Tecnologia digital em próteses totais: propriedades dos materiais CAD-CAM e desenvolvimento de uma patente de inovação para simplificação do fluxo de trabalho / Digital technology in complete dentures: properties of CAD-CAM materials and development of an innovation patent to simplify the workflow

Recursos digitais, como a manufatura subtrativa (fresagem CAD-CAM) e a manufatura aditiva (impressão 3D) podem promover significativos avanços, reduzindo o tempo e o custo de produção de próteses totais (PTs). Assim, este estudo objetiva investigar as características superficiais (rugosidade e ângulo de contato), propriedades mecânicas (resistência mini-flexural) e a adesão de biofilme sobre polímeros de PMMA pré-polimerizado para fresagem CAD-CAM e sobre resinas para impressão 3D utilizados na fabricação de bases de PTs, bem como propor um fluxo de trabalho inovador para abreviar e simplificar as etapas de confecção de PTs. Para a análise in vitro, foram fabricados um total de 60 discos e 40 barras distribuídas igualmente em quatro grupos: fresagem CAD-CAM (GF), impressão 3D (GI) e PMMA convencional termopolimerizado por ciclo longo (GCL) ou por energia de micro-ondas (GCM). A rugosidade foi determinada pelo valor de Ra; o ângulo de contato foi medido pelo método da gota séssil; o teste de resistência à mini-flexão foi obtido por teste de flexão de três pontos, enquanto o comportamento frente à formação de biofilme foi analisado através da adesão de biofilme de C. albicans. Os dados foram analisados por meio de estatística descritiva e analítica (α = 0,05). Os resultados mostraram que o GI apresentou a maior rugosidade superficial (Ra: 0,317 ± 0,151µm) e os menores valores de resistência à miniflexão (57,23 ± 9,07MPa) e o GF apresentou a menor adesão de biofilme de C. albicans (log UFC/mL: 3,74 ± 0,57) e maior média de resistência à mini-flexão (114,96 ± 16,23 MPa). Não houve diferença estatística entre o GF e os grupos convencionais para rugosidade, ângulo de contato e resistência à mini-flexão. A patente de inovação desenvolvida estabeleceu um novo fluxo de trabalho para confecção de próteses totais através de um protocolo de três consultas em que foram feitas as moldagens anatômicas na 1ª sessão, juntamente com o registro do suporte labial, plano oclusal e linhas de referência para subsidiar a montagem dos dentes superiores. Uma prótese-teste foi confeccionada por meio de procedimentos convencionais ou CAD-CAM e avaliada na 2ª consulta, permitindo observar o resultado estético, executar a moldagem funcional e realizar o registro da relação maxilo-mandibular, fornecendo referências precisas para a confecção da prótese inferior. Com base nos resultados da fase in vitro deste estudo, os corpos-de-prova obtidos a partir de disco para fresagem CAD-CAM apresentaram resistência flexural e propriedades superficiais semelhantes às resinas convencionais e mostraram um comportamento inibidor da adesão de C. albicans, enquanto os espécimes produzidos por impressão 3D exibiram a menor resistência à flexão e a maior rugosidade da superfície. O dispositivo inovador apresentado para a execução das etapas clínicas relacionadas à fabricação de PTs mostrou-se efetivo para abreviar e simplificar as técnicas disponíveis, apresentando confiabilidade e previsibilidade para produção de PTs em número de sessões reduzido (AU).

