Search

Accurate implant placement is essential for the success of dental implants. This placement influences osseointegration and occlusal forces. The freehand technique, despite its cost-effectiveness and time efficiency, may result in significant angular deviations compared with guided implantation, but the effect of angular deviations on the stress-strain state of peri-implant bone is unclear. The purpose of this finite element analysis (FEA) study was to examine the effects of angular deviations on stress-strain states in peri-implant bone. Computational modeling was used to investigate 4 different configurations of dental implant positions, each with 3 angles of insertion. The model was developed using computed tomography images, and typical mastication forces were considered. Strains were analyzed using the mechanostat hypothesis. The location of the implant had a significant impact on bone strain intensity. An angular deviation of ±5 degrees from the planned inclination did not significantly affect cancellous bone strains, which primarily support the implant. However, it had a substantial effect on strains in the cortical bone near the implant. Such deviations also significantly influenced implant stresses, especially when the support from the cortical bone was uneven or poorly localized. In extreme situations, angular deviations can lead to overstraining the cortical bone, risking implant failure from unfavorable interaction with the implant. Accurate implant placement is essential to mitigate these risks. [ABSTRACT FROM AUTHOR]

Fractures of the orbital floor are often a result of traffic accidents or interpersonal violence. To date, numerous materials and methods have been used to reconstruct the orbital floor. However, simple and cost-effective 3-dimensional (3D) printing technologies for the treatment of orbital floor fractures are still sought. This study describes a simple, precise, cost-effective method of treating orbital fractures using 3D printing technologies in combination with autologous bone. Enophthalmos and diplopia developed in a 64-year-old female patient with an orbital floor fracture. A virtual 3D model of the fracture site was generated from computed tomography images of the patient. The fracture was virtually closed using spline interpolation. Furthermore, a virtual individualized mold of the defect site was created, which was manufactured using an inkjet printer. The tangible mold was subsequently used during surgery to sculpture an individualized autologous orbital floor implant. Virtual reconstruction of the orbital floor and the resulting mold enhanced the overall accuracy and efficiency of the surgical procedure. The sculptured autologous orbital floor implant showed an excellent fit in vivo. The combination of virtual planning and 3D printing offers an accurate and cost-effective treatment method for orbital floor fractures. [ABSTRACT FROM AUTHOR]

This computational study investigates the effect of shape (defect contour curvature) and bone-implant interface (osteotomy angle) on the stress distribution within PMMA skull implants. Using finite element methodology, 15 configurations – combinations of simplified synthetic geometric shapes (circular, square, triangular, irregular) and interface angulations – were simulated under 50N static loads. Furthermore, the implant fixation devices were modelled and analysed in detail. Negative osteotomy configurations demonstrated the largest stresses in the implant (275 MPa), fixation devices (1258 MPa) and bone strains (0.04). The circular implant with zero and positive osteotomy performed well with maximum observed magnitudes of – implant stress (1.2 MPa and 1.2 MPa), fixation device stress (11.2 MPa and 2.2 MPa), bone strain (0.218e-3 and 0.750e-4). The results suggest that the preparation of defect sites is a critical procedure. Of the greatest importance is the angle at which the edges of the defect are sawed. If under an external load, the implant has no support from the interface and the stresses are transferred to the fixation devices. This can endanger their material integrity and lead to unphysiological strains in the adjacent bone, potentially compromising the bone morphology required for anchoring. These factors can ultimately weaken the stability of the entire implant assembly. [ABSTRACT FROM AUTHOR]

