Feasibility of carbon-fiber-reinforced polymer fixation plates for treatment of atrophic mandibular fracture: A finite element method

Biomechanical comparison of the efficacy of Cfr-PEEK and titanium systems in the fixation following sagittal split advancement osteotomy: a biomechanical study

BACKGROUND

This study evaluates the efficacy of carbon fiber reinforced Polyetheretherketone (Cfr-PEEK) in fixation after sagittal split ramus osteotomy (SSRO) by comparing it with titanium in vitro.

METHODS

Twenty-eight sheep hemimandibles were randomly assigned to four groups for SSRO surgery. Fixation was performed with a 4-hole titanium mini plate for 5 mm advancement in Group 1, with a 4-hole Cfr-PEEK mini plate for 5 mm advancement for Group 2, with a 4-hole titanium mini plate for 10 mm advancement for Group 3, and with a 4-hole Cfr-PEEK mini plate for 10 mm advancement for Group 4. A linear vertical load of 50 N was applied to all models from the molar region. Displacement values were recorded digitally.

RESULTS

There was a significant difference among the displacement values of four groups (p < 0.05). The highest displacement values were observed in group 2 and the lowest in group 3. The Cfr-PEEK plates' fixed groups showed lower displacement values than their titanium counterparts.

CONCLUSIONS

According to this study, Cfr-PEEK provides better stability than titanium by considering the displacement values. However, future experimental and clinical studies that include larger samples and different designs need to be done.

Design of internal fixation implants for fracture: A review

Internal fixation is the most common and effective fracture treatment, and the design of Internal Fixation Implants (IFI) is important for fracture healing. In recent decades, IFI have been designed from the aspects of materials, geometry, fixation methods and functional characteristics. However, there has been no comprehensive summary on the evaluation method and design methods of IFI. This paper aims to review and analyze the key issues involved in the design of IFI, to provide references for IFI design. Firstly, the main factors affecting the healing effect are summarized and the design requirements of IFI are put forward through the analysis of fracture healing process. Secondly, the evaluation methods of IFI are compared and summarized, and the importance of evaluation methods based on fracture healing theory is emphasized. Subsequently, the properties and application scopes of common biomaterials for IFI are introduced. And the IFI, which is used widely, such as bone plate, intramedullary nail and embracing device, are summed up from the aspects of design factors and design methods. Highlight the distinctive contributions of additive manufacturing for the fabrication of implants and surface treatment for improving the multifunctionality of implants. Finally, the design concept of ideal IFI and the potential research content in the future are proposed based on the design requirements and the summary of the existing design studies.

The translational potential of this article

This study summarizes and analyzes the key issues involved in the design of IFI, which provide references for IFI design. A discussion on future research directions and suggestion were made, which is expected to advance the research in this field.

Evaluation of the biomechanical effects and stability of titanium and carbon fiber-reinforced polyetheretherketone mini plates in Le Fort I advancement osteotomy fixation using finite element analysis

AIM

This study aimed to investigate the biomechanical properties of 60 % carbon fiber-reinforced polyetheretherketone (Cfr-PEEK), which exhibits high mechanical strength and can address the limitations of titanium mini plates used in Le Fort I osteotomy.

MATERIAL AND METHOD

Models were created using the FEA method based on tomography images of adult individuals. A 5 mm maxillary advancement was applied to the models following Le Fort I osteotomy. Mini plates made of titanium and 60 % Cfr-PEEK were used. Support was provided by the nasomaxillary and zygomaticomaxillary buttresses to fix a total of four l-shaped mini plates. Oblique loads of 125 N, directed from palatal to buccal, and a total of 250 N compression loads were applied to the central fossa of the premolar and molar teeth in the maxillary model at a 30° angle relative to the long axis of the teeth. Displacement values at the osteotomy line, Von Mises stresses in the mini plate-screws, and principal stresses in the bone were compared.

RESULTS

Examination of stress values in the fixation systems of the models revealed higher stress values in the Cfr-PEEK model compared to the titanium model. However, these stresses did not reach levels that would deform the Cfr-PEEK fixation systems. Stress and displacement values in the bone were lower in the Cfr-PEEK model compared to the titanium model.

CONCLUSION

According to the findings of our study, Cfr-PEEK represents a viable alternative to titanium for mini plate material in Le Fort I osteotomy, offering biomechanical advantages.