Digital features like subtractive and additive manufacturing can promote breakthroughs by reducing the time and cost of making complete dentures (CDs). Thus, this study aims to investigate surface characteristics (roughness and contact angle), mechanical properties (mini-flexural strength), and biofilm adhesion on computer-aided design/computer-aided manufacturing (CAD-CAM) PMMA polymer, and threedimensional (3D) printed resin for denture´s base fabrication as well as to propose an innovative workflow. For in vitro analysis, a total of 60 discs and 40 rectangular specimens were fabricated from one CAD-CAM pre-polymerized PMMA disc (GF), one 3D-printed (GI), and two conventional heat-polymerized (GCL and GCM) materials for denture base fabrication. Roughness was determined by the Ra value; the contact angle was measured by the sessile drop method; the mini-flexural strength test was a three-point bending test while the biofilm formation inhibition behavior was analyzed through C. albicans adhesion. The data were analyzed using descriptive and analytical statistics (α = 0.05). Results showed that GI specimens presented the highest surface roughness (Ra: 0.317 ± 0.151 µm) and lowest mini-flexural strength values (57.23 ± 9.07 MPa) and the GF showed the lowest C. albicans adhesion (log CFU/mL: 3.74 ± 0.57) and highest mini-flexural strength mean (114.96 ± 16.23 MPa). There was no statistical difference between GF and conventional groups for roughness, contact angle, and mini-flexural strength. In turn, the presented novel workflow for complete dentures fabrication reached a three appointments protocol in which preliminary impressions were made in the 1st session, all together to maxillary registration of lip support, occlusal plane, and reference lines for teeth arrangement. A trial denture was manufactured and evaluated by the 2nd appointment through conventional or CAD-CAM procedures, allowing esthetics evaluation, final impression, and maxillomandibular relationship record and providing precise references for final dentures fabrication. Based on the findings of this in vitro study, GF presented surface and mechanical properties similar to conventional resins and show improved behavior preventing C. albicans adhesion, while GI specimens exhibited the lowest flexural strength, and highest surface roughness. The proposed device for CD´s fabrication clinical procedures reached feasibility and by simplifying available techniques, this protocol could achieve reliability and predictability to produce complete dentures with reduced working time (AU).

Pandemic effects to autonomous vehicles test operations in California.

Companies developing automated driving system (ADS) technologies have spent heavily in recent years to conduct live testing of autonomous vehicles operating in real world environments to ensure their reliable and safe operations. However, the unexpected onset and ongoing resurgent effects of the Covid-19 pandemic starting in March 2020 has serve to halt, change, or delay the achievement of these new product development test objectives. This study draws on data obtained from the California automated vehicle test program to determine the extent that testing trends, test resumptions, and test environments have been affected by the pandemic. The importance of government policies to support and enable autonomous vehicles development during pandemic conditions is highlighted.

Biomechanical duality of fracture healing captured using virtual mechanical testing and validated in ovine bones.

Bone fractures commonly repair by forming a bridging structure called callus, which begins as soft tissue and gradually ossifies to restore rigidity to the bone. Virtual mechanical testing is a promising technique for image-based assessment of structural bone healing in both preclinical and clinical settings, but its accuracy depends on the validity of the material model used to assign tissue mechanical properties. The goal of this study was to develop a constitutive model for callus that captures the heterogeneity and biomechanical duality of the callus, which contains both soft tissue and woven bone. To achieve this, a large-scale optimization analysis was performed on 2363 variations of 3D finite element models derived from computed tomography (CT) scans of 33 osteotomized sheep under normal and delayed healing conditions. A piecewise material model was identified that produced high absolute agreement between virtual and physical tests by differentiating between soft and hard callus based on radiodensity. The results showed that the structural integrity of a healing long bone is conferred by an internal architecture of mineralized hard callus that is supported by interstitial soft tissue. These findings suggest that with appropriate material modeling, virtual mechanical testing is a reliable surrogate for physical biomechanical testing.

Desenvolvimento e avaliação do uso de um objeto virtual de aprendizagem com simulação virtual sobre alginato / Development and evaluation of the use of a virtual learning object with virtual simulation on alginate

O objetivo do presente estudo foi desenvolver um Objeto Virtual de Aprendizagem (OVA) sobre materiais de moldagem, com ênfase no alginato, e avaliar a influência do seu uso sobre o aprendizado teórico e habilidade clínica de estudantes de Odontologia, assim como sobre as propriedades física e mecânica material. Sessenta e quatro estudantes receberam aula teórica expositiva sobre alginato e posteriormente foram divididos em 2 grupos, Controle (n=30) e OVA (n=34). O grupo OVA teve acesso à ferramenta educacional composta de conteúdo teórico e simulação de espatulação do alginato, sendo sua habilidade avaliada. Todos os participantesrealizaram um pré-teste após a aula teórica, assim como testes de habilidade de manipulação do material,o qualfoi submetido a ensaio de resistência à compressão e reprodução de detalhes. Uma avaliação pós-teste foi realizada após quinze dias. Os resultados dos grupos foram comparados pelo teste t, modelo de regressão logística e as variáveis significativas foram incluídas no modelo de regressão múltipla. Todas as análises foram conduzidas com significância de 5%. Na simulação do OVA 75% dos usuários obtiveram nota máxima e os resultados das avaliações teóricas não indicaram diferença estatística entre os grupos. O uso do OVA está relacionado à maior habilidade clínica, com 3,76 mais chances de correta incorporação do pó. No ensaio de resistência à compressão a média dos grupos foi superior ao preconizado pela norma, OVA 0,86±0,03 e Controle 1,09±0,04. A ferramenta desenvolvida exerce influência positiva sobre a habilidade clínica e propriedade mecânica do material estudado, constituindo-se como promissora estratégia de aprendizagem virtual (AU).