Additive manufacturing is the process of joining materials to create objects from digital 3-dimensional (3D) model data, which is a promising technology in oral and maxillofacial surgery. The management of lost craniofacial tissues owing to congenital abnormalities, trauma, or cancer treatment poses a challenge to oral and maxillofacial surgeons. Many strategies have been proposed for the management of such defects, but autogenous bone grafts remain the gold standard for reconstructive bone surgery. Nevertheless, cell-based treatments using adipose stem cells combined with osteoconductive biomaterials or scaffolds have become a promising alternative to autogenous bone grafts. Such treatment protocols often require customized 3D scaffolds that fulfill functional and esthetic requirements, provide adequate blood supply, and meet the load-bearing requirements of the head. Currently, such customized 3D scaffolds are being manufactured using additive manufacturing technology. In this review, 2 of the current and emerging modalities for reconstruction of oral and maxillofacial bone defects are highlighted and discussed, namely human maxillary sinus floor elevation as a valid model to test bone tissue-engineering approaches enabling the application of 1-step surgical procedures and seeding of Good Manufacturing Practice-level adipose stem cells on computer-aided manufactured scaffolds to reconstruct large bone defects in a 2-step surgical procedure, in which cells are expanded ex vivo and seeded on resorbable scaffolds before implantation. Furthermore, imaging-guided tissue-engineering technologies to predetermine the surgical location and to facilitate the manufacturing of custom-made implants that meet the specific patient's demands are discussed. The potential of tissue-engineered constructs designed for the repair of large oral and maxillofacial bone defects in load-bearing situations in a 1-step surgical procedure combining these 2 innovative approaches is particularly emphasized. [ABSTRACT FROM AUTHOR]

The aim of the present study was to assess the indications, results and complications of patients treated with porous polyethylene (Medpor ® ) implants in the Department of Oral and Maxillofacial Surgery of VU Medical Centre, Amsterdam over 17 years. A total of 69 high-density porous polyethylene implants (Medpor ® Biomaterial; Porex Surgical, Newman, GA) were used in forty patients (22 males, 18 females). All patients were analysed for gender, age, diagnosis, indications for surgery, follow-up period and postoperative complications. A mean age of 34.1 years was observed. The main reason for implant surgery was post-traumatic functional impairment (27.5%). Most implants were placed at the mandibular angel and the orbital floor. Unsatisfactory appearance scored the highest in postoperative complications (10.1%) followed by infection rate (7.2%). Comparing the number of implants placed over the years and the incidence of complications, makes the overall complications rate of porous polyethylene very low. A consensus about antibiotic prophylaxis is needed. The objective measurements in patient satisfaction and proper implant design would be of great use. [ABSTRACT FROM AUTHOR]

Objective The aim of this article was to review and discuss papers that were published during the past 30 years regarding the distribution and characteristics of motor vehicle accidents-related facial injuries throughout the world. Methods We systematically reviewed all papers that were published in English between January 1980 and December 2013 using MEDLINE and the MeSH term “facial fractures” together with the term “motor vehicle”. Results The percentage of motor vehicle accidents as an etiological factor in epidemiological studies about maxillofacial injuries ranged between 11% and 85%. On the whole, a progressively decreasing trend was observed, particularly in North America, Brazil, and Europe. Discussion Motor vehicle accidents are still one of the most important etiological factors for maxillofacial injuries. A great difference in the incidence of this kind of fractures between developed countries and developing countries can be observed. [ABSTRACT FROM AUTHOR]

Highlights: [•] 10 Peri-implantitis cases treated with 4 different implant geometries are studied. [•] Geometries in clinically observed bone loss states are analysed using FEA method. [•] Implant geometry and bone morphology affect induced strains in adjacent bone. [•] Bone loss around implants increases pathological strain in the bone. [•] Suboptimal geometry may induce progressive bone loss leading to complete failure. [Copyright &y& Elsevier]