Effects of condylar neck inclination and counterclockwise rotation on the stress distribution of the temporomandibular joint

Three different kinds of condylar inclination were manually modelled anteriorly inclined condylar neck, vertical condylar neck, and posteriorly inclined condylar neck. Three different maxillary impactions were simulated to evaluate the effect of counterclockwise rotation. The von Misses stresses of the disc, compressive stresses of the glenoid fossa, and compressive stresses of the condyle were the highest in the models with posteriorly inclined neck and lowest in the models with vertical condylar neck design. Stresses of the temporomandibular joint increase with the counterclockwise rotation of the maxilla-mandibular complex. The posteriorly inclined neck should be considered a risk factor for condylar resorption with increased counterclockwise rotation.

Influence of bite force and implant elastic modulus on mandibular reconstruction with particulate-cancellous bone marrow grafts healing: An in silico investigation

This study aims to investigate tissue differentiation during mandibular reconstruction with particulate cancellous bone marrow (PCBM) graft healing using biphasic mechanoregulation theory under four bite force magnitudes and four implant elastic moduli to examine its implications on healing rate, implant stress distribution, new bone elastic modulus, mandible equivalent stiffness, and load-sharing progression. The finite element model of a half Canis lupus mandible, symmetrical about the midsagittal plane, with two marginal defects filled by PCBM graft and stabilized by porous implants, was simulated for 12 weeks. Eight different scenarios, which consist of four bite force magnitudes and four implant elastic moduli, were tested. It was found that the tissue differentiation pattern corroborates the experimental findings, where the new bone propagates from the superior side and the buccal and lingual sides in contact with the native bone, starting from the outer regions and progressing inward. Faster healing and quicker development of bone graft elastic modulus and mandible equivalent stiffness were observed in the variants with lower bite force magnitude and or larger implant elastic modulus. A load-sharing condition was found as the healing progressed, with M3 (Ti6Al4V) being better than M4 (stainless steel), indicating the higher stress shielding potentials of M4 in the long term. This study has implications for a better understanding of mandibular reconstruction mechanobiology and demonstrated a novel in silico framework that can be used for post-operative planning, failure prevention, and implant design in a better way.

Biomechanical effects of inclined implant shoulder design in all-on-four treatment concept: a three-dimensional finite element analysis

OBJECTIVES

The aim of the present study was to assess the biomechanical behaviour of using a posterior implant design with inclined shoulder designs in all-on-four treatment via three-dimensional finite element analysis.

METHODS

Implants with standard and inclined shoulder designs were modelled for posterior implants. Implants were positioned into the maxilla and mandible models according to the all-on-four concept. Compressive stresses in the peri-implant bone, the von Mises stresses in the different components of the prosthetic restoration, and movement of the prosthesis were obtained.

RESULTS

The compressive stresses of the models with inclined shoulder design resulted in 15-58 % decrease compared with standard shoulder design. The von Mises stresses in the posterior implants reduced 18-47 %, stresses in the implant body increased 38-78 %, stresses in the abutment screw reduced 20-65 %, stresses in the framework of prosthesis reduced 1-18 % and deformation of the prosthesis was reduced 6-37 % in the models of inclined shoulder design compared with models of standard shoulder design. The compressive and von Mises stresses were generally higher in the mandible models than in the maxilla models for standard and inclined shoulder designs.

CONCLUSIONS

All evaluated components of the simulated treatment except for posterior abutment bodies showed better biomechanical behaviour with inclined shoulder design. The clinical success of all-on-four treatment maybe enhanced by using posterior implants with an inclined shoulder design.

Optimizing efficiency in the creation of patient-specific plates through field-driven generative design in maxillofacial surgery

Field driven design is a novel approach that allows to define through equations geometrical entities known as implicit bodies. This technology does not rely upon conventional geometry subunits, such as polygons or edges, rather it represents spatial shapes through mathematical functions within a geometrical field. The advantages in terms of computational speed and automation are conspicuous, and well acknowledged in engineering, especially for lattice structures. Moreover, field-driven design amplifies the possibilities for generative design, facilitating the creation of shapes generated by the software on the basis of user-defined constraints. Given such potential, this paper suggests the possibility to use the software nTopology, which is currently the only software for field-driven generative design, in the context of patient-specific implant creation for maxillofacial surgery. Clinical scenarios of applicability, including trauma and orthognathic surgery, are discussed, as well as the integration of this new technology with current workflows of virtual surgical planning. This paper represents the first application of field-driven design in maxillofacial surgery and, although its results are very preliminary as it is limited in considering only the distance field elaborated from specific points of reconstructed anatomy, it introduces the importance of this new technology for the future of personalized implant design in surgery.

