Initial Stages Of Healing Research Articles

Microstructural analysis of flash-healed Vickers-indented microcracks near positive/negative electrodes on the (001) surface of cubic zirconia single crystals under direct current electric fields

Flash healing is a technique that uses power spikes to rapidly repair microcracks on ceramic surfaces. In this study, the microstructures of flash-healed Vickers-indented microcracks near the positive/negative electrodes under a DC electric field were examined by scanning transmission electron microscopy. The microstructural morphology near the positive electrode was almost identical to that of the microcracks located between both electrodes, as previously reported. However, a decrease in the degree of healing was observed near the negative electrode. This was attributed to the insufficient recovery of dislocations generated at the indentation state, which should have occurred in the initial stage of healing. The delay in dislocation recovery prevented contact between the inner surfaces of the microcracks and is possibly related to the increase in oxygen vacancies near the negative electrode.

Biocompatibility of mineral trioxide aggregate and biodentine as root-end filling materials: an in vivo study

This study evaluated the biocompatibility of mineral trioxide aggregate (MTA) and Biodentine (BD) as root-end filling materials. Six mongrel dogs were divided into two equal groups according to the evaluation period; group A: one month and group B: three months. Three premolars of the same quadrant in each arch were used, summing up 36 teeth (6 teeth/dog). These teeth were randomly subdivided into three subgroups according to the root-end filling material used: MTA, BD and no root-end filling material (control). Endodontic access cavities were performed for induction of periapical pathosis. After the infection period, root canal instrumentation and obturation were accomplished. One day after root canal procedures, root-end surgery was performed. Surgical access was achieved and the root-end was resected approximately 3 mm above the apex. Root-end cavity was prepared ultrasonically and filled with the tested materials. All samples were evaluated by radiography and histopathology (Inflammation and new hard tissue formation). Data were collected and subjected to statistical analysis. In group A, MTA subgroup exhibited significant higher mean inflammatory score than BD subgroup (P < 0.05) while no significant difference was recorded between MTA and BD subgroups in group B (P > 0.05). Regarding mean mineralization score, there was no significant difference between all subgroups in both groups A and B (P > 0.05). Biodentine exhibited favorable biocompatibility in the initial stage of healing than MTA and comparable biomineralization. Clinical relevance: Biodentine could be considered as an acceptable alternative to MTA in peri-radicular surgeries.

척추, 주요 관절 수술 후 초기 회복 과정에서 비침습적 치료인 도수치료, 냉각치료, 체외충격파 적용이 통증 및 관절 기능에 미치는 영향: 증례보고

Objective: Among various approaches to tissue healing after surgery, the degree of impact on pain reduction and changes in joint function was confirmed through the application of manual therapy, cryotherapy, and extracorporeal shock wave therapy to increase the level of physical activity performed in the early healing stage.&#x0D; Method: A person who received manual therapy, cooling therapy, and extracorporeal shock wave therapy after surgery on major spinal joints, and received intervention from immediately after surgery until discharge. Manual therapy, Cryo treatment, Extracorporeal shock wave therapy.&#x0D; Results: Through a case report, results were obtained that showed effectiveness in improving the range of motion of peripheral joints and reducing pain after surgery.&#x0D; Conclusion: It is believed that manual therapy, cryotherapy, and extracorporeal shock wave therapy, which are part of non-invasive treatment during the recovery process after spine and major joint surgery, will stabilize the initial healing stage and make physical activity levels more smooth in the future.

Advances of Blood Coagulation Factor XIII in Bone Healing.

The biologic process of bone healing is complicated, involving a variety of cells, cytokines, and growth factors. As a result of bone damage, the activation of a clotting cascade leads to hematoma with a high osteogenic potential in the initial stages of healing. A major factor involved in this course of events is clotting factor XIII (FXIII), which can regulate bone defect repair in different ways during various stages of healing. Autografts and allografts often have defects in clinical practice, making the development of advanced materials that support bone regeneration a critical requirement. Few studies, however, have examined the promotion of bone healing by FXIII in combination with biomaterials, in particular, its effect on blood coagulation and osteogenesis. Therefore, we mainly summarized the role of FXIII in promoting bone regeneration by regulating the extracellular matrix and type I collagen, bone-related cells, angiogenesis, and platelets, and described the research progress of FXIII = related biomaterials on osteogenesis. This review provides a reference for investigators to explore the mechanism by which FXIII promotes bone healing and the combination of FXIII with biomaterials to achieve targeted bone tissue repair.

