Development and characterization of 3D printed ethylene vinyl acetate (EVA) as drug delivery device for the treatment of overactive bladder.

The overactive bladder is a condition characterized by a sudden urge to urinate, even with small volumes of urine present in the bladder. The current treatments available for this pathology consist on conservative approaches and the continuous administration of drugs, which when made by conventional methods has limitations related to the first pass metabolism, bioavailability, severe side effects, and low patient adherence to treatments, ultimately leading to low effectiveness. Within this context, the present work proposes the design, manufacture, and characterization of an intravesical implant for the treatment of overactive bladder pathology, using EVA copolymer as a matrix and oxybutynin as a drug. The fabrication of devices through two manufacturing techniques (extrusion and additive manufacturing by fused filament fabrication, FFF) and the evaluation of the implants through characterization tests was proposed. The usability and functionality were evaluated through simulated insertion of the device/prototype in a bladder model through catheter insertion tests. The safety and effectiveness of the devices was investigated from mechanical testing as well as drug release assays. Drug release assays presented a burst release in the first 24 h, followed by a release of 1.8 and 2.8 mg/d, totalizing 32 d. Mechanical tests demonstrated an increase in the stiffness of the specimens due to the addition of the drug, showing a change in maximum stress and strain at break. The released dose was higher than that usually presented when considering the oral administration route, showing the optimization of the development of this implant has the potential to improve the quality of life of patients with overactive bladder.

Evaluation of safety and effectiveness of NAD in different clinical conditions: a systematic review.

Nicotinamide adenine dinucleotide (NAD+) is an essential pyridine nucleotide cofactor that is present in cells and in several important biological processes, including oxidative phosphorylation and production of adenosine triphosphate, DNA repair, calcium-dependent secondary messenger and gene expression. The purpose of this systematic review is to examine whether the coenzyme formulae NAD+ and NADH are safe and effective when acting as a supplement to humans. This systematic review of randomized clinical trials performed a search in six electronic databases: PubMed, MEDLINE (ovid), Embase, Cochrane CENTRAL (clinical trials), Web of Science, and Scopus. Secondary search included the databases (e.g., Clinical trials.gov, Rebec, Google Scholar - advance). Two reviewers assessed and extracted the studies independently. The risk of bias in studies was performed using version 2 of the Cochrane risk of bias tool for randomized trials. This review includes 10 studies, with a total of 489 participants. The studies included different clinical conditions, such as chronic fatigue syndrome (CFS), older adults, Parkinson's disease, overweight, postmenopausal prediabetes, and Alzheimer's disease. Based on studies, the supplementation with NADH and precursors was well tolerated and observed clinical results such as, a decrease in anxiety conditions and maximum heart rate was observed after a stress test, increased muscle insulin sensitivity, insulin signaling. Quality of life, fatigue intensity, and sleep quality among others were evaluated on patients with CFS. All studies showed some side effects, thus, the most common associated with NADs use are muscle pain, nervous disorders, fatigue, sleep disturbance, and headaches. All adverse events cataloged by the studies did not present a serious risk to the health of the participants. Overall, these findings support that the oral administration of NADH can be associated to an increase in general quality of life and improvement on health parameters (e.g., a decrease in anxiety, maximum heart rate, inflammatory cytokines in serum, and cerebrospinal fluid). NADH supplementation is safe and has a low incidence of side effects. Future investigations are needed to evidence the clinical benefits regarding specific diseases and doses administered.

Continuous Vertical Inside-Out Versus Traditional Vertical Inside-Out Meniscal Repair: A Biomechanical Comparison.

Background: Biomechanical assessment of meniscal repairs is essential for evaluating different meniscal suturing methods and techniques. The continuous meniscal suture technique is a newer method of meniscal repair that may have biomechanical differences compared with traditional techniques. Purpose: To evaluate the displacement, stiffness after cyclical loading, and load to failure for a continuous vertical inside-out meniscal suture versus a traditional vertical inside-out meniscal suture in a porcine medial meniscus. Study Design: Controlled laboratory study. Methods: A total of 28 porcine knees were acquired and divided into 2 test groups of 14 medial meniscus each. A 2.0-cm longitudinal red-white zone cut was made in the body of the medial meniscus for each knee. The continuous suture (CS) group received 4 vertical stitches performed with a continuous vertical meniscal suture technique, and the inside-out suture (IO) group received a traditional vertical suture with 4 stitches. Two traction tapes were passed between the sutures and positioned in the biomechanical testing fixture device. Each specimen underwent load-to-failure testing at 5 mm/s, and displacement, system stiffness, and maximum load to failure were compared between the groups. Results: The displacement after the cyclic test was 0.53 ± 0.12 and 0.48 ± 0.07 mm for the CS and IO groups, respectively. There was no significant difference between the groups (P = .2792). The stiffness at the ultimate load testing was 36.3 ± 1.9 and 35.3 ± 2.4 N/mm for groups CS and IO, respectively, with no significant difference between the groups (P = .2557). In the load-to-failure test, the ultimate load was 218.2 ± 63.9 and 238.3 ± 71.3 N in the CS and IO groups, respectively, with no significant group differences (P = .3062). Conclusion: A continuous vertical meniscal suture created a configuration for treating longitudinal meniscal lesions that was beneficial and biomechanically similar to a traditional vertical suture technique. Clinical Relevance: The study findings indicate that use of the continuous vertical inside-out meniscal suture technique is a possible therapeutic option.