Finite element analysis of different internal fixation methods for the treatment of atrophic mandible fractures

The aim of this study is to evaluate different plate systems and contribute to revealing the most appropriate treatment option for severe atrophic edentulous mandible fractures. A total of 8 different types of rigid internal fixation methods, which were a 4-hole miniplate on the crest, a 4-hole miniplate on the basis, a 6-hole miniplate on the crest, a 6-hole miniplate on the basis, two 4-hole mini plates on both the crest and basis, two 6-hole mini plates on both crest and basis, a 6-hole reconstruction plate on the crest and a 6-hole reconstruction plate on the basis, were simulated. Stress analysis on plates and screws and the displacement between fragments were evaluated using finite element analysis. The lowest von Mises stress was observed on the basis plate in Group 6. The highest von Mises stresses were measured on the screws closes to the fracture line. Values exceeding the boundary conditions were observed only in Groups 3 and 4 under molar loading. The highest compressive stresses were measured in Group 1, and the lowest compressive stresses were measured in Group 6. Under molar loading, the highest displacement was observed in Group 3, and the lowest displacement was observed in Group 6. When all groups are evaluated in terms of stress distributions and stability, a 1.5 mm thick six-hole reconstruction plate can be a reliable method in the treatment of severe atrophic edentulous mandible fractures.

Investigation of the biomechanical stability of Cfr-PEEK in the treatment of mandibular angulus fractures by finite element analysis

The purpose of this study is to explore the effectiveness of Cfr-PEEK, in the fixation of unfavorable fractures of mandibular angulus by comparing it with the titanium and resorbable biomaterials. 8 different fixation models were created. In the first 4 groups, a single mini plate was applied to the upper edge of the fracture line by the Champy method. In the other 4 groups, an additional plate was placed on the lower edge of the fracture line. In these models, titanium, resorbable and Cfr-PEEK plate/screw systems were investigated by the finite element analysis method. The highest Von Mises stress was observed on the upper plate in the group 5 while the lowest was seen in the lower plate in the group 7. The highest stress values on the screws were observed on the screws placed closer to the fracture line. Considering the stresses on the bone around the screws, the highest Pmax and Pmin values were seen in group 5, and the lowest values were seen in the group 7. The highest displacement was observed in the group 3, while the lowest was observed in the group 5. According to the results it can be said that Cfr-PEEK plate/screw systems may provide advantages by decreasing the stresses on the fixation systems over the titanium plates and providing more stable fixation over the resorbable systems. Cfr-PEEK plates of 2 mm thickness seems to be a potential alternative to 1 mm thick titanium plates.

An approach for simultaneous reduction and fixation of mandibular fractures

This article presents a new approach for the design of a flexible V-shaped miniplate for mandibular fractures, which combines simultaneous fracture reduction and fixation. A Computerized Tomography (CT) based finite element model was developed to assess the reliability of this design. Muscle and mastication forces were included to replicate post-surgery loading. The V-plate is compared with a standard, linear miniplate, typically used for mandibular fixation. The results indicate that the proposed design can support the fracture while inducing limited fracture displacement, in addition to reducing the duration of the surgery due to fracture reduction by tightening the wire.

A mechanical study of novel additive manufactured modular mandible fracture fixation plates - Preliminary Study with finite element analysis.✰

The paper presents an innovative osteofixation system designed for bone fracture stabilization. Its special feature, which makes it different from other similar systems, is the possibility to precisely adjust the implant to the shape of the bone. Such a precise adjustment is particularly important in the case of multiple fractures, where proper stabilization is a condition for restoring bone geometry and thus obtaining the biomechanical function of a given segment of the body lost due to fracture. Based on the tested properties of the implant material, the presented system structure was verified for loading, stress, and share forces in multi-site fractures of the mandible. Numerical tests were performed for three different fracture models: unilateral double fracture of the body of mandible, unilateral double fracture of the body and the angle of mandible, and bilateral fracture of the mandible at the angle and body of the mandible. The results indicate that the proposed system may be used to stabilize broken bone fragments successfully, and the obtained stabilization would allow unrestricted use of the chewing function during bone healing and remodeling. The authors point out the advantages of the proposed implantation method thanks to which it is possible to obtain any shape of the implant and thus stabilize bone fragments in any case.