The perspectives of a novel operative procedure for free gingival graft

Graft shrinkage, epithelial disintegration, and even necrosis are the well-known clinical complications during initial healing stage of free gingival graft (FGG) procedure. This article presented a novel operative prodecure for FGG in a dental implant with insufficient keratinized tissue over a 3-year follow-up period. Briefly, donor site for FGG harvested from maxillary tuberosity would minimize the volume of graft shrinkage. The new periosteum suture technique could secure FGG firmly adapted on the recipient site. With 1 mm gap between FGG and muco-gingival junction may improve plasmatic circulation and revascularization. The clinical findings of case report demonstrated that this novel operative procedure may provide a viable therapeutic alternative for FGG.

Self-healing of high-performance engineered cementitious materials with crystalline admixture in the seawater environment

The present paper studies the crack healing effect of high-performance cement-based materials mixed with crystalline admixture (CA) in seawater environments. Specifically, the healing effects of specimens with different initial crack widths in tap water and seawater environments were investigated through the seepage healing test (simulating a structure that a side contact with water and the other side contact with air). The variations of seepage velocity and water flow in the early 24 h of healing were mainly investigated. It was found that crystalline materials delay the healing of cracks in the initial stage of healing and this defect is more obvious under the seawater healing condition. Inductive Coupled Plasma (ICP) test was used to detect the variation of ion concentration in seawater; XRD, FTIR, and TG tests were carried out for characterizing the composition and relative content of healing products in the crack under the seawater and tap water healing conditions. Moreover, the effect of CA on the composition of healing products and the effect of crack width on healing products were quantified. The distribution characteristics of healing products along the crack depth under seawater seepage and seawater immersion healing conditions were then obtained.

Bone Morphogenetic Protein as Bone Additive around Dental Implant and its Impact on Osseointegration: a Systematic Review.

Bone morphogenetic protein (BMP), a potential osteoinductive agent, was systematically reviewed for merits and demerits when used as a bone additive that was intervened during the surgical phase of dental implant placement; and suitable drug carriers that could withstand the functional load and deliver BMP at its lowest concentration. To identify the carriers and concentration of BMP acceptable during surgical phase of implant placement and evaluate its efficacy in bone gain and osseointegration. The study design was systematic review. Literature search as per PICO format was carried out within a time range from 2000 to July 2021. The review fol-lowed PRISMA guidelines and registered with the PROSPERO (CRD42020171667). The focus question included the population with an intra-oral implant placed in both animal and human models that were intervened with BMP-2 as an external additive biomaterial during the surgical phase. 2631 articles selected from the initial search were systematically filtered and yielded 16 articles that were qualitatively analysed. The inter-rater reliability and level of agreement were 93.71%, κ(Kappa)>0.81 re-spectively. Results revealed the collagen carrier was commonly used for BMP delivery but lacked the property to withstand functional load and sustained release. BMP concentration varied in the range of 0.215μg to 0.8mg and the study revealed significantly indifferent out-come with low dose compared to the highest dose. BMP supplement showed better osseointe-gration in comparison with non-supplemented sites during the early period (within 6 months). BMP at lower concentrations and with appropriate carriers, collagen sponge, hydroxyapatite/tricalcium phosphate (HA/TCP) with a bio ceramic bulking agent, and poly (D, L-lactide-co-glycolic acid) (PLGA) reinforced with gelatin/HA/TCP accelerated bone growth during the initial stages of healing. Further long-term clinical trials for dental implant, analysing the sustained release of BMP with biodegradable and load-bearing carriers should be considered.