Background: Additive manufacturing (AM) is being increasingly used for producing medical models. The accuracy of these models varies between different materials, AM technologies and machine runs. Purpose: To determine the accuracy of selective laser sintering (SLS), three-dimensional printing (3DP) and PolyJet technologies in the production of medical models. Material: 3D skull models: “original”, “moderate” and “worse”. SLS, 3DP and PolyJet models, and a coordinate measuring machine (CMM). Methods: Measuring balls designed for measurements were attached to each 3D model. Skull models were manufactured using SLS, 3DP and PolyJet. The midpoints of the balls were determined using CMM. The distances between these points were calculated and compared with the 3D model. Results: The dimensional error for the PolyJet was 0.18 ± 0.12% (first measurement) and 0.18 ± 0.13% (second measurement), for SLS 0.79 ± 0.26% (first model) and 0.80 ± 0.32% (second model), and for 3DP 0.67 ± 0.43% (original model, first measurement) and 0.69 ± 0.44% (original model, second measurement), 0.38 ± 0.22% (moderate model) and 0.55 ± 0.37% (worse model). Repeatability of the measurement method was 0.12% for the PolyJet and 0.08% for the 3DP. Conclusion: A novel measuring technique was developed and its repeatability was found to be good. The accuracy of the PolyJet was higher when compared with SLS or 3DP. [ABSTRACT FROM AUTHOR]

PURPOSE: Large mandibular resection defects historically have been treated using autogenous bone grafts and reconstruction plates. However, a major drawback of large autogenous bone grafts is donor-site morbidity. PATIENTS AND METHODS: This report describes the replacement of a 10-cm anterior mandibular ameloblastoma resection defect, reproducing the original anatomy of the chin, using a tissue-engineered construct consisting of [beta]-tricalcium phosphate ([beta]-TCP) granules, recombinant human bone morphogenetic protein-2 (BMP-2), and Good Manufacturing Practice-level autologous adipose stem cells (ASCs). Unlike prior reports, 1-step in situ bone formation was used without the need for an ectopic bone-formation step. The reconstructed defect was rehabilitated with a dental implant-supported overdenture. An additive manufactured medical skull model was used preoperatively to guide the prebending of patient-specific hardware, including a reconstruction plate and titanium mesh. A subcutaneous adipose tissue sample was harvested from the anterior abdominal wall of the patient before resection and simultaneous reconstruction of the parasymphysis. ASCs were isolated and expanded ex vivo over the next 3 weeks. The cell surface marker expression profile of ASCs was similar to previously reported results and ASCs were analyzed for osteogenic differentiation potential in vitro. The expanded cells were seeded onto a scaffold consisting of [beta]-TCP and BMP-2 and the cell viability was evaluated. The construct was implanted into the parasymphyseal defect. RESULTS: Ten months after reconstruction, dental implants were inserted into the grafted site, allowing harvesting of bone cores. Histologic examination and in vitro analysis of cell viability and cell surface markers were performed and prosthodontic rehabilitation was completed. CONCLUSION: ASCs in combination with [beta]-TCP and BMP-2 offer a promising construct for the treatment of large, challenging mandibular defects without the need for ectopic bone formation and allowing rehabilitation with dental implants. [ABSTRACT FROM AUTHOR]

Patient-specific approach is gaining a wide popularity in computational simulations of biomechanical systems. Simulations (most often based on the finite element method) are to date routinely created using data from imaging devices such as computed tomography which makes the models seemingly very complex and sophisticated. However, using a computed tomography in finite element calculations does not necessarily enhance the quality or even credibility of the models as these depend on the quality of the input images. Low-resolution (medical-)CT datasets do not always offer detailed representation of trabecular bone in FE models and thus might lead to incorrect calculation of mechanical response to external loading. The effect of image resolution on mechanical simulations of bone-implant interaction has not been thoroughly studied yet. In this study, the effect of image resolution on the modeling procedure and resulting mechanical strains in bone was analyzed on the example of cranial implant. For this purpose, several finite element models of bone interacting with fixation-screws were generated using seven computed tomography datasets of a bone specimen but with different image resolutions (ranging from micro-CT resolution of 25 μm to medical-CT resolution of 1250 μm). The comparative analysis revealed that FE models created from images of low resolution (obtained from medical computed tomography) can produce biased results. There are two main reasons: 1. Medical computed tomography images do not allow generating models with complex trabecular architecture which leads to substituting of the intertrabecular pores with a fictitious mass; 2. Image gray value distribution can be distorted resulting in incorrect mechanical properties of the bone and thus in unrealistic or even completely fictitious mechanical strains. The biased results of calculated mechanical strains can lead to incorrect conclusion, especially when bone-implant interaction is investigated. The image resolution was observed not to significantly affect stresses in the fixation screw itself; however, selection of bone material representation might result in significantly different stresses in the screw. [ABSTRACT FROM AUTHOR]

