondary outcomes were maximum force, range of motion in the ankle joint, sensory limitations, the American Orthopedic Foot and Ankle Society Score (AOFAS-Score), and subjective perceptions. RESULTS: We found no significant difference between pre- and postoperative EFI (70.4% versus 66.0%, P = 0.07) and body sway (1.72 cm2 versus 2.60 cm2 , P = 0.093). The AOFAS-Score was reduced by 8.8 points (99.1 points versus 90.3 points, P < 0.001). Dorsal extenstion (31.6° versus 24.1°, P < 0.001) and flexion (32.3 versus 25.6° flexion, P = 0.011) were significantly reduced and 6 patients had chronic pain. CONCLUSIONS: Reduced peak power and balance ability seem to be reversible short-term effects after fibula harvesting. We recommend preoperative patient education and standardized protocols for physiotherapy.

Surgically Assisted Rapid Palatomaxillary Expansion With or Without Pterygomaxillary Disjunction: A Systematic Review and Meta-Analysis.

PURPOSE: The purpose of this review was to evaluate the outcome measurements of anterior expansion, posterior expansion, and complications after surgically assisted rapid palatal expansion (SARPE) with or without pterygomaxillary disjunction (PMD). MATERIALS AND METHODS: A computerized database search was performed using PubMed, CINAHL, Cochrane, Scopus, and Web of Science. Then, a computerized search was conducted in Google Scholar and ProQuest to overcome publication bias. RESULTS: From the original 125 combined results, 3 met the inclusion criteria. The Quality Assessment Tool for Quantitative Studies of the Effective Public Health Practice Project assessed 2 articles as weak and 1 as moderate. The systematic review included a total of 48 patients (11 male and 37 female). For 25 patients, SARPE was performed with PMD and for 23 patients SARPE was performed without PMD. A tooth-borne fixed hyrax-type palatal expansion screw appliance was used for all cases, activated 1 to 2 mm intraoperatively, and, after a latency period of 3 to 7 days, activated 0.5 to 0.6 mm per day for 38 patients and 0.25 mm for the other 10 until adequate expansion. Postexpansion retention was performed using ligature wired hyrax in 18 patients for 4 months. Comparisons were based on cone-beam computed tomographic projections, study models only, or a combination of study models, anteroposterior cephalometric radiographs, and occlusal radiographs. The time to measure the changes ranged from before fixed orthodontic retention to 6 months after the completion of active expansion. A meta-analysis was possible only for anterior (intercanine) and posterior (inter-molar) dental expansions. CONCLUSION: The literature is inconclusive regarding the effect of PMD on the outcomes of SARPE. Further controlled trials are needed.

Immediate effects of different steps of rhinoplasty on nasolabial angle and tip projection.

Nasolabial angle (NLA) and nasal tip projection (NTP) play an important role in aesthetic nose surgery. Little deviations can determine success and failure. The goal of this study was to analyze the immediate effect of different steps of open rhinoplasty on NLA and NTP. In this prospective single-blind study, 50 consecutive rhinoplasty cases were considered. The study consisted of 38 women and 12 men. The mean age was 28 years, ranging from 17 to 37 years. A standard life-size photograph was taken in each step of a classic open rhinoplasty during surgery. Nasolabial angle and NTP were measured and analyzed. Nasolabial angle: average increase after skeletonization (2.26 degrees), strut insertion (4 degrees), and tip spanning (0.17 degrees), whereas cephalic resection caused a decrease (1.9 degrees). Nasal tip projection: average increase after skeletonization (0.1 mm), strut insertion (0.31 mm), and tip spanning (0.84 mm), whereas cephalic resection caused a decrease (0.53 mm). Whereas strut insertion caused the highest mean increase in NLA, tip spanning was the most effective regarding change of NTP. Expectably cephalic resection was associated with decrease in NLA and NTP.

A potential new biomarker in HNSCC: metastasis suppressor protein 1 (MTSS1).

OBJECTIVE: Metastasis suppressor protein 1 (MTSS1) is a prognostic tumour marker in different malignant epithelial tumour entities and previously mainly the MTSS1 expression was analysed. This study evaluated the best analysis method as a prognosis and aggressiveness tumour marker in head and neck squamous cell carcinoma (HNSCC). STUDY DESIGN: MTSS1 expression, MTSS1 intensity, interpretation MTSS1 score and MTSS1 edging score were analysed in formalin-fixed paraffin-embedded tissue slices of 60 patients with proven HNSCC and correlated with clinical and pathological outcome parameters. RESULTS: A lack of MTSS1 expression showed tumour aggressiveness, but surprisingly, mainly MTSS1 intensity was correlated with a worse patient outcome. There was a significant correlation between higher MTSS1 intensity and an increased risk for lymph node metastasis (P = .027) and a significant increased risk for extracapsular growth (P = .016). Furthermore, disease-specific survival was worse in cases with higher MTSS1 intensity (P = .001). CONCLUSION: MTSS1 intensity has a high scientific potential for further studies and could potentially be used as a prognostic marker in diagnostic and therapeutic decision-making.