Evaluation of safety and effectiveness of gestrinone in the treatment of endometriosis: a systematic review and meta-analysis.

PURPOSE: Endometriosis is a common chronic gynecological disease defined as the presence of endometrial glands and stroma tissue outside the uterus. Gestrinone is an effective antiestrogen that induces endometrial atrophy and/or amenorrhea. The purpose of this systematic review is to provide an evaluation of safety and effectiveness of gestrinone for the treatment of endometriosis. METHODS: We performed a search in six electronic databases: PubMed, MEDLINE (ovid), Embase, Cochrane CENTRAL (clinical trials), Web of Science and Scopus. Our selected primary outcomes were the changes in dysmenorrhea, pain relief including pelvic pain and dyspareunia. The secondary outcomes embrace hormones parameters, pregnancy rate and adverse events. RESULTS: Of 3269 references screened, 16 studies were included involving 1286 women. All studies compared gestrinone with other drugs treatments (placebo, Danazol, Mifepristone tablets, Leuprolide acetate, Quyu Jiedu Recipe) during 6 months. When compared with other drugs treatments, gestrinone relieved dysmenorrhea, pelvic pain, and morphologic response in the ovary. There was an increase on the pregnancy rate. Regarding the side effects observed, gestrinone showed the same adverse events and increased the risk of acne and seborrhea when compared to other treatments. Even if there was any difference in efficacy between gestrinone, danazol, leuprolide acetate, or Quyu Jiedu Recipe Chinese Medicine, it remains unclear due to insufficient data. CONCLUSION: Based limited evidence available suggests that gestrinone appeared to be safe and may have some efficacy advantages over danazol, as well as other therapeutic interventions for treating endometriosis. However, this conclusion should be interpreted with caution, due the quality of the evidence provided is generally very low or unclear. TRIAL REGISTRATION: CRD42021284148.

Pre-clinical evaluation of fretting-corrosion at stem-head and stem-cement interfaces of hip implants using in vitro and in silico models.

Prior to clinical use, the corrosion resistance of new prosthesis system must be verified. The fretting-corrosion mechanisms of total hip arthroplasty (THA) implants generate metal debris and ions that can increase the incidence of adverse tissue reactions. For cemented stems, there are at least two interfaces that can be damaged by fretting-corrosion: stem-head and stem-cement. This investigation aimed to evaluate, through in vitro and in silico analyses, fretting-corrosion at the stem-head and stem-cement interfaces, to determine which surface is most affected in pre-clinical testing and identify the causes associated with the observed behavior. Unimodular stems and femoral heads of three different groups were evaluated, defined according to the head/stem material as group I (SS/SS), group II (CoCr/SS), and group III (CoCr/CoCr). Seven pairs of stems and heads per group were tested: three pairs were subjected to material characterization, three pairs to in vitro fretting-corrosion testing, and one pair to geometric modeling in the in silico analysis. The absolute area of the stem body degraded was more than three times higher compared with the trunnion, for all groups. These results were corroborated by the in silico analysis results, which revealed that the average micromotion at the stem-cement interface (9.65-15.66 µm) was higher than that at the stem-head interface (0.55-1.08 µm). In conclusion, the degradation of the stem-cement interface is predominant in the pre-clinical set, indicating the need to consider the fretting-corrosion at the stem-cement interface during pre-clinical implant evaluations.

Influence of acupuncture needle physical-chemical properties on needling quality.

OBJECTIVES: This study analyzed the physical-chemical properties of three different brands of acupuncture needle, classified by acupuncturists as high (A), medium (B) and low (C) quality. METHODS: Experienced acupuncturists, rated, in terms of perceived needling quality, three acupuncture needle brands as high (A), medium (B) and low (C) quality. Next, scanning electron microscopy (SEM) images of the tip and surface finish of the needles of each brand were analyzed. A mechanical test was developed and performed to evaluate the compressive force required to insert the needles through a smooth surface (silicon). In addition, X-ray fluorescence spectroscopy (XRF) and dispersive energy spectroscopy (DES) were conducted to analyze the material composition of the needles and presence of oxidation. RESULTS: SEM images revealed that needle brands A and B presented a sharper tip and a more regular surface finish in comparison to brand C. In the insertion test, needle brands A and B had similar performance characteristics, with A requiring less force to penetrate the silicon device when compared to B, while C failed to penetrate the silicon and complete the test. The XRF analysis did not reveal any differences in material composition between the three brands. However, brand C exhibited particles embedded on the needle surface and DES confirmed oxidation. CONCLUSION: This study demonstrates that perceived needling quality by acupuncturists can be correlated with physical-chemical properties of the needles, especially those related to finishing quality of the tip and the surface of the needles.