Objective: This retrospective study evaluated survival rates, prognosis, and overall success of autotransplanted teeth in young patients missing anterior teeth as a result of trauma, agenesis, or developmental disturbances.Study Design: Retrospective data were collected from the medical records of patients who had undergone tooth autotransplantations to anterior sites between January 2001 and December 2012. Clinical variables, such as gender, age, surgical indications, donor and recipient sites, type of anesthetics, bone augmentation, and complications during follow-up, were assessed.Results: A total of 59 donor teeth in 46 patients (30 boys and 16 girls; average age 12.15 years) were autotransplanted to the anterior region of the maxilla and mandible. After a mean follow-up period of 17.35 months (range 10-61 months), all of the transplanted teeth remained in situ with no complications.Conclusions: This study supports the autotransplantation of teeth to the anterior alveolus as a viable option suitable in growing patients with missing anterior teeth. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

Background: Over the last decades, dental implants have become increasingly popular in the prosthetic rehabilitation of patients. This has subsequently led to an increase of perioperative complications. Obstruction of the airway as a result of a floor of mouth hematoma after dental implant surgery is a rare but life-threatening complication.Case Report: A 62-year-old man presented to the emergency department with a compromised airway caused by a hematoma in the floor of the mouth that occurred during dental implant surgery in the edentulous anterior mandible. Computed tomography angiography images revealed an elevation of the floor of mouth with subsequent occlusion of the airway. In addition, a perforation of the lingual mandibular cortical plate was observed that was caused by two malpositioned dental implants. Awake fiberoptic intubation was immediately performed, the two malpositioned dental implants were subsequently removed, and the patient was extubated after 3 days. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Perforation of the lingual mandibular cortical plate during dental implant surgery can lead to life-threatening bleeding in the floor of the mouth. This condition can be successfully treated by awake fiberoptic intubation and, if necessary, the malpositioned dental implants can be subsequently removed. [ABSTRACT FROM AUTHOR]

Aim of the study The accuracy of additive manufactured medical constructs is limited by errors introduced during image segmentation. The aim of this study was to review the existing literature on different image segmentation methods used in medical additive manufacturing. Methods Thirty-two publications that reported on the accuracy of bone segmentation based on computed tomography images were identified using PubMed, ScienceDirect, Scopus, and Google Scholar. The advantages and disadvantages of the different segmentation methods used in these studies were evaluated and reported accuracies were compared. Results The spread between the reported accuracies was large (0.04 mm – 1.9 mm). Global thresholding was the most commonly used segmentation method with accuracies under 0.6 mm. The disadvantage of this method is the extensive manual post-processing required. Advanced thresholding methods could improve the accuracy to under 0.38 mm. However, such methods are currently not included in commercial software packages. Statistical shape model methods resulted in accuracies from 0.25 mm to 1.9 mm but are only suitable for anatomical structures with moderate anatomical variations. Conclusions Thresholding remains the most widely used segmentation method in medical additive manufacturing. To improve the accuracy and reduce the costs of patient-specific additive manufactured constructs, more advanced segmentation methods are required. [ABSTRACT FROM AUTHOR]

