Understanding the Relationship between Vaccine Supply Dead Space and Wasted COVID-19 Vaccine Doses

ABSTRACT Introduction: By July 2023, Brazil had administered approximately 540 million COVID-19 vaccine doses. This study aimed to quantify wasted doses resulting from dead space in vaccine supplies. Methods: The vaccine supply was initially weighed, filled with distilled water, and expelled to simulate administration. Weighing it again after the application determined the dead space volume. Descriptive analyses calculated the waste rate/wasted dose count. Results: The estimated total number of wasted vaccine doses using supplies with the lowest dead space was 62,097,338. Conclusions: Syringe dead space is a crucial factor in dose wastage, directly influencing the number of wasted doses.

Improving adhesion between luting cement and zirconia-based ceramic with an alternative surface treatment

This study evaluated the influence of an alternative surface treatment on the microshear bond strength (μsbs) of zirconia-based ceramic. Thirty-five zirconia disks were assigned to five groups according to the following treatments: Control (CO), glass and silane were not applied to the zirconia surface; G1, air blasted with 100μm glass beads + glaze + silane; G2, a gel containing 15% (by weight) glass beads applied to the ceramic surface + glaze + silane; G3, a gel containing 25% (by weight) glass beads applied to the ceramic surface + glaze + silane; and G4, a gel containing 50% (by weight) glass beads applied to the ceramic surface + glaze + silane. The specimens were built up using RelyX ARC®, according to the manufacturer’s recommendations, and inserted in an elastomeric mold with an inner diameter of 0.8 mm. The μsbs test was performed using a testing machine at a crosshead speed of 0.5 mm/min. ANOVA and Tukey’s test (p < 0.05) were applied to the bond strength values (in MPa). CO (15.6 ± 4.1) showed the lowest μsbs value. There were no statistical differences between the G1 (24.9 ± 7.4), G2 (24.9 ± 2.3), G3 (35.0 ± 10.3) and G4 (35.3 ± 6.0) experimental groups. Those groups submitted to surface treatments with higher concentrations of glass showed a lower frequency of adhesive failures. In conclusion, the glass application improved the interaction between the ceramic and the luting cement.

Analysis of stress induced by screws in the vertebral fixation system

Objective: To compare, using photoelasticity, internal stress produced by USS II type screw with 5.2 and 6.2 mm external diameters, when submitted to three different pullout strengths. Methods: Two photoelastic models were especially made. The simulation was performed using loads of 1.8, 2.4 e 3.3 kgf.The fringe orders were evaluated around the screws. In all the models analyzed the shear stress were calculated. Results: Independently of the applied load, the smaller screw showed higher values of shear stress. Conclusion: According to the analysis performed, we observed that the place of highest stress was in the first thread of the lead, close to the head of the screws. Experimental study. .

Análise fotoelástica da região inferior do corpo vertebral L4 / Photoelastic analisys in the lower region of vertebral body L4

OBJETIVO: Analisar as tensões geradas no corpo vertebral L4 quando submetida à força de compressão, utilizando a técnica da fotoelasticidade de transmissão. MÉTODOS: Doze modelos fotoelásticos foram utilizados e divididos em três grupos, sendo cada grupo formado por quatro modelos, de acordo com a localização do corte sagital nas vértebras L4-L5 (cortes A, B e C). A simulação foi realizada utilizando uma força compressão de 15 N e as ordens de franjas foram avaliadas no corpo vertebral L4 utilizando o método de compensação de Tardy. RESULTADOS: A análise fotoelástica mostrou que em geral, as tensões se distribuíram de forma homogênea nos corpos vertebrais. As tensões no corte C foram maiores que no B, que por sua vez foram maiores que no corte A. CONCLUSÃO: A região posterior do corpo vertebral L4, principalmente no corte C, apresentou maiores concentrações de tensões, sendo assim, é a área mais susceptível à fratura vertebral e à espondilolistese. Análises econômicas e de decisão. Desenvolvimento de modelo econômico ou de decisão, Nível de evidência I.