In vitro mechanical evaluation of spinal fixation rod connectors / Avaliação mecânica in vitro de conectores das hastes de fixação vertebral / Evaluación mecánica in vitro de conectores de varillas de fijación de la columna

ABSTRACT Objective Evaluate and compare the mechanical resistance and the fatigue behavior associated with the use of three different modalities of vertebral fixation system rod connectors through in vitro pre-clinical mechanical tests developed specifically for this application (linear, lateral with square connector and lateral with oblique connector). Methods Cobalt chromium rods 5.5 mm in diameter were used and coupled with three types of connectors: a) side rod with oblique connector, b) side rod with square connector, and c) rod and linear connectors. Quasi-static mechanical four-point bending and fatigue tests were performed. The variables measured were (I) the bending moment at the yield limit, (II) the displacement at the yield limit, (III) the rigidity of the system in flexion and (IV) the number of cycles until system failure. Results The linear system presented the greatest force and the greatest moment at the yield limit, as well as the greatest stiffness equivalent to bending. All specimens with square and oblique connectors endured 2.5 million cycles in the minimum and maximum conditions of applied moment. The specimens with linear connector endured 2.5 million cycles with fractions of 40.14% of the bending moment at the yield limit, but failed with levels of 60.17% and 80.27%. Conclusions Systems with linear connectors showed greater mechanical resistance when compared to systems with square and oblique connectors. All systems supported cyclic loads that mimic in vivo demands. Level of evidence V; In vitro research.

RESUMO Objetivo Avaliar e comparar a resistência mecânica e o comportamento em fadiga associados ao uso de três modalidades distintas de conectores de hastes do sistema de fixação vertebral por meio de ensaios mecânicos pré-clínicos in vitro desenvolvidos especificamente para essa aplicação (linear, lateral com conector quadrado e lateral com conector oblíquo). Métodos Foram usadas hastes de Cromo-cobalto de 5,5 mm de diâmetro acopladas a três modalidades de conectores: a) haste lateral com conector oblíquo, b) haste lateral com conector quadrado e c) haste e conector lineares. Foram realizados ensaios mecânicos quase-estáticos e de fadiga sob flexão em quatro pontos. As variáveis medidas foram (I) o momento fletor no limite de escoamento, (II) o deslocamento no limite de escoamento e (III) a rigidez do sistema em flexão e (IV) número de ciclos até a falha do sistema. Resultados O sistema linear apresentou a maior força e o maior momento no limite de escoamento, bem como maior rigidez equivalente à flexão. Todos os corpos de prova com conectores quadrados e oblíquos suportaram 2,5 milhões de ciclos nas condições mínimas e máximas de momento aplicado. Os corpos de prova com conector linear suportaram 2,5 milhões de ciclos com frações de 40,14% do momento fletor no limite do escoamento, porém falharam com níveis de 60,17% e 80,27%. Conclusões Os sistemas com conectores lineares apresentaram maior resistência mecânica quando comparados aos sistemas com conectores quadrados e oblíquos. Todos os sistemas suportaram carregamentos cíclicos que mimetizam as solicitações in vivo. Nível de evidencia V; Pesquisa in vitro.

RESUMEN Objetivo Evaluar y comparar la resistencia mecánica y el comportamiento de fatiga asociado al uso de tres modalidades distintas de conectores de varilla del sistema de fijación vertebral a través de ensayos mecánicos preclínicos in vitro desarrollados específicamente para esta aplicación (lineal, lateral con conector cuadrado y lateral con conector oblicuo). Métodos Se utilizaron varillas de cromo-cobalto de 5,5 mm de diámetro acopladas a tres tipos de conectores: a) varilla lateral con conector oblicuo, b) varilla lateral con conector cuadrado y c) varilla y conector lineales. Se realizaron ensayos mecánicos y de fatiga cuasi-estáticos y ensayos por flexión de cuatro puntos. Las variables medidas fueron (I) el momento flector en el límite elástico, (II) el desplazamiento en el límite elástico y (III) la rigidez del sistema en flexión y (IV) el número de ciclos hasta la falla del sistema. Resultados El sistema lineal presentó la mayor fuerza y el mayor momento en el límite elástico, así como la mayor rigidez equivalente a la flexión. Todas las probetas con conectores cuadrados y oblicuos soportaron 2,5 millones de ciclos en las condiciones mínimas y máximas de momento aplicado. Las probetas con conector lineal soportaron 2,5 millones de ciclos con fracciones del 40,14% del momento flector en el límite elástico, pero fallaron con niveles de 60,17% y 80,27%. Conclusiones Los sistemas con conectores lineales mostraron mayor resistencia mecánica en comparación con los sistemas con conectores cuadrados y oblicuos. Todos los sistemas admitían cargas cíclicas que imitan las solicitudes in vivo. Nivel de Evidencia V; Investigación in vitro.