The aim of the present study was to develop a Virtual Learning Object (VLO) on impression materials, with emphasis on alginate, and to evaluate the influence of its use on the theoretical learning and clinical skills of dental students, as well as on the physical properties and material mechanics. Sixty-four students received a theoretical lecture on alginate and were later divided into 2 groups, Control (n=30) and VLO (n=34). The VLO group had access to the educational tool composed of theoretical content and simulation of alginate mixing, and their ability was evaluated. All participants performed a pre-test after the theoretical class, as well as tests of ability to handle the material, which was subjected to a compressive strength test and detailreproduction. A post-test evaluation was performed after fifteen days. The results of the groups were compared by the t test, logistic regression model and significant variables were included in the multiple regression model. All analyzes were conducted with a significance of 5%. In the VLO simulation, 75% of the users obtained the maximum score and the results of the theoretical assessments did not indicate a statistical difference between the groups. The use of VLO is related to greater clinical skill, with 3.76 more chances of correct incorporation of the powder. In the compressive strength test, the mean of the groups was higher than that recommended by the standard, VLO 0.86±0.03 and Control 1.09±0.04. The developed tool has a positive influence on theclinical ability and mechanical property of the material studied, constituting itself as a promising strategy of virtual learning (AU).

A material stress test study on occurrence of leakage and material failure of peritoneal dialysis (PD) catheters.

Peritonitis is a common complication of peritoneal dialysis (PD). Our root cause analysis allowed to attribute some cases to leakage of the PD catheter. Accordingly, a clinically based stress test study on potential material damage issues of PD catheters was performed, focusing on material damage caused by cleaning, de- and attachment procedures during dialysate changes and on the individual storage methods of PD catheters between dialysate changes. PD catheters were exposed to both chemical stress by repeating dialysate-flow and physical stress simulating de- and connecting, fixation, pressure, flexing, folding etc.-simulating standard clinical daily routine of 8-10 years PD catheter usage. Potentially by normal usage caused damages should be then detected by intraluminal pressure, light- and electron microscopy. The multi-step visual control showed no obvious damages on PD catheters nor any leakage or barrier indulgence. Our tests simulating daily routine usage of PD catheters for several years could not detect any material defects under chemical or physical stress. Hence, we presume that most PD catheter damages, as identified cause for peritonitis in some of our patients, may be due to accidental, unnoticed external damage (e.g. through scissors, while changing dressings) or neglecting PD catheter handling specifications.

Decreased Injury Rate Following Mandated Headgear Use in Women's Lacrosse.

INTRODUCTION: There has been controversy regarding whether headgear use in women's lacrosse will affect the rate of head and musculoskeletal injuries. The purpose of this study was to investigate the effect of mandated headgear use on the rate of head and musculoskeletal injuries in high school women's lacrosse. METHODS: This was a prospective cohort study of eight high school women's lacrosse teams and their game op-ponents who were mandated to wear F3137 headgear for the 2017 and 2018 seasons. Athletic trainers documented all injuries that occurred as a result of participation on the lacrosse teams. Injury rates in the headgear cohort were compared to a retrospective (control) cohort from the High School Reporting Information Online injury data reports. RESULTS: Over the study period, 17 total injuries were reported in the headgear cohort during 22,397 exposures for an injury rate of 0.76 injuries per 1,000 athlete-exposures. The headgear cohort demonstrated significant decreases in rates of in-game head and face injury (RR 0.141, 95% CI [0.004, 0.798]), in-game concussion (RR 0.152, 95% CI [0.004, 0.860]), and practice trunk and extremity injury (RR 0.239, 95% CI [0.049, 0.703]) when compared to the control cohort. CONCLUSION: Mandated use of headgear was shown to be effective at lowering the rate of head or face injury and concussions in women's lacrosse. Additionally, mandated headgear use was also shown to lower the rate of injury to body locations other than the head or face during practice. To our knowledge, this is the first study to demonstrate a decrease in injury rates associated with ASTM approved headgear in women's lacrosse.

