Platelet-rich plasma for regeneration of neural feedback pathways around dental implants: a concise review and outlook on future possibilities

Along with the development of new materials, advanced medical imaging and surgical techniques, osseointegrated dental implants are considered a successful and constantly evolving treatment modality for the replacement of missing teeth in patients with complete or partial edentulism. The importance of restoring the peripheral neural feedback pathway and thus repairing the lack of periodontal rnechanoreceptors after tooth extraction has been highlighted in the literature. Nevertheless, regenerating the nerve fibers and reconstructing the neural feedback pathways around osseointegrated implants remain a challenge. Recent studies have provided evidence that platelet-rich plasma （PRP） therapy is a promising treatment for musculoskeletal injuries. Because of its high biological safety, convenience and usability, PRP therapy has gradually gained popularity in the clinical field Although much remains to be learned, the growth factors from PRP might play key roles in peripheral nerve repair mechanisms. This review presents known growth factors contributing to the biological efficacy of PRP and illustrates basic and （pre-）clinical evidence regarding the use of PRP and its relevant products in peripheral nerve regeneration. In addition, the potential of local application of PRP for structural and functional recovery of iniured peripheral nerves around dental implants is discussed.

Validation of a novel imaging approach using multi-slice CT and cone-beam CT to follow-up on condylar remodeling after bimaxillary surgery

The main goal of this study was to introduce a novel three-dimensional procedure to objectively quantify both inner and outer condylar remodelling on preoperative multi-slice computed tomography （MSCT） and postoperative cone-beam computed tomography （CBCT） images. Second, the reliability and accuracy of this condylar volume quantification method was assessed. The mandibles of 20 patients （11 female and 9 male） who underwent bimaxillary surgery were semi-automatically extracted from MSCT/CBCT scans and rendered in 3D. The resulting condyles were spatially matched by using an anatomical landmark-based registration procedure. A standardized sphere was created around each condyle, and the condylar bone volume within this selected region of interest was automatically calculated. To investigate the reproducibility of the method, inter- and intra-observer reliability was calculated for assessments made by two experienced radiologists twice five months apart in a set of ten randomly selected patients. To test the accuracy of the bone segmentation, the inner and outer bone structures of one dry mandible, scanned according to the clinical set-up, were compared with the gold standard, micro-CT. Thirty-eight condyles showed a significant （P〈O.05） mean bone volume decrease of 26.4%_ 11.4% （502.9 mm3＋ 268.1 mm3）. No significant effects of side, sex or age were found. Good to excellent （ICC〉 0.6） intra- and inter-observer reliability was observed for both MSCT and CBCT. Moreover, the bone segmentation accuracy was less than one voxel （0.4 mm） for MSCT （0.3 mm __. 0.2 mm） and CBCT （0.4 mm _ 0.3 mm）, thus indicating the clinical potential of this method for objective follow-up in pathological condylar resorption.

基于VTK的医用3D打印软件系统研究与开发

目的:开发出一套与现有的医学影像处理软件系统兼容的3D打印软件系统,实现更快速、便捷、高效的医用3D打印。方法:以VTK(Visualization Toolkit)为平台,使用Qt、CTK等开发工具,在现有的3D打印软件系统的基础上,对切片算法进行优化,尤其是多喷头打印功能,提出并实现支撑最优化算法。结果:开发了与医学影像处理软件兼容的3D打印软件系统MDPrinter。结论:MDPrinter软件系统可实现快速高效打印,切片速度、软件稳定性及支撑优化之后的模型表面质量均有较大提升,实现了基于多喷头的多材料多模型打印功能,有助于数字医学的信息化。

Use of long implants with distal anchorage in the skull base for treatment of extreme maxillary atrophy: The remote bone anchorage concept

The objectives of this study are to present a new concept of the bone anchorage using long implants in remote bone sites and to discuss four cases treated with this method. Our patients were treated with long implants with a distant anchorage in the skull bone. The planning procedure, the construction of the drill guide, and the surgical protocol are described. In the clinical cases described, all four patients were rehabilitated with the remote bone anchorage concept using long implants anchored in the skull base. Patients were followed for 5-12 years and the implants remained present and stable in these time periods. The skull base implant is a new concept of bone anchorage using long implants. It can be a solution for complicated clinical situations (often failed bone reconstructions and implant placements) or an alternative for bone grafting and maxillary augmentation procedures. There is effective implant retention in the skull base, an anatomical area that is often overlooked for implant placement.