A timeseries analysis of the fracture callus extracellular matrix proteome during bone fracture healing.

While most bones fully self-heal, certain diseases require bone allograft to assist with fracture healing. Bone allografts offer promise as treatments for such fractures due to their osteogenic properties. However, current bone allografts made of decellularized bone extracellular matrix (ECM) have high failure rates, and thus grafts which improve fracture healing outcomes are needed. Understanding specific changes to the ECM proteome during normal fracture healing would enable the identification of key proteins that could be used enhance osteogenicity of bone allograft. Here, we performed a timeseries analysis of the fracture callus in mice to investigate proteomic and mineralization changes to the ECM at key stages of fracture healing. We found that changes to the ECM proteome largely coincide with the distinct phases of fracture healing. Basement membrane proteins (AGRN, COL4, LAMA), cartilage proteins (COL2A1, ACAN), and collagen crosslinking enzymes (LOXL, PLOD, ITIH) were initially upregulated, followed by bone specific proteoglycans and collagens (IBSP, COL1A1). Various tissue proteases (MMP2, 9, 13, 14; CTSK, CTSG, ELANE) were expressed at different levels throughout fracture healing. These changes coordinated with mineralization of the fracture callus, which increased steeply during the initial stages of healing. Interestingly the later timepoint was characterized by a response to wound healing and high expression of clotting factors (F2, 7, 9, 10). We identified ELANE and ITIH2 as tissue remodeling enzymes having no prior known involvement with fracture healing. This data can be further mined to identify regenerative proteins for enhanced bone graft design.

Novel Molecular-Level Insight into the Self-Healing Behavior and Mechanism of Polyurethane-Urea Elastomer Based on a Noncovalent Strategy

A larger number of studies successfully prepared various polymer materials with excellent self-healing properties, but the study on the underlying self-healing mechanism remains comparably backward and still unclear. In this study, we prepared a self-healing polyurethane-urea (PUU) elastomer based on noncovalent bonds. Then, a coarse-grained model of PUU was successfully constructed using the iteration Boltzmann inversion (IBI) method. Microphase separation and mechanical properties of PUU were reproduced using this model by coarse-grained molecular dynamics (MD) simulation. The three-stage healing mechanism comprised the following: (1) movement of the material to close the gap, (2) interdiffusion of the polymer, and (3) bond exchange. The mechanism was revealed by determining the effects of hard segment content on the microstructure (chain entanglement, interactions of soft and hard segments, chain motility) and healing capacity over healing time. In the initial stage of healing, the polymer chains were disentangled, and the degree of entanglement of the healed samples decreased. A novel experimental strategy confirmed the transition of hydrogen bonds from disorder to order during the healing process. The motility of the cut polymer chains (low molecular weight), especially the cut soft segment, and the disordered hydrogen bonds played a key role in the healing capacity. The increased content of the ordered hydrogen bonds led to the formation of a hard segment network, which was not conducive to healing. Finally, the promoting mechanism of external factors, such as heating and trace amount of solvent, on the healing of PUU was explained. Our work systematically and profoundly reveals the self-healing behavior and mechanism of microphase-separated PUU at the molecular level.

Evaluation of wound healing activity of topical nicotine in an excision wound model in rats