Tendon grafts with preserved muscle demonstrate similar biomechanical properties to tendon grafts stripped of muscular attachments: a biomechanical evaluation in a porcine model.

PURPOSE: (1) To evaluate the biomechanical properties of a porcine flexor digitorum superficialis tendon graft with preserved muscle fibers and (2) to compare these results with the biomechanical properties of a porcine tendon graft after removal of associated muscle. METHODS: Eighty-two porcine forelegs were dissected and the flexor digitorum superficialis muscle tendons were harvested. The study comprised of two groups: Group 1 (G1), harvested tendon with preserved muscle tissue; and Group 2 (G2), harvested contralateral tendon with removal of all muscle tissue. Tests in both groups were conducted using an electro-mechanical material testing machine (Instron, model 23-5S, Instron Corp., Canton, MA, USA) with a 500 N force transducer. Yield load, stiffness, and maximum load were evaluated and compared between groups. RESULTS: The behavior of the autografts during the tests followed the same stretching, deformation, and failure patterns as those observed in human autografts subjected to axial strain. There were no significant differences in the comparison between groups for ultimate load to failure (p = 0.105), stiffness (p = 0.097), and energy (p = 0.761). CONCLUSION: In this porcine model biomechanical study, using autograft tendon with preserved muscle showed no statistically significant differences for yield load, stiffness, or maximum load compared to autograft tendon without preserved muscle. The preservation of muscle on the autograft tendon did not compromise the mechanical properties of the autograft. LEVEL OF EVIDENCE: Level III Controlled laboratory study.

Polymeric implants with drug-releasing capabilities: a mapping review of laboratory research.

PURPOSE: To provide a systematic map of the nature and extent of preclinical research concerning drug-releasing polymeric implants. SIGNIFICANCE: By summarizing available data, this mapping review can guide the development of new drug-delivery devices. METHODS: In-vitro studies assessing drug-delivery implants were reviewed. A study protocol was registered at Open Science Framework. The association of polymers with prominent drugs, manufacturing processes, geometries, treatments, and anatomical locations was assessed using the VOSviewer software. The release periods were also evaluated. RESULTS: A total of 423 articles, published between 1975 and 2020, were included and grouped into a framework with nine main categories. More than half of studies were published between 2010 and 2020. Among 201 individual polymers or combinations, the most investigated were PLGA, PCL, PLA, Silicone (SIL), EVA, and PU. Similarly, from 232 individual drugs or combinations, the most prominent were dexamethasone (DEX; anti-inflammatory), paclitaxel (PTX; anticancer), fluoruracil (anticancer), ciprofloxacin (CFX) hydrochloride (antibiotic), and gentamicin (GS; antibiotic). A total of 51 manufacturing processes were encountered, of which the most reported were solvent evaporation, compression molding (CM), extrusion (EX), electrospinning (ELS), and melt molding (MM). Among 38 implant geometries, cylinder (CIL) was the most prominent, followed by disk, square film, circular film (FCIR), and undefined film. Release times varied greatly, although the majority of articles ranged between 5 and 300 d. CONCLUSIONS: Drug-delivery implants were highly heterogeneous due to its applicability for multiple health conditions. Most implants were made of PLGA and most drugs assessed presented anti-inflammatory, antibiotic, or anticancer effects. Solvent evaporation and CIL were the most prominent manufacturing process and geometry, respectively.

Comparative Biomechanical Study of Crosslinked Polyethylene Wear with 36-mm Ceramic Femoral Heads and with 32-mm Metal Femoral Heads.

Objective This study aims to compare the in vitro wear rate of crosslinked, high molecular weight polyethylene coupled to 36-mm diameter ceramic heads and 32-mm diameter metal heads. Methods Ceramic-on-polyethylene (36 mm) and metal-on-polyethylene (32 mm) tribological pairs were submitted to biomechanical tests in a simulator to determine the wear rate after 15 × 10 6 cycles. Results A statistically significant difference ( p = 0.0005) was detected when comparing the wear rate of assemblies with metallic heads (average wear: 14.12 mg/MC) and ceramic heads (average wear: 7.46 mg/MC). Conclusion The present study demonstrated the lower wear rate in prosthetic assemblies using 36-mm crosslinked ceramic-on-polyethylene tribological pairs compared to 32-mm crosslinked metal-on-polyethylene assemblies. This finding demonstrates the effectiveness of ceramic-on-polyethylene tribological pairs, even with large diameter heads.