A new proximal femoral nail antirotation design: Is it effective in preventing varus collapse and cut-out?

OBJECTIVES: This study aims to compare the mechanical features of the existing proximal femoral nail antirotation (PFNA) system and the new PFNA system that we designed using three-dimensional (3D) finite element analysis. MATERIALS AND METHODS: This experimental study was conducted between 2019 and 2020. We constructed two femur models with Arbeitsgemeinschaft für Osteosynthesefragen (AO) type A1 fractures using 3D computed tomography scans. The new and standard PFNA designs were inserted into the femur models and subsequently transferred to the program. We investigated the distribution of stress on the tip of the lag screw, the calcar region, lag screw-nail junction, and the additional screw inserted through the greater trochanter (only present in the new PFNA design) using 3D finite element analysis. RESULTS: When the von Mises stress distributions in our models were examined, the maximum stress at the lag screw-nail junction was 18 mpa in the new design PFNA, while it was 20 mpa in the classic PFNA model. The maximum stress at the junction of the additional screw that had greater trochanter inlet with the nail was found as 42.5 mpa. The maximum stress on the calcar region was found to be 10 mpa at the new design PFNA, while it was 13 mpa with 30% increase in the classic PFNA. The stress on the tip of the lag screw was found to be 49 mpa in the classic PFNA design, while in the new design PFNA it was found as 28 mpa with a decrease of more than 40%. CONCLUSION: As per our findings, the new PFNA design leads to reduced stress on the lag screw-nail junction, the calcar region, and the tip of the lag screw.

High mechanical strength gelatin composite hydrogels reinforced by cellulose nanofibrils with unique beads-on-a-string morphology.

This work prepared high mechanical strength gelatin composite hydrogels reinforced by cellulose nanofibrils with unique beads-on-a-string morphology. In detail, cellulose nanofibrils (H-Cel) with unique beads-on-a-string morphology were obtained by acid hydrolysis followed by intensive sonication. The D-H-Cel nanofibrils were prepared through oxidizing part of the non-esterified hydroxyl groups on the H-Cel into aldehyde groups. D-H-Cel were then mixed with gelatin and D-H-Cel/Gel composite hydrogels were produced. During the mixing, a giant network structure was constructed through the Schiff-base reaction between the aldehyde groups on the surface of D-H-Cel nanofibrils and the primary amino groups on gelatin macromolecular chains. Since the cellulose nanofibrils were covalently bonded to gelatin, the stress could be efficiently transferred between the reinforcing agent and matrix, resulting in a composite hydrogel with drastically increased mechanical strength. The compressive strength of D-40H-Cel/Gel hydrogel reached 3.398 MPa. SEM images showed a highly porous three-dimensional structure in the hydrogel with regulated pore size. The crosslinking indices were measured with ninhydrin assay. The composite hydrogels could maintain their shape well in buffer solution. The present work shows that natural polymer-based composite hydrogels with extremely high mechanical strength could be obtained by reinforcing with surface modified cellulose nanofibrils with unique beads-on-a-string morphology.

An evaluation of dermal microcirculatory occlusion under repeated mechanical loads: Implication of lymphatic impairment in pressure ulcers.

OBJECTIVE: Pressure ulcers are caused by prolonged mechanical loads deforming the underlying soft tissues. However, the mechanical loads for microcirculatory occlusion are unknown. The present study was designed to characterize the simultaneous response of microvascular and lymphatic structures under repeated mechanical loading. METHODS: The effects of two distinct loading/unloading cycles involving (a) incremental pressures 30, 60, and 90 mmHg and (b) three repeated cycles of 30 mmHg were evaluated on a cohort of able-bodied volunteers. Microvascular response involved the monitoring of transcutaneous gas tensions, while dermal lymphatic activity was estimated from near-infrared imaging. Responses were compared during each load and recovery cycle. RESULTS: Changes in microvascular response were dependent on the load magnitudes, with 30 mmHg resulting in a reduction in oxygen tension only, while 90 mmHg affected both oxygen and carbon dioxide values in most cases (54%). By contrast, lymphatics revealed near total occlusion at 30 mmHg. Although there were intersubject differences, temporal trends consistently revealed partial or full impairment under load, with recovery during off-loading. CONCLUSIONS: The pressure required to cause microcirculatory occlusion differed between individuals, with lymphatic impairment occurring at a lower pressure to that of microvascular vessels. This highlights the need for personalized care strategies and regular off-loading of vulnerable tissues.