New Tumor Budding Evaluation in Head and Neck Squamous Cell Carcinomas.

BACKGROUND: Tumor budding (TB) is a histomorphological characteristic of the tumor invasion front and it has an impact on the tumor outcome prediction for head and neck squamous cell carcinoma (HNSCC) aetiopathology. PATIENTS AND METHODS: The average TB score (TB rel) of all tumor-positive marginal sections (n = 443) in the primary tumor was analyzed in the FFPE-fixed tumor slices of 66 patients with HNSCC, and they were compared with cryo-fixed sections. RESULTS: TB rel correlates with tumor aggressiveness (i.e., lymph node metastasis quantity, lymph node ratio, extra capsular growth, Pn1, pV1, grading). The TB scores often vary between the different tumor margins of FFPE sections in the same patient, and in many cases, they differ depending on the fixation method. CONCLUSION: Our data show that a randomly selected marginal cut cannot reliably mirror the TB score, and thus, they cannot predict the prognostic outcome. However, TB rel could be a tool that compensates for differences in TB score analysis. TB score determination in cryo sections seems to be inaccurate compared with TB determination in FFPE.

Full-thickness skin graft versus split-thickness skin graft for radial forearm free flap donor site closure: protocol for a systematic review and meta-analysis.

BACKGROUND: The radial forearm free flap (RFFF) serves as a workhorse for a variety of reconstructions. Although there are a variety of surgical techniques for donor site closure after RFFF raising, the most common techniques are closure using a split-thickness skin graft (STSG) or a full-thickness skin graft (FTSG). The closure can result in wound complications and function and aesthetic compromise of the forearm and hand. The aim of the planned systematic review and meta-analysis is to compare the wound-related, function-related and aesthetics-related outcome associated with full-thickness skin grafts (FTSG) and split-thickness skin grafts (STSG) in radial forearm free flap (RFFF) donor site closure. METHODS: A systematic review and meta-analysis will be conducted. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines will be followed. Electronic databases and platforms (PubMed, Embase, Scopus, Web of Science, Cochrane Central Register of Controlled Trials (CENTRAL), China National Knowledge Infrastructure (CNKI)) and clinical trial registries (ClinicalTrials.gov, the German Clinical Trials Register, the ISRCTN registry, the International Clinical Trials Registry Platform) will be searched using predefined search terms until 15 January 2024. A rerun of the search will be carried out within 12 months before publication of the review. Eligible studies should report on the occurrence of donor site complications after raising an RFFF and closure of the defect. Included closure techniques are techniques that use full-thickness skin grafts and split-thickness skin grafts. Excluded techniques for closure are primary wound closure without the use of skin graft. Outcomes are considered wound-, functional-, and aesthetics-related. Studies that will be included are randomized controlled trials (RCTs) and prospective and retrospective comparative cohort studies. Case-control studies, studies without a control group, animal studies and cadaveric studies will be excluded. Screening will be performed in a blinded fashion by two reviewers per study. A third reviewer resolves discrepancies. The risk of bias in the original studies will be assessed using the ROBINS-I and RoB 2 tools. Data synthesis will be done using Review Manager (RevMan) 5.4.1. If appropriate, a meta-analysis will be conducted. Between-study variability will be assessed using the I2 index. If necessary, R will be used. The quality of evidence for outcomes will eventually be assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. DISCUSSION: This study's findings may help us understand both closure techniques' complication rates and may have important implications for developing future guidelines for RFFF donor site management. If available data is limited and several questions remain unanswered, additional comparative studies will be needed. SYSTEMATIC REVIEW REGISTRATION: The protocol was developed in line with the PRISMA-P extension for protocols and was registered with the International Prospective Register of Systematic Reviews (PROSPERO) on 17 September 2023 (registration number CRD42023351903).

Improving detection of oral lesions: Eye tracking insights from a randomized controlled trial comparing standardized to conventional approach.