Comparative Biomechanical Study of Crosslinked Polyethylene Wear with 36-mm Ceramic Femoral Heads and with 32-mm Metal Femoral Heads / Estudo biomecânico comparativo do desgaste do polietileno reticulado com cabeças femorais cerâmicas de 36 mm e com cabeças metálicas de 32 mm

Abstract Objective This study aims to compare the in vitro wear rate of crosslinked, high molecular weight polyethylene coupled to 36-mm diameter ceramic heads and 32-mm diameter metal heads. Methods Ceramic-on-polyethylene (36 mm) and metal-on-polyethylene (32 mm) tribological pairs were submitted to biomechanical tests in a simulator to determine the wear rate after 15 × 106 cycles. Results A statistically significant difference (p= 0.0005) was detected when comparing the wear rate of assemblies with metallic heads (average wear: 14.12 mg/MC) and ceramic heads (average wear: 7.46 mg/MC). Conclusion The present study demonstrated the lower wear rate in prosthetic assemblies using 36-mm crosslinked ceramic-on-polyethylene tribological pairs compared to 32-mm crosslinked metal-on-polyethylene assemblies. This finding demonstrates the effectiveness of ceramic-on-polyethylene tribological pairs, even with large diameter heads.

Resumo Objetivo: O objetivo do presente estudo foi comparar, in vitro, a taxa de desgaste do polietileno de alto peso molecular reticulado acoplado a cabeças cerâmicas de 36 mm de diâmetro e acoplado a cabeças metálicas de 32 mm de diâmetro. Métodos: Foram realizados ensaios biomecânicos em simulador de desgaste para os pares tribológicos cerâmica-poli (36 mm) e metal-poli (32 mm) a fim de verificar a taxa de desgaste após em 15 × 106 ciclos. Resultados: Na comparação entre as medidas de taxa de desgaste dos conjuntos com cabeças metálicas (média:14,12 mg/MC) e cerâmicas (média:7,46 mg/MC) houve diferença estatitsticamente significativa (p= 0,0005). Conclusão: O presente estudo demonstrou menor taxa de desgaste em conjuntos protéticos que utilizaram o par tribológico cerâmica-polietileno reticulado de 36 mm em comparação aos conjuntos com metal-polietileno reticulado de 32 mm. Tal achado demonstra a eficácia do par tribológico cerâmica-poli, mesmo com a utilização de cabeças de grande diâmetro.

Numerical study on the effect of stent shape on suture forces in stent-grafts.

Second-generation stent-grafts (SGs) have addressed many of the mechanical problems reported for first-generation endoprostheses, such as graft tear and stent rupture; however, suture wear and detachment due to pulsatile fatigue remains an issue. Numerical studies on the mechanical behavior of these endoprostheses usually model the attachment between stents and graft as a continuous ''tie'' constraint, which does not provide information on the mechanical loads acting on individual sutures. This paper presents a suitable approach for Finite Element (FE) simulations of SGs which allows for a qualitative evaluation of the loads acting on sutures. Attachment between stents and graft is modeled as rigid beams at discrete locations of the endoprostheses, and the reaction forces on the beams are analyzed. This modeling strategy is employed for four different SG models (two Z-stented commercial models and two circular-stented models) subjected to a severe 180° U-bend, followed by intraluminal pressurization. Results show that, for all models, the majority of sutures is experiencing fluctuating forces within a cardiac cycle (between 80 and 120 mmHg), which points to pulsatile fatigue as potential failure mode. In addition, the highest loads are concentrated in kinks and, for Z-stented models, at the apexes of stents. Moreover, suture loads for circular-stented models are lower than for Z-stented models, indicating better resistance to suture detachment. All these observations are in line with experimental results published in the literature, and, therefore, the procedure herein proposed may serve as a valuable tool in the development of new SG models with better suture resistance to pulsatile wear and fatigue.

An experimental and numerical study on the transverse deformations in tensile test of tendons.

The transverse deformations of tendons assessed in tensile tests seems to constitute a controversial issue in literature. On the one hand, large positive variations of the Poisson's ratio have been reported, indicating volume reduction under tensile states. On the other hand, negative values were also observed, pointing out an auxetic material response. Based on these experimental observations, the following question is raised: Are these large and discrepant transverse deformations intrinsically related to the constitutive response of tendons or they result from artifacts of the mechanical test setup? In order to provide further insights to this question, an experimental and numerical study on the transverse kinematics of tendons was carried out. Tensile experiments were performed in branches of deep digital flexor tendons of domestic porcine, where the transverse displacements were measured by two high-speed, high-accuracy optical digital micrometers placed transversely to one another. Aiming at a better understanding of the effects of the mechanical test setup in the transverse measurements, a three-dimensional finite element model is proposed to resemble the tensile experiment. The main achieved results strongly support the following hypotheses regarding tensile tests of tendons: the clamping region considerably affects the kinematics of the specimen even at a large distance from the clamps; the transverse deformations are mainly ruled by stiff fibers embedded in a soft matrix; the generalization of the Poisson's ratio to draw conclusions about changes in volume of tendons may lead to misinterpretations.