Realization of Rapid Large-Size 3D Printing Based on Full-Color Powder-Based 3DP Technique.

The powder-based 3DP (3D printing) technique has developed rapidly in creative and customized industries on account of it's uniqueness, such as low energy consumption, cheap consumables, and non-existent exhaust emissions. Moreover, it could actualize full-color 3D printing. However, the printing time and size are both in need of upgrade using ready printers, especially for large-size 3D printing objects. Given the above issues, the effects of height and monolayer area on printing time were explored and the quantitative relationship was given in this paper conducted on the specimens with a certain gradient. On this basis, an XYX rotation method was proposed to minimize the printing time. The mechanical tests were conducted with three impregnation types as well as seven printing angles and combined with the characterization of surface structure based on the scanning electron microscope (SEM) digital images to explore the optimum parameters of cutting-bonding frame (CBF) applied to powder-based 3D printing. Then, four adhesives were compared in terms of the width of bonded gap and chromatic aberration. The results revealed that ColorBond impregnated specimens showed excellent mechanical properties which reached maximum when printed at 45° to Z axis, and α-cyanoacrylate is the most suitable adhesive to bond full-color powder-based models. Finally, an operation technological process was summarized to realize the rapid manufacturing of large-size full-color 3D printed objects.

A Helmholtz resonator on elastic foundation for measurement of the elastic coefficient of human skin.

A new sensing mechanism is proposed for the measurement of elasticity of human skin by utilizing Helmholtz resonator with a flexible membrane mounted at the bottom and putting on an elastic foundation. Elastic coefficient of human skin is modeled as the elastic foundation modulus, based on the assumption that human skin is equivalent to the Winkler foundation. For the Helmholtz resonator, the acoustic transmission loss (by which resonant frequency can be acquired) was derived by using the receptance coupling method, based on the theories of conventional Helmholtz resonator and fixed-edge membrane on elastic foundation. The fundamental resonant frequency of the proposed Helmholtz resonator was proved to be related with the elastic foundation modulus, and was used as the indicator of elastic foundation modulus to be measured. Theoretical derivation for measuring elastic foundation modulus and analytical example were presented. Experiments measuring the elastic foundation modulus of the phantoms were carried out by utilizing phantoms with different stiffness using gelatin with corresponding different concentrations. The analytical and experimental results verified the effectiveness of the proposed method. Nanoindentation test was conducted for comparison, and relative errors ranged from 9.24% to 20.06% were obtained, which tends to be higher with the increasing concentration of gelatin.

Nondestructive Assessment of Articular Cartilage Electromechanical Properties after Osteochondral Autologous and Allogeneic Transplantation in a Goat Model.

OBJECTIVE: To determine the applicability of a minimally invasive diagnostic device to evaluate the quality of articular cartilage following autologous (OAT) and allogeneic (OCA) osteochondral graft transplantation in goat model. DESIGN: OAT grafts were harvested from lateral femoral condyles (LFCs) and transplanted into osteochondral defects created in medial femoral condyles (MFCs) of contralateral knees. OCA grafts were transplanted into MFC condyles after in vitro storage. Autologous platelet-rich plasma (PRP) was administered intraarticularly after the surgery and at 1 and 2 months postoperatively. OAT and OCA grafts were evaluated macroscopically (Oswestry arthroscopy score [OAS]), electromechanically (quantitative parameter, QP), and histologically (O'Driscoll score, safranin O staining intensity) at 3 and 6 months after transplantation. Results were compared with preoperative graft evaluation. RESULTS: Transplanted cartilage deteriorated within 6 months in all groups. Cartilage quality was better retained in OAT group compared with a decline in OCA group. QP and OAS scores were comparable in OAT and OCA groups at 3 months, but superior in OAT group at 6 months, according to all the methods applied. PRP injections significantly improved QP and OAS score at 6 months compared with 3 months in OAT group. QP moderately correlated with OAS, O'Driscoll score, and safranin O staining intensity. CONCLUSIONS: Grafts did not retain preoperative quality parameters at 6 months follow-up; however, OAT were superior to OCA grafts. PRP may have a beneficial effect on macroscopic and electromechanical properties of cartilage; however, histological improvement is yet to be proved. Electromechanical diagnostic device enables reliable assessment of transplanted cartilage.