Background: Wound can be defined as disruption of cellular, anatomical, or functional continuity of living tissues. Nicotine causes damage to the epithelial layer of blood vessel and delays wound healing. It plays an important pathogenic role in impaired wound healing. Although in the last millennium, topical use of nicotine has been reported. It promotes collagen synthesis and, in turn, promotes wound healing. The role of topical nicotine on wound healing is controversial. Therefore, it was planned to evaluate and compare wound healing activity of various doses topical nicotine in rats. Aim and Objectives: The objectives of this study were to evaluate the effect of topical nicotine on wound healing in an excision wound model in rats. Materials and Methods: For evaluation of the wound healing effects of the nicotine, excision wound model was used. Nicotine was applied topically in a dose of 1.5 g%, 3.0 g%, and 6.0 g% petroleum base. Petroleum jelly served as control for topical nicotine. Dressing done by applying topical nicotine until (20 days) complete wound healing was observed. Parameters evaluated were surface area of wound and percentage closure. Results: Findings of this show that, on day 4, nicotine 3.0 g% and 6 g% the wound surface area were more as compared to control. On day 12, nicotine 6.0 g% showed significantly more wound surface area than control (P &lt; 0.05). Percentage wound contraction with topical nicotine (6.0 g%) was less as compared to control on day 4, 8, and 12 (P &lt; 0.001). On day 16, percentage wound contracture with topical nicotine (6.0 g%) contraction was significantly less as compared to control (P &lt; 0.05). Although percentage wound contraction with topical nicotine (all preparations) and control was similar on day 20. Conclusion: Finding shows that topical nicotine impairs wound healing in a dose related pattern during initial stages of healing in an excision wound model. However, there is no delay in wound healing with any dose of topical nicotine.

Effect of Dietary Amino Acids L-Arginine and Lysine on Implant Osseointegration.

Background:Low protein diets have been linked to decreased bone strength in humans. Arginine and lysine can help improve the healing process and stimulate growth factors.Aim:To evaluate if dietary arginine and lysine combination aids in reducing the time frame for osseo-integration process and bone formation in animal models.Materials and Methods:Controls (Group I) and Experimental (Group II) consisted of twelve New Zealand rabbits. Animals in the experimental group were fed a conventional pellet food, water, and the amino acids L-Lysine and L-Arginine (Biovea, USA), whereas those in the control group were offered a standard diet. In both groups of animals, titanium implants measuring 2.5mm* 6mm were implanted in each tibial osteotomy. At the end of two weeks, four weeks, and eight weeks, the animals were euthanized. The tibial bone was removed and preserved in 1% formalin. The samples were analysed histologically for presence or absence of Necrosis, presence or absence of clot formation, Vascularization, Fibroblast, Osteoblasts and Osteoid Bone growth.Results:Histological outcomes on vascularization, fibroblasts, osteoblasts, osteoid bone growth inferred no significant variation between the control and experimental groups after 8 weeks (P>.05).Conclusion:Vascularity, clot organisation, osteoblasts, fibroblasts, and osteoid bone production in the protein fed experimental group animals were better in initial stages of healing when compared to control groups.

Effects of the healing activity of rosemary-of-Chapada (Lippia gracilis Schauer) on cutaneous lesions in rats.

ABSTRACTPurpose:To evaluate the effects of rosemary leaf essential oil-based ointments on the healing of rat skin lesions.Methods:Sixty adult male rats, with dorsal excisional skin wounds made surgically under anesthesia, were divided into three groups (n = 20): Sham group (untreated wounds); control group (CG, wounds treated with vehicle); and essential oil (EO) treated group (wounds treated with essential oil-based ointments), administered topically once daily. Skin wounds were evaluated at 4, 7, 14, and 21 days after EO or vehicle treatments. Lesions were analyzed macroscopically for the contraction degree. Formalin-fixed paraffin-embedded sections of skin wounds were used for histopathological evaluation.Results:Macroscopic evaluation showed wounds edges with thin crust without firmness and yellowish color, along with an improvement in wound contraction in EO group when compared to the other groups. A reduced inflammatory reaction, along with newly formed small diameter capillaries and more organized and elongated collagen fibers, were more frequently observed in EO group than in the other groups. Moreover, blood vessel number and collagen fibers density were significantly higher in EO group.Conclusions:Skin lesion treatment with rosemary leaf essential oil-based ointments accelerates the initial stages of healing, reduces inflammation, and increases angiogenesis, collagen fibers density, and wound contraction in rats.

Successful management of gingival recession with interdental attachment loss using gingival unit grafts.