Thermomechanical and in vitro biological characterization of injection-molded PLGA craniofacial plates.

PURPOSE:: To evaluate the thermomechanical and in vitro biological response of poly(lactic-co-glycolic acid) (PLGA) plates for craniofacial reconstructive surgery. METHODS:: PLGA 85/15 craniofacial plates were produced by injection molding by testing two different temperatures (i.e., 240°C, PLGA_lowT, and 280°C, PLGA_highT). The mechanical properties of the produced plates were characterized by three-point bending tests, dynamic mechanical analysis, and residual stress. Crystallinity and thermal transitions were investigated by differential scanning calorimetry. Finally, in vitro cell interaction was evaluated by using SAOS-2 as cell model. Indirect cytotoxicity tests (ISO 10-993) were performed to prove the absence of cytotoxic release. Cells were then directly seeded on the plates and their viability, morphology, and functionality (ALP) checked up to 21 days of culture. RESULTS:: A similar performance of PLGA_lowT and PLGA_highT plates was verified in the three-point bending test and dynamic mechanical analyses. Also, the two processing temperatures did not influence the in vitro cell interaction. Cytotoxicity and ALP activity were similar for the PLGA plates and control. Cell results demonstrated that the PLGA plates supported cell attachment and proliferation. Furthermore, energy-dispersive X-ray spectroscopy revealed the presence of sub-micron particles, which were identified as inorganic mineral deposits resulting from osteoblast activity. CONCLUSION:: The present work demonstrated that the selected processing temperatures did not affect the material performance. PLGA plates showed good mechanical properties for application in craniofacial reconstructive surgery and adequate biological properties.

Effect of Injection Molding Melt Temperatures on PLGA Craniofacial Plate Properties during In Vitro Degradation.

The purpose of this article is to present mechanical and physicochemical properties during in vitro degradation of PLGA material as craniofacial plates based on different values of injection molded temperatures. Injection molded plates were submitted to in vitro degradation in a thermostat bath at 37 ± 1°C by 16 weeks. The material was removed after 15, 30, 60, and 120 days; then bending stiffness, crystallinity, molecular weights, and viscoelasticity were studied. A significant decrease of molecular weight and mechanical properties over time and a difference in FT-IR after 60 days showed faster degradation of the material in the geometry studied. DSC analysis confirmed that the crystallization occurred, especially in higher melt temperature condition. DMA analysis suggests a greater contribution of the viscous component of higher temperature than lower temperature in thermomechanical behavior. The results suggest that physical-mechanical properties of PLGA plates among degradation differ per injection molding temperatures.

Influence of Processing Conditions on the Mechanical Behavior and Morphology of Injection Molded Poly(lactic-co-glycolic acid) 85:15.

Two groups of PLGA specimens with different geometries (notched and unnotched) were injection molded under two melting temperatures and flow rates. The mechanical properties, morphology at the fracture surface, and residual stresses were evaluated for both processing conditions. The morphology of the fractured surfaces for both specimens showed brittle and smooth fracture features for the majority of the specimens. Fracture images of the notched specimens suggest that the surface failure mechanisms are different from the core failure. Polarized light techniques indicated birefringence in all specimens, especially those molded with lower temperature, which suggests residual stress due to rapid solidification. DSC analysis confirmed the existence of residual stress in all PLGA specimens. The specimens molded using the lower injection temperature and the low flow rate presented lower loss tangent values according to the DMA and higher residual stress as shown by DSC, and the photoelastic analysis showed extensive birefringence.

An experimental methodology for arterial walls / Análise experimental de paredes arteriais

Numerical simulations of arterial walls allow a better understanding of the interaction between biological tissue and endoprosthesis (stents), which are used in aneurysms or atherosclerosis stenosis treatment. A reliable understanding of this interaction may help one to select, or even design, the best structure for a given clinical indication. The development of a realistic numerical simulation requires an appropriated definition of a constitutive model and the obtainment of experimental data useful to a parameter identification procedure. Biological tissues have different mechanical characteristics of materials commonly used for engineering applications, however the experimental data acquisition is a major challenge. Some examples of technical difficulties of experimental test in biological tissue are associated to the obtainment of samples, temperature and humidity control during storage, suitable gripping and geometric and strain measurements methods. Therefore, this paper presents an experimental methodology to perform uniaxial mechanical tests in pig arteries in order to provide useful information for material models of arterial walls. This study proposes the experimental procedure from the sample obtainment to the uniaxial experimental testing of the tissue in two directions (circumferential and longitudinal) at two strain rates. In order to shown the use of the experimental data into a suitable numerical model for arterial walls, a parameter identification procedure was performed to obtain material parameters of a viscoelastic anisotropic model with fiber dispersion for finite strains. Through the experimental methodology proposed it was possible to obtain useful data for the parameter identification. Moreover, the results demonstrate that the arterial walls mechanical behavior was properly represented by the selected model.