Determination of the Depth- and Time- Dependent Mechanical Behavior of Mouse Articular Cartilage Using Cyclic Reference Point Indentation.

Mouse models of osteoarthritis and cartilage degeneration are important and powerful tools for investigating the molecular mechanisms of the disease pathology. Because of the vast number of genetically modified mouse models that are available for research, the ability to use these models is particularly attractive for the mechanobiologic interactions in the pathogenesis of osteoarthritis. However, the very small scale of mouse articular cartilage, where the healthy tissue is only 80 µm in thickness, poses challenges in quantifying mechanical characteristics of the tissue. We introduce here a novel approach that combines experimental and analytical methods to quantify the nuanced mechanical changes during cartilage degeneration at this scale. Cyclic reference point indentation is used to directly test the murine articular cartilage to obtain the force-deformation and the phase-shift characteristics of the tissue. The cartilage zonal thicknesses are confirmed from histology. These data are then fitted to a parallel spring model to determine the depth-dependent tissue stiffness and modulus. Using this approach, we investigated the effects of trypsin degradation on the zonal mechanical behavior of mouse articular cartilage. We observe a decline of the superficial zone stiffness coupled with the loss of the superficial layer. Subsequent degradation by trypsin allowed the identification of middle- and deep- zone properties. Taken together, this approach can be a useful tool for understanding the disease mechanisms of cartilage homeostasis and degeneration, and for monitoring of therapies for osteoarthritis.

Características mecânicas e ópticas de resinas bulk-fill: revisão de literatura / Mechanical and optics characteristics of bulk-fill resins: literature review

Objetivo: realizar uma análise descritiva das característicasmecânicas e ópticas das resinas bulk-fill com baseem dados da literatura. Revisão da literatura: para arealização do estudo, foram utilizados artigos extraídosdas bases de dados PubMed, SciELO e Lilacs. As palavras-chave utilizadas para busca foram: resina bulk-fill,resina composta, polimerização, grau de conversão,caracterização, dureza, rugosidade, resistência à flexão,translucidez, propriedades ópticas. Os compostosbulk-fill são basicamente formados por matriz orgânicae partículas de alumínio, silício e bário, medindo de0,1 µm a 1 µm. Tratam-se de resinas translúcidas quepodem ser polimerizadas adequadamente em camadasespessas, possuem propriedades mecânicas aceitáveis,porém inferiores às resinas nano e micro-híbridas, e têmbaixo grau de contração volumétrica e menor tensão decontração do que as resinas compostas convencionais.Considerações finais: as resinas bulk-fill são indicadaspara restauração de cavidades com fator de contraçãocavitário desfavorável. A cobertura dessas resinas com2 mm de resina composta convencional em área oclusalé recomendável. (AU)

Objective: the objective of this work was, based on literature data, to describe mechanical and optical characteristics of bulk-fill resins. Literature review: articles were selected at PubMed, SciELO and Lilacs. Search was performed using the keywords: bulk-fill resin, composite resin, polymerization, degree of conversion, characterization, hardness, roughness, flexural strength, translucency, optical properties. Bulk-fill composites are basically formed by organic matrix and particles of aluminium, silicon and barium, measuring from 0.1 µm to 1 µm. They are translucent resins that can be polymerized in thick layers, with acceptable mechanical properties, but with inferior performance than nano and microhybrid resins. The material presents volumetric lower shrinkage and residual stresses than conventional composite resins. Final considerations: bulk-fill resins are indicated for the restoration of cavities with an unfavorable contraction factor. A 2 mm-thick layer of conventional composite resin at the occlusal area over the bulk-fill resins is recommended. (AU)