Background:Gingival recession leads to root surface exposure devoid of periodontal attachment. Recession defects with interdental attachment loss (RT2, RT3), further increase the avascular area which is critical for survival of soft-tissue grafts. Nonsubmerged grafts such as free gingival grafts and gingival unit grafts (GUGs) rely primarily on plasmatic circulation from the recipient area during the initial stages of healing for its survival.Methods:Nineteen isolated RT2 recession defects, in the mandibular anterior region, were treated using GUG. The clinical parameters of recession depth (RD), recession width (RW), interdental clinical attachment levels (iCAL) were measured at baseline. Percentage of mean root coverage (MRC) was calculated at 3 months and 6 months.Results:The percentage of mean root coverage (MRC) achieved at the end of 6 months was 81.79% ± 6.16%. Further, Simple linear regression analysis to predict MRC at 6 months using baseline RW revealed, for every 1 mm decrease in RW, the percentage of root coverage significantly increased by 5.25% (P = 0.04).Conclusion:GUG can be used as an alternative treatment modality to achieve successful root coverage in RT2 recession defects. Baseline RW can be used to predict the outcome of root coverage at the end of 6 months.

Role of TNF-α in early-stage fracture healing under normal and diabetic conditions

Background and objectiveInflammatory response plays a crucial role in the early stage of fracture healing. Immediately after fracture, the debris and immune cells (e.g., macrophages), recruited into the fracture callus, lead to the secretion of inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α), which governs the mesenchymal stem cells (MSCs) mediated healing processes. However, it is still unclear how chronic inflammatory diseases (e.g., diabetes) affect the level of TNF-α in fracture callus, ultimately the healing outcomes at the early stage of healing. Therefore, the purpose of this study is to develop a numerical model for investigating TNF-α mediated bone fracture healing. MethodsA mathematical model consisting of a system of partial differential equations that represent the reactive transport of cells and cytokines in the fracture callus is developed in this study. The model is first calibrated by using available experimental data and then implemented to study the effect of TNF-α on the early stage of fracture healing under normal and diabetic conditions. ResultsThere is a significant elevation of TNF-α level in facture callus during the first 24 h post-fracture in normal condition, and its influence in the concentration of MSCs and cell differentiation becomes significant three days post-fracture (e.g., the absence of TNF-α signaling could reduce the concentration of MSCs more than 20% in cortical callus). In addition, the excessive secretion of TNF-α induced by diabetes could decrease the concentration of MSCs at the initial stage of healing, particularly reduce the concentration of MSCs in cortical callus by around 25%. ConclusionThe model predictions suggested that there should be an optimal concentration of TNF-α in fracture callus, which enhances the early stage of healing, and excessive or insufficient secretion of TNF-α might significantly hinder the healing process.

Osseointegration around dental implants biofunctionalized with TGFβ-1 inhibitor peptides: an in vivo study in beagle dogs.

The aim of this study was to evaluate the effect of biofunctionalization with two TGF-β1 inhibitor peptides, P17 and P144, on osseointegration of CP-Ti dental implants. A total of 36 implants (VEGA, Klockner®) with 3.5 × 8 mm internal connection were used in this study, divided in three groups: (1) control group (n = 12), (2) implants which surfaces were biofunctionalized with P17 peptide inhibitor (n = 12), (3) implants with surfaces biofunctionalized by P144 peptide (n = 12). Three implants, one from each group, were inserted in both hemimandibles of 6 beagle dogs, 2 months after tooth extraction. Two animals were sacrificed at 2, 4 and 8 weeks post implant insertion, respectively. The samples were analyzed by Backscattering Scanning Electron Microscopy (BS-SEM) and histological analysis. Histomorphometric analysis of bone to implant contact (BIC), peri-implant bone fraction (BF) and interthread bone (IB) were carried out. Bone formation around implants measured by quantitative analysis, BS-SEM, was significantly higher in the P17-biofunctionalized implants, 4 and 8 weeks after the implantation. Histomorphometric analysis of BIC, BF and IB showed higher values in the P17-biofunctionalized group at initial stages of healing (2 weeks) and early osseointegration both at 4 and 8 weeks. For P144 biofunctionalized implants, the histomorphometric values obtained are also higher than control group. Accordingly, better results in the experimental groups were proven both by the quantitative and the qualitative analysis. Surface biofunctionalization with TGF-β1 inhibitor peptides, P17 and P144, resulted in better quantitative and qualitative parameters relative to implant osseointegration.