Simulações numéricas de paredes arteriais permitem um melhor entendimento da interação entre tecido biológico e endopróteses (stents), os quais são utilizados no tratamento de aneurismas e lesões obstrutivas ateroscleróticas. O melhor entendimento desta interação pode auxiliar na seleção do modelo ou no projeto da estrutura da endoprótese mais adequada para uma dada indicação clínica. A realização de simulações numéricas realísticas requer a definição apropriada de um modelo constitutivo e a obtenção de dados experimentais adequados para um procedimento de identificação de parâmetros. Diferentemente dos materiais usados comumente em engenharia, a aquisição de dados experimentais de tecidos biológicos representa um grande desafio. Alguns exemplos das dificuldades técnicas associadas aos testes experimentais de tecidos biológicos estão na obtenção de amostras, no controle de temperatura e humidade durante o armazenamento, na fixação adequada e na medição geométrica e de deformações. Portanto, o presente artigo apresenta uma metodologia experimental para realização de testes uniaxiais em artérias suínas, visando fornecer informações adequadas para modelos materiais de paredes arteriais. Este estudo propõe um procedimento experimental que abrange desde a obtenção da amostra até o ensaio uniaxial do tecido em duas direções (circunferencial e longitudinal), com duas taxas de velocidades. Para exemplificar o uso dos dados experimentais em um modelo numérico adequado para paredes arteriais, um procedimento de identificação de parâmetros foi realizado, obtendo parâmetros materiais de um modelo viscoelástico anisotrópico com dispersão de fibras para deformações finitas. Através da metodologia experimental proposta foi possível obter dados úteis para identificação de parâmetros. Além disso, os resultados demonstraram que o comportamento mecânico de paredes arteriais foi representado adequadamente pelo modelo selecionado.

In Vitro Fatigue Resistance of Teeth Restored With Bulk Fill versus Conventional Composite Resin.

The aim of this study was to compare the fatigue resistance of restored teeth with bulk fill composite resin, conventional composite resin with incremental insertion and unprepared sound teeth. Twenty-eight extracted maxillary premolars were selected and divided into 4 groups based on composite resin and insertion technique: control (C), conventional composite resin with incremental insertion (I) and bulk fill composite resin with three (BF3) or single increment (BF1). The restored specimens were submitted to fatigue resistance test with a 5 Hz frequency. An initial application of 5,000 sinusoidal load cycles with a minimum force of 50 N and a maximum force of 200 N was used. Next, were applied stages of 30,000 load cycles with the maximum force increasing gradually: 400, 600, 800, 1000, 1200 and 1400 N. The test was concluded when 185,000 load cycles were achieved or the specimen failed. The fatigue resistance data were recorded for comparison, using the Kaplan-Meier survival curve and analyzed by log-rank test at 0.05 significance. Fractures were classified based on the position of the failure - above or below the cementoenamel junction (CEJ). Statistical analysis of the Kaplan-Meier survival curve and log-rank test showed a significant difference between groups (p=0.001). The fracture analysis demonstrated that only 28.58% of failures were below the CEJ in group C, while for groups I, BF1 and BF3 they were 42.85%, 85.71% and 85.71%, respectively. Teeth restored with composite bulk fill in both techniques present similar fatigue resistance values compared with those restored with a conventional incremental insertion of composite, while the fatigue strength values of unprepared sound teeth were higher. Furthermore, unprepared sound teeth showed a lower percentage of fractures below the CEJ.

In Vitro Fatigue Resistance of Teeth Restored With Bulk Fill versus Conventional Composite Resin

Abstract The aim of this study was to compare the fatigue resistance of restored teeth with bulk fill composite resin, conventional composite resin with incremental insertion and unprepared sound teeth. Twenty-eight extracted maxillary premolars were selected and divided into 4 groups based on composite resin and insertion technique: control (C), conventional composite resin with incremental insertion (I) and bulk fill composite resin with three (BF3) or single increment (BF1). The restored specimens were submitted to fatigue resistance test with a 5 Hz frequency. An initial application of 5,000 sinusoidal load cycles with a minimum force of 50 N and a maximum force of 200 N was used. Next, were applied stages of 30,000 load cycles with the maximum force increasing gradually: 400, 600, 800, 1000, 1200 and 1400 N. The test was concluded when 185,000 load cycles were achieved or the specimen failed. The fatigue resistance data were recorded for comparison, using the Kaplan-Meier survival curve and analyzed by log-rank test at 0.05 significance. Fractures were classified based on the position of the failure - above or below the cementoenamel junction (CEJ). Statistical analysis of the Kaplan-Meier survival curve and log-rank test showed a significant difference between groups (p=0.001). The fracture analysis demonstrated that only 28.58% of failures were below the CEJ in group C, while for groups I, BF1 and BF3 they were 42.85%, 85.71% and 85.71%, respectively. Teeth restored with composite bulk fill in both techniques present similar fatigue resistance values compared with those restored with a conventional incremental insertion of composite, while the fatigue strength values of unprepared sound teeth were higher. Furthermore, unprepared sound teeth showed a lower percentage of fractures below the CEJ.

