In vitro comparison of peracetic acid and autoclave sterilization in the corrosion of orthodontic pliers: a pilot study

ABSTRACT Introduction: The most currently recommended method for sterilization of orthodontic pliers is the autoclave, while peracetic acid has also been shown to be effective in the chemical sterilization process. Objective: This study sought to compare the corrosive effects of peracetic acid and autoclave sterilization process of orthodontic pliers. Methods: Four active tungsten carbide (WC) stainless steel tie-cutting pliers from the manufacturers Quinelato (Rio Claro, SP, Brazil) and ICE (Cajamar, SP, Brazil) were selected. The active ends of the pliers were sectioned, and six active tips were obtained and distributed into the following groups: 1) control group (no sterilization); 2) AC group (two active pliers tips submitted to 100 autoclave sterilization cycles); and 3) AP group (two active pliers tips submitted to 100 cycles of sterilization by immersion in 2% peracetic acid solution for 30 minutes). Results: Chemical analysis using X-ray dispersive energy spectroscopy showed that after autoclave sterilization, only the ICE pliers presented oxidation corrosion (Δ[O] = +24.5%; Δ[Fe] = +5.8%; Δ[WC] = -1.9%). In comparison, following peracetic acid sterilization, both manufacturers ICE (Δ[O] = +1.8%; Δ[Fe] = +18.0%; Δ[WC] = -1.1%) and Quinelato (Δ[O] = +5.3%; Δ[Fe] = -10.4%; Δ[WC] = -15.2%) showed corrosion. The morphological analysis revealed that peracetic acid caused a pitting and localized corrosion in both brands, while the autoclave caused uniform surface corrosion on the ICE pliers. Conclusion: Autoclave application was the sterilization method that generated less corrosive damage to the orthodontic cutting pliers, when compared to the immersion in 2% peracetic acid.

RESUMO Introdução: O método mais recomendado para a esterilização dos alicates ortodônticos é a autoclave; porém, o ácido peracético mostrou-se eficaz no processo de esterilização química. Objetivo: O objetivo do presente estudo foi avaliar o efeito corrosivo do ácido peracético e da autoclave no processo de esterilização de alicates ortodônticos. Métodos: Foram selecionados quatro alicates de corte de amarrilho de aço inoxidável, com ponta ativa de carboneto de tungstênio (WC), das marcas Quinelato (Rio Claro/SP, Brasil) e ICE (Cajamar/SP, Brasil), que foram distribuídos em três grupos: 1) Controle (C), o qual não foi submetido à esterilização; 2) Grupo AC, constituído por duas pontas ativas de alicates submetidas a 100 ciclos de esterilização em autoclave; e 3) Grupo AP, formado por duas pontas ativas de alicates submetidas a 100 ciclos de esterilização por imersão em solução de ácido peracético a 2% durante 30 minutos. Resultados: Por meio da análise química (EDS, energia dispersiva de raios X), constatou-se que, após esterilização em autoclave, somente o alicate ICE apresentou corrosão por oxidação (Δ[O] = +24,5%; Δ[Fe] = +5,8% e Δ[WC] = -1,9%), enquanto na esterilização em ácido peracético, ambas as marcas, ICE (Δ[O] = +1,8%; Δ[Fe] = +18,0% e Δ[WC] = -1,1%) e Quinelato (Δ[O] = +5,3%; Δ[Fe] = -10,4% e Δ[WC] = -15,2%), apresentaram corrosão. A análise morfológica demonstrou que o ácido peracético causou uma corrosão localizada em pite em ambas as marcas, enquanto a autoclave ocasionou uma corrosão superficial uniforme no alicate ICE. Conclusão: A autoclave foi o método de esterilização que gerou menor dano corrosivo aos alicates ortodônticos, em comparação à imersão em ácido peracético a 2%.

Influence of metal ions on pellet morphology and polygalacturonase synthesis by Aspergillus niger 3T5B8

The effects of cations addition on pellet morphology and polygalacturonase (PG) synthesis by Aspergillus niger 3T5B8 were studied and compared with a control system. Fe(II), Cu(II), Zn(II) and Mn(II) were added to the fermentation medium separately, and also as combined groups of cations. The addition of Fe2+ and/or Zn2+ ions was significantly positive to the enzyme production. A positive effect in the biomass content, however, was only obtained when the same metal ions were added separately. On the other hand, Cu2+ and Mn2+ ions had almost no effect on these parameters. The morphology of the pellets was studied by image processing techniques. Small pellets with small cores were usually obtained when Fe2+ and Zn2+ ions were individually or collectively added to the medium. The pellets produced in media containing Fe2+ or Zn2+ ions were compact, while the ones produced in a medium containing both cations were considered diffuse. Autolysis of the core was observed for large control pellets, due to the deficient nutrient transfer to the interior of the pellet. The pellets obtained in a medium containing both Fe2+ and Zn2+ ions were high enzyme producers, probably due to a loose morphology, induced by the presence of combined groups of metal ions in the medium, favoring the nutrient transfer.