Dynamics of implant site preparation affecting the quality of osseointegrated implants in the maxillary aesthetic zone

PurposeThis study compared piezoelectric (PE) and conventional drills (CD) for maxillary aesthetic zone implant insertion. Material and methodsThis was a prospective split-mouth study. Implants were divided into two groups. Beds were prepared with CDs in group I and PE in group II. The implant stability quotient (ISQ) of the mechanical implant stability (MIS) was measured intraoperatively. The ISQ of the biological implant stability (BIS) was recorded at postoperative second and fourth months. Marginal bone loss (MBL) and bone density (BMD) were measured in the first and second years after prosthetic loading. The osteotomy time was also documented for both techniques. P values <0.05 were considered significant. ResultsSixty implants in 30 patients were included. PE provided a significantly higher ISQ. All values were above 70 throughout the follow-up period. The mean of the ISQ for MIS was 63.78 ± 1.03 and 73.89 ± 1.05 in group I and group II, respectively (p = 0.003). PE needed significantly longer osteotomy time with a mean of 11.99 ± 0.839 min. The BIS quality had high stability in group II and medium stability in group I throughout the study period. Its values decreased in both groups. Group II had a lesser percentage of decrease. However, it was significant only at time intervals between intraoperative and two months' postoperative (p = 0.004). MBL and BMD demonstrated insignificant results. ConclusionThe implant site preparation with PE devices should be preferred to CDs whenever possible, because they seem to enhance implant stability and osseointegration, especially at the initial stages of healing.

836 Custom Fabricated Open Anterior Ankle Foot Orthosis to Promote Early Mobility with Lower Extremity Grafts

Abstract Introduction Distal lower extremity STSG’s present a challenge with the balance of early mobility and immobilization of the ankle. Traditional commercially available ambulation boots or pre-fabricated orthotics may impose circumferential compression endangering graft integrity. Custom fabricated posterior AFO’s comprised of thermoplastic, scotch cast or fiberglass materials are not recommended for weight-bearing of the lower extremity during mobility/ambulation. What may also hinder promotion of early mobility is having a multitude of injuries or advanced age with decreased ability to adhere to a LE NWB status. An anterior approach to immobilization of the ankle was thought of to free the plantar surface of the foot for weight-bearing. The open concept of the orthosis itself minimizes direct contact with the involved LE graft. This promotes graft integrity during mobility with ankle immobilization. Methods Materials: Thermoplastic material, scissors, strapping, dense adhesive foam, adhesive Velcro and a heat gun. Fabrication: Measure the point of distance between where the desired proximal end of the orthosis would be to the patient’s metatarsal heads on the dorsal aspect of the foot; double it to calculate the amount of material needed. The width of the material should be approx. 3 to 4 inches. Warm material and tri-fold it together reducing width to approx. 1 ½ to 2 inches to increase stability. Shape the folded material into a continuous oval and place on the patient’s distal LE. As the material cools, shape the oval away from the medial/ lateral aspects of the distal LE restricting the points of contact to the anterior most proximal and distal aspect of the desired splint parameters. Remove once cooled and add dense adhesive foam to the 2 points of contact that will rest against the patient. This will allow for a slight area of “give” against the patient during weight-bearing of the LE/foot. Velcro and straps are added to the proximal/distal ends of the oval; heating the adhesive side will imbed the Velcro allowing increased durability with repeated donning/doffing. Results The open construction of this orthosis allows different degrees of weight-bearing eliminating contact with the distal LE STSG. The forefoot and heel are available to weight bear safely within the confines of the open anterior ankle foot orthosis. Conclusions Patients have been trialed with/without an AD with success in the achievement of ankle immobilization with mobility. Weight-bearing instructions that accompany this splint wear is foot placement rather than a normal heel strike cadence to avoid undue pressure at the proximal aspect of the splint on the lower extremity. Applicability of Research to Practice This splint has been successfully utilized for immobilization without compromise to STSG integrity due to the anterior open support it offers the ankle. Perhaps this concept could be applied to other joints to avoid direct contact of the splint with STSG during the initial stages of healing.