In-situ formation of Ti-Mo biomaterials by selective laser melting of Ti/Mo and Ti/Mo_(2)C powder mixtures:A comparative study on microstructure,mechanical and wear performance,and thermal mechanisms

Ti-Mo alloys/composites are expected to be the next-generation implant material with low moduli but without toxic/allergic elements.However,synthesis mechanisms of the Ti-Mo biomaterials in Selective Laser Melting(SLM)vary according to raw materials and fundamentally influence material performance,due to inhomogeneous chemical compositions and stability.Therefore,this work provides a comparative study on microstructure,mechanical and wear performance,and underlying thermal mechanisms of two promising Ti-Mo biomaterials prepared by SLM but through different synthesis mechanisms to offer scientific understanding for creation of ideal metal implants.They are(i)Ti-7.5 Mo alloys,prepared from a conventional Ti/Mo powder mixture,and(ii)Ti-7.5 Mo-2.4 Ti C composites,in-situ prepared from Ti/Mo_(2)C powder mixture.Results reveal that the in-situ Ti-7.5 Mo-2.4 Ti C composites made from Ti/Mo_(2)C powder mixture by SLM can produce 61.4%moreβphase and extra Ti C precipitates(diameter below 229.6 nm)than the Ti-7.5 Mo alloys.The fine Ti C not only contributes to thinner and shorterβcolumnar grains under a large temperature gradient of 51.2 K/μm but also benefits material performance.The in-situ Ti-7.5 Mo-2.4 Ti C composites produce higher yield strength(980.1±29.8 MPa)and ultimate compressive strength(1561.4±39 MPa)than the Ti-7.5 Mo alloys,increasing by up to 12.1%.However,the fine Ti C with an aspect ratio of 2.71 dominates an unfavourable rise of elastic modulus to 91.9±2 GPa,44.7%higher than the Ti-7.5 Mo alloys,which,nevertheless,is still lower than the modulus of traditional Ti-6 Al-4 V.While,Ti C and its homogeneous distribution benefit wear resistance,decreasing the wear rate of the in-situ Ti-7.5 Mo-2.4 Ti C composites to 6.98×10^(-4)mm^3 N^(-1)m^(-1),which is 36%lower than that of the Ti-7.5 Mo alloys.Therefore,although with higher modulus than the Ti-7.5 Mo alloys,the SLM-fabricated in-situ Ti-7.5 Mo-2.4 Ti C composites can expect to provide good biomedical application potential in cases where combined good strength and wear resistance are required.

An automatic optimization method for minimizing supporting structures in additive manufacturing

The amount of supporting structure usage has been a major research topic in layer-based additive manufacturing(AM)over the past years as it leads to increased fabrication time and decreased surface quality.Previous studies focused on deformation and topology optimization to eliminate the number of support structures.However,during the actual fabrication process,the properties of shape and topology are essential.Therefore,they should not be modified casually.In this study,we present an optimizer that reduces the number of supporting structures by identifying the prime printing direction.Without rotation,models are projected in each direction in space,and the basis units involved in the generation of support structures are separated.Furthermore,the area of the supporting structures is calculated.Eventually,the prime printing direction with minimal supporting area is obtained through pattern-searching method.The results of the experiment demonstrated that the printing area was reduced by up to 60%for some cases,and the surface quality was also improved correspondingly.Furthermore,both the material consumption and fabrication time were decreased in most cases.In future work,additional factors will be considered,such as the height of the supporting S Xiao-Jun Chen xiaojunchen@sjtu.edu.cn 1 Institute of Biomedical Manufacturing and Life Quality Engineering,State Key Laboratory of Mechanical System and Vibration,School of Mechanical Engineering,Shanghai Jiao Tong University,Shanghai 200240,P.R.China 2 OMFS-IMPATH Research Group,Department of Imaging and Pathology,Faculty of Medicine,Katholieke Universiteit Leuven,Leuven,Belgium 3 Department of Oral and Maxillofacial Surgery,University Hospitals Leuven,Leuven,Belgium structures and the adhesion locations to improve the efficiency of this optimizer.

Neuropathic pain after bilateral sagittal split osteotomy:management and prevention

Neuropathic pain is characterized by spontaneous and provoked pain and other signs reflecting neural damage.Aberrant regeneration following peripheral nerve lesions leaves neurons unusually sensitive and prone to spontaneous pathological activity,abnormal excitability and heightened sensitivity to stimuli.This review covers the current understanding of neuropathic pain after bilateral sagittal split osteotomy(BSSO)of the lower jaw.The reported incidence of neuropathic pain after mandibular osteotomies is less than 1%,while the incidence in patients with iatrogenic inferior alveolar nerve(IAN)injuries during BSSO can be as high as 45%.The factors which modulate the healing process toward neuropathic pain during or after nerve damage have not yet been elucidated.Patients at highest risk for developing post-BSSO neuropathic pain are older than 45 years and have undergone procedures involving IAN compression,partial severance,or complete discontinuity of the lingual nerve with a proximal stump neuroma,patients with nerve injury repair delayed longer than 12 months and patients with chronic illnesses that compromise healing or increase risk for peripheral neuropathy.Although neuropathic pain tends to be long-lasting,some patients can recover completely.Preventive measures include risk assessment prior to surgery,prevention of nerve damage during surgery,and early repair of nerve injury.