OBJECTIVE: to analyze the shear forces on the vertebral body L4 when submitted to a compression force by means of transmission photoelasticity. METHODS: Twelve photoelastic models were divided into three groups, with four models per group, according to the positioning of the sagittal section vertebrae L4-L5 (sections A, B and C). The simulation was performed using a 15N compression force, and the fringe orders were evaluated in the vertebral body L4 by the Tardy compensation method. RESULTS: Photoelastic analysis showed, in general, a homogeneous distribution in the vertebral bodies. The shear forces were higher in section C than B, and higher in B than A. CONCLUSION: The posterior area of L4, mainly in section C, showed higher shear concentrations, corresponding to a more susceptible area for bone fracture and spondylolisthesis. Economic and Decision Analyses - Development of an Economic or Decision Model. Level I.

Influence of ceramic primers on microshear bond strength between resin cements and zirconia-based ceramic

This study evaluated the effect of a coupling agent ceramic primer (CP) on the microshear bond strength (ìsbs) between luting cements and zirconia-based ceramic. Methods: Zirconia discs (Cercon) were made and finished with silicon carbide paper and submitted to air abrasion using 50 μm aluminum oxide particles (Al2O3) under 4 bar pressure. Zirconia disks were randomly assigned to four groups (n=10): (G1) ResiCem luting cement + Porcelain Primer, (G2) ResiCemluting cement only, (G3) Clearfil Esthetic Cement + Clearfil Ceramic Primer and (G4) Clearfil Esthetic Cement only. The luting cements were prepared according to manufacturers’ recommendations and inserted in an elastomeric mold positioned onto a zirconia disc. Each specimen was photoactivated by 20 s. The specimens were stored at 100% relative humidity and 37ºC for 24 h. The ìsbs test was performed using universal testing machine at a crosshead speed of 0.5 mm/min. An optical microscope was used to analyze the failure modes and illustrative images were captured with a scanning electron microscope. The ìsbs data were analyzed by two-way ANOVA (p<0.05). Results: No significant difference was found among the four groups G1 (17.4±6.8), G2 (17.1±5.5), G3 (15.6±5.5) and G4 (14.2±3.5), all of which showed 100% of adhesive failures. Conclusions: CP showed no increase in the ìsbs between zirconia-based ceramic and resin luting cements.

Comportamento mecânico do terço proximal de fêmures de ratos após período de suspensão pela cauda e exercitação / Mechanical behavior of rats' femoral proximal thirds after a period of tail suspension and exercises

A remodelação óssea pode ser estimulada por forças mecânicas presentes nas atividades físicas normais. Neste trabalho foi analisado o comportamento mecânico do terço proximal de fêmur de ratas submetidas à suspensão pela cauda e posterior treinamento em esteira. Sessenta e seis ratas da raça Wistar foram usadas. Primeiramente os animais foram criados por noventa dias e divididos em cinco grupos (dois controles e três experimentais). Os animais do grupo Controle I foram sacrificados com 118 dias de idade. No grupo S (suspenso) os animais foram suspensos pela cauda por 28 dias e sacrificados. No grupo Controle II os animais foram sacrificados com 139 dias de idade. No grupo S-L (suspenso-liberado) as ratas foram liberadas 21 dias após a suspensão. No grupo S-T (suspenso-treinado) após o período de suspensão os animais passaram por treinamento em esteira durante 21 dias. Para análise do comportamento mecânico do osso foi aplicada uma força vertical na cabeça femoral até a ruptura. A fratura foi analisada por raios-X. A suspensão causou um decréscimo da força máxima e, o treinamento e a liberação após a suspensão causaram a recuperação das propriedades mecânicas. Mas, o padrão de fratura não apresentou diferença entre os grupos experimentais.

Bone remodeling can be stimulated by mechanical forces present in normal physical activities. In the present research, we investigated the mechanical behavior of the proximal femur of rats previously maintained in tail suspension and later, submitted to physical exercise on a treadmill. Sixty-six Wistar rats were used. Firstly, the animals were raised until the age of ninety days and then divided into five groups (two control groups and three experimental groups). The animals allocated to Control I group were killed at 118 days of age. In the S group, the animals were suspended by tail for 28 days. In Control II group, the animals were killed at 139 days of age. In group S-L (suspended and released) the rats were kept free for 21 days after tail suspension. In group S-T (suspended and trained), after tail suspension period, the rats were trained in a treadmill for 21 days. For analysis of the mechanical behavior of the bone, force was applied on the femoral head until failure. The fracture was evaluated by x-ray. Suspension caused a decrease of the maximum load and, treadmill training and post-suspension release caused the recovery of mechanical properties. But, the fracture line pattern did not show any difference among the experimental groups.