BACKGROUND: Early detection of oral cancer (OC) or its precursors is the most effective measure to improve outcome. The reasons for missing them on conventional oral examination (COE) or possible countermeasures are still unclear. METHODS: In this randomized controlled trial, we investigated the effects of standardized oral examination (SOE) compared to COE. 49 dentists, specialists, and dental students wearing an eye tracker had to detect 10 simulated oral lesions drawn into a volunteer's oral cavity. RESULTS: SOE had a higher detection rate at 85.4% sensitivity compared to 78.8% in the control (p = 0.017) due to higher completeness (p < 0.001). Detection rate correlated with examination duration (p = 0.002). CONCLUSIONS: A standardized approach can improve systematics and thereby detection rates in oral examinations. It should take at least 5 min. Perceptual and cognitive errors and improper technique cause oral lesions to be missed. Its wide implementation could be an additional strategy to enhance early detection of OC.

Material attrition and bone micromorphology after conventional and ultrasonic implant site preparation.

OBJECTIVES: Little is known about the recently introduced ultrasonic implant site preparation. The purpose of this study was to compare material attrition and micromorphological changes after ultrasonic and conventional implant site preparations. MATERIAL AND METHODS: Implant site preparations were performed on fresh bovine ribs using one conventional (Straumann, Freiburg, Germany) and two ultrasonic (Piezosurgery; Mectron Medical Technology, Carasco, Italy and Variosurg; NSK, Tochigi, Japan) systems with sufficient saline irrigation. Sections were examined by environmental scanning electron microscopy (ESEM). Energy-dispersive X-ray spectroscopy (EDX) was performed to evaluate the metal attrition within the bone and the irrigation fluid. RESULTS ESEM: After conventional osteotomy, partially destroyed trabecular structures of the cancellous bone that were loaded with debris were observed, whereas after ultrasonic implant site preparations, the anatomic structures were preserved. EDX: None of the implant site preparation methods resulted in metal deposits in the adjacent bone structures. However, within the irrigation liquid, there was significantly higher metal attrition with ultrasonic osteotomy (P < 0.0001 and P < 0.0001 for Mectron and NSK, respectively). Whereas for Straumann system used, 15.5% of the SEM/EDX findings were drill-origin metals, this percentage increased to 37.3% and 37.9% with the application of Mectron and NSK, respectively. CONCLUSIONS: Ultrasonic implant site preparation is associated with the preservation of bone microarchitecture and with the increased attrition of metal particles. Therefore, copious irrigation seems to be even more essential for ultrasonic implant site preparation than for the conventional method.

Neck hairline incision for simultaneous harvesting of temporal and mastoid fasciae: a technical note.

Fasciae are known reservoirs of ideal graft material. The temporalis and mastoid fasciae are 2 of the most important graft reservoirs used by plastic surgeons, otolaryngologists, and oral and maxillofacial surgeons. The temporalis fascia is harvested predominantly by plastic surgeons, whereas otolaryngologists often prefer the mastoid fascia. In either case, graft harvesting might be accompanied by donor-site complications, such as hair loss, bleeding, hematoma, and scar formation, which can limit its application. To gain access to the temporal and mastoid fasciae simultaneously, the authors combined conventional techniques to develop a modified single-approach incision line that would minimize most donor-site complications.

Lateral crural transposition flap in tip correction: Tehran retrospective rhinoplasty experience.

PURPOSE: This study aims to review the authors' experience with the lower lateral crura (LLC) transposition flap in an attempt to highlight its advantages, indications, and limitations. MATERIALS AND METHODS: A retrospective study of 37 rhinoplasties (29 primary cases, 7 secondary cases, and 1 tertiary case) was performed. In all of these, an LLC transposition flap was used by inserting the cephalic portion of the LLCs into a subperichondrial pocket between the medial aspect of the remaining rim strip and the vestibular skin, based on the posterior pedicle. RESULTS: The most prevalent symptom among our patients was nasal external valve dysfunction. Concavity of the LLCs was very common. The LLC transposition flap can correct the LLC deformities with a high rate of patient satisfaction and no need for revision operations. CONCLUSIONS: The LLC transposition flap can overcome the common irregularities of the LLCs and could be applied to primary and secondary rhinoplasties, as well as ethnic noses.

Long-term outcome assessment of closed treatment of mandibular fractures.

Mandibular fractures are among the most common trauma injuries of the craniomaxillofacial region. This study evaluated the late results of mandibles fractures treated with arch bar. Forty-nine patients were examined clinically and by questionnaires for late results of arch bar treatment. Demographic data (age, sex, etc), trigeminal nerve sensation (Weber test), temporomandibular joint evaluation, masticatory muscle function, and occlusion were recorded. The data were analyzed by χ test using Sigma Stat 2.0 software. Fifty-one percent of the patients with angular fractures complained of sensory disturbances. Condylar and angular fractures demonstrated higher levels of pain. According to Pearson χ test, a statistically significant relation between angular fracture and tenderness of the internal pterygoid muscles (P = 0.047), angular fracture and cross-bite (P = 0.021), parasymphysial fracture and pain upon wind blowing (P = 0.026), and body fracture and mastication discomfort (P = 0.038) was found. In closed reduction therapy, fracture location of the mandible seems to be more likely correlated in producing particular long-term complications. Regular follow-ups for functional treatments and physiotherapy of chewing muscles and temporomandibular joint, along with removal of occlusal abnormalities, should be considered following arch bar reduction of mandibular fractures.