Resumo O objetivo deste estudo foi comparar a resistência à fadiga de dentes restaurados com uma resina composta bulk fill, resina composta convencional de inserção incremental e dentes hígidos sem preparo. Vinte e oito pré-molares maxilares extraídos foram selecionados e divididos em quatro grupos conforme a resina composta e técnica de inserção: controle (C), resina composta convencional com inserção incremental (I) e resina composta bulk fill inserida em três (BF3) ou único incremento (BF1). O preparo das cavidades foi padronizado para todos os grupos. As amostras foram restauradas e submetidas ao testes de resistência à fadiga com uma frequência de 5 Hz. Foram aplicados 5.000 ciclos de carregamento senoidal inicial com valor de força mínima igual a 50 N e força máxima de 200 N. Após, foram aplicados estágios de 30.000 ciclos de carga com a força máxima sendo aumentada gradativamente a cada estágio, para 400, 600, 800, 1000, 1200 e 1400 N. O ensaio foi finalizado ao ser alcançado 185.000 ciclos de carga (número máximo de ciclos de carga), ou na fratura da amostra. A resistência à fadiga foi registrada para comparação usando a curva de sobrevivência de Kaplan-Meier e analisada pelo teste log-rank a um nível de significância de 0.05. As fraturas foram classificadas conforme a posição da falha - acima ou abaixo da junção cemento esmalte (JCE). A análise estatística da curva de sobrevivência de Kaplan-Meier pelo teste log-rank demonstrou diferença significativa entre os grupos (p=0.001). Na análise de fratura somente 28.58% das falhas foram abaixo da JCE para o grupo C, enquanto para os grupos I, BF1 e BF3 foram 42.85%, 85.71% e 85.71%, respectivamente. Os dentes restaurados com a resina composta bulk fill em ambas as técnicas de inserção apresentaram valores de resistência à fadiga similares àqueles dos dentes restaurados com a resina composta convencional pela técnica incremental. Entretanto, dentes hígidos mostraram uma menor porcentagem de fraturas abaixo da JCE e maior resistência à fadiga.

Biomechanical performance of Bio Cross-Pin and EndoButton for ACL reconstruction at femoral side: a porcine model

Abstract Introduction The method of graft fixation is critical in anterior cruciate ligament (ACL) reconstruction surgery. Success of surgery is totally dependent on the ability of the implant to secure the graft inside the bone tunnel until complete graft integration. The principle of EndoButton is based on the cortical suspension of the graft. The Cross-Pin is based on graft expansion. The aim of this study was to evaluate the biomechanical performance of EndoButton and Bio Cross-Pin to fix the hamstring graft at femoral side of porcine knee joints and evaluate whether they are able to support of loading applied on graft during immediate post-operative tasks. Methods Fourteen ACL reconstructions were carried out in porcine femurs fixing superficial flexor tendons with Titanium EndoButton (n = 7) and with 6 × 50 mm HA/PLLA Bio Cross-Pin (n = 7). A cyclic loading test was applied with 50-250 N of tensile force at 1 Hz for 1000 cycles. The displacement was measured at 20, 100, 500 and 1000 load cycles to quantify the slippage of the graft during the test. Single-cycle load-to-failure test was performed at 50 N/mm to measure fixation strength. Results The laxity during cyclic loading and the displacement to failure during single-cycle test were lower for the Bio Cross-Pin fixation (8.21 ± 1.72 mm) than the EndoButton (11.20 ± 2.00 mm). The Bio Cross-Pin (112.22 ± 21.20 N.mm–1) was significantly stiffer than the EndoButton fixation (60.50 ±10.38 N.mm–1). There was no significant difference between Bio Cross-Pin (failure loading: 758.29 ± 188.05 N; yield loading: 713.67 ± 192.56 N) and EndoButton strength (failure loading: 672.52 ± 66.56 N; yield loading: 599.91 ± 59.64 N). Both are able to support the immediate post-operative loading applied (445 N). Conclusion The results obtained in this experiment indicate that the Bio Cross-Pin technique promote stiffer fixation during cyclic loading as compared with EndoButton. Both techniques are able to support the immediate post-operative loading applied.