Objectives: In the Netherlands, cyclists continue to outnumber other road users in injuries and deaths. The wearing of bicycle helmets is not mandatory in the Netherlands even though research has shown that wearing bicycle helmets can reduce head and brain injuries by up to 88%. Therefore, the aim of this study was to assess the feasibility of using 3D technology to evaluate bicycle-related head injuries and helmet protection.Methods: Three patients who had been involved in a bicycle accident while wearing a helmet were subjected to multi-detector row computed tomography (MDCT) imaging after trauma. The helmets were separately scanned using the same MDCT scanner with tube voltages ranging from 80kVp to 140kVp and tube currents ranging from 10mAs to 300mAs in order to determine the best image acquisition parameters for helmets. The acquired helmet images were converted into virtual 3D surface hence Standard Tessellation Language (STL) models and merged with MDCT-derived STL models of the patients' skulls. Finally, all skull fractures and corresponding helmet damage were visualized and related.Results: Imaging bicycle helmets on an MDCT scanner proved to be feasible using a tube voltage of 120kVp and a tube current of 120mAs. Merging the resulting STL models of the patients' skull and helmet allowed the overall damage sustained by both skull and helmet to be related.Conclusion: Our proposed 3D method of assessing bicycle helmet damage and corresponding head injuries could offer valuable information for the development and design of safer bicycle helmets. [ABSTRACT FROM AUTHOR]

Recent developments in craniofacial reconstruction have shown important advances in both the materials and methods used. While autogenous tissue is still considered to be the gold standard for these reconstructions, the harvesting procedure remains tedious and in many cases causes significant donor site morbidity. These limitations have subsequently led to the development of less invasive techniques such as 3D bioprinting that could offer possibilities to manufacture patient-tailored bioactive tissue constructs for craniofacial reconstruction. Here, we discuss the current technological and (pre)clinical advances of 3D bioprinting for use in craniofacial reconstruction and highlight the challenges that need to be addressed in the coming years. [ABSTRACT FROM AUTHOR]

The first aim of this study was to assess displacements and micro-strain induced on different grades of atrophic cortical and trabecular mandibular bone by axially loaded dental implants using finite element analysis (FEA). The second aim was to assess the micro-strain induced by different implant geometries and the levels of bone-to-implant contact (BIC) on the surrounding bone. Six mandibular bone segments demonstrating different grades of mandibular bone atrophy and various bone volume fractions (from 0.149 to 0.471) were imaged using a micro-CT device. The acquired bone STL models and implant (Brånemark, Straumann, Ankylos) were merged into a three-dimensional finite elements structure. The mean displacement value for all implants was 3.1±1.2 μm. Displacements were lower in the group with a strong BIC. The results indicated that the maximum strain values of cortical and cancellous bone increased with lower bone density. Strain distribution is the first and foremost dependent on the shape of bone and architecture of cancellous bone. The geometry of the implant, thread patterns, grade of bone atrophy and BIC all affect the displacement and micro-strain on the mandible bone. Preoperative finite element analysis could offer improved predictability in the long-term outlook of dental implant restorations. [ABSTRACT FROM AUTHOR]

Large mandibular continuity defects pose a significant challenge in oral maxillofacial surgery. One solution to this problem is to use computer-guided surgical planning and additive manufacturing technology to produce patient-specific reconstruction plates. However, when designing customized plates, it is important to assess potential biomechanical responses that may vary substantially depending on the size and geometry of the defect. The aim of this study was to assess the design of two customized plates using finite element method (FEM). These plates were designed for the reconstruction of the lower left mandibles of two ameloblastoma cases (patient 1/plate 1 and patient 2/plate 2) with large bone resections differing in both geometry and size. Simulations revealed maximum von Mises stresses of 63 MPa and 108 MPa in plates 1 and 2, and 65 MPa and 190 MPa in the fixation screws of patients 1 and 2. The equivalent strain induced in the bone at the screw-bone interface reached maximum values of 2739 micro-strain for patient 1 and 19,575 micro-strain for patient 2. The results demonstrate the influence of design on the stresses induced in the plate and screw bodies. Of particular note, however, are the differences in the induced strains. Unphysiologically high strains in bone adjacent to screws can cause micro- damage leading to bone resorption. This can adversely affect the anchoring capabilities of the screws. Thus, while custom plates offer optimal anatomical fit, attention should be paid to the expected physiological forces on the plates and the induced stresses and strains in the plate-screw-bone assembly. [ABSTRACT FROM AUTHOR]