Development of machine learning and multivariable models for predicting blood transfusion in head and neck microvascular reconstruction for risk-stratified patient blood management.

BACKGROUND: Although blood transfusions have adverse consequences for microvascular head and neck reconstruction, they are frequently administered. Pre-identifying patients would allow risk-stratified patient blood management. METHODS: Development of machine learning (ML) and logistic regression (LR) models based on retrospective inclusion of 657 patients from 2011 to 2021. Internal validation and comparison with models from the literature by external validation. Development of a web application and a score chart. RESULTS: Our models achieved an area under the receiver operating characteristic curve (ROC-AUC) of up to 0.825, significantly outperforming LR models from the literature. Preoperative hemoglobin, blood volume, duration of surgery and flap type/size were strong predictors. CONCLUSIONS: The use of additional variables improves the prediction for blood transfusion, while models seems to have good generalizability due to surgical standardization and underlying physiological mechanism. The ML models developed showed comparable predictive performance to an LR model. However, ML models face legal hurdles, whereas score charts based on LR could be used after further validation.

Tolerable degree of muscle sacrifice when harvesting a vastus lateralis or myocutaneous anterolateral thigh flap.

The myocutaneous anterolateral thigh (ALT) and vastus lateralis (VL) flaps include a large muscle mass and a sufficient vascular pedicle, and they have been used for decades to reconstruct traumatic and acquired defects of the head and neck and extremities. In spite of these benefits, musculoskeletal dysfunction was reported in nearly 1 out of 20 patients at follow-up. It is unclear whether the recently proposed muscle-sparing flap-raising approach could preserve VL muscle function and whether patients at increased risk could benefit from such an approach. Therefore, we performed a predictive dynamic gait simulation based on a biological motion model with gradual weakening of the VL during a self-selected and fast walking speed to determine the compensable degree of VL muscle reduction. Muscle force, joint angle, and joint moment were measured. Our study showed that VL muscle reduction could be compensated up to a certain degree, which could explain the observed incidence of musculoskeletal dysfunction. In elderly or fragile patients, the VL muscle should not be reduced by 50% or more, which could be achieved by muscle-sparing flap-raising of the superficial partition only. In young or athletic patients, a VL muscle reduction of 10%, which corresponds to a muscle cuff, has no relevant effect. Yet, a reduction of more than 30% leads to relevant weakening of the quadriceps. Therefore, in this patient population with the need for a large portion of muscle, alternative flaps should be considered. This study can serve as the first basis for further investigations of human locomotion after flap-raising.

Effect of head-mounted displays on students' acquisition of surgical suturing techniques compared to an e-learning and tutor-led course: a randomized controlled trial.

BACKGROUND: Although surgical suturing is one of the most important basic skills, many medical school graduates do not acquire sufficient knowledge of it due to its lack of integration into the curriculum or a shortage of tutors. E-learning approaches attempt to address this issue but still rely on the involvement of tutors. Furthermore, the learning experience and visual-spatial ability appear to play a critical role in surgical skill acquisition. Virtual reality head-mounted displays (HMDs) could address this, but the benefits of immersive and stereoscopic learning of surgical suturing techniques are still unclear. MATERIAL AND METHODS: In this multi-arm randomized controlled trial, 150 novices participated. Three teaching modalities were compared: an e-learning course (monoscopic), an HMD-based course (stereoscopic, immersive), both self-directed and a tutor-led course with feedback. Suturing performance was recorded by video camera both before and after course participation (>26 h of video material) and assessed in a blinded fashion using the Objective Structured Assessment of Technical Skills (OSATS) Global Rating Score (GRS). Furthermore, the optical flow of the videos was determined using an algorithm. The number of sutures performed was counted, the visual-spatial ability was measured with the Mental Rotation Test (MRT), and courses were assessed with questionnaires. RESULTS: Students' self-assessment in the HMD-based course was comparable to that of the tutor-led course and significantly better than in the e-learning course ( P =0.003). Course suitability was rated best for the tutor-led course ( x̄ =4.8), followed by the HMD-based ( x̄ =3.6) and e-learning ( x̄ =2.5) courses. The median ΔGRS between courses was comparable ( P =0.15) at 12.4 (95% CI 10.0-12.7) for the e-learning course, 14.1 (95% CI 13.0-15.0) for the HMD-based course, and 12.7 (95% CI 10.3-14.2) for the tutor-led course. However, the ΔGRS was significantly correlated with the number of sutures performed during the training session ( P =0.002), but not with visual-spatial ability ( P =0.615). Optical flow ( R2 =0.15, P <0.001) and the number of sutures performed ( R2 =0.73, P <0.001) can be used as additional measures to GRS. CONCLUSION: The use of HMDs with stereoscopic and immersive video provides advantages in the learning experience and should be preferred over a traditional web application for e-learning. Contrary to expectations, feedback is not necessary for novices to achieve a sufficient level in suturing; only the number of surgical sutures performed during training is a good determinant of competence improvement. Nevertheless, feedback still enhances the learning experience. Therefore, automated assessment as an alternative feedback approach could further improve self-directed learning modalities. As a next step, the data from this study could be used to develop such automated AI-based assessments.