An alternative approach for vestibular extension using temporary coverage of epithelialized palatal grafts

An alternative approach was used to increase the buccal vestibular depth of two edentulous patients, using free epithelialized palatal grafts. Two edentulous patients presented with shallow vestibules and inadequate keratinized tissue width in the mandibular anterior region. These sites were treated with vestibuloplasty followed by placement of an epithelialized palatal graft. In order to minimize graft movement and possible mechanical trauma to the area, the graft was covered with the buccal flap during the initial stages of healing. The patients maintained an increase in the vestibular depth as well as the keratinized tissue width at 14 months and 5 years postoperatively. Successful outcomes in terms of increase in vestibular depth can be achieved with the use of epithelialized palatal graft that is covered during the initial stage of healing. The dental practitioner fabricating the complete denture should be aware of the advantages offered by this alternative surgical technique.

Adhesion of High Temperature Thermoplastic Composites

Thermoplastic composites offer new manufacturing prospects, thanks to the ability to melt the matrix. Welding, tape placement, 3D printing, overmoulding, or even stamping involve adhesion of the thermoplastic polymer at high temperature. One of the leading mechanism that enable to build up strength of adherent over the substrate is called healing. It is classically described as the diffusion of the macromolecular chains across the interface that enable bridging. In continuous processes, such as some which are used in advanced manufacturing of aerospace structures, cycle times are very short. Thus, it is unclear how suitable these materials are for fast continuous processes – the limiting factor being the time required to gain adhesion. To model and predict such processes, a controlled welding bench was designed enabling very short welding times (~5s). The mechanical adhesion between coupons was assessed by fracture of the welded interface via double cantilever beam fracture test. The welding kinetics were observed for the initial stages of healing with a behavior that should fit the t1/2trend. From this, it was possible to compare the accuracy and repeatability of interface healing at short time scales to that of samples which were closer to fully welded. Concurrently, the reptation of the polymer melt was assessed on a commercial rheometer, by computing relaxation time from the viscoelastic response. The correlation confirms that the mechanical quality is associated with the macromolecule diffusion. It was also observed that for high temperature thermoplastics, reticulation occurs, which inhibits molecular diffusion and increases the relaxation time. The major implication is that the preprocessing of the polymer will impact the subsequent adhesion step. For example, plates processed with an autoclave for a couple of hours would require a welding time an order of magnitude longer than the adhesion of a virgin prepreg in the tape placement process.

Computational modeling of human bone fracture healing affected by different conditions of initial healing stage

BackgroundBone healing process includes four phases: inflammatory response, soft callus formation, hard callus development, and remodeling. Mechanobiological models have been used to investigate the role of various mechanical and biological factors on bone healing. However, the effects of initial healing phase, which includes the inflammatory stage, the granulation tissue formation, and the initial callus formation during the first few days post-fracture, are generally neglected in such studies.MethodsIn this study, we developed a finite-element-based model to simulate different levels of diffusion coefficient for mesenchymal stem cell (MSC) migration, Young’s modulus of granulation tissue, callus thickness and interfragmentary gap size to understand the modulatory effects of these initial phase parameters on bone healing.ResultsThe results quantified how faster MSC migration, stiffer granulation tissue, thicker callus, and smaller interfragmentary gap enhanced healing to some extent. However, after a certain threshold, a state of saturation was reached for MSC migration rate, granulation tissue stiffness, and callus thickness. Therefore, a parametric study was performed to verify that the callus formed at the initial phase, in agreement with experimental observations, has an ideal range of geometry and material properties to have the most efficient healing time.ConclusionsFindings from this paper quantified the effects of the initial healing phase on healing outcome to better understand the biological and mechanobiological mechanisms and their utilization in the design and optimization of treatment strategies. It is also demonstrated through a simulation that for fractures, where bone segments are in close proximity, callus development is not required. This finding is consistent with the concepts of primary and secondary bone healing.