Advantages of a Training Course for Surgical Planning in Virtual Reality for Oral and Maxillofacial Surgery: Crossover Study.

BACKGROUND: As an integral part of computer-assisted surgery, virtual surgical planning (VSP) leads to significantly better surgery results, such as for oral and maxillofacial reconstruction with microvascular grafts of the fibula or iliac crest. It is performed on a 2D computer desktop screen (DS) based on preoperative medical imaging. However, in this environment, VSP is associated with shortcomings, such as a time-consuming planning process and the requirement of a learning process. Therefore, a virtual reality (VR)-based VSP application has great potential to reduce or even overcome these shortcomings due to the benefits of visuospatial vision, bimanual interaction, and full immersion. However, the efficacy of such a VR environment has not yet been investigated. OBJECTIVE: This study aimed to demonstrate the possible advantages of a VR environment through a substep of VSP, specifically the segmentation of the fibula (calf bone) and os coxae (hip bone), by conducting a training course in both DS and VR environments and comparing the results. METHODS: During the training course, 6 novices were taught how to use a software application in a DS environment (3D Slicer) and in a VR environment (Elucis) for the segmentation of the fibula and os coxae, and they were asked to carry out the maneuvers as accurately and quickly as possible. Overall, 13 fibula and 13 os coxae were segmented for each participant in both methods (VR and DS), resulting in 156 different models (78 fibula and 78 os coxae) per method (VR and DS) and 312 models in total. The individual learning processes in both environments were compared using objective criteria (time and segmentation performance) and self-reported questionnaires. The models resulting from the segmentation were compared mathematically (Hausdorff distance and Dice coefficient) and evaluated by 2 experienced radiologists in a blinded manner. RESULTS: A much faster learning curve was observed for the VR environment than the DS environment (ß=.86 vs ß=.25). This nearly doubled the segmentation speed (cm3/min) by the end of training, leading to a shorter time (P<.001) to reach a qualitative result. However, there was no qualitative difference between the models for VR and DS (P=.99). The VR environment was perceived by participants as more intuitive and less exhausting, and was favored over the DS environment. CONCLUSIONS: The more rapid learning process and the ability to work faster in the VR environment could save time and reduce the VSP workload, providing certain advantages over the DS environment.

Alveolar bone stress around implants with different abutment angulation: an FE-analysis of anterior maxilla.

OBJECTIVES: To comparatively assess the masticatory stress distribution in bone around implants placed in the anterior maxilla with three different labial inclinations. MATERIALS AND METHODS: Three-dimensional finite element models were fabricated for three situations in anterior maxilla: (1) a fixture in contact with buccal cortical plate restored by straight abutment, (2) a fixture inclined at 15 degrees, and (3) 20 degrees labially restored with corresponding angled abutment. A palatal bite force of 146 N was applied to a point 3 mm below the incisal edge. Stress distribution around the bone-fixture interface was determined using ANSYS software. RESULTS: The maximum compressive stress, concentrated in the labial crestal cortical bone, was measured to be 62, 108, and 122 MPa for 0-, 15-, and 20-degree labially inclined fixtures, respectively. The maximum tensile stress, concentrated in the palatal crestal cortical bone, was measured to be 60, 108, and 120 MPa for 0-, 15-, and 20-degree labially inclined fixtures, respectively. CONCLUSIONS: While all compressive stress values were under the cortical yield strength of 169 MPa, tensile stress values partially surpassed the yield strength (104 MPa) especially when a 20-degree inclination was followed for fixture placement.